samples/bpf/test_overhead_kprobe_kern.c

   1 /* Copyright (c) 2016 Facebook
   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 #include <linux/version.h>
   8 #include <linux/ptrace.h>
   9 #include <linux/sched.h>
  10 #include <uapi/linux/bpf.h>
  11 #include <bpf/bpf_helpers.h>
  12 #include <bpf/bpf_tracing.h>
  13
  14 #define _(P)                                                                   \
  15         ({                                                                     \
  16                 typeof(P) val = 0;                                             \
  17                 bpf_probe_read_kernel(&val, sizeof(val), &(P));                \
  18                 val;                                                           \
  19         })
  20
  21 SEC("kprobe/__set_task_comm")
  22 int prog(struct pt_regs *ctx)
  23 {
  24         struct signal_struct *signal;
  25         struct task_struct *tsk;
  26         char oldcomm[TASK_COMM_LEN] = {};
  27         char newcomm[TASK_COMM_LEN] = {};
  28         u16 oom_score_adj;
  29         u32 pid;
  30
  31         tsk = (void *)PT_REGS_PARM1(ctx);
  32
  33         pid = _(tsk->pid);
  34         bpf_probe_read_kernel_str(oldcomm, sizeof(oldcomm), &tsk->comm);
  35         bpf_probe_read_kernel_str(newcomm, sizeof(newcomm),
  36                                   (void *)PT_REGS_PARM2(ctx));
  37         signal = _(tsk->signal);
  38         oom_score_adj = _(signal->oom_score_adj);
  39         return 0;
  40 }
  41
  42 SEC("kprobe/urandom_read")
  43 int prog2(struct pt_regs *ctx)
  44 {
  45         return 0;
  46 }
  47
  48 char _license[] SEC("license") = "GPL";
  49 u32 _version SEC("version") = LINUX_VERSION_CODE;