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References: <20170313163337.1704-1-aryabinin@virtuozzo.com> <tip-be3606ff739d1c1be36389f8737c577ad87e1f57@git.kernel.org>
From: Alexander Potapenko <glider@google.com>
Date: Tue, 14 Mar 2017 15:09:52 +0100
Message-ID: <CAG_fn=VgW2m8KLb49Xp8LerXKwMZTuUW67wc0mpTo7_86=TyWg@mail.gmail.com>
Subject: Re: [tip:x86/urgent] x86/kasan: Fix boot with KASAN=y and PROFILE_ANNOTATED_BRANCHES=y
To: "H. Peter Anvin" <hpa@zytor.com>, Thomas Gleixner <tglx@linutronix.de>,
        Alexander Potapenko <glider@google.com>,
        Dmitriy Vyukov <dvyukov@google.com>,
        Andrey Ryabinin <aryabinin@virtuozzo.com>,
        LKML <linux-kernel@vger.kernel.org>,
        kbuild test robot <fengguang.wu@intel.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Ingo Molnar <mingo@kernel.org>
Cc: linux-tip-commits@vger.kernel.org
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On Tue, Mar 14, 2017 at 12:03 AM, tip-bot for Andrey Ryabinin
<tipbot@zytor.com> wrote:
> Commit-ID:  be3606ff739d1c1be36389f8737c577ad87e1f57
> Gitweb:     http://git.kernel.org/tip/be3606ff739d1c1be36389f8737c577ad87e1f57
> Author:     Andrey Ryabinin <aryabinin@virtuozzo.com>
> AuthorDate: Mon, 13 Mar 2017 19:33:37 +0300
> Committer:  Thomas Gleixner <tglx@linutronix.de>
> CommitDate: Tue, 14 Mar 2017 00:00:55 +0100
>
> x86/kasan: Fix boot with KASAN=y and PROFILE_ANNOTATED_BRANCHES=y
>
> The kernel doesn't boot with both PROFILE_ANNOTATED_BRANCHES=y and KASAN=y
> options selected. With branch profiling enabled we end up calling
> ftrace_likely_update() before kasan_early_init(). ftrace_likely_update() is
> built with KASAN instrumentation, so calling it before kasan has been
> initialized leads to crash.
>
> Use DISABLE_BRANCH_PROFILING define to make sure that we don't call
> ftrace_likely_update() from early code before kasan_early_init().
Won't it suffice to disable instrumentation of ftrace_likely_update() and alike?
> Fixes: ef7f0d6a6ca8 ("x86_64: add KASan support")
> Reported-by: Fengguang Wu <fengguang.wu@intel.com>
> Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
> Cc: kasan-dev@googlegroups.com
> Cc: Alexander Potapenko <glider@google.com>
> Cc: stable@vger.kernel.org
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: lkp@01.org
> Cc: Dmitry Vyukov <dvyukov@google.com>
> Link: http://lkml.kernel.org/r/20170313163337.1704-1-aryabinin@virtuozzo.com
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
>
> ---
>  arch/x86/kernel/head64.c    | 1 +
>  arch/x86/mm/kasan_init_64.c | 1 +
>  2 files changed, 2 insertions(+)
>
> diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c
> index 54a2372..b5785c1 100644
> --- a/arch/x86/kernel/head64.c
> +++ b/arch/x86/kernel/head64.c
> @@ -4,6 +4,7 @@
>   *  Copyright (C) 2000 Andrea Arcangeli <andrea@suse.de> SuSE
>   */
>
> +#define DISABLE_BRANCH_PROFILING
>  #include <linux/init.h>
>  #include <linux/linkage.h>
>  #include <linux/types.h>
> diff --git a/arch/x86/mm/kasan_init_64.c b/arch/x86/mm/kasan_init_64.c
> index 8d63d7a..4c90cfd 100644
> --- a/arch/x86/mm/kasan_init_64.c
> +++ b/arch/x86/mm/kasan_init_64.c
> @@ -1,3 +1,4 @@
> +#define DISABLE_BRANCH_PROFILING
>  #define pr_fmt(fmt) "kasan: " fmt
>  #include <linux/bootmem.h>
>  #include <linux/kasan.h>


-- 
Alexander Potapenko
Software Engineer

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