kmsan: fix memcpy tests

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.

Link: https://lkml.kernel.org/r/20221205145740.694038-1-glider@google.com
Signed-off-by: Alexander Potapenko <glider@google.com>
Suggested-by: Marco Elver <elver@google.com>
Reviewed-by: Marco Elver <elver@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/kmsan/kmsan_test.c b/mm/kmsan/kmsan_test.c
index 9a29ea2..eb44ef3 100644 (file)
--- 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));