tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
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
7char _license[] SEC("license") = "GPL";
8
9struct sample {
10 int pid;
11 int seq;
12 long value;
13 char comm[16];
14};
15
16struct {
17 __uint(type, BPF_MAP_TYPE_RINGBUF);
18} ringbuf SEC(".maps");
19
20/* inputs */
21int pid = 0;
22long value = 0;
23long flags = 0;
24
25/* outputs */
26long total = 0;
27long discarded = 0;
28long dropped = 0;
29
30long avail_data = 0;
31long ring_size = 0;
32long cons_pos = 0;
33long prod_pos = 0;
34
35/* inner state */
36long seq = 0;
37
38SEC("fentry/__x64_sys_getpgid")
39int test_ringbuf(void *ctx)
40{
41 int cur_pid = bpf_get_current_pid_tgid() >> 32;
42 struct sample *sample;
43 int zero = 0;
44
45 if (cur_pid != pid)
46 return 0;
47
48 sample = bpf_ringbuf_reserve(&ringbuf, sizeof(*sample), 0);
49 if (!sample) {
50 __sync_fetch_and_add(&dropped, 1);
51 return 0;
52 }
53
54 sample->pid = pid;
55 bpf_get_current_comm(sample->comm, sizeof(sample->comm));
56 sample->value = value;
57
58 sample->seq = seq++;
59 __sync_fetch_and_add(&total, 1);
60
61 if (sample->seq & 1) {
62 /* copy from reserved sample to a new one... */
63 bpf_ringbuf_output(&ringbuf, sample, sizeof(*sample), flags);
64 /* ...and then discard reserved sample */
65 bpf_ringbuf_discard(sample, flags);
66 __sync_fetch_and_add(&discarded, 1);
67 } else {
68 bpf_ringbuf_submit(sample, flags);
69 }
70
71 avail_data = bpf_ringbuf_query(&ringbuf, BPF_RB_AVAIL_DATA);
72 ring_size = bpf_ringbuf_query(&ringbuf, BPF_RB_RING_SIZE);
73 cons_pos = bpf_ringbuf_query(&ringbuf, BPF_RB_CONS_POS);
74 prod_pos = bpf_ringbuf_query(&ringbuf, BPF_RB_PROD_POS);
75
76 return 0;
77}