1// SPDX-License-Identifier: GPL-2.0-only
2#include <linux/module.h>
3#include <linux/kthread.h>
4#include <linux/ftrace.h>
5#if !defined(CONFIG_ARM64) && !defined(CONFIG_PPC32)
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 ASM_RET
79" .size my_tramp1, .-my_tramp1\n"
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 $ra, $sp, 0\n"
180" ld.d $t0, $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 $ra, $sp, 0\n"
193" ld.d $t0, $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
202#ifdef CONFIG_PPC
203#include <asm/ppc_asm.h>
204
205#ifdef CONFIG_PPC64
206#define STACK_FRAME_SIZE 48
207#else
208#define STACK_FRAME_SIZE 24
209#endif
210
211#if defined(CONFIG_PPC64_ELF_ABI_V2) && !defined(CONFIG_PPC_KERNEL_PCREL)
212#define PPC64_TOC_SAVE_AND_UPDATE \
213" std 2, 24(1)\n" \
214" bcl 20, 31, 1f\n" \
215" 1: mflr 12\n" \
216" ld 2, (99f - 1b)(12)\n"
217#define PPC64_TOC_RESTORE \
218" ld 2, 24(1)\n"
219#define PPC64_TOC \
220" 99: .quad .TOC.@tocbase\n"
221#else
222#define PPC64_TOC_SAVE_AND_UPDATE ""
223#define PPC64_TOC_RESTORE ""
224#define PPC64_TOC ""
225#endif
226
227#ifdef CONFIG_PPC_FTRACE_OUT_OF_LINE
228#define PPC_FTRACE_RESTORE_LR \
229 PPC_LL" 0, "__stringify(PPC_LR_STKOFF)"(1)\n" \
230" mtlr 0\n"
231#define PPC_FTRACE_RET \
232" blr\n"
233#else
234#define PPC_FTRACE_RESTORE_LR \
235 PPC_LL" 0, "__stringify(PPC_LR_STKOFF)"(1)\n" \
236" mtctr 0\n"
237#define PPC_FTRACE_RET \
238" mtlr 0\n" \
239" bctr\n"
240#endif
241
242asm (
243" .pushsection .text, \"ax\", @progbits\n"
244" .type my_tramp1, @function\n"
245" .globl my_tramp1\n"
246" my_tramp1:\n"
247 PPC_STL" 0, "__stringify(PPC_LR_STKOFF)"(1)\n"
248 PPC_STLU" 1, -"__stringify(STACK_FRAME_MIN_SIZE)"(1)\n"
249" mflr 0\n"
250 PPC_STL" 0, "__stringify(PPC_LR_STKOFF)"(1)\n"
251 PPC_STLU" 1, -"__stringify(STACK_FRAME_SIZE)"(1)\n"
252 PPC64_TOC_SAVE_AND_UPDATE
253" bl my_direct_func1\n"
254 PPC64_TOC_RESTORE
255" addi 1, 1, "__stringify(STACK_FRAME_SIZE)"\n"
256 PPC_FTRACE_RESTORE_LR
257" addi 1, 1, "__stringify(STACK_FRAME_MIN_SIZE)"\n"
258 PPC_LL" 0, "__stringify(PPC_LR_STKOFF)"(1)\n"
259 PPC_FTRACE_RET
260" .size my_tramp1, .-my_tramp1\n"
261
262" .type my_tramp2, @function\n"
263" .globl my_tramp2\n"
264" my_tramp2:\n"
265 PPC_STL" 0, "__stringify(PPC_LR_STKOFF)"(1)\n"
266 PPC_STLU" 1, -"__stringify(STACK_FRAME_MIN_SIZE)"(1)\n"
267" mflr 0\n"
268 PPC_STL" 0, "__stringify(PPC_LR_STKOFF)"(1)\n"
269 PPC_STLU" 1, -"__stringify(STACK_FRAME_SIZE)"(1)\n"
270 PPC64_TOC_SAVE_AND_UPDATE
271" bl my_direct_func2\n"
272 PPC64_TOC_RESTORE
273" addi 1, 1, "__stringify(STACK_FRAME_SIZE)"\n"
274 PPC_FTRACE_RESTORE_LR
275" addi 1, 1, "__stringify(STACK_FRAME_MIN_SIZE)"\n"
276 PPC_LL" 0, "__stringify(PPC_LR_STKOFF)"(1)\n"
277 PPC_FTRACE_RET
278 PPC64_TOC
279" .size my_tramp2, .-my_tramp2\n"
280" .popsection\n"
281);
282
283#endif /* CONFIG_PPC */
284
285static struct ftrace_ops direct;
286
287static unsigned long my_tramp = (unsigned long)my_tramp1;
288static unsigned long tramps[2] = {
289 (unsigned long)my_tramp1,
290 (unsigned long)my_tramp2,
291};
292
293static int simple_thread(void *arg)
294{
295 static int t;
296 int ret = 0;
297
298 while (!kthread_should_stop()) {
299 set_current_state(TASK_INTERRUPTIBLE);
300 schedule_timeout(timeout: 2 * HZ);
301
302 if (ret)
303 continue;
304 t ^= 1;
305 ret = modify_ftrace_direct(ops: &direct, addr: tramps[t]);
306 if (!ret)
307 my_tramp = tramps[t];
308 WARN_ON_ONCE(ret);
309 }
310
311 return 0;
312}
313
314static struct task_struct *simple_tsk;
315
316static int __init ftrace_direct_init(void)
317{
318 int ret;
319
320 ftrace_set_filter_ip(ops: &direct, ip: (unsigned long) my_ip, remove: 0, reset: 0);
321 ret = register_ftrace_direct(ops: &direct, addr: my_tramp);
322
323 if (!ret)
324 simple_tsk = kthread_run(simple_thread, NULL, "event-sample-fn");
325 return ret;
326}
327
328static void __exit ftrace_direct_exit(void)
329{
330 kthread_stop(k: simple_tsk);
331 unregister_ftrace_direct(ops: &direct, addr: my_tramp, free_filters: true);
332}
333
334module_init(ftrace_direct_init);
335module_exit(ftrace_direct_exit);
336
337MODULE_AUTHOR("Steven Rostedt");
338MODULE_DESCRIPTION("Example use case of using modify_ftrace_direct()");
339MODULE_LICENSE("GPL");
340

source code of linux/samples/ftrace/ftrace-direct-modify.c