root/tools/testing/selftests/bpf/progs/test_stacktrace_build_id.c

DEFINITIONS

1. SEC

   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 {
  12         __uint(type, BPF_MAP_TYPE_ARRAY);
  13         __uint(max_entries, 1);
  14         __type(key, __u32);
  15         __type(value, __u32);
  16 } control_map SEC(".maps");
  17 
  18 struct {
  19         __uint(type, BPF_MAP_TYPE_HASH);
  20         __uint(max_entries, 16384);
  21         __type(key, __u32);
  22         __type(value, __u32);
  23 } stackid_hmap SEC(".maps");
  24 
  25 typedef struct bpf_stack_build_id stack_trace_t[PERF_MAX_STACK_DEPTH];
  26 
  27 struct {
  28         __uint(type, BPF_MAP_TYPE_STACK_TRACE);
  29         __uint(max_entries, 128);
  30         __uint(map_flags, BPF_F_STACK_BUILD_ID);
  31         __uint(key_size, sizeof(__u32));
  32         __uint(value_size, sizeof(stack_trace_t));
  33 } stackmap SEC(".maps");
  34 
  35 struct {
  36         __uint(type, BPF_MAP_TYPE_ARRAY);
  37         __uint(max_entries, 128);
  38         __type(key, __u32);
  39         __type(value, stack_trace_t);
  40 } stack_amap SEC(".maps");
  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 */