root/tools/testing/selftests/bpf/prog_tests/stacktrace_build_id.c

DEFINITIONS

1. test_stacktrace_build_id

   1 // SPDX-License-Identifier: GPL-2.0
   2 #include <test_progs.h>
   3 
   4 void test_stacktrace_build_id(void)
   5 {
   6         int control_map_fd, stackid_hmap_fd, stackmap_fd, stack_amap_fd;
   7         const char *prog_name = "tracepoint/random/urandom_read";
   8         const char *file = "./test_stacktrace_build_id.o";
   9         int err, prog_fd, stack_trace_len;
  10         __u32 key, previous_key, val, duration = 0;
  11         struct bpf_program *prog;
  12         struct bpf_object *obj;
  13         struct bpf_link *link = NULL;
  14         char buf[256];
  15         int i, j;
  16         struct bpf_stack_build_id id_offs[PERF_MAX_STACK_DEPTH];
  17         int build_id_matches = 0;
  18         int retry = 1;
  19 
  20 retry:
  21         err = bpf_prog_load(file, BPF_PROG_TYPE_TRACEPOINT, &obj, &prog_fd);
  22         if (CHECK(err, "prog_load", "err %d errno %d\n", err, errno))
  23                 return;
  24 
  25         prog = bpf_object__find_program_by_title(obj, prog_name);
  26         if (CHECK(!prog, "find_prog", "prog '%s' not found\n", prog_name))
  27                 goto close_prog;
  28 
  29         link = bpf_program__attach_tracepoint(prog, "random", "urandom_read");
  30         if (CHECK(IS_ERR(link), "attach_tp", "err %ld\n", PTR_ERR(link)))
  31                 goto close_prog;
  32 
  33         /* find map fds */
  34         control_map_fd = bpf_find_map(__func__, obj, "control_map");
  35         if (CHECK(control_map_fd < 0, "bpf_find_map control_map",
  36                   "err %d errno %d\n", err, errno))
  37                 goto disable_pmu;
  38 
  39         stackid_hmap_fd = bpf_find_map(__func__, obj, "stackid_hmap");
  40         if (CHECK(stackid_hmap_fd < 0, "bpf_find_map stackid_hmap",
  41                   "err %d errno %d\n", err, errno))
  42                 goto disable_pmu;
  43 
  44         stackmap_fd = bpf_find_map(__func__, obj, "stackmap");
  45         if (CHECK(stackmap_fd < 0, "bpf_find_map stackmap", "err %d errno %d\n",
  46                   err, errno))
  47                 goto disable_pmu;
  48 
  49         stack_amap_fd = bpf_find_map(__func__, obj, "stack_amap");
  50         if (CHECK(stack_amap_fd < 0, "bpf_find_map stack_amap",
  51                   "err %d errno %d\n", err, errno))
  52                 goto disable_pmu;
  53 
  54         if (CHECK_FAIL(system("dd if=/dev/urandom of=/dev/zero count=4 2> /dev/null")))
  55                 goto disable_pmu;
  56         if (CHECK_FAIL(system("./urandom_read")))
  57                 goto disable_pmu;
  58         /* disable stack trace collection */
  59         key = 0;
  60         val = 1;
  61         bpf_map_update_elem(control_map_fd, &key, &val, 0);
  62 
  63         /* for every element in stackid_hmap, we can find a corresponding one
  64          * in stackmap, and vise versa.
  65          */
  66         err = compare_map_keys(stackid_hmap_fd, stackmap_fd);
  67         if (CHECK(err, "compare_map_keys stackid_hmap vs. stackmap",
  68                   "err %d errno %d\n", err, errno))
  69                 goto disable_pmu;
  70 
  71         err = compare_map_keys(stackmap_fd, stackid_hmap_fd);
  72         if (CHECK(err, "compare_map_keys stackmap vs. stackid_hmap",
  73                   "err %d errno %d\n", err, errno))
  74                 goto disable_pmu;
  75 
  76         err = extract_build_id(buf, 256);
  77 
  78         if (CHECK(err, "get build_id with readelf",
  79                   "err %d errno %d\n", err, errno))
  80                 goto disable_pmu;
  81 
  82         err = bpf_map_get_next_key(stackmap_fd, NULL, &key);
  83         if (CHECK(err, "get_next_key from stackmap",
  84                   "err %d, errno %d\n", err, errno))
  85                 goto disable_pmu;
  86 
  87         do {
  88                 char build_id[64];
  89 
  90                 err = bpf_map_lookup_elem(stackmap_fd, &key, id_offs);
  91                 if (CHECK(err, "lookup_elem from stackmap",
  92                           "err %d, errno %d\n", err, errno))
  93                         goto disable_pmu;
  94                 for (i = 0; i < PERF_MAX_STACK_DEPTH; ++i)
  95                         if (id_offs[i].status == BPF_STACK_BUILD_ID_VALID &&
  96                             id_offs[i].offset != 0) {
  97                                 for (j = 0; j < 20; ++j)
  98                                         sprintf(build_id + 2 * j, "%02x",
  99                                                 id_offs[i].build_id[j] & 0xff);
 100                                 if (strstr(buf, build_id) != NULL)
 101                                         build_id_matches = 1;
 102                         }
 103                 previous_key = key;
 104         } while (bpf_map_get_next_key(stackmap_fd, &previous_key, &key) == 0);
 105 
 106         /* stack_map_get_build_id_offset() is racy and sometimes can return
 107          * BPF_STACK_BUILD_ID_IP instead of BPF_STACK_BUILD_ID_VALID;
 108          * try it one more time.
 109          */
 110         if (build_id_matches < 1 && retry--) {
 111                 bpf_link__destroy(link);
 112                 bpf_object__close(obj);
 113                 printf("%s:WARN:Didn't find expected build ID from the map, retrying\n",
 114                        __func__);
 115                 goto retry;
 116         }
 117 
 118         if (CHECK(build_id_matches < 1, "build id match",
 119                   "Didn't find expected build ID from the map\n"))
 120                 goto disable_pmu;
 121 
 122         stack_trace_len = PERF_MAX_STACK_DEPTH
 123                 * sizeof(struct bpf_stack_build_id);
 124         err = compare_stack_ips(stackmap_fd, stack_amap_fd, stack_trace_len);
 125         CHECK(err, "compare_stack_ips stackmap vs. stack_amap",
 126               "err %d errno %d\n", err, errno);
 127 
 128 disable_pmu:
 129         bpf_link__destroy(link);
 130 
 131 close_prog:
 132         bpf_object__close(obj);
 133 }