tools/testing/selftests/bpf/progs/test_ringbuf.c

   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 {
  17         __uint(type, BPF_MAP_TYPE_RINGBUF);
  18         __uint(max_entries, 1 << 12);
  19 } ringbuf SEC(".maps");
  20
  21 /* inputs */
  22 int pid = 0;
  23 long value = 0;
  24 long flags = 0;
  25
  26 /* outputs */
  27 long total = 0;
  28 long discarded = 0;
  29 long dropped = 0;
  30
  31 long avail_data = 0;
  32 long ring_size = 0;
  33 long cons_pos = 0;
  34 long prod_pos = 0;
  35
  36 /* inner state */
  37 long seq = 0;
  38
  39 SEC("tp/syscalls/sys_enter_getpgid")
  40 int test_ringbuf(void *ctx)
  41 {
  42         int cur_pid = bpf_get_current_pid_tgid() >> 32;
  43         struct sample *sample;
  44         int zero = 0;
  45
  46         if (cur_pid != pid)
  47                 return 0;
  48
  49         sample = bpf_ringbuf_reserve(&ringbuf, sizeof(*sample), 0);
  50         if (!sample) {
  51                 __sync_fetch_and_add(&dropped, 1);
  52                 return 1;
  53         }
  54
  55         sample->pid = pid;
  56         bpf_get_current_comm(sample->comm, sizeof(sample->comm));
  57         sample->value = value;
  58
  59         sample->seq = seq++;
  60         __sync_fetch_and_add(&total, 1);
  61
  62         if (sample->seq & 1) {
  63                 /* copy from reserved sample to a new one... */
  64                 bpf_ringbuf_output(&ringbuf, sample, sizeof(*sample), flags);
  65                 /* ...and then discard reserved sample */
  66                 bpf_ringbuf_discard(sample, flags);
  67                 __sync_fetch_and_add(&discarded, 1);
  68         } else {
  69                 bpf_ringbuf_submit(sample, flags);
  70         }
  71
  72         avail_data = bpf_ringbuf_query(&ringbuf, BPF_RB_AVAIL_DATA);
  73         ring_size = bpf_ringbuf_query(&ringbuf, BPF_RB_RING_SIZE);
  74         cons_pos = bpf_ringbuf_query(&ringbuf, BPF_RB_CONS_POS);
  75         prod_pos = bpf_ringbuf_query(&ringbuf, BPF_RB_PROD_POS);
  76
  77         return 0;
  78 }