LXR linux/tools/testing/selftests/bpf/prog_tests/stacktrace_build_id

   1// SPDX-License-Identifier: GPL-2.0
   2#include <test_progs.h>
   3#include "test_stacktrace_build_id.skel.h"
   4
   5static __u64 read_perf_max_sample_freq(void)
   6{
   7        __u64 sample_freq = 5000; /* fallback to 5000 on error */
   8        FILE *f;
   9
  10        f = fopen("/proc/sys/kernel/perf_event_max_sample_rate", "r");
  11        if (f == NULL)
  12                return sample_freq;
  13        fscanf(f, "%llu", &sample_freq);
  14        fclose(f);
  15        return sample_freq;
  16}
  17
  18void test_stacktrace_build_id_nmi(void)
  19{
  20        int control_map_fd, stackid_hmap_fd, stackmap_fd;
  21        struct test_stacktrace_build_id *skel;
  22        int err, pmu_fd;
  23        struct perf_event_attr attr = {
  24                .freq = 1,
  25                .type = PERF_TYPE_HARDWARE,
  26                .config = PERF_COUNT_HW_CPU_CYCLES,
  27        };
  28        __u32 key, previous_key, val, duration = 0;
  29        char buf[256];
  30        int i, j;
  31        struct bpf_stack_build_id id_offs[PERF_MAX_STACK_DEPTH];
  32        int build_id_matches = 0;
  33        int retry = 1;
  34
  35        attr.sample_freq = read_perf_max_sample_freq();
  36
  37retry:
  38        skel = test_stacktrace_build_id__open();
  39        if (CHECK(!skel, "skel_open", "skeleton open failed\n"))
  40                return;
  41
  42        /* override program type */
  43        bpf_program__set_perf_event(skel->progs.oncpu);
  44
  45        err = test_stacktrace_build_id__load(skel);
  46        if (CHECK(err, "skel_load", "skeleton load failed: %d\n", err))
  47                goto cleanup;
  48
  49        pmu_fd = syscall(__NR_perf_event_open, &attr, -1 /* pid */,
  50                         0 /* cpu 0 */, -1 /* group id */,
  51                         0 /* flags */);
  52        if (pmu_fd < 0 && errno == ENOENT) {
  53                printf("%s:SKIP:no PERF_COUNT_HW_CPU_CYCLES\n", __func__);
  54                test__skip();
  55                goto cleanup;
  56        }
  57        if (CHECK(pmu_fd < 0, "perf_event_open", "err %d errno %d\n",
  58                  pmu_fd, errno))
  59                goto cleanup;
  60
  61        skel->links.oncpu = bpf_program__attach_perf_event(skel->progs.oncpu,
  62                                                           pmu_fd);
  63        if (CHECK(IS_ERR(skel->links.oncpu), "attach_perf_event",
  64                  "err %ld\n", PTR_ERR(skel->links.oncpu))) {
  65                close(pmu_fd);
  66                goto cleanup;
  67        }
  68
  69        /* find map fds */
  70        control_map_fd = bpf_map__fd(skel->maps.control_map);
  71        stackid_hmap_fd = bpf_map__fd(skel->maps.stackid_hmap);
  72        stackmap_fd = bpf_map__fd(skel->maps.stackmap);
  73
  74        if (CHECK_FAIL(system("dd if=/dev/urandom of=/dev/zero count=4 2> /dev/null")))
  75                goto cleanup;
  76        if (CHECK_FAIL(system("taskset 0x1 ./urandom_read 100000")))
  77                goto cleanup;
  78        /* disable stack trace collection */
  79        key = 0;
  80        val = 1;
  81        bpf_map_update_elem(control_map_fd, &key, &val, 0);
  82
  83        /* for every element in stackid_hmap, we can find a corresponding one
  84         * in stackmap, and vise versa.
  85         */
  86        err = compare_map_keys(stackid_hmap_fd, stackmap_fd);
  87        if (CHECK(err, "compare_map_keys stackid_hmap vs. stackmap",
  88                  "err %d errno %d\n", err, errno))
  89                goto cleanup;
  90
  91        err = compare_map_keys(stackmap_fd, stackid_hmap_fd);
  92        if (CHECK(err, "compare_map_keys stackmap vs. stackid_hmap",
  93                  "err %d errno %d\n", err, errno))
  94                goto cleanup;
  95
  96        err = extract_build_id(buf, 256);
  97
  98        if (CHECK(err, "get build_id with readelf",
  99                  "err %d errno %d\n", err, errno))
 100                goto cleanup;
 101
 102        err = bpf_map_get_next_key(stackmap_fd, NULL, &key);
 103        if (CHECK(err, "get_next_key from stackmap",
 104                  "err %d, errno %d\n", err, errno))
 105                goto cleanup;
 106
 107        do {
 108                char build_id[64];
 109
 110                err = bpf_map_lookup_elem(stackmap_fd, &key, id_offs);
 111                if (CHECK(err, "lookup_elem from stackmap",
 112                          "err %d, errno %d\n", err, errno))
 113                        goto cleanup;
 114                for (i = 0; i < PERF_MAX_STACK_DEPTH; ++i)
 115                        if (id_offs[i].status == BPF_STACK_BUILD_ID_VALID &&
 116                            id_offs[i].offset != 0) {
 117                                for (j = 0; j < 20; ++j)
 118                                        sprintf(build_id + 2 * j, "%02x",
 119                                                id_offs[i].build_id[j] & 0xff);
 120                                if (strstr(buf, build_id) != NULL)
 121                                        build_id_matches = 1;
 122                        }
 123                previous_key = key;
 124        } while (bpf_map_get_next_key(stackmap_fd, &previous_key, &key) == 0);
 125
 126        /* stack_map_get_build_id_offset() is racy and sometimes can return
 127         * BPF_STACK_BUILD_ID_IP instead of BPF_STACK_BUILD_ID_VALID;
 128         * try it one more time.
 129         */
 130        if (build_id_matches < 1 && retry--) {
 131                test_stacktrace_build_id__destroy(skel);
 132                printf("%s:WARN:Didn't find expected build ID from the map, retrying\n",
 133                       __func__);
 134                goto retry;
 135        }
 136
 137        if (CHECK(build_id_matches < 1, "build id match",
 138                  "Didn't find expected build ID from the map\n"))
 139                goto cleanup;
 140
 141        /*
 142         * We intentionally skip compare_stack_ips(). This is because we
 143         * only support one in_nmi() ips-to-build_id translation per cpu
 144         * at any time, thus stack_amap here will always fallback to
 145         * BPF_STACK_BUILD_ID_IP;
 146         */
 147
 148cleanup:
 149        test_stacktrace_build_id__destroy(skel);
 150}
 151