/* Copyright (c) 2016 Sargun Dhillon <sargun@sargun.me>
   *
   * This program is free software; you can redistribute it and/or
   * modify it under the terms of version 2 of the GNU General Public
   * License as published by the Free Software Foundation.
   */
  
  #include <linux/ptrace.h>
  #include <uapi/linux/bpf.h>
  #include <linux/version.h>
  #include "bpf_helpers.h"
  #include <uapi/linux/utsname.h>
  
  struct bpf_map_def SEC("maps") cgroup_map = {
  	.type			= BPF_MAP_TYPE_CGROUP_ARRAY,
  	.key_size		= sizeof(u32),
  	.value_size		= sizeof(u32),
  	.max_entries	= 1,
  };
  
  struct bpf_map_def SEC("maps") perf_map = {
  	.type			= BPF_MAP_TYPE_ARRAY,
  	.key_size		= sizeof(u32),
  	.value_size		= sizeof(u64),
  	.max_entries	= 1,
  };
  
  /* Writes the last PID that called sync to a map at index 0 */
  SEC("kprobe/sys_sync")
  int bpf_prog1(struct pt_regs *ctx)
  {
  	u64 pid = bpf_get_current_pid_tgid();
  	int idx = 0;
  
  	if (!bpf_current_task_under_cgroup(&cgroup_map, 0))
  		return 0;
  
  	bpf_map_update_elem(&perf_map, &idx, &pid, BPF_ANY);
  	return 0;
  }
  
  char _license[] SEC("license") = "GPL";
  u32 _version SEC("version") = LINUX_VERSION_CODE;