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
my_direct_func(struct vm_area_struct * vma,unsigned long address,unsigned int flags)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 ASM_RET
35 " .size my_tramp, .-my_tramp\n"
36 " .popsection\n"
37 );
38
39
ftrace_direct_init(void)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
ftrace_direct_exit(void)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");
58