1 // SPDX-License-Identifier: GPL-2.0
2 // Copyright (c) 2020 Facebook
3 
4 #include <linux/bpf.h>
5 #include <bpf/bpf_helpers.h>
6 
7 char _license[] SEC("license") = "GPL";
8 
9 struct sample {
10 	int pid;
11 	int seq;
12 	long value;
13 	char comm[16];
14 };
15 
16 struct ringbuf_map {
17 	__uint(type, BPF_MAP_TYPE_RINGBUF);
18 	__uint(max_entries, 1 << 12);
19 } ringbuf1 SEC(".maps"),
20   ringbuf2 SEC(".maps");
21 
22 struct {
23 	__uint(type, BPF_MAP_TYPE_ARRAY_OF_MAPS);
24 	__uint(max_entries, 4);
25 	__type(key, int);
26 	__array(values, struct ringbuf_map);
27 } ringbuf_arr SEC(".maps") = {
28 	.values = {
29 		[0] = &ringbuf1,
30 		[2] = &ringbuf2,
31 	},
32 };
33 
34 /* inputs */
35 int pid = 0;
36 int target_ring = 0;
37 long value = 0;
38 
39 /* outputs */
40 long total = 0;
41 long dropped = 0;
42 long skipped = 0;
43 
44 SEC("tp/syscalls/sys_enter_getpgid")
45 int test_ringbuf(void *ctx)
46 {
47 	int cur_pid = bpf_get_current_pid_tgid() >> 32;
48 	struct sample *sample;
49 	void *rb;
50 	int zero = 0;
51 
52 	if (cur_pid != pid)
53 		return 0;
54 
55 	rb = bpf_map_lookup_elem(&ringbuf_arr, &target_ring);
56 	if (!rb) {
57 		skipped += 1;
58 		return 1;
59 	}
60 
61 	sample = bpf_ringbuf_reserve(rb, sizeof(*sample), 0);
62 	if (!sample) {
63 		dropped += 1;
64 		return 1;
65 	}
66 
67 	sample->pid = pid;
68 	bpf_get_current_comm(sample->comm, sizeof(sample->comm));
69 	sample->value = value;
70 
71 	sample->seq = total;
72 	total += 1;
73 
74 	bpf_ringbuf_submit(sample, 0);
75 
76 	return 0;
77 }
78