On 6/28/19 8:49 PM, Andrii Nakryiko wrote:
> Use new bpf_program__attach_perf_event() in test previously relying on
> direct ioctl manipulations.
>
> Signed-off-by: Andrii Nakryiko <andr...@fb.com>
> Reviewed-by: Stanislav Fomichev <s...@google.com>
> Acked-by: Song Liu <songliubrav...@fb.com>
> ---
> .../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);
> }
>
