samples/bpf/test_current_task_under_cgroup_kern.c

   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 */
  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;