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// SPDX-License-Identifier: GPL-2.0
// Copyright (c) 2020 Facebook
#include <linux/bpf.h>
#include <bpf/bpf_helpers.h>
char _license[] SEC("license") = "GPL";
struct sample {
int pid;
int seq;
long value;
char comm[16];
};
struct {
__uint(type, BPF_MAP_TYPE_RINGBUF);
__uint(max_entries, 1 << 12);
} ringbuf SEC(".maps");
/* inputs */
int pid = 0;
long value = 0;
long flags = 0;
/* outputs */
long total = 0;
long discarded = 0;
long dropped = 0;
long avail_data = 0;
long ring_size = 0;
long cons_pos = 0;
long prod_pos = 0;
/* inner state */
long seq = 0;
SEC("tp/syscalls/sys_enter_getpgid")
int test_ringbuf(void *ctx)
{
int cur_pid = bpf_get_current_pid_tgid() >> 32;
struct sample *sample;
int zero = 0;
if (cur_pid != pid)
return 0;
sample = bpf_ringbuf_reserve(&ringbuf, sizeof(*sample), 0);
if (!sample) {
__sync_fetch_and_add(&dropped, 1);
return 1;
}
sample->pid = pid;
bpf_get_current_comm(sample->comm, sizeof(sample->comm));
sample->value = value;
sample->seq = seq++;
__sync_fetch_and_add(&total, 1);
if (sample->seq & 1) {
/* copy from reserved sample to a new one... */
bpf_ringbuf_output(&ringbuf, sample, sizeof(*sample), flags);
/* ...and then discard reserved sample */
bpf_ringbuf_discard(sample, flags);
__sync_fetch_and_add(&discarded, 1);
} else {
bpf_ringbuf_submit(sample, flags);
}
avail_data = bpf_ringbuf_query(&ringbuf, BPF_RB_AVAIL_DATA);
ring_size = bpf_ringbuf_query(&ringbuf, BPF_RB_RING_SIZE);
cons_pos = bpf_ringbuf_query(&ringbuf, BPF_RB_CONS_POS);
prod_pos = bpf_ringbuf_query(&ringbuf, BPF_RB_PROD_POS);
return 0;
}
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