Clang 18 learned to optimize away memcpy() calls of small uninitialized
scalar values. To ensure that memcpy tests in kmsan_test.c still perform
calls to memcpy() (which KMSAN replaces with __msan_memcpy()), declare a
separate memcpy_noinline() function with volatile parameters, which
won't be optimized.
Also retire DO_NOT_OPTIMIZE(), as memcpy_noinline() is apparently
enough.
Signed-off-by: Alexander Potapenko <glider@xxxxxxxxxx>
---
v2:
- fix W=1 warnings reported by LKP test robot
---
mm/kmsan/kmsan_test.c | 41 ++++++++++++++++-------------------------
1 file changed, 16 insertions(+), 25 deletions(-)
diff --git a/mm/kmsan/kmsan_test.c b/mm/kmsan/kmsan_test.c
index 312989aa2865c..a8d4ca4a1066d 100644
--- a/mm/kmsan/kmsan_test.c
+++ b/mm/kmsan/kmsan_test.c
@@ -407,33 +407,25 @@ static void test_printk(struct kunit *test)
KUNIT_EXPECT_TRUE(test, report_matches(&expect));
}
-/*
- * Prevent the compiler from optimizing @var away. Without this, Clang may
- * notice that @var is uninitialized and drop memcpy() calls that use it.
- *
- * There is OPTIMIZER_HIDE_VAR() in linux/compier.h that we cannot use here,
- * because it is implemented as inline assembly receiving @var as a parameter
- * and will enforce a KMSAN check. Same is true for e.g. barrier_data(var).
- */
-#define DO_NOT_OPTIMIZE(var) barrier()
+/* Prevent the compiler from inlining a memcpy() call. */
+static noinline void *memcpy_noinline(volatile void *dst,
+ const volatile void *src, size_t size)
+{
+ return memcpy((void *)dst, (const void *)src, size);
+}
-/*
- * Test case: ensure that memcpy() correctly copies initialized values.
- * Also serves as a regression test to ensure DO_NOT_OPTIMIZE() does not cause
- * extra checks.
- */
+/* Test case: ensure that memcpy() correctly copies initialized values. */
static void test_init_memcpy(struct kunit *test)
{
EXPECTATION_NO_REPORT(expect);
- volatile int src;
- volatile int dst = 0;
+ volatile long long src;
+ volatile long long dst = 0;
- DO_NOT_OPTIMIZE(src);
src = 1;
kunit_info(
test,
"memcpy()ing aligned initialized src to aligned dst (no reports)\n");
- memcpy((void *)&dst, (void *)&src, sizeof(src));
+ memcpy_noinline((void *)&dst, (void *)&src, sizeof(src));
kmsan_check_memory((void *)&dst, sizeof(dst));
KUNIT_EXPECT_TRUE(test, report_matches(&expect));
}
@@ -451,8 +443,7 @@ static void test_memcpy_aligned_to_aligned(struct kunit *test)
kunit_info(
test,
"memcpy()ing aligned uninit src to aligned dst (UMR report)\n");
- DO_NOT_OPTIMIZE(uninit_src);
- memcpy((void *)&dst, (void *)&uninit_src, sizeof(uninit_src));
+ memcpy_noinline((void *)&dst, (void *)&uninit_src, sizeof(uninit_src));
kmsan_check_memory((void *)&dst, sizeof(dst));
KUNIT_EXPECT_TRUE(test, report_matches(&expect));
}
@@ -474,8 +465,9 @@ static void test_memcpy_aligned_to_unaligned(struct kunit *test)
kunit_info(
test,
"memcpy()ing aligned uninit src to unaligned dst (UMR report)\n");
- DO_NOT_OPTIMIZE(uninit_src);
- memcpy((void *)&dst[1], (void *)&uninit_src, sizeof(uninit_src));
+ kmsan_check_memory((void *)&uninit_src, sizeof(uninit_src));
+ memcpy_noinline((void *)&dst[1], (void *)&uninit_src,
+ sizeof(uninit_src));
kmsan_check_memory((void *)dst, 4);
KUNIT_EXPECT_TRUE(test, report_matches(&expect));
}
@@ -498,8 +490,8 @@ 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");
- DO_NOT_OPTIMIZE(uninit_src);
- memcpy((void *)&dst[1], (void *)&uninit_src, sizeof(uninit_src));
+ memcpy_noinline((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));
}
@@ -513,7 +505,6 @@ static void test_memcpy_aligned_to_unaligned2(struct kunit *test)
\
kunit_info(test, \
"memset" #size "() should initialize memory\n"); \
- DO_NOT_OPTIMIZE(uninit); \
memset##size((uint##size##_t *)&uninit, 0, 1); \
kmsan_check_memory((void *)&uninit, sizeof(uninit)); \
KUNIT_EXPECT_TRUE(test, report_matches(&expect)); \
--
2.42.0.283.g2d96d420d3-goog
