From: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
To: glider@google.com
Cc: Vegard Nossum <vegard.nossum@oracle.com>,
Dmitry Vyukov <dvyukov@google.com>,
linux-mm@kvack.org, viro@zeniv.linux.org.uk,
akpm@linux-foundation.org, aryabinin@virtuozzo.com,
luto@kernel.org, ard.biesheuvel@linaro.org, arnd@arndb.de,
hch@lst.de, dmitry.torokhov@gmail.com, edumazet@google.com,
ericvh@gmail.com, gregkh@linuxfoundation.org,
harry.wentland@amd.com, herbert@gondor.apana.org.au,
mingo@elte.hu, axboe@kernel.dk, martin.petersen@oracle.com,
schwidefsky@de.ibm.com, mst@redhat.com, monstr@monstr.eu,
pmladek@suse.com, sergey.senozhatsky@gmail.com,
rostedt@goodmis.org, tiwai@suse.com, tytso@mit.edu,
tglx@linutronix.de, wsa@the-dreams.de, gor@linux.ibm.com,
iii@linux.ibm.com, mark.rutland@arm.com, willy@infradead.org,
rdunlap@infradead.org, andreyknvl@google.com, elver@google.com
Subject: Re: [PATCH RFC v2 02/25] stackdepot: prevent Clang from optimizing away stackdepot_memcmp()
Date: Fri, 1 Nov 2019 14:50:33 +0900 [thread overview]
Message-ID: <20191101055033.GA226263@google.com> (raw)
In-Reply-To: <20191030142237.249532-3-glider@google.com>
On (19/10/30 15:22), glider@google.com wrote:
> Clang may replace stackdepot_memcmp() with a call to instrumented bcmp(),
> which is exactly what we wanted to avoid creating stackdepot_memcmp().
> Add a compiler barrier() to prevent optimizations.
[..]
> @@ -163,6 +163,11 @@ int stackdepot_memcmp(const unsigned long *u1, const unsigned long *u2,
> unsigned int n)
> {
> for ( ; n-- ; u1++, u2++) {
> + /*
> + * Prevent Clang from replacing this function with a bcmp()
> + * call.
> + */
> + barrier();
> if (*u1 != *u2)
> return 1;
> }
Would 'volatile' do the trick?
-ss
next prev parent reply other threads:[~2019-11-01 5:50 UTC|newest]
Thread overview: 61+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-30 14:22 [PATCH RFC v2 00/25] Add KernelMemorySanitizer infrastructure glider
2019-10-30 14:22 ` [PATCH RFC v2 01/25] stackdepot: check depot_index before accessing the stack slab glider
2019-10-30 14:22 ` [PATCH RFC v2 02/25] stackdepot: prevent Clang from optimizing away stackdepot_memcmp() glider
2019-11-01 5:50 ` Sergey Senozhatsky [this message]
2019-11-06 11:43 ` Alexander Potapenko
2019-11-07 6:08 ` Sergey Senozhatsky
2019-11-07 9:04 ` Arnd Bergmann
2019-11-07 9:22 ` Alexander Potapenko
2019-11-07 9:28 ` Arnd Bergmann
2019-11-07 9:43 ` Alexander Potapenko
[not found] ` <47fdac13-fa2c-2acd-2480-5e6d4db208f8@virtuozzo.com>
2019-11-07 10:00 ` Arnd Bergmann
[not found] ` <6875c6e6-2f1f-f8e6-e5d7-d451c48397ff@virtuozzo.com>
2019-11-07 10:30 ` Alexander Potapenko
2019-10-30 14:22 ` [PATCH RFC v2 03/25] kasan: stackdepot: move filter_irq_stacks() to stackdepot.c glider
2019-10-30 14:22 ` [PATCH RFC v2 04/25] stackdepot: reserve 5 extra bits in depot_stack_handle_t glider
2019-10-30 14:22 ` [PATCH RFC v2 05/25] kmsan: add ReST documentation glider
2019-10-30 14:22 ` [PATCH RFC v2 06/25] kmsan: gfp: introduce __GFP_NO_KMSAN_SHADOW glider
2019-10-30 14:22 ` [PATCH RFC v2 07/25] kmsan: introduce __no_sanitize_memory and __SANITIZE_MEMORY__ glider
2019-10-30 15:50 ` Andrey Konovalov
2019-11-01 12:52 ` Alexander Potapenko
2019-10-30 14:22 ` [PATCH RFC v2 08/25] kmsan: reduce vmalloc space glider
2019-10-30 14:22 ` [PATCH RFC v2 09/25] kmsan: add KMSAN runtime glider
2019-11-08 12:08 ` Dmitry Vyukov
2019-11-08 12:17 ` Dmitry Vyukov
2019-11-21 12:06 ` Alexander Potapenko
2019-11-13 8:13 ` Wolfram Sang
2019-11-21 12:01 ` Alexander Potapenko
2019-10-30 14:22 ` [PATCH RFC v2 10/25] kmsan: define READ_ONCE_NOCHECK() glider
2019-11-05 14:21 ` Mark Rutland
2019-11-21 12:08 ` Alexander Potapenko
2019-10-30 14:22 ` [PATCH RFC v2 11/25] kmsan: x86: sync metadata pages on page fault glider
2019-10-30 14:22 ` [PATCH RFC v2 12/25] kmsan: add tests for KMSAN glider
2019-10-30 14:22 ` [PATCH RFC v2 13/25] kmsan: make READ_ONCE_TASK_STACK() return initialized values glider
2019-10-30 14:22 ` [PATCH RFC v2 14/25] kmsan: Kconfig changes to disable options incompatible with KMSAN glider
2019-10-30 14:34 ` Qian Cai
2019-10-30 14:34 ` Christoph Hellwig
2019-10-30 14:22 ` [PATCH RFC v2 15/25] kmsan: Changing existing files to enable KMSAN builds glider
2019-10-30 14:36 ` Christoph Hellwig
2019-10-30 14:22 ` [PATCH RFC v2 16/25] kmsan: disable KMSAN instrumentation for certain kernel parts glider
2019-10-30 14:22 ` [PATCH RFC v2 17/25] kmsan: mm: call KMSAN hooks from SLUB code glider
2019-10-30 16:07 ` Andrey Konovalov
2019-10-30 14:22 ` [PATCH RFC v2 18/25] kmsan: call KMSAN hooks where needed glider
2019-10-31 11:49 ` Petr Mladek
2019-11-01 8:26 ` Sergey Senozhatsky
2019-11-05 14:12 ` Alexander Potapenko
2019-11-06 9:04 ` Petr Mladek
2019-11-06 9:07 ` Sergey Senozhatsky
2019-10-30 14:22 ` [PATCH RFC v2 19/25] kmsan: disable instrumentation of certain functions glider
2019-10-30 14:22 ` [PATCH RFC v2 20/25] kmsan: unpoison |tlb| in arch_tlb_gather_mmu() glider
2019-10-30 14:22 ` [PATCH RFC v2 21/25] kmsan: use __msan_memcpy() where possible glider
2019-10-30 14:22 ` [PATCH RFC v2 22/25] kmsan: unpoisoning buffers from devices etc glider
2019-10-30 14:38 ` Christoph Hellwig
2019-11-05 15:02 ` Alexander Potapenko
2019-11-07 13:00 ` Alexander Potapenko
2019-11-13 11:07 ` Alexander Potapenko
2019-11-01 22:25 ` kbuild test robot
2019-11-03 18:16 ` kbuild test robot
2019-10-30 14:22 ` [PATCH RFC v2 23/25] kmsan: hooks for copy_to_user() and friends glider
2019-11-01 23:08 ` kbuild test robot
2019-11-03 22:10 ` kbuild test robot
2019-10-30 14:22 ` [PATCH RFC v2 24/25] kmsan: disable strscpy() optimization under KMSAN glider
2019-10-30 14:22 ` [PATCH RFC v2 25/25] net: kasan: kmsan: support CONFIG_GENERIC_CSUM on x86, enable it for KASAN/KMSAN glider
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