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
14struct {
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
21struct {
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 */
29SEC("ksyscall/sync")
30int 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
42char _license[] SEC("license") = "GPL";
43u32 _version SEC("version") = LINUX_VERSION_CODE;
44