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_RISCV
26#include <asm/asm.h>
27
28asm (
29"	.pushsection    .text, \"ax\", @progbits\n"
30"	.type		my_tramp1, @function\n"
31"	.globl		my_tramp1\n"
32"   my_tramp1:\n"
33"       addi	sp,sp,-3*"SZREG"\n"
34"       "REG_S"	a0,0*"SZREG"(sp)\n"
35"       "REG_S"	t0,1*"SZREG"(sp)\n"
36"       "REG_S"	ra,2*"SZREG"(sp)\n"
37"       mv	a0,t0\n"
38"       call	my_direct_func1\n"
39"       "REG_L"	a0,0*"SZREG"(sp)\n"
40"       "REG_L"	t0,1*"SZREG"(sp)\n"
41"       "REG_L"	ra,2*"SZREG"(sp)\n"
42"       addi	sp,sp,3*"SZREG"\n"
43"	jr	t0\n"
44"	.size		my_tramp1, .-my_tramp1\n"
45
46"	.type		my_tramp2, @function\n"
47"	.globl		my_tramp2\n"
48"   my_tramp2:\n"
49"       addi	sp,sp,-3*"SZREG"\n"
50"       "REG_S"	a0,0*"SZREG"(sp)\n"
51"       "REG_S"	t0,1*"SZREG"(sp)\n"
52"       "REG_S"	ra,2*"SZREG"(sp)\n"
53"       mv	a0,t0\n"
54"       call	my_direct_func2\n"
55"       "REG_L"	a0,0*"SZREG"(sp)\n"
56"       "REG_L"	t0,1*"SZREG"(sp)\n"
57"       "REG_L"	ra,2*"SZREG"(sp)\n"
58"       addi	sp,sp,3*"SZREG"\n"
59"	jr	t0\n"
60"	.size		my_tramp2, .-my_tramp2\n"
61"	.popsection\n"
62);
63
64#endif /* CONFIG_RISCV */
65
66#ifdef CONFIG_X86_64
67
68#include <asm/ibt.h>
69#include <asm/nospec-branch.h>
70
71asm (
72"	.pushsection    .text, \"ax\", @progbits\n"
73"	.type		my_tramp1, @function\n"
74"	.globl		my_tramp1\n"
75"   my_tramp1:"
76	ASM_ENDBR
77"	pushq %rbp\n"
78"	movq %rsp, %rbp\n"
79	CALL_DEPTH_ACCOUNT
80"	pushq %rdi\n"
81"	movq 8(%rbp), %rdi\n"
82"	call my_direct_func1\n"
83"	popq %rdi\n"
84"	leave\n"
85	ASM_RET
86"	.size		my_tramp1, .-my_tramp1\n"
87
88"	.type		my_tramp2, @function\n"
89"	.globl		my_tramp2\n"
90"   my_tramp2:"
91	ASM_ENDBR
92"	pushq %rbp\n"
93"	movq %rsp, %rbp\n"
94	CALL_DEPTH_ACCOUNT
95"	pushq %rdi\n"
96"	movq 8(%rbp), %rdi\n"
97"	call my_direct_func2\n"
98"	popq %rdi\n"
99"	leave\n"
100	ASM_RET
101"	.size		my_tramp2, .-my_tramp2\n"
102"	.popsection\n"
103);
104
105#endif /* CONFIG_X86_64 */
106
107#ifdef CONFIG_S390
108
109asm (
110"       .pushsection    .text, \"ax\", @progbits\n"
111"       .type           my_tramp1, @function\n"
112"       .globl          my_tramp1\n"
113"   my_tramp1:"
114"       lgr             %r1,%r15\n"
115"       stmg            %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
116"       stg             %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
117"       aghi            %r15,"__stringify(-STACK_FRAME_OVERHEAD)"\n"
118"       stg             %r1,"__stringify(__SF_BACKCHAIN)"(%r15)\n"
119"       lgr             %r2,%r0\n"
120"       brasl           %r14,my_direct_func1\n"
121"       aghi            %r15,"__stringify(STACK_FRAME_OVERHEAD)"\n"
122"       lmg             %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
123"       lg              %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
124"       lgr             %r1,%r0\n"
125"       br              %r1\n"
126"       .size           my_tramp1, .-my_tramp1\n"
127"\n"
128"       .type           my_tramp2, @function\n"
129"       .globl          my_tramp2\n"
130"   my_tramp2:"
131"       lgr             %r1,%r15\n"
132"       stmg            %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
133"       stg             %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
134"       aghi            %r15,"__stringify(-STACK_FRAME_OVERHEAD)"\n"
135"       stg             %r1,"__stringify(__SF_BACKCHAIN)"(%r15)\n"
136"       lgr             %r2,%r0\n"
137"       brasl           %r14,my_direct_func2\n"
138"       aghi            %r15,"__stringify(STACK_FRAME_OVERHEAD)"\n"
139"       lmg             %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
140"       lg              %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
141"       lgr             %r1,%r0\n"
142"       br              %r1\n"
143"       .size           my_tramp2, .-my_tramp2\n"
144"       .popsection\n"
145);
146
147#endif /* CONFIG_S390 */
148
149#ifdef CONFIG_ARM64
150
151asm (
152"	.pushsection    .text, \"ax\", @progbits\n"
153"	.type		my_tramp1, @function\n"
154"	.globl		my_tramp1\n"
155"   my_tramp1:"
156"	hint	34\n" // bti	c
157"	sub	sp, sp, #32\n"
158"	stp	x9, x30, [sp]\n"
159"	str	x0, [sp, #16]\n"
160"	mov	x0, x30\n"
161"	bl	my_direct_func1\n"
162"	ldp	x30, x9, [sp]\n"
163"	ldr	x0, [sp, #16]\n"
164"	add	sp, sp, #32\n"
165"	ret	x9\n"
166"	.size		my_tramp1, .-my_tramp1\n"
167
168"	.type		my_tramp2, @function\n"
169"	.globl		my_tramp2\n"
170"   my_tramp2:"
171"	hint	34\n" // bti	c
172"	sub	sp, sp, #32\n"
173"	stp	x9, x30, [sp]\n"
174"	str	x0, [sp, #16]\n"
175"	mov	x0, x30\n"
176"	bl	my_direct_func2\n"
177"	ldp	x30, x9, [sp]\n"
178"	ldr	x0, [sp, #16]\n"
179"	add	sp, sp, #32\n"
180"	ret	x9\n"
181"	.size		my_tramp2, .-my_tramp2\n"
182"	.popsection\n"
183);
184
185#endif /* CONFIG_ARM64 */
186
187#ifdef CONFIG_LOONGARCH
188#include <asm/asm.h>
189
190asm (
191"	.pushsection    .text, \"ax\", @progbits\n"
192"	.type		my_tramp1, @function\n"
193"	.globl		my_tramp1\n"
194"   my_tramp1:\n"
195"	addi.d	$sp, $sp, -32\n"
196"	st.d	$a0, $sp, 0\n"
197"	st.d	$t0, $sp, 8\n"
198"	st.d	$ra, $sp, 16\n"
199"	move	$a0, $t0\n"
200"	bl	my_direct_func1\n"
201"	ld.d	$a0, $sp, 0\n"
202"	ld.d	$t0, $sp, 8\n"
203"	ld.d	$ra, $sp, 16\n"
204"	addi.d	$sp, $sp, 32\n"
205"	jr	$t0\n"
206"	.size		my_tramp1, .-my_tramp1\n"
207
208"	.type		my_tramp2, @function\n"
209"	.globl		my_tramp2\n"
210"   my_tramp2:\n"
211"	addi.d	$sp, $sp, -32\n"
212"	st.d	$a0, $sp, 0\n"
213"	st.d	$t0, $sp, 8\n"
214"	st.d	$ra, $sp, 16\n"
215"	move	$a0, $t0\n"
216"	bl	my_direct_func2\n"
217"	ld.d	$a0, $sp, 0\n"
218"	ld.d	$t0, $sp, 8\n"
219"	ld.d	$ra, $sp, 16\n"
220"	addi.d	$sp, $sp, 32\n"
221"	jr	$t0\n"
222"	.size		my_tramp2, .-my_tramp2\n"
223"	.popsection\n"
224);
225
226#endif /* CONFIG_LOONGARCH */
227
228static unsigned long my_tramp = (unsigned long)my_tramp1;
229static unsigned long tramps[2] = {
230	(unsigned long)my_tramp1,
231	(unsigned long)my_tramp2,
232};
233
234static struct ftrace_ops direct;
235
236static int simple_thread(void *arg)
237{
238	static int t;
239	int ret = 0;
240
241	while (!kthread_should_stop()) {
242		set_current_state(TASK_INTERRUPTIBLE);
243		schedule_timeout(2 * HZ);
244
245		if (ret)
246			continue;
247		t ^= 1;
248		ret = modify_ftrace_direct(&direct, tramps[t]);
249		if (!ret)
250			my_tramp = tramps[t];
251		WARN_ON_ONCE(ret);
252	}
253
254	return 0;
255}
256
257static struct task_struct *simple_tsk;
258
259static int __init ftrace_direct_multi_init(void)
260{
261	int ret;
262
263	ftrace_set_filter_ip(&direct, (unsigned long) wake_up_process, 0, 0);
264	ftrace_set_filter_ip(&direct, (unsigned long) schedule, 0, 0);
265
266	ret = register_ftrace_direct(&direct, my_tramp);
267
268	if (!ret)
269		simple_tsk = kthread_run(simple_thread, NULL, "event-sample-fn");
270	return ret;
271}
272
273static void __exit ftrace_direct_multi_exit(void)
274{
275	kthread_stop(simple_tsk);
276	unregister_ftrace_direct(&direct, my_tramp, true);
277}
278
279module_init(ftrace_direct_multi_init);
280module_exit(ftrace_direct_multi_exit);
281
282MODULE_AUTHOR("Jiri Olsa");
283MODULE_DESCRIPTION("Example use case of using modify_ftrace_direct()");
284MODULE_LICENSE("GPL");
285