On Wed, May 02, 2018 at 04:20:30PM -0700, Song Liu wrote:
> This new test captures stackmap with build_id with hardware event
> PERF_COUNT_HW_CPU_CYCLES.
>
> Because we only support one ips-to-build_id lookup per cpu in NMI
> context, stack_amap will not be able to do the lookup in this test.
stack_map ?
> Therefore, we didn't do compare_stack_ips(), as it will alwasy fail.
>
> urandom_read.c is extended to run configurable cycles so that it can be
> caught by the perf event.
>
> Signed-off-by: Song Liu <songliubrav...@fb.com>
> ---
> tools/testing/selftests/bpf/test_progs.c | 137
> +++++++++++++++++++++++++++++
> tools/testing/selftests/bpf/urandom_read.c | 10 ++-
> 2 files changed, 145 insertions(+), 2 deletions(-)
>
> diff --git a/tools/testing/selftests/bpf/test_progs.c
> b/tools/testing/selftests/bpf/test_progs.c
> index aa336f0..00bb08c 100644
> --- a/tools/testing/selftests/bpf/test_progs.c
> +++ b/tools/testing/selftests/bpf/test_progs.c
> @@ -1272,6 +1272,142 @@ static void test_stacktrace_build_id(void)
> return;
> }
>
> +static void test_stacktrace_build_id_nmi(void)
> +{
> + int control_map_fd, stackid_hmap_fd, stackmap_fd, stack_amap_fd;
> + const char *file = "./test_stacktrace_build_id.o";
> + int err, pmu_fd, prog_fd;
> + struct perf_event_attr attr = {
> + .sample_freq = 5000,
> + .freq = 1,
> + .type = PERF_TYPE_HARDWARE,
> + .config = PERF_COUNT_HW_CPU_CYCLES,
> + };
> + __u32 key, previous_key, val, duration = 0;
> + struct bpf_object *obj;
> + char buf[256];
> + int i, j;
> + struct bpf_stack_build_id id_offs[PERF_MAX_STACK_DEPTH];
> + int build_id_matches = 0;
> +
> + err = bpf_prog_load(file, BPF_PROG_TYPE_PERF_EVENT, &obj, &prog_fd);
> + if (CHECK(err, "prog_load", "err %d errno %d\n", err, errno))
> + goto out;
perhaps:
return;
> + pmu_fd = syscall(__NR_perf_event_open, &attr, -1 /* pid */,
> + 0 /* cpu 0 */, -1 /* group id */,
> + 0 /* flags */);
> + if (CHECK(pmu_fd < 0, "perf_event_open",
> + "err %d errno %d. Does the test host support
> PERF_COUNT_HW_CPU_CYCLES?\n",
> + 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;
> +
> + /* find map fds */
> + control_map_fd = bpf_find_map(__func__, obj, "control_map");
> + if (CHECK(control_map_fd < 0, "bpf_find_map control_map",
> + "err %d errno %d\n", err, errno))
> + goto disable_pmu;
> +
> + stackid_hmap_fd = bpf_find_map(__func__, obj, "stackid_hmap");
> + if (CHECK(stackid_hmap_fd < 0, "bpf_find_map stackid_hmap",
> + "err %d errno %d\n", err, errno))
> + goto disable_pmu;
> +
> + stackmap_fd = bpf_find_map(__func__, obj, "stackmap");
> + if (CHECK(stackmap_fd < 0, "bpf_find_map stackmap", "err %d errno %d\n",
> + err, errno))
> + goto disable_pmu;
> +
> + stack_amap_fd = bpf_find_map(__func__, obj, "stack_amap");
> + if (CHECK(stack_amap_fd < 0, "bpf_find_map stack_amap",
> + "err %d errno %d\n", err, errno))
> + goto disable_pmu;
> +
> + assert(system("dd if=/dev/urandom of=/dev/zero count=4 2> /dev/null")
> + == 0);
> + assert(system("taskset 0x1 ./urandom_read 100000") == 0);
> + /* disable stack trace collection */
> + key = 0;
> + val = 1;
> + bpf_map_update_elem(control_map_fd, &key, &val, 0);
> +
> + /* for every element in stackid_hmap, we can find a corresponding one
> + * in stackmap, and vise versa.
> + */
> + err = compare_map_keys(stackid_hmap_fd, stackmap_fd);
> + if (CHECK(err, "compare_map_keys stackid_hmap vs. stackmap",
> + "err %d errno %d\n", err, errno))
> + goto disable_pmu;
> +
> + err = compare_map_keys(stackmap_fd, stackid_hmap_fd);
> + if (CHECK(err, "compare_map_keys stackmap vs. stackid_hmap",
> + "err %d errno %d\n", err, errno))
> + goto disable_pmu;
> +
> + err = extract_build_id(buf, 256);
> +
> + if (CHECK(err, "get build_id with readelf",
> + "err %d errno %d\n", err, errno))
> + goto disable_pmu;
> +
> + err = bpf_map_get_next_key(stackmap_fd, NULL, &key);
> + if (CHECK(err, "get_next_key from stackmap",
> + "err %d, errno %d\n", err, errno))
> + goto disable_pmu;
> +
> + do {
> + char build_id[64];
> +
> + err = bpf_map_lookup_elem(stackmap_fd, &key, id_offs);
> + if (CHECK(err, "lookup_elem from stackmap",
> + "err %d, errno %d\n", err, errno))
> + goto disable_pmu;
> + for (i = 0; i < PERF_MAX_STACK_DEPTH; ++i)
> + if (id_offs[i].status == BPF_STACK_BUILD_ID_VALID &&
> + id_offs[i].offset != 0) {
> + for (j = 0; j < 20; ++j)
> + sprintf(build_id + 2 * j, "%02x",
> + id_offs[i].build_id[j] & 0xff);
> + if (strstr(buf, build_id) != NULL)
> + build_id_matches = 1;
> + }
> + previous_key = key;
> + } while (bpf_map_get_next_key(stackmap_fd, &previous_key, &key) == 0);
> +
> + if (CHECK(build_id_matches < 1, "build id match",
> + "Didn't find expected build ID from the map\n"))
> + goto disable_pmu;
> +
> + /*
> + * We intentionally skip compare_stack_ips(). This is because we
> + * only support one in_nmi() ips-to-build_id translation per cpu
> + * at any time, thus stack_amap here will always fallback to
> + * BPF_STACK_BUILD_ID_IP;
> + */
> +
> +disable_pmu:
> + ioctl(pmu_fd, PERF_EVENT_IOC_DISABLE);
> +
> +close_pmu:
> + close(pmu_fd);
> +
> +close_prog:
> + bpf_object__close(obj);
> +
> +out:
> + return;
> +}
No real need for label 'out' right? We can just return directly and
remove the last three lines of this function.
Hope this helps,
Tobin.
