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Commit | Line | Data |
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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 | ||
08d636b6 SR |
171 | int modifying_ftrace_code __read_mostly; |
172 | ||
173 | /* | |
174 | * A breakpoint was added to the code address we are about to | |
175 | * modify, and this is the handle that will just skip over it. | |
176 | * We are either changing a nop into a trace call, or a trace | |
177 | * call to a nop. While the change is taking place, we treat | |
178 | * it just like it was a nop. | |
179 | */ | |
180 | int ftrace_int3_handler(struct pt_regs *regs) | |
181 | { | |
182 | if (WARN_ON_ONCE(!regs)) | |
183 | return 0; | |
184 | ||
185 | if (!ftrace_location(regs->ip - 1)) | |
186 | return 0; | |
187 | ||
188 | regs->ip += MCOUNT_INSN_SIZE - 1; | |
189 | ||
190 | return 1; | |
191 | } | |
192 | ||
193 | static int ftrace_write(unsigned long ip, const char *val, int size) | |
194 | { | |
195 | /* | |
196 | * On x86_64, kernel text mappings are mapped read-only with | |
197 | * CONFIG_DEBUG_RODATA. So we use the kernel identity mapping instead | |
198 | * of the kernel text mapping to modify the kernel text. | |
199 | * | |
200 | * For 32bit kernels, these mappings are same and we can use | |
201 | * kernel identity mapping to modify code. | |
202 | */ | |
203 | if (within(ip, (unsigned long)_text, (unsigned long)_etext)) | |
204 | ip = (unsigned long)__va(__pa(ip)); | |
205 | ||
206 | return probe_kernel_write((void *)ip, val, size); | |
207 | } | |
208 | ||
209 | static int add_break(unsigned long ip, const char *old) | |
210 | { | |
211 | unsigned char replaced[MCOUNT_INSN_SIZE]; | |
212 | unsigned char brk = BREAKPOINT_INSTRUCTION; | |
213 | ||
214 | if (probe_kernel_read(replaced, (void *)ip, MCOUNT_INSN_SIZE)) | |
215 | return -EFAULT; | |
216 | ||
217 | /* Make sure it is what we expect it to be */ | |
218 | if (memcmp(replaced, old, MCOUNT_INSN_SIZE) != 0) | |
219 | return -EINVAL; | |
220 | ||
221 | if (ftrace_write(ip, &brk, 1)) | |
222 | return -EPERM; | |
223 | ||
224 | return 0; | |
225 | } | |
226 | ||
227 | static int add_brk_on_call(struct dyn_ftrace *rec, unsigned long addr) | |
228 | { | |
229 | unsigned const char *old; | |
230 | unsigned long ip = rec->ip; | |
231 | ||
232 | old = ftrace_call_replace(ip, addr); | |
233 | ||
234 | return add_break(rec->ip, old); | |
235 | } | |
236 | ||
237 | ||
238 | static int add_brk_on_nop(struct dyn_ftrace *rec) | |
239 | { | |
240 | unsigned const char *old; | |
241 | ||
242 | old = ftrace_nop_replace(); | |
243 | ||
244 | return add_break(rec->ip, old); | |
245 | } | |
246 | ||
247 | static int add_breakpoints(struct dyn_ftrace *rec, int enable) | |
248 | { | |
249 | unsigned long ftrace_addr; | |
250 | int ret; | |
251 | ||
252 | ret = ftrace_test_record(rec, enable); | |
253 | ||
254 | ftrace_addr = (unsigned long)FTRACE_ADDR; | |
255 | ||
256 | switch (ret) { | |
257 | case FTRACE_UPDATE_IGNORE: | |
258 | return 0; | |
259 | ||
260 | case FTRACE_UPDATE_MAKE_CALL: | |
261 | /* converting nop to call */ | |
262 | return add_brk_on_nop(rec); | |
263 | ||
264 | case FTRACE_UPDATE_MAKE_NOP: | |
265 | /* converting a call to a nop */ | |
266 | return add_brk_on_call(rec, ftrace_addr); | |
267 | } | |
268 | return 0; | |
269 | } | |
270 | ||
271 | /* | |
272 | * On error, we need to remove breakpoints. This needs to | |
273 | * be done caefully. If the address does not currently have a | |
274 | * breakpoint, we know we are done. Otherwise, we look at the | |
275 | * remaining 4 bytes of the instruction. If it matches a nop | |
276 | * we replace the breakpoint with the nop. Otherwise we replace | |
277 | * it with the call instruction. | |
278 | */ | |
279 | static int remove_breakpoint(struct dyn_ftrace *rec) | |
280 | { | |
281 | unsigned char ins[MCOUNT_INSN_SIZE]; | |
282 | unsigned char brk = BREAKPOINT_INSTRUCTION; | |
283 | const unsigned char *nop; | |
284 | unsigned long ftrace_addr; | |
285 | unsigned long ip = rec->ip; | |
286 | ||
287 | /* If we fail the read, just give up */ | |
288 | if (probe_kernel_read(ins, (void *)ip, MCOUNT_INSN_SIZE)) | |
289 | return -EFAULT; | |
290 | ||
291 | /* If this does not have a breakpoint, we are done */ | |
292 | if (ins[0] != brk) | |
293 | return -1; | |
294 | ||
295 | nop = ftrace_nop_replace(); | |
296 | ||
297 | /* | |
298 | * If the last 4 bytes of the instruction do not match | |
299 | * a nop, then we assume that this is a call to ftrace_addr. | |
300 | */ | |
301 | if (memcmp(&ins[1], &nop[1], MCOUNT_INSN_SIZE - 1) != 0) { | |
302 | /* | |
303 | * For extra paranoidism, we check if the breakpoint is on | |
304 | * a call that would actually jump to the ftrace_addr. | |
305 | * If not, don't touch the breakpoint, we make just create | |
306 | * a disaster. | |
307 | */ | |
308 | ftrace_addr = (unsigned long)FTRACE_ADDR; | |
309 | nop = ftrace_call_replace(ip, ftrace_addr); | |
310 | ||
311 | if (memcmp(&ins[1], &nop[1], MCOUNT_INSN_SIZE - 1) != 0) | |
312 | return -EINVAL; | |
313 | } | |
314 | ||
315 | return probe_kernel_write((void *)ip, &nop[0], 1); | |
316 | } | |
317 | ||
318 | static int add_update_code(unsigned long ip, unsigned const char *new) | |
319 | { | |
320 | /* skip breakpoint */ | |
321 | ip++; | |
322 | new++; | |
323 | if (ftrace_write(ip, new, MCOUNT_INSN_SIZE - 1)) | |
324 | return -EPERM; | |
325 | return 0; | |
326 | } | |
327 | ||
328 | static int add_update_call(struct dyn_ftrace *rec, unsigned long addr) | |
329 | { | |
330 | unsigned long ip = rec->ip; | |
331 | unsigned const char *new; | |
332 | ||
333 | new = ftrace_call_replace(ip, addr); | |
334 | return add_update_code(ip, new); | |
335 | } | |
336 | ||
337 | static int add_update_nop(struct dyn_ftrace *rec) | |
338 | { | |
339 | unsigned long ip = rec->ip; | |
340 | unsigned const char *new; | |
341 | ||
342 | new = ftrace_nop_replace(); | |
343 | return add_update_code(ip, new); | |
344 | } | |
345 | ||
346 | static int add_update(struct dyn_ftrace *rec, int enable) | |
347 | { | |
348 | unsigned long ftrace_addr; | |
349 | int ret; | |
350 | ||
351 | ret = ftrace_test_record(rec, enable); | |
352 | ||
353 | ftrace_addr = (unsigned long)FTRACE_ADDR; | |
354 | ||
355 | switch (ret) { | |
356 | case FTRACE_UPDATE_IGNORE: | |
357 | return 0; | |
358 | ||
359 | case FTRACE_UPDATE_MAKE_CALL: | |
360 | /* converting nop to call */ | |
361 | return add_update_call(rec, ftrace_addr); | |
362 | ||
363 | case FTRACE_UPDATE_MAKE_NOP: | |
364 | /* converting a call to a nop */ | |
365 | return add_update_nop(rec); | |
366 | } | |
367 | ||
368 | return 0; | |
369 | } | |
370 | ||
371 | static int finish_update_call(struct dyn_ftrace *rec, unsigned long addr) | |
372 | { | |
373 | unsigned long ip = rec->ip; | |
374 | unsigned const char *new; | |
375 | ||
376 | new = ftrace_call_replace(ip, addr); | |
377 | ||
378 | if (ftrace_write(ip, new, 1)) | |
379 | return -EPERM; | |
380 | ||
381 | return 0; | |
382 | } | |
383 | ||
384 | static int finish_update_nop(struct dyn_ftrace *rec) | |
385 | { | |
386 | unsigned long ip = rec->ip; | |
387 | unsigned const char *new; | |
388 | ||
389 | new = ftrace_nop_replace(); | |
390 | ||
391 | if (ftrace_write(ip, new, 1)) | |
392 | return -EPERM; | |
393 | return 0; | |
394 | } | |
395 | ||
396 | static int finish_update(struct dyn_ftrace *rec, int enable) | |
397 | { | |
398 | unsigned long ftrace_addr; | |
399 | int ret; | |
400 | ||
401 | ret = ftrace_update_record(rec, enable); | |
402 | ||
403 | ftrace_addr = (unsigned long)FTRACE_ADDR; | |
404 | ||
405 | switch (ret) { | |
406 | case FTRACE_UPDATE_IGNORE: | |
407 | return 0; | |
408 | ||
409 | case FTRACE_UPDATE_MAKE_CALL: | |
410 | /* converting nop to call */ | |
411 | return finish_update_call(rec, ftrace_addr); | |
412 | ||
413 | case FTRACE_UPDATE_MAKE_NOP: | |
414 | /* converting a call to a nop */ | |
415 | return finish_update_nop(rec); | |
416 | } | |
417 | ||
418 | return 0; | |
419 | } | |
420 | ||
421 | static void do_sync_core(void *data) | |
422 | { | |
423 | sync_core(); | |
424 | } | |
425 | ||
426 | static void run_sync(void) | |
427 | { | |
428 | int enable_irqs = irqs_disabled(); | |
429 | ||
430 | /* We may be called with interrupts disbled (on bootup). */ | |
431 | if (enable_irqs) | |
432 | local_irq_enable(); | |
433 | on_each_cpu(do_sync_core, NULL, 1); | |
434 | if (enable_irqs) | |
435 | local_irq_disable(); | |
436 | } | |
437 | ||
438 | static void ftrace_replace_code(int enable) | |
439 | { | |
440 | struct ftrace_rec_iter *iter; | |
441 | struct dyn_ftrace *rec; | |
442 | const char *report = "adding breakpoints"; | |
443 | int count = 0; | |
444 | int ret; | |
445 | ||
446 | for_ftrace_rec_iter(iter) { | |
447 | rec = ftrace_rec_iter_record(iter); | |
448 | ||
449 | ret = add_breakpoints(rec, enable); | |
450 | if (ret) | |
451 | goto remove_breakpoints; | |
452 | count++; | |
453 | } | |
454 | ||
455 | run_sync(); | |
456 | ||
457 | report = "updating code"; | |
458 | ||
459 | for_ftrace_rec_iter(iter) { | |
460 | rec = ftrace_rec_iter_record(iter); | |
461 | ||
462 | ret = add_update(rec, enable); | |
463 | if (ret) | |
464 | goto remove_breakpoints; | |
465 | } | |
466 | ||
467 | run_sync(); | |
468 | ||
469 | report = "removing breakpoints"; | |
470 | ||
471 | for_ftrace_rec_iter(iter) { | |
472 | rec = ftrace_rec_iter_record(iter); | |
473 | ||
474 | ret = finish_update(rec, enable); | |
475 | if (ret) | |
476 | goto remove_breakpoints; | |
477 | } | |
478 | ||
479 | run_sync(); | |
480 | ||
481 | return; | |
482 | ||
483 | remove_breakpoints: | |
484 | ftrace_bug(ret, rec ? rec->ip : 0); | |
485 | printk(KERN_WARNING "Failed on %s (%d):\n", report, count); | |
486 | for_ftrace_rec_iter(iter) { | |
487 | rec = ftrace_rec_iter_record(iter); | |
488 | remove_breakpoint(rec); | |
489 | } | |
490 | } | |
491 | ||
492 | void arch_ftrace_update_code(int command) | |
493 | { | |
494 | modifying_ftrace_code++; | |
495 | ||
496 | if (command & FTRACE_UPDATE_CALLS) | |
497 | ftrace_replace_code(1); | |
498 | else if (command & FTRACE_DISABLE_CALLS) | |
499 | ftrace_replace_code(0); | |
500 | ||
501 | if (command & FTRACE_UPDATE_TRACE_FUNC) | |
502 | ftrace_update_ftrace_func(ftrace_trace_function); | |
503 | ||
504 | if (command & FTRACE_START_FUNC_RET) | |
505 | ftrace_enable_ftrace_graph_caller(); | |
506 | else if (command & FTRACE_STOP_FUNC_RET) | |
507 | ftrace_disable_ftrace_graph_caller(); | |
508 | ||
509 | modifying_ftrace_code--; | |
510 | } | |
511 | ||
d61f82d0 | 512 | int __init ftrace_dyn_arch_init(void *data) |
3d083395 | 513 | { |
732f3ca7 SR |
514 | /* The return code is retured via data */ |
515 | *(unsigned long *)data = 0; | |
dfa60aba | 516 | |
3d083395 SR |
517 | return 0; |
518 | } | |
caf4b323 | 519 | #endif |
e7d3737e | 520 | |
fb52607a | 521 | #ifdef CONFIG_FUNCTION_GRAPH_TRACER |
e7d3737e | 522 | |
5a45cfe1 SR |
523 | #ifdef CONFIG_DYNAMIC_FTRACE |
524 | extern void ftrace_graph_call(void); | |
525 | ||
526 | static int ftrace_mod_jmp(unsigned long ip, | |
527 | int old_offset, int new_offset) | |
528 | { | |
529 | unsigned char code[MCOUNT_INSN_SIZE]; | |
530 | ||
531 | if (probe_kernel_read(code, (void *)ip, MCOUNT_INSN_SIZE)) | |
532 | return -EFAULT; | |
533 | ||
534 | if (code[0] != 0xe9 || old_offset != *(int *)(&code[1])) | |
535 | return -EINVAL; | |
536 | ||
537 | *(int *)(&code[1]) = new_offset; | |
538 | ||
539 | if (do_ftrace_mod_code(ip, &code)) | |
540 | return -EPERM; | |
541 | ||
542 | return 0; | |
543 | } | |
544 | ||
545 | int ftrace_enable_ftrace_graph_caller(void) | |
546 | { | |
547 | unsigned long ip = (unsigned long)(&ftrace_graph_call); | |
548 | int old_offset, new_offset; | |
549 | ||
550 | old_offset = (unsigned long)(&ftrace_stub) - (ip + MCOUNT_INSN_SIZE); | |
551 | new_offset = (unsigned long)(&ftrace_graph_caller) - (ip + MCOUNT_INSN_SIZE); | |
552 | ||
553 | return ftrace_mod_jmp(ip, old_offset, new_offset); | |
554 | } | |
555 | ||
556 | int ftrace_disable_ftrace_graph_caller(void) | |
557 | { | |
558 | unsigned long ip = (unsigned long)(&ftrace_graph_call); | |
559 | int old_offset, new_offset; | |
560 | ||
561 | old_offset = (unsigned long)(&ftrace_graph_caller) - (ip + MCOUNT_INSN_SIZE); | |
562 | new_offset = (unsigned long)(&ftrace_stub) - (ip + MCOUNT_INSN_SIZE); | |
563 | ||
564 | return ftrace_mod_jmp(ip, old_offset, new_offset); | |
565 | } | |
566 | ||
e7d3737e FW |
567 | #endif /* !CONFIG_DYNAMIC_FTRACE */ |
568 | ||
e7d3737e FW |
569 | /* |
570 | * Hook the return address and push it in the stack of return addrs | |
571 | * in current thread info. | |
572 | */ | |
71e308a2 SR |
573 | void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr, |
574 | unsigned long frame_pointer) | |
e7d3737e FW |
575 | { |
576 | unsigned long old; | |
e7d3737e | 577 | int faulted; |
287b6e68 | 578 | struct ftrace_graph_ent trace; |
e7d3737e FW |
579 | unsigned long return_hooker = (unsigned long) |
580 | &return_to_handler; | |
581 | ||
380c4b14 | 582 | if (unlikely(atomic_read(¤t->tracing_graph_pause))) |
e7d3737e FW |
583 | return; |
584 | ||
585 | /* | |
586 | * Protect against fault, even if it shouldn't | |
587 | * happen. This tool is too much intrusive to | |
588 | * ignore such a protection. | |
589 | */ | |
590 | asm volatile( | |
96665788 SR |
591 | "1: " _ASM_MOV " (%[parent]), %[old]\n" |
592 | "2: " _ASM_MOV " %[return_hooker], (%[parent])\n" | |
e7d3737e | 593 | " movl $0, %[faulted]\n" |
e3944bfa | 594 | "3:\n" |
e7d3737e FW |
595 | |
596 | ".section .fixup, \"ax\"\n" | |
e3944bfa SR |
597 | "4: movl $1, %[faulted]\n" |
598 | " jmp 3b\n" | |
e7d3737e FW |
599 | ".previous\n" |
600 | ||
e3944bfa SR |
601 | _ASM_EXTABLE(1b, 4b) |
602 | _ASM_EXTABLE(2b, 4b) | |
e7d3737e | 603 | |
aa512a27 | 604 | : [old] "=&r" (old), [faulted] "=r" (faulted) |
96665788 | 605 | : [parent] "r" (parent), [return_hooker] "r" (return_hooker) |
e7d3737e FW |
606 | : "memory" |
607 | ); | |
608 | ||
14a866c5 SR |
609 | if (unlikely(faulted)) { |
610 | ftrace_graph_stop(); | |
611 | WARN_ON(1); | |
e7d3737e FW |
612 | return; |
613 | } | |
614 | ||
287b6e68 | 615 | trace.func = self_addr; |
722b3c74 | 616 | trace.depth = current->curr_ret_stack + 1; |
287b6e68 | 617 | |
e49dc19c SR |
618 | /* Only trace if the calling function expects to */ |
619 | if (!ftrace_graph_entry(&trace)) { | |
e49dc19c | 620 | *parent = old; |
722b3c74 SR |
621 | return; |
622 | } | |
623 | ||
624 | if (ftrace_push_return_trace(old, self_addr, &trace.depth, | |
625 | frame_pointer) == -EBUSY) { | |
626 | *parent = old; | |
627 | return; | |
e49dc19c | 628 | } |
e7d3737e | 629 | } |
fb52607a | 630 | #endif /* CONFIG_FUNCTION_GRAPH_TRACER */ |