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