samples/bpf/test_current_task_under_cgroup.bpf.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 "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;