Re: [PATCH RFC v2 07/25] kmsan: introduce __no_sanitize_memory and __SANITIZE_MEMORY__

From: Andrey Konovalov <andreyknvl@google.com>
To: Alexander Potapenko <glider@google.com>
Cc: Vegard Nossum <vegard.nossum@oracle.com>,
	Dmitry Vyukov <dvyukov@google.com>,
	 Linux Memory Management List <linux-mm@kvack.org>,
	Alexander Viro <viro@zeniv.linux.org.uk>,
	 Andrew Morton <akpm@linux-foundation.org>,
	Andrey Ryabinin <aryabinin@virtuozzo.com>,
	 Andy Lutomirski <luto@kernel.org>,
	Ard Biesheuvel <ard.biesheuvel@linaro.org>,
	 Arnd Bergmann <arnd@arndb.de>, Christoph Hellwig <hch@lst.de>,
	Dmitry Torokhov <dmitry.torokhov@gmail.com>,
	 Eric Dumazet <edumazet@google.com>,
	ericvh@gmail.com,
	 Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	harry.wentland@amd.com,  Herbert Xu <herbert@gondor.apana.org.au>,
	mingo@elte.hu, axboe@kernel.dk,
	 "Martin K. Petersen" <martin.petersen@oracle.com>,
	Martin Schwidefsky <schwidefsky@de.ibm.com>,
	 "Michael S . Tsirkin" <mst@redhat.com>,
	Michal Simek <monstr@monstr.eu>,
	pmladek@suse.com,  sergey.senozhatsky@gmail.com,
	Steven Rostedt <rostedt@goodmis.org>,
	 Takashi Iwai <tiwai@suse.com>, "Theodore Ts'o" <tytso@mit.edu>,
	Thomas Gleixner <tglx@linutronix.de>,
	wsa@the-dreams.de,  gor@linux.ibm.com, iii@linux.ibm.com,
	Mark Rutland <mark.rutland@arm.com>,
	 Matthew Wilcox <willy@infradead.org>,
	Randy Dunlap <rdunlap@infradead.org>,
	 Marco Elver <elver@google.com>
Subject: Re: [PATCH RFC v2 07/25] kmsan: introduce __no_sanitize_memory and __SANITIZE_MEMORY__
Date: Wed, 30 Oct 2019 16:50:11 +0100	[thread overview]
Message-ID: <CAAeHK+z60zXPsWB8qGKyBc_Z1pBY_XNQHF4_pKoLhG=axrkiQg@mail.gmail.com> (raw)
In-Reply-To: <20191030142237.249532-8-glider@google.com>

On Wed, Oct 30, 2019 at 3:23 PM <glider@google.com> wrote:
>
> __no_sanitize_memory is a function attribute that makes KMSAN
> ignore the uninitialized values coming from the function's
> inputs, and initialize the function's outputs.
>
> Functions marked with this attribute can't be inlined into functions
> not marked with it, and vice versa.
>
> __SANITIZE_MEMORY__ is a macro that's defined iff the file is
> instrumented with KMSAN. This is not the same as CONFIG_KMSAN, which is
> defined for every file.
>
> Signed-off-by: Alexander Potapenko <glider@google.com>
> To: Alexander Potapenko <glider@google.com>
> Cc: Vegard Nossum <vegard.nossum@oracle.com>
> Cc: Dmitry Vyukov <dvyukov@google.com>
> Cc: linux-mm@kvack.org
>
> ---
>
> Change-Id: I1f1672652c8392f15f7ca8ac26cd4e71f9cc1e4b
> ---
>  include/linux/compiler-clang.h | 8 ++++++++
>  include/linux/compiler-gcc.h   | 5 +++++
>  2 files changed, 13 insertions(+)
>
> diff --git a/include/linux/compiler-clang.h b/include/linux/compiler-clang.h
> index 333a6695a918..edba13a069a6 100644
> --- a/include/linux/compiler-clang.h
> +++ b/include/linux/compiler-clang.h
> @@ -24,6 +24,14 @@
>  #define __no_sanitize_address
>  #endif
>
> +/* KMSAN is a Clang-only tool, thus putting the defines here */
> +#if __has_feature(memory_sanitizer)
> +# define __SANITIZE_MEMORY__
> +# define __no_sanitize_memory __attribute__((no_sanitize("kernel-memory")))

For KASAN with Clang we ended up choosing to use
no_sanitize("address") instead of no_sanitize("kernel-address") to
make it match what GCC uses. Do we want to use no_sanitize("memory")
here?

> +#else
> +# define __no_sanitize_memory
> +#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 d7ee4c6bad48..e5ebc788dde4 100644
> --- a/include/linux/compiler-gcc.h
> +++ b/include/linux/compiler-gcc.h
> @@ -145,6 +145,11 @@
>  #define __no_sanitize_address
>  #endif
>
> +/*
> + * GCC doesn't support KMSAN.
> + */
> +#define __no_sanitize_memory
> +
>  #if GCC_VERSION >= 50100
>  #define COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW 1
>  #endif
> --
> 2.24.0.rc0.303.g954a862665-goog
>