1 /* Copyright (c) 2016 Sargun Dhillon <sargun@sargun.me>
2  *
3  * This program is free software; you can redistribute it and/or
4  * modify it under the terms of version 2 of the GNU General Public
5  * License as published by the Free Software Foundation.
6  */
7 
8 #include "vmlinux.h"
9 #include <linux/version.h>
10 #include <bpf/bpf_helpers.h>
11 #include <bpf/bpf_tracing.h>
12 #include <bpf/bpf_core_read.h>
13 
14 struct {
15 	__uint(type, BPF_MAP_TYPE_CGROUP_ARRAY);
16 	__uint(key_size, sizeof(u32));
17 	__uint(value_size, sizeof(u32));
18 	__uint(max_entries, 1);
19 } cgroup_map SEC(".maps");
20 
21 struct {
22 	__uint(type, BPF_MAP_TYPE_ARRAY);
23 	__type(key, u32);
24 	__type(value, u64);
25 	__uint(max_entries, 1);
26 } perf_map SEC(".maps");
27 
28 /* Writes the last PID that called sync to a map at index 0 */
29 SEC("ksyscall/sync")
30 int BPF_KSYSCALL(bpf_prog1)
31 {
32 	u64 pid = bpf_get_current_pid_tgid();
33 	int idx = 0;
34 
35 	if (!bpf_current_task_under_cgroup(&cgroup_map, 0))
36 		return 0;
37 
38 	bpf_map_update_elem(&perf_map, &idx, &pid, BPF_ANY);
39 	return 0;
40 }
41 
42 char _license[] SEC("license") = "GPL";
43 u32 _version SEC("version") = LINUX_VERSION_CODE;
44