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 <linux/ptrace.h>
9 #include <uapi/linux/bpf.h>
10 #include <linux/version.h>
11 #include <bpf/bpf_helpers.h>
12 #include <uapi/linux/utsname.h>
13 #include "trace_common.h"
14 
15 struct {
16 	__uint(type, BPF_MAP_TYPE_CGROUP_ARRAY);
17 	__uint(key_size, sizeof(u32));
18 	__uint(value_size, sizeof(u32));
19 	__uint(max_entries, 1);
20 } cgroup_map SEC(".maps");
21 
22 struct {
23 	__uint(type, BPF_MAP_TYPE_ARRAY);
24 	__type(key, u32);
25 	__type(value, u64);
26 	__uint(max_entries, 1);
27 } perf_map SEC(".maps");
28 
29 /* Writes the last PID that called sync to a map at index 0 */
SYSCALL(sys_sync)30 SEC("kprobe/" SYSCALL(sys_sync))
31 int bpf_prog1(struct pt_regs *ctx)
32 {
33 	u64 pid = bpf_get_current_pid_tgid();
34 	int idx = 0;
35 
36 	if (!bpf_current_task_under_cgroup(&cgroup_map, 0))
37 		return 0;
38 
39 	bpf_map_update_elem(&perf_map, &idx, &pid, BPF_ANY);
40 	return 0;
41 }
42 
43 char _license[] SEC("license") = "GPL";
44 u32 _version SEC("version") = LINUX_VERSION_CODE;
45