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

   1// SPDX-License-Identifier: GPL-2.0
   2#include <test_progs.h>
   3
   4static __u64 read_perf_max_sample_freq(void)
   5{
   6        __u64 sample_freq = 5000; /* fallback to 5000 on error */
   7        FILE *f;
   8
   9        f = fopen("/proc/sys/kernel/perf_event_max_sample_rate", "r");
  10        if (f == NULL)
  11                return sample_freq;
  12        fscanf(f, "%llu", &sample_freq);
  13        fclose(f);
  14        return sample_freq;
  15}
  16
  17void test_stacktrace_build_id_nmi(void)
  18{
  19        int control_map_fd, stackid_hmap_fd, stackmap_fd, stack_amap_fd;
  20        const char *prog_name = "tracepoint/random/urandom_read";
  21        const char *file = "./test_stacktrace_build_id.o";
  22        int err, pmu_fd, prog_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        struct bpf_program *prog;
  30        struct bpf_object *obj;
  31        struct bpf_link *link;
  32        char buf[256];
  33        int i, j;
  34        struct bpf_stack_build_id id_offs[PERF_MAX_STACK_DEPTH];
  35        int build_id_matches = 0;
  36        int retry = 1;
  37
  38        attr.sample_freq = read_perf_max_sample_freq();
  39
  40retry:
  41        err = bpf_prog_load(file, BPF_PROG_TYPE_PERF_EVENT, &obj, &prog_fd);
  42        if (CHECK(err, "prog_load", "err %d errno %d\n", err, errno))
  43                return;
  44
  45        prog = bpf_object__find_program_by_title(obj, prog_name);
  46        if (CHECK(!prog, "find_prog", "prog '%s' not found\n", prog_name))
  47                goto close_prog;
  48
  49        pmu_fd = syscall(__NR_perf_event_open, &attr, -1 /* pid */,
  50                         0 /* cpu 0 */, -1 /* group id */,
  51                         0 /* flags */);
  52        if (CHECK(pmu_fd < 0, "perf_event_open",
  53                  "err %d errno %d. Does the test host support PERF_COUNT_HW_CPU_CYCLES?\n",
  54                  pmu_fd, errno))
  55                goto close_prog;
  56
  57        link = bpf_program__attach_perf_event(prog, pmu_fd);
  58        if (CHECK(IS_ERR(link), "attach_perf_event",
  59                  "err %ld\n", PTR_ERR(link))) {
  60                close(pmu_fd);
  61                goto close_prog;
  62        }
  63
  64        /* find map fds */
  65        control_map_fd = bpf_find_map(__func__, obj, "control_map");
  66        if (CHECK(control_map_fd < 0, "bpf_find_map control_map",
  67                  "err %d errno %d\n", err, errno))
  68                goto disable_pmu;
  69
  70        stackid_hmap_fd = bpf_find_map(__func__, obj, "stackid_hmap");
  71        if (CHECK(stackid_hmap_fd < 0, "bpf_find_map stackid_hmap",
  72                  "err %d errno %d\n", err, errno))
  73                goto disable_pmu;
  74
  75        stackmap_fd = bpf_find_map(__func__, obj, "stackmap");
  76        if (CHECK(stackmap_fd < 0, "bpf_find_map stackmap", "err %d errno %d\n",
  77                  err, errno))
  78                goto disable_pmu;
  79
  80        stack_amap_fd = bpf_find_map(__func__, obj, "stack_amap");
  81        if (CHECK(stack_amap_fd < 0, "bpf_find_map stack_amap",
  82                  "err %d errno %d\n", err, errno))
  83                goto disable_pmu;
  84
  85        if (CHECK_FAIL(system("dd if=/dev/urandom of=/dev/zero count=4 2> /dev/null")))
  86                goto disable_pmu;
  87        if (CHECK_FAIL(system("taskset 0x1 ./urandom_read 100000")))
  88                goto disable_pmu;
  89        /* disable stack trace collection */
  90        key = 0;
  91        val = 1;
  92        bpf_map_update_elem(control_map_fd, &key, &val, 0);
  93
  94        /* for every element in stackid_hmap, we can find a corresponding one
  95         * in stackmap, and vise versa.
  96         */
  97        err = compare_map_keys(stackid_hmap_fd, stackmap_fd);
  98        if (CHECK(err, "compare_map_keys stackid_hmap vs. stackmap",
  99                  "err %d errno %d\n", err, errno))
 100                goto disable_pmu;
 101
 102        err = compare_map_keys(stackmap_fd, stackid_hmap_fd);
 103        if (CHECK(err, "compare_map_keys stackmap vs. stackid_hmap",
 104                  "err %d errno %d\n", err, errno))
 105                goto disable_pmu;
 106
 107        err = extract_build_id(buf, 256);
 108
 109        if (CHECK(err, "get build_id with readelf",
 110                  "err %d errno %d\n", err, errno))
 111                goto disable_pmu;
 112
 113        err = bpf_map_get_next_key(stackmap_fd, NULL, &key);
 114        if (CHECK(err, "get_next_key from stackmap",
 115                  "err %d, errno %d\n", err, errno))
 116                goto disable_pmu;
 117
 118        do {
 119                char build_id[64];
 120
 121                err = bpf_map_lookup_elem(stackmap_fd, &key, id_offs);
 122                if (CHECK(err, "lookup_elem from stackmap",
 123                          "err %d, errno %d\n", err, errno))
 124                        goto disable_pmu;
 125                for (i = 0; i < PERF_MAX_STACK_DEPTH; ++i)
 126                        if (id_offs[i].status == BPF_STACK_BUILD_ID_VALID &&
 127                            id_offs[i].offset != 0) {
 128                                for (j = 0; j < 20; ++j)
 129                                        sprintf(build_id + 2 * j, "%02x",
 130                                                id_offs[i].build_id[j] & 0xff);
 131                                if (strstr(buf, build_id) != NULL)
 132                                        build_id_matches = 1;
 133                        }
 134                previous_key = key;
 135        } while (bpf_map_get_next_key(stackmap_fd, &previous_key, &key) == 0);
 136
 137        /* stack_map_get_build_id_offset() is racy and sometimes can return
 138         * BPF_STACK_BUILD_ID_IP instead of BPF_STACK_BUILD_ID_VALID;
 139         * try it one more time.
 140         */
 141        if (build_id_matches < 1 && retry--) {
 142                bpf_link__destroy(link);
 143                bpf_object__close(obj);
 144                printf("%s:WARN:Didn't find expected build ID from the map, retrying\n",
 145                       __func__);
 146                goto retry;
 147        }
 148
 149        if (CHECK(build_id_matches < 1, "build id match",
 150                  "Didn't find expected build ID from the map\n"))
 151                goto disable_pmu;
 152
 153        /*
 154         * We intentionally skip compare_stack_ips(). This is because we
 155         * only support one in_nmi() ips-to-build_id translation per cpu
 156         * at any time, thus stack_amap here will always fallback to
 157         * BPF_STACK_BUILD_ID_IP;
 158         */
 159
 160disable_pmu:
 161        bpf_link__destroy(link);
 162close_prog:
 163        bpf_object__close(obj);
 164}
 165