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 __uint(max_entries, 1 << 12); 19 } ringbuf SEC(".maps"); 20 21 /* inputs */ 22 int pid = 0; 23 long value = 0; 24 long flags = 0; 25 26 /* outputs */ 27 long total = 0; 28 long discarded = 0; 29 long dropped = 0; 30 31 long avail_data = 0; 32 long ring_size = 0; 33 long cons_pos = 0; 34 long prod_pos = 0; 35 36 /* inner state */ 37 long seq = 0; 38 39 SEC("tp/syscalls/sys_enter_getpgid") 40 int test_ringbuf(void *ctx) 41 { 42 int cur_pid = bpf_get_current_pid_tgid() >> 32; 43 struct sample *sample; 44 int zero = 0; 45 46 if (cur_pid != pid) 47 return 0; 48 49 sample = bpf_ringbuf_reserve(&ringbuf, sizeof(*sample), 0); 50 if (!sample) { 51 __sync_fetch_and_add(&dropped, 1); 52 return 1; 53 } 54 55 sample->pid = pid; 56 bpf_get_current_comm(sample->comm, sizeof(sample->comm)); 57 sample->value = value; 58 59 sample->seq = seq++; 60 __sync_fetch_and_add(&total, 1); 61 62 if (sample->seq & 1) { 63 /* copy from reserved sample to a new one... */ 64 bpf_ringbuf_output(&ringbuf, sample, sizeof(*sample), flags); 65 /* ...and then discard reserved sample */ 66 bpf_ringbuf_discard(sample, flags); 67 __sync_fetch_and_add(&discarded, 1); 68 } else { 69 bpf_ringbuf_submit(sample, flags); 70 } 71 72 avail_data = bpf_ringbuf_query(&ringbuf, BPF_RB_AVAIL_DATA); 73 ring_size = bpf_ringbuf_query(&ringbuf, BPF_RB_RING_SIZE); 74 cons_pos = bpf_ringbuf_query(&ringbuf, BPF_RB_CONS_POS); 75 prod_pos = bpf_ringbuf_query(&ringbuf, BPF_RB_PROD_POS); 76 77 return 0; 78 } 79