samples/ftrace/ftrace-direct.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 #include <linux/module.h>
   3
   4 #include <linux/sched.h> /* for wake_up_process() */
   5 #include <linux/ftrace.h>
   6
   7 void my_direct_func(struct task_struct *p)
   8 {
   9         trace_printk("waking up %s-%d\n", p->comm, p->pid);
  10 }
  11
  12 extern void my_tramp(void *);
  13
  14 asm (
  15 "       .pushsection    .text, \"ax\", @progbits\n"
  16 "   my_tramp:"
  17 "       pushq %rbp\n"
  18 "       movq %rsp, %rbp\n"
  19 "       pushq %rdi\n"
  20 "       call my_direct_func\n"
  21 "       popq %rdi\n"
  22 "       leave\n"
  23 "       ret\n"
  24 "       .popsection\n"
  25 );
  26
  27
  28 static int __init ftrace_direct_init(void)
  29 {
  30         return register_ftrace_direct((unsigned long)wake_up_process,
  31                                      (unsigned long)my_tramp);
  32 }
  33
  34 static void __exit ftrace_direct_exit(void)
  35 {
  36         unregister_ftrace_direct((unsigned long)wake_up_process,
  37                                  (unsigned long)my_tramp);
  38 }
  39
  40 module_init(ftrace_direct_init);
  41 module_exit(ftrace_direct_exit);
  42
  43 MODULE_AUTHOR("Steven Rostedt");
  44 MODULE_DESCRIPTION("Example use case of using register_ftrace_direct()");
  45 MODULE_LICENSE("GPL");