Commit | Line | Data |
---|---|---|
3d083395 SR |
1 | /* |
2 | * Code for replacing ftrace calls with jumps. | |
3 | * | |
4 | * Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com> | |
5 | * | |
6 | * Thanks goes to Ingo Molnar, for suggesting the idea. | |
7 | * Mathieu Desnoyers, for suggesting postponing the modifications. | |
8 | * Arjan van de Ven, for keeping me straight, and explaining to me | |
9 | * the dangers of modifying code on the run. | |
10 | */ | |
11 | ||
3bb258bf JP |
12 | #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt |
13 | ||
3d083395 SR |
14 | #include <linux/spinlock.h> |
15 | #include <linux/hardirq.h> | |
6f93fc07 | 16 | #include <linux/uaccess.h> |
3d083395 SR |
17 | #include <linux/ftrace.h> |
18 | #include <linux/percpu.h> | |
19b3e967 | 19 | #include <linux/sched.h> |
3d083395 SR |
20 | #include <linux/init.h> |
21 | #include <linux/list.h> | |
84e1c6bb | 22 | #include <linux/module.h> |
3d083395 | 23 | |
47788c58 FW |
24 | #include <trace/syscall.h> |
25 | ||
16239630 | 26 | #include <asm/cacheflush.h> |
59a094c9 | 27 | #include <asm/kprobes.h> |
395a59d0 | 28 | #include <asm/ftrace.h> |
732f3ca7 | 29 | #include <asm/nops.h> |
3d083395 | 30 | |
caf4b323 | 31 | #ifdef CONFIG_DYNAMIC_FTRACE |
3d083395 | 32 | |
16239630 SR |
33 | int ftrace_arch_code_modify_prepare(void) |
34 | { | |
35 | set_kernel_text_rw(); | |
84e1c6bb | 36 | set_all_modules_text_rw(); |
16239630 SR |
37 | return 0; |
38 | } | |
39 | ||
40 | int ftrace_arch_code_modify_post_process(void) | |
41 | { | |
84e1c6bb | 42 | set_all_modules_text_ro(); |
16239630 SR |
43 | set_kernel_text_ro(); |
44 | return 0; | |
45 | } | |
46 | ||
3d083395 | 47 | union ftrace_code_union { |
395a59d0 | 48 | char code[MCOUNT_INSN_SIZE]; |
3d083395 SR |
49 | struct { |
50 | char e8; | |
51 | int offset; | |
52 | } __attribute__((packed)); | |
53 | }; | |
54 | ||
15adc048 | 55 | static int ftrace_calc_offset(long ip, long addr) |
3c1720f0 SR |
56 | { |
57 | return (int)(addr - ip); | |
58 | } | |
3d083395 | 59 | |
31e88909 | 60 | static unsigned char *ftrace_call_replace(unsigned long ip, unsigned long addr) |
3c1720f0 SR |
61 | { |
62 | static union ftrace_code_union calc; | |
3d083395 | 63 | |
3c1720f0 | 64 | calc.e8 = 0xe8; |
395a59d0 | 65 | calc.offset = ftrace_calc_offset(ip + MCOUNT_INSN_SIZE, addr); |
3c1720f0 SR |
66 | |
67 | /* | |
68 | * No locking needed, this must be called via kstop_machine | |
69 | * which in essence is like running on a uniprocessor machine. | |
70 | */ | |
71 | return calc.code; | |
3d083395 SR |
72 | } |
73 | ||
55ca3cc1 SS |
74 | static inline int |
75 | within(unsigned long addr, unsigned long start, unsigned long end) | |
76 | { | |
77 | return addr >= start && addr < end; | |
78 | } | |
79 | ||
17666f02 | 80 | static int |
0d098a7d | 81 | do_ftrace_mod_code(unsigned long ip, const void *new_code) |
17666f02 | 82 | { |
55ca3cc1 SS |
83 | /* |
84 | * On x86_64, kernel text mappings are mapped read-only with | |
85 | * CONFIG_DEBUG_RODATA. So we use the kernel identity mapping instead | |
86 | * of the kernel text mapping to modify the kernel text. | |
87 | * | |
88 | * For 32bit kernels, these mappings are same and we can use | |
89 | * kernel identity mapping to modify code. | |
90 | */ | |
91 | if (within(ip, (unsigned long)_text, (unsigned long)_etext)) | |
92 | ip = (unsigned long)__va(__pa(ip)); | |
93 | ||
4a6d70c9 | 94 | return probe_kernel_write((void *)ip, new_code, MCOUNT_INSN_SIZE); |
17666f02 SR |
95 | } |
96 | ||
dc326fca | 97 | static const unsigned char *ftrace_nop_replace(void) |
caf4b323 | 98 | { |
dc326fca | 99 | return ideal_nops[NOP_ATOMIC5]; |
caf4b323 FW |
100 | } |
101 | ||
31e88909 | 102 | static int |
0d098a7d RM |
103 | ftrace_modify_code(unsigned long ip, unsigned const char *old_code, |
104 | unsigned const char *new_code) | |
3d083395 | 105 | { |
6f93fc07 | 106 | unsigned char replaced[MCOUNT_INSN_SIZE]; |
3d083395 SR |
107 | |
108 | /* | |
109 | * Note: Due to modules and __init, code can | |
110 | * disappear and change, we need to protect against faulting | |
76aefee5 | 111 | * as well as code changing. We do this by using the |
ab9a0918 | 112 | * probe_kernel_* functions. |
3d083395 SR |
113 | * |
114 | * No real locking needed, this code is run through | |
6f93fc07 | 115 | * kstop_machine, or before SMP starts. |
3d083395 | 116 | */ |
76aefee5 SR |
117 | |
118 | /* read the text we want to modify */ | |
ab9a0918 | 119 | if (probe_kernel_read(replaced, (void *)ip, MCOUNT_INSN_SIZE)) |
593eb8a2 | 120 | return -EFAULT; |
6f93fc07 | 121 | |
76aefee5 | 122 | /* Make sure it is what we expect it to be */ |
6f93fc07 | 123 | if (memcmp(replaced, old_code, MCOUNT_INSN_SIZE) != 0) |
593eb8a2 | 124 | return -EINVAL; |
3d083395 | 125 | |
76aefee5 | 126 | /* replace the text with the new text */ |
17666f02 | 127 | if (do_ftrace_mod_code(ip, new_code)) |
593eb8a2 | 128 | return -EPERM; |
6f93fc07 SR |
129 | |
130 | sync_core(); | |
3d083395 | 131 | |
6f93fc07 | 132 | return 0; |
3d083395 SR |
133 | } |
134 | ||
31e88909 SR |
135 | int ftrace_make_nop(struct module *mod, |
136 | struct dyn_ftrace *rec, unsigned long addr) | |
137 | { | |
0d098a7d | 138 | unsigned const char *new, *old; |
31e88909 SR |
139 | unsigned long ip = rec->ip; |
140 | ||
141 | old = ftrace_call_replace(ip, addr); | |
142 | new = ftrace_nop_replace(); | |
143 | ||
144 | return ftrace_modify_code(rec->ip, old, new); | |
145 | } | |
146 | ||
147 | int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr) | |
148 | { | |
0d098a7d | 149 | unsigned const char *new, *old; |
31e88909 SR |
150 | unsigned long ip = rec->ip; |
151 | ||
152 | old = ftrace_nop_replace(); | |
153 | new = ftrace_call_replace(ip, addr); | |
154 | ||
155 | return ftrace_modify_code(rec->ip, old, new); | |
156 | } | |
157 | ||
15adc048 | 158 | int ftrace_update_ftrace_func(ftrace_func_t func) |
d61f82d0 SR |
159 | { |
160 | unsigned long ip = (unsigned long)(&ftrace_call); | |
395a59d0 | 161 | unsigned char old[MCOUNT_INSN_SIZE], *new; |
d61f82d0 SR |
162 | int ret; |
163 | ||
395a59d0 | 164 | memcpy(old, &ftrace_call, MCOUNT_INSN_SIZE); |
d61f82d0 SR |
165 | new = ftrace_call_replace(ip, (unsigned long)func); |
166 | ret = ftrace_modify_code(ip, old, new); | |
167 | ||
168 | return ret; | |
169 | } | |
170 | ||
a192cd04 SR |
171 | /* |
172 | * The modifying_ftrace_code is used to tell the breakpoint | |
173 | * handler to call ftrace_int3_handler(). If it fails to | |
174 | * call this handler for a breakpoint added by ftrace, then | |
175 | * the kernel may crash. | |
176 | * | |
177 | * As atomic_writes on x86 do not need a barrier, we do not | |
178 | * need to add smp_mb()s for this to work. It is also considered | |
179 | * that we can not read the modifying_ftrace_code before | |
180 | * executing the breakpoint. That would be quite remarkable if | |
181 | * it could do that. Here's the flow that is required: | |
182 | * | |
183 | * CPU-0 CPU-1 | |
184 | * | |
185 | * atomic_inc(mfc); | |
186 | * write int3s | |
187 | * <trap-int3> // implicit (r)mb | |
188 | * if (atomic_read(mfc)) | |
189 | * call ftrace_int3_handler() | |
190 | * | |
191 | * Then when we are finished: | |
192 | * | |
193 | * atomic_dec(mfc); | |
194 | * | |
195 | * If we hit a breakpoint that was not set by ftrace, it does not | |
196 | * matter if ftrace_int3_handler() is called or not. It will | |
197 | * simply be ignored. But it is crucial that a ftrace nop/caller | |
198 | * breakpoint is handled. No other user should ever place a | |
199 | * breakpoint on an ftrace nop/caller location. It must only | |
200 | * be done by this code. | |
201 | */ | |
202 | atomic_t modifying_ftrace_code __read_mostly; | |
08d636b6 SR |
203 | |
204 | /* | |
205 | * A breakpoint was added to the code address we are about to | |
206 | * modify, and this is the handle that will just skip over it. | |
207 | * We are either changing a nop into a trace call, or a trace | |
208 | * call to a nop. While the change is taking place, we treat | |
209 | * it just like it was a nop. | |
210 | */ | |
211 | int ftrace_int3_handler(struct pt_regs *regs) | |
212 | { | |
213 | if (WARN_ON_ONCE(!regs)) | |
214 | return 0; | |
215 | ||
216 | if (!ftrace_location(regs->ip - 1)) | |
217 | return 0; | |
218 | ||
219 | regs->ip += MCOUNT_INSN_SIZE - 1; | |
220 | ||
221 | return 1; | |
222 | } | |
223 | ||
224 | static int ftrace_write(unsigned long ip, const char *val, int size) | |
225 | { | |
226 | /* | |
227 | * On x86_64, kernel text mappings are mapped read-only with | |
228 | * CONFIG_DEBUG_RODATA. So we use the kernel identity mapping instead | |
229 | * of the kernel text mapping to modify the kernel text. | |
230 | * | |
231 | * For 32bit kernels, these mappings are same and we can use | |
232 | * kernel identity mapping to modify code. | |
233 | */ | |
234 | if (within(ip, (unsigned long)_text, (unsigned long)_etext)) | |
235 | ip = (unsigned long)__va(__pa(ip)); | |
236 | ||
237 | return probe_kernel_write((void *)ip, val, size); | |
238 | } | |
239 | ||
240 | static int add_break(unsigned long ip, const char *old) | |
241 | { | |
242 | unsigned char replaced[MCOUNT_INSN_SIZE]; | |
243 | unsigned char brk = BREAKPOINT_INSTRUCTION; | |
244 | ||
245 | if (probe_kernel_read(replaced, (void *)ip, MCOUNT_INSN_SIZE)) | |
246 | return -EFAULT; | |
247 | ||
248 | /* Make sure it is what we expect it to be */ | |
249 | if (memcmp(replaced, old, MCOUNT_INSN_SIZE) != 0) | |
250 | return -EINVAL; | |
251 | ||
252 | if (ftrace_write(ip, &brk, 1)) | |
253 | return -EPERM; | |
254 | ||
255 | return 0; | |
256 | } | |
257 | ||
258 | static int add_brk_on_call(struct dyn_ftrace *rec, unsigned long addr) | |
259 | { | |
260 | unsigned const char *old; | |
261 | unsigned long ip = rec->ip; | |
262 | ||
263 | old = ftrace_call_replace(ip, addr); | |
264 | ||
265 | return add_break(rec->ip, old); | |
266 | } | |
267 | ||
268 | ||
269 | static int add_brk_on_nop(struct dyn_ftrace *rec) | |
270 | { | |
271 | unsigned const char *old; | |
272 | ||
273 | old = ftrace_nop_replace(); | |
274 | ||
275 | return add_break(rec->ip, old); | |
276 | } | |
277 | ||
278 | static int add_breakpoints(struct dyn_ftrace *rec, int enable) | |
279 | { | |
280 | unsigned long ftrace_addr; | |
281 | int ret; | |
282 | ||
283 | ret = ftrace_test_record(rec, enable); | |
284 | ||
285 | ftrace_addr = (unsigned long)FTRACE_ADDR; | |
286 | ||
287 | switch (ret) { | |
288 | case FTRACE_UPDATE_IGNORE: | |
289 | return 0; | |
290 | ||
291 | case FTRACE_UPDATE_MAKE_CALL: | |
292 | /* converting nop to call */ | |
293 | return add_brk_on_nop(rec); | |
294 | ||
295 | case FTRACE_UPDATE_MAKE_NOP: | |
296 | /* converting a call to a nop */ | |
297 | return add_brk_on_call(rec, ftrace_addr); | |
298 | } | |
299 | return 0; | |
300 | } | |
301 | ||
302 | /* | |
303 | * On error, we need to remove breakpoints. This needs to | |
304 | * be done caefully. If the address does not currently have a | |
305 | * breakpoint, we know we are done. Otherwise, we look at the | |
306 | * remaining 4 bytes of the instruction. If it matches a nop | |
307 | * we replace the breakpoint with the nop. Otherwise we replace | |
308 | * it with the call instruction. | |
309 | */ | |
310 | static int remove_breakpoint(struct dyn_ftrace *rec) | |
311 | { | |
312 | unsigned char ins[MCOUNT_INSN_SIZE]; | |
313 | unsigned char brk = BREAKPOINT_INSTRUCTION; | |
314 | const unsigned char *nop; | |
315 | unsigned long ftrace_addr; | |
316 | unsigned long ip = rec->ip; | |
317 | ||
318 | /* If we fail the read, just give up */ | |
319 | if (probe_kernel_read(ins, (void *)ip, MCOUNT_INSN_SIZE)) | |
320 | return -EFAULT; | |
321 | ||
322 | /* If this does not have a breakpoint, we are done */ | |
323 | if (ins[0] != brk) | |
324 | return -1; | |
325 | ||
326 | nop = ftrace_nop_replace(); | |
327 | ||
328 | /* | |
329 | * If the last 4 bytes of the instruction do not match | |
330 | * a nop, then we assume that this is a call to ftrace_addr. | |
331 | */ | |
332 | if (memcmp(&ins[1], &nop[1], MCOUNT_INSN_SIZE - 1) != 0) { | |
333 | /* | |
334 | * For extra paranoidism, we check if the breakpoint is on | |
335 | * a call that would actually jump to the ftrace_addr. | |
336 | * If not, don't touch the breakpoint, we make just create | |
337 | * a disaster. | |
338 | */ | |
339 | ftrace_addr = (unsigned long)FTRACE_ADDR; | |
340 | nop = ftrace_call_replace(ip, ftrace_addr); | |
341 | ||
342 | if (memcmp(&ins[1], &nop[1], MCOUNT_INSN_SIZE - 1) != 0) | |
343 | return -EINVAL; | |
344 | } | |
345 | ||
346 | return probe_kernel_write((void *)ip, &nop[0], 1); | |
347 | } | |
348 | ||
349 | static int add_update_code(unsigned long ip, unsigned const char *new) | |
350 | { | |
351 | /* skip breakpoint */ | |
352 | ip++; | |
353 | new++; | |
354 | if (ftrace_write(ip, new, MCOUNT_INSN_SIZE - 1)) | |
355 | return -EPERM; | |
356 | return 0; | |
357 | } | |
358 | ||
359 | static int add_update_call(struct dyn_ftrace *rec, unsigned long addr) | |
360 | { | |
361 | unsigned long ip = rec->ip; | |
362 | unsigned const char *new; | |
363 | ||
364 | new = ftrace_call_replace(ip, addr); | |
365 | return add_update_code(ip, new); | |
366 | } | |
367 | ||
368 | static int add_update_nop(struct dyn_ftrace *rec) | |
369 | { | |
370 | unsigned long ip = rec->ip; | |
371 | unsigned const char *new; | |
372 | ||
373 | new = ftrace_nop_replace(); | |
374 | return add_update_code(ip, new); | |
375 | } | |
376 | ||
377 | static int add_update(struct dyn_ftrace *rec, int enable) | |
378 | { | |
379 | unsigned long ftrace_addr; | |
380 | int ret; | |
381 | ||
382 | ret = ftrace_test_record(rec, enable); | |
383 | ||
384 | ftrace_addr = (unsigned long)FTRACE_ADDR; | |
385 | ||
386 | switch (ret) { | |
387 | case FTRACE_UPDATE_IGNORE: | |
388 | return 0; | |
389 | ||
390 | case FTRACE_UPDATE_MAKE_CALL: | |
391 | /* converting nop to call */ | |
392 | return add_update_call(rec, ftrace_addr); | |
393 | ||
394 | case FTRACE_UPDATE_MAKE_NOP: | |
395 | /* converting a call to a nop */ | |
396 | return add_update_nop(rec); | |
397 | } | |
398 | ||
399 | return 0; | |
400 | } | |
401 | ||
402 | static int finish_update_call(struct dyn_ftrace *rec, unsigned long addr) | |
403 | { | |
404 | unsigned long ip = rec->ip; | |
405 | unsigned const char *new; | |
406 | ||
407 | new = ftrace_call_replace(ip, addr); | |
408 | ||
409 | if (ftrace_write(ip, new, 1)) | |
410 | return -EPERM; | |
411 | ||
412 | return 0; | |
413 | } | |
414 | ||
415 | static int finish_update_nop(struct dyn_ftrace *rec) | |
416 | { | |
417 | unsigned long ip = rec->ip; | |
418 | unsigned const char *new; | |
419 | ||
420 | new = ftrace_nop_replace(); | |
421 | ||
422 | if (ftrace_write(ip, new, 1)) | |
423 | return -EPERM; | |
424 | return 0; | |
425 | } | |
426 | ||
427 | static int finish_update(struct dyn_ftrace *rec, int enable) | |
428 | { | |
429 | unsigned long ftrace_addr; | |
430 | int ret; | |
431 | ||
432 | ret = ftrace_update_record(rec, enable); | |
433 | ||
434 | ftrace_addr = (unsigned long)FTRACE_ADDR; | |
435 | ||
436 | switch (ret) { | |
437 | case FTRACE_UPDATE_IGNORE: | |
438 | return 0; | |
439 | ||
440 | case FTRACE_UPDATE_MAKE_CALL: | |
441 | /* converting nop to call */ | |
442 | return finish_update_call(rec, ftrace_addr); | |
443 | ||
444 | case FTRACE_UPDATE_MAKE_NOP: | |
445 | /* converting a call to a nop */ | |
446 | return finish_update_nop(rec); | |
447 | } | |
448 | ||
449 | return 0; | |
450 | } | |
451 | ||
452 | static void do_sync_core(void *data) | |
453 | { | |
454 | sync_core(); | |
455 | } | |
456 | ||
457 | static void run_sync(void) | |
458 | { | |
459 | int enable_irqs = irqs_disabled(); | |
460 | ||
461 | /* We may be called with interrupts disbled (on bootup). */ | |
462 | if (enable_irqs) | |
463 | local_irq_enable(); | |
464 | on_each_cpu(do_sync_core, NULL, 1); | |
465 | if (enable_irqs) | |
466 | local_irq_disable(); | |
467 | } | |
468 | ||
e4f5d544 | 469 | void ftrace_replace_code(int enable) |
08d636b6 SR |
470 | { |
471 | struct ftrace_rec_iter *iter; | |
472 | struct dyn_ftrace *rec; | |
473 | const char *report = "adding breakpoints"; | |
474 | int count = 0; | |
475 | int ret; | |
476 | ||
477 | for_ftrace_rec_iter(iter) { | |
478 | rec = ftrace_rec_iter_record(iter); | |
479 | ||
480 | ret = add_breakpoints(rec, enable); | |
481 | if (ret) | |
482 | goto remove_breakpoints; | |
483 | count++; | |
484 | } | |
485 | ||
486 | run_sync(); | |
487 | ||
488 | report = "updating code"; | |
489 | ||
490 | for_ftrace_rec_iter(iter) { | |
491 | rec = ftrace_rec_iter_record(iter); | |
492 | ||
493 | ret = add_update(rec, enable); | |
494 | if (ret) | |
495 | goto remove_breakpoints; | |
496 | } | |
497 | ||
498 | run_sync(); | |
499 | ||
500 | report = "removing breakpoints"; | |
501 | ||
502 | for_ftrace_rec_iter(iter) { | |
503 | rec = ftrace_rec_iter_record(iter); | |
504 | ||
505 | ret = finish_update(rec, enable); | |
506 | if (ret) | |
507 | goto remove_breakpoints; | |
508 | } | |
509 | ||
510 | run_sync(); | |
511 | ||
512 | return; | |
513 | ||
514 | remove_breakpoints: | |
515 | ftrace_bug(ret, rec ? rec->ip : 0); | |
516 | printk(KERN_WARNING "Failed on %s (%d):\n", report, count); | |
517 | for_ftrace_rec_iter(iter) { | |
518 | rec = ftrace_rec_iter_record(iter); | |
519 | remove_breakpoint(rec); | |
520 | } | |
521 | } | |
522 | ||
523 | void arch_ftrace_update_code(int command) | |
524 | { | |
a192cd04 SR |
525 | /* See comment above by declaration of modifying_ftrace_code */ |
526 | atomic_inc(&modifying_ftrace_code); | |
08d636b6 | 527 | |
e4f5d544 | 528 | ftrace_modify_all_code(command); |
08d636b6 | 529 | |
a192cd04 | 530 | atomic_dec(&modifying_ftrace_code); |
08d636b6 SR |
531 | } |
532 | ||
d61f82d0 | 533 | int __init ftrace_dyn_arch_init(void *data) |
3d083395 | 534 | { |
732f3ca7 SR |
535 | /* The return code is retured via data */ |
536 | *(unsigned long *)data = 0; | |
dfa60aba | 537 | |
3d083395 SR |
538 | return 0; |
539 | } | |
caf4b323 | 540 | #endif |
e7d3737e | 541 | |
fb52607a | 542 | #ifdef CONFIG_FUNCTION_GRAPH_TRACER |
e7d3737e | 543 | |
5a45cfe1 SR |
544 | #ifdef CONFIG_DYNAMIC_FTRACE |
545 | extern void ftrace_graph_call(void); | |
546 | ||
547 | static int ftrace_mod_jmp(unsigned long ip, | |
548 | int old_offset, int new_offset) | |
549 | { | |
550 | unsigned char code[MCOUNT_INSN_SIZE]; | |
551 | ||
552 | if (probe_kernel_read(code, (void *)ip, MCOUNT_INSN_SIZE)) | |
553 | return -EFAULT; | |
554 | ||
555 | if (code[0] != 0xe9 || old_offset != *(int *)(&code[1])) | |
556 | return -EINVAL; | |
557 | ||
558 | *(int *)(&code[1]) = new_offset; | |
559 | ||
560 | if (do_ftrace_mod_code(ip, &code)) | |
561 | return -EPERM; | |
562 | ||
563 | return 0; | |
564 | } | |
565 | ||
566 | int ftrace_enable_ftrace_graph_caller(void) | |
567 | { | |
568 | unsigned long ip = (unsigned long)(&ftrace_graph_call); | |
569 | int old_offset, new_offset; | |
570 | ||
571 | old_offset = (unsigned long)(&ftrace_stub) - (ip + MCOUNT_INSN_SIZE); | |
572 | new_offset = (unsigned long)(&ftrace_graph_caller) - (ip + MCOUNT_INSN_SIZE); | |
573 | ||
574 | return ftrace_mod_jmp(ip, old_offset, new_offset); | |
575 | } | |
576 | ||
577 | int ftrace_disable_ftrace_graph_caller(void) | |
578 | { | |
579 | unsigned long ip = (unsigned long)(&ftrace_graph_call); | |
580 | int old_offset, new_offset; | |
581 | ||
582 | old_offset = (unsigned long)(&ftrace_graph_caller) - (ip + MCOUNT_INSN_SIZE); | |
583 | new_offset = (unsigned long)(&ftrace_stub) - (ip + MCOUNT_INSN_SIZE); | |
584 | ||
585 | return ftrace_mod_jmp(ip, old_offset, new_offset); | |
586 | } | |
587 | ||
e7d3737e FW |
588 | #endif /* !CONFIG_DYNAMIC_FTRACE */ |
589 | ||
e7d3737e FW |
590 | /* |
591 | * Hook the return address and push it in the stack of return addrs | |
592 | * in current thread info. | |
593 | */ | |
71e308a2 SR |
594 | void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr, |
595 | unsigned long frame_pointer) | |
e7d3737e FW |
596 | { |
597 | unsigned long old; | |
e7d3737e | 598 | int faulted; |
287b6e68 | 599 | struct ftrace_graph_ent trace; |
e7d3737e FW |
600 | unsigned long return_hooker = (unsigned long) |
601 | &return_to_handler; | |
602 | ||
380c4b14 | 603 | if (unlikely(atomic_read(¤t->tracing_graph_pause))) |
e7d3737e FW |
604 | return; |
605 | ||
606 | /* | |
607 | * Protect against fault, even if it shouldn't | |
608 | * happen. This tool is too much intrusive to | |
609 | * ignore such a protection. | |
610 | */ | |
611 | asm volatile( | |
96665788 SR |
612 | "1: " _ASM_MOV " (%[parent]), %[old]\n" |
613 | "2: " _ASM_MOV " %[return_hooker], (%[parent])\n" | |
e7d3737e | 614 | " movl $0, %[faulted]\n" |
e3944bfa | 615 | "3:\n" |
e7d3737e FW |
616 | |
617 | ".section .fixup, \"ax\"\n" | |
e3944bfa SR |
618 | "4: movl $1, %[faulted]\n" |
619 | " jmp 3b\n" | |
e7d3737e FW |
620 | ".previous\n" |
621 | ||
e3944bfa SR |
622 | _ASM_EXTABLE(1b, 4b) |
623 | _ASM_EXTABLE(2b, 4b) | |
e7d3737e | 624 | |
aa512a27 | 625 | : [old] "=&r" (old), [faulted] "=r" (faulted) |
96665788 | 626 | : [parent] "r" (parent), [return_hooker] "r" (return_hooker) |
e7d3737e FW |
627 | : "memory" |
628 | ); | |
629 | ||
14a866c5 SR |
630 | if (unlikely(faulted)) { |
631 | ftrace_graph_stop(); | |
632 | WARN_ON(1); | |
e7d3737e FW |
633 | return; |
634 | } | |
635 | ||
287b6e68 | 636 | trace.func = self_addr; |
722b3c74 | 637 | trace.depth = current->curr_ret_stack + 1; |
287b6e68 | 638 | |
e49dc19c SR |
639 | /* Only trace if the calling function expects to */ |
640 | if (!ftrace_graph_entry(&trace)) { | |
e49dc19c | 641 | *parent = old; |
722b3c74 SR |
642 | return; |
643 | } | |
644 | ||
645 | if (ftrace_push_return_trace(old, self_addr, &trace.depth, | |
646 | frame_pointer) == -EBUSY) { | |
647 | *parent = old; | |
648 | return; | |
e49dc19c | 649 | } |
e7d3737e | 650 | } |
fb52607a | 651 | #endif /* CONFIG_FUNCTION_GRAPH_TRACER */ |