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 } ringbuf SEC(".maps"); 19 20 /* inputs */ 21 int pid = 0; 22 long value = 0; 23 long flags = 0; 24 25 /* outputs */ 26 long total = 0; 27 long discarded = 0; 28 long dropped = 0; 29 30 long avail_data = 0; 31 long ring_size = 0; 32 long cons_pos = 0; 33 long prod_pos = 0; 34 35 /* inner state */ 36 long seq = 0; 37 38 SEC("tp/syscalls/sys_enter_getpgid") 39 int test_ringbuf(void *ctx) 40 { 41 int cur_pid = bpf_get_current_pid_tgid() >> 32; 42 struct sample *sample; 43 int zero = 0; 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 1; 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