1*4882a593Smuzhiyun // SPDX-License-Identifier: GPL-2.0
2*4882a593Smuzhiyun // Copyright (c) 2020 Facebook
3*4882a593Smuzhiyun
4*4882a593Smuzhiyun #include <linux/bpf.h>
5*4882a593Smuzhiyun #include <bpf/bpf_helpers.h>
6*4882a593Smuzhiyun
7*4882a593Smuzhiyun char _license[] SEC("license") = "GPL";
8*4882a593Smuzhiyun
9*4882a593Smuzhiyun struct sample {
10*4882a593Smuzhiyun int pid;
11*4882a593Smuzhiyun int seq;
12*4882a593Smuzhiyun long value;
13*4882a593Smuzhiyun char comm[16];
14*4882a593Smuzhiyun };
15*4882a593Smuzhiyun
16*4882a593Smuzhiyun struct {
17*4882a593Smuzhiyun __uint(type, BPF_MAP_TYPE_RINGBUF);
18*4882a593Smuzhiyun __uint(max_entries, 1 << 12);
19*4882a593Smuzhiyun } ringbuf SEC(".maps");
20*4882a593Smuzhiyun
21*4882a593Smuzhiyun /* inputs */
22*4882a593Smuzhiyun int pid = 0;
23*4882a593Smuzhiyun long value = 0;
24*4882a593Smuzhiyun long flags = 0;
25*4882a593Smuzhiyun
26*4882a593Smuzhiyun /* outputs */
27*4882a593Smuzhiyun long total = 0;
28*4882a593Smuzhiyun long discarded = 0;
29*4882a593Smuzhiyun long dropped = 0;
30*4882a593Smuzhiyun
31*4882a593Smuzhiyun long avail_data = 0;
32*4882a593Smuzhiyun long ring_size = 0;
33*4882a593Smuzhiyun long cons_pos = 0;
34*4882a593Smuzhiyun long prod_pos = 0;
35*4882a593Smuzhiyun
36*4882a593Smuzhiyun /* inner state */
37*4882a593Smuzhiyun long seq = 0;
38*4882a593Smuzhiyun
39*4882a593Smuzhiyun SEC("tp/syscalls/sys_enter_getpgid")
test_ringbuf(void * ctx)40*4882a593Smuzhiyun int test_ringbuf(void *ctx)
41*4882a593Smuzhiyun {
42*4882a593Smuzhiyun int cur_pid = bpf_get_current_pid_tgid() >> 32;
43*4882a593Smuzhiyun struct sample *sample;
44*4882a593Smuzhiyun int zero = 0;
45*4882a593Smuzhiyun
46*4882a593Smuzhiyun if (cur_pid != pid)
47*4882a593Smuzhiyun return 0;
48*4882a593Smuzhiyun
49*4882a593Smuzhiyun sample = bpf_ringbuf_reserve(&ringbuf, sizeof(*sample), 0);
50*4882a593Smuzhiyun if (!sample) {
51*4882a593Smuzhiyun __sync_fetch_and_add(&dropped, 1);
52*4882a593Smuzhiyun return 1;
53*4882a593Smuzhiyun }
54*4882a593Smuzhiyun
55*4882a593Smuzhiyun sample->pid = pid;
56*4882a593Smuzhiyun bpf_get_current_comm(sample->comm, sizeof(sample->comm));
57*4882a593Smuzhiyun sample->value = value;
58*4882a593Smuzhiyun
59*4882a593Smuzhiyun sample->seq = seq++;
60*4882a593Smuzhiyun __sync_fetch_and_add(&total, 1);
61*4882a593Smuzhiyun
62*4882a593Smuzhiyun if (sample->seq & 1) {
63*4882a593Smuzhiyun /* copy from reserved sample to a new one... */
64*4882a593Smuzhiyun bpf_ringbuf_output(&ringbuf, sample, sizeof(*sample), flags);
65*4882a593Smuzhiyun /* ...and then discard reserved sample */
66*4882a593Smuzhiyun bpf_ringbuf_discard(sample, flags);
67*4882a593Smuzhiyun __sync_fetch_and_add(&discarded, 1);
68*4882a593Smuzhiyun } else {
69*4882a593Smuzhiyun bpf_ringbuf_submit(sample, flags);
70*4882a593Smuzhiyun }
71*4882a593Smuzhiyun
72*4882a593Smuzhiyun avail_data = bpf_ringbuf_query(&ringbuf, BPF_RB_AVAIL_DATA);
73*4882a593Smuzhiyun ring_size = bpf_ringbuf_query(&ringbuf, BPF_RB_RING_SIZE);
74*4882a593Smuzhiyun cons_pos = bpf_ringbuf_query(&ringbuf, BPF_RB_CONS_POS);
75*4882a593Smuzhiyun prod_pos = bpf_ringbuf_query(&ringbuf, BPF_RB_PROD_POS);
76*4882a593Smuzhiyun
77*4882a593Smuzhiyun return 0;
78*4882a593Smuzhiyun }
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