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 |
8a4d0a68 | 103 | ftrace_modify_code_direct(unsigned long ip, unsigned const char *old_code, |
0d098a7d | 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 | ||
8a4d0a68 SR |
144 | /* |
145 | * On boot up, and when modules are loaded, the MCOUNT_ADDR | |
146 | * is converted to a nop, and will never become MCOUNT_ADDR | |
147 | * again. This code is either running before SMP (on boot up) | |
148 | * or before the code will ever be executed (module load). | |
149 | * We do not want to use the breakpoint version in this case, | |
150 | * just modify the code directly. | |
151 | */ | |
152 | if (addr == MCOUNT_ADDR) | |
153 | return ftrace_modify_code_direct(rec->ip, old, new); | |
154 | ||
155 | /* Normal cases use add_brk_on_nop */ | |
156 | WARN_ONCE(1, "invalid use of ftrace_make_nop"); | |
157 | return -EINVAL; | |
31e88909 SR |
158 | } |
159 | ||
160 | int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr) | |
161 | { | |
0d098a7d | 162 | unsigned const char *new, *old; |
31e88909 SR |
163 | unsigned long ip = rec->ip; |
164 | ||
165 | old = ftrace_nop_replace(); | |
166 | new = ftrace_call_replace(ip, addr); | |
167 | ||
8a4d0a68 SR |
168 | /* Should only be called when module is loaded */ |
169 | return ftrace_modify_code_direct(rec->ip, old, new); | |
d61f82d0 SR |
170 | } |
171 | ||
a192cd04 SR |
172 | /* |
173 | * The modifying_ftrace_code is used to tell the breakpoint | |
174 | * handler to call ftrace_int3_handler(). If it fails to | |
175 | * call this handler for a breakpoint added by ftrace, then | |
176 | * the kernel may crash. | |
177 | * | |
178 | * As atomic_writes on x86 do not need a barrier, we do not | |
179 | * need to add smp_mb()s for this to work. It is also considered | |
180 | * that we can not read the modifying_ftrace_code before | |
181 | * executing the breakpoint. That would be quite remarkable if | |
182 | * it could do that. Here's the flow that is required: | |
183 | * | |
184 | * CPU-0 CPU-1 | |
185 | * | |
186 | * atomic_inc(mfc); | |
187 | * write int3s | |
188 | * <trap-int3> // implicit (r)mb | |
189 | * if (atomic_read(mfc)) | |
190 | * call ftrace_int3_handler() | |
191 | * | |
192 | * Then when we are finished: | |
193 | * | |
194 | * atomic_dec(mfc); | |
195 | * | |
196 | * If we hit a breakpoint that was not set by ftrace, it does not | |
197 | * matter if ftrace_int3_handler() is called or not. It will | |
198 | * simply be ignored. But it is crucial that a ftrace nop/caller | |
199 | * breakpoint is handled. No other user should ever place a | |
200 | * breakpoint on an ftrace nop/caller location. It must only | |
201 | * be done by this code. | |
202 | */ | |
203 | atomic_t modifying_ftrace_code __read_mostly; | |
08d636b6 | 204 | |
8a4d0a68 SR |
205 | static int |
206 | ftrace_modify_code(unsigned long ip, unsigned const char *old_code, | |
207 | unsigned const char *new_code); | |
208 | ||
209 | int ftrace_update_ftrace_func(ftrace_func_t func) | |
210 | { | |
211 | unsigned long ip = (unsigned long)(&ftrace_call); | |
212 | unsigned char old[MCOUNT_INSN_SIZE], *new; | |
213 | int ret; | |
214 | ||
215 | memcpy(old, &ftrace_call, MCOUNT_INSN_SIZE); | |
216 | new = ftrace_call_replace(ip, (unsigned long)func); | |
217 | ||
218 | /* See comment above by declaration of modifying_ftrace_code */ | |
219 | atomic_inc(&modifying_ftrace_code); | |
220 | ||
221 | ret = ftrace_modify_code(ip, old, new); | |
222 | ||
223 | atomic_dec(&modifying_ftrace_code); | |
224 | ||
225 | return ret; | |
226 | } | |
227 | ||
08d636b6 SR |
228 | /* |
229 | * A breakpoint was added to the code address we are about to | |
230 | * modify, and this is the handle that will just skip over it. | |
231 | * We are either changing a nop into a trace call, or a trace | |
232 | * call to a nop. While the change is taking place, we treat | |
233 | * it just like it was a nop. | |
234 | */ | |
235 | int ftrace_int3_handler(struct pt_regs *regs) | |
236 | { | |
237 | if (WARN_ON_ONCE(!regs)) | |
238 | return 0; | |
239 | ||
240 | if (!ftrace_location(regs->ip - 1)) | |
241 | return 0; | |
242 | ||
243 | regs->ip += MCOUNT_INSN_SIZE - 1; | |
244 | ||
245 | return 1; | |
246 | } | |
247 | ||
248 | static int ftrace_write(unsigned long ip, const char *val, int size) | |
249 | { | |
250 | /* | |
251 | * On x86_64, kernel text mappings are mapped read-only with | |
252 | * CONFIG_DEBUG_RODATA. So we use the kernel identity mapping instead | |
253 | * of the kernel text mapping to modify the kernel text. | |
254 | * | |
255 | * For 32bit kernels, these mappings are same and we can use | |
256 | * kernel identity mapping to modify code. | |
257 | */ | |
258 | if (within(ip, (unsigned long)_text, (unsigned long)_etext)) | |
259 | ip = (unsigned long)__va(__pa(ip)); | |
260 | ||
261 | return probe_kernel_write((void *)ip, val, size); | |
262 | } | |
263 | ||
264 | static int add_break(unsigned long ip, const char *old) | |
265 | { | |
266 | unsigned char replaced[MCOUNT_INSN_SIZE]; | |
267 | unsigned char brk = BREAKPOINT_INSTRUCTION; | |
268 | ||
269 | if (probe_kernel_read(replaced, (void *)ip, MCOUNT_INSN_SIZE)) | |
270 | return -EFAULT; | |
271 | ||
272 | /* Make sure it is what we expect it to be */ | |
273 | if (memcmp(replaced, old, MCOUNT_INSN_SIZE) != 0) | |
274 | return -EINVAL; | |
275 | ||
276 | if (ftrace_write(ip, &brk, 1)) | |
277 | return -EPERM; | |
278 | ||
279 | return 0; | |
280 | } | |
281 | ||
282 | static int add_brk_on_call(struct dyn_ftrace *rec, unsigned long addr) | |
283 | { | |
284 | unsigned const char *old; | |
285 | unsigned long ip = rec->ip; | |
286 | ||
287 | old = ftrace_call_replace(ip, addr); | |
288 | ||
289 | return add_break(rec->ip, old); | |
290 | } | |
291 | ||
292 | ||
293 | static int add_brk_on_nop(struct dyn_ftrace *rec) | |
294 | { | |
295 | unsigned const char *old; | |
296 | ||
297 | old = ftrace_nop_replace(); | |
298 | ||
299 | return add_break(rec->ip, old); | |
300 | } | |
301 | ||
302 | static int add_breakpoints(struct dyn_ftrace *rec, int enable) | |
303 | { | |
304 | unsigned long ftrace_addr; | |
305 | int ret; | |
306 | ||
307 | ret = ftrace_test_record(rec, enable); | |
308 | ||
309 | ftrace_addr = (unsigned long)FTRACE_ADDR; | |
310 | ||
311 | switch (ret) { | |
312 | case FTRACE_UPDATE_IGNORE: | |
313 | return 0; | |
314 | ||
315 | case FTRACE_UPDATE_MAKE_CALL: | |
316 | /* converting nop to call */ | |
317 | return add_brk_on_nop(rec); | |
318 | ||
319 | case FTRACE_UPDATE_MAKE_NOP: | |
320 | /* converting a call to a nop */ | |
321 | return add_brk_on_call(rec, ftrace_addr); | |
322 | } | |
323 | return 0; | |
324 | } | |
325 | ||
326 | /* | |
327 | * On error, we need to remove breakpoints. This needs to | |
328 | * be done caefully. If the address does not currently have a | |
329 | * breakpoint, we know we are done. Otherwise, we look at the | |
330 | * remaining 4 bytes of the instruction. If it matches a nop | |
331 | * we replace the breakpoint with the nop. Otherwise we replace | |
332 | * it with the call instruction. | |
333 | */ | |
334 | static int remove_breakpoint(struct dyn_ftrace *rec) | |
335 | { | |
336 | unsigned char ins[MCOUNT_INSN_SIZE]; | |
337 | unsigned char brk = BREAKPOINT_INSTRUCTION; | |
338 | const unsigned char *nop; | |
339 | unsigned long ftrace_addr; | |
340 | unsigned long ip = rec->ip; | |
341 | ||
342 | /* If we fail the read, just give up */ | |
343 | if (probe_kernel_read(ins, (void *)ip, MCOUNT_INSN_SIZE)) | |
344 | return -EFAULT; | |
345 | ||
346 | /* If this does not have a breakpoint, we are done */ | |
347 | if (ins[0] != brk) | |
348 | return -1; | |
349 | ||
350 | nop = ftrace_nop_replace(); | |
351 | ||
352 | /* | |
353 | * If the last 4 bytes of the instruction do not match | |
354 | * a nop, then we assume that this is a call to ftrace_addr. | |
355 | */ | |
356 | if (memcmp(&ins[1], &nop[1], MCOUNT_INSN_SIZE - 1) != 0) { | |
357 | /* | |
358 | * For extra paranoidism, we check if the breakpoint is on | |
359 | * a call that would actually jump to the ftrace_addr. | |
360 | * If not, don't touch the breakpoint, we make just create | |
361 | * a disaster. | |
362 | */ | |
363 | ftrace_addr = (unsigned long)FTRACE_ADDR; | |
364 | nop = ftrace_call_replace(ip, ftrace_addr); | |
365 | ||
366 | if (memcmp(&ins[1], &nop[1], MCOUNT_INSN_SIZE - 1) != 0) | |
367 | return -EINVAL; | |
368 | } | |
369 | ||
370 | return probe_kernel_write((void *)ip, &nop[0], 1); | |
371 | } | |
372 | ||
373 | static int add_update_code(unsigned long ip, unsigned const char *new) | |
374 | { | |
375 | /* skip breakpoint */ | |
376 | ip++; | |
377 | new++; | |
378 | if (ftrace_write(ip, new, MCOUNT_INSN_SIZE - 1)) | |
379 | return -EPERM; | |
380 | return 0; | |
381 | } | |
382 | ||
383 | static int add_update_call(struct dyn_ftrace *rec, unsigned long addr) | |
384 | { | |
385 | unsigned long ip = rec->ip; | |
386 | unsigned const char *new; | |
387 | ||
388 | new = ftrace_call_replace(ip, addr); | |
389 | return add_update_code(ip, new); | |
390 | } | |
391 | ||
392 | static int add_update_nop(struct dyn_ftrace *rec) | |
393 | { | |
394 | unsigned long ip = rec->ip; | |
395 | unsigned const char *new; | |
396 | ||
397 | new = ftrace_nop_replace(); | |
398 | return add_update_code(ip, new); | |
399 | } | |
400 | ||
401 | static int add_update(struct dyn_ftrace *rec, int enable) | |
402 | { | |
403 | unsigned long ftrace_addr; | |
404 | int ret; | |
405 | ||
406 | ret = ftrace_test_record(rec, enable); | |
407 | ||
408 | ftrace_addr = (unsigned long)FTRACE_ADDR; | |
409 | ||
410 | switch (ret) { | |
411 | case FTRACE_UPDATE_IGNORE: | |
412 | return 0; | |
413 | ||
414 | case FTRACE_UPDATE_MAKE_CALL: | |
415 | /* converting nop to call */ | |
416 | return add_update_call(rec, ftrace_addr); | |
417 | ||
418 | case FTRACE_UPDATE_MAKE_NOP: | |
419 | /* converting a call to a nop */ | |
420 | return add_update_nop(rec); | |
421 | } | |
422 | ||
423 | return 0; | |
424 | } | |
425 | ||
426 | static int finish_update_call(struct dyn_ftrace *rec, unsigned long addr) | |
427 | { | |
428 | unsigned long ip = rec->ip; | |
429 | unsigned const char *new; | |
430 | ||
431 | new = ftrace_call_replace(ip, addr); | |
432 | ||
433 | if (ftrace_write(ip, new, 1)) | |
434 | return -EPERM; | |
435 | ||
436 | return 0; | |
437 | } | |
438 | ||
439 | static int finish_update_nop(struct dyn_ftrace *rec) | |
440 | { | |
441 | unsigned long ip = rec->ip; | |
442 | unsigned const char *new; | |
443 | ||
444 | new = ftrace_nop_replace(); | |
445 | ||
446 | if (ftrace_write(ip, new, 1)) | |
447 | return -EPERM; | |
448 | return 0; | |
449 | } | |
450 | ||
451 | static int finish_update(struct dyn_ftrace *rec, int enable) | |
452 | { | |
453 | unsigned long ftrace_addr; | |
454 | int ret; | |
455 | ||
456 | ret = ftrace_update_record(rec, enable); | |
457 | ||
458 | ftrace_addr = (unsigned long)FTRACE_ADDR; | |
459 | ||
460 | switch (ret) { | |
461 | case FTRACE_UPDATE_IGNORE: | |
462 | return 0; | |
463 | ||
464 | case FTRACE_UPDATE_MAKE_CALL: | |
465 | /* converting nop to call */ | |
466 | return finish_update_call(rec, ftrace_addr); | |
467 | ||
468 | case FTRACE_UPDATE_MAKE_NOP: | |
469 | /* converting a call to a nop */ | |
470 | return finish_update_nop(rec); | |
471 | } | |
472 | ||
473 | return 0; | |
474 | } | |
475 | ||
476 | static void do_sync_core(void *data) | |
477 | { | |
478 | sync_core(); | |
479 | } | |
480 | ||
481 | static void run_sync(void) | |
482 | { | |
483 | int enable_irqs = irqs_disabled(); | |
484 | ||
485 | /* We may be called with interrupts disbled (on bootup). */ | |
486 | if (enable_irqs) | |
487 | local_irq_enable(); | |
488 | on_each_cpu(do_sync_core, NULL, 1); | |
489 | if (enable_irqs) | |
490 | local_irq_disable(); | |
491 | } | |
492 | ||
e4f5d544 | 493 | void ftrace_replace_code(int enable) |
08d636b6 SR |
494 | { |
495 | struct ftrace_rec_iter *iter; | |
496 | struct dyn_ftrace *rec; | |
497 | const char *report = "adding breakpoints"; | |
498 | int count = 0; | |
499 | int ret; | |
500 | ||
501 | for_ftrace_rec_iter(iter) { | |
502 | rec = ftrace_rec_iter_record(iter); | |
503 | ||
504 | ret = add_breakpoints(rec, enable); | |
505 | if (ret) | |
506 | goto remove_breakpoints; | |
507 | count++; | |
508 | } | |
509 | ||
510 | run_sync(); | |
511 | ||
512 | report = "updating code"; | |
513 | ||
514 | for_ftrace_rec_iter(iter) { | |
515 | rec = ftrace_rec_iter_record(iter); | |
516 | ||
517 | ret = add_update(rec, enable); | |
518 | if (ret) | |
519 | goto remove_breakpoints; | |
520 | } | |
521 | ||
522 | run_sync(); | |
523 | ||
524 | report = "removing breakpoints"; | |
525 | ||
526 | for_ftrace_rec_iter(iter) { | |
527 | rec = ftrace_rec_iter_record(iter); | |
528 | ||
529 | ret = finish_update(rec, enable); | |
530 | if (ret) | |
531 | goto remove_breakpoints; | |
532 | } | |
533 | ||
534 | run_sync(); | |
535 | ||
536 | return; | |
537 | ||
538 | remove_breakpoints: | |
539 | ftrace_bug(ret, rec ? rec->ip : 0); | |
540 | printk(KERN_WARNING "Failed on %s (%d):\n", report, count); | |
541 | for_ftrace_rec_iter(iter) { | |
542 | rec = ftrace_rec_iter_record(iter); | |
543 | remove_breakpoint(rec); | |
544 | } | |
545 | } | |
546 | ||
8a4d0a68 SR |
547 | static int |
548 | ftrace_modify_code(unsigned long ip, unsigned const char *old_code, | |
549 | unsigned const char *new_code) | |
550 | { | |
551 | int ret; | |
552 | ||
553 | ret = add_break(ip, old_code); | |
554 | if (ret) | |
555 | goto out; | |
556 | ||
557 | run_sync(); | |
558 | ||
559 | ret = add_update_code(ip, new_code); | |
560 | if (ret) | |
561 | goto fail_update; | |
562 | ||
563 | run_sync(); | |
564 | ||
565 | ret = ftrace_write(ip, new_code, 1); | |
566 | if (ret) { | |
567 | ret = -EPERM; | |
568 | goto out; | |
569 | } | |
570 | run_sync(); | |
571 | out: | |
572 | return ret; | |
573 | ||
574 | fail_update: | |
575 | probe_kernel_write((void *)ip, &old_code[0], 1); | |
576 | goto out; | |
577 | } | |
578 | ||
08d636b6 SR |
579 | void arch_ftrace_update_code(int command) |
580 | { | |
a192cd04 SR |
581 | /* See comment above by declaration of modifying_ftrace_code */ |
582 | atomic_inc(&modifying_ftrace_code); | |
08d636b6 | 583 | |
e4f5d544 | 584 | ftrace_modify_all_code(command); |
08d636b6 | 585 | |
a192cd04 | 586 | atomic_dec(&modifying_ftrace_code); |
08d636b6 SR |
587 | } |
588 | ||
d61f82d0 | 589 | int __init ftrace_dyn_arch_init(void *data) |
3d083395 | 590 | { |
732f3ca7 SR |
591 | /* The return code is retured via data */ |
592 | *(unsigned long *)data = 0; | |
dfa60aba | 593 | |
3d083395 SR |
594 | return 0; |
595 | } | |
caf4b323 | 596 | #endif |
e7d3737e | 597 | |
fb52607a | 598 | #ifdef CONFIG_FUNCTION_GRAPH_TRACER |
e7d3737e | 599 | |
5a45cfe1 SR |
600 | #ifdef CONFIG_DYNAMIC_FTRACE |
601 | extern void ftrace_graph_call(void); | |
602 | ||
603 | static int ftrace_mod_jmp(unsigned long ip, | |
604 | int old_offset, int new_offset) | |
605 | { | |
606 | unsigned char code[MCOUNT_INSN_SIZE]; | |
607 | ||
608 | if (probe_kernel_read(code, (void *)ip, MCOUNT_INSN_SIZE)) | |
609 | return -EFAULT; | |
610 | ||
611 | if (code[0] != 0xe9 || old_offset != *(int *)(&code[1])) | |
612 | return -EINVAL; | |
613 | ||
614 | *(int *)(&code[1]) = new_offset; | |
615 | ||
616 | if (do_ftrace_mod_code(ip, &code)) | |
617 | return -EPERM; | |
618 | ||
619 | return 0; | |
620 | } | |
621 | ||
622 | int ftrace_enable_ftrace_graph_caller(void) | |
623 | { | |
624 | unsigned long ip = (unsigned long)(&ftrace_graph_call); | |
625 | int old_offset, new_offset; | |
626 | ||
627 | old_offset = (unsigned long)(&ftrace_stub) - (ip + MCOUNT_INSN_SIZE); | |
628 | new_offset = (unsigned long)(&ftrace_graph_caller) - (ip + MCOUNT_INSN_SIZE); | |
629 | ||
630 | return ftrace_mod_jmp(ip, old_offset, new_offset); | |
631 | } | |
632 | ||
633 | int ftrace_disable_ftrace_graph_caller(void) | |
634 | { | |
635 | unsigned long ip = (unsigned long)(&ftrace_graph_call); | |
636 | int old_offset, new_offset; | |
637 | ||
638 | old_offset = (unsigned long)(&ftrace_graph_caller) - (ip + MCOUNT_INSN_SIZE); | |
639 | new_offset = (unsigned long)(&ftrace_stub) - (ip + MCOUNT_INSN_SIZE); | |
640 | ||
641 | return ftrace_mod_jmp(ip, old_offset, new_offset); | |
642 | } | |
643 | ||
e7d3737e FW |
644 | #endif /* !CONFIG_DYNAMIC_FTRACE */ |
645 | ||
e7d3737e FW |
646 | /* |
647 | * Hook the return address and push it in the stack of return addrs | |
648 | * in current thread info. | |
649 | */ | |
71e308a2 SR |
650 | void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr, |
651 | unsigned long frame_pointer) | |
e7d3737e FW |
652 | { |
653 | unsigned long old; | |
e7d3737e | 654 | int faulted; |
287b6e68 | 655 | struct ftrace_graph_ent trace; |
e7d3737e FW |
656 | unsigned long return_hooker = (unsigned long) |
657 | &return_to_handler; | |
658 | ||
380c4b14 | 659 | if (unlikely(atomic_read(¤t->tracing_graph_pause))) |
e7d3737e FW |
660 | return; |
661 | ||
662 | /* | |
663 | * Protect against fault, even if it shouldn't | |
664 | * happen. This tool is too much intrusive to | |
665 | * ignore such a protection. | |
666 | */ | |
667 | asm volatile( | |
96665788 SR |
668 | "1: " _ASM_MOV " (%[parent]), %[old]\n" |
669 | "2: " _ASM_MOV " %[return_hooker], (%[parent])\n" | |
e7d3737e | 670 | " movl $0, %[faulted]\n" |
e3944bfa | 671 | "3:\n" |
e7d3737e FW |
672 | |
673 | ".section .fixup, \"ax\"\n" | |
e3944bfa SR |
674 | "4: movl $1, %[faulted]\n" |
675 | " jmp 3b\n" | |
e7d3737e FW |
676 | ".previous\n" |
677 | ||
e3944bfa SR |
678 | _ASM_EXTABLE(1b, 4b) |
679 | _ASM_EXTABLE(2b, 4b) | |
e7d3737e | 680 | |
aa512a27 | 681 | : [old] "=&r" (old), [faulted] "=r" (faulted) |
96665788 | 682 | : [parent] "r" (parent), [return_hooker] "r" (return_hooker) |
e7d3737e FW |
683 | : "memory" |
684 | ); | |
685 | ||
14a866c5 SR |
686 | if (unlikely(faulted)) { |
687 | ftrace_graph_stop(); | |
688 | WARN_ON(1); | |
e7d3737e FW |
689 | return; |
690 | } | |
691 | ||
287b6e68 | 692 | trace.func = self_addr; |
722b3c74 | 693 | trace.depth = current->curr_ret_stack + 1; |
287b6e68 | 694 | |
e49dc19c SR |
695 | /* Only trace if the calling function expects to */ |
696 | if (!ftrace_graph_entry(&trace)) { | |
e49dc19c | 697 | *parent = old; |
722b3c74 SR |
698 | return; |
699 | } | |
700 | ||
701 | if (ftrace_push_return_trace(old, self_addr, &trace.depth, | |
702 | frame_pointer) == -EBUSY) { | |
703 | *parent = old; | |
704 | return; | |
e49dc19c | 705 | } |
e7d3737e | 706 | } |
fb52607a | 707 | #endif /* CONFIG_FUNCTION_GRAPH_TRACER */ |