samples/ftrace/ftrace-direct-too.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 #include <linux/module.h>
   3
   4 #include <linux/mm.h> /* for handle_mm_fault() */
   5 #include <linux/ftrace.h>
   6
   7 extern void my_direct_func(struct vm_area_struct *vma,
   8                            unsigned long address, unsigned int flags);
   9
  10 void my_direct_func(struct vm_area_struct *vma,
  11                         unsigned long address, unsigned int flags)
  12 {
  13         trace_printk("handle mm fault vma=%p address=%lx flags=%x\n",
  14                      vma, address, flags);
  15 }
  16
  17 extern void my_tramp(void *);
  18
  19 asm (
  20 "       .pushsection    .text, \"ax\", @progbits\n"
  21 "       .type           my_tramp, @function\n"
  22 "       .globl          my_tramp\n"
  23 "   my_tramp:"
  24 "       pushq %rbp\n"
  25 "       movq %rsp, %rbp\n"
  26 "       pushq %rdi\n"
  27 "       pushq %rsi\n"
  28 "       pushq %rdx\n"
  29 "       call my_direct_func\n"
  30 "       popq %rdx\n"
  31 "       popq %rsi\n"
  32 "       popq %rdi\n"
  33 "       leave\n"
  34 "       ret\n"
  35 "       .size           my_tramp, .-my_tramp\n"
  36 "       .popsection\n"
  37 );
  38
  39
  40 static int __init ftrace_direct_init(void)
  41 {
  42         return register_ftrace_direct((unsigned long)handle_mm_fault,
  43                                      (unsigned long)my_tramp);
  44 }
  45
  46 static void __exit ftrace_direct_exit(void)
  47 {
  48         unregister_ftrace_direct((unsigned long)handle_mm_fault,
  49                                  (unsigned long)my_tramp);
  50 }
  51
  52 module_init(ftrace_direct_init);
  53 module_exit(ftrace_direct_exit);
  54
  55 MODULE_AUTHOR("Steven Rostedt");
  56 MODULE_DESCRIPTION("Another example use case of using register_ftrace_direct()");
  57 MODULE_LICENSE("GPL");