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kmsan: prevent optimizations in memcpy tests 

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.

Link: https://lkml.kernel.org/r/20230911145702.2663753-2-glider@google.com
Signed-off-by: Alexander Potapenko <glider@google.com>
Acked-by: Marco Elver <elver@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Alexander Potapenko 2023-09-11 16:57:00 +02:00 committed by Andrew Morton
parent be1ab60eb0
commit 0be7b2c232
1 changed files with 16 additions and 25 deletions
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41
mm/kmsan/kmsan_test.c
View File

@ -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)); \