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

   1 // SPDX-License-Identifier: GPL-2.0
   2
   3 #include <linux/bpf.h>
   4 #include <bpf/bpf_helpers.h>
   5 #include "bpf_misc.h"
   6
   7 char _license[] SEC("license") = "GPL";
   8
   9 struct {
  10         __uint(type, BPF_MAP_TYPE_RINGBUF);
  11 } ringbuf SEC(".maps");
  12
  13 /* inputs */
  14 int pid = 0;
  15
  16 /* outputs */
  17 long passed = 0;
  18 long discarded = 0;
  19
  20 SEC("fentry/" SYS_PREFIX "sys_getpgid")
  21 int test_ringbuf_write(void *ctx)
  22 {
  23         int *foo, cur_pid = bpf_get_current_pid_tgid() >> 32;
  24         void *sample1, *sample2;
  25
  26         if (cur_pid != pid)
  27                 return 0;
  28
  29         sample1 = bpf_ringbuf_reserve(&ringbuf, 0x3000, 0);
  30         if (!sample1)
  31                 return 0;
  32         /* first one can pass */
  33         sample2 = bpf_ringbuf_reserve(&ringbuf, 0x3000, 0);
  34         if (!sample2) {
  35                 bpf_ringbuf_discard(sample1, 0);
  36                 __sync_fetch_and_add(&discarded, 1);
  37                 return 0;
  38         }
  39         /* second one must not */
  40         __sync_fetch_and_add(&passed, 1);
  41         foo = sample2 + 4084;
  42         *foo = 256;
  43         bpf_ringbuf_discard(sample1, 0);
  44         bpf_ringbuf_discard(sample2, 0);
  45         return 0;
  46 }