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(unsigned long ip);
10extern void my_direct_func2(unsigned long ip);
11
12void my_direct_func1(unsigned long ip)
13{
14	trace_printk("my direct func1 ip %lx\n", ip);
15}
16
17void my_direct_func2(unsigned long ip)
18{
19	trace_printk("my direct func2 ip %lx\n", ip);
20}
21
22extern void my_tramp1(void *);
23extern void my_tramp2(void *);
24
25#ifdef CONFIG_X86_64
26
27#include <asm/ibt.h>
28#include <asm/nospec-branch.h>
29
30asm (
31"	.pushsection    .text, \"ax\", @progbits\n"
32"	.type		my_tramp1, @function\n"
33"	.globl		my_tramp1\n"
34"   my_tramp1:"
35	ASM_ENDBR
36"	pushq %rbp\n"
37"	movq %rsp, %rbp\n"
38	CALL_DEPTH_ACCOUNT
39"	pushq %rdi\n"
40"	movq 8(%rbp), %rdi\n"
41"	call my_direct_func1\n"
42"	popq %rdi\n"
43"	leave\n"
44	ASM_RET
45"	.size		my_tramp1, .-my_tramp1\n"
46
47"	.type		my_tramp2, @function\n"
48"	.globl		my_tramp2\n"
49"   my_tramp2:"
50	ASM_ENDBR
51"	pushq %rbp\n"
52"	movq %rsp, %rbp\n"
53	CALL_DEPTH_ACCOUNT
54"	pushq %rdi\n"
55"	movq 8(%rbp), %rdi\n"
56"	call my_direct_func2\n"
57"	popq %rdi\n"
58"	leave\n"
59	ASM_RET
60"	.size		my_tramp2, .-my_tramp2\n"
61"	.popsection\n"
62);
63
64#endif /* CONFIG_X86_64 */
65
66#ifdef CONFIG_S390
67
68asm (
69"       .pushsection    .text, \"ax\", @progbits\n"
70"       .type           my_tramp1, @function\n"
71"       .globl          my_tramp1\n"
72"   my_tramp1:"
73"       lgr             %r1,%r15\n"
74"       stmg            %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
75"       stg             %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
76"       aghi            %r15,"__stringify(-STACK_FRAME_OVERHEAD)"\n"
77"       stg             %r1,"__stringify(__SF_BACKCHAIN)"(%r15)\n"
78"       lgr             %r2,%r0\n"
79"       brasl           %r14,my_direct_func1\n"
80"       aghi            %r15,"__stringify(STACK_FRAME_OVERHEAD)"\n"
81"       lmg             %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
82"       lg              %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
83"       lgr             %r1,%r0\n"
84"       br              %r1\n"
85"       .size           my_tramp1, .-my_tramp1\n"
86"\n"
87"       .type           my_tramp2, @function\n"
88"       .globl          my_tramp2\n"
89"   my_tramp2:"
90"       lgr             %r1,%r15\n"
91"       stmg            %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
92"       stg             %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
93"       aghi            %r15,"__stringify(-STACK_FRAME_OVERHEAD)"\n"
94"       stg             %r1,"__stringify(__SF_BACKCHAIN)"(%r15)\n"
95"       lgr             %r2,%r0\n"
96"       brasl           %r14,my_direct_func2\n"
97"       aghi            %r15,"__stringify(STACK_FRAME_OVERHEAD)"\n"
98"       lmg             %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
99"       lg              %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
100"       lgr             %r1,%r0\n"
101"       br              %r1\n"
102"       .size           my_tramp2, .-my_tramp2\n"
103"       .popsection\n"
104);
105
106#endif /* CONFIG_S390 */
107
108#ifdef CONFIG_ARM64
109
110asm (
111"	.pushsection    .text, \"ax\", @progbits\n"
112"	.type		my_tramp1, @function\n"
113"	.globl		my_tramp1\n"
114"   my_tramp1:"
115"	hint	34\n" // bti	c
116"	sub	sp, sp, #32\n"
117"	stp	x9, x30, [sp]\n"
118"	str	x0, [sp, #16]\n"
119"	mov	x0, x30\n"
120"	bl	my_direct_func1\n"
121"	ldp	x30, x9, [sp]\n"
122"	ldr	x0, [sp, #16]\n"
123"	add	sp, sp, #32\n"
124"	ret	x9\n"
125"	.size		my_tramp1, .-my_tramp1\n"
126
127"	.type		my_tramp2, @function\n"
128"	.globl		my_tramp2\n"
129"   my_tramp2:"
130"	hint	34\n" // bti	c
131"	sub	sp, sp, #32\n"
132"	stp	x9, x30, [sp]\n"
133"	str	x0, [sp, #16]\n"
134"	mov	x0, x30\n"
135"	bl	my_direct_func2\n"
136"	ldp	x30, x9, [sp]\n"
137"	ldr	x0, [sp, #16]\n"
138"	add	sp, sp, #32\n"
139"	ret	x9\n"
140"	.size		my_tramp2, .-my_tramp2\n"
141"	.popsection\n"
142);
143
144#endif /* CONFIG_ARM64 */
145
146#ifdef CONFIG_LOONGARCH
147#include <asm/asm.h>
148
149asm (
150"	.pushsection    .text, \"ax\", @progbits\n"
151"	.type		my_tramp1, @function\n"
152"	.globl		my_tramp1\n"
153"   my_tramp1:\n"
154"	addi.d	$sp, $sp, -32\n"
155"	st.d	$a0, $sp, 0\n"
156"	st.d	$t0, $sp, 8\n"
157"	st.d	$ra, $sp, 16\n"
158"	move	$a0, $t0\n"
159"	bl	my_direct_func1\n"
160"	ld.d	$a0, $sp, 0\n"
161"	ld.d	$t0, $sp, 8\n"
162"	ld.d	$ra, $sp, 16\n"
163"	addi.d	$sp, $sp, 32\n"
164"	jr	$t0\n"
165"	.size		my_tramp1, .-my_tramp1\n"
166
167"	.type		my_tramp2, @function\n"
168"	.globl		my_tramp2\n"
169"   my_tramp2:\n"
170"	addi.d	$sp, $sp, -32\n"
171"	st.d	$a0, $sp, 0\n"
172"	st.d	$t0, $sp, 8\n"
173"	st.d	$ra, $sp, 16\n"
174"	move	$a0, $t0\n"
175"	bl	my_direct_func2\n"
176"	ld.d	$a0, $sp, 0\n"
177"	ld.d	$t0, $sp, 8\n"
178"	ld.d	$ra, $sp, 16\n"
179"	addi.d	$sp, $sp, 32\n"
180"	jr	$t0\n"
181"	.size		my_tramp2, .-my_tramp2\n"
182"	.popsection\n"
183);
184
185#endif /* CONFIG_LOONGARCH */
186
187static unsigned long my_tramp = (unsigned long)my_tramp1;
188static unsigned long tramps[2] = {
189	(unsigned long)my_tramp1,
190	(unsigned long)my_tramp2,
191};
192
193static struct ftrace_ops direct;
194
195static int simple_thread(void *arg)
196{
197	static int t;
198	int ret = 0;
199
200	while (!kthread_should_stop()) {
201		set_current_state(TASK_INTERRUPTIBLE);
202		schedule_timeout(2 * HZ);
203
204		if (ret)
205			continue;
206		t ^= 1;
207		ret = modify_ftrace_direct(&direct, tramps[t]);
208		if (!ret)
209			my_tramp = tramps[t];
210		WARN_ON_ONCE(ret);
211	}
212
213	return 0;
214}
215
216static struct task_struct *simple_tsk;
217
218static int __init ftrace_direct_multi_init(void)
219{
220	int ret;
221
222	ftrace_set_filter_ip(&direct, (unsigned long) wake_up_process, 0, 0);
223	ftrace_set_filter_ip(&direct, (unsigned long) schedule, 0, 0);
224
225	ret = register_ftrace_direct(&direct, my_tramp);
226
227	if (!ret)
228		simple_tsk = kthread_run(simple_thread, NULL, "event-sample-fn");
229	return ret;
230}
231
232static void __exit ftrace_direct_multi_exit(void)
233{
234	kthread_stop(simple_tsk);
235	unregister_ftrace_direct(&direct, my_tramp, true);
236}
237
238module_init(ftrace_direct_multi_init);
239module_exit(ftrace_direct_multi_exit);
240
241MODULE_AUTHOR("Jiri Olsa");
242MODULE_DESCRIPTION("Example use case of using modify_ftrace_direct()");
243MODULE_LICENSE("GPL");
244