linux-kernel - Re: [PATCH -tip 2/2] compiler_types.h: Add __no_sanitize

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Date:   Tue, 2 Jun 2020 11:49:10 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Marco Elver <elver@...gle.com>,
        Miguel Ojeda <miguel.ojeda.sandonis@...il.com>
Cc:     Will Deacon <will@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Borislav Petkov <bp@...en8.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>,
        clang-built-linux <clang-built-linux@...glegroups.com>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Alexander Potapenko <glider@...gle.com>,
        Andrey Konovalov <andreyknvl@...gle.com>,
        kasan-dev <kasan-dev@...glegroups.com>,
        LKML <linux-kernel@...r.kernel.org>,
        syzbot+dc1fa714cb070b184db5@...kaller.appspotmail.com
Subject: Re: [PATCH -tip 2/2] compiler_types.h: Add __no_sanitize_{address,undefined}
 to noinstr

On Tue, Jun 2, 2020 at 11:44 AM 'Marco Elver' via Clang Built Linux
<clang-built-linux@...glegroups.com> wrote:
>
> Adds the portable definitions for __no_sanitize_address, and
> __no_sanitize_undefined, and subsequently changes noinstr to use the
> attributes to disable instrumentation via KASAN or UBSAN.
>
> Link: https://lore.kernel.org/lkml/000000000000d2474c05a6c938fe@google.com/
> Reported-by: syzbot+dc1fa714cb070b184db5@...kaller.appspotmail.com
> Signed-off-by: Marco Elver <elver@...gle.com>

Currently most of our compiler attribute detection is done in
include/linux/compiler_attributes.h; I think this should be handled
there. +Miguel Ojeda

> ---
>
> Note: __no_sanitize_coverage (for KCOV) isn't possible right now,
> because neither GCC nor Clang support such an attribute. This means
> going and changing the compilers again (for Clang it's fine, for GCC,
> it'll take a while).
>
> However, it looks like that KCOV_INSTRUMENT := n is currently in all the
> right places. Short-term, this should be reasonable.
> ---
>  include/linux/compiler-clang.h | 8 ++++++++
>  include/linux/compiler-gcc.h   | 6 ++++++
>  include/linux/compiler_types.h | 3 ++-
>  3 files changed, 16 insertions(+), 1 deletion(-)
>
> diff --git a/include/linux/compiler-clang.h b/include/linux/compiler-clang.h
> index 2cb42d8bdedc..c0e4b193b311 100644
> --- a/include/linux/compiler-clang.h
> +++ b/include/linux/compiler-clang.h
> @@ -33,6 +33,14 @@
>  #define __no_sanitize_thread
>  #endif
>
> +#if __has_feature(undefined_behavior_sanitizer)
> +/* GCC does not have __SANITIZE_UNDEFINED__ */
> +#define __no_sanitize_undefined \
> +               __attribute__((no_sanitize("undefined")))
> +#else
> +#define __no_sanitize_undefined
> +#endif
> +
>  /*
>   * Not all versions of clang implement the the type-generic versions
>   * of the builtin overflow checkers. Fortunately, clang implements
> diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h
> index 7dd4e0349ef3..1c74464c80c6 100644
> --- a/include/linux/compiler-gcc.h
> +++ b/include/linux/compiler-gcc.h
> @@ -150,6 +150,12 @@
>  #define __no_sanitize_thread
>  #endif
>
> +#if __has_attribute(__no_sanitize_undefined__)
> +#define __no_sanitize_undefined __attribute__((no_sanitize_undefined))
> +#else
> +#define __no_sanitize_undefined
> +#endif
> +
>  #if GCC_VERSION >= 50100
>  #define COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW 1
>  #endif
> diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h
> index 02becd21d456..89b8c1ae18a1 100644
> --- a/include/linux/compiler_types.h
> +++ b/include/linux/compiler_types.h
> @@ -198,7 +198,8 @@ struct ftrace_likely_data {
>
>  /* Section for code which can't be instrumented at all */
>  #define noinstr                                                                \
> -       noinline notrace __attribute((__section__(".noinstr.text"))) __no_kcsan
> +       noinline notrace __attribute((__section__(".noinstr.text")))    \
> +       __no_kcsan __no_sanitize_address __no_sanitize_undefined
>
>  #endif /* __KERNEL__ */
>
> --

-- 
Thanks,
~Nick Desaulniers