[fedora-arm] arm64 uprobes support showing signs of life
Pratyush Anand
panand at redhat.com
Wed Jan 7 12:07:39 UTC 2015
Hi Will,
On Monday 05 January 2015 09:36 PM, William Cohen wrote:
> Hi All,
>
> Pratyush has been implementing uprobes support for aarch64 and has
> posted a set of patches
> (http://comments.gmane.org/gmane.linux.ports.arm.kernel/382237) for
> review. The really new Linux kernels requires a patch to the
> systemtap runtime because the f_dentry macro has been removed. With
> the patched systemtap I was able to run the systemtap testsuite and
> get some test results exercising the uprobes support:
>
> https://web.elastic.org/~dejazilla/viewsummary.php?summary=%3D%27%3C54A9E21C.2080504%40redhat.com%3E%27
>
> There looked to be a localized fixes for plt support to eliminate the
> unsupported systemtap.base/list.exp plt-* tests.
>
> A number of the tests appear to fail because of userspace arguments
> cannot be found for sdt probes.
>
> The uprobe patches still need some refinement. On a number of
> systemtap "make installcheck" runs the kernel would get stuck spewing
> out:
>
> Unexpected kernel single-step exception at EL1
There are at least two functions of arm64/uprobe implementation
uprobe_breakpoint_handler and uprobe_single_step_handler, where a kprobe
insertion might be causing above issue. Currently I have qualified these
functions with __kprobe, so that one can not insert a kprobe there. With
this you should not be able to see the above message.
However, I am still investigating if a kprobe insertion be allowed to
these functions or any other function which is called directly from
debug exception handler (do_debug_exception)
Update code is here:
https://github.com/pratyushanand/linux.git : ml_arm64_uprobe_devel_v2
~Pratyush
>
> However, things are looking better for user-space probing on arm64.
>
> -Will
>
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