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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");
1// SPDX-License-Identifier: GPL-2.0-only
2#include <linux/module.h>
3#include <linux/kthread.h>
4#include <linux/ftrace.h>
5
6void my_direct_func1(void)
7{
8 trace_printk("my direct func1\n");
9}
10
11void my_direct_func2(void)
12{
13 trace_printk("my direct func2\n");
14}
15
16extern void my_tramp1(void *);
17extern void my_tramp2(void *);
18
19static unsigned long my_ip = (unsigned long)schedule;
20
21asm (
22" .pushsection .text, \"ax\", @progbits\n"
23" .type my_tramp1, @function\n"
24" .globl my_tramp1\n"
25" my_tramp1:"
26" pushq %rbp\n"
27" movq %rsp, %rbp\n"
28" call my_direct_func1\n"
29" leave\n"
30" .size my_tramp1, .-my_tramp1\n"
31" ret\n"
32" .type my_tramp2, @function\n"
33" .globl my_tramp2\n"
34" my_tramp2:"
35" pushq %rbp\n"
36" movq %rsp, %rbp\n"
37" call my_direct_func2\n"
38" leave\n"
39" ret\n"
40" .size my_tramp2, .-my_tramp2\n"
41" .popsection\n"
42);
43
44static unsigned long my_tramp = (unsigned long)my_tramp1;
45static unsigned long tramps[2] = {
46 (unsigned long)my_tramp1,
47 (unsigned long)my_tramp2,
48};
49
50static int simple_thread(void *arg)
51{
52 static int t;
53 int ret = 0;
54
55 while (!kthread_should_stop()) {
56 set_current_state(TASK_INTERRUPTIBLE);
57 schedule_timeout(2 * HZ);
58
59 if (ret)
60 continue;
61 t ^= 1;
62 ret = modify_ftrace_direct(my_ip, my_tramp, tramps[t]);
63 if (!ret)
64 my_tramp = tramps[t];
65 WARN_ON_ONCE(ret);
66 }
67
68 return 0;
69}
70
71static struct task_struct *simple_tsk;
72
73static int __init ftrace_direct_init(void)
74{
75 int ret;
76
77 ret = register_ftrace_direct(my_ip, my_tramp);
78 if (!ret)
79 simple_tsk = kthread_run(simple_thread, NULL, "event-sample-fn");
80 return ret;
81}
82
83static void __exit ftrace_direct_exit(void)
84{
85 kthread_stop(simple_tsk);
86 unregister_ftrace_direct(my_ip, my_tramp);
87}
88
89module_init(ftrace_direct_init);
90module_exit(ftrace_direct_exit);
91
92MODULE_AUTHOR("Steven Rostedt");
93MODULE_DESCRIPTION("Example use case of using modify_ftrace_direct()");
94MODULE_LICENSE("GPL");