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. To outsmart the compiler, we call __msan_memcpy() instead of memcpy() in test_memcpy_aligned_to_aligned(), test_memcpy_aligned_to_unaligned() and test_memcpy_aligned_to_unaligned2(), because it's the behavior of __msan_memcpy() we are testing here anyway. Signed-off-by: Alexander Potapenko <glider@xxxxxxxxxx> --- mm/kmsan/kmsan_test.c | 16 +++++++++++++--- 1 file changed, 13 insertions(+), 3 deletions(-) diff --git a/mm/kmsan/kmsan_test.c b/mm/kmsan/kmsan_test.c index 9a29ea2dbfb9b..8e4f206a900ae 100644 --- a/mm/kmsan/kmsan_test.c +++ b/mm/kmsan/kmsan_test.c @@ -406,6 +406,16 @@ static void test_printk(struct kunit *test) KUNIT_EXPECT_TRUE(test, report_matches(&expect)); } +/* + * The test_memcpy_xxx tests below should be calling memcpy() to copy an + * uninitialized value from a volatile int. But such calls discard the volatile + * qualifier, so Clang may optimize them away, breaking the tests. + * Because KMSAN instrumentation pass would just replace memcpy() with + * __msan_memcpy(), do that explicitly to trick the optimizer into preserving + * the calls. + */ +void *__msan_memcpy(void *, const void *, size_t); + /* * Test case: ensure that memcpy() correctly copies uninitialized values between * aligned `src` and `dst`. @@ -419,7 +429,7 @@ static void test_memcpy_aligned_to_aligned(struct kunit *test) kunit_info( test, "memcpy()ing aligned uninit src to aligned dst (UMR report)\n"); - memcpy((void *)&dst, (void *)&uninit_src, sizeof(uninit_src)); + __msan_memcpy((void *)&dst, (void *)&uninit_src, sizeof(uninit_src)); kmsan_check_memory((void *)&dst, sizeof(dst)); KUNIT_EXPECT_TRUE(test, report_matches(&expect)); } @@ -441,7 +451,7 @@ static void test_memcpy_aligned_to_unaligned(struct kunit *test) kunit_info( test, "memcpy()ing aligned uninit src to unaligned dst (UMR report)\n"); - memcpy((void *)&dst[1], (void *)&uninit_src, sizeof(uninit_src)); + __msan_memcpy((void *)&dst[1], (void *)&uninit_src, sizeof(uninit_src)); kmsan_check_memory((void *)dst, 4); KUNIT_EXPECT_TRUE(test, report_matches(&expect)); } @@ -464,7 +474,7 @@ 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"); - memcpy((void *)&dst[1], (void *)&uninit_src, sizeof(uninit_src)); + __msan_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
