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 #include <asm/asm-offsets.h>
7
8 extern void my_direct_func(struct vm_area_struct *vma,
9 unsigned long address, unsigned int flags);
10
my_direct_func(struct vm_area_struct * vma,unsigned long address,unsigned int flags)11 void my_direct_func(struct vm_area_struct *vma,
12 unsigned long address, unsigned int flags)
13 {
14 trace_printk("handle mm fault vma=%p address=%lx flags=%x\n",
15 vma, address, flags);
16 }
17
18 extern void my_tramp(void *);
19
20 #ifdef CONFIG_X86_64
21
22 #include <asm/ibt.h>
23 #include <asm/nospec-branch.h>
24
25 asm (
26 " .pushsection .text, \"ax\", @progbits\n"
27 " .type my_tramp, @function\n"
28 " .globl my_tramp\n"
29 " my_tramp:"
30 ASM_ENDBR
31 " pushq %rbp\n"
32 " movq %rsp, %rbp\n"
33 CALL_DEPTH_ACCOUNT
34 " pushq %rdi\n"
35 " pushq %rsi\n"
36 " pushq %rdx\n"
37 " call my_direct_func\n"
38 " popq %rdx\n"
39 " popq %rsi\n"
40 " popq %rdi\n"
41 " leave\n"
42 ASM_RET
43 " .size my_tramp, .-my_tramp\n"
44 " .popsection\n"
45 );
46
47 #endif /* CONFIG_X86_64 */
48
49 #ifdef CONFIG_S390
50
51 asm (
52 " .pushsection .text, \"ax\", @progbits\n"
53 " .type my_tramp, @function\n"
54 " .globl my_tramp\n"
55 " my_tramp:"
56 " lgr %r1,%r15\n"
57 " stmg %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
58 " stg %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
59 " aghi %r15,"__stringify(-STACK_FRAME_OVERHEAD)"\n"
60 " stg %r1,"__stringify(__SF_BACKCHAIN)"(%r15)\n"
61 " brasl %r14,my_direct_func\n"
62 " aghi %r15,"__stringify(STACK_FRAME_OVERHEAD)"\n"
63 " lmg %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
64 " lg %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
65 " lgr %r1,%r0\n"
66 " br %r1\n"
67 " .size my_tramp, .-my_tramp\n"
68 " .popsection\n"
69 );
70
71 #endif /* CONFIG_S390 */
72
ftrace_direct_init(void)73 static int __init ftrace_direct_init(void)
74 {
75 return register_ftrace_direct((unsigned long)handle_mm_fault,
76 (unsigned long)my_tramp);
77 }
78
ftrace_direct_exit(void)79 static void __exit ftrace_direct_exit(void)
80 {
81 unregister_ftrace_direct((unsigned long)handle_mm_fault,
82 (unsigned long)my_tramp);
83 }
84
85 module_init(ftrace_direct_init);
86 module_exit(ftrace_direct_exit);
87
88 MODULE_AUTHOR("Steven Rostedt");
89 MODULE_DESCRIPTION("Another example use case of using register_ftrace_direct()");
90 MODULE_LICENSE("GPL");
91