powerpc: Implement save_stack_trace_regs() to enable kprobe stack tracing (was [RFC] ppc: Implement save_stack_trace_regs())

[Michael Ellerman]

On Mon, 2016-11-01 at 03:30:31 UTC, Michael Ellerman wrote:
> On Fri, 2016-01-08 at 17:50 -0500, Steven Rostedt wrote:
> > > Are you going to take this, or do you want me to?
>
> Sorry, yep I'll take it.
>
> I trimmed the change log a bit, final version below.
>
> powerpc: Implement save_stack_trace_regs() to enable kprobe stack tracing
>
> It has come to my attention that kprobe event stack tracing does not
> work on powerpc. You can see with the following:
>
>   # cd /sys/kernel/debug/tracing
>   # echo stacktrace > trace_options
>   # echo 'p kfree' > kprobe_events
>   # echo 1 > events/kprobes/enable
>
> Will print the following warning:
>   save_stack_trace_regs() not implemented yet.
>
> Although save_stack_trace() (which normal event stack traces use) is
> implemented, save_stack_trace_regs() which kprobe events use is not.
> This is a cheap attempt to implement that function.
>
> Note, This may have issues if a task tries to get a stack trace from
> another task with its regs, because it just passes in "current" to
> save_context_stack(). But this does solve the issue with stack tracing
> kprobe events.
>
> Reported-by: Chunyu Hu <chuhu at redhat.com>
> Signed-off-by: Steven Rostedt <rostedt at goodmis.org>
> Signed-off-by: Michael Ellerman <mpe at ellerman.id.au>

Applied to powerpc next, thanks.

https://git.kernel.org/powerpc/c/35de3b1aa16842214e0cd7c603

cheers