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_RISCV
20#include <asm/asm.h>
21
22asm (
23"       .pushsection    .text, \"ax\", @progbits\n"
24"       .type           my_tramp, @function\n"
25"       .globl          my_tramp\n"
26"   my_tramp:\n"
27"       addi	sp,sp,-3*"SZREG"\n"
28"       "REG_S"	a0,0*"SZREG"(sp)\n"
29"       "REG_S"	t0,1*"SZREG"(sp)\n"
30"       "REG_S"	ra,2*"SZREG"(sp)\n"
31"       call	my_direct_func\n"
32"       "REG_L"	a0,0*"SZREG"(sp)\n"
33"       "REG_L"	t0,1*"SZREG"(sp)\n"
34"       "REG_L"	ra,2*"SZREG"(sp)\n"
35"       addi	sp,sp,3*"SZREG"\n"
36"       jr	t0\n"
37"       .size           my_tramp, .-my_tramp\n"
38"       .popsection\n"
39);
40
41#endif /* CONFIG_RISCV */
42
43#ifdef CONFIG_X86_64
44
45#include <asm/ibt.h>
46#include <asm/nospec-branch.h>
47
48asm (
49"	.pushsection    .text, \"ax\", @progbits\n"
50"	.type		my_tramp, @function\n"
51"	.globl		my_tramp\n"
52"   my_tramp:"
53	ASM_ENDBR
54"	pushq %rbp\n"
55"	movq %rsp, %rbp\n"
56	CALL_DEPTH_ACCOUNT
57"	pushq %rdi\n"
58"	call my_direct_func\n"
59"	popq %rdi\n"
60"	leave\n"
61	ASM_RET
62"	.size		my_tramp, .-my_tramp\n"
63"	.popsection\n"
64);
65
66#endif /* CONFIG_X86_64 */
67
68#ifdef CONFIG_S390
69
70asm (
71"	.pushsection	.text, \"ax\", @progbits\n"
72"	.type		my_tramp, @function\n"
73"	.globl		my_tramp\n"
74"   my_tramp:"
75"	lgr		%r1,%r15\n"
76"	stmg		%r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
77"	stg		%r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
78"	aghi		%r15,"__stringify(-STACK_FRAME_OVERHEAD)"\n"
79"	stg		%r1,"__stringify(__SF_BACKCHAIN)"(%r15)\n"
80"	brasl		%r14,my_direct_func\n"
81"	aghi		%r15,"__stringify(STACK_FRAME_OVERHEAD)"\n"
82"	lmg		%r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
83"	lg		%r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
84"	lgr		%r1,%r0\n"
85"	br		%r1\n"
86"	.size		my_tramp, .-my_tramp\n"
87"	.popsection\n"
88);
89
90#endif /* CONFIG_S390 */
91
92#ifdef CONFIG_ARM64
93
94asm (
95"	.pushsection	.text, \"ax\", @progbits\n"
96"	.type		my_tramp, @function\n"
97"	.globl		my_tramp\n"
98"   my_tramp:"
99"	hint	34\n" // bti	c
100"	sub	sp, sp, #32\n"
101"	stp	x9, x30, [sp]\n"
102"	str	x0, [sp, #16]\n"
103"	bl	my_direct_func\n"
104"	ldp	x30, x9, [sp]\n"
105"	ldr	x0, [sp, #16]\n"
106"	add	sp, sp, #32\n"
107"	ret	x9\n"
108"	.size		my_tramp, .-my_tramp\n"
109"	.popsection\n"
110);
111
112#endif /* CONFIG_ARM64 */
113
114#ifdef CONFIG_LOONGARCH
115
116asm (
117"	.pushsection	.text, \"ax\", @progbits\n"
118"	.type		my_tramp, @function\n"
119"	.globl		my_tramp\n"
120"   my_tramp:\n"
121"	addi.d	$sp, $sp, -32\n"
122"	st.d	$a0, $sp, 0\n"
123"	st.d	$t0, $sp, 8\n"
124"	st.d	$ra, $sp, 16\n"
125"	bl	my_direct_func\n"
126"	ld.d	$a0, $sp, 0\n"
127"	ld.d	$t0, $sp, 8\n"
128"	ld.d	$ra, $sp, 16\n"
129"	addi.d	$sp, $sp, 32\n"
130"	jr	$t0\n"
131"	.size		my_tramp, .-my_tramp\n"
132"	.popsection\n"
133);
134
135#endif /* CONFIG_LOONGARCH */
136
137static struct ftrace_ops direct;
138
139static int __init ftrace_direct_init(void)
140{
141	ftrace_set_filter_ip(&direct, (unsigned long) wake_up_process, 0, 0);
142
143	return register_ftrace_direct(&direct, (unsigned long) my_tramp);
144}
145
146static void __exit ftrace_direct_exit(void)
147{
148	unregister_ftrace_direct(&direct, (unsigned long)my_tramp, true);
149}
150
151module_init(ftrace_direct_init);
152module_exit(ftrace_direct_exit);
153
154MODULE_AUTHOR("Steven Rostedt");
155MODULE_DESCRIPTION("Example use case of using register_ftrace_direct()");
156MODULE_LICENSE("GPL");
157