Re: [fedora-arm] arm64 uprobes support showing signs of life
On 01/07/2015 07:07 AM, Pratyush Anand wrote:
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%3C54A9E...
>
> 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)
Hi Pratyush,
Are there any other places that need to be protected from kprobe probing in the arm64
code?
Update code is here:
https://github.com/pratyushanand/linux.git : ml_arm64_uprobe_devel_v2
~Pratyush
I will give the new kernel a try.
-Will
>
> However, things are looking better for user-space probing on arm64.
>
> -Will
>