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From: Dmitry Vyukov <dvyukov@google.com>
Date: Thu, 21 Apr 2016 12:39:02 +0200
Message-ID: <CACT4Y+ayeScUP91zVx0-RJSDzs35V8O2i1n_ysAYEKep1CzMSQ@mail.gmail.com>
Subject: Re: [PATCH] kcov: disable tracing and branch profiling in kcov
To: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
        LKML <linux-kernel@vger.kernel.org>,
        syzkaller <syzkaller@googlegroups.com>
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On Thu, Apr 21, 2016 at 12:32 PM, Andrey Ryabinin
<aryabinin@virtuozzo.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@virtuozzo.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.