1 // SPDX-License-Identifier: GPL-2.0-only
2 #include <linux/module.h>
3 
4 #include <linux/sched.h> /* for wake_up_process() */
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 task_struct *p);
11 
12 void my_direct_func(struct task_struct *p)
13 {
14 	trace_printk("waking up %s-%d\n", p->comm, p->pid);
15 }
16 
17 extern void my_tramp(void *);
18 
19 #ifdef CONFIG_X86_64
20 
21 #include <asm/ibt.h>
22 #include <asm/nospec-branch.h>
23 
24 asm (
25 "	.pushsection    .text, \"ax\", @progbits\n"
26 "	.type		my_tramp, @function\n"
27 "	.globl		my_tramp\n"
28 "   my_tramp:"
29 	ASM_ENDBR
30 "	pushq %rbp\n"
31 "	movq %rsp, %rbp\n"
32 	CALL_DEPTH_ACCOUNT
33 "	pushq %rdi\n"
34 "	call my_direct_func\n"
35 "	popq %rdi\n"
36 "	leave\n"
37 	ASM_RET
38 "	.size		my_tramp, .-my_tramp\n"
39 "	.popsection\n"
40 );
41 
42 #endif /* CONFIG_X86_64 */
43 
44 #ifdef CONFIG_S390
45 
46 asm (
47 "	.pushsection	.text, \"ax\", @progbits\n"
48 "	.type		my_tramp, @function\n"
49 "	.globl		my_tramp\n"
50 "   my_tramp:"
51 "	lgr		%r1,%r15\n"
52 "	stmg		%r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
53 "	stg		%r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
54 "	aghi		%r15,"__stringify(-STACK_FRAME_OVERHEAD)"\n"
55 "	stg		%r1,"__stringify(__SF_BACKCHAIN)"(%r15)\n"
56 "	brasl		%r14,my_direct_func\n"
57 "	aghi		%r15,"__stringify(STACK_FRAME_OVERHEAD)"\n"
58 "	lmg		%r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
59 "	lg		%r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
60 "	lgr		%r1,%r0\n"
61 "	br		%r1\n"
62 "	.size		my_tramp, .-my_tramp\n"
63 "	.popsection\n"
64 );
65 
66 #endif /* CONFIG_S390 */
67 
68 #ifdef CONFIG_ARM64
69 
70 asm (
71 "	.pushsection	.text, \"ax\", @progbits\n"
72 "	.type		my_tramp, @function\n"
73 "	.globl		my_tramp\n"
74 "   my_tramp:"
75 "	bti	c\n"
76 "	sub	sp, sp, #32\n"
77 "	stp	x9, x30, [sp]\n"
78 "	str	x0, [sp, #16]\n"
79 "	bl	my_direct_func\n"
80 "	ldp	x30, x9, [sp]\n"
81 "	ldr	x0, [sp, #16]\n"
82 "	add	sp, sp, #32\n"
83 "	ret	x9\n"
84 "	.size		my_tramp, .-my_tramp\n"
85 "	.popsection\n"
86 );
87 
88 #endif /* CONFIG_ARM64 */
89 
90 #ifdef CONFIG_LOONGARCH
91 
92 asm (
93 "	.pushsection	.text, \"ax\", @progbits\n"
94 "	.type		my_tramp, @function\n"
95 "	.globl		my_tramp\n"
96 "   my_tramp:\n"
97 "	addi.d	$sp, $sp, -32\n"
98 "	st.d	$a0, $sp, 0\n"
99 "	st.d	$t0, $sp, 8\n"
100 "	st.d	$ra, $sp, 16\n"
101 "	bl	my_direct_func\n"
102 "	ld.d	$a0, $sp, 0\n"
103 "	ld.d	$t0, $sp, 8\n"
104 "	ld.d	$ra, $sp, 16\n"
105 "	addi.d	$sp, $sp, 32\n"
106 "	jr	$t0\n"
107 "	.size		my_tramp, .-my_tramp\n"
108 "	.popsection\n"
109 );
110 
111 #endif /* CONFIG_LOONGARCH */
112 
113 static struct ftrace_ops direct;
114 
115 static int __init ftrace_direct_init(void)
116 {
117 	ftrace_set_filter_ip(&direct, (unsigned long) wake_up_process, 0, 0);
118 
119 	return register_ftrace_direct(&direct, (unsigned long) my_tramp);
120 }
121 
122 static void __exit ftrace_direct_exit(void)
123 {
124 	unregister_ftrace_direct(&direct, (unsigned long)my_tramp, true);
125 }
126 
127 module_init(ftrace_direct_init);
128 module_exit(ftrace_direct_exit);
129 
130 MODULE_AUTHOR("Steven Rostedt");
131 MODULE_DESCRIPTION("Example use case of using register_ftrace_direct()");
132 MODULE_LICENSE("GPL");
133