1// SPDX-License-Identifier: GPL-2.0
2// Copyright (c) 2018 Facebook
3
4#include <linux/bpf.h>
5#include <bpf/bpf_helpers.h>
6
7#ifndef PERF_MAX_STACK_DEPTH
8#define PERF_MAX_STACK_DEPTH 127
9#endif
10
11struct {
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
18struct {
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
25typedef struct bpf_stack_build_id stack_trace_t[PERF_MAX_STACK_DEPTH];
26
27struct {
28 __uint(type, BPF_MAP_TYPE_STACK_TRACE);
29 __uint(max_entries, 128);
30 __uint(map_flags, BPF_F_STACK_BUILD_ID);
31 __type(key, __u32);
32 __type(value, stack_trace_t);
33} stackmap SEC(".maps");
34
35struct {
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
42SEC("kprobe/urandom_read_iter")
43int oncpu(struct pt_regs *args)
44{
45 __u32 max_len = sizeof(struct bpf_stack_build_id)
46 * PERF_MAX_STACK_DEPTH;
47 __u32 key = 0, val = 0, *value_p;
48 void *stack_p;
49
50 value_p = bpf_map_lookup_elem(&control_map, &key);
51 if (value_p && *value_p)
52 return 0; /* skip if non-zero *value_p */
53
54 /* The size of stackmap and stackid_hmap should be the same */
55 key = bpf_get_stackid(args, &stackmap, BPF_F_USER_STACK);
56 if ((int)key >= 0) {
57 bpf_map_update_elem(&stackid_hmap, &key, &val, 0);
58 stack_p = bpf_map_lookup_elem(&stack_amap, &key);
59 if (stack_p)
60 bpf_get_stack(args, stack_p, max_len,
61 BPF_F_USER_STACK | BPF_F_USER_BUILD_ID);
62 }
63
64 return 0;
65}
66
67char _license[] SEC("license") = "GPL";
68

source code of linux/tools/testing/selftests/bpf/progs/test_stacktrace_build_id.c