Re: [PATCH v4 bpf-next 7/9] selftests/bpf: switch test to new attach_perf_event API
From: Yonghong Song <hidden>
Date: 2019-07-01 17:16:25
Also in:
bpf
On 6/28/19 8:49 PM, Andrii Nakryiko wrote:
quoted hunk ↗ jump to hunk
Use new bpf_program__attach_perf_event() in test previously relying on direct ioctl manipulations. Signed-off-by: Andrii Nakryiko <redacted> Reviewed-by: Stanislav Fomichev <redacted> Acked-by: Song Liu <redacted> --- .../bpf/prog_tests/stacktrace_build_id_nmi.c | 31 +++++++++---------- 1 file changed, 15 insertions(+), 16 deletions(-)diff --git a/tools/testing/selftests/bpf/prog_tests/stacktrace_build_id_nmi.c b/tools/testing/selftests/bpf/prog_tests/stacktrace_build_id_nmi.c index 1c1a2f75f3d8..9557b7dfb782 100644 --- a/tools/testing/selftests/bpf/prog_tests/stacktrace_build_id_nmi.c +++ b/tools/testing/selftests/bpf/prog_tests/stacktrace_build_id_nmi.c@@ -17,6 +17,7 @@ static __u64 read_perf_max_sample_freq(void) void test_stacktrace_build_id_nmi(void) { int control_map_fd, stackid_hmap_fd, stackmap_fd, stack_amap_fd; + const char *prog_name = "tracepoint/random/urandom_read"; const char *file = "./test_stacktrace_build_id.o"; int err, pmu_fd, prog_fd; struct perf_event_attr attr = {@@ -25,7 +26,9 @@ void test_stacktrace_build_id_nmi(void) .config = PERF_COUNT_HW_CPU_CYCLES, }; __u32 key, previous_key, val, duration = 0; + struct bpf_program *prog; struct bpf_object *obj; + struct bpf_link *link; char buf[256]; int i, j; struct bpf_stack_build_id id_offs[PERF_MAX_STACK_DEPTH];@@ -39,6 +42,10 @@ void test_stacktrace_build_id_nmi(void) if (CHECK(err, "prog_load", "err %d errno %d\n", err, errno)) return; + prog = bpf_object__find_program_by_title(obj, prog_name); + if (CHECK(!prog, "find_prog", "prog '%s' not found\n", prog_name)) + goto close_prog; + pmu_fd = syscall(__NR_perf_event_open, &attr, -1 /* pid */, 0 /* cpu 0 */, -1 /* group id */, 0 /* flags */);@@ -47,15 +54,12 @@ void test_stacktrace_build_id_nmi(void) pmu_fd, errno)) goto close_prog; - err = ioctl(pmu_fd, PERF_EVENT_IOC_ENABLE, 0); - if (CHECK(err, "perf_event_ioc_enable", "err %d errno %d\n", - err, errno)) - goto close_pmu; - - err = ioctl(pmu_fd, PERF_EVENT_IOC_SET_BPF, prog_fd); - if (CHECK(err, "perf_event_ioc_set_bpf", "err %d errno %d\n", - err, errno)) - goto disable_pmu; + link = bpf_program__attach_perf_event(prog, pmu_fd); + if (CHECK(IS_ERR(link), "attach_perf_event", + "err %ld\n", PTR_ERR(link))) { + close(pmu_fd); + goto close_prog; + } /* find map fds */ control_map_fd = bpf_find_map(__func__, obj, "control_map");@@ -134,8 +138,7 @@ void test_stacktrace_build_id_nmi(void) * try it one more time. */ if (build_id_matches < 1 && retry--) { - ioctl(pmu_fd, PERF_EVENT_IOC_DISABLE); - close(pmu_fd); + bpf_link__destroy(link); bpf_object__close(obj); printf("%s:WARN:Didn't find expected build ID from the map, retrying\n", __func__);@@ -154,11 +157,7 @@ void test_stacktrace_build_id_nmi(void) */ disable_pmu: - ioctl(pmu_fd, PERF_EVENT_IOC_DISABLE); - -close_pmu: - close(pmu_fd); - + bpf_link__destroy(link);
There is a problem in bpf_link__destroy(link). The "link = bpf_program__attach_perf_event(prog, pmu_fd)" may be an error pointer (IS_ERR(link) is true), in which case, link should be reset to NULL and then call bpf_link__destroy(link). Otherwise, the program may segfault or function incorrectly.
close_prog: bpf_object__close(obj); }