[PATCH] ftrace/jprobes/s390: Fix conflict between jprobes and function graph tracing

[PATCH] ftrace/jprobes/s390: Fix conflict between jprobes and function graph tracing

[Jiri Olsa]

This fixes the same issue Steven already fixed for x86
in following commit:

  237d28db036e ftrace/jprobes/x86: Fix conflict between jprobes and function graph tracing

It fixes the crash, that happens when function graph tracing
and jprobes are used simultaneously. Please refer to above
commit for details.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
 arch/s390/kernel/kprobes.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/arch/s390/kernel/kprobes.c b/arch/s390/kernel/kprobes.c
index 250f5972536a..dd6306c51bd6 100644
--- a/arch/s390/kernel/kprobes.c
+++ b/arch/s390/kernel/kprobes.c
@@ -690,6 +690,15 @@ int setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
 	stack = (unsigned long) regs->gprs[15];
 
 	memcpy(kcb->jprobes_stack, (void *) stack, MIN_STACK_SIZE(stack));
+
+	/*
+	 * jprobes use jprobe_return() which skips the normal return
+	 * path of the function, and this messes up the accounting of the
+	 * function graph tracer to get messed up.
+	 *
+	 * Pause function graph tracing while performing the jprobe function.
+	 */
+	pause_graph_tracing();
 	return 1;
 }
 NOKPROBE_SYMBOL(setjmp_pre_handler);
@@ -705,6 +714,9 @@ int longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
 	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 	unsigned long stack;
 
+	/* It's OK to start function graph tracing again */
+	unpause_graph_tracing();
+
 	stack = (unsigned long) kcb->jprobe_saved_regs.gprs[15];
 
 	/* Put the regs back */
-- 
2.4.11

Re: [PATCH] ftrace/jprobes/s390: Fix conflict between jprobes and function graph tracing

[Steven Rostedt]

On Mon, 18 Jul 2016 15:26:41 +0200
Jiri Olsa <jolsa@kernel.org> wrote:

> This fixes the same issue Steven already fixed for x86
> in following commit:
> 
>   237d28db036e ftrace/jprobes/x86: Fix conflict between jprobes and function graph tracing
> 
> It fixes the crash, that happens when function graph tracing
> and jprobes are used simultaneously. Please refer to above
> commit for details.

I'm guessing that this should go in via the s390 tree.

Acked-by: Steven Rostedt <rostedt@goodmis.org>

-- Steve

> 
> Signed-off-by: Jiri Olsa <jolsa@kernel.org>
> ---
>  arch/s390/kernel/kprobes.c | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> diff --git a/arch/s390/kernel/kprobes.c b/arch/s390/kernel/kprobes.c
> index 250f5972536a..dd6306c51bd6 100644
> --- a/arch/s390/kernel/kprobes.c
> +++ b/arch/s390/kernel/kprobes.c
> @@ -690,6 +690,15 @@ int setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
>  	stack = (unsigned long) regs->gprs[15];
>  
>  	memcpy(kcb->jprobes_stack, (void *) stack, MIN_STACK_SIZE(stack));
> +
> +	/*
> +	 * jprobes use jprobe_return() which skips the normal return
> +	 * path of the function, and this messes up the accounting of the
> +	 * function graph tracer to get messed up.
> +	 *
> +	 * Pause function graph tracing while performing the jprobe function.
> +	 */
> +	pause_graph_tracing();
>  	return 1;
>  }
>  NOKPROBE_SYMBOL(setjmp_pre_handler);
> @@ -705,6 +714,9 @@ int longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
>  	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
>  	unsigned long stack;
>  
> +	/* It's OK to start function graph tracing again */
> +	unpause_graph_tracing();
> +
>  	stack = (unsigned long) kcb->jprobe_saved_regs.gprs[15];
>  
>  	/* Put the regs back */

Re: [PATCH] ftrace/jprobes/s390: Fix conflict between jprobes and function graph tracing

[Jiri Olsa]

On Thu, Jul 28, 2016 at 02:39:33PM -0400, Steven Rostedt wrote:
> On Mon, 18 Jul 2016 15:26:41 +0200
> Jiri Olsa <jolsa@kernel.org> wrote:
> 
> > This fixes the same issue Steven already fixed for x86
> > in following commit:
> > 
> >   237d28db036e ftrace/jprobes/x86: Fix conflict between jprobes and function graph tracing
> > 
> > It fixes the crash, that happens when function graph tracing
> > and jprobes are used simultaneously. Please refer to above
> > commit for details.
> 
> I'm guessing that this should go in via the s390 tree.

oops, I forgot to CC s390 mailing list.. CC-ing now

I can repost if needed

thanks,
jirka

> 
> Acked-by: Steven Rostedt <rostedt@goodmis.org>
> 
> -- Steve
> 
> > 
> > Signed-off-by: Jiri Olsa <jolsa@kernel.org>
> > ---
> >  arch/s390/kernel/kprobes.c | 12 ++++++++++++
> >  1 file changed, 12 insertions(+)
> > 
> > diff --git a/arch/s390/kernel/kprobes.c b/arch/s390/kernel/kprobes.c
> > index 250f5972536a..dd6306c51bd6 100644
> > --- a/arch/s390/kernel/kprobes.c
> > +++ b/arch/s390/kernel/kprobes.c
> > @@ -690,6 +690,15 @@ int setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
> >  	stack = (unsigned long) regs->gprs[15];
> >  
> >  	memcpy(kcb->jprobes_stack, (void *) stack, MIN_STACK_SIZE(stack));
> > +
> > +	/*
> > +	 * jprobes use jprobe_return() which skips the normal return
> > +	 * path of the function, and this messes up the accounting of the
> > +	 * function graph tracer to get messed up.
> > +	 *
> > +	 * Pause function graph tracing while performing the jprobe function.
> > +	 */
> > +	pause_graph_tracing();
> >  	return 1;
> >  }
> >  NOKPROBE_SYMBOL(setjmp_pre_handler);
> > @@ -705,6 +714,9 @@ int longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
> >  	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
> >  	unsigned long stack;
> >  
> > +	/* It's OK to start function graph tracing again */
> > +	unpause_graph_tracing();
> > +
> >  	stack = (unsigned long) kcb->jprobe_saved_regs.gprs[15];
> >  
> >  	/* Put the regs back */
> 

Re: [PATCH] ftrace/jprobes/s390: Fix conflict between jprobes and function graph tracing

[Martin Schwidefsky]

On Sun, 31 Jul 2016 14:21:14 +0200
Jiri Olsa <jolsa@redhat.com> wrote:

> On Thu, Jul 28, 2016 at 02:39:33PM -0400, Steven Rostedt wrote:
> > On Mon, 18 Jul 2016 15:26:41 +0200
> > Jiri Olsa <jolsa@kernel.org> wrote:
> > 
> > > This fixes the same issue Steven already fixed for x86
> > > in following commit:
> > > 
> > >   237d28db036e ftrace/jprobes/x86: Fix conflict between jprobes and function graph tracing
> > > 
> > > It fixes the crash, that happens when function graph tracing
> > > and jprobes are used simultaneously. Please refer to above
> > > commit for details.
> > 
> > I'm guessing that this should go in via the s390 tree.
> 
> oops, I forgot to CC s390 mailing list.. CC-ing now
> 
> I can repost if needed

This is not necessary. I have seen your original patch and could test
it now. As expected it crashes without the patch and works find with
your patch.

Applied to linux-s390. Thanks.

-- 
blue skies,
   Martin.

"Reality continues to ruin my life." - Calvin.