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 
10 extern void my_direct_func(struct vm_area_struct *vma, unsigned long address,
11 			   unsigned int flags, struct pt_regs *regs);
12 
13 void 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 
20 extern void my_tramp(void *);
21 
22 #ifdef CONFIG_X86_64
23 
24 #include <asm/ibt.h>
25 #include <asm/nospec-branch.h>
26 
27 asm (
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 
55 asm (
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 
79 asm (
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 
103 asm (
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 
128 static struct ftrace_ops direct;
129 
130 static 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 
137 static void __exit ftrace_direct_exit(void)
138 {
139 	unregister_ftrace_direct(&direct, (unsigned long)my_tramp, true);
140 }
141 
142 module_init(ftrace_direct_init);
143 module_exit(ftrace_direct_exit);
144 
145 MODULE_AUTHOR("Steven Rostedt");
146 MODULE_DESCRIPTION("Another example use case of using register_ftrace_direct()");
147 MODULE_LICENSE("GPL");
148