[kernel] Bring back utrace until uprobes gets merged upstream.
Dave Jones
davej at fedoraproject.org
Fri Jul 15 20:04:51 UTC 2011
commit 5a6744203a9917826cdd7a003e0fbbecc341adfe
Author: Dave Jones <davej at redhat.com>
Date: Fri Jul 15 16:04:21 2011 -0400
Bring back utrace until uprobes gets merged upstream.
config-generic | 2 +
kernel.spec | 8 +
utrace.patch | 6166 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 6176 insertions(+), 0 deletions(-)
---
diff --git a/config-generic b/config-generic
index 755c7c6..e93ccee 100644
--- a/config-generic
+++ b/config-generic
@@ -4220,6 +4220,8 @@ CONFIG_ASYNC_TX_DMA=y
CONFIG_UNUSED_SYMBOLS=y
+CONFIG_UTRACE=y
+
CONFIG_FTRACE=y
CONFIG_DYNAMIC_FTRACE=y
# CONFIG_IRQSOFF_TRACER is not set
diff --git a/kernel.spec b/kernel.spec
index 9248054..fcb9284 100644
--- a/kernel.spec
+++ b/kernel.spec
@@ -696,6 +696,8 @@ Patch12205: runtime_pm_fixups.patch
Patch12303: dmar-disable-when-ricoh-multifunction.patch
+Patch20000: utrace.patch
+
%endif
BuildRoot: %{_tmppath}/kernel-%{KVERREL}-root
@@ -1274,6 +1276,9 @@ ApplyPatch linux-2.6-rt2x00-Add-device-ID-for-RT539F-device.patch
# rhbz#605888
ApplyPatch dmar-disable-when-ricoh-multifunction.patch
+# utrace.
+ApplyPatch utrace.patch
+
# END OF PATCH APPLICATIONS
%endif
@@ -1884,6 +1889,9 @@ fi
# and build.
%changelog
+* Fri Jul 15 2011 Dave Jones <davej at redhat.com>
+- Bring back utrace until uprobes gets merged upstream.
+
* Wed Jul 13 2011 Kyle McMartin <kmcmartin at redhat.com> 3.0-0.rc7.git1.1
- Update to snapshot 3.0-rc7-git1 for intel drm fixes.
diff --git a/utrace.patch b/utrace.patch
new file mode 100644
index 0000000..55d0b3c
--- /dev/null
+++ b/utrace.patch
@@ -0,0 +1,6166 @@
+From davej Thu Jun 30 20:27:03 2011
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+Date: Fri, 1 Jul 2011 02:20:57 +0200
+From: Oleg Nesterov <oleg at redhat.com>
+To: "Frank Ch. Eigler" <fche at redhat.com>, Kyle McMartin <kmcmartin at redhat.com>,
+ Dave Jones <davej at redhat.com>, Josh Stone <jistone at redhat.com>,
+ Matthew Garrett <mjg at redhat.com>, David Smith <dsmith at redhat.com>
+Cc: kernel at lists.fedoraproject.org, utrace-devel at redhat.com
+Subject: [PATCH 01/19] utrace core
+Message-ID: <20110701002057.GA25776 at redhat.com>
+MIME-Version: 1.0
+Content-Type: text/plain; charset=us-ascii
+Content-Disposition: inline
+User-Agent: Mutt/1.5.18 (2008-05-17)
+X-Scanned-By: MIMEDefang 2.68 on 10.5.11.22
+Status: RO
+Content-Length: 148213
+Lines: 4119
+
+From: Roland McGrath <roland at redhat.com>
+
+This adds the utrace facility, a new modular interface in the kernel for
+implementing user thread tracing and debugging. This fits on top of the
+tracehook_* layer, so the new code is well-isolated.
+
+The new interface is in <linux/utrace.h> and the DocBook utrace book
+describes it. It allows for multiple separate tracing engines to work in
+parallel without interfering with each other. Higher-level tracing
+facilities can be implemented as loadable kernel modules using this layer.
+
+The new facility is made optional under CONFIG_UTRACE.
+When this is not enabled, no new code is added.
+It can only be enabled on machines that have all the
+prerequisites and select CONFIG_HAVE_ARCH_TRACEHOOK.
+
+In this initial version, utrace and ptrace do not play together at all,
+the next patches try to fix this.
+
+This is is same/old utrace-core patch except:
+
+ - use group_stop/GROUP_STOP_DEQUEUED instead of removed
+ signal->flags/SIGNAL_STOP_DEQUEUED in utrace_get_signal()
+
+ - rediff the changes in tracehook.h against the current code
+ without PT_PTRACED tweaks which were needed for ptrace-utrace
+
+Signed-off-by: Roland McGrath <roland at redhat.com>
+Signed-off-by: Oleg Nesterov <oleg at redhat.com>
+---
+ Documentation/DocBook/Makefile | 2 +-
+ Documentation/DocBook/utrace.tmpl | 589 +++++++++
+ fs/proc/array.c | 3 +
+ include/linux/sched.h | 5 +
+ include/linux/tracehook.h | 85 ++-
+ include/linux/utrace.h | 692 +++++++++++
+ init/Kconfig | 9 +
+ kernel/Makefile | 1 +
+ kernel/fork.c | 3 +
+ kernel/utrace.c | 2440 +++++++++++++++++++++++++++++++++++++
+ 10 files changed, 3827 insertions(+), 2 deletions(-)
+ create mode 100644 Documentation/DocBook/utrace.tmpl
+ create mode 100644 include/linux/utrace.h
+ create mode 100644 kernel/utrace.c
+
+diff --git a/Documentation/DocBook/Makefile b/Documentation/DocBook/Makefile
+index 3cebfa0..86c288b 100644
+--- a/Documentation/DocBook/Makefile
++++ b/Documentation/DocBook/Makefile
+@@ -14,7 +14,7 @@ DOCBOOKS := z8530book.xml mcabook.xml device-drivers.xml \
+ genericirq.xml s390-drivers.xml uio-howto.xml scsi.xml \
+ 80211.xml debugobjects.xml sh.xml regulator.xml \
+ alsa-driver-api.xml writing-an-alsa-driver.xml \
+- tracepoint.xml media.xml drm.xml
++ tracepoint.xml utrace.xml media.xml drm.xml
+
+ ###
+ # The build process is as follows (targets):
+diff --git a/Documentation/DocBook/utrace.tmpl b/Documentation/DocBook/utrace.tmpl
+new file mode 100644
+index 0000000..0c40add
+--- /dev/null
++++ b/Documentation/DocBook/utrace.tmpl
+@@ -0,0 +1,589 @@
++<?xml version="1.0" encoding="UTF-8"?>
++<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.1.2//EN"
++"http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd" []>
++
++<book id="utrace">
++ <bookinfo>
++ <title>The utrace User Debugging Infrastructure</title>
++ </bookinfo>
++
++ <toc></toc>
++
++ <chapter id="concepts"><title>utrace concepts</title>
++
++ <sect1 id="intro"><title>Introduction</title>
++
++ <para>
++ <application>utrace</application> is infrastructure code for tracing
++ and controlling user threads. This is the foundation for writing
++ tracing engines, which can be loadable kernel modules.
++ </para>
++
++ <para>
++ The basic actors in <application>utrace</application> are the thread
++ and the tracing engine. A tracing engine is some body of code that
++ calls into the <filename><linux/utrace.h></filename>
++ interfaces, represented by a <structname>struct
++ utrace_engine_ops</structname>. (Usually it's a kernel module,
++ though the legacy <function>ptrace</function> support is a tracing
++ engine that is not in a kernel module.) The interface operates on
++ individual threads (<structname>struct task_struct</structname>).
++ If an engine wants to treat several threads as a group, that is up
++ to its higher-level code.
++ </para>
++
++ <para>
++ Tracing begins by attaching an engine to a thread, using
++ <function>utrace_attach_task</function> or
++ <function>utrace_attach_pid</function>. If successful, it returns a
++ pointer that is the handle used in all other calls.
++ </para>
++
++ </sect1>
++
++ <sect1 id="callbacks"><title>Events and Callbacks</title>
++
++ <para>
++ An attached engine does nothing by default. An engine makes something
++ happen by requesting callbacks via <function>utrace_set_events</function>
++ and poking the thread with <function>utrace_control</function>.
++ The synchronization issues related to these two calls
++ are discussed further below in <xref linkend="teardown"/>.
++ </para>
++
++ <para>
++ Events are specified using the macro
++ <constant>UTRACE_EVENT(<replaceable>type</replaceable>)</constant>.
++ Each event type is associated with a callback in <structname>struct
++ utrace_engine_ops</structname>. A tracing engine can leave unused
++ callbacks <constant>NULL</constant>. The only callbacks required
++ are those used by the event flags it sets.
++ </para>
++
++ <para>
++ Many engines can be attached to each thread. When a thread has an
++ event, each engine gets a callback if it has set the event flag for
++ that event type. For most events, engines are called in the order they
++ attached. Engines that attach after the event has occurred do not get
++ callbacks for that event. This includes any new engines just attached
++ by an existing engine's callback function. Once the sequence of
++ callbacks for that one event has completed, such new engines are then
++ eligible in the next sequence that starts when there is another event.
++ </para>
++
++ <para>
++ Event reporting callbacks have details particular to the event type,
++ but are all called in similar environments and have the same
++ constraints. Callbacks are made from safe points, where no locks
++ are held, no special resources are pinned (usually), and the
++ user-mode state of the thread is accessible. So, callback code has
++ a pretty free hand. But to be a good citizen, callback code should
++ never block for long periods. It is fine to block in
++ <function>kmalloc</function> and the like, but never wait for i/o or
++ for user mode to do something. If you need the thread to wait, use
++ <constant>UTRACE_STOP</constant> and return from the callback
++ quickly. When your i/o finishes or whatever, you can use
++ <function>utrace_control</function> to resume the thread.
++ </para>
++
++ <para>
++ The <constant>UTRACE_EVENT(SYSCALL_ENTRY)</constant> event is a special
++ case. While other events happen in the kernel when it will return to
++ user mode soon, this event happens when entering the kernel before it
++ will proceed with the work requested from user mode. Because of this
++ difference, the <function>report_syscall_entry</function> callback is
++ special in two ways. For this event, engines are called in reverse of
++ the normal order (this includes the <function>report_quiesce</function>
++ call that precedes a <function>report_syscall_entry</function> call).
++ This preserves the semantics that the last engine to attach is called
++ "closest to user mode"--the engine that is first to see a thread's user
++ state when it enters the kernel is also the last to see that state when
++ the thread returns to user mode. For the same reason, if these
++ callbacks use <constant>UTRACE_STOP</constant> (see the next section),
++ the thread stops immediately after callbacks rather than only when it's
++ ready to return to user mode; when allowed to resume, it will actually
++ attempt the system call indicated by the register values at that time.
++ </para>
++
++ </sect1>
++
++ <sect1 id="safely"><title>Stopping Safely</title>
++
++ <sect2 id="well-behaved"><title>Writing well-behaved callbacks</title>
++
++ <para>
++ Well-behaved callbacks are important to maintain two essential
++ properties of the interface. The first of these is that unrelated
++ tracing engines should not interfere with each other. If your engine's
++ event callback does not return quickly, then another engine won't get
++ the event notification in a timely manner. The second important
++ property is that tracing should be as noninvasive as possible to the
++ normal operation of the system overall and of the traced thread in
++ particular. That is, attached tracing engines should not perturb a
++ thread's behavior, except to the extent that changing its user-visible
++ state is explicitly what you want to do. (Obviously some perturbation
++ is unavoidable, primarily timing changes, ranging from small delays due
++ to the overhead of tracing, to arbitrary pauses in user code execution
++ when a user stops a thread with a debugger for examination.) Even when
++ you explicitly want the perturbation of making the traced thread block,
++ just blocking directly in your callback has more unwanted effects. For
++ example, the <constant>CLONE</constant> event callbacks are called when
++ the new child thread has been created but not yet started running; the
++ child can never be scheduled until the <constant>CLONE</constant>
++ tracing callbacks return. (This allows engines tracing the parent to
++ attach to the child.) If a <constant>CLONE</constant> event callback
++ blocks the parent thread, it also prevents the child thread from
++ running (even to process a <constant>SIGKILL</constant>). If what you
++ want is to make both the parent and child block, then use
++ <function>utrace_attach_task</function> on the child and then use
++ <constant>UTRACE_STOP</constant> on both threads. A more crucial
++ problem with blocking in callbacks is that it can prevent
++ <constant>SIGKILL</constant> from working. A thread that is blocking
++ due to <constant>UTRACE_STOP</constant> will still wake up and die
++ immediately when sent a <constant>SIGKILL</constant>, as all threads
++ should. Relying on the <application>utrace</application>
++ infrastructure rather than on private synchronization calls in event
++ callbacks is an important way to help keep tracing robustly
++ noninvasive.
++ </para>
++
++ </sect2>
++
++ <sect2 id="UTRACE_STOP"><title>Using <constant>UTRACE_STOP</constant></title>
++
++ <para>
++ To control another thread and access its state, it must be stopped
++ with <constant>UTRACE_STOP</constant>. This means that it is
++ stopped and won't start running again while we access it. When a
++ thread is not already stopped, <function>utrace_control</function>
++ returns <constant>-EINPROGRESS</constant> and an engine must wait
++ for an event callback when the thread is ready to stop. The thread
++ may be running on another CPU or may be blocked. When it is ready
++ to be examined, it will make callbacks to engines that set the
++ <constant>UTRACE_EVENT(QUIESCE)</constant> event bit. To wake up an
++ interruptible wait, use <constant>UTRACE_INTERRUPT</constant>.
++ </para>
++
++ <para>
++ As long as some engine has used <constant>UTRACE_STOP</constant> and
++ not called <function>utrace_control</function> to resume the thread,
++ then the thread will remain stopped. <constant>SIGKILL</constant>
++ will wake it up, but it will not run user code. When the stop is
++ cleared with <function>utrace_control</function> or a callback
++ return value, the thread starts running again.
++ (See also <xref linkend="teardown"/>.)
++ </para>
++
++ </sect2>
++
++ </sect1>
++
++ <sect1 id="teardown"><title>Tear-down Races</title>
++
++ <sect2 id="SIGKILL"><title>Primacy of <constant>SIGKILL</constant></title>
++ <para>
++ Ordinarily synchronization issues for tracing engines are kept fairly
++ straightforward by using <constant>UTRACE_STOP</constant>. You ask a
++ thread to stop, and then once it makes the
++ <function>report_quiesce</function> callback it cannot do anything else
++ that would result in another callback, until you let it with a
++ <function>utrace_control</function> call. This simple arrangement
++ avoids complex and error-prone code in each one of a tracing engine's
++ event callbacks to keep them serialized with the engine's other
++ operations done on that thread from another thread of control.
++ However, giving tracing engines complete power to keep a traced thread
++ stuck in place runs afoul of a more important kind of simplicity that
++ the kernel overall guarantees: nothing can prevent or delay
++ <constant>SIGKILL</constant> from making a thread die and release its
++ resources. To preserve this important property of
++ <constant>SIGKILL</constant>, it as a special case can break
++ <constant>UTRACE_STOP</constant> like nothing else normally can. This
++ includes both explicit <constant>SIGKILL</constant> signals and the
++ implicit <constant>SIGKILL</constant> sent to each other thread in the
++ same thread group by a thread doing an exec, or processing a fatal
++ signal, or making an <function>exit_group</function> system call. A
++ tracing engine can prevent a thread from beginning the exit or exec or
++ dying by signal (other than <constant>SIGKILL</constant>) if it is
++ attached to that thread, but once the operation begins, no tracing
++ engine can prevent or delay all other threads in the same thread group
++ dying.
++ </para>
++ </sect2>
++
++ <sect2 id="reap"><title>Final callbacks</title>
++ <para>
++ The <function>report_reap</function> callback is always the final event
++ in the life cycle of a traced thread. Tracing engines can use this as
++ the trigger to clean up their own data structures. The
++ <function>report_death</function> callback is always the penultimate
++ event a tracing engine might see; it's seen unless the thread was
++ already in the midst of dying when the engine attached. Many tracing
++ engines will have no interest in when a parent reaps a dead process,
++ and nothing they want to do with a zombie thread once it dies; for
++ them, the <function>report_death</function> callback is the natural
++ place to clean up data structures and detach. To facilitate writing
++ such engines robustly, given the asynchrony of
++ <constant>SIGKILL</constant>, and without error-prone manual
++ implementation of synchronization schemes, the
++ <application>utrace</application> infrastructure provides some special
++ guarantees about the <function>report_death</function> and
++ <function>report_reap</function> callbacks. It still takes some care
++ to be sure your tracing engine is robust to tear-down races, but these
++ rules make it reasonably straightforward and concise to handle a lot of
++ corner cases correctly.
++ </para>
++ </sect2>
++
++ <sect2 id="refcount"><title>Engine and task pointers</title>
++ <para>
++ The first sort of guarantee concerns the core data structures
++ themselves. <structname>struct utrace_engine</structname> is
++ a reference-counted data structure. While you hold a reference, an
++ engine pointer will always stay valid so that you can safely pass it to
++ any <application>utrace</application> call. Each call to
++ <function>utrace_attach_task</function> or
++ <function>utrace_attach_pid</function> returns an engine pointer with a
++ reference belonging to the caller. You own that reference until you
++ drop it using <function>utrace_engine_put</function>. There is an
++ implicit reference on the engine while it is attached. So if you drop
++ your only reference, and then use
++ <function>utrace_attach_task</function> without
++ <constant>UTRACE_ATTACH_CREATE</constant> to look up that same engine,
++ you will get the same pointer with a new reference to replace the one
++ you dropped, just like calling <function>utrace_engine_get</function>.
++ When an engine has been detached, either explicitly with
++ <constant>UTRACE_DETACH</constant> or implicitly after
++ <function>report_reap</function>, then any references you hold are all
++ that keep the old engine pointer alive.
++ </para>
++
++ <para>
++ There is nothing a kernel module can do to keep a <structname>struct
++ task_struct</structname> alive outside of
++ <function>rcu_read_lock</function>. When the task dies and is reaped
++ by its parent (or itself), that structure can be freed so that any
++ dangling pointers you have stored become invalid.
++ <application>utrace</application> will not prevent this, but it can
++ help you detect it safely. By definition, a task that has been reaped
++ has had all its engines detached. All
++ <application>utrace</application> calls can be safely called on a
++ detached engine if the caller holds a reference on that engine pointer,
++ even if the task pointer passed in the call is invalid. All calls
++ return <constant>-ESRCH</constant> for a detached engine, which tells
++ you that the task pointer you passed could be invalid now. Since
++ <function>utrace_control</function> and
++ <function>utrace_set_events</function> do not block, you can call those
++ inside a <function>rcu_read_lock</function> section and be sure after
++ they don't return <constant>-ESRCH</constant> that the task pointer is
++ still valid until <function>rcu_read_unlock</function>. The
++ infrastructure never holds task references of its own. Though neither
++ <function>rcu_read_lock</function> nor any other lock is held while
++ making a callback, it's always guaranteed that the <structname>struct
++ task_struct</structname> and the <structname>struct
++ utrace_engine</structname> passed as arguments remain valid
++ until the callback function returns.
++ </para>
++
++ <para>
++ The common means for safely holding task pointers that is available to
++ kernel modules is to use <structname>struct pid</structname>, which
++ permits <function>put_pid</function> from kernel modules. When using
++ that, the calls <function>utrace_attach_pid</function>,
++ <function>utrace_control_pid</function>,
++ <function>utrace_set_events_pid</function>, and
++ <function>utrace_barrier_pid</function> are available.
++ </para>
++ </sect2>
++
++ <sect2 id="reap-after-death">
++ <title>
++ Serialization of <constant>DEATH</constant> and <constant>REAP</constant>
++ </title>
++ <para>
++ The second guarantee is the serialization of
++ <constant>DEATH</constant> and <constant>REAP</constant> event
++ callbacks for a given thread. The actual reaping by the parent
++ (<function>release_task</function> call) can occur simultaneously
++ while the thread is still doing the final steps of dying, including
++ the <function>report_death</function> callback. If a tracing engine
++ has requested both <constant>DEATH</constant> and
++ <constant>REAP</constant> event reports, it's guaranteed that the
++ <function>report_reap</function> callback will not be made until
++ after the <function>report_death</function> callback has returned.
++ If the <function>report_death</function> callback itself detaches
++ from the thread, then the <function>report_reap</function> callback
++ will never be made. Thus it is safe for a
++ <function>report_death</function> callback to clean up data
++ structures and detach.
++ </para>
++ </sect2>
++
++ <sect2 id="interlock"><title>Interlock with final callbacks</title>
++ <para>
++ The final sort of guarantee is that a tracing engine will know for sure
++ whether or not the <function>report_death</function> and/or
++ <function>report_reap</function> callbacks will be made for a certain
++ thread. These tear-down races are disambiguated by the error return
++ values of <function>utrace_set_events</function> and
++ <function>utrace_control</function>. Normally
++ <function>utrace_control</function> called with
++ <constant>UTRACE_DETACH</constant> returns zero, and this means that no
++ more callbacks will be made. If the thread is in the midst of dying,
++ it returns <constant>-EALREADY</constant> to indicate that the
++ <constant>report_death</constant> callback may already be in progress;
++ when you get this error, you know that any cleanup your
++ <function>report_death</function> callback does is about to happen or
++ has just happened--note that if the <function>report_death</function>
++ callback does not detach, the engine remains attached until the thread
++ gets reaped. If the thread is in the midst of being reaped,
++ <function>utrace_control</function> returns <constant>-ESRCH</constant>
++ to indicate that the <function>report_reap</function> callback may
++ already be in progress; this means the engine is implicitly detached
++ when the callback completes. This makes it possible for a tracing
++ engine that has decided asynchronously to detach from a thread to
++ safely clean up its data structures, knowing that no
++ <function>report_death</function> or <function>report_reap</function>
++ callback will try to do the same. <constant>utrace_detach</constant>
++ returns <constant>-ESRCH</constant> when the <structname>struct
++ utrace_engine</structname> has already been detached, but is
++ still a valid pointer because of its reference count. A tracing engine
++ can use this to safely synchronize its own independent multiple threads
++ of control with each other and with its event callbacks that detach.
++ </para>
++
++ <para>
++ In the same vein, <function>utrace_set_events</function> normally
++ returns zero; if the target thread was stopped before the call, then
++ after a successful call, no event callbacks not requested in the new
++ flags will be made. It fails with <constant>-EALREADY</constant> if
++ you try to clear <constant>UTRACE_EVENT(DEATH)</constant> when the
++ <function>report_death</function> callback may already have begun, or if
++ you try to newly set <constant>UTRACE_EVENT(DEATH)</constant> or
++ <constant>UTRACE_EVENT(QUIESCE)</constant> when the target is already
++ dead or dying. Like <function>utrace_control</function>, it returns
++ <constant>-ESRCH</constant> when the <function>report_reap</function>
++ callback may already have begun, or the thread has already been detached
++ (including forcible detach on reaping). This lets the tracing engine
++ know for sure which event callbacks it will or won't see after
++ <function>utrace_set_events</function> has returned. By checking for
++ errors, it can know whether to clean up its data structures immediately
++ or to let its callbacks do the work.
++ </para>
++ </sect2>
++
++ <sect2 id="barrier"><title>Using <function>utrace_barrier</function></title>
++ <para>
++ When a thread is safely stopped, calling
++ <function>utrace_control</function> with <constant>UTRACE_DETACH</constant>
++ or calling <function>utrace_set_events</function> to disable some events
++ ensures synchronously that your engine won't get any more of the callbacks
++ that have been disabled (none at all when detaching). But these can also
++ be used while the thread is not stopped, when it might be simultaneously
++ making a callback to your engine. For this situation, these calls return
++ <constant>-EINPROGRESS</constant> when it's possible a callback is in
++ progress. If you are not prepared to have your old callbacks still run,
++ then you can synchronize to be sure all the old callbacks are finished,
++ using <function>utrace_barrier</function>. This is necessary if the
++ kernel module containing your callback code is going to be unloaded.
++ </para>
++ <para>
++ After using <constant>UTRACE_DETACH</constant> once, further calls to
++ <function>utrace_control</function> with the same engine pointer will
++ return <constant>-ESRCH</constant>. In contrast, after getting
++ <constant>-EINPROGRESS</constant> from
++ <function>utrace_set_events</function>, you can call
++ <function>utrace_set_events</function> again later and if it returns zero
++ then know the old callbacks have finished.
++ </para>
++ <para>
++ Unlike all other calls, <function>utrace_barrier</function> (and
++ <function>utrace_barrier_pid</function>) will accept any engine pointer you
++ hold a reference on, even if <constant>UTRACE_DETACH</constant> has already
++ been used. After any <function>utrace_control</function> or
++ <function>utrace_set_events</function> call (these do not block), you can
++ call <function>utrace_barrier</function> to block until callbacks have
++ finished. This returns <constant>-ESRCH</constant> only if the engine is
++ completely detached (finished all callbacks). Otherwise it waits
++ until the thread is definitely not in the midst of a callback to this
++ engine and then returns zero, but can return
++ <constant>-ERESTARTSYS</constant> if its wait is interrupted.
++ </para>
++ </sect2>
++
++</sect1>
++
++</chapter>
++
++<chapter id="core"><title>utrace core API</title>
++
++<para>
++ The utrace API is declared in <filename><linux/utrace.h></filename>.
++</para>
++
++!Iinclude/linux/utrace.h
++!Ekernel/utrace.c
++
++</chapter>
++
++<chapter id="machine"><title>Machine State</title>
++
++<para>
++ The <function>task_current_syscall</function> function can be used on any
++ valid <structname>struct task_struct</structname> at any time, and does
++ not even require that <function>utrace_attach_task</function> was used at all.
++</para>
++
++<para>
++ The other ways to access the registers and other machine-dependent state of
++ a task can only be used on a task that is at a known safe point. The safe
++ points are all the places where <function>utrace_set_events</function> can
++ request callbacks (except for the <constant>DEATH</constant> and
++ <constant>REAP</constant> events). So at any event callback, it is safe to
++ examine <varname>current</varname>.
++</para>
++
++<para>
++ One task can examine another only after a callback in the target task that
++ returns <constant>UTRACE_STOP</constant> so that task will not return to user
++ mode after the safe point. This guarantees that the task will not resume
++ until the same engine uses <function>utrace_control</function>, unless the
++ task dies suddenly. To examine safely, one must use a pair of calls to
++ <function>utrace_prepare_examine</function> and
++ <function>utrace_finish_examine</function> surrounding the calls to
++ <structname>struct user_regset</structname> functions or direct examination
++ of task data structures. <function>utrace_prepare_examine</function> returns
++ an error if the task is not properly stopped, or is dead. After a
++ successful examination, the paired <function>utrace_finish_examine</function>
++ call returns an error if the task ever woke up during the examination. If
++ so, any data gathered may be scrambled and should be discarded. This means
++ there was a spurious wake-up (which should not happen), or a sudden death.
++</para>
++
++<sect1 id="regset"><title><structname>struct user_regset</structname></title>
++
++<para>
++ The <structname>struct user_regset</structname> API
++ is declared in <filename><linux/regset.h></filename>.
++</para>
++
++!Finclude/linux/regset.h
++
++</sect1>
++
++<sect1 id="task_current_syscall">
++ <title><filename>System Call Information</filename></title>
++
++<para>
++ This function is declared in <filename><linux/ptrace.h></filename>.
++</para>
++
++!Elib/syscall.c
++
++</sect1>
++
++<sect1 id="syscall"><title><filename>System Call Tracing</filename></title>
++
++<para>
++ The arch API for system call information is declared in
++ <filename><asm/syscall.h></filename>.
++ Each of these calls can be used only at system call entry tracing,
++ or can be used only at system call exit and the subsequent safe points
++ before returning to user mode.
++ At system call entry tracing means either during a
++ <structfield>report_syscall_entry</structfield> callback,
++ or any time after that callback has returned <constant>UTRACE_STOP</constant>.
++</para>
++
++!Finclude/asm-generic/syscall.h
++
++</sect1>
++
++</chapter>
++
++<chapter id="internals"><title>Kernel Internals</title>
++
++<para>
++ This chapter covers the interface to the tracing infrastructure
++ from the core of the kernel and the architecture-specific code.
++ This is for maintainers of the kernel and arch code, and not relevant
++ to using the tracing facilities described in preceding chapters.
++</para>
++
++<sect1 id="tracehook"><title>Core Calls In</title>
++
++<para>
++ These calls are declared in <filename><linux/tracehook.h></filename>.
++ The core kernel calls these functions at various important places.
++</para>
++
++!Finclude/linux/tracehook.h
++
++</sect1>
++
++<sect1 id="arch"><title>Architecture Calls Out</title>
++
++<para>
++ An arch that has done all these things sets
++ <constant>CONFIG_HAVE_ARCH_TRACEHOOK</constant>.
++ This is required to enable the <application>utrace</application> code.
++</para>
++
++<sect2 id="arch-ptrace"><title><filename><asm/ptrace.h></filename></title>
++
++<para>
++ An arch defines these in <filename><asm/ptrace.h></filename>
++ if it supports hardware single-step or block-step features.
++</para>
++
++!Finclude/linux/ptrace.h arch_has_single_step arch_has_block_step
++!Finclude/linux/ptrace.h user_enable_single_step user_enable_block_step
++!Finclude/linux/ptrace.h user_disable_single_step
++
++</sect2>
++
++<sect2 id="arch-syscall">
++ <title><filename><asm/syscall.h></filename></title>
++
++ <para>
++ An arch provides <filename><asm/syscall.h></filename> that
++ defines these as inlines, or declares them as exported functions.
++ These interfaces are described in <xref linkend="syscall"/>.
++ </para>
++
++</sect2>
++
++<sect2 id="arch-tracehook">
++ <title><filename><linux/tracehook.h></filename></title>
++
++ <para>
++ An arch must define <constant>TIF_NOTIFY_RESUME</constant>
++ and <constant>TIF_SYSCALL_TRACE</constant>
++ in its <filename><asm/thread_info.h></filename>.
++ The arch code must call the following functions, all declared
++ in <filename><linux/tracehook.h></filename> and
++ described in <xref linkend="tracehook"/>:
++
++ <itemizedlist>
++ <listitem>
++ <para><function>tracehook_notify_resume</function></para>
++ </listitem>
++ <listitem>
++ <para><function>tracehook_report_syscall_entry</function></para>
++ </listitem>
++ <listitem>
++ <para><function>tracehook_report_syscall_exit</function></para>
++ </listitem>
++ <listitem>
++ <para><function>tracehook_signal_handler</function></para>
++ </listitem>
++ </itemizedlist>
++
++ </para>
++
++</sect2>
++
++</sect1>
++
++</chapter>
++
++</book>
+diff --git a/fs/proc/array.c b/fs/proc/array.c
+index 9b45ee8..496fef3 100644
+--- a/fs/proc/array.c
++++ b/fs/proc/array.c
+@@ -81,6 +81,7 @@
+ #include <linux/pid_namespace.h>
+ #include <linux/ptrace.h>
+ #include <linux/tracehook.h>
++#include <linux/utrace.h>
+
+ #include <asm/pgtable.h>
+ #include <asm/processor.h>
+@@ -192,6 +193,8 @@ static inline void task_state(struct seq_file *m, struct pid_namespace *ns,
+ cred->uid, cred->euid, cred->suid, cred->fsuid,
+ cred->gid, cred->egid, cred->sgid, cred->fsgid);
+
++ task_utrace_proc_status(m, p);
++
+ task_lock(p);
+ if (p->files)
+ fdt = files_fdtable(p->files);
+diff --git a/include/linux/sched.h b/include/linux/sched.h
+index a837b20..b87de83 100644
+--- a/include/linux/sched.h
++++ b/include/linux/sched.h
+@@ -1397,6 +1397,11 @@ struct task_struct {
+ #endif
+ seccomp_t seccomp;
+
++#ifdef CONFIG_UTRACE
++ struct utrace *utrace;
++ unsigned long utrace_flags;
++#endif
++
+ /* Thread group tracking */
+ u32 parent_exec_id;
+ u32 self_exec_id;
+diff --git a/include/linux/tracehook.h b/include/linux/tracehook.h
+index e95f523..7d7bdde 100644
+--- a/include/linux/tracehook.h
++++ b/include/linux/tracehook.h
+@@ -49,6 +49,7 @@
+ #include <linux/sched.h>
+ #include <linux/ptrace.h>
+ #include <linux/security.h>
++#include <linux/utrace.h>
+ struct linux_binprm;
+
+ /**
+@@ -63,6 +64,8 @@ struct linux_binprm;
+ */
+ static inline int tracehook_expect_breakpoints(struct task_struct *task)
+ {
++ if (unlikely(task_utrace_flags(task) & UTRACE_EVENT(SIGNAL_CORE)))
++ return 1;
+ return (task_ptrace(task) & PT_PTRACED) != 0;
+ }
+
+@@ -111,6 +114,9 @@ static inline void ptrace_report_syscall(struct pt_regs *regs)
+ static inline __must_check int tracehook_report_syscall_entry(
+ struct pt_regs *regs)
+ {
++ if ((task_utrace_flags(current) & UTRACE_EVENT(SYSCALL_ENTRY)) &&
++ utrace_report_syscall_entry(regs))
++ return 1;
+ ptrace_report_syscall(regs);
+ return 0;
+ }
+@@ -134,6 +140,9 @@ static inline __must_check int tracehook_report_syscall_entry(
+ */
+ static inline void tracehook_report_syscall_exit(struct pt_regs *regs, int step)
+ {
++ if (task_utrace_flags(current) & UTRACE_EVENT(SYSCALL_EXIT))
++ utrace_report_syscall_exit(regs);
++
+ if (step) {
+ siginfo_t info;
+ user_single_step_siginfo(current, regs, &info);
+@@ -201,6 +210,8 @@ static inline void tracehook_report_exec(struct linux_binfmt *fmt,
+ struct linux_binprm *bprm,
+ struct pt_regs *regs)
+ {
++ if (unlikely(task_utrace_flags(current) & UTRACE_EVENT(EXEC)))
++ utrace_report_exec(fmt, bprm, regs);
+ if (!ptrace_event(PT_TRACE_EXEC, PTRACE_EVENT_EXEC, 0) &&
+ unlikely(task_ptrace(current) & PT_PTRACED))
+ send_sig(SIGTRAP, current, 0);
+@@ -218,10 +229,37 @@ static inline void tracehook_report_exec(struct linux_binfmt *fmt,
+ */
+ static inline void tracehook_report_exit(long *exit_code)
+ {
++ if (unlikely(task_utrace_flags(current) & UTRACE_EVENT(EXIT)))
++ utrace_report_exit(exit_code);
+ ptrace_event(PT_TRACE_EXIT, PTRACE_EVENT_EXIT, *exit_code);
+ }
+
+ /**
++ * tracehook_init_task - task_struct has just been copied
++ * @task: new &struct task_struct just copied from parent
++ *
++ * Called from do_fork() when @task has just been duplicated.
++ * After this, @task will be passed to tracehook_free_task()
++ * even if the rest of its setup fails before it is fully created.
++ */
++static inline void tracehook_init_task(struct task_struct *task)
++{
++ utrace_init_task(task);
++}
++
++/**
++ * tracehook_free_task - task_struct is being freed
++ * @task: dead &struct task_struct being freed
++ *
++ * Called from free_task() when @task is no longer in use.
++ */
++static inline void tracehook_free_task(struct task_struct *task)
++{
++ if (task_utrace_struct(task))
++ utrace_free_task(task);
++}
++
++/**
+ * tracehook_prepare_clone - prepare for new child to be cloned
+ * @clone_flags: %CLONE_* flags from clone/fork/vfork system call
+ *
+@@ -285,6 +323,8 @@ static inline void tracehook_report_clone(struct pt_regs *regs,
+ unsigned long clone_flags,
+ pid_t pid, struct task_struct *child)
+ {
++ if (unlikely(task_utrace_flags(current) & UTRACE_EVENT(CLONE)))
++ utrace_report_clone(clone_flags, child);
+ if (unlikely(task_ptrace(child))) {
+ /*
+ * It doesn't matter who attached/attaching to this
+@@ -317,6 +357,9 @@ static inline void tracehook_report_clone_complete(int trace,
+ pid_t pid,
+ struct task_struct *child)
+ {
++ if (unlikely(task_utrace_flags(current) & UTRACE_EVENT(CLONE)) &&
++ (clone_flags & CLONE_VFORK))
++ utrace_finish_vfork(current);
+ if (unlikely(trace))
+ ptrace_event(0, trace, pid);
+ }
+@@ -351,6 +394,10 @@ static inline void tracehook_report_vfork_done(struct task_struct *child,
+ */
+ static inline void tracehook_prepare_release_task(struct task_struct *task)
+ {
++ /* see utrace_add_engine() about this barrier */
++ smp_mb();
++ if (task_utrace_flags(task))
++ utrace_maybe_reap(task, task_utrace_struct(task), true);
+ }
+
+ /**
+@@ -365,6 +412,7 @@ static inline void tracehook_prepare_release_task(struct task_struct *task)
+ static inline void tracehook_finish_release_task(struct task_struct *task)
+ {
+ ptrace_release_task(task);
++ BUG_ON(task->exit_state != EXIT_DEAD);
+ }
+
+ /**
+@@ -386,6 +434,8 @@ static inline void tracehook_signal_handler(int sig, siginfo_t *info,
+ const struct k_sigaction *ka,
+ struct pt_regs *regs, int stepping)
+ {
++ if (task_utrace_flags(current))
++ utrace_signal_handler(current, stepping);
+ if (stepping)
+ ptrace_notify(SIGTRAP);
+ }
+@@ -403,6 +453,8 @@ static inline void tracehook_signal_handler(int sig, siginfo_t *info,
+ static inline int tracehook_consider_ignored_signal(struct task_struct *task,
+ int sig)
+ {
++ if (unlikely(task_utrace_flags(task) & UTRACE_EVENT(SIGNAL_IGN)))
++ return 1;
+ return (task_ptrace(task) & PT_PTRACED) != 0;
+ }
+
+@@ -422,6 +474,9 @@ static inline int tracehook_consider_ignored_signal(struct task_struct *task,
+ static inline int tracehook_consider_fatal_signal(struct task_struct *task,
+ int sig)
+ {
++ if (unlikely(task_utrace_flags(task) & (UTRACE_EVENT(SIGNAL_TERM) |
++ UTRACE_EVENT(SIGNAL_CORE))))
++ return 1;
+ return (task_ptrace(task) & PT_PTRACED) != 0;
+ }
+
+@@ -436,6 +491,8 @@ static inline int tracehook_consider_fatal_signal(struct task_struct *task,
+ */
+ static inline int tracehook_force_sigpending(void)
+ {
++ if (unlikely(task_utrace_flags(current)))
++ return utrace_interrupt_pending();
+ return 0;
+ }
+
+@@ -465,6 +522,8 @@ static inline int tracehook_get_signal(struct task_struct *task,
+ siginfo_t *info,
+ struct k_sigaction *return_ka)
+ {
++ if (unlikely(task_utrace_flags(task)))
++ return utrace_get_signal(task, regs, info, return_ka);
+ return 0;
+ }
+
+@@ -475,6 +534,8 @@ static inline int tracehook_get_signal(struct task_struct *task,
+ */
+ static inline void tracehook_finish_jctl(void)
+ {
++ if (task_utrace_flags(current))
++ utrace_finish_stop();
+ }
+
+ #define DEATH_REAP -1
+@@ -497,6 +558,8 @@ static inline void tracehook_finish_jctl(void)
+ static inline int tracehook_notify_death(struct task_struct *task,
+ void **death_cookie, int group_dead)
+ {
++ *death_cookie = task_utrace_struct(task);
++
+ if (task_detached(task))
+ return task->ptrace ? SIGCHLD : DEATH_REAP;
+
+@@ -533,6 +596,15 @@ static inline void tracehook_report_death(struct task_struct *task,
+ int signal, void *death_cookie,
+ int group_dead)
+ {
++ /*
++ * If utrace_set_events() was just called to enable
++ * UTRACE_EVENT(DEATH), then we are obliged to call
++ * utrace_report_death() and not miss it. utrace_set_events()
++ * checks @task->exit_state under tasklist_lock to synchronize
++ * with exit_notify(), the caller.
++ */
++ if (task_utrace_flags(task) & _UTRACE_DEATH_EVENTS)
++ utrace_report_death(task, death_cookie, group_dead, signal);
+ }
+
+ #ifdef TIF_NOTIFY_RESUME
+@@ -562,10 +634,21 @@ static inline void set_notify_resume(struct task_struct *task)
+ * asynchronously, this will be called again before we return to
+ * user mode.
+ *
+- * Called without locks.
++ * Called without locks. However, on some machines this may be
++ * called with interrupts disabled.
+ */
+ static inline void tracehook_notify_resume(struct pt_regs *regs)
+ {
++ struct task_struct *task = current;
++ /*
++ * Prevent the following store/load from getting ahead of the
++ * caller which clears TIF_NOTIFY_RESUME. This pairs with the
++ * implicit mb() before setting TIF_NOTIFY_RESUME in
++ * set_notify_resume().
++ */
++ smp_mb();
++ if (task_utrace_flags(task))
++ utrace_resume(task, regs);
+ }
+ #endif /* TIF_NOTIFY_RESUME */
+
+diff --git a/include/linux/utrace.h b/include/linux/utrace.h
+new file mode 100644
+index 0000000..f251efe
+--- /dev/null
++++ b/include/linux/utrace.h
+@@ -0,0 +1,692 @@
++/*
++ * utrace infrastructure interface for debugging user processes
++ *
++ * Copyright (C) 2006-2009 Red Hat, Inc. All rights reserved.
++ *
++ * This copyrighted material is made available to anyone wishing to use,
++ * modify, copy, or redistribute it subject to the terms and conditions
++ * of the GNU General Public License v.2.
++ *
++ * Red Hat Author: Roland McGrath.
++ *
++ * This interface allows for notification of interesting events in a
++ * thread. It also mediates access to thread state such as registers.
++ * Multiple unrelated users can be associated with a single thread.
++ * We call each of these a tracing engine.
++ *
++ * A tracing engine starts by calling utrace_attach_task() or
++ * utrace_attach_pid() on the chosen thread, passing in a set of hooks
++ * (&struct utrace_engine_ops), and some associated data. This produces a
++ * &struct utrace_engine, which is the handle used for all other
++ * operations. An attached engine has its ops vector, its data, and an
++ * event mask controlled by utrace_set_events().
++ *
++ * For each event bit that is set, that engine will get the
++ * appropriate ops->report_*() callback when the event occurs. The
++ * &struct utrace_engine_ops need not provide callbacks for an event
++ * unless the engine sets one of the associated event bits.
++ */
++
++#ifndef _LINUX_UTRACE_H
++#define _LINUX_UTRACE_H 1
++
++#include <linux/list.h>
++#include <linux/kref.h>
++#include <linux/signal.h>
++#include <linux/sched.h>
++
++struct linux_binprm;
++struct pt_regs;
++struct utrace;
++struct user_regset;
++struct user_regset_view;
++
++/*
++ * Event bits passed to utrace_set_events().
++ * These appear in &struct task_struct. at utrace_flags
++ * and &struct utrace_engine. at flags.
++ */
++enum utrace_events {
++ _UTRACE_EVENT_QUIESCE, /* Thread is available for examination. */
++ _UTRACE_EVENT_REAP, /* Zombie reaped, no more tracing possible. */
++ _UTRACE_EVENT_CLONE, /* Successful clone/fork/vfork just done. */
++ _UTRACE_EVENT_EXEC, /* Successful execve just completed. */
++ _UTRACE_EVENT_EXIT, /* Thread exit in progress. */
++ _UTRACE_EVENT_DEATH, /* Thread has died. */
++ _UTRACE_EVENT_SYSCALL_ENTRY, /* User entered kernel for system call. */
++ _UTRACE_EVENT_SYSCALL_EXIT, /* Returning to user after system call. */
++ _UTRACE_EVENT_SIGNAL, /* Signal delivery will run a user handler. */
++ _UTRACE_EVENT_SIGNAL_IGN, /* No-op signal to be delivered. */
++ _UTRACE_EVENT_SIGNAL_STOP, /* Signal delivery will suspend. */
++ _UTRACE_EVENT_SIGNAL_TERM, /* Signal delivery will terminate. */
++ _UTRACE_EVENT_SIGNAL_CORE, /* Signal delivery will dump core. */
++ _UTRACE_EVENT_JCTL, /* Job control stop or continue completed. */
++ _UTRACE_NEVENTS
++};
++#define UTRACE_EVENT(type) (1UL << _UTRACE_EVENT_##type)
++
++/*
++ * All the kinds of signal events.
++ * These all use the @report_signal() callback.
++ */
++#define UTRACE_EVENT_SIGNAL_ALL (UTRACE_EVENT(SIGNAL) \
++ | UTRACE_EVENT(SIGNAL_IGN) \
++ | UTRACE_EVENT(SIGNAL_STOP) \
++ | UTRACE_EVENT(SIGNAL_TERM) \
++ | UTRACE_EVENT(SIGNAL_CORE))
++/*
++ * Both kinds of syscall events; these call the @report_syscall_entry()
++ * and @report_syscall_exit() callbacks, respectively.
++ */
++#define UTRACE_EVENT_SYSCALL \
++ (UTRACE_EVENT(SYSCALL_ENTRY) | UTRACE_EVENT(SYSCALL_EXIT))
++
++/*
++ * The event reports triggered synchronously by task death.
++ */
++#define _UTRACE_DEATH_EVENTS (UTRACE_EVENT(DEATH) | UTRACE_EVENT(QUIESCE))
++
++/*
++ * Hooks in <linux/tracehook.h> call these entry points to the utrace dispatch.
++ */
++void utrace_free_task(struct task_struct *);
++bool utrace_interrupt_pending(void);
++void utrace_resume(struct task_struct *, struct pt_regs *);
++void utrace_finish_stop(void);
++void utrace_maybe_reap(struct task_struct *, struct utrace *, bool);
++int utrace_get_signal(struct task_struct *, struct pt_regs *,
++ siginfo_t *, struct k_sigaction *);
++void utrace_report_clone(unsigned long, struct task_struct *);
++void utrace_finish_vfork(struct task_struct *);
++void utrace_report_exit(long *exit_code);
++void utrace_report_death(struct task_struct *, struct utrace *, bool, int);
++void utrace_report_jctl(int notify, int type);
++void utrace_report_exec(struct linux_binfmt *, struct linux_binprm *,
++ struct pt_regs *regs);
++bool utrace_report_syscall_entry(struct pt_regs *);
++void utrace_report_syscall_exit(struct pt_regs *);
++void utrace_signal_handler(struct task_struct *, int);
++
++#ifndef CONFIG_UTRACE
++
++/*
++ * <linux/tracehook.h> uses these accessors to avoid #ifdef CONFIG_UTRACE.
++ */
++static inline unsigned long task_utrace_flags(struct task_struct *task)
++{
++ return 0;
++}
++static inline struct utrace *task_utrace_struct(struct task_struct *task)
++{
++ return NULL;
++}
++static inline void utrace_init_task(struct task_struct *child)
++{
++}
++
++static inline void task_utrace_proc_status(struct seq_file *m,
++ struct task_struct *p)
++{
++}
++
++#else /* CONFIG_UTRACE */
++
++static inline unsigned long task_utrace_flags(struct task_struct *task)
++{
++ return task->utrace_flags;
++}
++
++static inline struct utrace *task_utrace_struct(struct task_struct *task)
++{
++ struct utrace *utrace;
++
++ /*
++ * This barrier ensures that any prior load of task->utrace_flags
++ * is ordered before this load of task->utrace. We use those
++ * utrace_flags checks in the hot path to decide to call into
++ * the utrace code. The first attach installs task->utrace before
++ * setting task->utrace_flags nonzero with implicit barrier in
++ * between, see utrace_add_engine().
++ */
++ smp_rmb();
++ utrace = task->utrace;
++
++ smp_read_barrier_depends(); /* See utrace_task_alloc(). */
++ return utrace;
++}
++
++static inline void utrace_init_task(struct task_struct *task)
++{
++ task->utrace_flags = 0;
++ task->utrace = NULL;
++}
++
++void task_utrace_proc_status(struct seq_file *m, struct task_struct *p);
++
++
++/*
++ * Version number of the API defined in this file. This will change
++ * whenever a tracing engine's code would need some updates to keep
++ * working. We maintain this here for the benefit of tracing engine code
++ * that is developed concurrently with utrace API improvements before they
++ * are merged into the kernel, making LINUX_VERSION_CODE checks unwieldy.
++ */
++#define UTRACE_API_VERSION 20091216
++
++/**
++ * enum utrace_resume_action - engine's choice of action for a traced task
++ * @UTRACE_STOP: Stay quiescent after callbacks.
++ * @UTRACE_INTERRUPT: Make @report_signal() callback soon.
++ * @UTRACE_REPORT: Make some callback soon.
++ * @UTRACE_SINGLESTEP: Resume in user mode for one instruction.
++ * @UTRACE_BLOCKSTEP: Resume in user mode until next branch.
++ * @UTRACE_RESUME: Resume normally in user mode.
++ * @UTRACE_DETACH: Detach my engine (implies %UTRACE_RESUME).
++ *
++ * See utrace_control() for detailed descriptions of each action. This is
++ * encoded in the @action argument and the return value for every callback
++ * with a &u32 return value.
++ *
++ * The order of these is important. When there is more than one engine,
++ * each supplies its choice and the smallest value prevails.
++ */
++enum utrace_resume_action {
++ UTRACE_STOP,
++ UTRACE_INTERRUPT,
++ UTRACE_REPORT,
++ UTRACE_SINGLESTEP,
++ UTRACE_BLOCKSTEP,
++ UTRACE_RESUME,
++ UTRACE_DETACH,
++ UTRACE_RESUME_MAX
++};
++#define UTRACE_RESUME_BITS (ilog2(UTRACE_RESUME_MAX) + 1)
++#define UTRACE_RESUME_MASK ((1 << UTRACE_RESUME_BITS) - 1)
++
++/**
++ * utrace_resume_action - &enum utrace_resume_action from callback action
++ * @action: &u32 callback @action argument or return value
++ *
++ * This extracts the &enum utrace_resume_action from @action,
++ * which is the @action argument to a &struct utrace_engine_ops
++ * callback or the return value from one.
++ */
++static inline enum utrace_resume_action utrace_resume_action(u32 action)
++{
++ return action & UTRACE_RESUME_MASK;
++}
++
++/**
++ * enum utrace_signal_action - disposition of signal
++ * @UTRACE_SIGNAL_DELIVER: Deliver according to sigaction.
++ * @UTRACE_SIGNAL_IGN: Ignore the signal.
++ * @UTRACE_SIGNAL_TERM: Terminate the process.
++ * @UTRACE_SIGNAL_CORE: Terminate with core dump.
++ * @UTRACE_SIGNAL_STOP: Deliver as absolute stop.
++ * @UTRACE_SIGNAL_TSTP: Deliver as job control stop.
++ * @UTRACE_SIGNAL_REPORT: Reporting before pending signals.
++ * @UTRACE_SIGNAL_HANDLER: Reporting after signal handler setup.
++ *
++ * This is encoded in the @action argument and the return value for
++ * a @report_signal() callback. It says what will happen to the
++ * signal described by the &siginfo_t parameter to the callback.
++ *
++ * The %UTRACE_SIGNAL_REPORT value is used in an @action argument when
++ * a tracing report is being made before dequeuing any pending signal.
++ * If this is immediately after a signal handler has been set up, then
++ * %UTRACE_SIGNAL_HANDLER is used instead. A @report_signal callback
++ * that uses %UTRACE_SIGNAL_DELIVER|%UTRACE_SINGLESTEP will ensure
++ * it sees a %UTRACE_SIGNAL_HANDLER report.
++ */
++enum utrace_signal_action {
++ UTRACE_SIGNAL_DELIVER = 0x00,
++ UTRACE_SIGNAL_IGN = 0x10,
++ UTRACE_SIGNAL_TERM = 0x20,
++ UTRACE_SIGNAL_CORE = 0x30,
++ UTRACE_SIGNAL_STOP = 0x40,
++ UTRACE_SIGNAL_TSTP = 0x50,
++ UTRACE_SIGNAL_REPORT = 0x60,
++ UTRACE_SIGNAL_HANDLER = 0x70
++};
++#define UTRACE_SIGNAL_MASK 0xf0
++#define UTRACE_SIGNAL_HOLD 0x100 /* Flag, push signal back on queue. */
++
++/**
++ * utrace_signal_action - &enum utrace_signal_action from callback action
++ * @action: @report_signal callback @action argument or return value
++ *
++ * This extracts the &enum utrace_signal_action from @action, which
++ * is the @action argument to a @report_signal callback or the
++ * return value from one.
++ */
++static inline enum utrace_signal_action utrace_signal_action(u32 action)
++{
++ return action & UTRACE_SIGNAL_MASK;
++}
++
++/**
++ * enum utrace_syscall_action - disposition of system call attempt
++ * @UTRACE_SYSCALL_RUN: Run the system call.
++ * @UTRACE_SYSCALL_ABORT: Don't run the system call.
++ *
++ * This is encoded in the @action argument and the return value for
++ * a @report_syscall_entry callback.
++ */
++enum utrace_syscall_action {
++ UTRACE_SYSCALL_RUN = 0x00,
++ UTRACE_SYSCALL_ABORT = 0x10
++};
++#define UTRACE_SYSCALL_MASK 0xf0
++#define UTRACE_SYSCALL_RESUMED 0x100 /* Flag, report_syscall_entry() repeats */
++
++/**
++ * utrace_syscall_action - &enum utrace_syscall_action from callback action
++ * @action: @report_syscall_entry callback @action or return value
++ *
++ * This extracts the &enum utrace_syscall_action from @action, which
++ * is the @action argument to a @report_syscall_entry callback or the
++ * return value from one.
++ */
++static inline enum utrace_syscall_action utrace_syscall_action(u32 action)
++{
++ return action & UTRACE_SYSCALL_MASK;
++}
++
++/*
++ * Flags for utrace_attach_task() and utrace_attach_pid().
++ */
++#define UTRACE_ATTACH_MATCH_OPS 0x0001 /* Match engines on ops. */
++#define UTRACE_ATTACH_MATCH_DATA 0x0002 /* Match engines on data. */
++#define UTRACE_ATTACH_MATCH_MASK 0x000f
++#define UTRACE_ATTACH_CREATE 0x0010 /* Attach a new engine. */
++#define UTRACE_ATTACH_EXCLUSIVE 0x0020 /* Refuse if existing match. */
++
++/**
++ * struct utrace_engine - per-engine structure
++ * @ops: &struct utrace_engine_ops pointer passed to utrace_attach_task()
++ * @data: engine-private &void * passed to utrace_attach_task()
++ * @flags: event mask set by utrace_set_events() plus internal flag bits
++ *
++ * The task itself never has to worry about engines detaching while
++ * it's doing event callbacks. These structures are removed from the
++ * task's active list only when it's stopped, or by the task itself.
++ *
++ * utrace_engine_get() and utrace_engine_put() maintain a reference count.
++ * When it drops to zero, the structure is freed. One reference is held
++ * implicitly while the engine is attached to its task.
++ */
++struct utrace_engine {
++/* private: */
++ struct kref kref;
++ void (*release)(void *);
++ struct list_head entry;
++
++/* public: */
++ const struct utrace_engine_ops *ops;
++ void *data;
++
++ unsigned long flags;
++};
++
++/**
++ * utrace_engine_get - acquire a reference on a &struct utrace_engine
++ * @engine: &struct utrace_engine pointer
++ *
++ * You must hold a reference on @engine, and you get another.
++ */
++static inline void utrace_engine_get(struct utrace_engine *engine)
++{
++ kref_get(&engine->kref);
++}
++
++void __utrace_engine_release(struct kref *);
++
++/**
++ * utrace_engine_put - release a reference on a &struct utrace_engine
++ * @engine: &struct utrace_engine pointer
++ *
++ * You must hold a reference on @engine, and you lose that reference.
++ * If it was the last one, @engine becomes an invalid pointer.
++ */
++static inline void utrace_engine_put(struct utrace_engine *engine)
++{
++ kref_put(&engine->kref, __utrace_engine_release);
++}
++
++/**
++ * struct utrace_engine_ops - tracing engine callbacks
++ *
++ * Each @report_*() callback corresponds to an %UTRACE_EVENT(*) bit.
++ * utrace_set_events() calls on @engine choose which callbacks will
++ * be made to @engine from @task.
++ *
++ * Most callbacks take an @action argument, giving the resume action
++ * chosen by other tracing engines. All callbacks take an @engine
++ * argument. The @report_reap callback takes a @task argument that
++ * might or might not be @current. All other @report_* callbacks
++ * report an event in the @current task.
++ *
++ * For some calls, @action also includes bits specific to that event
++ * and utrace_resume_action() is used to extract the resume action.
++ * This shows what would happen if @engine wasn't there, or will if
++ * the callback's return value uses %UTRACE_RESUME. This always
++ * starts as %UTRACE_RESUME when no other tracing is being done on
++ * this task.
++ *
++ * All return values contain &enum utrace_resume_action bits. For
++ * some calls, other bits specific to that kind of event are added to
++ * the resume action bits with OR. These are the same bits used in
++ * the @action argument. The resume action returned by a callback
++ * does not override previous engines' choices, it only says what
++ * @engine wants done. What @current actually does is the action that's
++ * most constrained among the choices made by all attached engines.
++ * See utrace_control() for more information on the actions.
++ *
++ * When %UTRACE_STOP is used in @report_syscall_entry, then @current
++ * stops before attempting the system call. In this case, another
++ * @report_syscall_entry callback will follow after @current resumes if
++ * %UTRACE_REPORT or %UTRACE_INTERRUPT was returned by some callback
++ * or passed to utrace_control(). In a second or later callback,
++ * %UTRACE_SYSCALL_RESUMED is set in the @action argument to indicate
++ * a repeat callback still waiting to attempt the same system call
++ * invocation. This repeat callback gives each engine an opportunity
++ * to reexamine registers another engine might have changed while
++ * @current was held in %UTRACE_STOP.
++ *
++ * In other cases, the resume action does not take effect until @current
++ * is ready to check for signals and return to user mode. If there
++ * are more callbacks to be made, the last round of calls determines
++ * the final action. A @report_quiesce callback with @event zero, or
++ * a @report_signal callback, will always be the last one made before
++ * @current resumes. Only %UTRACE_STOP is "sticky"--if @engine returned
++ * %UTRACE_STOP then @current stays stopped unless @engine returns
++ * different from a following callback.
++ *
++ * The report_death() and report_reap() callbacks do not take @action
++ * arguments, and only %UTRACE_DETACH is meaningful in the return value
++ * from a report_death() callback. None of the resume actions applies
++ * to a dead thread.
++ *
++ * All @report_*() hooks are called with no locks held, in a generally
++ * safe environment when we will be returning to user mode soon (or just
++ * entered the kernel). It is fine to block for memory allocation and
++ * the like, but all hooks are asynchronous and must not block on
++ * external events! If you want the thread to block, use %UTRACE_STOP
++ * in your hook's return value; then later wake it up with utrace_control().
++ *
++ * @report_quiesce:
++ * Requested by %UTRACE_EVENT(%QUIESCE).
++ * This does not indicate any event, but just that @current is in a
++ * safe place for examination. This call is made before each specific
++ * event callback, except for @report_reap. The @event argument gives
++ * the %UTRACE_EVENT(@which) value for the event occurring. This
++ * callback might be made for events @engine has not requested, if
++ * some other engine is tracing the event; calling utrace_set_events()
++ * call here can request the immediate callback for this occurrence of
++ * @event. @event is zero when there is no other event, @current is
++ * now ready to check for signals and return to user mode, and some
++ * engine has used %UTRACE_REPORT or %UTRACE_INTERRUPT to request this
++ * callback. For this case, if @report_signal is not %NULL, the
++ * @report_quiesce callback may be replaced with a @report_signal
++ * callback passing %UTRACE_SIGNAL_REPORT in its @action argument,
++ * whenever @current is entering the signal-check path anyway.
++ *
++ * @report_signal:
++ * Requested by %UTRACE_EVENT(%SIGNAL_*) or %UTRACE_EVENT(%QUIESCE).
++ * Use utrace_signal_action() and utrace_resume_action() on @action.
++ * The signal action is %UTRACE_SIGNAL_REPORT when some engine has
++ * used %UTRACE_REPORT or %UTRACE_INTERRUPT; the callback can choose
++ * to stop or to deliver an artificial signal, before pending signals.
++ * It's %UTRACE_SIGNAL_HANDLER instead when signal handler setup just
++ * finished (after a previous %UTRACE_SIGNAL_DELIVER return); this
++ * serves in lieu of any %UTRACE_SIGNAL_REPORT callback requested by
++ * %UTRACE_REPORT or %UTRACE_INTERRUPT, and is also implicitly
++ * requested by %UTRACE_SINGLESTEP or %UTRACE_BLOCKSTEP into the
++ * signal delivery. The other signal actions indicate a signal about
++ * to be delivered; the previous engine's return value sets the signal
++ * action seen by the the following engine's callback. The @info data
++ * can be changed at will, including @info->si_signo. The settings in
++ * @return_ka determines what %UTRACE_SIGNAL_DELIVER does. @orig_ka
++ * is what was in force before other tracing engines intervened, and
++ * it's %NULL when this report began as %UTRACE_SIGNAL_REPORT or
++ * %UTRACE_SIGNAL_HANDLER. For a report without a new signal, @info
++ * is left uninitialized and must be set completely by an engine that
++ * chooses to deliver a signal; if there was a previous @report_signal
++ * callback ending in %UTRACE_STOP and it was just resumed using
++ * %UTRACE_REPORT or %UTRACE_INTERRUPT, then @info is left unchanged
++ * from the previous callback. In this way, the original signal can
++ * be left in @info while returning %UTRACE_STOP|%UTRACE_SIGNAL_IGN
++ * and then found again when resuming with %UTRACE_INTERRUPT.
++ * The %UTRACE_SIGNAL_HOLD flag bit can be OR'd into the return value,
++ * and might be in @action if the previous engine returned it. This
++ * flag asks that the signal in @info be pushed back on @current's queue
++ * so that it will be seen again after whatever action is taken now.
++ *
++ * @report_clone:
++ * Requested by %UTRACE_EVENT(%CLONE).
++ * Event reported for parent, before the new task @child might run.
++ * @clone_flags gives the flags used in the clone system call, or
++ * equivalent flags for a fork() or vfork() system call. This
++ * function can use utrace_attach_task() on @child. Then passing
++ * %UTRACE_STOP to utrace_control() on @child here keeps the child
++ * stopped before it ever runs in user mode, %UTRACE_REPORT or
++ * %UTRACE_INTERRUPT ensures a callback from @child before it
++ * starts in user mode.
++ *
++ * @report_jctl:
++ * Requested by %UTRACE_EVENT(%JCTL).
++ * Job control event; @type is %CLD_STOPPED or %CLD_CONTINUED,
++ * indicating whether we are stopping or resuming now. If @notify
++ * is nonzero, @current is the last thread to stop and so will send
++ * %SIGCHLD to its parent after this callback; @notify reflects
++ * what the parent's %SIGCHLD has in @si_code, which can sometimes
++ * be %CLD_STOPPED even when @type is %CLD_CONTINUED.
++ *
++ * @report_exec:
++ * Requested by %UTRACE_EVENT(%EXEC).
++ * An execve system call has succeeded and the new program is about to
++ * start running. The initial user register state is handy to be tweaked
++ * directly in @regs. @fmt and @bprm gives the details of this exec.
++ *
++ * @report_syscall_entry:
++ * Requested by %UTRACE_EVENT(%SYSCALL_ENTRY).
++ * Thread has entered the kernel to request a system call.
++ * The user register state is handy to be tweaked directly in @regs.
++ * The @action argument contains an &enum utrace_syscall_action,
++ * use utrace_syscall_action() to extract it. The return value
++ * overrides the last engine's action for the system call.
++ * If the final action is %UTRACE_SYSCALL_ABORT, no system call
++ * is made. The details of the system call being attempted can
++ * be fetched here with syscall_get_nr() and syscall_get_arguments().
++ * The parameter registers can be changed with syscall_set_arguments().
++ * See above about the %UTRACE_SYSCALL_RESUMED flag in @action.
++ * Use %UTRACE_REPORT in the return value to guarantee you get
++ * another callback (with %UTRACE_SYSCALL_RESUMED flag) in case
++ * @current stops with %UTRACE_STOP before attempting the system call.
++ *
++ * @report_syscall_exit:
++ * Requested by %UTRACE_EVENT(%SYSCALL_EXIT).
++ * Thread is about to leave the kernel after a system call request.
++ * The user register state is handy to be tweaked directly in @regs.
++ * The results of the system call attempt can be examined here using
++ * syscall_get_error() and syscall_get_return_value(). It is safe
++ * here to call syscall_set_return_value() or syscall_rollback().
++ *
++ * @report_exit:
++ * Requested by %UTRACE_EVENT(%EXIT).
++ * Thread is exiting and cannot be prevented from doing so,
++ * but all its state is still live. The @code value will be
++ * the wait result seen by the parent, and can be changed by
++ * this engine or others. The @orig_code value is the real
++ * status, not changed by any tracing engine. Returning %UTRACE_STOP
++ * here keeps @current stopped before it cleans up its state and dies,
++ * so it can be examined by other processes. When @current is allowed
++ * to run, it will die and get to the @report_death callback.
++ *
++ * @report_death:
++ * Requested by %UTRACE_EVENT(%DEATH).
++ * Thread is really dead now. It might be reaped by its parent at
++ * any time, or self-reap immediately. Though the actual reaping
++ * may happen in parallel, a report_reap() callback will always be
++ * ordered after a report_death() callback.
++ *
++ * @report_reap:
++ * Requested by %UTRACE_EVENT(%REAP).
++ * Called when someone reaps the dead task (parent, init, or self).
++ * This means the parent called wait, or else this was a detached
++ * thread or a process whose parent ignores SIGCHLD.
++ * No more callbacks are made after this one.
++ * The engine is always detached.
++ * There is nothing more a tracing engine can do about this thread.
++ * After this callback, the @engine pointer will become invalid.
++ * The @task pointer may become invalid if get_task_struct() hasn't
++ * been used to keep it alive.
++ * An engine should always request this callback if it stores the
++ * @engine pointer or stores any pointer in @engine->data, so it
++ * can clean up its data structures.
++ * Unlike other callbacks, this can be called from the parent's context
++ * rather than from the traced thread itself--it must not delay the
++ * parent by blocking.
++ *
++ * @release:
++ * If not %NULL, this is called after the last utrace_engine_put()
++ * call for a &struct utrace_engine, which could be implicit after
++ * a %UTRACE_DETACH return from another callback. Its argument is
++ * the engine's @data member.
++ */
++struct utrace_engine_ops {
++ u32 (*report_quiesce)(u32 action, struct utrace_engine *engine,
++ unsigned long event);
++ u32 (*report_signal)(u32 action, struct utrace_engine *engine,
++ struct pt_regs *regs,
++ siginfo_t *info,
++ const struct k_sigaction *orig_ka,
++ struct k_sigaction *return_ka);
++ u32 (*report_clone)(u32 action, struct utrace_engine *engine,
++ unsigned long clone_flags,
++ struct task_struct *child);
++ u32 (*report_jctl)(u32 action, struct utrace_engine *engine,
++ int type, int notify);
++ u32 (*report_exec)(u32 action, struct utrace_engine *engine,
++ const struct linux_binfmt *fmt,
++ const struct linux_binprm *bprm,
++ struct pt_regs *regs);
++ u32 (*report_syscall_entry)(u32 action, struct utrace_engine *engine,
++ struct pt_regs *regs);
++ u32 (*report_syscall_exit)(u32 action, struct utrace_engine *engine,
++ struct pt_regs *regs);
++ u32 (*report_exit)(u32 action, struct utrace_engine *engine,
++ long orig_code, long *code);
++ u32 (*report_death)(struct utrace_engine *engine,
++ bool group_dead, int signal);
++ void (*report_reap)(struct utrace_engine *engine,
++ struct task_struct *task);
++ void (*release)(void *data);
++};
++
++/**
++ * struct utrace_examiner - private state for using utrace_prepare_examine()
++ *
++ * The members of &struct utrace_examiner are private to the implementation.
++ * This data type holds the state from a call to utrace_prepare_examine()
++ * to be used by a call to utrace_finish_examine().
++ */
++struct utrace_examiner {
++/* private: */
++ long state;
++ unsigned long ncsw;
++};
++
++/*
++ * These are the exported entry points for tracing engines to use.
++ * See kernel/utrace.c for their kerneldoc comments with interface details.
++ */
++struct utrace_engine *utrace_attach_task(struct task_struct *, int,
++ const struct utrace_engine_ops *,
++ void *);
++struct utrace_engine *utrace_attach_pid(struct pid *, int,
++ const struct utrace_engine_ops *,
++ void *);
++int __must_check utrace_control(struct task_struct *,
++ struct utrace_engine *,
++ enum utrace_resume_action);
++int __must_check utrace_set_events(struct task_struct *,
++ struct utrace_engine *,
++ unsigned long eventmask);
++int __must_check utrace_barrier(struct task_struct *,
++ struct utrace_engine *);
++int __must_check utrace_prepare_examine(struct task_struct *,
++ struct utrace_engine *,
++ struct utrace_examiner *);
++int __must_check utrace_finish_examine(struct task_struct *,
++ struct utrace_engine *,
++ struct utrace_examiner *);
++
++/**
++ * utrace_control_pid - control a thread being traced by a tracing engine
++ * @pid: thread to affect
++ * @engine: attached engine to affect
++ * @action: &enum utrace_resume_action for thread to do
++ *
++ * This is the same as utrace_control(), but takes a &struct pid
++ * pointer rather than a &struct task_struct pointer. The caller must
++ * hold a ref on @pid, but does not need to worry about the task
++ * staying valid. If it's been reaped so that @pid points nowhere,
++ * then this call returns -%ESRCH.
++ */
++static inline __must_check int utrace_control_pid(
++ struct pid *pid, struct utrace_engine *engine,
++ enum utrace_resume_action action)
++{
++ /*
++ * We don't bother with rcu_read_lock() here to protect the
++ * task_struct pointer, because utrace_control will return
++ * -ESRCH without looking at that pointer if the engine is
++ * already detached. A task_struct pointer can't die before
++ * all the engines are detached in release_task() first.
++ */
++ struct task_struct *task = pid_task(pid, PIDTYPE_PID);
++ return unlikely(!task) ? -ESRCH : utrace_control(task, engine, action);
++}
++
++/**
++ * utrace_set_events_pid - choose which event reports a tracing engine gets
++ * @pid: thread to affect
++ * @engine: attached engine to affect
++ * @eventmask: new event mask
++ *
++ * This is the same as utrace_set_events(), but takes a &struct pid
++ * pointer rather than a &struct task_struct pointer. The caller must
++ * hold a ref on @pid, but does not need to worry about the task
++ * staying valid. If it's been reaped so that @pid points nowhere,
++ * then this call returns -%ESRCH.
++ */
++static inline __must_check int utrace_set_events_pid(
++ struct pid *pid, struct utrace_engine *engine, unsigned long eventmask)
++{
++ struct task_struct *task = pid_task(pid, PIDTYPE_PID);
++ return unlikely(!task) ? -ESRCH :
++ utrace_set_events(task, engine, eventmask);
++}
++
++/**
++ * utrace_barrier_pid - synchronize with simultaneous tracing callbacks
++ * @pid: thread to affect
++ * @engine: engine to affect (can be detached)
++ *
++ * This is the same as utrace_barrier(), but takes a &struct pid
++ * pointer rather than a &struct task_struct pointer. The caller must
++ * hold a ref on @pid, but does not need to worry about the task
++ * staying valid. If it's been reaped so that @pid points nowhere,
++ * then this call returns -%ESRCH.
++ */
++static inline __must_check int utrace_barrier_pid(struct pid *pid,
++ struct utrace_engine *engine)
++{
++ struct task_struct *task = pid_task(pid, PIDTYPE_PID);
++ return unlikely(!task) ? -ESRCH : utrace_barrier(task, engine);
++}
++
++#endif /* CONFIG_UTRACE */
++
++#endif /* linux/utrace.h */
+diff --git a/init/Kconfig b/init/Kconfig
+index 412c21b..a03ae51 100644
+--- a/init/Kconfig
++++ b/init/Kconfig
+@@ -372,6 +372,15 @@ config AUDIT_TREE
+ depends on AUDITSYSCALL
+ select FSNOTIFY
+
++config UTRACE
++ bool "Infrastructure for tracing and debugging user processes"
++ depends on EXPERIMENTAL
++ depends on HAVE_ARCH_TRACEHOOK
++ help
++ Enable the utrace process tracing interface. This is an internal
++ kernel interface exported to kernel modules, to track events in
++ user threads, extract and change user thread state.
++
+ source "kernel/irq/Kconfig"
+
+ menu "RCU Subsystem"
+diff --git a/kernel/Makefile b/kernel/Makefile
+index 2d64cfc..4a22e81 100644
+--- a/kernel/Makefile
++++ b/kernel/Makefile
+@@ -68,6 +68,7 @@ obj-$(CONFIG_IKCONFIG) += configs.o
+ obj-$(CONFIG_RESOURCE_COUNTERS) += res_counter.o
+ obj-$(CONFIG_SMP) += stop_machine.o
+ obj-$(CONFIG_KPROBES_SANITY_TEST) += test_kprobes.o
++obj-$(CONFIG_UTRACE) += utrace.o
+ obj-$(CONFIG_AUDIT) += audit.o auditfilter.o
+ obj-$(CONFIG_AUDITSYSCALL) += auditsc.o
+ obj-$(CONFIG_AUDIT_WATCH) += audit_watch.o
+diff --git a/kernel/fork.c b/kernel/fork.c
+index 0276c30..62caf3d 100644
+--- a/kernel/fork.c
++++ b/kernel/fork.c
+@@ -168,6 +168,7 @@ void free_task(struct task_struct *tsk)
+ free_thread_info(tsk->stack);
+ rt_mutex_debug_task_free(tsk);
+ ftrace_graph_exit_task(tsk);
++ tracehook_free_task(tsk);
+ free_task_struct(tsk);
+ }
+ EXPORT_SYMBOL(free_task);
+@@ -1095,6 +1096,8 @@ static struct task_struct *copy_process(unsigned long clone_flags,
+ if (!p)
+ goto fork_out;
+
++ tracehook_init_task(p);
++
+ ftrace_graph_init_task(p);
+
+ rt_mutex_init_task(p);
+diff --git a/kernel/utrace.c b/kernel/utrace.c
+new file mode 100644
+index 0000000..f332d65
+--- /dev/null
++++ b/kernel/utrace.c
+@@ -0,0 +1,2440 @@
++/*
++ * utrace infrastructure interface for debugging user processes
++ *
++ * Copyright (C) 2006-2010 Red Hat, Inc. All rights reserved.
++ *
++ * This copyrighted material is made available to anyone wishing to use,
++ * modify, copy, or redistribute it subject to the terms and conditions
++ * of the GNU General Public License v.2.
++ *
++ * Red Hat Author: Roland McGrath.
++ */
++
++#include <linux/utrace.h>
++#include <linux/tracehook.h>
++#include <linux/regset.h>
++#include <asm/syscall.h>
++#include <linux/ptrace.h>
++#include <linux/err.h>
++#include <linux/sched.h>
++#include <linux/freezer.h>
++#include <linux/module.h>
++#include <linux/init.h>
++#include <linux/slab.h>
++#include <linux/seq_file.h>
++
++
++/*
++ * Per-thread structure private to utrace implementation.
++ * If task_struct.utrace_flags is nonzero, task_struct.utrace
++ * has always been allocated first. Once allocated, it is
++ * never freed until free_task().
++ *
++ * The common event reporting loops are done by the task making the
++ * report without ever taking any locks. To facilitate this, the two
++ * lists @attached and @attaching work together for smooth asynchronous
++ * attaching with low overhead. Modifying either list requires @lock.
++ * The @attaching list can be modified any time while holding @lock.
++ * New engines being attached always go on this list.
++ *
++ * The @attached list is what the task itself uses for its reporting
++ * loops. When the task itself is not quiescent, it can use the
++ * @attached list without taking any lock. Nobody may modify the list
++ * when the task is not quiescent. When it is quiescent, that means
++ * that it won't run again without taking @lock itself before using
++ * the list.
++ *
++ * At each place where we know the task is quiescent (or it's current),
++ * while holding @lock, we call splice_attaching(), below. This moves
++ * the @attaching list members on to the end of the @attached list.
++ * Since this happens at the start of any reporting pass, any new
++ * engines attached asynchronously go on the stable @attached list
++ * in time to have their callbacks seen.
++ */
++struct utrace {
++ spinlock_t lock;
++ struct list_head attached, attaching;
++
++ struct task_struct *cloning;
++
++ struct utrace_engine *reporting;
++
++ enum utrace_resume_action resume:UTRACE_RESUME_BITS;
++ unsigned int signal_handler:1;
++ unsigned int vfork_stop:1; /* need utrace_stop() before vfork wait */
++ unsigned int death:1; /* in utrace_report_death() now */
++ unsigned int reap:1; /* release_task() has run */
++ unsigned int pending_attach:1; /* need splice_attaching() */
++};
++
++static struct kmem_cache *utrace_cachep;
++static struct kmem_cache *utrace_engine_cachep;
++static const struct utrace_engine_ops utrace_detached_ops; /* forward decl */
++
++static int __init utrace_init(void)
++{
++ utrace_cachep = KMEM_CACHE(utrace, SLAB_PANIC);
++ utrace_engine_cachep = KMEM_CACHE(utrace_engine, SLAB_PANIC);
++ return 0;
++}
++module_init(utrace_init);
++
++/*
++ * Set up @task.utrace for the first time. We can have races
++ * between two utrace_attach_task() calls here. The task_lock()
++ * governs installing the new pointer. If another one got in first,
++ * we just punt the new one we allocated.
++ *
++ * This returns false only in case of a memory allocation failure.
++ */
++static bool utrace_task_alloc(struct task_struct *task)
++{
++ struct utrace *utrace = kmem_cache_zalloc(utrace_cachep, GFP_KERNEL);
++ if (unlikely(!utrace))
++ return false;
++ spin_lock_init(&utrace->lock);
++ INIT_LIST_HEAD(&utrace->attached);
++ INIT_LIST_HEAD(&utrace->attaching);
++ utrace->resume = UTRACE_RESUME;
++ task_lock(task);
++ if (likely(!task->utrace)) {
++ /*
++ * This barrier makes sure the initialization of the struct
++ * precedes the installation of the pointer. This pairs
++ * with smp_read_barrier_depends() in task_utrace_struct().
++ */
++ smp_wmb();
++ task->utrace = utrace;
++ }
++ task_unlock(task);
++
++ if (unlikely(task->utrace != utrace))
++ kmem_cache_free(utrace_cachep, utrace);
++ return true;
++}
++
++/*
++ * This is called via tracehook_free_task() from free_task()
++ * when @task is being deallocated.
++ */
++void utrace_free_task(struct task_struct *task)
++{
++ kmem_cache_free(utrace_cachep, task->utrace);
++}
++
++/*
++ * This is calledwhen the task is safely quiescent, i.e. it won't consult
++ * utrace->attached without the lock. Move any engines attached
++ * asynchronously from @utrace->attaching onto the @utrace->attached list.
++ */
++static void splice_attaching(struct utrace *utrace)
++{
++ lockdep_assert_held(&utrace->lock);
++ list_splice_tail_init(&utrace->attaching, &utrace->attached);
++ utrace->pending_attach = 0;
++}
++
++/*
++ * This is the exported function used by the utrace_engine_put() inline.
++ */
++void __utrace_engine_release(struct kref *kref)
++{
++ struct utrace_engine *engine = container_of(kref, struct utrace_engine,
++ kref);
++ BUG_ON(!list_empty(&engine->entry));
++ if (engine->release)
++ (*engine->release)(engine->data);
++ kmem_cache_free(utrace_engine_cachep, engine);
++}
++EXPORT_SYMBOL_GPL(__utrace_engine_release);
++
++static bool engine_matches(struct utrace_engine *engine, int flags,
++ const struct utrace_engine_ops *ops, void *data)
++{
++ if ((flags & UTRACE_ATTACH_MATCH_OPS) && engine->ops != ops)
++ return false;
++ if ((flags & UTRACE_ATTACH_MATCH_DATA) && engine->data != data)
++ return false;
++ return engine->ops && engine->ops != &utrace_detached_ops;
++}
++
++static struct utrace_engine *find_matching_engine(
++ struct utrace *utrace, int flags,
++ const struct utrace_engine_ops *ops, void *data)
++{
++ struct utrace_engine *engine;
++ list_for_each_entry(engine, &utrace->attached, entry)
++ if (engine_matches(engine, flags, ops, data))
++ return engine;
++ list_for_each_entry(engine, &utrace->attaching, entry)
++ if (engine_matches(engine, flags, ops, data))
++ return engine;
++ return NULL;
++}
++
++/*
++ * Enqueue @engine, or maybe don't if UTRACE_ATTACH_EXCLUSIVE.
++ */
++static int utrace_add_engine(struct task_struct *target,
++ struct utrace *utrace,
++ struct utrace_engine *engine,
++ int flags,
++ const struct utrace_engine_ops *ops,
++ void *data)
++{
++ int ret;
++
++ spin_lock(&utrace->lock);
++
++ ret = -EEXIST;
++ if ((flags & UTRACE_ATTACH_EXCLUSIVE) &&
++ unlikely(find_matching_engine(utrace, flags, ops, data)))
++ goto unlock;
++
++ /*
++ * In case we had no engines before, make sure that
++ * utrace_flags is not zero. Since we did unlock+lock
++ * at least once after utrace_task_alloc() installed
++ * ->utrace, we have the necessary barrier which pairs
++ * with rmb() in task_utrace_struct().
++ */
++ ret = -ESRCH;
++ if (!target->utrace_flags) {
++ target->utrace_flags = UTRACE_EVENT(REAP);
++ /*
++ * If we race with tracehook_prepare_release_task()
++ * make sure that either it sees utrace_flags != 0
++ * or we see exit_state == EXIT_DEAD.
++ */
++ smp_mb();
++ if (unlikely(target->exit_state == EXIT_DEAD)) {
++ target->utrace_flags = 0;
++ goto unlock;
++ }
++ }
++
++ /*
++ * Put the new engine on the pending ->attaching list.
++ * Make sure it gets onto the ->attached list by the next
++ * time it's examined. Setting ->pending_attach ensures
++ * that start_report() takes the lock and splices the lists
++ * before the next new reporting pass.
++ *
++ * When target == current, it would be safe just to call
++ * splice_attaching() right here. But if we're inside a
++ * callback, that would mean the new engine also gets
++ * notified about the event that precipitated its own
++ * creation. This is not what the user wants.
++ */
++ list_add_tail(&engine->entry, &utrace->attaching);
++ utrace->pending_attach = 1;
++ utrace_engine_get(engine);
++ ret = 0;
++unlock:
++ spin_unlock(&utrace->lock);
++
++ return ret;
++}
++
++/**
++ * utrace_attach_task - attach new engine, or look up an attached engine
++ * @target: thread to attach to
++ * @flags: flag bits combined with OR, see below
++ * @ops: callback table for new engine
++ * @data: engine private data pointer
++ *
++ * The caller must ensure that the @target thread does not get freed,
++ * i.e. hold a ref or be its parent. It is always safe to call this
++ * on @current, or on the @child pointer in a @report_clone callback.
++ * For most other cases, it's easier to use utrace_attach_pid() instead.
++ *
++ * UTRACE_ATTACH_CREATE:
++ * Create a new engine. If %UTRACE_ATTACH_CREATE is not specified, you
++ * only look up an existing engine already attached to the thread.
++ *
++ * UTRACE_ATTACH_EXCLUSIVE:
++ * Attempting to attach a second (matching) engine fails with -%EEXIST.
++ *
++ * UTRACE_ATTACH_MATCH_OPS: Only consider engines matching @ops.
++ * UTRACE_ATTACH_MATCH_DATA: Only consider engines matching @data.
++ *
++ * Calls with neither %UTRACE_ATTACH_MATCH_OPS nor %UTRACE_ATTACH_MATCH_DATA
++ * match the first among any engines attached to @target. That means that
++ * %UTRACE_ATTACH_EXCLUSIVE in such a call fails with -%EEXIST if there
++ * are any engines on @target at all.
++ */
++struct utrace_engine *utrace_attach_task(
++ struct task_struct *target, int flags,
++ const struct utrace_engine_ops *ops, void *data)
++{
++ struct utrace *utrace = task_utrace_struct(target);
++ struct utrace_engine *engine;
++ int ret;
++
++ if (!(flags & UTRACE_ATTACH_CREATE)) {
++ if (unlikely(!utrace))
++ return ERR_PTR(-ENOENT);
++ spin_lock(&utrace->lock);
++ engine = find_matching_engine(utrace, flags, ops, data);
++ if (engine)
++ utrace_engine_get(engine);
++ spin_unlock(&utrace->lock);
++ return engine ?: ERR_PTR(-ENOENT);
++ }
++
++ if (unlikely(!ops) || unlikely(ops == &utrace_detached_ops))
++ return ERR_PTR(-EINVAL);
++
++ if (unlikely(target->flags & PF_KTHREAD))
++ /*
++ * Silly kernel, utrace is for users!
++ */
++ return ERR_PTR(-EPERM);
++
++ if (!utrace) {
++ if (unlikely(!utrace_task_alloc(target)))
++ return ERR_PTR(-ENOMEM);
++ utrace = task_utrace_struct(target);
++ }
++
++ engine = kmem_cache_alloc(utrace_engine_cachep, GFP_KERNEL);
++ if (unlikely(!engine))
++ return ERR_PTR(-ENOMEM);
++
++ /*
++ * Initialize the new engine structure. It starts out with one ref
++ * to return. utrace_add_engine() adds another for being attached.
++ */
++ kref_init(&engine->kref);
++ engine->flags = 0;
++ engine->ops = ops;
++ engine->data = data;
++ engine->release = ops->release;
++
++ ret = utrace_add_engine(target, utrace, engine, flags, ops, data);
++
++ if (unlikely(ret)) {
++ kmem_cache_free(utrace_engine_cachep, engine);
++ engine = ERR_PTR(ret);
++ }
++
++
++ return engine;
++}
++EXPORT_SYMBOL_GPL(utrace_attach_task);
++
++/**
++ * utrace_attach_pid - attach new engine, or look up an attached engine
++ * @pid: &struct pid pointer representing thread to attach to
++ * @flags: flag bits combined with OR, see utrace_attach_task()
++ * @ops: callback table for new engine
++ * @data: engine private data pointer
++ *
++ * This is the same as utrace_attach_task(), but takes a &struct pid
++ * pointer rather than a &struct task_struct pointer. The caller must
++ * hold a ref on @pid, but does not need to worry about the task
++ * staying valid. If it's been reaped so that @pid points nowhere,
++ * then this call returns -%ESRCH.
++ */
++struct utrace_engine *utrace_attach_pid(
++ struct pid *pid, int flags,
++ const struct utrace_engine_ops *ops, void *data)
++{
++ struct utrace_engine *engine = ERR_PTR(-ESRCH);
++ struct task_struct *task = get_pid_task(pid, PIDTYPE_PID);
++ if (task) {
++ engine = utrace_attach_task(task, flags, ops, data);
++ put_task_struct(task);
++ }
++ return engine;
++}
++EXPORT_SYMBOL_GPL(utrace_attach_pid);
++
++/*
++ * When an engine is detached, the target thread may still see it and
++ * make callbacks until it quiesces. We install a special ops vector
++ * with these two callbacks. When the target thread quiesces, it can
++ * safely free the engine itself. For any event we will always get
++ * the report_quiesce() callback first, so we only need this one
++ * pointer to be set. The only exception is report_reap(), so we
++ * supply that callback too.
++ */
++static u32 utrace_detached_quiesce(u32 action, struct utrace_engine *engine,
++ unsigned long event)
++{
++ return UTRACE_DETACH;
++}
++
++static void utrace_detached_reap(struct utrace_engine *engine,
++ struct task_struct *task)
++{
++}
++
++static const struct utrace_engine_ops utrace_detached_ops = {
++ .report_quiesce = &utrace_detached_quiesce,
++ .report_reap = &utrace_detached_reap
++};
++
++/*
++ * The caller has to hold a ref on the engine. If the attached flag is
++ * true (all but utrace_barrier() calls), the engine is supposed to be
++ * attached. If the attached flag is false (utrace_barrier() only),
++ * then return -ERESTARTSYS for an engine marked for detach but not yet
++ * fully detached. The task pointer can be invalid if the engine is
++ * detached.
++ *
++ * Get the utrace lock for the target task.
++ * Returns the struct if locked, or ERR_PTR(-errno).
++ *
++ * This has to be robust against races with:
++ * utrace_control(target, UTRACE_DETACH) calls
++ * UTRACE_DETACH after reports
++ * utrace_report_death
++ * utrace_release_task
++ */
++static struct utrace *get_utrace_lock(struct task_struct *target,
++ struct utrace_engine *engine,
++ bool attached)
++ __acquires(utrace->lock)
++{
++ struct utrace *utrace;
++
++ rcu_read_lock();
++
++ /*
++ * If this engine was already detached, bail out before we look at
++ * the task_struct pointer at all. If it's detached after this
++ * check, then RCU is still keeping this task_struct pointer valid.
++ *
++ * The ops pointer is NULL when the engine is fully detached.
++ * It's &utrace_detached_ops when it's marked detached but still
++ * on the list. In the latter case, utrace_barrier() still works,
++ * since the target might be in the middle of an old callback.
++ */
++ if (unlikely(!engine->ops)) {
++ rcu_read_unlock();
++ return ERR_PTR(-ESRCH);
++ }
++
++ if (unlikely(engine->ops == &utrace_detached_ops)) {
++ rcu_read_unlock();
++ return attached ? ERR_PTR(-ESRCH) : ERR_PTR(-ERESTARTSYS);
++ }
++
++ utrace = task_utrace_struct(target);
++ spin_lock(&utrace->lock);
++ if (unlikely(utrace->reap) || unlikely(!engine->ops) ||
++ unlikely(engine->ops == &utrace_detached_ops)) {
++ /*
++ * By the time we got the utrace lock,
++ * it had been reaped or detached already.
++ */
++ spin_unlock(&utrace->lock);
++ utrace = ERR_PTR(-ESRCH);
++ if (!attached && engine->ops == &utrace_detached_ops)
++ utrace = ERR_PTR(-ERESTARTSYS);
++ }
++ rcu_read_unlock();
++
++ return utrace;
++}
++
++/*
++ * Now that we don't hold any locks, run through any
++ * detached engines and free their references. Each
++ * engine had one implicit ref while it was attached.
++ */
++static void put_detached_list(struct list_head *list)
++{
++ struct utrace_engine *engine, *next;
++ list_for_each_entry_safe(engine, next, list, entry) {
++ list_del_init(&engine->entry);
++ utrace_engine_put(engine);
++ }
++}
++
++/*
++ * We use an extra bit in utrace_engine.flags past the event bits,
++ * to record whether the engine is keeping the target thread stopped.
++ *
++ * This bit is set in task_struct.utrace_flags whenever it is set in any
++ * engine's flags. Only utrace_reset() resets it in utrace_flags.
++ */
++#define ENGINE_STOP (1UL << _UTRACE_NEVENTS)
++
++static void mark_engine_wants_stop(struct task_struct *task,
++ struct utrace_engine *engine)
++{
++ engine->flags |= ENGINE_STOP;
++ task->utrace_flags |= ENGINE_STOP;
++}
++
++static void clear_engine_wants_stop(struct utrace_engine *engine)
++{
++ engine->flags &= ~ENGINE_STOP;
++}
++
++static bool engine_wants_stop(struct utrace_engine *engine)
++{
++ return (engine->flags & ENGINE_STOP) != 0;
++}
++
++/**
++ * utrace_set_events - choose which event reports a tracing engine gets
++ * @target: thread to affect
++ * @engine: attached engine to affect
++ * @events: new event mask
++ *
++ * This changes the set of events for which @engine wants callbacks made.
++ *
++ * This fails with -%EALREADY and does nothing if you try to clear
++ * %UTRACE_EVENT(%DEATH) when the @report_death callback may already have
++ * begun, or if you try to newly set %UTRACE_EVENT(%DEATH) or
++ * %UTRACE_EVENT(%QUIESCE) when @target is already dead or dying.
++ *
++ * This fails with -%ESRCH if you try to clear %UTRACE_EVENT(%REAP) when
++ * the @report_reap callback may already have begun, or when @target has
++ * already been detached, including forcible detach on reaping.
++ *
++ * If @target was stopped before the call, then after a successful call,
++ * no event callbacks not requested in @events will be made; if
++ * %UTRACE_EVENT(%QUIESCE) is included in @events, then a
++ * @report_quiesce callback will be made when @target resumes.
++ *
++ * If @target was not stopped and @events excludes some bits that were
++ * set before, this can return -%EINPROGRESS to indicate that @target
++ * may have been making some callback to @engine. When this returns
++ * zero, you can be sure that no event callbacks you've disabled in
++ * @events can be made. If @events only sets new bits that were not set
++ * before on @engine, then -%EINPROGRESS will never be returned.
++ *
++ * To synchronize after an -%EINPROGRESS return, see utrace_barrier().
++ *
++ * When @target is @current, -%EINPROGRESS is not returned. But note
++ * that a newly-created engine will not receive any callbacks related to
++ * an event notification already in progress. This call enables @events
++ * callbacks to be made as soon as @engine becomes eligible for any
++ * callbacks, see utrace_attach_task().
++ *
++ * These rules provide for coherent synchronization based on %UTRACE_STOP,
++ * even when %SIGKILL is breaking its normal simple rules.
++ */
++int utrace_set_events(struct task_struct *target,
++ struct utrace_engine *engine,
++ unsigned long events)
++{
++ struct utrace *utrace;
++ unsigned long old_flags, old_utrace_flags;
++ int ret = -EALREADY;
++
++ /*
++ * We just ignore the internal bit, so callers can use
++ * engine->flags to seed bitwise ops for our argument.
++ */
++ events &= ~ENGINE_STOP;
++
++ utrace = get_utrace_lock(target, engine, true);
++ if (unlikely(IS_ERR(utrace)))
++ return PTR_ERR(utrace);
++
++ old_utrace_flags = target->utrace_flags;
++ old_flags = engine->flags & ~ENGINE_STOP;
++
++ /*
++ * If utrace_report_death() is already progress now,
++ * it's too late to clear the death event bits.
++ */
++ if (((old_flags & ~events) & _UTRACE_DEATH_EVENTS) && utrace->death)
++ goto unlock;
++
++ /*
++ * When setting these flags, it's essential that we really
++ * synchronize with exit_notify(). They cannot be set after
++ * exit_notify() takes the tasklist_lock. By holding the read
++ * lock here while setting the flags, we ensure that the calls
++ * to tracehook_notify_death() and tracehook_report_death() will
++ * see the new flags. This ensures that utrace_release_task()
++ * knows positively that utrace_report_death() will be called or
++ * that it won't.
++ */
++ if ((events & ~old_flags) & _UTRACE_DEATH_EVENTS) {
++ read_lock(&tasklist_lock);
++ if (unlikely(target->exit_state)) {
++ read_unlock(&tasklist_lock);
++ goto unlock;
++ }
++ target->utrace_flags |= events;
++ read_unlock(&tasklist_lock);
++ }
++
++ engine->flags = events | (engine->flags & ENGINE_STOP);
++ target->utrace_flags |= events;
++
++ if ((events & UTRACE_EVENT_SYSCALL) &&
++ !(old_utrace_flags & UTRACE_EVENT_SYSCALL))
++ set_tsk_thread_flag(target, TIF_SYSCALL_TRACE);
++
++ ret = 0;
++ if ((old_flags & ~events) && target != current &&
++ !task_is_stopped_or_traced(target) && !target->exit_state) {
++ /*
++ * This barrier ensures that our engine->flags changes
++ * have hit before we examine utrace->reporting,
++ * pairing with the barrier in start_callback(). If
++ * @target has not yet hit finish_callback() to clear
++ * utrace->reporting, we might be in the middle of a
++ * callback to @engine.
++ */
++ smp_mb();
++ if (utrace->reporting == engine)
++ ret = -EINPROGRESS;
++ }
++unlock:
++ spin_unlock(&utrace->lock);
++
++ return ret;
++}
++EXPORT_SYMBOL_GPL(utrace_set_events);
++
++/*
++ * Asynchronously mark an engine as being detached.
++ *
++ * This must work while the target thread races with us doing
++ * start_callback(), defined below. It uses smp_rmb() between checking
++ * @engine->flags and using @engine->ops. Here we change @engine->ops
++ * first, then use smp_wmb() before changing @engine->flags. This ensures
++ * it can check the old flags before using the old ops, or check the old
++ * flags before using the new ops, or check the new flags before using the
++ * new ops, but can never check the new flags before using the old ops.
++ * Hence, utrace_detached_ops might be used with any old flags in place.
++ * It has report_quiesce() and report_reap() callbacks to handle all cases.
++ */
++static void mark_engine_detached(struct utrace_engine *engine)
++{
++ engine->ops = &utrace_detached_ops;
++ smp_wmb();
++ engine->flags = UTRACE_EVENT(QUIESCE);
++}
++
++/*
++ * Get @target to stop and return true if it is already stopped now.
++ * If we return false, it will make some event callback soonish.
++ * Called with @utrace locked.
++ */
++static bool utrace_do_stop(struct task_struct *target, struct utrace *utrace)
++{
++ if (task_is_stopped(target)) {
++ /*
++ * Stopped is considered quiescent; when it wakes up, it will
++ * go through utrace_finish_stop() before doing anything else.
++ */
++ spin_lock_irq(&target->sighand->siglock);
++ if (likely(task_is_stopped(target)))
++ __set_task_state(target, TASK_TRACED);
++ spin_unlock_irq(&target->sighand->siglock);
++ } else if (utrace->resume > UTRACE_REPORT) {
++ utrace->resume = UTRACE_REPORT;
++ set_notify_resume(target);
++ }
++
++ return task_is_traced(target);
++}
++
++/*
++ * If the target is not dead it should not be in tracing
++ * stop any more. Wake it unless it's in job control stop.
++ */
++static void utrace_wakeup(struct task_struct *target, struct utrace *utrace)
++{
++ lockdep_assert_held(&utrace->lock);
++ spin_lock_irq(&target->sighand->siglock);
++ if (target->signal->flags & SIGNAL_STOP_STOPPED ||
++ target->signal->group_stop_count)
++ target->state = TASK_STOPPED;
++ else
++ wake_up_state(target, __TASK_TRACED);
++ spin_unlock_irq(&target->sighand->siglock);
++}
++
++/*
++ * This is called when there might be some detached engines on the list or
++ * some stale bits in @task->utrace_flags. Clean them up and recompute the
++ * flags. Returns true if we're now fully detached.
++ *
++ * Called with @utrace->lock held, returns with it released.
++ * After this returns, @utrace might be freed if everything detached.
++ */
++static bool utrace_reset(struct task_struct *task, struct utrace *utrace)
++ __releases(utrace->lock)
++{
++ struct utrace_engine *engine, *next;
++ unsigned long flags = 0;
++ LIST_HEAD(detached);
++
++ splice_attaching(utrace);
++
++ /*
++ * Update the set of events of interest from the union
++ * of the interests of the remaining tracing engines.
++ * For any engine marked detached, remove it from the list.
++ * We'll collect them on the detached list.
++ */
++ list_for_each_entry_safe(engine, next, &utrace->attached, entry) {
++ if (engine->ops == &utrace_detached_ops) {
++ engine->ops = NULL;
++ list_move(&engine->entry, &detached);
++ } else {
++ flags |= engine->flags | UTRACE_EVENT(REAP);
++ }
++ }
++
++ if (task->exit_state) {
++ /*
++ * Once it's already dead, we never install any flags
++ * except REAP. When ->exit_state is set and events
++ * like DEATH are not set, then they never can be set.
++ * This ensures that utrace_release_task() knows
++ * positively that utrace_report_death() can never run.
++ */
++ BUG_ON(utrace->death);
++ flags &= UTRACE_EVENT(REAP);
++ } else if (!(flags & UTRACE_EVENT_SYSCALL) &&
++ test_tsk_thread_flag(task, TIF_SYSCALL_TRACE)) {
++ clear_tsk_thread_flag(task, TIF_SYSCALL_TRACE);
++ }
++
++ if (!flags) {
++ /*
++ * No more engines, cleared out the utrace.
++ */
++ utrace->resume = UTRACE_RESUME;
++ utrace->signal_handler = 0;
++ }
++
++ /*
++ * If no more engines want it stopped, wake it up.
++ */
++ if (task_is_traced(task) && !(flags & ENGINE_STOP)) {
++ /*
++ * It just resumes, so make sure single-step
++ * is not left set.
++ */
++ if (utrace->resume == UTRACE_RESUME)
++ user_disable_single_step(task);
++ utrace_wakeup(task, utrace);
++ }
++
++ /*
++ * In theory spin_lock() doesn't imply rcu_read_lock().
++ * Once we clear ->utrace_flags this task_struct can go away
++ * because tracehook_prepare_release_task() path does not take
++ * utrace->lock when ->utrace_flags == 0.
++ */
++ rcu_read_lock();
++ task->utrace_flags = flags;
++ spin_unlock(&utrace->lock);
++ rcu_read_unlock();
++
++ put_detached_list(&detached);
++
++ return !flags;
++}
++
++void utrace_finish_stop(void)
++{
++ /*
++ * If we were task_is_traced() and then SIGKILL'ed, make
++ * sure we do nothing until the tracer drops utrace->lock.
++ */
++ if (unlikely(__fatal_signal_pending(current))) {
++ struct utrace *utrace = task_utrace_struct(current);
++ spin_unlock_wait(&utrace->lock);
++ }
++}
++
++/*
++ * Perform %UTRACE_STOP, i.e. block in TASK_TRACED until woken up.
++ * @task == current, @utrace == current->utrace, which is not locked.
++ * Return true if we were woken up by SIGKILL even though some utrace
++ * engine may still want us to stay stopped.
++ */
++static void utrace_stop(struct task_struct *task, struct utrace *utrace,
++ enum utrace_resume_action action)
++{
++relock:
++ spin_lock(&utrace->lock);
++
++ if (action < utrace->resume) {
++ /*
++ * Ensure a reporting pass when we're resumed.
++ */
++ utrace->resume = action;
++ if (action == UTRACE_INTERRUPT)
++ set_thread_flag(TIF_SIGPENDING);
++ else
++ set_thread_flag(TIF_NOTIFY_RESUME);
++ }
++
++ /*
++ * If the ENGINE_STOP bit is clear in utrace_flags, that means
++ * utrace_reset() ran after we processed some UTRACE_STOP return
++ * values from callbacks to get here. If all engines have detached
++ * or resumed us, we don't stop. This check doesn't require
++ * siglock, but it should follow the interrupt/report bookkeeping
++ * steps (this can matter for UTRACE_RESUME but not UTRACE_DETACH).
++ */
++ if (unlikely(!(task->utrace_flags & ENGINE_STOP))) {
++ utrace_reset(task, utrace);
++ if (task->utrace_flags & ENGINE_STOP)
++ goto relock;
++ return;
++ }
++
++ /*
++ * The siglock protects us against signals. As well as SIGKILL
++ * waking us up, we must synchronize with the signal bookkeeping
++ * for stop signals and SIGCONT.
++ */
++ spin_lock_irq(&task->sighand->siglock);
++
++ if (unlikely(__fatal_signal_pending(task))) {
++ spin_unlock_irq(&task->sighand->siglock);
++ spin_unlock(&utrace->lock);
++ return;
++ }
++
++ __set_current_state(TASK_TRACED);
++
++ /*
++ * If there is a group stop in progress,
++ * we must participate in the bookkeeping.
++ */
++ if (unlikely(task->signal->group_stop_count) &&
++ !--task->signal->group_stop_count)
++ task->signal->flags = SIGNAL_STOP_STOPPED;
++
++ spin_unlock_irq(&task->sighand->siglock);
++ spin_unlock(&utrace->lock);
++
++ schedule();
++
++ utrace_finish_stop();
++
++ /*
++ * While in TASK_TRACED, we were considered "frozen enough".
++ * Now that we woke up, it's crucial if we're supposed to be
++ * frozen that we freeze now before running anything substantial.
++ */
++ try_to_freeze();
++
++ /*
++ * While we were in TASK_TRACED, complete_signal() considered
++ * us "uninterested" in signal wakeups. Now make sure our
++ * TIF_SIGPENDING state is correct for normal running.
++ */
++ spin_lock_irq(&task->sighand->siglock);
++ recalc_sigpending();
++ spin_unlock_irq(&task->sighand->siglock);
++}
++
++/*
++ * Called by release_task() with @reap set to true.
++ * Called by utrace_report_death() with @reap set to false.
++ * On reap, make report_reap callbacks and clean out @utrace
++ * unless still making callbacks. On death, update bookkeeping
++ * and handle the reap work if release_task() came in first.
++ */
++void utrace_maybe_reap(struct task_struct *target, struct utrace *utrace,
++ bool reap)
++{
++ struct utrace_engine *engine, *next;
++ struct list_head attached;
++
++ spin_lock(&utrace->lock);
++
++ if (reap) {
++ /*
++ * If the target will do some final callbacks but hasn't
++ * finished them yet, we know because it clears these event
++ * bits after it's done. Instead of cleaning up here and
++ * requiring utrace_report_death() to cope with it, we
++ * delay the REAP report and the teardown until after the
++ * target finishes its death reports.
++ */
++ utrace->reap = 1;
++
++ if (target->utrace_flags & _UTRACE_DEATH_EVENTS) {
++ spin_unlock(&utrace->lock);
++ return;
++ }
++ } else {
++ /*
++ * After we unlock with this flag clear, any competing
++ * utrace_control/utrace_set_events calls know that we've
++ * finished our callbacks and any detach bookkeeping.
++ */
++ utrace->death = 0;
++
++ if (!utrace->reap) {
++ /*
++ * We're just dead, not reaped yet. This will
++ * reset @target->utrace_flags so the later call
++ * with @reap set won't hit the check above.
++ */
++ utrace_reset(target, utrace);
++ return;
++ }
++ }
++
++ /*
++ * utrace_add_engine() checks ->utrace_flags != 0. Since
++ * @utrace->reap is set, nobody can set or clear UTRACE_EVENT(REAP)
++ * in @engine->flags or change @engine->ops and nobody can change
++ * @utrace->attached after we drop the lock.
++ */
++ target->utrace_flags = 0;
++
++ /*
++ * We clear out @utrace->attached before we drop the lock so
++ * that find_matching_engine() can't come across any old engine
++ * while we are busy tearing it down.
++ */
++ list_replace_init(&utrace->attached, &attached);
++ list_splice_tail_init(&utrace->attaching, &attached);
++
++ spin_unlock(&utrace->lock);
++
++ list_for_each_entry_safe(engine, next, &attached, entry) {
++ if (engine->flags & UTRACE_EVENT(REAP))
++ engine->ops->report_reap(engine, target);
++
++ engine->ops = NULL;
++ engine->flags = 0;
++ list_del_init(&engine->entry);
++
++ utrace_engine_put(engine);
++ }
++}
++
++/*
++ * You can't do anything to a dead task but detach it.
++ * If release_task() has been called, you can't do that.
++ *
++ * On the exit path, DEATH and QUIESCE event bits are set only
++ * before utrace_report_death() has taken the lock. At that point,
++ * the death report will come soon, so disallow detach until it's
++ * done. This prevents us from racing with it detaching itself.
++ *
++ * Called only when @target->exit_state is nonzero.
++ */
++static inline int utrace_control_dead(struct task_struct *target,
++ struct utrace *utrace,
++ enum utrace_resume_action action)
++{
++ lockdep_assert_held(&utrace->lock);
++
++ if (action != UTRACE_DETACH || unlikely(utrace->reap))
++ return -ESRCH;
++
++ if (unlikely(utrace->death))
++ /*
++ * We have already started the death report. We can't
++ * prevent the report_death and report_reap callbacks,
++ * so tell the caller they will happen.
++ */
++ return -EALREADY;
++
++ return 0;
++}
++
++/**
++ * utrace_control - control a thread being traced by a tracing engine
++ * @target: thread to affect
++ * @engine: attached engine to affect
++ * @action: &enum utrace_resume_action for thread to do
++ *
++ * This is how a tracing engine asks a traced thread to do something.
++ * This call is controlled by the @action argument, which has the
++ * same meaning as the &enum utrace_resume_action value returned by
++ * event reporting callbacks.
++ *
++ * If @target is already dead (@target->exit_state nonzero),
++ * all actions except %UTRACE_DETACH fail with -%ESRCH.
++ *
++ * The following sections describe each option for the @action argument.
++ *
++ * UTRACE_DETACH:
++ *
++ * After this, the @engine data structure is no longer accessible,
++ * and the thread might be reaped. The thread will start running
++ * again if it was stopped and no longer has any attached engines
++ * that want it stopped.
++ *
++ * If the @report_reap callback may already have begun, this fails
++ * with -%ESRCH. If the @report_death callback may already have
++ * begun, this fails with -%EALREADY.
++ *
++ * If @target is not already stopped, then a callback to this engine
++ * might be in progress or about to start on another CPU. If so,
++ * then this returns -%EINPROGRESS; the detach happens as soon as
++ * the pending callback is finished. To synchronize after an
++ * -%EINPROGRESS return, see utrace_barrier().
++ *
++ * If @target is properly stopped before utrace_control() is called,
++ * then after successful return it's guaranteed that no more callbacks
++ * to the @engine->ops vector will be made.
++ *
++ * The only exception is %SIGKILL (and exec or group-exit by another
++ * thread in the group), which can cause asynchronous @report_death
++ * and/or @report_reap callbacks even when %UTRACE_STOP was used.
++ * (In that event, this fails with -%ESRCH or -%EALREADY, see above.)
++ *
++ * UTRACE_STOP:
++ *
++ * This asks that @target stop running. This returns 0 only if
++ * @target is already stopped, either for tracing or for job
++ * control. Then @target will remain stopped until another
++ * utrace_control() call is made on @engine; @target can be woken
++ * only by %SIGKILL (or equivalent, such as exec or termination by
++ * another thread in the same thread group).
++ *
++ * This returns -%EINPROGRESS if @target is not already stopped.
++ * Then the effect is like %UTRACE_REPORT. A @report_quiesce or
++ * @report_signal callback will be made soon. Your callback can
++ * then return %UTRACE_STOP to keep @target stopped.
++ *
++ * This does not interrupt system calls in progress, including ones
++ * that sleep for a long time. For that, use %UTRACE_INTERRUPT.
++ * To interrupt system calls and then keep @target stopped, your
++ * @report_signal callback can return %UTRACE_STOP.
++ *
++ * UTRACE_RESUME:
++ *
++ * Just let @target continue running normally, reversing the effect
++ * of a previous %UTRACE_STOP. If another engine is keeping @target
++ * stopped, then it remains stopped until all engines let it resume.
++ * If @target was not stopped, this has no effect.
++ *
++ * UTRACE_REPORT:
++ *
++ * This is like %UTRACE_RESUME, but also ensures that there will be
++ * a @report_quiesce or @report_signal callback made soon. If
++ * @target had been stopped, then there will be a callback before it
++ * resumes running normally. If another engine is keeping @target
++ * stopped, then there might be no callbacks until all engines let
++ * it resume.
++ *
++ * Since this is meaningless unless @report_quiesce callbacks will
++ * be made, it returns -%EINVAL if @engine lacks %UTRACE_EVENT(%QUIESCE).
++ *
++ * UTRACE_INTERRUPT:
++ *
++ * This is like %UTRACE_REPORT, but ensures that @target will make a
++ * @report_signal callback before it resumes or delivers signals.
++ * If @target was in a system call or about to enter one, work in
++ * progress will be interrupted as if by %SIGSTOP. If another
++ * engine is keeping @target stopped, then there might be no
++ * callbacks until all engines let it resume.
++ *
++ * This gives @engine an opportunity to introduce a forced signal
++ * disposition via its @report_signal callback.
++ *
++ * UTRACE_SINGLESTEP:
++ *
++ * It's invalid to use this unless arch_has_single_step() returned true.
++ * This is like %UTRACE_RESUME, but resumes for one user instruction only.
++ *
++ * Note that passing %UTRACE_SINGLESTEP or %UTRACE_BLOCKSTEP to
++ * utrace_control() or returning it from an event callback alone does
++ * not necessarily ensure that stepping will be enabled. If there are
++ * more callbacks made to any engine before returning to user mode,
++ * then the resume action is chosen only by the last set of callbacks.
++ * To be sure, enable %UTRACE_EVENT(%QUIESCE) and look for the
++ * @report_quiesce callback with a zero event mask, or the
++ * @report_signal callback with %UTRACE_SIGNAL_REPORT.
++ *
++ * Since this is not robust unless @report_quiesce callbacks will
++ * be made, it returns -%EINVAL if @engine lacks %UTRACE_EVENT(%QUIESCE).
++ *
++ * UTRACE_BLOCKSTEP:
++ *
++ * It's invalid to use this unless arch_has_block_step() returned true.
++ * This is like %UTRACE_SINGLESTEP, but resumes for one whole basic
++ * block of user instructions.
++ *
++ * Since this is not robust unless @report_quiesce callbacks will
++ * be made, it returns -%EINVAL if @engine lacks %UTRACE_EVENT(%QUIESCE).
++ *
++ * %UTRACE_BLOCKSTEP devolves to %UTRACE_SINGLESTEP when another
++ * tracing engine is using %UTRACE_SINGLESTEP at the same time.
++ */
++int utrace_control(struct task_struct *target,
++ struct utrace_engine *engine,
++ enum utrace_resume_action action)
++{
++ struct utrace *utrace;
++ bool reset;
++ int ret;
++
++ if (unlikely(action >= UTRACE_RESUME_MAX)) {
++ WARN(1, "invalid action argument to utrace_control()!");
++ return -EINVAL;
++ }
++
++ /*
++ * This is a sanity check for a programming error in the caller.
++ * Their request can only work properly in all cases by relying on
++ * a follow-up callback, but they didn't set one up! This check
++ * doesn't do locking, but it shouldn't matter. The caller has to
++ * be synchronously sure the callback is set up to be operating the
++ * interface properly.
++ */
++ if (action >= UTRACE_REPORT && action < UTRACE_RESUME &&
++ unlikely(!(engine->flags & UTRACE_EVENT(QUIESCE)))) {
++ WARN(1, "utrace_control() with no QUIESCE callback in place!");
++ return -EINVAL;
++ }
++
++ utrace = get_utrace_lock(target, engine, true);
++ if (unlikely(IS_ERR(utrace)))
++ return PTR_ERR(utrace);
++
++ reset = task_is_traced(target);
++ ret = 0;
++
++ /*
++ * ->exit_state can change under us, this doesn't matter.
++ * We do not care about ->exit_state in fact, but we do
++ * care about ->reap and ->death. If either flag is set,
++ * we must also see ->exit_state != 0.
++ */
++ if (unlikely(target->exit_state)) {
++ ret = utrace_control_dead(target, utrace, action);
++ if (ret) {
++ spin_unlock(&utrace->lock);
++ return ret;
++ }
++ reset = true;
++ }
++
++ switch (action) {
++ case UTRACE_STOP:
++ mark_engine_wants_stop(target, engine);
++ if (!reset && !utrace_do_stop(target, utrace))
++ ret = -EINPROGRESS;
++ reset = false;
++ break;
++
++ case UTRACE_DETACH:
++ if (engine_wants_stop(engine))
++ target->utrace_flags &= ~ENGINE_STOP;
++ mark_engine_detached(engine);
++ reset = reset || utrace_do_stop(target, utrace);
++ if (!reset) {
++ /*
++ * As in utrace_set_events(), this barrier ensures
++ * that our engine->flags changes have hit before we
++ * examine utrace->reporting, pairing with the barrier
++ * in start_callback(). If @target has not yet hit
++ * finish_callback() to clear utrace->reporting, we
++ * might be in the middle of a callback to @engine.
++ */
++ smp_mb();
++ if (utrace->reporting == engine)
++ ret = -EINPROGRESS;
++ }
++ break;
++
++ case UTRACE_RESUME:
++ clear_engine_wants_stop(engine);
++ break;
++
++ case UTRACE_BLOCKSTEP:
++ /*
++ * Resume from stopped, step one block.
++ * We fall through to treat it like UTRACE_SINGLESTEP.
++ */
++ if (unlikely(!arch_has_block_step())) {
++ WARN(1, "UTRACE_BLOCKSTEP when !arch_has_block_step()");
++ action = UTRACE_SINGLESTEP;
++ }
++
++ case UTRACE_SINGLESTEP:
++ /*
++ * Resume from stopped, step one instruction.
++ * We fall through to the UTRACE_REPORT case.
++ */
++ if (unlikely(!arch_has_single_step())) {
++ WARN(1,
++ "UTRACE_SINGLESTEP when !arch_has_single_step()");
++ reset = false;
++ ret = -EOPNOTSUPP;
++ break;
++ }
++
++ case UTRACE_REPORT:
++ /*
++ * Make the thread call tracehook_notify_resume() soon.
++ * But don't bother if it's already been interrupted.
++ * In that case, utrace_get_signal() will be reporting soon.
++ */
++ clear_engine_wants_stop(engine);
++ if (action < utrace->resume) {
++ utrace->resume = action;
++ set_notify_resume(target);
++ }
++ break;
++
++ case UTRACE_INTERRUPT:
++ /*
++ * Make the thread call tracehook_get_signal() soon.
++ */
++ clear_engine_wants_stop(engine);
++ if (utrace->resume == UTRACE_INTERRUPT)
++ break;
++ utrace->resume = UTRACE_INTERRUPT;
++
++ /*
++ * If it's not already stopped, interrupt it now. We need
++ * the siglock here in case it calls recalc_sigpending()
++ * and clears its own TIF_SIGPENDING. By taking the lock,
++ * we've serialized any later recalc_sigpending() after our
++ * setting of utrace->resume to force it on.
++ */
++ if (reset) {
++ /*
++ * This is really just to keep the invariant that
++ * TIF_SIGPENDING is set with UTRACE_INTERRUPT.
++ * When it's stopped, we know it's always going
++ * through utrace_get_signal() and will recalculate.
++ */
++ set_tsk_thread_flag(target, TIF_SIGPENDING);
++ } else {
++ struct sighand_struct *sighand;
++ unsigned long irqflags;
++ sighand = lock_task_sighand(target, &irqflags);
++ if (likely(sighand)) {
++ signal_wake_up(target, 0);
++ unlock_task_sighand(target, &irqflags);
++ }
++ }
++ break;
++
++ default:
++ BUG(); /* We checked it on entry. */
++ }
++
++ /*
++ * Let the thread resume running. If it's not stopped now,
++ * there is nothing more we need to do.
++ */
++ if (reset)
++ utrace_reset(target, utrace);
++ else
++ spin_unlock(&utrace->lock);
++
++ return ret;
++}
++EXPORT_SYMBOL_GPL(utrace_control);
++
++/**
++ * utrace_barrier - synchronize with simultaneous tracing callbacks
++ * @target: thread to affect
++ * @engine: engine to affect (can be detached)
++ *
++ * This blocks while @target might be in the midst of making a callback to
++ * @engine. It can be interrupted by signals and will return -%ERESTARTSYS.
++ * A return value of zero means no callback from @target to @engine was
++ * in progress. Any effect of its return value (such as %UTRACE_STOP) has
++ * already been applied to @engine.
++ *
++ * It's not necessary to keep the @target pointer alive for this call.
++ * It's only necessary to hold a ref on @engine. This will return
++ * safely even if @target has been reaped and has no task refs.
++ *
++ * A successful return from utrace_barrier() guarantees its ordering
++ * with respect to utrace_set_events() and utrace_control() calls. If
++ * @target was not properly stopped, event callbacks just disabled might
++ * still be in progress; utrace_barrier() waits until there is no chance
++ * an unwanted callback can be in progress.
++ */
++int utrace_barrier(struct task_struct *target, struct utrace_engine *engine)
++{
++ struct utrace *utrace;
++ int ret = -ERESTARTSYS;
++
++ if (unlikely(target == current))
++ return 0;
++
++ do {
++ utrace = get_utrace_lock(target, engine, false);
++ if (unlikely(IS_ERR(utrace))) {
++ ret = PTR_ERR(utrace);
++ if (ret != -ERESTARTSYS)
++ break;
++ } else {
++ /*
++ * All engine state changes are done while
++ * holding the lock, i.e. before we get here.
++ * Since we have the lock, we only need to
++ * worry about @target making a callback.
++ * When it has entered start_callback() but
++ * not yet gotten to finish_callback(), we
++ * will see utrace->reporting == @engine.
++ * When @target doesn't take the lock, it uses
++ * barriers to order setting utrace->reporting
++ * before it examines the engine state.
++ */
++ if (utrace->reporting != engine)
++ ret = 0;
++ spin_unlock(&utrace->lock);
++ if (!ret)
++ break;
++ }
++ schedule_timeout_interruptible(1);
++ } while (!signal_pending(current));
++
++ return ret;
++}
++EXPORT_SYMBOL_GPL(utrace_barrier);
++
++/*
++ * This is local state used for reporting loops, perhaps optimized away.
++ */
++struct utrace_report {
++ u32 result;
++ enum utrace_resume_action action;
++ enum utrace_resume_action resume_action;
++ bool detaches;
++ bool spurious;
++};
++
++#define INIT_REPORT(var) \
++ struct utrace_report var = { \
++ .action = UTRACE_RESUME, \
++ .resume_action = UTRACE_RESUME, \
++ .spurious = true \
++ }
++
++/*
++ * We are now making the report, so clear the flag saying we need one.
++ * When there is a new attach, ->pending_attach is set just so we will
++ * know to do splice_attaching() here before the callback loop.
++ */
++static enum utrace_resume_action start_report(struct utrace *utrace)
++{
++ enum utrace_resume_action resume = utrace->resume;
++ if (utrace->pending_attach ||
++ (resume > UTRACE_INTERRUPT && resume < UTRACE_RESUME)) {
++ spin_lock(&utrace->lock);
++ splice_attaching(utrace);
++ resume = utrace->resume;
++ if (resume > UTRACE_INTERRUPT)
++ utrace->resume = UTRACE_RESUME;
++ spin_unlock(&utrace->lock);
++ }
++ return resume;
++}
++
++static inline void finish_report_reset(struct task_struct *task,
++ struct utrace *utrace,
++ struct utrace_report *report)
++{
++ if (unlikely(report->spurious || report->detaches)) {
++ spin_lock(&utrace->lock);
++ if (utrace_reset(task, utrace))
++ report->action = UTRACE_RESUME;
++ }
++}
++
++/*
++ * Complete a normal reporting pass, pairing with a start_report() call.
++ * This handles any UTRACE_DETACH or UTRACE_REPORT or UTRACE_INTERRUPT
++ * returns from engine callbacks. If @will_not_stop is true and any
++ * engine's last callback used UTRACE_STOP, we do UTRACE_REPORT here to
++ * ensure we stop before user mode. If there were no callbacks made, it
++ * will recompute @task->utrace_flags to avoid another false-positive.
++ */
++static void finish_report(struct task_struct *task, struct utrace *utrace,
++ struct utrace_report *report, bool will_not_stop)
++{
++ enum utrace_resume_action resume = report->action;
++
++ if (resume == UTRACE_STOP)
++ resume = will_not_stop ? UTRACE_REPORT : UTRACE_RESUME;
++
++ if (resume < utrace->resume) {
++ spin_lock(&utrace->lock);
++ utrace->resume = resume;
++ if (resume == UTRACE_INTERRUPT)
++ set_tsk_thread_flag(task, TIF_SIGPENDING);
++ else
++ set_tsk_thread_flag(task, TIF_NOTIFY_RESUME);
++ spin_unlock(&utrace->lock);
++ }
++
++ finish_report_reset(task, utrace, report);
++}
++
++static void finish_callback_report(struct task_struct *task,
++ struct utrace *utrace,
++ struct utrace_report *report,
++ struct utrace_engine *engine,
++ enum utrace_resume_action action)
++{
++ if (action == UTRACE_DETACH) {
++ /*
++ * By holding the lock here, we make sure that
++ * utrace_barrier() (really get_utrace_lock()) sees the
++ * effect of this detach. Otherwise utrace_barrier() could
++ * return 0 after this callback had returned UTRACE_DETACH.
++ * This way, a 0 return is an unambiguous indicator that any
++ * callback returning UTRACE_DETACH has indeed caused detach.
++ */
++ spin_lock(&utrace->lock);
++ engine->ops = &utrace_detached_ops;
++ spin_unlock(&utrace->lock);
++ }
++
++ /*
++ * If utrace_control() was used, treat that like UTRACE_DETACH here.
++ */
++ if (engine->ops == &utrace_detached_ops) {
++ report->detaches = true;
++ return;
++ }
++
++ if (action < report->action)
++ report->action = action;
++
++ if (action != UTRACE_STOP) {
++ if (action < report->resume_action)
++ report->resume_action = action;
++
++ if (engine_wants_stop(engine)) {
++ spin_lock(&utrace->lock);
++ clear_engine_wants_stop(engine);
++ spin_unlock(&utrace->lock);
++ }
++
++ return;
++ }
++
++ if (!engine_wants_stop(engine)) {
++ spin_lock(&utrace->lock);
++ /*
++ * If utrace_control() came in and detached us
++ * before we got the lock, we must not stop now.
++ */
++ if (unlikely(engine->ops == &utrace_detached_ops))
++ report->detaches = true;
++ else
++ mark_engine_wants_stop(task, engine);
++ spin_unlock(&utrace->lock);
++ }
++}
++
++/*
++ * Apply the return value of one engine callback to @report.
++ * Returns true if @engine detached and should not get any more callbacks.
++ */
++static bool finish_callback(struct task_struct *task, struct utrace *utrace,
++ struct utrace_report *report,
++ struct utrace_engine *engine,
++ u32 ret)
++{
++ report->result = ret & ~UTRACE_RESUME_MASK;
++ finish_callback_report(task, utrace, report, engine,
++ utrace_resume_action(ret));
++
++ /*
++ * Now that we have applied the effect of the return value,
++ * clear this so that utrace_barrier() can stop waiting.
++ * A subsequent utrace_control() can stop or resume @engine
++ * and know this was ordered after its callback's action.
++ *
++ * We don't need any barriers here because utrace_barrier()
++ * takes utrace->lock. If we touched engine->flags above,
++ * the lock guaranteed this change was before utrace_barrier()
++ * examined utrace->reporting.
++ */
++ utrace->reporting = NULL;
++
++ /*
++ * We've just done an engine callback. These are allowed to sleep,
++ * though all well-behaved ones restrict that to blocking kalloc()
++ * or quickly-acquired mutex_lock() and the like. This is a good
++ * place to make sure tracing engines don't introduce too much
++ * latency under voluntary preemption.
++ */
++ might_sleep();
++
++ return engine->ops == &utrace_detached_ops;
++}
++
++/*
++ * Start the callbacks for @engine to consider @event (a bit mask).
++ * This makes the report_quiesce() callback first. If @engine wants
++ * a specific callback for @event, we return the ops vector to use.
++ * If not, we return NULL. The return value from the ops->callback
++ * function called should be passed to finish_callback().
++ */
++static const struct utrace_engine_ops *start_callback(
++ struct utrace *utrace, struct utrace_report *report,
++ struct utrace_engine *engine, struct task_struct *task,
++ unsigned long event)
++{
++ const struct utrace_engine_ops *ops;
++ unsigned long want;
++
++ /*
++ * This barrier ensures that we've set utrace->reporting before
++ * we examine engine->flags or engine->ops. utrace_barrier()
++ * relies on this ordering to indicate that the effect of any
++ * utrace_control() and utrace_set_events() calls is in place
++ * by the time utrace->reporting can be seen to be NULL.
++ */
++ utrace->reporting = engine;
++ smp_mb();
++
++ /*
++ * This pairs with the barrier in mark_engine_detached().
++ * It makes sure that we never see the old ops vector with
++ * the new flags, in case the original vector had no report_quiesce.
++ */
++ want = engine->flags;
++ smp_rmb();
++ ops = engine->ops;
++
++ if ((want & UTRACE_EVENT(QUIESCE)) || ops == &utrace_detached_ops) {
++ if (finish_callback(task, utrace, report, engine,
++ (*ops->report_quiesce)(report->action,
++ engine, event)))
++ return NULL;
++
++ if (!event) {
++ /* We only got here to report QUIESCE */
++ report->spurious = false;
++ return NULL;
++ }
++
++ /*
++ * finish_callback() reset utrace->reporting after the
++ * quiesce callback. Now we set it again (as above)
++ * before re-examining engine->flags, which could have
++ * been changed synchronously by ->report_quiesce or
++ * asynchronously by utrace_control() or utrace_set_events().
++ */
++ utrace->reporting = engine;
++ smp_mb();
++ want = engine->flags;
++ }
++
++ if (want & ENGINE_STOP)
++ report->action = UTRACE_STOP;
++
++ if (want & event) {
++ report->spurious = false;
++ return ops;
++ }
++
++ utrace->reporting = NULL;
++ return NULL;
++}
++
++/*
++ * Do a normal reporting pass for engines interested in @event.
++ * @callback is the name of the member in the ops vector, and remaining
++ * args are the extras it takes after the standard three args.
++ */
++#define REPORT_CALLBACKS(rev, task, utrace, report, event, callback, ...) \
++ do { \
++ struct utrace_engine *engine; \
++ const struct utrace_engine_ops *ops; \
++ list_for_each_entry##rev(engine, &utrace->attached, entry) { \
++ ops = start_callback(utrace, report, engine, task, \
++ event); \
++ if (!ops) \
++ continue; \
++ finish_callback(task, utrace, report, engine, \
++ (*ops->callback)(__VA_ARGS__)); \
++ } \
++ } while (0)
++#define REPORT(task, utrace, report, event, callback, ...) \
++ do { \
++ start_report(utrace); \
++ REPORT_CALLBACKS(, task, utrace, report, event, callback, \
++ (report)->action, engine, ## __VA_ARGS__); \
++ finish_report(task, utrace, report, true); \
++ } while (0)
++
++/*
++ * Called iff UTRACE_EVENT(EXEC) flag is set.
++ */
++void utrace_report_exec(struct linux_binfmt *fmt, struct linux_binprm *bprm,
++ struct pt_regs *regs)
++{
++ struct task_struct *task = current;
++ struct utrace *utrace = task_utrace_struct(task);
++ INIT_REPORT(report);
++
++ REPORT(task, utrace, &report, UTRACE_EVENT(EXEC),
++ report_exec, fmt, bprm, regs);
++}
++
++static u32 do_report_syscall_entry(struct pt_regs *regs,
++ struct task_struct *task,
++ struct utrace *utrace,
++ struct utrace_report *report,
++ u32 resume_report)
++{
++ start_report(utrace);
++ REPORT_CALLBACKS(_reverse, task, utrace, report,
++ UTRACE_EVENT(SYSCALL_ENTRY), report_syscall_entry,
++ resume_report | report->result | report->action,
++ engine, regs);
++ finish_report(task, utrace, report, false);
++
++ if (report->action != UTRACE_STOP)
++ return 0;
++
++ utrace_stop(task, utrace, report->resume_action);
++
++ if (fatal_signal_pending(task)) {
++ /*
++ * We are continuing despite UTRACE_STOP because of a
++ * SIGKILL. Don't let the system call actually proceed.
++ */
++ report->result = UTRACE_SYSCALL_ABORT;
++ } else if (utrace->resume <= UTRACE_REPORT) {
++ /*
++ * If we've been asked for another report after our stop,
++ * go back to report (and maybe stop) again before we run
++ * the system call. The second (and later) reports are
++ * marked with the UTRACE_SYSCALL_RESUMED flag so that
++ * engines know this is a second report at the same
++ * entry. This gives them the chance to examine the
++ * registers anew after they might have been changed
++ * while we were stopped.
++ */
++ report->detaches = false;
++ report->spurious = true;
++ report->action = report->resume_action = UTRACE_RESUME;
++ return UTRACE_SYSCALL_RESUMED;
++ }
++
++ return 0;
++}
++
++/*
++ * Called iff UTRACE_EVENT(SYSCALL_ENTRY) flag is set.
++ * Return true to prevent the system call.
++ */
++bool utrace_report_syscall_entry(struct pt_regs *regs)
++{
++ struct task_struct *task = current;
++ struct utrace *utrace = task_utrace_struct(task);
++ INIT_REPORT(report);
++ u32 resume_report = 0;
++
++ do {
++ resume_report = do_report_syscall_entry(regs, task, utrace,
++ &report, resume_report);
++ } while (resume_report);
++
++ return utrace_syscall_action(report.result) == UTRACE_SYSCALL_ABORT;
++}
++
++/*
++ * Called iff UTRACE_EVENT(SYSCALL_EXIT) flag is set.
++ */
++void utrace_report_syscall_exit(struct pt_regs *regs)
++{
++ struct task_struct *task = current;
++ struct utrace *utrace = task_utrace_struct(task);
++ INIT_REPORT(report);
++
++ REPORT(task, utrace, &report, UTRACE_EVENT(SYSCALL_EXIT),
++ report_syscall_exit, regs);
++}
++
++/*
++ * Called iff UTRACE_EVENT(CLONE) flag is set.
++ * This notification call blocks the wake_up_new_task call on the child.
++ * So we must not quiesce here. tracehook_report_clone_complete will do
++ * a quiescence check momentarily.
++ */
++void utrace_report_clone(unsigned long clone_flags, struct task_struct *child)
++{
++ struct task_struct *task = current;
++ struct utrace *utrace = task_utrace_struct(task);
++ INIT_REPORT(report);
++
++ /*
++ * We don't use the REPORT() macro here, because we need
++ * to clear utrace->cloning before finish_report().
++ * After finish_report(), utrace can be a stale pointer
++ * in cases when report.action is still UTRACE_RESUME.
++ */
++ start_report(utrace);
++ utrace->cloning = child;
++
++ REPORT_CALLBACKS(, task, utrace, &report,
++ UTRACE_EVENT(CLONE), report_clone,
++ report.action, engine, clone_flags, child);
++
++ utrace->cloning = NULL;
++ finish_report(task, utrace, &report, !(clone_flags & CLONE_VFORK));
++
++ /*
++ * For a vfork, we will go into an uninterruptible block waiting
++ * for the child. We need UTRACE_STOP to happen before this, not
++ * after. For CLONE_VFORK, utrace_finish_vfork() will be called.
++ */
++ if (report.action == UTRACE_STOP && (clone_flags & CLONE_VFORK)) {
++ spin_lock(&utrace->lock);
++ utrace->vfork_stop = 1;
++ spin_unlock(&utrace->lock);
++ }
++}
++
++/*
++ * We're called after utrace_report_clone() for a CLONE_VFORK.
++ * If UTRACE_STOP was left from the clone report, we stop here.
++ * After this, we'll enter the uninterruptible wait_for_completion()
++ * waiting for the child.
++ */
++void utrace_finish_vfork(struct task_struct *task)
++{
++ struct utrace *utrace = task_utrace_struct(task);
++
++ if (utrace->vfork_stop) {
++ spin_lock(&utrace->lock);
++ utrace->vfork_stop = 0;
++ spin_unlock(&utrace->lock);
++ utrace_stop(task, utrace, UTRACE_RESUME); /* XXX */
++ }
++}
++
++/*
++ * Called iff UTRACE_EVENT(JCTL) flag is set.
++ *
++ * Called with siglock held.
++ */
++void utrace_report_jctl(int notify, int what)
++{
++ struct task_struct *task = current;
++ struct utrace *utrace = task_utrace_struct(task);
++ INIT_REPORT(report);
++
++ spin_unlock_irq(&task->sighand->siglock);
++
++ REPORT(task, utrace, &report, UTRACE_EVENT(JCTL),
++ report_jctl, what, notify);
++
++ spin_lock_irq(&task->sighand->siglock);
++}
++
++/*
++ * Called iff UTRACE_EVENT(EXIT) flag is set.
++ */
++void utrace_report_exit(long *exit_code)
++{
++ struct task_struct *task = current;
++ struct utrace *utrace = task_utrace_struct(task);
++ INIT_REPORT(report);
++ long orig_code = *exit_code;
++
++ REPORT(task, utrace, &report, UTRACE_EVENT(EXIT),
++ report_exit, orig_code, exit_code);
++
++ if (report.action == UTRACE_STOP)
++ utrace_stop(task, utrace, report.resume_action);
++}
++
++/*
++ * Called iff UTRACE_EVENT(DEATH) or UTRACE_EVENT(QUIESCE) flag is set.
++ *
++ * It is always possible that we are racing with utrace_release_task here.
++ * For this reason, utrace_release_task checks for the event bits that get
++ * us here, and delays its cleanup for us to do.
++ */
++void utrace_report_death(struct task_struct *task, struct utrace *utrace,
++ bool group_dead, int signal)
++{
++ INIT_REPORT(report);
++
++ BUG_ON(!task->exit_state);
++
++ /*
++ * We are presently considered "quiescent"--which is accurate
++ * inasmuch as we won't run any more user instructions ever again.
++ * But for utrace_control and utrace_set_events to be robust, they
++ * must be sure whether or not we will run any more callbacks. If
++ * a call comes in before we do, taking the lock here synchronizes
++ * us so we don't run any callbacks just disabled. Calls that come
++ * in while we're running the callbacks will see the exit.death
++ * flag and know that we are not yet fully quiescent for purposes
++ * of detach bookkeeping.
++ */
++ spin_lock(&utrace->lock);
++ BUG_ON(utrace->death);
++ utrace->death = 1;
++ utrace->resume = UTRACE_RESUME;
++ splice_attaching(utrace);
++ spin_unlock(&utrace->lock);
++
++ REPORT_CALLBACKS(, task, utrace, &report, UTRACE_EVENT(DEATH),
++ report_death, engine, group_dead, signal);
++
++ utrace_maybe_reap(task, utrace, false);
++}
++
++/*
++ * Finish the last reporting pass before returning to user mode.
++ */
++static void finish_resume_report(struct task_struct *task,
++ struct utrace *utrace,
++ struct utrace_report *report)
++{
++ finish_report_reset(task, utrace, report);
++
++ switch (report->action) {
++ case UTRACE_STOP:
++ utrace_stop(task, utrace, report->resume_action);
++ break;
++
++ case UTRACE_INTERRUPT:
++ if (!signal_pending(task))
++ set_tsk_thread_flag(task, TIF_SIGPENDING);
++ break;
++
++ case UTRACE_BLOCKSTEP:
++ if (likely(arch_has_block_step())) {
++ user_enable_block_step(task);
++ break;
++ }
++
++ /*
++ * This means some callback is to blame for failing
++ * to check arch_has_block_step() itself. Warn and
++ * then fall through to treat it as SINGLESTEP.
++ */
++ WARN(1, "UTRACE_BLOCKSTEP when !arch_has_block_step()");
++
++ case UTRACE_SINGLESTEP:
++ if (likely(arch_has_single_step())) {
++ user_enable_single_step(task);
++ } else {
++ /*
++ * This means some callback is to blame for failing
++ * to check arch_has_single_step() itself. Spew
++ * about it so the loser will fix his module.
++ */
++ WARN(1,
++ "UTRACE_SINGLESTEP when !arch_has_single_step()");
++ }
++ break;
++
++ case UTRACE_REPORT:
++ case UTRACE_RESUME:
++ default:
++ user_disable_single_step(task);
++ break;
++ }
++}
++
++/*
++ * This is called when TIF_NOTIFY_RESUME had been set (and is now clear).
++ * We are close to user mode, and this is the place to report or stop.
++ * When we return, we're going to user mode or into the signals code.
++ */
++void utrace_resume(struct task_struct *task, struct pt_regs *regs)
++{
++ struct utrace *utrace = task_utrace_struct(task);
++ INIT_REPORT(report);
++ struct utrace_engine *engine;
++
++ /*
++ * Some machines get here with interrupts disabled. The same arch
++ * code path leads to calling into get_signal_to_deliver(), which
++ * implicitly reenables them by virtue of spin_unlock_irq.
++ */
++ local_irq_enable();
++
++ /*
++ * If this flag is still set it's because there was a signal
++ * handler setup done but no report_signal following it. Clear
++ * the flag before we get to user so it doesn't confuse us later.
++ */
++ if (unlikely(utrace->signal_handler)) {
++ spin_lock(&utrace->lock);
++ utrace->signal_handler = 0;
++ spin_unlock(&utrace->lock);
++ }
++
++ /*
++ * Update our bookkeeping even if there are no callbacks made here.
++ */
++ report.action = start_report(utrace);
++
++ switch (report.action) {
++ case UTRACE_RESUME:
++ /*
++ * Anything we might have done was already handled by
++ * utrace_get_signal(), or this is an entirely spurious
++ * call. (The arch might use TIF_NOTIFY_RESUME for other
++ * purposes as well as calling us.)
++ */
++ return;
++ case UTRACE_REPORT:
++ if (unlikely(!(task->utrace_flags & UTRACE_EVENT(QUIESCE))))
++ break;
++ /*
++ * Do a simple reporting pass, with no specific
++ * callback after report_quiesce.
++ */
++ report.action = UTRACE_RESUME;
++ list_for_each_entry(engine, &utrace->attached, entry)
++ start_callback(utrace, &report, engine, task, 0);
++ break;
++ default:
++ /*
++ * Even if this report was truly spurious, there is no need
++ * for utrace_reset() now. TIF_NOTIFY_RESUME was already
++ * cleared--it doesn't stay spuriously set.
++ */
++ report.spurious = false;
++ break;
++ }
++
++ /*
++ * Finish the report and either stop or get ready to resume.
++ * If utrace->resume was not UTRACE_REPORT, this applies its
++ * effect now (i.e. step or interrupt).
++ */
++ finish_resume_report(task, utrace, &report);
++}
++
++/*
++ * Return true if current has forced signal_pending().
++ *
++ * This is called only when current->utrace_flags is nonzero, so we know
++ * that current->utrace must be set. It's not inlined in tracehook.h
++ * just so that struct utrace can stay opaque outside this file.
++ */
++bool utrace_interrupt_pending(void)
++{
++ return task_utrace_struct(current)->resume == UTRACE_INTERRUPT;
++}
++
++/*
++ * Take the siglock and push @info back on our queue.
++ * Returns with @task->sighand->siglock held.
++ */
++static void push_back_signal(struct task_struct *task, siginfo_t *info)
++ __acquires(task->sighand->siglock)
++{
++ struct sigqueue *q;
++
++ if (unlikely(!info->si_signo)) { /* Oh, a wise guy! */
++ spin_lock_irq(&task->sighand->siglock);
++ return;
++ }
++
++ q = sigqueue_alloc();
++ if (likely(q)) {
++ q->flags = 0;
++ copy_siginfo(&q->info, info);
++ }
++
++ spin_lock_irq(&task->sighand->siglock);
++
++ sigaddset(&task->pending.signal, info->si_signo);
++ if (likely(q))
++ list_add(&q->list, &task->pending.list);
++
++ set_tsk_thread_flag(task, TIF_SIGPENDING);
++}
++
++/*
++ * This is the hook from the signals code, called with the siglock held.
++ * Here is the ideal place to stop. We also dequeue and intercept signals.
++ */
++int utrace_get_signal(struct task_struct *task, struct pt_regs *regs,
++ siginfo_t *info, struct k_sigaction *return_ka)
++ __releases(task->sighand->siglock)
++ __acquires(task->sighand->siglock)
++{
++ struct utrace *utrace;
++ struct k_sigaction *ka;
++ INIT_REPORT(report);
++ struct utrace_engine *engine;
++ const struct utrace_engine_ops *ops;
++ unsigned long event, want;
++ u32 ret;
++ int signr;
++
++ utrace = task_utrace_struct(task);
++ if (utrace->resume < UTRACE_RESUME ||
++ utrace->pending_attach || utrace->signal_handler) {
++ enum utrace_resume_action resume;
++
++ /*
++ * We've been asked for an explicit report before we
++ * even check for pending signals.
++ */
++
++ spin_unlock_irq(&task->sighand->siglock);
++
++ spin_lock(&utrace->lock);
++
++ splice_attaching(utrace);
++
++ report.result = utrace->signal_handler ?
++ UTRACE_SIGNAL_HANDLER : UTRACE_SIGNAL_REPORT;
++ utrace->signal_handler = 0;
++
++ resume = utrace->resume;
++ utrace->resume = UTRACE_RESUME;
++
++ spin_unlock(&utrace->lock);
++
++ /*
++ * Make sure signal_pending() only returns true
++ * if there are real signals pending.
++ */
++ if (signal_pending(task)) {
++ spin_lock_irq(&task->sighand->siglock);
++ recalc_sigpending();
++ spin_unlock_irq(&task->sighand->siglock);
++ }
++
++ if (resume > UTRACE_REPORT) {
++ /*
++ * We only got here to process utrace->resume.
++ * Despite no callbacks, this report is not spurious.
++ */
++ report.action = resume;
++ report.spurious = false;
++ finish_resume_report(task, utrace, &report);
++ return -1;
++ } else if (!(task->utrace_flags & UTRACE_EVENT(QUIESCE))) {
++ /*
++ * We only got here to clear utrace->signal_handler.
++ */
++ return -1;
++ }
++
++ /*
++ * Do a reporting pass for no signal, just for EVENT(QUIESCE).
++ * The engine callbacks can fill in *info and *return_ka.
++ * We'll pass NULL for the @orig_ka argument to indicate
++ * that there was no original signal.
++ */
++ event = 0;
++ ka = NULL;
++ memset(return_ka, 0, sizeof *return_ka);
++ } else if (!(task->utrace_flags & UTRACE_EVENT_SIGNAL_ALL) ||
++ unlikely(task->signal->group_stop_count)) {
++ /*
++ * If no engine is interested in intercepting signals or
++ * we must stop, let the caller just dequeue them normally
++ * or participate in group-stop.
++ */
++ return 0;
++ } else {
++ /*
++ * Steal the next signal so we can let tracing engines
++ * examine it. From the signal number and sigaction,
++ * determine what normal delivery would do. If no
++ * engine perturbs it, we'll do that by returning the
++ * signal number after setting *return_ka.
++ */
++ signr = dequeue_signal(task, &task->blocked, info);
++ if (signr == 0)
++ return signr;
++ BUG_ON(signr != info->si_signo);
++
++ ka = &task->sighand->action[signr - 1];
++ *return_ka = *ka;
++
++ /*
++ * We are never allowed to interfere with SIGKILL.
++ * Just punt after filling in *return_ka for our caller.
++ */
++ if (signr == SIGKILL)
++ return signr;
++
++ if (ka->sa.sa_handler == SIG_IGN) {
++ event = UTRACE_EVENT(SIGNAL_IGN);
++ report.result = UTRACE_SIGNAL_IGN;
++ } else if (ka->sa.sa_handler != SIG_DFL) {
++ event = UTRACE_EVENT(SIGNAL);
++ report.result = UTRACE_SIGNAL_DELIVER;
++ } else if (sig_kernel_coredump(signr)) {
++ event = UTRACE_EVENT(SIGNAL_CORE);
++ report.result = UTRACE_SIGNAL_CORE;
++ } else if (sig_kernel_ignore(signr)) {
++ event = UTRACE_EVENT(SIGNAL_IGN);
++ report.result = UTRACE_SIGNAL_IGN;
++ } else if (signr == SIGSTOP) {
++ event = UTRACE_EVENT(SIGNAL_STOP);
++ report.result = UTRACE_SIGNAL_STOP;
++ } else if (sig_kernel_stop(signr)) {
++ event = UTRACE_EVENT(SIGNAL_STOP);
++ report.result = UTRACE_SIGNAL_TSTP;
++ } else {
++ event = UTRACE_EVENT(SIGNAL_TERM);
++ report.result = UTRACE_SIGNAL_TERM;
++ }
++
++ /*
++ * Now that we know what event type this signal is, we
++ * can short-circuit if no engines care about those.
++ */
++ if ((task->utrace_flags & (event | UTRACE_EVENT(QUIESCE))) == 0)
++ return signr;
++
++ /*
++ * We have some interested engines, so tell them about
++ * the signal and let them change its disposition.
++ */
++ spin_unlock_irq(&task->sighand->siglock);
++ }
++
++ /*
++ * This reporting pass chooses what signal disposition we'll act on.
++ */
++ list_for_each_entry(engine, &utrace->attached, entry) {
++ /*
++ * See start_callback() comment about this barrier.
++ */
++ utrace->reporting = engine;
++ smp_mb();
++
++ /*
++ * This pairs with the barrier in mark_engine_detached(),
++ * see start_callback() comments.
++ */
++ want = engine->flags;
++ smp_rmb();
++ ops = engine->ops;
++
++ if ((want & (event | UTRACE_EVENT(QUIESCE))) == 0) {
++ utrace->reporting = NULL;
++ continue;
++ }
++
++ if (ops->report_signal)
++ ret = (*ops->report_signal)(
++ report.result | report.action, engine,
++ regs, info, ka, return_ka);
++ else
++ ret = (report.result | (*ops->report_quiesce)(
++ report.action, engine, event));
++
++ /*
++ * Avoid a tight loop reporting again and again if some
++ * engine is too stupid.
++ */
++ switch (utrace_resume_action(ret)) {
++ default:
++ break;
++ case UTRACE_INTERRUPT:
++ case UTRACE_REPORT:
++ ret = (ret & ~UTRACE_RESUME_MASK) | UTRACE_RESUME;
++ break;
++ }
++
++ finish_callback(task, utrace, &report, engine, ret);
++ }
++
++ /*
++ * We express the chosen action to the signals code in terms
++ * of a representative signal whose default action does it.
++ * Our caller uses our return value (signr) to decide what to
++ * do, but uses info->si_signo as the signal number to report.
++ */
++ switch (utrace_signal_action(report.result)) {
++ case UTRACE_SIGNAL_TERM:
++ signr = SIGTERM;
++ break;
++
++ case UTRACE_SIGNAL_CORE:
++ signr = SIGQUIT;
++ break;
++
++ case UTRACE_SIGNAL_STOP:
++ signr = SIGSTOP;
++ break;
++
++ case UTRACE_SIGNAL_TSTP:
++ signr = SIGTSTP;
++ break;
++
++ case UTRACE_SIGNAL_DELIVER:
++ signr = info->si_signo;
++
++ if (return_ka->sa.sa_handler == SIG_DFL) {
++ /*
++ * We'll do signr's normal default action.
++ * For ignore, we'll fall through below.
++ * For stop/death, break locks and returns it.
++ */
++ if (likely(signr) && !sig_kernel_ignore(signr))
++ break;
++ } else if (return_ka->sa.sa_handler != SIG_IGN &&
++ likely(signr)) {
++ /*
++ * Complete the bookkeeping after the report.
++ * The handler will run. If an engine wanted to
++ * stop or step, then make sure we do another
++ * report after signal handler setup.
++ */
++ if (report.action != UTRACE_RESUME)
++ report.action = UTRACE_INTERRUPT;
++ finish_report(task, utrace, &report, true);
++
++ if (unlikely(report.result & UTRACE_SIGNAL_HOLD))
++ push_back_signal(task, info);
++ else
++ spin_lock_irq(&task->sighand->siglock);
++
++ /*
++ * We do the SA_ONESHOT work here since the
++ * normal path will only touch *return_ka now.
++ */
++ if (unlikely(return_ka->sa.sa_flags & SA_ONESHOT)) {
++ return_ka->sa.sa_flags &= ~SA_ONESHOT;
++ if (likely(valid_signal(signr))) {
++ ka = &task->sighand->action[signr - 1];
++ ka->sa.sa_handler = SIG_DFL;
++ }
++ }
++
++ return signr;
++ }
++
++ /* Fall through for an ignored signal. */
++
++ case UTRACE_SIGNAL_IGN:
++ case UTRACE_SIGNAL_REPORT:
++ default:
++ /*
++ * If the signal is being ignored, then we are on the way
++ * directly back to user mode. We can stop here, or step,
++ * as in utrace_resume(), above. After we've dealt with that,
++ * our caller will relock and come back through here.
++ */
++ finish_resume_report(task, utrace, &report);
++
++ if (unlikely(fatal_signal_pending(task))) {
++ /*
++ * The only reason we woke up now was because of a
++ * SIGKILL. Don't do normal dequeuing in case it
++ * might get a signal other than SIGKILL. That would
++ * perturb the death state so it might differ from
++ * what the debugger would have allowed to happen.
++ * Instead, pluck out just the SIGKILL to be sure
++ * we'll die immediately with nothing else different
++ * from the quiescent state the debugger wanted us in.
++ */
++ sigset_t sigkill_only;
++ siginitsetinv(&sigkill_only, sigmask(SIGKILL));
++ spin_lock_irq(&task->sighand->siglock);
++ signr = dequeue_signal(task, &sigkill_only, info);
++ BUG_ON(signr != SIGKILL);
++ *return_ka = task->sighand->action[SIGKILL - 1];
++ return signr;
++ }
++
++ if (unlikely(report.result & UTRACE_SIGNAL_HOLD)) {
++ push_back_signal(task, info);
++ spin_unlock_irq(&task->sighand->siglock);
++ }
++
++ return -1;
++ }
++
++ /*
++ * Complete the bookkeeping after the report.
++ * This sets utrace->resume if UTRACE_STOP was used.
++ */
++ finish_report(task, utrace, &report, true);
++
++ return_ka->sa.sa_handler = SIG_DFL;
++
++ /*
++ * If this signal is fatal, si_signo gets through as exit_code.
++ * We can't allow a completely bogus value there or else core
++ * kernel code can freak out. (If an engine wants to control
++ * the exit_code value exactly, it can do so in report_exit.)
++ * We'll produce a big complaint in dmesg, but won't crash.
++ * That's nicer for debugging your utrace engine.
++ */
++ if (unlikely(info->si_signo & 0x80)) {
++ WARN(1, "utrace engine left bogus si_signo value!");
++ info->si_signo = SIGTRAP;
++ }
++
++ if (unlikely(report.result & UTRACE_SIGNAL_HOLD))
++ push_back_signal(task, info);
++ else
++ spin_lock_irq(&task->sighand->siglock);
++
++ if (sig_kernel_stop(signr))
++ task->group_stop |= GROUP_STOP_DEQUEUED;
++
++ return signr;
++}
++
++/*
++ * This gets called after a signal handler has been set up.
++ * We set a flag so the next report knows it happened.
++ * If we're already stepping, make sure we do a report_signal.
++ * If not, make sure we get into utrace_resume() where we can
++ * clear the signal_handler flag before resuming.
++ */
++void utrace_signal_handler(struct task_struct *task, int stepping)
++{
++ struct utrace *utrace = task_utrace_struct(task);
++
++ spin_lock(&utrace->lock);
++
++ utrace->signal_handler = 1;
++ if (utrace->resume > UTRACE_INTERRUPT) {
++ if (stepping) {
++ utrace->resume = UTRACE_INTERRUPT;
++ set_tsk_thread_flag(task, TIF_SIGPENDING);
++ } else if (utrace->resume == UTRACE_RESUME) {
++ set_tsk_thread_flag(task, TIF_NOTIFY_RESUME);
++ }
++ }
++
++ spin_unlock(&utrace->lock);
++}
++
++/**
++ * utrace_prepare_examine - prepare to examine thread state
++ * @target: thread of interest, a &struct task_struct pointer
++ * @engine: engine pointer returned by utrace_attach_task()
++ * @exam: temporary state, a &struct utrace_examiner pointer
++ *
++ * This call prepares to safely examine the thread @target using
++ * &struct user_regset calls, or direct access to thread-synchronous fields.
++ *
++ * When @target is current, this call is superfluous. When @target is
++ * another thread, it must be held stopped via %UTRACE_STOP by @engine.
++ *
++ * This call may block the caller until @target stays stopped, so it must
++ * be called only after the caller is sure @target is about to unschedule.
++ * This means a zero return from a utrace_control() call on @engine giving
++ * %UTRACE_STOP, or a report_quiesce() or report_signal() callback to
++ * @engine that used %UTRACE_STOP in its return value.
++ *
++ * Returns -%ESRCH if @target is dead or -%EINVAL if %UTRACE_STOP was
++ * not used. If @target has started running again despite %UTRACE_STOP
++ * (for %SIGKILL or a spurious wakeup), this call returns -%EAGAIN.
++ *
++ * When this call returns zero, it's safe to use &struct user_regset
++ * calls and task_user_regset_view() on @target and to examine some of
++ * its fields directly. When the examination is complete, a
++ * utrace_finish_examine() call must follow to check whether it was
++ * completed safely.
++ */
++int utrace_prepare_examine(struct task_struct *target,
++ struct utrace_engine *engine,
++ struct utrace_examiner *exam)
++{
++ int ret = 0;
++
++ if (unlikely(target == current))
++ return 0;
++
++ rcu_read_lock();
++ if (unlikely(!engine_wants_stop(engine)))
++ ret = -EINVAL;
++ else if (unlikely(target->exit_state))
++ ret = -ESRCH;
++ else {
++ exam->state = target->state;
++ if (unlikely(exam->state == TASK_RUNNING))
++ ret = -EAGAIN;
++ else
++ get_task_struct(target);
++ }
++ rcu_read_unlock();
++
++ if (likely(!ret)) {
++ exam->ncsw = wait_task_inactive(target, exam->state);
++ put_task_struct(target);
++ if (unlikely(!exam->ncsw))
++ ret = -EAGAIN;
++ }
++
++ return ret;
++}
++EXPORT_SYMBOL_GPL(utrace_prepare_examine);
++
++/**
++ * utrace_finish_examine - complete an examination of thread state
++ * @target: thread of interest, a &struct task_struct pointer
++ * @engine: engine pointer returned by utrace_attach_task()
++ * @exam: pointer passed to utrace_prepare_examine() call
++ *
++ * This call completes an examination on the thread @target begun by a
++ * paired utrace_prepare_examine() call with the same arguments that
++ * returned success (zero).
++ *
++ * When @target is current, this call is superfluous. When @target is
++ * another thread, this returns zero if @target has remained unscheduled
++ * since the paired utrace_prepare_examine() call returned zero.
++ *
++ * When this returns an error, any examination done since the paired
++ * utrace_prepare_examine() call is unreliable and the data extracted
++ * should be discarded. The error is -%EINVAL if @engine is not
++ * keeping @target stopped, or -%EAGAIN if @target woke up unexpectedly.
++ */
++int utrace_finish_examine(struct task_struct *target,
++ struct utrace_engine *engine,
++ struct utrace_examiner *exam)
++{
++ int ret = 0;
++
++ if (unlikely(target == current))
++ return 0;
++
++ rcu_read_lock();
++ if (unlikely(!engine_wants_stop(engine)))
++ ret = -EINVAL;
++ else if (unlikely(target->state != exam->state))
++ ret = -EAGAIN;
++ else
++ get_task_struct(target);
++ rcu_read_unlock();
++
++ if (likely(!ret)) {
++ unsigned long ncsw = wait_task_inactive(target, exam->state);
++ if (unlikely(ncsw != exam->ncsw))
++ ret = -EAGAIN;
++ put_task_struct(target);
++ }
++
++ return ret;
++}
++EXPORT_SYMBOL_GPL(utrace_finish_examine);
++
++/*
++ * This is declared in linux/regset.h and defined in machine-dependent
++ * code. We put the export here to ensure no machine forgets it.
++ */
++EXPORT_SYMBOL_GPL(task_user_regset_view);
++
++/*
++ * Called with rcu_read_lock() held.
++ */
++void task_utrace_proc_status(struct seq_file *m, struct task_struct *p)
++{
++ seq_printf(m, "Utrace:\t%lx\n", p->utrace_flags);
++}
+--
+1.5.5.1
+
+
+From davej Thu Jun 30 20:27:04 2011
+Return-Path: oleg at redhat.com
+X-Spam-Checker-Version: SpamAssassin 3.3.2 (2011-06-06) on
+ gelk.kernelslacker.org
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+Received: from mail.corp.redhat.com [10.5.5.51]
+ by gelk with IMAP (fetchmail-6.3.20)
+ for <davej at localhost> (single-drop); Thu, 30 Jun 2011 20:27:04 -0400 (EDT)
+Received: from zmta03.collab.prod.int.phx2.redhat.com (LHLO
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+Received: from localhost (localhost.localdomain [127.0.0.1])
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+ oleg at redhat.com; Fri, 1 Jul 2011 02:21:03 +0200 (CEST)
+Date: Fri, 1 Jul 2011 02:21:01 +0200
+From: Oleg Nesterov <oleg at redhat.com>
+To: "Frank Ch. Eigler" <fche at redhat.com>, Kyle McMartin <kmcmartin at redhat.com>,
+ Dave Jones <davej at redhat.com>, Josh Stone <jistone at redhat.com>,
+ Matthew Garrett <mjg at redhat.com>, David Smith <dsmith at redhat.com>
+Cc: kernel at lists.fedoraproject.org, utrace-devel at redhat.com
+Subject: [PATCH 02/19] utrace: remove jobctl bits
+Message-ID: <20110701002101.GA25779 at redhat.com>
+MIME-Version: 1.0
+Content-Type: text/plain; charset=us-ascii
+Content-Disposition: inline
+User-Agent: Mutt/1.5.18 (2008-05-17)
+X-Scanned-By: MIMEDefang 2.67 on 10.5.11.12
+Status: RO
+Content-Length: 1890
+Lines: 56
+
+- change utrace_get_signal() to check GROUP_STOP_PENDING instead of
+ signal->group_stop_count. With the recent changes group_stop_count
+ doesn't necessarily mean this task should participate in group stop.
+
+- remove the "participate in group stop" code from utrace_wakeup() and
+ utrace_stop(), this is no longer needed and wrong.
+
+Signed-off-by: Oleg Nesterov <oleg at redhat.com>
+---
+ kernel/utrace.c | 16 ++--------------
+ 1 files changed, 2 insertions(+), 14 deletions(-)
+
+diff --git a/kernel/utrace.c b/kernel/utrace.c
+index f332d65..6e7fafb 100644
+--- a/kernel/utrace.c
++++ b/kernel/utrace.c
+@@ -648,11 +648,7 @@ static void utrace_wakeup(struct task_struct *target, struct utrace *utrace)
+ {
+ lockdep_assert_held(&utrace->lock);
+ spin_lock_irq(&target->sighand->siglock);
+- if (target->signal->flags & SIGNAL_STOP_STOPPED ||
+- target->signal->group_stop_count)
+- target->state = TASK_STOPPED;
+- else
+- wake_up_state(target, __TASK_TRACED);
++ wake_up_state(target, __TASK_TRACED);
+ spin_unlock_irq(&target->sighand->siglock);
+ }
+
+@@ -805,14 +801,6 @@ relock:
+
+ __set_current_state(TASK_TRACED);
+
+- /*
+- * If there is a group stop in progress,
+- * we must participate in the bookkeeping.
+- */
+- if (unlikely(task->signal->group_stop_count) &&
+- !--task->signal->group_stop_count)
+- task->signal->flags = SIGNAL_STOP_STOPPED;
+-
+ spin_unlock_irq(&task->sighand->siglock);
+ spin_unlock(&utrace->lock);
+
+@@ -2036,7 +2024,7 @@ int utrace_get_signal(struct task_struct *task, struct pt_regs *regs,
+ ka = NULL;
+ memset(return_ka, 0, sizeof *return_ka);
+ } else if (!(task->utrace_flags & UTRACE_EVENT_SIGNAL_ALL) ||
+- unlikely(task->signal->group_stop_count)) {
++ unlikely(task->group_stop & GROUP_STOP_PENDING)) {
+ /*
+ * If no engine is interested in intercepting signals or
+ * we must stop, let the caller just dequeue them normally
+--
+1.5.5.1
+
+
+From davej Thu Jun 30 20:27:05 2011
+Return-Path: oleg at redhat.com
+X-Spam-Checker-Version: SpamAssassin 3.3.2 (2011-06-06) on
+ gelk.kernelslacker.org
+X-Spam-Level:
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+ oleg at redhat.com; Fri, 1 Jul 2011 02:21:06 +0200 (CEST)
+Date: Fri, 1 Jul 2011 02:21:04 +0200
+From: Oleg Nesterov <oleg at redhat.com>
+To: "Frank Ch. Eigler" <fche at redhat.com>, Kyle McMartin <kmcmartin at redhat.com>,
+ Dave Jones <davej at redhat.com>, Josh Stone <jistone at redhat.com>,
+ Matthew Garrett <mjg at redhat.com>, David Smith <dsmith at redhat.com>
+Cc: kernel at lists.fedoraproject.org, utrace-devel at redhat.com
+Subject: [PATCH 03/19] ptrace: take ->siglock around s/TRACED/RUNNING/
+Message-ID: <20110701002104.GA25787 at redhat.com>
+MIME-Version: 1.0
+Content-Type: text/plain; charset=us-ascii
+Content-Disposition: inline
+User-Agent: Mutt/1.5.18 (2008-05-17)
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+Lines: 56
+
+change ptrace_resume() and ptrace_stop() to take ->siglock around changing
+task->state from TRACED to RUNNING.
+
+With this patch __TASK_TRACED/STOPPED bits are fully protected by ->siglock,
+nobody can set or clear these bits without ->siglock held.
+
+Signed-off-by: Oleg Nesterov <oleg at redhat.com>
+---
+ kernel/ptrace.c | 8 +++++++-
+ kernel/signal.c | 3 +++
+ 2 files changed, 10 insertions(+), 1 deletions(-)
+
+diff --git a/kernel/ptrace.c b/kernel/ptrace.c
+index 2df1157..9988b13 100644
+--- a/kernel/ptrace.c
++++ b/kernel/ptrace.c
+@@ -534,6 +534,8 @@ static int ptrace_setsiginfo(struct task_struct *child, const siginfo_t *info)
+ static int ptrace_resume(struct task_struct *child, long request,
+ unsigned long data)
+ {
++ unsigned long flags;
++
+ if (!valid_signal(data))
+ return -EIO;
+
+@@ -562,7 +564,11 @@ static int ptrace_resume(struct task_struct *child, long request,
+ }
+
+ child->exit_code = data;
+- wake_up_state(child, __TASK_TRACED);
++
++ if (lock_task_sighand(child, &flags)) {
++ wake_up_state(child, __TASK_TRACED);
++ unlock_task_sighand(child, &flags);
++ }
+
+ return 0;
+ }
+diff --git a/kernel/signal.c b/kernel/signal.c
+index ff76786..2138cee 100644
+--- a/kernel/signal.c
++++ b/kernel/signal.c
+@@ -1799,7 +1799,10 @@ static void ptrace_stop(int exit_code, int why, int clear_code, siginfo_t *info)
+ if (gstop_done)
+ do_notify_parent_cldstop(current, false, why);
+
++ spin_lock_irq(¤t->sighand->siglock);
+ __set_current_state(TASK_RUNNING);
++ spin_unlock_irq(¤t->sighand->siglock);
++
+ if (clear_code)
+ current->exit_code = 0;
+ read_unlock(&tasklist_lock);
+--
+1.5.5.1
+
+
+From davej Thu Jun 30 20:27:06 2011
+Return-Path: oleg at redhat.com
+X-Spam-Checker-Version: SpamAssassin 3.3.2 (2011-06-06) on
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+ oleg at redhat.com; Fri, 1 Jul 2011 02:21:10 +0200 (CEST)
+Date: Fri, 1 Jul 2011 02:21:07 +0200
+From: Oleg Nesterov <oleg at redhat.com>
+To: "Frank Ch. Eigler" <fche at redhat.com>, Kyle McMartin <kmcmartin at redhat.com>,
+ Dave Jones <davej at redhat.com>, Josh Stone <jistone at redhat.com>,
+ Matthew Garrett <mjg at redhat.com>, David Smith <dsmith at redhat.com>
+Cc: kernel at lists.fedoraproject.org, utrace-devel at redhat.com
+Subject: [PATCH 04/19] introduce wake_up_quiescent()
+Message-ID: <20110701002107.GA25790 at redhat.com>
+MIME-Version: 1.0
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+Lines: 93
+
+No functional changes. Add the new helper, wake_up_quiescent(task, state),
+which simply returns wake_up_state(task, state). Change all callers which
+do wake_up_state(STOPPED/TRACED) to use the new helper. ptrace_stop() is
+a bit special, it does __set_current_state(RUNNING) in the very unlikely
+case, change it as well.
+
+Signed-off-by: Oleg Nesterov <oleg at redhat.com>
+---
+ include/linux/signal.h | 2 ++
+ kernel/ptrace.c | 2 +-
+ kernel/signal.c | 12 ++++++++++--
+ kernel/utrace.c | 2 +-
+ 4 files changed, 14 insertions(+), 4 deletions(-)
+
+diff --git a/include/linux/signal.h b/include/linux/signal.h
+index a822300..2be3712 100644
+--- a/include/linux/signal.h
++++ b/include/linux/signal.h
+@@ -239,6 +239,8 @@ static inline int valid_signal(unsigned long sig)
+ struct timespec;
+ struct pt_regs;
+
++extern int wake_up_quiescent(struct task_struct *p, unsigned int state);
++
+ extern int next_signal(struct sigpending *pending, sigset_t *mask);
+ extern int do_send_sig_info(int sig, struct siginfo *info,
+ struct task_struct *p, bool group);
+diff --git a/kernel/ptrace.c b/kernel/ptrace.c
+index 9988b13..26ae214 100644
+--- a/kernel/ptrace.c
++++ b/kernel/ptrace.c
+@@ -566,7 +566,7 @@ static int ptrace_resume(struct task_struct *child, long request,
+ child->exit_code = data;
+
+ if (lock_task_sighand(child, &flags)) {
+- wake_up_state(child, __TASK_TRACED);
++ wake_up_quiescent(child, __TASK_TRACED);
+ unlock_task_sighand(child, &flags);
+ }
+
+diff --git a/kernel/signal.c b/kernel/signal.c
+index 2138cee..4fcf1c7 100644
+--- a/kernel/signal.c
++++ b/kernel/signal.c
+@@ -652,6 +652,14 @@ void signal_wake_up(struct task_struct *t, int resume)
+ }
+
+ /*
++ * wakes up the STOPPED/TRACED task, must be called with ->siglock held.
++ */
++int wake_up_quiescent(struct task_struct *p, unsigned int state)
++{
++ return wake_up_state(p, state);
++}
++
++/*
+ * Remove signals in mask from the pending set and queue.
+ * Returns 1 if any signals were found.
+ *
+@@ -811,7 +819,7 @@ static int prepare_signal(int sig, struct task_struct *p, int from_ancestor_ns)
+ do {
+ task_clear_group_stop_pending(t);
+ rm_from_queue(SIG_KERNEL_STOP_MASK, &t->pending);
+- wake_up_state(t, __TASK_STOPPED);
++ wake_up_quiescent(t, __TASK_STOPPED);
+ } while_each_thread(p, t);
+
+ /*
+@@ -1800,7 +1808,7 @@ static void ptrace_stop(int exit_code, int why, int clear_code, siginfo_t *info)
+ do_notify_parent_cldstop(current, false, why);
+
+ spin_lock_irq(¤t->sighand->siglock);
+- __set_current_state(TASK_RUNNING);
++ wake_up_quiescent(current, __TASK_TRACED);
+ spin_unlock_irq(¤t->sighand->siglock);
+
+ if (clear_code)
+diff --git a/kernel/utrace.c b/kernel/utrace.c
+index 6e7fafb..d7c547c 100644
+--- a/kernel/utrace.c
++++ b/kernel/utrace.c
+@@ -648,7 +648,7 @@ static void utrace_wakeup(struct task_struct *target, struct utrace *utrace)
+ {
+ lockdep_assert_held(&utrace->lock);
+ spin_lock_irq(&target->sighand->siglock);
+- wake_up_state(target, __TASK_TRACED);
++ wake_up_quiescent(target, __TASK_TRACED);
+ spin_unlock_irq(&target->sighand->siglock);
+ }
+
+--
+1.5.5.1
+
+
+From davej Thu Jun 30 20:27:07 2011
+Return-Path: oleg at redhat.com
+X-Spam-Checker-Version: SpamAssassin 3.3.2 (2011-06-06) on
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+ oleg at redhat.com; Fri, 1 Jul 2011 02:21:13 +0200 (CEST)
+Date: Fri, 1 Jul 2011 02:21:11 +0200
+From: Oleg Nesterov <oleg at redhat.com>
+To: "Frank Ch. Eigler" <fche at redhat.com>, Kyle McMartin <kmcmartin at redhat.com>,
+ Dave Jones <davej at redhat.com>, Josh Stone <jistone at redhat.com>,
+ Matthew Garrett <mjg at redhat.com>, David Smith <dsmith at redhat.com>
+Cc: kernel at lists.fedoraproject.org, utrace-devel at redhat.com
+Subject: [PATCH 05/19] introduce ptrace_signal_wake_up()
+Message-ID: <20110701002111.GA25797 at redhat.com>
+MIME-Version: 1.0
+Content-Type: text/plain; charset=us-ascii
+Content-Disposition: inline
+User-Agent: Mutt/1.5.18 (2008-05-17)
+X-Scanned-By: MIMEDefang 2.67 on 10.5.11.12
+Status: RO
+Content-Length: 1975
+Lines: 68
+
+Add the new helper, ptrace_signal_wake_up(), change ptrace.c to use
+it instead of signal_wake_up().
+
+The new helper does almost the same, except:
+
+ - it doesn't use the TASK_WAKEKILL bit to wake up the TRACED
+ or STOPPED task, it uses __TASK_STOPPED | __TASK_TRACED
+ explicitly. This is what ptrace actually wants, it should
+ never wake up a TASK_KILLABLE task.
+
+ This should be cleanuped upatream, signal_wake_up() should
+ take the state as an argument, not a boolean. Until then
+ we add a new static helper.
+
+ - it uses wake_up_quiescent() instead of wake_up_state().
+
+Thereafter every change from STOPPED/TRACED to RUNNING is done via
+wake_up_quiescent().
+
+Signed-off-by: Oleg Nesterov <oleg at redhat.com>
+---
+ kernel/ptrace.c | 16 ++++++++++++++--
+ 1 files changed, 14 insertions(+), 2 deletions(-)
+
+diff --git a/kernel/ptrace.c b/kernel/ptrace.c
+index 26ae214..0b2aba5 100644
+--- a/kernel/ptrace.c
++++ b/kernel/ptrace.c
+@@ -24,6 +24,18 @@
+ #include <linux/regset.h>
+ #include <linux/hw_breakpoint.h>
+
++static void ptrace_signal_wake_up(struct task_struct *p, int quiescent)
++{
++ unsigned int state;
++
++ set_tsk_thread_flag(p, TIF_SIGPENDING);
++
++ state = TASK_INTERRUPTIBLE;
++ if (quiescent)
++ state |= (__TASK_STOPPED | __TASK_TRACED);
++ if (!wake_up_quiescent(p, state))
++ kick_process(p);
++}
+
+ /*
+ * ptrace a task: make the debugger its new parent and
+@@ -92,7 +104,7 @@ void __ptrace_unlink(struct task_struct *child)
+ * TASK_KILLABLE sleeps.
+ */
+ if (child->group_stop & GROUP_STOP_PENDING || task_is_traced(child))
+- signal_wake_up(child, task_is_traced(child));
++ ptrace_signal_wake_up(child, task_is_traced(child));
+
+ spin_unlock(&child->sighand->siglock);
+ }
+@@ -245,7 +257,7 @@ static int ptrace_attach(struct task_struct *task)
+ */
+ if (task_is_stopped(task)) {
+ task->group_stop |= GROUP_STOP_PENDING | GROUP_STOP_TRAPPING;
+- signal_wake_up(task, 1);
++ ptrace_signal_wake_up(task, 1);
+ wait_trap = true;
+ }
+
+--
+1.5.5.1
+
+
+From davej Thu Jun 30 20:27:08 2011
+Return-Path: oleg at redhat.com
+X-Spam-Checker-Version: SpamAssassin 3.3.2 (2011-06-06) on
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+ oleg at redhat.com; Fri, 1 Jul 2011 02:21:16 +0200 (CEST)
+Date: Fri, 1 Jul 2011 02:21:14 +0200
+From: Oleg Nesterov <oleg at redhat.com>
+To: "Frank Ch. Eigler" <fche at redhat.com>, Kyle McMartin <kmcmartin at redhat.com>,
+ Dave Jones <davej at redhat.com>, Josh Stone <jistone at redhat.com>,
+ Matthew Garrett <mjg at redhat.com>, David Smith <dsmith at redhat.com>
+Cc: kernel at lists.fedoraproject.org, utrace-devel at redhat.com
+Subject: [PATCH 06/19] wait_task_inactive: treat task->state and
+ match_state as bitmasks
+Message-ID: <20110701002114.GA25804 at redhat.com>
+MIME-Version: 1.0
+Content-Type: text/plain; charset=us-ascii
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+User-Agent: Mutt/1.5.18 (2008-05-17)
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+Lines: 39
+
+Change wait_task_inactive() to check "state & match_state" instead of
+"state == match_state". This should not make any difference, but this
+allows us to add more "stopped" bits which can be set or cleared
+independently.
+
+IOW. wait_task_inactive() assumes that if task->state != 0, it can
+only be changed to TASK_RUNNING. Currently this is true, and in this
+case "state & match_state" continues to work. But, unlike the current
+check, it also works if task->state has other bits set while the caller
+is only interested in, say, __TASK_TRACED.
+
+Note: I think wait_task_inactive() should be cleanuped upstrean anyway,
+nowadays we have TASK_WAKING and task->state != 0 doesn't necessarily
+mean it is TASK_RUNNING. It also makes sense to exclude the !TASK_REPORT
+bits during the check. Finally, probably this patch makes sense anyway
+even without utrace. For example, a stopped _and_ traced thread could
+have task->state = TASK_STOPPED | TASK_TRACED, this can be useful.
+
+Signed-off-by: Oleg Nesterov <oleg at redhat.com>
+---
+ kernel/sched.c | 2 +-
+ 1 files changed, 1 insertions(+), 1 deletions(-)
+
+diff --git a/kernel/sched.c b/kernel/sched.c
+index 3f2e502..ade7997 100644
+--- a/kernel/sched.c
++++ b/kernel/sched.c
+@@ -2277,7 +2277,7 @@ unsigned long wait_task_inactive(struct task_struct *p, long match_state)
+ * is actually now running somewhere else!
+ */
+ while (task_running(rq, p)) {
+- if (match_state && unlikely(p->state != match_state))
++ if (match_state && !likely(p->state & match_state))
+ return 0;
+ cpu_relax();
+ }
+--
+1.5.5.1
+
+
+From davej Thu Jun 30 20:27:09 2011
+Return-Path: oleg at redhat.com
+X-Spam-Checker-Version: SpamAssassin 3.3.2 (2011-06-06) on
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+ oleg at redhat.com; Fri, 1 Jul 2011 02:21:19 +0200 (CEST)
+Date: Fri, 1 Jul 2011 02:21:17 +0200
+From: Oleg Nesterov <oleg at redhat.com>
+To: "Frank Ch. Eigler" <fche at redhat.com>, Kyle McMartin <kmcmartin at redhat.com>,
+ Dave Jones <davej at redhat.com>, Josh Stone <jistone at redhat.com>,
+ Matthew Garrett <mjg at redhat.com>, David Smith <dsmith at redhat.com>
+Cc: kernel at lists.fedoraproject.org, utrace-devel at redhat.com
+Subject: [PATCH 07/19] introduce TASK_UTRACED state
+Message-ID: <20110701002117.GA25807 at redhat.com>
+MIME-Version: 1.0
+Content-Type: text/plain; charset=us-ascii
+Content-Disposition: inline
+User-Agent: Mutt/1.5.18 (2008-05-17)
+X-Scanned-By: MIMEDefang 2.67 on 10.5.11.11
+Status: RO
+Content-Length: 2913
+Lines: 84
+
+Introduce TASK_UTRACED state, will be used by utrace instead of TASK_TRACED.
+
+Note: this state is reported as "t (tracing stop)" to the user-space to
+avoid the confusion. IOW, it looks like TASK_TRACED in /proc/pid/status.
+
+Signed-off-by: Oleg Nesterov <oleg at redhat.com>
+---
+ fs/proc/array.c | 11 ++++++-----
+ include/linux/sched.h | 20 +++++++++++---------
+ 2 files changed, 17 insertions(+), 14 deletions(-)
+
+diff --git a/fs/proc/array.c b/fs/proc/array.c
+index 496fef3..bfaa998 100644
+--- a/fs/proc/array.c
++++ b/fs/proc/array.c
+@@ -138,11 +138,12 @@ static const char * const task_state_array[] = {
+ "D (disk sleep)", /* 2 */
+ "T (stopped)", /* 4 */
+ "t (tracing stop)", /* 8 */
+- "Z (zombie)", /* 16 */
+- "X (dead)", /* 32 */
+- "x (dead)", /* 64 */
+- "K (wakekill)", /* 128 */
+- "W (waking)", /* 256 */
++ "t (tracing stop)", /* 16 (stopped by utrace) */
++ "Z (zombie)", /* 32 */
++ "X (dead)", /* 64 */
++ "x (dead)", /* 128 */
++ "K (wakekill)", /* 256 */
++ "W (waking)", /* 512 */
+ };
+
+ static inline const char *get_task_state(struct task_struct *tsk)
+diff --git a/include/linux/sched.h b/include/linux/sched.h
+index b87de83..7a0008c 100644
+--- a/include/linux/sched.h
++++ b/include/linux/sched.h
+@@ -184,16 +184,17 @@ print_cfs_rq(struct seq_file *m, int cpu, struct cfs_rq *cfs_rq)
+ #define TASK_UNINTERRUPTIBLE 2
+ #define __TASK_STOPPED 4
+ #define __TASK_TRACED 8
++#define __TASK_UTRACED 16
+ /* in tsk->exit_state */
+-#define EXIT_ZOMBIE 16
+-#define EXIT_DEAD 32
++#define EXIT_ZOMBIE 32
++#define EXIT_DEAD 64
+ /* in tsk->state again */
+-#define TASK_DEAD 64
+-#define TASK_WAKEKILL 128
+-#define TASK_WAKING 256
+-#define TASK_STATE_MAX 512
++#define TASK_DEAD 128
++#define TASK_WAKEKILL 256
++#define TASK_WAKING 512
++#define TASK_STATE_MAX 1024
+
+-#define TASK_STATE_TO_CHAR_STR "RSDTtZXxKW"
++#define TASK_STATE_TO_CHAR_STR "RSDTtUZXxKW"
+
+ extern char ___assert_task_state[1 - 2*!!(
+ sizeof(TASK_STATE_TO_CHAR_STR)-1 != ilog2(TASK_STATE_MAX)+1)];
+@@ -202,15 +203,16 @@ extern char ___assert_task_state[1 - 2*!!(
+ #define TASK_KILLABLE (TASK_WAKEKILL | TASK_UNINTERRUPTIBLE)
+ #define TASK_STOPPED (TASK_WAKEKILL | __TASK_STOPPED)
+ #define TASK_TRACED (TASK_WAKEKILL | __TASK_TRACED)
++#define TASK_UTRACED (TASK_WAKEKILL | __TASK_UTRACED)
+
+ /* Convenience macros for the sake of wake_up */
+ #define TASK_NORMAL (TASK_INTERRUPTIBLE | TASK_UNINTERRUPTIBLE)
+-#define TASK_ALL (TASK_NORMAL | __TASK_STOPPED | __TASK_TRACED)
++#define TASK_ALL (TASK_NORMAL | __TASK_STOPPED | __TASK_TRACED | __TASK_UTRACED)
+
+ /* get_task_state() */
+ #define TASK_REPORT (TASK_RUNNING | TASK_INTERRUPTIBLE | \
+ TASK_UNINTERRUPTIBLE | __TASK_STOPPED | \
+- __TASK_TRACED)
++ __TASK_TRACED | __TASK_UTRACED)
+
+ #define task_is_traced(task) ((task->state & __TASK_TRACED) != 0)
+ #define task_is_stopped(task) ((task->state & __TASK_STOPPED) != 0)
+--
+1.5.5.1
+
+
+From davej Thu Jun 30 20:27:10 2011
+Return-Path: oleg at redhat.com
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+ oleg at redhat.com; Fri, 1 Jul 2011 02:21:23 +0200 (CEST)
+Date: Fri, 1 Jul 2011 02:21:20 +0200
+From: Oleg Nesterov <oleg at redhat.com>
+To: "Frank Ch. Eigler" <fche at redhat.com>, Kyle McMartin <kmcmartin at redhat.com>,
+ Dave Jones <davej at redhat.com>, Josh Stone <jistone at redhat.com>,
+ Matthew Garrett <mjg at redhat.com>, David Smith <dsmith at redhat.com>
+Cc: kernel at lists.fedoraproject.org, utrace-devel at redhat.com
+Subject: [PATCH 08/19] utrace: use TASK_UTRACED instead of TASK_TRACED
+Message-ID: <20110701002120.GA25814 at redhat.com>
+MIME-Version: 1.0
+Content-Type: text/plain; charset=us-ascii
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+User-Agent: Mutt/1.5.18 (2008-05-17)
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+
+Change utrace.c to use TASK_UTRACED instead of TASK_TRACED.
+
+- utrace_stop/utrace_wakeup: simply use the new state
+
+- utrace_do_stop: do not clear STOPPED/TRACED, but add the new
+ __TASK_UTRACED bit to state the fact that both ptrace and utrace
+ want this task to be stopped
+
+- naturally, do not use task_is_traced() to check if this task was
+ stopped by utrace, use the new task_is_utraced() helper which
+ checks __TASK_UTRACED.
+
+Signed-off-by: Oleg Nesterov <oleg at redhat.com>
+---
+ kernel/utrace.c | 26 ++++++++++++++------------
+ 1 files changed, 14 insertions(+), 12 deletions(-)
+
+diff --git a/kernel/utrace.c b/kernel/utrace.c
+index d7c547c..be98607 100644
+--- a/kernel/utrace.c
++++ b/kernel/utrace.c
+@@ -462,6 +462,8 @@ static void put_detached_list(struct list_head *list)
+ */
+ #define ENGINE_STOP (1UL << _UTRACE_NEVENTS)
+
++#define task_is_utraced(task) ((task->state & __TASK_UTRACED) != 0)
++
+ static void mark_engine_wants_stop(struct task_struct *task,
+ struct utrace_engine *engine)
+ {
+@@ -576,7 +578,7 @@ int utrace_set_events(struct task_struct *target,
+
+ ret = 0;
+ if ((old_flags & ~events) && target != current &&
+- !task_is_stopped_or_traced(target) && !target->exit_state) {
++ !task_is_utraced(target) && !target->exit_state) {
+ /*
+ * This barrier ensures that our engine->flags changes
+ * have hit before we examine utrace->reporting,
+@@ -623,21 +625,21 @@ static void mark_engine_detached(struct utrace_engine *engine)
+ */
+ static bool utrace_do_stop(struct task_struct *target, struct utrace *utrace)
+ {
+- if (task_is_stopped(target)) {
++ if (task_is_stopped_or_traced(target)) {
+ /*
+ * Stopped is considered quiescent; when it wakes up, it will
+ * go through utrace_finish_stop() before doing anything else.
+ */
+ spin_lock_irq(&target->sighand->siglock);
+- if (likely(task_is_stopped(target)))
+- __set_task_state(target, TASK_TRACED);
++ if (likely(task_is_stopped_or_traced(target)))
++ target->state |= TASK_UTRACED;
+ spin_unlock_irq(&target->sighand->siglock);
+ } else if (utrace->resume > UTRACE_REPORT) {
+ utrace->resume = UTRACE_REPORT;
+ set_notify_resume(target);
+ }
+
+- return task_is_traced(target);
++ return task_is_utraced(target);
+ }
+
+ /*
+@@ -648,7 +650,7 @@ static void utrace_wakeup(struct task_struct *target, struct utrace *utrace)
+ {
+ lockdep_assert_held(&utrace->lock);
+ spin_lock_irq(&target->sighand->siglock);
+- wake_up_quiescent(target, __TASK_TRACED);
++ wake_up_quiescent(target, __TASK_UTRACED);
+ spin_unlock_irq(&target->sighand->siglock);
+ }
+
+@@ -710,7 +712,7 @@ static bool utrace_reset(struct task_struct *task, struct utrace *utrace)
+ /*
+ * If no more engines want it stopped, wake it up.
+ */
+- if (task_is_traced(task) && !(flags & ENGINE_STOP)) {
++ if (task_is_utraced(task) && !(flags & ENGINE_STOP)) {
+ /*
+ * It just resumes, so make sure single-step
+ * is not left set.
+@@ -749,7 +751,7 @@ void utrace_finish_stop(void)
+ }
+
+ /*
+- * Perform %UTRACE_STOP, i.e. block in TASK_TRACED until woken up.
++ * Perform %UTRACE_STOP, i.e. block in TASK_UTRACED until woken up.
+ * @task == current, @utrace == current->utrace, which is not locked.
+ * Return true if we were woken up by SIGKILL even though some utrace
+ * engine may still want us to stay stopped.
+@@ -799,7 +801,7 @@ relock:
+ return;
+ }
+
+- __set_current_state(TASK_TRACED);
++ __set_current_state(TASK_UTRACED);
+
+ spin_unlock_irq(&task->sighand->siglock);
+ spin_unlock(&utrace->lock);
+@@ -809,14 +811,14 @@ relock:
+ utrace_finish_stop();
+
+ /*
+- * While in TASK_TRACED, we were considered "frozen enough".
++ * While in TASK_UTRACED, we were considered "frozen enough".
+ * Now that we woke up, it's crucial if we're supposed to be
+ * frozen that we freeze now before running anything substantial.
+ */
+ try_to_freeze();
+
+ /*
+- * While we were in TASK_TRACED, complete_signal() considered
++ * While we were in TASK_UTRACED, complete_signal() considered
+ * us "uninterested" in signal wakeups. Now make sure our
+ * TIF_SIGPENDING state is correct for normal running.
+ */
+@@ -1087,7 +1089,7 @@ int utrace_control(struct task_struct *target,
+ if (unlikely(IS_ERR(utrace)))
+ return PTR_ERR(utrace);
+
+- reset = task_is_traced(target);
++ reset = task_is_utraced(target);
+ ret = 0;
+
+ /*
+--
+1.5.5.1
+
+
+From davej Thu Jun 30 20:27:12 2011
+Return-Path: oleg at redhat.com
+X-Spam-Checker-Version: SpamAssassin 3.3.2 (2011-06-06) on
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+ oleg at redhat.com; Fri, 1 Jul 2011 02:21:26 +0200 (CEST)
+Date: Fri, 1 Jul 2011 02:21:24 +0200
+From: Oleg Nesterov <oleg at redhat.com>
+To: "Frank Ch. Eigler" <fche at redhat.com>, Kyle McMartin <kmcmartin at redhat.com>,
+ Dave Jones <davej at redhat.com>, Josh Stone <jistone at redhat.com>,
+ Matthew Garrett <mjg at redhat.com>, David Smith <dsmith at redhat.com>
+Cc: kernel at lists.fedoraproject.org, utrace-devel at redhat.com
+Subject: [PATCH 09/19] tracehooks: kill tracehook_finish_jctl(), add
+ tracehook_finish_stop()
+Message-ID: <20110701002124.GA25817 at redhat.com>
+MIME-Version: 1.0
+Content-Type: text/plain; charset=us-ascii
+Content-Disposition: inline
+User-Agent: Mutt/1.5.18 (2008-05-17)
+X-Scanned-By: MIMEDefang 2.67 on 10.5.11.12
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+Lines: 86
+
+tracehook_finish_jctl() is needed to avoid the races with SIGKILL
+which wakes up UTRACED task, and thus it should be called every time
+after the STOPPED/TRACED/UTRACED returns from schedule(), remember
+that TASK_UTRACED can be added while the task is STOPPED/UTRACED.
+
+- rename it to tracehook_finish_stop(),jctl no longer matches the
+ reality.
+
+- change do_signal_state() to call this helper right after schedule(),
+ otherwise this logic is broken by the upstream changes
+
+- now that utrace doesn't control TASK_TRACED bit, ptrace_stop() must
+ call this helper too.
+
+Signed-off-by: Oleg Nesterov <oleg at redhat.com>
+---
+ include/linux/tracehook.h | 6 +++---
+ kernel/signal.c | 5 +++--
+ kernel/utrace.c | 2 +-
+ 3 files changed, 7 insertions(+), 6 deletions(-)
+
+diff --git a/include/linux/tracehook.h b/include/linux/tracehook.h
+index 7d7bdde..3c7b6b3 100644
+--- a/include/linux/tracehook.h
++++ b/include/linux/tracehook.h
+@@ -528,11 +528,11 @@ static inline int tracehook_get_signal(struct task_struct *task,
+ }
+
+ /**
+- * tracehook_finish_jctl - report about return from job control stop
++ * tracehook_finish_stop - report about return from STOPPED/TRACED
+ *
+- * This is called by do_signal_stop() after wakeup.
++ * This is called by do_signal_stop() and ptrace_stop after wakeup.
+ */
+-static inline void tracehook_finish_jctl(void)
++static inline void tracehook_finish_stop(void)
+ {
+ if (task_utrace_flags(current))
+ utrace_finish_stop();
+diff --git a/kernel/signal.c b/kernel/signal.c
+index 4fcf1c7..a7979ad 100644
+--- a/kernel/signal.c
++++ b/kernel/signal.c
+@@ -1816,6 +1816,7 @@ static void ptrace_stop(int exit_code, int why, int clear_code, siginfo_t *info)
+ read_unlock(&tasklist_lock);
+ }
+
++ tracehook_finish_stop();
+ /*
+ * While in TASK_TRACED, we were considered "frozen enough".
+ * Now that we woke up, it's crucial if we're supposed to be
+@@ -1952,6 +1953,8 @@ retry:
+ /* Now we don't run again until woken by SIGCONT or SIGKILL */
+ schedule();
+
++ tracehook_finish_stop();
++
+ spin_lock_irq(¤t->sighand->siglock);
+ } else {
+ ptrace_stop(current->group_stop & GROUP_STOP_SIGMASK,
+@@ -1974,8 +1977,6 @@ retry:
+
+ spin_unlock_irq(¤t->sighand->siglock);
+
+- tracehook_finish_jctl();
+-
+ return 1;
+ }
+
+diff --git a/kernel/utrace.c b/kernel/utrace.c
+index be98607..daa96b9 100644
+--- a/kernel/utrace.c
++++ b/kernel/utrace.c
+@@ -741,7 +741,7 @@ static bool utrace_reset(struct task_struct *task, struct utrace *utrace)
+ void utrace_finish_stop(void)
+ {
+ /*
+- * If we were task_is_traced() and then SIGKILL'ed, make
++ * If we were task_is_utraced() and then SIGKILL'ed, make
+ * sure we do nothing until the tracer drops utrace->lock.
+ */
+ if (unlikely(__fatal_signal_pending(current))) {
+--
+1.5.5.1
+
+
+From davej Thu Jun 30 20:27:13 2011
+Return-Path: oleg at redhat.com
+X-Spam-Checker-Version: SpamAssassin 3.3.2 (2011-06-06) on
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+ oleg at redhat.com; Fri, 1 Jul 2011 02:21:29 +0200 (CEST)
+Date: Fri, 1 Jul 2011 02:21:27 +0200
+From: Oleg Nesterov <oleg at redhat.com>
+To: "Frank Ch. Eigler" <fche at redhat.com>, Kyle McMartin <kmcmartin at redhat.com>,
+ Dave Jones <davej at redhat.com>, Josh Stone <jistone at redhat.com>,
+ Matthew Garrett <mjg at redhat.com>, David Smith <dsmith at redhat.com>
+Cc: kernel at lists.fedoraproject.org, utrace-devel at redhat.com
+Subject: [PATCH 10/19] teach wake_up_quiescent() to do "selective" wake_up
+Message-ID: <20110701002127.GA25824 at redhat.com>
+MIME-Version: 1.0
+Content-Type: text/plain; charset=us-ascii
+Content-Disposition: inline
+User-Agent: Mutt/1.5.18 (2008-05-17)
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+
+Both utrace and ptrace can want the same thread to be quiescent, in this
+case its state is TASK_TRACED | TASK_UTRACED. And this also means that
+this task must not run unless both utrace and ptrace resume it.
+
+Change wake_up_quiescent(p, state) to do "p->state &= ~state" and return
+false unless there is no more "quiescent" bits in task->state.
+
+Signed-off-by: Oleg Nesterov <oleg at redhat.com>
+---
+ kernel/signal.c | 15 +++++++++++++++
+ 1 files changed, 15 insertions(+), 0 deletions(-)
+
+diff --git a/kernel/signal.c b/kernel/signal.c
+index a7979ad..57552e6 100644
+--- a/kernel/signal.c
++++ b/kernel/signal.c
+@@ -651,11 +651,26 @@ void signal_wake_up(struct task_struct *t, int resume)
+ kick_process(t);
+ }
+
++#define STATE_QUIESCENT (__TASK_STOPPED | __TASK_TRACED | __TASK_UTRACED)
+ /*
+ * wakes up the STOPPED/TRACED task, must be called with ->siglock held.
+ */
+ int wake_up_quiescent(struct task_struct *p, unsigned int state)
+ {
++ unsigned int quiescent = (p->state & STATE_QUIESCENT);
++
++ WARN_ON(state & ~(STATE_QUIESCENT | TASK_INTERRUPTIBLE));
++
++ if (quiescent) {
++ state &= ~TASK_INTERRUPTIBLE;
++ if ((quiescent & ~state) != 0) {
++ p->state &= ~state;
++ WARN_ON(!(p->state & STATE_QUIESCENT));
++ WARN_ON(!(p->state & TASK_WAKEKILL));
++ return 0;
++ }
++ }
++
+ return wake_up_state(p, state);
+ }
+
+--
+1.5.5.1
+
+
+From davej Thu Jun 30 20:27:14 2011
+Return-Path: oleg at redhat.com
+X-Spam-Checker-Version: SpamAssassin 3.3.2 (2011-06-06) on
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+ oleg at redhat.com; Fri, 1 Jul 2011 02:21:33 +0200 (CEST)
+Date: Fri, 1 Jul 2011 02:21:30 +0200
+From: Oleg Nesterov <oleg at redhat.com>
+To: "Frank Ch. Eigler" <fche at redhat.com>, Kyle McMartin <kmcmartin at redhat.com>,
+ Dave Jones <davej at redhat.com>, Josh Stone <jistone at redhat.com>,
+ Matthew Garrett <mjg at redhat.com>, David Smith <dsmith at redhat.com>
+Cc: kernel at lists.fedoraproject.org, utrace-devel at redhat.com
+Subject: [PATCH 11/19] ptrace_stop: do not assume the task is running after
+ wake_up_quiescent()
+Message-ID: <20110701002130.GA25827 at redhat.com>
+MIME-Version: 1.0
+Content-Type: text/plain; charset=us-ascii
+Content-Disposition: inline
+User-Agent: Mutt/1.5.18 (2008-05-17)
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+
+If ptrace_stop() sets TASK_TRACED and then detects we should not stop,
+it can race with utrace_do_stop() which can see TASK_TRACED and add
+TASK_UTRACED. In this case we should stop for utrace needs.
+
+Signed-off-by: Oleg Nesterov <oleg at redhat.com>
+---
+ kernel/signal.c | 8 ++++++++
+ 1 files changed, 8 insertions(+), 0 deletions(-)
+
+diff --git a/kernel/signal.c b/kernel/signal.c
+index 57552e6..89e691d 100644
+--- a/kernel/signal.c
++++ b/kernel/signal.c
+@@ -1829,6 +1829,14 @@ static void ptrace_stop(int exit_code, int why, int clear_code, siginfo_t *info)
+ if (clear_code)
+ current->exit_code = 0;
+ read_unlock(&tasklist_lock);
++
++ /*
++ * It is possible that __TASK_UTRACED was added by utrace
++ * while we were __TASK_TRACED and before we take ->siglock
++ * for wake_up_quiescent(), we need to block in this case.
++ * Otherwise this is unnecessary but absolutely harmless.
++ */
++ schedule();
+ }
+
+ tracehook_finish_stop();
+--
+1.5.5.1
+
+
+From davej Thu Jun 30 20:27:17 2011
+Return-Path: oleg at redhat.com
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+ by int-mx12.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with SMTP id p610NSc9032626;
+ Thu, 30 Jun 2011 20:23:29 -0400
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+ oleg at redhat.com; Fri, 1 Jul 2011 02:21:36 +0200 (CEST)
+Date: Fri, 1 Jul 2011 02:21:34 +0200
+From: Oleg Nesterov <oleg at redhat.com>
+To: "Frank Ch. Eigler" <fche at redhat.com>, Kyle McMartin <kmcmartin at redhat.com>,
+ Dave Jones <davej at redhat.com>, Josh Stone <jistone at redhat.com>,
+ Matthew Garrett <mjg at redhat.com>, David Smith <dsmith at redhat.com>
+Cc: kernel at lists.fedoraproject.org, utrace-devel at redhat.com
+Subject: [PATCH 12/19] get_signal_to_deliver: restructure utrace/ptrace
+ signal reporting
+Message-ID: <20110701002134.GA25834 at redhat.com>
+MIME-Version: 1.0
+Content-Type: text/plain; charset=us-ascii
+Content-Disposition: inline
+User-Agent: Mutt/1.5.18 (2008-05-17)
+X-Scanned-By: MIMEDefang 2.68 on 10.5.11.25
+Status: RO
+Content-Length: 2012
+Lines: 73
+
+get_signal_to_deliver() assumes that either tracehook_get_signal() does
+nothing (without CONFIG_UTRACE), or it also reports the signal to ptrace
+engine implemented on top of utrace. Now that ptrace works independently
+this doesn't work.
+
+Change the code to call ptrace_signal() after tracehook_get_signal().
+
+Move ->ptrace check from ptrace_signal() to get_signal_to_deliver(),
+we do not want to change *return_ka if it was initialized by utrace
+and the task is not traced.
+
+IOW, roughly, ptrace acts as if it is the last attached engine, it
+takes the final decision about the signal.
+
+Signed-off-by: Oleg Nesterov <oleg at redhat.com>
+---
+ kernel/signal.c | 24 +++++++++++-------------
+ 1 files changed, 11 insertions(+), 13 deletions(-)
+
+diff --git a/kernel/signal.c b/kernel/signal.c
+index 89e691d..d0e0c67 100644
+--- a/kernel/signal.c
++++ b/kernel/signal.c
+@@ -2006,9 +2006,6 @@ retry:
+ static int ptrace_signal(int signr, siginfo_t *info,
+ struct pt_regs *regs, void *cookie)
+ {
+- if (!task_ptrace(current))
+- return signr;
+-
+ ptrace_signal_deliver(regs, cookie);
+
+ /* Let the debugger run. */
+@@ -2110,6 +2107,7 @@ relock:
+ signr = tracehook_get_signal(current, regs, info, return_ka);
+ if (unlikely(signr < 0))
+ goto relock;
++
+ if (unlikely(signr != 0))
+ ka = return_ka;
+ else {
+@@ -2117,18 +2115,18 @@ relock:
+ GROUP_STOP_PENDING) && do_signal_stop(0))
+ goto relock;
+
+- signr = dequeue_signal(current, ¤t->blocked,
+- info);
++ signr = dequeue_signal(current, ¤t->blocked, info);
+
+- if (!signr)
+- break; /* will return 0 */
++ ka = &sighand->action[signr-1];
++ }
+
+- if (signr != SIGKILL) {
+- signr = ptrace_signal(signr, info,
+- regs, cookie);
+- if (!signr)
+- continue;
+- }
++ if (!signr)
++ break; /* will return 0 */
++
++ if (signr != SIGKILL && current->ptrace) {
++ signr = ptrace_signal(signr, info, regs, cookie);
++ if (!signr)
++ continue;
+
+ ka = &sighand->action[signr-1];
+ }
+--
+1.5.5.1
+
+
+From davej Thu Jun 30 20:27:18 2011
+Return-Path: oleg at redhat.com
+X-Spam-Checker-Version: SpamAssassin 3.3.2 (2011-06-06) on
+ gelk.kernelslacker.org
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+ UNPARSEABLE_RELAY autolearn=ham version=3.3.2
+Received: from mail.corp.redhat.com [10.5.5.51]
+ by gelk with IMAP (fetchmail-6.3.20)
+ for <davej at localhost> (single-drop); Thu, 30 Jun 2011 20:27:18 -0400 (EDT)
+Received: from zmta03.collab.prod.int.phx2.redhat.com (LHLO
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+Received: from localhost (localhost.localdomain [127.0.0.1])
+ by zmta03.collab.prod.int.phx2.redhat.com (Postfix) with ESMTP id 74BDFD813B;
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+ by int-mx12.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with SMTP id p610NWY1032629;
+ Thu, 30 Jun 2011 20:23:32 -0400
+Received: by tranklukator.englab.brq.redhat.com (nbSMTP-1.00) for uid 500
+ oleg at redhat.com; Fri, 1 Jul 2011 02:21:39 +0200 (CEST)
+Date: Fri, 1 Jul 2011 02:21:37 +0200
+From: Oleg Nesterov <oleg at redhat.com>
+To: "Frank Ch. Eigler" <fche at redhat.com>, Kyle McMartin <kmcmartin at redhat.com>,
+ Dave Jones <davej at redhat.com>, Josh Stone <jistone at redhat.com>,
+ Matthew Garrett <mjg at redhat.com>, David Smith <dsmith at redhat.com>
+Cc: kernel at lists.fedoraproject.org, utrace-devel at redhat.com
+Subject: [PATCH 13/19] introduce ptrace_set_syscall_trace()
+Message-ID: <20110701002137.GA25837 at redhat.com>
+MIME-Version: 1.0
+Content-Type: text/plain; charset=us-ascii
+Content-Disposition: inline
+User-Agent: Mutt/1.5.18 (2008-05-17)
+X-Scanned-By: MIMEDefang 2.68 on 10.5.11.25
+Status: RO
+Content-Length: 1581
+Lines: 52
+
+No functional changes. Add the new helper, ptrace_set_syscall_trace(),
+which should be used to set/clear TIF_SYSCALL_TRACE in ptrace code.
+Currently it does nothing more.
+
+Signed-off-by: Oleg Nesterov <oleg at redhat.com>
+---
+ kernel/ptrace.c | 15 ++++++++++-----
+ 1 files changed, 10 insertions(+), 5 deletions(-)
+
+diff --git a/kernel/ptrace.c b/kernel/ptrace.c
+index 0b2aba5..b6fd922 100644
+--- a/kernel/ptrace.c
++++ b/kernel/ptrace.c
+@@ -37,6 +37,14 @@ static void ptrace_signal_wake_up(struct task_struct *p, int quiescent)
+ kick_process(p);
+ }
+
++static void ptrace_set_syscall_trace(struct task_struct *p, bool on)
++{
++ if (on)
++ set_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
++ else
++ clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
++}
++
+ /*
+ * ptrace a task: make the debugger its new parent and
+ * move it to the ptrace list.
+@@ -364,7 +372,7 @@ static int ptrace_detach(struct task_struct *child, unsigned int data)
+
+ /* Architecture-specific hardware disable .. */
+ ptrace_disable(child);
+- clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
++ ptrace_set_syscall_trace(child, false);
+
+ write_lock_irq(&tasklist_lock);
+ /*
+@@ -551,10 +559,7 @@ static int ptrace_resume(struct task_struct *child, long request,
+ if (!valid_signal(data))
+ return -EIO;
+
+- if (request == PTRACE_SYSCALL)
+- set_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
+- else
+- clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
++ ptrace_set_syscall_trace(child, request == PTRACE_SYSCALL);
+
+ #ifdef TIF_SYSCALL_EMU
+ if (request == PTRACE_SYSEMU || request == PTRACE_SYSEMU_SINGLESTEP)
+--
+1.5.5.1
+
+
+From davej Thu Jun 30 20:27:20 2011
+Return-Path: oleg at redhat.com
+X-Spam-Checker-Version: SpamAssassin 3.3.2 (2011-06-06) on
+ gelk.kernelslacker.org
+X-Spam-Level:
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+ UNPARSEABLE_RELAY autolearn=ham version=3.3.2
+Received: from mail.corp.redhat.com [10.5.5.51]
+ by gelk with IMAP (fetchmail-6.3.20)
+ for <davej at localhost> (single-drop); Thu, 30 Jun 2011 20:27:20 -0400 (EDT)
+Received: from zmta01.collab.prod.int.phx2.redhat.com (LHLO
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+ by int-mx09.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with SMTP id p610NZvo015255;
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+ oleg at redhat.com; Fri, 1 Jul 2011 02:21:43 +0200 (CEST)
+Date: Fri, 1 Jul 2011 02:21:40 +0200
+From: Oleg Nesterov <oleg at redhat.com>
+To: "Frank Ch. Eigler" <fche at redhat.com>, Kyle McMartin <kmcmartin at redhat.com>,
+ Dave Jones <davej at redhat.com>, Josh Stone <jistone at redhat.com>,
+ Matthew Garrett <mjg at redhat.com>, David Smith <dsmith at redhat.com>
+Cc: kernel at lists.fedoraproject.org, utrace-devel at redhat.com
+Subject: [PATCH 14/19] introduce PT_SYSCALL_TRACE flag
+Message-ID: <20110701002140.GA25844 at redhat.com>
+MIME-Version: 1.0
+Content-Type: text/plain; charset=us-ascii
+Content-Disposition: inline
+User-Agent: Mutt/1.5.18 (2008-05-17)
+X-Scanned-By: MIMEDefang 2.68 on 10.5.11.22
+Status: RO
+Content-Length: 2236
+Lines: 73
+
+Currently tracehooks assume that if the ptraced task has
+TIF_SYSCALL_TRACE set, the tracee should report the syscall.
+This is not true, this thread flag can be set by utrace.
+
+Add the new internal ptrace flag, PT_SYSCALL_TRACE. Change
+ptrace_set_syscall_trace() to set/clear this bit along with
+TIF_SYSCALL_TRACE, change ptrace_report_syscall() to check
+this flag instead of PT_PTRACED.
+
+Signed-off-by: Oleg Nesterov <oleg at redhat.com>
+---
+ include/linux/ptrace.h | 3 +++
+ include/linux/tracehook.h | 2 +-
+ kernel/ptrace.c | 7 +++++--
+ 3 files changed, 9 insertions(+), 3 deletions(-)
+
+diff --git a/include/linux/ptrace.h b/include/linux/ptrace.h
+index 9178d5c..98d995d 100644
+--- a/include/linux/ptrace.h
++++ b/include/linux/ptrace.h
+@@ -90,6 +90,8 @@
+
+ #define PT_TRACE_MASK 0x000003f4
+
++#define PT_SYSCALL_TRACE 0x00010000
++
+ /* single stepping state bits (used on ARM and PA-RISC) */
+ #define PT_SINGLESTEP_BIT 31
+ #define PT_SINGLESTEP (1<<PT_SINGLESTEP_BIT)
+@@ -187,6 +189,7 @@ static inline void ptrace_init_task(struct task_struct *child, bool ptrace)
+ child->ptrace = 0;
+ if (unlikely(ptrace) && (current->ptrace & PT_PTRACED)) {
+ child->ptrace = current->ptrace;
++ child->ptrace &= ~PT_SYSCALL_TRACE;
+ __ptrace_link(child, current->parent);
+ }
+
+diff --git a/include/linux/tracehook.h b/include/linux/tracehook.h
+index 3c7b6b3..6ce7a37 100644
+--- a/include/linux/tracehook.h
++++ b/include/linux/tracehook.h
+@@ -76,7 +76,7 @@ static inline void ptrace_report_syscall(struct pt_regs *regs)
+ {
+ int ptrace = task_ptrace(current);
+
+- if (!(ptrace & PT_PTRACED))
++ if (!(ptrace & PT_SYSCALL_TRACE))
+ return;
+
+ ptrace_notify(SIGTRAP | ((ptrace & PT_TRACESYSGOOD) ? 0x80 : 0));
+diff --git a/kernel/ptrace.c b/kernel/ptrace.c
+index b6fd922..0825a01 100644
+--- a/kernel/ptrace.c
++++ b/kernel/ptrace.c
+@@ -39,10 +39,13 @@ static void ptrace_signal_wake_up(struct task_struct *p, int quiescent)
+
+ static void ptrace_set_syscall_trace(struct task_struct *p, bool on)
+ {
+- if (on)
++ if (on) {
++ p->ptrace |= PT_SYSCALL_TRACE;
+ set_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
+- else
++ } else {
++ p->ptrace &= ~PT_SYSCALL_TRACE;
+ clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
++ }
+ }
+
+ /*
+--
+1.5.5.1
+
+
+From davej Thu Jun 30 20:27:21 2011
+Return-Path: oleg at redhat.com
+X-Spam-Checker-Version: SpamAssassin 3.3.2 (2011-06-06) on
+ gelk.kernelslacker.org
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+ by gelk with IMAP (fetchmail-6.3.20)
+ for <davej at localhost> (single-drop); Thu, 30 Jun 2011 20:27:21 -0400 (EDT)
+Received: from zmta03.collab.prod.int.phx2.redhat.com (LHLO
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+ oleg at redhat.com; Fri, 1 Jul 2011 02:21:46 +0200 (CEST)
+Date: Fri, 1 Jul 2011 02:21:44 +0200
+From: Oleg Nesterov <oleg at redhat.com>
+To: "Frank Ch. Eigler" <fche at redhat.com>, Kyle McMartin <kmcmartin at redhat.com>,
+ Dave Jones <davej at redhat.com>, Josh Stone <jistone at redhat.com>,
+ Matthew Garrett <mjg at redhat.com>, David Smith <dsmith at redhat.com>
+Cc: kernel at lists.fedoraproject.org, utrace-devel at redhat.com
+Subject: [PATCH 15/19] utrace: don't clear TIF_SYSCALL_TRACE if it is
+ needed by ptrace
+Message-ID: <20110701002144.GA25847 at redhat.com>
+MIME-Version: 1.0
+Content-Type: text/plain; charset=us-ascii
+Content-Disposition: inline
+User-Agent: Mutt/1.5.18 (2008-05-17)
+X-Scanned-By: MIMEDefang 2.68 on 10.5.11.23
+Status: RO
+Content-Length: 797
+Lines: 24
+
+TIF_SYSCALL_TRACE should be cleared only if both ptrace and utrace do
+not want it, change utrace_reset() to check PT_SYSCALL_TRACE before
+clear_tsk_thread_flag(TIF_SYSCALL_TRACE).
+
+Signed-off-by: Oleg Nesterov <oleg at redhat.com>
+---
+ kernel/utrace.c | 1 +
+ 1 files changed, 1 insertions(+), 0 deletions(-)
+
+diff --git a/kernel/utrace.c b/kernel/utrace.c
+index daa96b9..a824ac3 100644
+--- a/kernel/utrace.c
++++ b/kernel/utrace.c
+@@ -697,6 +697,7 @@ static bool utrace_reset(struct task_struct *task, struct utrace *utrace)
+ BUG_ON(utrace->death);
+ flags &= UTRACE_EVENT(REAP);
+ } else if (!(flags & UTRACE_EVENT_SYSCALL) &&
++ !(task->ptrace & PT_SYSCALL_TRACE) &&
+ test_tsk_thread_flag(task, TIF_SYSCALL_TRACE)) {
+ clear_tsk_thread_flag(task, TIF_SYSCALL_TRACE);
+ }
+--
+1.5.5.1
+
+
+From davej Thu Jun 30 20:27:22 2011
+Return-Path: oleg at redhat.com
+X-Spam-Checker-Version: SpamAssassin 3.3.2 (2011-06-06) on
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+Received: from mail.corp.redhat.com [10.5.5.51]
+ by gelk with IMAP (fetchmail-6.3.20)
+ for <davej at localhost> (single-drop); Thu, 30 Jun 2011 20:27:22 -0400 (EDT)
+Received: from zmta01.collab.prod.int.phx2.redhat.com (LHLO
+ zmta01.collab.prod.int.phx2.redhat.com) (10.5.5.31) by
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+ oleg at redhat.com; Fri, 1 Jul 2011 02:21:49 +0200 (CEST)
+Date: Fri, 1 Jul 2011 02:21:47 +0200
+From: Oleg Nesterov <oleg at redhat.com>
+To: "Frank Ch. Eigler" <fche at redhat.com>, Kyle McMartin <kmcmartin at redhat.com>,
+ Dave Jones <davej at redhat.com>, Josh Stone <jistone at redhat.com>,
+ Matthew Garrett <mjg at redhat.com>, David Smith <dsmith at redhat.com>
+Cc: kernel at lists.fedoraproject.org, utrace-devel at redhat.com
+Subject: [PATCH 16/19] introduce task_utrace_lock/task_utrace_unlock
+Message-ID: <20110701002147.GA25854 at redhat.com>
+MIME-Version: 1.0
+Content-Type: text/plain; charset=us-ascii
+Content-Disposition: inline
+User-Agent: Mutt/1.5.18 (2008-05-17)
+X-Scanned-By: MIMEDefang 2.67 on 10.5.11.11
+Status: RO
+Content-Length: 2190
+Lines: 81
+
+- Add task_utrace_lock(task). It simply takes task->utrace->lock if
+ this task was ever utraced. Otherwise it takes task_lock(), this
+ serializes with utrace_attach_task()->utrace_task_alloc(). In both
+ case the caller can be sure it can't race with anything which needs
+ utrace->lock.
+
+- Add task_utrace_unlock(task), it releases the corresponding lock.
+
+Signed-off-by: Oleg Nesterov <oleg at redhat.com>
+---
+ include/linux/utrace.h | 9 +++++++++
+ kernel/utrace.c | 26 ++++++++++++++++++++++++++
+ 2 files changed, 35 insertions(+), 0 deletions(-)
+
+diff --git a/include/linux/utrace.h b/include/linux/utrace.h
+index f251efe..5176f5f 100644
+--- a/include/linux/utrace.h
++++ b/include/linux/utrace.h
+@@ -109,6 +109,12 @@ void utrace_signal_handler(struct task_struct *, int);
+
+ #ifndef CONFIG_UTRACE
+
++static inline void task_utrace_lock(struct task_struct *task)
++{
++}
++static inline void task_utrace_unlock(struct task_struct *task)
++{
++}
+ /*
+ * <linux/tracehook.h> uses these accessors to avoid #ifdef CONFIG_UTRACE.
+ */
+@@ -131,6 +137,9 @@ static inline void task_utrace_proc_status(struct seq_file *m,
+
+ #else /* CONFIG_UTRACE */
+
++extern void task_utrace_lock(struct task_struct *task);
++extern void task_utrace_unlock(struct task_struct *task);
++
+ static inline unsigned long task_utrace_flags(struct task_struct *task)
+ {
+ return task->utrace_flags;
+diff --git a/kernel/utrace.c b/kernel/utrace.c
+index a824ac3..508c13c 100644
+--- a/kernel/utrace.c
++++ b/kernel/utrace.c
+@@ -79,6 +79,32 @@ static int __init utrace_init(void)
+ }
+ module_init(utrace_init);
+
++void task_utrace_lock(struct task_struct *task)
++{
++ struct utrace *utrace = task_utrace_struct(task);
++
++ if (!utrace) {
++ task_lock(task);
++ utrace = task_utrace_struct(task);
++ if (!utrace)
++ return;
++
++ task_unlock(task);
++ }
++
++ spin_lock(&utrace->lock);
++}
++
++void task_utrace_unlock(struct task_struct *task)
++{
++ struct utrace *utrace = task_utrace_struct(task);
++
++ if (utrace)
++ spin_unlock(&utrace->lock);
++ else
++ task_unlock(task);
++}
++
+ /*
+ * Set up @task.utrace for the first time. We can have races
+ * between two utrace_attach_task() calls here. The task_lock()
+--
+1.5.5.1
+
+
+From davej Thu Jun 30 20:27:24 2011
+Return-Path: oleg at redhat.com
+X-Spam-Checker-Version: SpamAssassin 3.3.2 (2011-06-06) on
+ gelk.kernelslacker.org
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+ oleg at redhat.com; Fri, 1 Jul 2011 02:21:53 +0200 (CEST)
+Date: Fri, 1 Jul 2011 02:21:50 +0200
+From: Oleg Nesterov <oleg at redhat.com>
+To: "Frank Ch. Eigler" <fche at redhat.com>, Kyle McMartin <kmcmartin at redhat.com>,
+ Dave Jones <davej at redhat.com>, Josh Stone <jistone at redhat.com>,
+ Matthew Garrett <mjg at redhat.com>, David Smith <dsmith at redhat.com>
+Cc: kernel at lists.fedoraproject.org, utrace-devel at redhat.com
+Subject: [PATCH 17/19] teach ptrace_set_syscall_trace() to play well with
+ utrace
+Message-ID: <20110701002150.GA25861 at redhat.com>
+MIME-Version: 1.0
+Content-Type: text/plain; charset=us-ascii
+Content-Disposition: inline
+User-Agent: Mutt/1.5.18 (2008-05-17)
+X-Scanned-By: MIMEDefang 2.68 on 10.5.11.22
+Status: RO
+Content-Length: 1513
+Lines: 49
+
+1. ptrace_set_syscall_trace(true)->set_tsk_thread_flag(TIF_SYSCALL_TRACE)
+ can race with utrace_control()->utrace_reset() path which can miss
+ PT_SYSCALL_TRACE and clear TIF_SYSCALL_TRACE after it was already set.
+
+2. ptrace_set_syscall_trace(false) clears TIF_SYSCALL_TRACE and this is
+ not utrace-friendly, it can need this flag.
+
+Change ptrace_set_syscall_trace() to take task_utrace_lock(), this is
+enough to fix the 1st problem. Check task_utrace_flags() before clearing
+TIF_SYSCALL_TRACE, this fixes 2.
+
+Signed-off-by: Oleg Nesterov <oleg at redhat.com>
+---
+ kernel/ptrace.c | 6 +++++-
+ 1 files changed, 5 insertions(+), 1 deletions(-)
+
+diff --git a/kernel/ptrace.c b/kernel/ptrace.c
+index 0825a01..209ea2d 100644
+--- a/kernel/ptrace.c
++++ b/kernel/ptrace.c
+@@ -23,6 +23,7 @@
+ #include <linux/uaccess.h>
+ #include <linux/regset.h>
+ #include <linux/hw_breakpoint.h>
++#include <linux/utrace.h>
+
+ static void ptrace_signal_wake_up(struct task_struct *p, int quiescent)
+ {
+@@ -39,13 +40,16 @@ static void ptrace_signal_wake_up(struct task_struct *p, int quiescent)
+
+ static void ptrace_set_syscall_trace(struct task_struct *p, bool on)
+ {
++ task_utrace_lock(p);
+ if (on) {
+ p->ptrace |= PT_SYSCALL_TRACE;
+ set_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
+ } else {
+ p->ptrace &= ~PT_SYSCALL_TRACE;
+- clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
++ if (!(task_utrace_flags(p) & UTRACE_EVENT_SYSCALL))
++ clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
+ }
++ task_utrace_unlock(p);
+ }
+
+ /*
+--
+1.5.5.1
+
+
+From davej Thu Jun 30 20:27:24 2011
+Return-Path: oleg at redhat.com
+X-Spam-Checker-Version: SpamAssassin 3.3.2 (2011-06-06) on
+ gelk.kernelslacker.org
+X-Spam-Level:
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+ by gelk with IMAP (fetchmail-6.3.20)
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+Received: from zmta02.collab.prod.int.phx2.redhat.com (LHLO
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+ oleg at redhat.com; Fri, 1 Jul 2011 02:21:56 +0200 (CEST)
+Date: Fri, 1 Jul 2011 02:21:54 +0200
+From: Oleg Nesterov <oleg at redhat.com>
+To: "Frank Ch. Eigler" <fche at redhat.com>, Kyle McMartin <kmcmartin at redhat.com>,
+ Dave Jones <davej at redhat.com>, Josh Stone <jistone at redhat.com>,
+ Matthew Garrett <mjg at redhat.com>, David Smith <dsmith at redhat.com>
+Cc: kernel at lists.fedoraproject.org, utrace-devel at redhat.com
+Subject: [PATCH 18/19] introduce PT_SINGLE_STEP and PT_SINGLE_BLOCK
+Message-ID: <20110701002154.GA25864 at redhat.com>
+MIME-Version: 1.0
+Content-Type: text/plain; charset=us-ascii
+Content-Disposition: inline
+User-Agent: Mutt/1.5.18 (2008-05-17)
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+Lines: 108
+
+Add the new internal ptrace flags, PT_SINGLE_STEP and PT_SINGLE_BLOCK.
+
+Like PT_SYSCALL_TRACE, this is needed to avoid the unnecessary ptrace
+reports when TIF_SINGLESTEP was set by another engine, not by ptrace.
+Also, we need these bits to coordinate the user_*_single_step() calls
+from ptrace and utrace.
+
+TODO: update the !x86 ptrace code which does user_disable_single_step().
+
+Signed-off-by: Oleg Nesterov <oleg at redhat.com>
+---
+ arch/x86/kernel/ptrace.c | 1 +
+ include/linux/ptrace.h | 5 ++++-
+ include/linux/tracehook.h | 7 +++++--
+ kernel/ptrace.c | 3 +++
+ 4 files changed, 13 insertions(+), 3 deletions(-)
+
+diff --git a/arch/x86/kernel/ptrace.c b/arch/x86/kernel/ptrace.c
+index 807c2a2..7ab475f 100644
+--- a/arch/x86/kernel/ptrace.c
++++ b/arch/x86/kernel/ptrace.c
+@@ -807,6 +807,7 @@ static int ioperm_get(struct task_struct *target,
+ */
+ void ptrace_disable(struct task_struct *child)
+ {
++ child->ptrace &= ~(PT_SINGLE_STEP | PT_SINGLE_BLOCK);
+ user_disable_single_step(child);
+ #ifdef TIF_SYSCALL_EMU
+ clear_tsk_thread_flag(child, TIF_SYSCALL_EMU);
+diff --git a/include/linux/ptrace.h b/include/linux/ptrace.h
+index 98d995d..65b1e4f 100644
+--- a/include/linux/ptrace.h
++++ b/include/linux/ptrace.h
+@@ -91,6 +91,8 @@
+ #define PT_TRACE_MASK 0x000003f4
+
+ #define PT_SYSCALL_TRACE 0x00010000
++#define PT_SINGLE_STEP 0x00020000
++#define PT_SINGLE_BLOCK 0x00040000
+
+ /* single stepping state bits (used on ARM and PA-RISC) */
+ #define PT_SINGLESTEP_BIT 31
+@@ -189,7 +191,8 @@ static inline void ptrace_init_task(struct task_struct *child, bool ptrace)
+ child->ptrace = 0;
+ if (unlikely(ptrace) && (current->ptrace & PT_PTRACED)) {
+ child->ptrace = current->ptrace;
+- child->ptrace &= ~PT_SYSCALL_TRACE;
++ child->ptrace &=
++ ~(PT_SYSCALL_TRACE | PT_SINGLE_STEP | PT_SINGLE_BLOCK);
+ __ptrace_link(child, current->parent);
+ }
+
+diff --git a/include/linux/tracehook.h b/include/linux/tracehook.h
+index 6ce7a37..06edb52 100644
+--- a/include/linux/tracehook.h
++++ b/include/linux/tracehook.h
+@@ -121,6 +121,9 @@ static inline __must_check int tracehook_report_syscall_entry(
+ return 0;
+ }
+
++#define ptrace_wants_step() \
++ (current->ptrace & (PT_SINGLE_STEP | PT_SINGLE_BLOCK))
++
+ /**
+ * tracehook_report_syscall_exit - task has just finished a system call
+ * @regs: user register state of current task
+@@ -143,7 +146,7 @@ static inline void tracehook_report_syscall_exit(struct pt_regs *regs, int step)
+ if (task_utrace_flags(current) & UTRACE_EVENT(SYSCALL_EXIT))
+ utrace_report_syscall_exit(regs);
+
+- if (step) {
++ if (step && ptrace_wants_step()) {
+ siginfo_t info;
+ user_single_step_siginfo(current, regs, &info);
+ force_sig_info(SIGTRAP, &info, current);
+@@ -436,7 +439,7 @@ static inline void tracehook_signal_handler(int sig, siginfo_t *info,
+ {
+ if (task_utrace_flags(current))
+ utrace_signal_handler(current, stepping);
+- if (stepping)
++ if (stepping && ptrace_wants_step())
+ ptrace_notify(SIGTRAP);
+ }
+
+diff --git a/kernel/ptrace.c b/kernel/ptrace.c
+index 209ea2d..44908d0 100644
+--- a/kernel/ptrace.c
++++ b/kernel/ptrace.c
+@@ -575,13 +575,16 @@ static int ptrace_resume(struct task_struct *child, long request,
+ clear_tsk_thread_flag(child, TIF_SYSCALL_EMU);
+ #endif
+
++ child->ptrace &= ~(PT_SINGLE_STEP | PT_SINGLE_BLOCK);
+ if (is_singleblock(request)) {
+ if (unlikely(!arch_has_block_step()))
+ return -EIO;
++ child->ptrace |= PT_SINGLE_BLOCK;
+ user_enable_block_step(child);
+ } else if (is_singlestep(request) || is_sysemu_singlestep(request)) {
+ if (unlikely(!arch_has_single_step()))
+ return -EIO;
++ child->ptrace |= PT_SINGLE_STEP;
+ user_enable_single_step(child);
+ } else {
+ user_disable_single_step(child);
+--
+1.5.5.1
+
+
+From davej Thu Jun 30 20:27:26 2011
+Return-Path: oleg at redhat.com
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+ oleg at redhat.com; Fri, 1 Jul 2011 02:21:59 +0200 (CEST)
+Date: Fri, 1 Jul 2011 02:21:57 +0200
+From: Oleg Nesterov <oleg at redhat.com>
+To: "Frank Ch. Eigler" <fche at redhat.com>, Kyle McMartin <kmcmartin at redhat.com>,
+ Dave Jones <davej at redhat.com>, Josh Stone <jistone at redhat.com>,
+ Matthew Garrett <mjg at redhat.com>, David Smith <dsmith at redhat.com>
+Cc: kernel at lists.fedoraproject.org, utrace-devel at redhat.com
+Subject: [PATCH 19/19] utrace: consult PT_SINGLE_STEP/PT_SINGLE_BLOCK
+ before user_disable_single_step()
+Message-ID: <20110701002157.GA25871 at redhat.com>
+MIME-Version: 1.0
+Content-Type: text/plain; charset=us-ascii
+Content-Disposition: inline
+User-Agent: Mutt/1.5.18 (2008-05-17)
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+Status: RO
+Content-Length: 1150
+Lines: 41
+
+- do not do user_enable_block_step() if PT_SINGLE_STEP is set, in this
+ case ptrace has already called user_enable_single_step()
+
+- do not do user_disable_single_step() if PT_*_STEP is set, ptrace needs
+ the stepping
+
+Unless the tracee is killed this can't race with ptrace, this is called
+by the tracee itself.
+
+Signed-off-by: Oleg Nesterov <oleg at redhat.com>
+---
+ kernel/utrace.c | 6 ++++--
+ 1 files changed, 4 insertions(+), 2 deletions(-)
+
+diff --git a/kernel/utrace.c b/kernel/utrace.c
+index 508c13c..d6607cb 100644
+--- a/kernel/utrace.c
++++ b/kernel/utrace.c
+@@ -1828,7 +1828,8 @@ static void finish_resume_report(struct task_struct *task,
+
+ case UTRACE_BLOCKSTEP:
+ if (likely(arch_has_block_step())) {
+- user_enable_block_step(task);
++ if (!(current->ptrace & PT_SINGLE_STEP))
++ user_enable_block_step(task);
+ break;
+ }
+
+@@ -1856,7 +1857,8 @@ static void finish_resume_report(struct task_struct *task,
+ case UTRACE_REPORT:
+ case UTRACE_RESUME:
+ default:
+- user_disable_single_step(task);
++ if (!(current->ptrace & (PT_SINGLE_STEP | PT_SINGLE_BLOCK)))
++ user_disable_single_step(task);
+ break;
+ }
+ }
+--
+1.5.5.1
+
+
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