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
10extern void my_direct_func(struct task_struct *p);
11
12void my_direct_func(struct task_struct *p)
13{
14	trace_printk("waking up %s-%d\n", p->comm, p->pid);
15}
16
17extern void my_tramp(void *);
18
19#ifdef CONFIG_X86_64
20
21#include <asm/ibt.h>
22#include <asm/nospec-branch.h>
23
24asm (
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
46asm (
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
70asm (
71"	.pushsection	.text, \"ax\", @progbits\n"
72"	.type		my_tramp, @function\n"
73"	.globl		my_tramp\n"
74"   my_tramp:"
75"	hint	34\n" // bti	c
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
92asm (
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
113static struct ftrace_ops direct;
114
115static 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
122static void __exit ftrace_direct_exit(void)
123{
124	unregister_ftrace_direct(&direct, (unsigned long)my_tramp, true);
125}
126
127module_init(ftrace_direct_init);
128module_exit(ftrace_direct_exit);
129
130MODULE_AUTHOR("Steven Rostedt");
131MODULE_DESCRIPTION("Example use case of using register_ftrace_direct()");
132MODULE_LICENSE("GPL");
133