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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#if !defined(CONFIG_ARM64) && !defined(CONFIG_PPC32)
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 $ra, $sp, 8\n"
203" ld.d $t0, $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 $ra, $sp, 8\n"
219" ld.d $t0, $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
228#ifdef CONFIG_PPC
229#include <asm/ppc_asm.h>
230
231#ifdef CONFIG_PPC64
232#define STACK_FRAME_SIZE 48
233#else
234#define STACK_FRAME_SIZE 24
235#endif
236
237#if defined(CONFIG_PPC64_ELF_ABI_V2) && !defined(CONFIG_PPC_KERNEL_PCREL)
238#define PPC64_TOC_SAVE_AND_UPDATE \
239" std 2, 24(1)\n" \
240" bcl 20, 31, 1f\n" \
241" 1: mflr 12\n" \
242" ld 2, (99f - 1b)(12)\n"
243#define PPC64_TOC_RESTORE \
244" ld 2, 24(1)\n"
245#define PPC64_TOC \
246" 99: .quad .TOC.@tocbase\n"
247#else
248#define PPC64_TOC_SAVE_AND_UPDATE ""
249#define PPC64_TOC_RESTORE ""
250#define PPC64_TOC ""
251#endif
252
253#ifdef CONFIG_PPC_FTRACE_OUT_OF_LINE
254#define PPC_FTRACE_RESTORE_LR \
255 PPC_LL" 0, "__stringify(PPC_LR_STKOFF)"(1)\n" \
256" mtlr 0\n"
257#define PPC_FTRACE_RET \
258" blr\n"
259#define PPC_FTRACE_RECOVER_IP \
260" lwz 8, 4(3)\n" \
261" li 9, 6\n" \
262" slw 8, 8, 9\n" \
263" sraw 8, 8, 9\n" \
264" add 3, 3, 8\n" \
265" addi 3, 3, 4\n"
266#else
267#define PPC_FTRACE_RESTORE_LR \
268 PPC_LL" 0, "__stringify(PPC_LR_STKOFF)"(1)\n" \
269" mtctr 0\n"
270#define PPC_FTRACE_RET \
271" mtlr 0\n" \
272" bctr\n"
273#define PPC_FTRACE_RECOVER_IP ""
274#endif
275
276asm (
277" .pushsection .text, \"ax\", @progbits\n"
278" .type my_tramp1, @function\n"
279" .globl my_tramp1\n"
280" my_tramp1:\n"
281 PPC_STL" 0, "__stringify(PPC_LR_STKOFF)"(1)\n"
282 PPC_STLU" 1, -"__stringify(STACK_FRAME_MIN_SIZE)"(1)\n"
283" mflr 0\n"
284 PPC_STL" 0, "__stringify(PPC_LR_STKOFF)"(1)\n"
285 PPC_STLU" 1, -"__stringify(STACK_FRAME_SIZE)"(1)\n"
286 PPC64_TOC_SAVE_AND_UPDATE
287 PPC_STL" 3, "__stringify(STACK_FRAME_MIN_SIZE)"(1)\n"
288" mr 3, 0\n"
289 PPC_FTRACE_RECOVER_IP
290" bl my_direct_func1\n"
291 PPC_LL" 3, "__stringify(STACK_FRAME_MIN_SIZE)"(1)\n"
292 PPC64_TOC_RESTORE
293" addi 1, 1, "__stringify(STACK_FRAME_SIZE)"\n"
294 PPC_FTRACE_RESTORE_LR
295" addi 1, 1, "__stringify(STACK_FRAME_MIN_SIZE)"\n"
296 PPC_LL" 0, "__stringify(PPC_LR_STKOFF)"(1)\n"
297 PPC_FTRACE_RET
298" .size my_tramp1, .-my_tramp1\n"
299
300" .type my_tramp2, @function\n"
301" .globl my_tramp2\n"
302" my_tramp2:\n"
303 PPC_STL" 0, "__stringify(PPC_LR_STKOFF)"(1)\n"
304 PPC_STLU" 1, -"__stringify(STACK_FRAME_MIN_SIZE)"(1)\n"
305" mflr 0\n"
306 PPC_STL" 0, "__stringify(PPC_LR_STKOFF)"(1)\n"
307 PPC_STLU" 1, -"__stringify(STACK_FRAME_SIZE)"(1)\n"
308 PPC64_TOC_SAVE_AND_UPDATE
309 PPC_STL" 3, "__stringify(STACK_FRAME_MIN_SIZE)"(1)\n"
310" mr 3, 0\n"
311 PPC_FTRACE_RECOVER_IP
312" bl my_direct_func2\n"
313 PPC_LL" 3, "__stringify(STACK_FRAME_MIN_SIZE)"(1)\n"
314 PPC64_TOC_RESTORE
315" addi 1, 1, "__stringify(STACK_FRAME_SIZE)"\n"
316 PPC_FTRACE_RESTORE_LR
317" addi 1, 1, "__stringify(STACK_FRAME_MIN_SIZE)"\n"
318 PPC_LL" 0, "__stringify(PPC_LR_STKOFF)"(1)\n"
319 PPC_FTRACE_RET
320 PPC64_TOC
321 " .size my_tramp2, .-my_tramp2\n"
322" .popsection\n"
323);
324
325#endif /* CONFIG_PPC */
326
327static unsigned long my_tramp = (unsigned long)my_tramp1;
328static unsigned long tramps[2] = {
329 (unsigned long)my_tramp1,
330 (unsigned long)my_tramp2,
331};
332
333static struct ftrace_ops direct;
334
335static int simple_thread(void *arg)
336{
337 static int t;
338 int ret = 0;
339
340 while (!kthread_should_stop()) {
341 set_current_state(TASK_INTERRUPTIBLE);
342 schedule_timeout(2 * HZ);
343
344 if (ret)
345 continue;
346 t ^= 1;
347 ret = modify_ftrace_direct(&direct, tramps[t]);
348 if (!ret)
349 my_tramp = tramps[t];
350 WARN_ON_ONCE(ret);
351 }
352
353 return 0;
354}
355
356static struct task_struct *simple_tsk;
357
358static int __init ftrace_direct_multi_init(void)
359{
360 int ret;
361
362 ftrace_set_filter_ip(&direct, (unsigned long) wake_up_process, 0, 0);
363 ftrace_set_filter_ip(&direct, (unsigned long) schedule, 0, 0);
364
365 ret = register_ftrace_direct(&direct, my_tramp);
366
367 if (ret)
368 return ret;
369 simple_tsk = kthread_run(simple_thread, NULL, "event-sample-fn");
370 if (IS_ERR(simple_tsk)) {
371 unregister_ftrace_direct(&direct, my_tramp, true);
372 return PTR_ERR(simple_tsk);
373 }
374
375 return 0;
376}
377
378static void __exit ftrace_direct_multi_exit(void)
379{
380 kthread_stop(simple_tsk);
381 unregister_ftrace_direct(&direct, my_tramp, true);
382}
383
384module_init(ftrace_direct_multi_init);
385module_exit(ftrace_direct_multi_exit);
386
387MODULE_AUTHOR("Jiri Olsa");
388MODULE_DESCRIPTION("Example use case of using modify_ftrace_direct()");
389MODULE_LICENSE("GPL");