Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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kernel
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linux
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
11struct 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
18struct 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
25struct 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
34struct 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 */
43struct random_urandom_args {
44 unsigned long long pad;
45 int got_bits;
46 int pool_left;
47 int input_left;
48};
49
50SEC("tracepoint/random/urandom_read")
51int 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
75char _license[] SEC("license") = "GPL";
76__u32 _version SEC("version") = 1; /* ignored by tracepoints, required by libbpf.a */