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, unsigned long address,
8 unsigned int flags, struct pt_regs *regs);
9
my_direct_func(struct vm_area_struct * vma,unsigned long address,unsigned int flags,struct pt_regs * regs)10 void my_direct_func(struct vm_area_struct *vma, unsigned long address,
11 unsigned int flags, struct pt_regs *regs)
12 {
13 trace_printk("handle mm fault vma=%p address=%lx flags=%x regs=%p\n",
14 vma, address, flags, regs);
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 " pushq %rcx\n"
30 " call my_direct_func\n"
31 " popq %rcx\n"
32 " popq %rdx\n"
33 " popq %rsi\n"
34 " popq %rdi\n"
35 " leave\n"
36 ASM_RET
37 " .size my_tramp, .-my_tramp\n"
38 " .popsection\n"
39 );
40
41
ftrace_direct_init(void)42 static int __init ftrace_direct_init(void)
43 {
44 return register_ftrace_direct((unsigned long)handle_mm_fault,
45 (unsigned long)my_tramp);
46 }
47
ftrace_direct_exit(void)48 static void __exit ftrace_direct_exit(void)
49 {
50 unregister_ftrace_direct((unsigned long)handle_mm_fault,
51 (unsigned long)my_tramp);
52 }
53
54 module_init(ftrace_direct_init);
55 module_exit(ftrace_direct_exit);
56
57 MODULE_AUTHOR("Steven Rostedt");
58 MODULE_DESCRIPTION("Another example use case of using register_ftrace_direct()");
59 MODULE_LICENSE("GPL");
60