tools/testing/selftests/bpf/test_stacktrace_build_id.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 // Copyright (c) 2018 Facebook
   3
   4 #include <linux/bpf.h>
   5 #include "bpf_helpers.h"
   6
   7 #ifndef PERF_MAX_STACK_DEPTH
   8 #define PERF_MAX_STACK_DEPTH         127
   9 #endif
  10
  11 struct bpf_map_def SEC("maps") control_map = {
  12         .type = BPF_MAP_TYPE_ARRAY,
  13         .key_size = sizeof(__u32),
  14         .value_size = sizeof(__u32),
  15         .max_entries = 1,
  16 };
  17
  18 struct bpf_map_def SEC("maps") stackid_hmap = {
  19         .type = BPF_MAP_TYPE_HASH,
  20         .key_size = sizeof(__u32),
  21         .value_size = sizeof(__u32),
  22         .max_entries = 16384,
  23 };
  24
  25 struct bpf_map_def SEC("maps") stackmap = {
  26         .type = BPF_MAP_TYPE_STACK_TRACE,
  27         .key_size = sizeof(__u32),
  28         .value_size = sizeof(struct bpf_stack_build_id)
  29                 * PERF_MAX_STACK_DEPTH,
  30         .max_entries = 128,
  31         .map_flags = BPF_F_STACK_BUILD_ID,
  32 };
  33
  34 struct bpf_map_def SEC("maps") stack_amap = {
  35         .type = BPF_MAP_TYPE_ARRAY,
  36         .key_size = sizeof(__u32),
  37         .value_size = sizeof(struct bpf_stack_build_id)
  38                 * PERF_MAX_STACK_DEPTH,
  39         .max_entries = 128,
  40 };
  41
  42 /* taken from /sys/kernel/debug/tracing/events/random/urandom_read/format */
  43 struct random_urandom_args {
  44         unsigned long long pad;
  45         int got_bits;
  46         int pool_left;
  47         int input_left;
  48 };
  49
  50 SEC("tracepoint/random/urandom_read")
  51 int oncpu(struct random_urandom_args *args)
  52 {
  53         __u32 max_len = sizeof(struct bpf_stack_build_id)
  54                         * PERF_MAX_STACK_DEPTH;
  55         __u32 key = 0, val = 0, *value_p;
  56         void *stack_p;
  57
  58         value_p = bpf_map_lookup_elem(&control_map, &key);
  59         if (value_p && *value_p)
  60                 return 0; /* skip if non-zero *value_p */
  61
  62         /* The size of stackmap and stackid_hmap should be the same */
  63         key = bpf_get_stackid(args, &stackmap, BPF_F_USER_STACK);
  64         if ((int)key >= 0) {
  65                 bpf_map_update_elem(&stackid_hmap, &key, &val, 0);
  66                 stack_p = bpf_map_lookup_elem(&stack_amap, &key);
  67                 if (stack_p)
  68                         bpf_get_stack(args, stack_p, max_len,
  69                                       BPF_F_USER_STACK | BPF_F_USER_BUILD_ID);
  70         }
  71
  72         return 0;
  73 }
  74
  75 char _license[] SEC("license") = "GPL";
  76 __u32 _version SEC("version") = 1; /* ignored by tracepoints, required by libbpf.a */