Commit 5478afc5 authored by Alexander Potapenko's avatar Alexander Potapenko Committed by Andrew Morton
Browse files

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: default avatarAlexander Potapenko <glider@google.com>
Suggested-by: default avatarMarco Elver <elver@google.com>
Reviewed-by: default avatarMarco Elver <elver@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent de2e5171

mm/kmsan/kmsan_test.c

+3 −0
Original line number Diff line number Diff line
@@ -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));