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Mon, 02 Dec 2019 02:03:36 -0800 (PST) MIME-Version: 1.0 References: <20191122112621.204798-1-glider@google.com> <20191122112621.204798-13-glider@google.com> In-Reply-To: <20191122112621.204798-13-glider@google.com> From: Marco Elver Date: Mon, 2 Dec 2019 11:03:25 +0100 Message-ID: Subject: Re: [PATCH RFC v3 12/36] kmsan: define READ_ONCE_NOCHECK() To: Alexander Potapenko Cc: Mark Rutland , Vegard Nossum , Dmitry Vyukov , Linux Memory Management List , Al Viro , adilger.kernel@dilger.ca, Andrew Morton , Andrey Konovalov , Andrey Ryabinin , Andy Lutomirski , Ard Biesheuvel , Arnd Bergmann , hch@infradead.org, Christoph Hellwig , darrick.wong@oracle.com, davem@davemloft.net, dmitry.torokhov@gmail.com, Eric Biggers , Eric Dumazet , ericvh@gmail.com, gregkh@linuxfoundation.org, harry.wentland@amd.com, herbert@gondor.apana.org.au, iii@linux.ibm.com, mingo@elte.hu, jasowang@redhat.com, Jens Axboe , m.szyprowski@samsung.com, martin.petersen@oracle.com, schwidefsky@de.ibm.com, Matthew Wilcox , mst@redhat.com, Michal Simek , pmladek@suse.com, Qian Cai , Randy Dunlap , robin.murphy@arm.com, Sergey Senozhatsky , Steven Rostedt , tiwai@suse.com, tytso@mit.edu, Thomas Gleixner , gor@linux.ibm.com, wsa@the-dreams.de Content-Type: text/plain; charset="UTF-8" X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Fri, 22 Nov 2019 at 12:27, wrote: > > READ_ONCE_NOCHECK() is already used by KASAN to ignore memory accesses > from e.g. stack unwinders. > Define READ_ONCE_NOCHECK() for KMSAN so that it returns initialized > values. This helps defeat false positives from leftover stack contents. > > Signed-off-by: Alexander Potapenko > To: Alexander Potapenko > Cc: Mark Rutland > Cc: Vegard Nossum > Cc: Dmitry Vyukov > Cc: linux-mm@kvack.org > --- > v3: > - removed unnecessary #ifdef as requested by Mark Rutland > > Change-Id: Ib38369ba038ab3b581d8e45b81036c3304fb79cb > --- > include/linux/compiler.h | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/include/linux/compiler.h b/include/linux/compiler.h > index 5e88e7e33abe..99d40f31a2c3 100644 > --- a/include/linux/compiler.h > +++ b/include/linux/compiler.h > @@ -270,9 +270,9 @@ static __always_inline void __write_once_size(volatile void *p, void *res, int s > > /* > * Use READ_ONCE_NOCHECK() instead of READ_ONCE() if you need > - * to hide memory access from KASAN. > + * to hide memory access from KASAN or KMSAN. > */ > -#define READ_ONCE_NOCHECK(x) __READ_ONCE(x, 0) > +#define READ_ONCE_NOCHECK(x) KMSAN_INIT_VALUE(__READ_ONCE(x, 0)) I think this needs: #include above. > static __no_kasan_or_inline > unsigned long read_word_at_a_time(const void *addr) > -- > 2.24.0.432.g9d3f5f5b63-goog >