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charset="UTF-8" X-Stat-Signature: e77kp13rcki8pqentjg7y4di8946yauw X-Rspam-User: X-Spamd-Result: default: False [-0.72 / 9.00]; BAYES_HAM(-3.82)[94.52%]; SORBS_IRL_BL(3.00)[209.85.219.176:from]; RCVD_NO_TLS_LAST(0.10)[]; MIME_GOOD(-0.10)[text/plain]; BAD_REP_POLICIES(0.10)[]; TO_DN_SOME(0.00)[]; R_DKIM_ALLOW(0.00)[google.com:s=20210112]; DMARC_POLICY_ALLOW(0.00)[google.com,reject]; FROM_EQ_ENVFROM(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; MIME_TRACE(0.00)[0:+]; R_SPF_ALLOW(0.00)[+ip4:209.85.128.0/17]; DKIM_TRACE(0.00)[google.com:+]; FROM_HAS_DN(0.00)[]; PREVIOUSLY_DELIVERED(0.00)[linux-mm@kvack.org]; TO_MATCH_ENVRCPT_SOME(0.00)[]; ARC_SIGNED(0.00)[hostedemail.com:s=arc-20220608:i=1]; RCPT_COUNT_FIVE(0.00)[5]; ARC_NA(0.00)[] X-Rspamd-Queue-Id: 9A8B612001A X-Rspamd-Server: rspam06 X-HE-Tag: 1670253080-730206 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 Mon, 5 Dec 2022 at 15:57, Alexander Potapenko wrote: > > Recent Clang changes may cause it to delete calls of memcpy(), if the > source is an uninitialized volatile local. > This happens because passing a pointer to a volatile local into memcpy() > discards the volatile qualifier, giving the compiler a free hand to > optimize the memcpy() call away. > > Use OPTIMIZER_HIDE_VAR() to hide the uninitialized var from the > too-smart compiler. > > Suggested-by: Marco Elver > Signed-off-by: Alexander Potapenko Reviewed-by: Marco Elver > --- > mm/kmsan/kmsan_test.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/mm/kmsan/kmsan_test.c b/mm/kmsan/kmsan_test.c > index 9a29ea2dbfb9b..eb44ef3c5f290 100644 > --- a/mm/kmsan/kmsan_test.c > +++ b/mm/kmsan/kmsan_test.c > @@ -419,6 +419,7 @@ static void test_memcpy_aligned_to_aligned(struct kunit *test) > kunit_info( > test, > "memcpy()ing aligned uninit src to aligned dst (UMR report)\n"); > + OPTIMIZER_HIDE_VAR(uninit_src); > memcpy((void *)&dst, (void *)&uninit_src, sizeof(uninit_src)); > kmsan_check_memory((void *)&dst, sizeof(dst)); > KUNIT_EXPECT_TRUE(test, report_matches(&expect)); > @@ -441,6 +442,7 @@ static void test_memcpy_aligned_to_unaligned(struct kunit *test) > kunit_info( > test, > "memcpy()ing aligned uninit src to unaligned dst (UMR report)\n"); > + OPTIMIZER_HIDE_VAR(uninit_src); > memcpy((void *)&dst[1], (void *)&uninit_src, sizeof(uninit_src)); > kmsan_check_memory((void *)dst, 4); > KUNIT_EXPECT_TRUE(test, report_matches(&expect)); > @@ -464,6 +466,7 @@ static void test_memcpy_aligned_to_unaligned2(struct kunit *test) > kunit_info( > test, > "memcpy()ing aligned uninit src to unaligned dst - part 2 (UMR report)\n"); > + OPTIMIZER_HIDE_VAR(uninit_src); > memcpy((void *)&dst[1], (void *)&uninit_src, sizeof(uninit_src)); > kmsan_check_memory((void *)&dst[4], sizeof(uninit_src)); > KUNIT_EXPECT_TRUE(test, report_matches(&expect)); > -- > 2.39.0.rc0.267.gcb52ba06e7-goog >