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Re: [RFC][PATCH] ppc: Implement save_stack_trace_regs()

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  Re: [RFC][PATCH] ppc: Implement save_stack_trace_regs() Steven Rostedt <rostedt@goodmis.org> - 2016-01-09 00:00 +0100
    Re: [RFC][PATCH] ppc: Implement save_stack_trace_regs() Michael Ellerman <mpe@ellerman.id.au> - 2016-01-11 04:40 +0100
      Re: [RFC][PATCH] ppc: Implement save_stack_trace_regs() Steven Rostedt <rostedt@goodmis.org> - 2016-01-11 16:00 +0100
      Re: powerpc: Implement save_stack_trace_regs() to enable kprobe stack tracing (was [RFC] ppc: Implement save_stack_trace_regs()) Michael Ellerman <mpe@ellerman.id.au> - 2016-01-12 13:40 +0100

#1305047 — Re: [RFC][PATCH] ppc: Implement save_stack_trace_regs()

On Wed, 16 Dec 2015 12:24:19 -0500
Steven Rostedt <rostedt@goodmis.org> wrote:

> On Wed, 09 Dec 2015 12:03:05 +1100
> Michael Ellerman <mpe@ellerman.id.au> wrote:
> 
> > > > Should I take this via powerpc or do you want it to go in via tracing?    
> > > 
> > > You can take it. And you can replace the PT_R1 if you want. I just
> > > noticed that it was defined, and I try to use macro names instead of
> > > hard coded numbers. I was actually looking for a "PT_SP" :-)    
> > 
> > OK thanks.
> > 
> > Looks like we actually have:
> > 
> >   #define kernel_stack_pointer(regs) ((regs)->gpr[1])
> > 
> > So that would be the most self documenting way to do it I guess, though I've
> > never actually seen that macro used anywhere before :)  
> 
> Hi,
> 
> Are you going to take this, or do you want me to?
> 
> -- Steve

Ping?

-- Steve

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#1305802

On Fri, 2016-01-08 at 17:50 -0500, Steven Rostedt wrote:
> On Wed, 16 Dec 2015 12:24:19 -0500
> Steven Rostedt <rostedt@goodmis.org> wrote:
> > On Wed, 09 Dec 2015 12:03:05 +1100
> > Michael Ellerman <mpe@ellerman.id.au> wrote:
> > > > > Should I take this via powerpc or do you want it to go in via tracing?
> > > >
> > > > You can take it. And you can replace the PT_R1 if you want. I just
> > > > noticed that it was defined, and I try to use macro names instead of
> > > > hard coded numbers. I was actually looking for a "PT_SP" :-)
> > >
> > > OK thanks.
> > >
> > > Looks like we actually have:
> > >
> > >   #define kernel_stack_pointer(regs) ((regs)->gpr[1])
> > >
> > > So that would be the most self documenting way to do it I guess, though I've
> > > never actually seen that macro used anywhere before :)
> >
> > Hi,
> >
> > 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.

cheers


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@redhat.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

diff --git a/arch/powerpc/kernel/stacktrace.c b/arch/powerpc/kernel/stacktrace.c
index ea43a347a104..4f24606afc3f 100644
--- a/arch/powerpc/kernel/stacktrace.c
+++ b/arch/powerpc/kernel/stacktrace.c
@@ -61,3 +61,10 @@ void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
 	save_context_stack(trace, tsk->thread.ksp, tsk, 0);
 }
 EXPORT_SYMBOL_GPL(save_stack_trace_tsk);
+
+void
+save_stack_trace_regs(struct pt_regs *regs, struct stack_trace *trace)
+{
+	save_context_stack(trace, regs->gpr[1], current, 0);
+}
+EXPORT_SYMBOL_GPL(save_stack_trace_regs);

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#1306357

On Mon, 11 Jan 2016 14:30:31 +1100
Michael Ellerman <mpe@ellerman.id.au> wrote:

 
> Sorry, yep I'll take it.
> 
> I trimmed the change log a bit, final version below.
> 
> cheers
>

Thanks, appreciate it!

-- Steve

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#1307366 — Re: powerpc: Implement save_stack_trace_regs() to enable kprobe stack tracing (was [RFC] ppc: Implement save_stack_trace_regs())

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@redhat.com>
> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

Applied to powerpc next, thanks.

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

cheers

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