1// SPDX-License-Identifier: GPL-2.0-only
2#include <linux/module.h>
3#include <linux/kthread.h>
4#include <linux/ftrace.h>
5#ifndef CONFIG_ARM64
6#include <asm/asm-offsets.h>
7#endif
8
9extern void my_direct_func1(void);
10extern void my_direct_func2(void);
11
12void my_direct_func1(void)
13{
14	trace_printk("my direct func1\n");
15}
16
17void my_direct_func2(void)
18{
19	trace_printk("my direct func2\n");
20}
21
22extern void my_tramp1(void *);
23extern void my_tramp2(void *);
24
25static unsigned long my_ip = (unsigned long)schedule;
26
27#ifdef CONFIG_RISCV
28#include <asm/asm.h>
29
30asm (
31"	.pushsection    .text, \"ax\", @progbits\n"
32"	.type		my_tramp1, @function\n"
33"	.globl		my_tramp1\n"
34"   my_tramp1:\n"
35"	addi	sp,sp,-2*"SZREG"\n"
36"	"REG_S"	t0,0*"SZREG"(sp)\n"
37"	"REG_S"	ra,1*"SZREG"(sp)\n"
38"	call	my_direct_func1\n"
39"	"REG_L"	t0,0*"SZREG"(sp)\n"
40"	"REG_L"	ra,1*"SZREG"(sp)\n"
41"	addi	sp,sp,2*"SZREG"\n"
42"	jr	t0\n"
43"	.size		my_tramp1, .-my_tramp1\n"
44"	.type		my_tramp2, @function\n"
45"	.globl		my_tramp2\n"
46
47"   my_tramp2:\n"
48"	addi	sp,sp,-2*"SZREG"\n"
49"	"REG_S"	t0,0*"SZREG"(sp)\n"
50"	"REG_S"	ra,1*"SZREG"(sp)\n"
51"	call	my_direct_func2\n"
52"	"REG_L"	t0,0*"SZREG"(sp)\n"
53"	"REG_L"	ra,1*"SZREG"(sp)\n"
54"	addi	sp,sp,2*"SZREG"\n"
55"	jr	t0\n"
56"	.size		my_tramp2, .-my_tramp2\n"
57"	.popsection\n"
58);
59
60#endif /* CONFIG_RISCV */
61
62#ifdef CONFIG_X86_64
63
64#include <asm/ibt.h>
65#include <asm/nospec-branch.h>
66
67asm (
68"	.pushsection    .text, \"ax\", @progbits\n"
69"	.type		my_tramp1, @function\n"
70"	.globl		my_tramp1\n"
71"   my_tramp1:"
72	ASM_ENDBR
73"	pushq %rbp\n"
74"	movq %rsp, %rbp\n"
75	CALL_DEPTH_ACCOUNT
76"	call my_direct_func1\n"
77"	leave\n"
78"	.size		my_tramp1, .-my_tramp1\n"
79	ASM_RET
80
81"	.type		my_tramp2, @function\n"
82"	.globl		my_tramp2\n"
83"   my_tramp2:"
84	ASM_ENDBR
85"	pushq %rbp\n"
86"	movq %rsp, %rbp\n"
87	CALL_DEPTH_ACCOUNT
88"	call my_direct_func2\n"
89"	leave\n"
90	ASM_RET
91"	.size		my_tramp2, .-my_tramp2\n"
92"	.popsection\n"
93);
94
95#endif /* CONFIG_X86_64 */
96
97#ifdef CONFIG_S390
98
99asm (
100"	.pushsection	.text, \"ax\", @progbits\n"
101"	.type		my_tramp1, @function\n"
102"	.globl		my_tramp1\n"
103"   my_tramp1:"
104"	lgr		%r1,%r15\n"
105"	stmg		%r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
106"	stg		%r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
107"	aghi		%r15,"__stringify(-STACK_FRAME_OVERHEAD)"\n"
108"	stg		%r1,"__stringify(__SF_BACKCHAIN)"(%r15)\n"
109"	brasl		%r14,my_direct_func1\n"
110"	aghi		%r15,"__stringify(STACK_FRAME_OVERHEAD)"\n"
111"	lmg		%r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
112"	lg		%r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
113"	lgr		%r1,%r0\n"
114"	br		%r1\n"
115"	.size		my_tramp1, .-my_tramp1\n"
116"	.type		my_tramp2, @function\n"
117"	.globl		my_tramp2\n"
118"   my_tramp2:"
119"	lgr		%r1,%r15\n"
120"	stmg		%r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
121"	stg		%r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
122"	aghi		%r15,"__stringify(-STACK_FRAME_OVERHEAD)"\n"
123"	stg		%r1,"__stringify(__SF_BACKCHAIN)"(%r15)\n"
124"	brasl		%r14,my_direct_func2\n"
125"	aghi		%r15,"__stringify(STACK_FRAME_OVERHEAD)"\n"
126"	lmg		%r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
127"	lg		%r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
128"	lgr		%r1,%r0\n"
129"	br		%r1\n"
130"	.size		my_tramp2, .-my_tramp2\n"
131"	.popsection\n"
132);
133
134#endif /* CONFIG_S390 */
135
136#ifdef CONFIG_ARM64
137
138asm (
139"	.pushsection    .text, \"ax\", @progbits\n"
140"	.type		my_tramp1, @function\n"
141"	.globl		my_tramp1\n"
142"   my_tramp1:"
143"	hint	34\n" // bti	c
144"	sub	sp, sp, #16\n"
145"	stp	x9, x30, [sp]\n"
146"	bl	my_direct_func1\n"
147"	ldp	x30, x9, [sp]\n"
148"	add	sp, sp, #16\n"
149"	ret	x9\n"
150"	.size		my_tramp1, .-my_tramp1\n"
151
152"	.type		my_tramp2, @function\n"
153"	.globl		my_tramp2\n"
154"   my_tramp2:"
155"	hint	34\n" // bti	c
156"	sub	sp, sp, #16\n"
157"	stp	x9, x30, [sp]\n"
158"	bl	my_direct_func2\n"
159"	ldp	x30, x9, [sp]\n"
160"	add	sp, sp, #16\n"
161"	ret	x9\n"
162"	.size		my_tramp2, .-my_tramp2\n"
163"	.popsection\n"
164);
165
166#endif /* CONFIG_ARM64 */
167
168#ifdef CONFIG_LOONGARCH
169
170asm (
171"	.pushsection    .text, \"ax\", @progbits\n"
172"	.type		my_tramp1, @function\n"
173"	.globl		my_tramp1\n"
174"   my_tramp1:\n"
175"	addi.d	$sp, $sp, -16\n"
176"	st.d	$t0, $sp, 0\n"
177"	st.d	$ra, $sp, 8\n"
178"	bl	my_direct_func1\n"
179"	ld.d	$t0, $sp, 0\n"
180"	ld.d	$ra, $sp, 8\n"
181"	addi.d	$sp, $sp, 16\n"
182"	jr	$t0\n"
183"	.size		my_tramp1, .-my_tramp1\n"
184
185"	.type		my_tramp2, @function\n"
186"	.globl		my_tramp2\n"
187"   my_tramp2:\n"
188"	addi.d	$sp, $sp, -16\n"
189"	st.d	$t0, $sp, 0\n"
190"	st.d	$ra, $sp, 8\n"
191"	bl	my_direct_func2\n"
192"	ld.d	$t0, $sp, 0\n"
193"	ld.d	$ra, $sp, 8\n"
194"	addi.d	$sp, $sp, 16\n"
195"	jr	$t0\n"
196"	.size		my_tramp2, .-my_tramp2\n"
197"	.popsection\n"
198);
199
200#endif /* CONFIG_LOONGARCH */
201
202static struct ftrace_ops direct;
203
204static unsigned long my_tramp = (unsigned long)my_tramp1;
205static unsigned long tramps[2] = {
206	(unsigned long)my_tramp1,
207	(unsigned long)my_tramp2,
208};
209
210static int simple_thread(void *arg)
211{
212	static int t;
213	int ret = 0;
214
215	while (!kthread_should_stop()) {
216		set_current_state(TASK_INTERRUPTIBLE);
217		schedule_timeout(2 * HZ);
218
219		if (ret)
220			continue;
221		t ^= 1;
222		ret = modify_ftrace_direct(&direct, tramps[t]);
223		if (!ret)
224			my_tramp = tramps[t];
225		WARN_ON_ONCE(ret);
226	}
227
228	return 0;
229}
230
231static struct task_struct *simple_tsk;
232
233static int __init ftrace_direct_init(void)
234{
235	int ret;
236
237	ftrace_set_filter_ip(&direct, (unsigned long) my_ip, 0, 0);
238	ret = register_ftrace_direct(&direct, my_tramp);
239
240	if (!ret)
241		simple_tsk = kthread_run(simple_thread, NULL, "event-sample-fn");
242	return ret;
243}
244
245static void __exit ftrace_direct_exit(void)
246{
247	kthread_stop(simple_tsk);
248	unregister_ftrace_direct(&direct, my_tramp, true);
249}
250
251module_init(ftrace_direct_init);
252module_exit(ftrace_direct_exit);
253
254MODULE_AUTHOR("Steven Rostedt");
255MODULE_DESCRIPTION("Example use case of using modify_ftrace_direct()");
256MODULE_LICENSE("GPL");
257