lkml.org 
[lkml]   [2023]   [Mar]   [3]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    Date
    Subject[PATCH 2/4] kmsan: another take at fixing memcpy tests
    From
    commit 5478afc55a21 ("kmsan: fix memcpy tests") uses OPTIMIZER_HIDE_VAR()
    to hide the uninitialized var from the compiler optimizations.

    However OPTIMIZER_HIDE_VAR(uninit) enforces an immediate check of
    @uninit, so memcpy tests did not actually check the behavior of memcpy(),
    because they always contained a KMSAN report.

    Replace OPTIMIZER_HIDE_VAR() with a file-local macro that just clobbers
    the memory with a barrier(), and add a test case for memcpy() that does not
    expect an error report.

    Also reflow kmsan_test.c with clang-format.

    Signed-off-by: Alexander Potapenko <glider@google.com>
    ---
    v2:
    - replace inline assembly with a barrier(), update comments
    ---
    mm/kmsan/kmsan_test.c | 44 +++++++++++++++++++++++++++++++++++++------
    1 file changed, 38 insertions(+), 6 deletions(-)

    diff --git a/mm/kmsan/kmsan_test.c b/mm/kmsan/kmsan_test.c
    index 088e21a48dc4b..aeddfdd4f679f 100644
    --- a/mm/kmsan/kmsan_test.c
    +++ b/mm/kmsan/kmsan_test.c
    @@ -407,6 +407,37 @@ 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()
    +
    +/*
    + * 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.
    + */
    +static void test_init_memcpy(struct kunit *test)
    +{
    + EXPECTATION_NO_REPORT(expect);
    + volatile int src;
    + volatile int 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));
    + kmsan_check_memory((void *)&dst, sizeof(dst));
    + KUNIT_EXPECT_TRUE(test, report_matches(&expect));
    +}
    +
    /*
    * Test case: ensure that memcpy() correctly copies uninitialized values between
    * aligned `src` and `dst`.
    @@ -420,7 +451,7 @@ 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);
    + DO_NOT_OPTIMIZE(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));
    @@ -443,7 +474,7 @@ 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);
    + DO_NOT_OPTIMIZE(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));
    @@ -467,13 +498,14 @@ 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);
    + DO_NOT_OPTIMIZE(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));
    }

    -static noinline void fibonacci(int *array, int size, int start) {
    +static noinline void fibonacci(int *array, int size, int start)
    +{
    if (start < 2 || (start == size))
    return;
    array[start] = array[start - 1] + array[start - 2];
    @@ -482,8 +514,7 @@ static noinline void fibonacci(int *array, int size, int start) {

    static void test_long_origin_chain(struct kunit *test)
    {
    - EXPECTATION_UNINIT_VALUE_FN(expect,
    - "test_long_origin_chain");
    + EXPECTATION_UNINIT_VALUE_FN(expect, "test_long_origin_chain");
    /* (KMSAN_MAX_ORIGIN_DEPTH * 2) recursive calls to fibonacci(). */
    volatile int accum[KMSAN_MAX_ORIGIN_DEPTH * 2 + 2];
    int last = ARRAY_SIZE(accum) - 1;
    @@ -515,6 +546,7 @@ static struct kunit_case kmsan_test_cases[] = {
    KUNIT_CASE(test_uaf),
    KUNIT_CASE(test_percpu_propagate),
    KUNIT_CASE(test_printk),
    + KUNIT_CASE(test_init_memcpy),
    KUNIT_CASE(test_memcpy_aligned_to_aligned),
    KUNIT_CASE(test_memcpy_aligned_to_unaligned),
    KUNIT_CASE(test_memcpy_aligned_to_unaligned2),
    --
    2.40.0.rc0.216.gc4246ad0f0-goog
    \
     
     \ /
      Last update: 2023-03-27 00:43    [W:4.844 / U:0.028 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site