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
 7char _license[] SEC("license") = "GPL";
 8
 9struct {
10	__uint(type, BPF_MAP_TYPE_RINGBUF);
11} ringbuf SEC(".maps");
12
13/* inputs */
14int pid = 0;
15
16/* outputs */
17long passed = 0;
18long discarded = 0;
19
20SEC("fentry/" SYS_PREFIX "sys_getpgid")
21int 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}