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#include "bpf_misc.h" 7 8char _license[] SEC("license") = "GPL"; 9 10struct sample { 11 int pid; 12 int seq; 13 long value; 14 char comm[16]; 15}; 16 17struct { 18 __uint(type, BPF_MAP_TYPE_RINGBUF); 19} ringbuf SEC(".maps"); 20 21/* inputs */ 22int pid = 0; 23long value = 0; 24long flags = 0; 25 26/* outputs */ 27long total = 0; 28long discarded = 0; 29long dropped = 0; 30 31long avail_data = 0; 32long ring_size = 0; 33long cons_pos = 0; 34long prod_pos = 0; 35 36/* inner state */ 37long seq = 0; 38 39SEC("fentry/" SYS_PREFIX "sys_getpgid") 40int test_ringbuf(void *ctx) 41{ 42 int cur_pid = bpf_get_current_pid_tgid() >> 32; 43 struct sample *sample; 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} 78