On Mon, 5 Dec 2022 at 15:57, Alexander Potapenko <glider@xxxxxxxxxx> 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 <elver@xxxxxxxxxx> > Signed-off-by: Alexander Potapenko <glider@xxxxxxxxxx> Reviewed-by: Marco Elver <elver@xxxxxxxxxx> > --- > 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 >
