progs/lsm_bdev.c keys its verity_devices hashmap with the raw kernel dev_t read straight off bdev->bd_dev, i.e. MKDEV(major, minor) = (major << 20) | minor. prog_tests/lsm_bdev.c instead builds its lookup key with dev_key = (__u32)st.st_rdev from stat(2), but the stat(2) syscall fills st_rdev via the kernel's new_encode_dev(), a different bit layout: (minor & 0xff) | (major << 8) | ((minor & ~0xff) << 12). For any device with a non-trivial major these two values differ, so the lookup can never find what the BPF program stored, and test_lsm_bdev() always fails with: test_lsm_bdev:FAIL:map lookup unexpected error: -2 (errno 2) Reconstruct the raw kernel dev_t from the decoded major/minor instead of casting st_rdev directly, restoring the layout the BPF program actually reads. Fixes: 96f4c251a087 ("selftests/bpf: add block device management selftests") Signed-off-by: Ricardo B. Marlière --- tools/testing/selftests/bpf/prog_tests/lsm_bdev.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/tools/testing/selftests/bpf/prog_tests/lsm_bdev.c b/tools/testing/selftests/bpf/prog_tests/lsm_bdev.c index a970798e1173..28bc4b117f41 100644 --- a/tools/testing/selftests/bpf/prog_tests/lsm_bdev.c +++ b/tools/testing/selftests/bpf/prog_tests/lsm_bdev.c @@ -17,6 +17,7 @@ #include #include #include +#include #include #include #include "lsm_bdev.skel.h" @@ -172,7 +173,7 @@ void test_lsm_bdev(void) if (!ASSERT_OK(stat(DM_DEV_PATH, &st), "stat dm dev")) goto remove_dm; - dev_key = (__u32)st.st_rdev; + dev_key = (major(st.st_rdev) << 20) | minor(st.st_rdev); /* Look up the device in the BPF map and verify. */ err = bpf_map__lookup_elem(skel->maps.verity_devices, -- 2.54.0