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From:   Dmitry Vyukov <dvyukov@google.com>
Date:   Thu, 13 Dec 2018 09:52:36 +0100
Message-ID: <CACT4Y+YwuHK3VyYTCE=txWKRr_XWdJrUrw+ehBV=-caOQ9mjKg@mail.gmail.com>
Subject: Re: [PATCH v2] kasan: mark file common so ftrace doesn't trace it
To:     anders.roxell@linaro.org
Cc:     Andrey Ryabinin <aryabinin@virtuozzo.com>,
        kasan-dev <kasan-dev@googlegroups.com>,
        Linux-MM <linux-mm@kvack.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Steven Rostedt <rostedt@goodmis.org>
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On Wed, Dec 12, 2018 at 7:36 PM Anders Roxell <anders.roxell@linaro.org> wrote:
>
> When option CONFIG_KASAN is enabled toghether with ftrace, function
> ftrace_graph_caller() gets in to a recursion, via functions
> kasan_check_read() and kasan_check_write().
>
>  Breakpoint 2, ftrace_graph_caller () at ../arch/arm64/kernel/entry-ftrace.S:179
>  179             mcount_get_pc             x0    //     function's pc
>  (gdb) bt
>  #0  ftrace_graph_caller () at ../arch/arm64/kernel/entry-ftrace.S:179
>  #1  0xffffff90101406c8 in ftrace_caller () at ../arch/arm64/kernel/entry-ftrace.S:151
>  #2  0xffffff90106fd084 in kasan_check_write (p=0xffffffc06c170878, size=4) at ../mm/kasan/common.c:105
>  #3  0xffffff90104a2464 in atomic_add_return (v=<optimized out>, i=<optimized out>) at ./include/generated/atomic-instrumented.h:71
>  #4  atomic_inc_return (v=<optimized out>) at ./include/generated/atomic-fallback.h:284
>  #5  trace_graph_entry (trace=0xffffffc03f5ff380) at ../kernel/trace/trace_functions_graph.c:441
>  #6  0xffffff9010481774 in trace_graph_entry_watchdog (trace=<optimized out>) at ../kernel/trace/trace_selftest.c:741
>  #7  0xffffff90104a185c in function_graph_enter (ret=<optimized out>, func=<optimized out>, frame_pointer=18446743799894897728, retp=<optimized out>) at ../kernel/trace/trace_functions_graph.c:196
>  #8  0xffffff9010140628 in prepare_ftrace_return (self_addr=18446743592948977792, parent=0xffffffc03f5ff418, frame_pointer=18446743799894897728) at ../arch/arm64/kernel/ftrace.c:231
>  #9  0xffffff90101406f4 in ftrace_graph_caller () at ../arch/arm64/kernel/entry-ftrace.S:182
>  Backtrace stopped: previous frame identical to this frame (corrupt stack?)
>  (gdb)
>
> Rework so that the kasan implementation isn't traced.

Acked-by: Dmitry Vyukov <dvyukov@google.com>

Thanks!

> Signed-off-by: Anders Roxell <anders.roxell@linaro.org>
> ---
>  mm/kasan/Makefile | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/mm/kasan/Makefile b/mm/kasan/Makefile
> index 0a14fcff70ed..e2bb06c1b45e 100644
> --- a/mm/kasan/Makefile
> +++ b/mm/kasan/Makefile
> @@ -5,6 +5,7 @@ UBSAN_SANITIZE_generic.o := n
>  UBSAN_SANITIZE_tags.o := n
>  KCOV_INSTRUMENT := n
>
> +CFLAGS_REMOVE_common.o = -pg
>  CFLAGS_REMOVE_generic.o = -pg
>  # Function splitter causes unnecessary splits in __asan_load1/__asan_store1
>  # see: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63533
> --
> 2.19.2
>