linux-kernel - Re: [PATCH] kcov: disable tracing and branch profiling in kcov

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Date:	Thu, 21 Apr 2016 12:39:02 +0200
From:	Dmitry Vyukov <dvyukov@...gle.com>
To:	Andrey Ryabinin <aryabinin@...tuozzo.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	syzkaller <syzkaller@...glegroups.com>
Subject: Re: [PATCH] kcov: disable tracing and branch profiling in kcov

On Thu, Apr 21, 2016 at 12:32 PM, Andrey Ryabinin
<aryabinin@...tuozzo.com> wrote:
> Tracing of __sanitizer_cov_trace_pc() causes unbound recursion and crash,
> because __sanitizer_cov_trace_pc() is also called from tracer code.
> For the same reason we need to disable profiling of 'if' branches.
>
> Signed-off-by: Andrey Ryabinin <aryabinin@...tuozzo.com>
> ---
>  kernel/kcov.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/kcov.c b/kernel/kcov.c
> index 3efbee0..7919253 100644
> --- a/kernel/kcov.c
> +++ b/kernel/kcov.c
> @@ -1,5 +1,6 @@
>  #define pr_fmt(fmt) "kcov: " fmt
>
> +#define DISABLE_BRANCH_PROFILING
>  #include <linux/compiler.h>
>  #include <linux/types.h>
>  #include <linux/file.h>
> @@ -43,7 +44,7 @@ struct kcov {
>   * Entry point from instrumented code.
>   * This is called once per basic-block/edge.
>   */
> -void __sanitizer_cov_trace_pc(void)
> +notrace void __sanitizer_cov_trace_pc(void)
>  {
>         struct task_struct *t;
>         enum kcov_mode mode;
> --
> 2.7.3


There was a similar patch "kcov: Don't trace the code coverage code"
recently. But it did not add DISABLE_BRANCH_PROFILING.