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

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Date:	Thu, 28 Jul 2016 14:39:33 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Jiri Olsa <jolsa@...nel.org>
Cc:	lkml <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...nel.org>,
	Michael Grundy <grundym@...ibm.com>,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
Subject: Re: [PATCH] ftrace/jprobes/s390: Fix conflict between jprobes and
 function graph tracing

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

-- Steve

> 
> Signed-off-by: Jiri Olsa <jolsa@...nel.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 */