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#ifndef CONFIG_ARM64
7#include <asm/asm-offsets.h>
8#endif
9
10extern void my_direct_func(struct vm_area_struct *vma, unsigned long address,
11			   unsigned int flags, struct pt_regs *regs);
12
13void my_direct_func(struct vm_area_struct *vma, unsigned long address,
14		    unsigned int flags, struct pt_regs *regs)
15{
16	trace_printk("handle mm fault vma=%p address=%lx flags=%x regs=%p\n",
17		     vma, address, flags, regs);
18}
19
20extern void my_tramp(void *);
21
22#ifdef CONFIG_X86_64
23
24#include <asm/ibt.h>
25#include <asm/nospec-branch.h>
26
27asm (
28"	.pushsection    .text, \"ax\", @progbits\n"
29"	.type		my_tramp, @function\n"
30"	.globl		my_tramp\n"
31"   my_tramp:"
32	ASM_ENDBR
33"	pushq %rbp\n"
34"	movq %rsp, %rbp\n"
35	CALL_DEPTH_ACCOUNT
36"	pushq %rdi\n"
37"	pushq %rsi\n"
38"	pushq %rdx\n"
39"	pushq %rcx\n"
40"	call my_direct_func\n"
41"	popq %rcx\n"
42"	popq %rdx\n"
43"	popq %rsi\n"
44"	popq %rdi\n"
45"	leave\n"
46	ASM_RET
47"	.size		my_tramp, .-my_tramp\n"
48"	.popsection\n"
49);
50
51#endif /* CONFIG_X86_64 */
52
53#ifdef CONFIG_S390
54
55asm (
56"	.pushsection	.text, \"ax\", @progbits\n"
57"	.type		my_tramp, @function\n"
58"	.globl		my_tramp\n"
59"   my_tramp:"
60"	lgr		%r1,%r15\n"
61"	stmg		%r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
62"	stg		%r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
63"	aghi		%r15,"__stringify(-STACK_FRAME_OVERHEAD)"\n"
64"	stg		%r1,"__stringify(__SF_BACKCHAIN)"(%r15)\n"
65"	brasl		%r14,my_direct_func\n"
66"	aghi		%r15,"__stringify(STACK_FRAME_OVERHEAD)"\n"
67"	lmg		%r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
68"	lg		%r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
69"	lgr		%r1,%r0\n"
70"	br		%r1\n"
71"	.size		my_tramp, .-my_tramp\n"
72"	.popsection\n"
73);
74
75#endif /* CONFIG_S390 */
76
77#ifdef CONFIG_ARM64
78
79asm (
80"	.pushsection	.text, \"ax\", @progbits\n"
81"	.type		my_tramp, @function\n"
82"	.globl		my_tramp\n"
83"   my_tramp:"
84"	hint	34\n" // bti	c
85"	sub	sp, sp, #48\n"
86"	stp	x9, x30, [sp]\n"
87"	stp	x0, x1, [sp, #16]\n"
88"	stp	x2, x3, [sp, #32]\n"
89"	bl	my_direct_func\n"
90"	ldp	x30, x9, [sp]\n"
91"	ldp	x0, x1, [sp, #16]\n"
92"	ldp	x2, x3, [sp, #32]\n"
93"	add	sp, sp, #48\n"
94"	ret	x9\n"
95"	.size		my_tramp, .-my_tramp\n"
96"	.popsection\n"
97);
98
99#endif /* CONFIG_ARM64 */
100
101#ifdef CONFIG_LOONGARCH
102
103asm (
104"	.pushsection	.text, \"ax\", @progbits\n"
105"	.type		my_tramp, @function\n"
106"	.globl		my_tramp\n"
107"   my_tramp:\n"
108"	addi.d	$sp, $sp, -48\n"
109"	st.d	$a0, $sp, 0\n"
110"	st.d	$a1, $sp, 8\n"
111"	st.d	$a2, $sp, 16\n"
112"	st.d	$t0, $sp, 24\n"
113"	st.d	$ra, $sp, 32\n"
114"	bl	my_direct_func\n"
115"	ld.d	$a0, $sp, 0\n"
116"	ld.d	$a1, $sp, 8\n"
117"	ld.d	$a2, $sp, 16\n"
118"	ld.d	$t0, $sp, 24\n"
119"	ld.d	$ra, $sp, 32\n"
120"	addi.d	$sp, $sp, 48\n"
121"	jr	$t0\n"
122"	.size		my_tramp, .-my_tramp\n"
123"	.popsection\n"
124);
125
126#endif /* CONFIG_LOONGARCH */
127
128static struct ftrace_ops direct;
129
130static int __init ftrace_direct_init(void)
131{
132	ftrace_set_filter_ip(&direct, (unsigned long) handle_mm_fault, 0, 0);
133
134	return register_ftrace_direct(&direct, (unsigned long) my_tramp);
135}
136
137static void __exit ftrace_direct_exit(void)
138{
139	unregister_ftrace_direct(&direct, (unsigned long)my_tramp, true);
140}
141
142module_init(ftrace_direct_init);
143module_exit(ftrace_direct_exit);
144
145MODULE_AUTHOR("Steven Rostedt");
146MODULE_DESCRIPTION("Another example use case of using register_ftrace_direct()");
147MODULE_LICENSE("GPL");
148