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1 | /** | |
2 | * @file buffer_sync.c | |
3 | * | |
4 | * @remark Copyright 2002-2009 OProfile authors | |
5 | * @remark Read the file COPYING | |
6 | * | |
7 | * @author John Levon <levon@movementarian.org> | |
8 | * @author Barry Kasindorf | |
9 | * @author Robert Richter <robert.richter@amd.com> | |
10 | * | |
11 | * This is the core of the buffer management. Each | |
12 | * CPU buffer is processed and entered into the | |
13 | * global event buffer. Such processing is necessary | |
14 | * in several circumstances, mentioned below. | |
15 | * | |
16 | * The processing does the job of converting the | |
17 | * transitory EIP value into a persistent dentry/offset | |
18 | * value that the profiler can record at its leisure. | |
19 | * | |
20 | * See fs/dcookies.c for a description of the dentry/offset | |
21 | * objects. | |
22 | */ | |
23 | ||
24 | #include <linux/file.h> | |
25 | #include <linux/mm.h> | |
26 | #include <linux/workqueue.h> | |
27 | #include <linux/notifier.h> | |
28 | #include <linux/dcookies.h> | |
29 | #include <linux/profile.h> | |
30 | #include <linux/module.h> | |
31 | #include <linux/fs.h> | |
32 | #include <linux/oprofile.h> | |
33 | #include <linux/sched.h> | |
34 | #include <linux/gfp.h> | |
35 | ||
36 | #include "oprofile_stats.h" | |
37 | #include "event_buffer.h" | |
38 | #include "cpu_buffer.h" | |
39 | #include "buffer_sync.h" | |
40 | ||
41 | static LIST_HEAD(dying_tasks); | |
42 | static LIST_HEAD(dead_tasks); | |
43 | static cpumask_var_t marked_cpus; | |
44 | static DEFINE_SPINLOCK(task_mortuary); | |
45 | static void process_task_mortuary(void); | |
46 | ||
47 | /* Take ownership of the task struct and place it on the | |
48 | * list for processing. Only after two full buffer syncs | |
49 | * does the task eventually get freed, because by then | |
50 | * we are sure we will not reference it again. | |
51 | * Can be invoked from softirq via RCU callback due to | |
52 | * call_rcu() of the task struct, hence the _irqsave. | |
53 | */ | |
54 | static int | |
55 | task_free_notify(struct notifier_block *self, unsigned long val, void *data) | |
56 | { | |
57 | unsigned long flags; | |
58 | struct task_struct *task = data; | |
59 | spin_lock_irqsave(&task_mortuary, flags); | |
60 | list_add(&task->tasks, &dying_tasks); | |
61 | spin_unlock_irqrestore(&task_mortuary, flags); | |
62 | return NOTIFY_OK; | |
63 | } | |
64 | ||
65 | ||
66 | /* The task is on its way out. A sync of the buffer means we can catch | |
67 | * any remaining samples for this task. | |
68 | */ | |
69 | static int | |
70 | task_exit_notify(struct notifier_block *self, unsigned long val, void *data) | |
71 | { | |
72 | /* To avoid latency problems, we only process the current CPU, | |
73 | * hoping that most samples for the task are on this CPU | |
74 | */ | |
75 | sync_buffer(raw_smp_processor_id()); | |
76 | return 0; | |
77 | } | |
78 | ||
79 | ||
80 | /* The task is about to try a do_munmap(). We peek at what it's going to | |
81 | * do, and if it's an executable region, process the samples first, so | |
82 | * we don't lose any. This does not have to be exact, it's a QoI issue | |
83 | * only. | |
84 | */ | |
85 | static int | |
86 | munmap_notify(struct notifier_block *self, unsigned long val, void *data) | |
87 | { | |
88 | unsigned long addr = (unsigned long)data; | |
89 | struct mm_struct *mm = current->mm; | |
90 | struct vm_area_struct *mpnt; | |
91 | ||
92 | down_read(&mm->mmap_sem); | |
93 | ||
94 | mpnt = find_vma(mm, addr); | |
95 | if (mpnt && mpnt->vm_file && (mpnt->vm_flags & VM_EXEC)) { | |
96 | up_read(&mm->mmap_sem); | |
97 | /* To avoid latency problems, we only process the current CPU, | |
98 | * hoping that most samples for the task are on this CPU | |
99 | */ | |
100 | sync_buffer(raw_smp_processor_id()); | |
101 | return 0; | |
102 | } | |
103 | ||
104 | up_read(&mm->mmap_sem); | |
105 | return 0; | |
106 | } | |
107 | ||
108 | ||
109 | /* We need to be told about new modules so we don't attribute to a previously | |
110 | * loaded module, or drop the samples on the floor. | |
111 | */ | |
112 | static int | |
113 | module_load_notify(struct notifier_block *self, unsigned long val, void *data) | |
114 | { | |
115 | #ifdef CONFIG_MODULES | |
116 | if (val != MODULE_STATE_COMING) | |
117 | return 0; | |
118 | ||
119 | /* FIXME: should we process all CPU buffers ? */ | |
120 | mutex_lock(&buffer_mutex); | |
121 | add_event_entry(ESCAPE_CODE); | |
122 | add_event_entry(MODULE_LOADED_CODE); | |
123 | mutex_unlock(&buffer_mutex); | |
124 | #endif | |
125 | return 0; | |
126 | } | |
127 | ||
128 | ||
129 | static struct notifier_block task_free_nb = { | |
130 | .notifier_call = task_free_notify, | |
131 | }; | |
132 | ||
133 | static struct notifier_block task_exit_nb = { | |
134 | .notifier_call = task_exit_notify, | |
135 | }; | |
136 | ||
137 | static struct notifier_block munmap_nb = { | |
138 | .notifier_call = munmap_notify, | |
139 | }; | |
140 | ||
141 | static struct notifier_block module_load_nb = { | |
142 | .notifier_call = module_load_notify, | |
143 | }; | |
144 | ||
145 | static void free_all_tasks(void) | |
146 | { | |
147 | /* make sure we don't leak task structs */ | |
148 | process_task_mortuary(); | |
149 | process_task_mortuary(); | |
150 | } | |
151 | ||
152 | int sync_start(void) | |
153 | { | |
154 | int err; | |
155 | ||
156 | if (!zalloc_cpumask_var(&marked_cpus, GFP_KERNEL)) | |
157 | return -ENOMEM; | |
158 | ||
159 | err = task_handoff_register(&task_free_nb); | |
160 | if (err) | |
161 | goto out1; | |
162 | err = profile_event_register(PROFILE_TASK_EXIT, &task_exit_nb); | |
163 | if (err) | |
164 | goto out2; | |
165 | err = profile_event_register(PROFILE_MUNMAP, &munmap_nb); | |
166 | if (err) | |
167 | goto out3; | |
168 | err = register_module_notifier(&module_load_nb); | |
169 | if (err) | |
170 | goto out4; | |
171 | ||
172 | start_cpu_work(); | |
173 | ||
174 | out: | |
175 | return err; | |
176 | out4: | |
177 | profile_event_unregister(PROFILE_MUNMAP, &munmap_nb); | |
178 | out3: | |
179 | profile_event_unregister(PROFILE_TASK_EXIT, &task_exit_nb); | |
180 | out2: | |
181 | task_handoff_unregister(&task_free_nb); | |
182 | free_all_tasks(); | |
183 | out1: | |
184 | free_cpumask_var(marked_cpus); | |
185 | goto out; | |
186 | } | |
187 | ||
188 | ||
189 | void sync_stop(void) | |
190 | { | |
191 | end_cpu_work(); | |
192 | unregister_module_notifier(&module_load_nb); | |
193 | profile_event_unregister(PROFILE_MUNMAP, &munmap_nb); | |
194 | profile_event_unregister(PROFILE_TASK_EXIT, &task_exit_nb); | |
195 | task_handoff_unregister(&task_free_nb); | |
196 | barrier(); /* do all of the above first */ | |
197 | ||
198 | flush_cpu_work(); | |
199 | ||
200 | free_all_tasks(); | |
201 | free_cpumask_var(marked_cpus); | |
202 | } | |
203 | ||
204 | ||
205 | /* Optimisation. We can manage without taking the dcookie sem | |
206 | * because we cannot reach this code without at least one | |
207 | * dcookie user still being registered (namely, the reader | |
208 | * of the event buffer). */ | |
209 | static inline unsigned long fast_get_dcookie(const struct path *path) | |
210 | { | |
211 | unsigned long cookie; | |
212 | ||
213 | if (path->dentry->d_flags & DCACHE_COOKIE) | |
214 | return (unsigned long)path->dentry; | |
215 | get_dcookie(path, &cookie); | |
216 | return cookie; | |
217 | } | |
218 | ||
219 | ||
220 | /* Look up the dcookie for the task's mm->exe_file, | |
221 | * which corresponds loosely to "application name". This is | |
222 | * not strictly necessary but allows oprofile to associate | |
223 | * shared-library samples with particular applications | |
224 | */ | |
225 | static unsigned long get_exec_dcookie(struct mm_struct *mm) | |
226 | { | |
227 | unsigned long cookie = NO_COOKIE; | |
228 | struct file *exe_file; | |
229 | ||
230 | if (!mm) | |
231 | goto done; | |
232 | ||
233 | exe_file = get_mm_exe_file(mm); | |
234 | if (!exe_file) | |
235 | goto done; | |
236 | ||
237 | cookie = fast_get_dcookie(&exe_file->f_path); | |
238 | fput(exe_file); | |
239 | done: | |
240 | return cookie; | |
241 | } | |
242 | ||
243 | ||
244 | /* Convert the EIP value of a sample into a persistent dentry/offset | |
245 | * pair that can then be added to the global event buffer. We make | |
246 | * sure to do this lookup before a mm->mmap modification happens so | |
247 | * we don't lose track. | |
248 | * | |
249 | * The caller must ensure the mm is not nil (ie: not a kernel thread). | |
250 | */ | |
251 | static unsigned long | |
252 | lookup_dcookie(struct mm_struct *mm, unsigned long addr, off_t *offset) | |
253 | { | |
254 | unsigned long cookie = NO_COOKIE; | |
255 | struct vm_area_struct *vma; | |
256 | ||
257 | down_read(&mm->mmap_sem); | |
258 | for (vma = find_vma(mm, addr); vma; vma = vma->vm_next) { | |
259 | ||
260 | if (addr < vma->vm_start || addr >= vma->vm_end) | |
261 | continue; | |
262 | ||
263 | if (vma->vm_file) { | |
264 | cookie = fast_get_dcookie(&vma->vm_file->f_path); | |
265 | *offset = (vma->vm_pgoff << PAGE_SHIFT) + addr - | |
266 | vma->vm_start; | |
267 | } else { | |
268 | /* must be an anonymous map */ | |
269 | *offset = addr; | |
270 | } | |
271 | ||
272 | break; | |
273 | } | |
274 | ||
275 | if (!vma) | |
276 | cookie = INVALID_COOKIE; | |
277 | up_read(&mm->mmap_sem); | |
278 | ||
279 | return cookie; | |
280 | } | |
281 | ||
282 | static unsigned long last_cookie = INVALID_COOKIE; | |
283 | ||
284 | static void add_cpu_switch(int i) | |
285 | { | |
286 | add_event_entry(ESCAPE_CODE); | |
287 | add_event_entry(CPU_SWITCH_CODE); | |
288 | add_event_entry(i); | |
289 | last_cookie = INVALID_COOKIE; | |
290 | } | |
291 | ||
292 | static void add_kernel_ctx_switch(unsigned int in_kernel) | |
293 | { | |
294 | add_event_entry(ESCAPE_CODE); | |
295 | if (in_kernel) | |
296 | add_event_entry(KERNEL_ENTER_SWITCH_CODE); | |
297 | else | |
298 | add_event_entry(KERNEL_EXIT_SWITCH_CODE); | |
299 | } | |
300 | ||
301 | static void | |
302 | add_user_ctx_switch(struct task_struct const *task, unsigned long cookie) | |
303 | { | |
304 | add_event_entry(ESCAPE_CODE); | |
305 | add_event_entry(CTX_SWITCH_CODE); | |
306 | add_event_entry(task->pid); | |
307 | add_event_entry(cookie); | |
308 | /* Another code for daemon back-compat */ | |
309 | add_event_entry(ESCAPE_CODE); | |
310 | add_event_entry(CTX_TGID_CODE); | |
311 | add_event_entry(task->tgid); | |
312 | } | |
313 | ||
314 | ||
315 | static void add_cookie_switch(unsigned long cookie) | |
316 | { | |
317 | add_event_entry(ESCAPE_CODE); | |
318 | add_event_entry(COOKIE_SWITCH_CODE); | |
319 | add_event_entry(cookie); | |
320 | } | |
321 | ||
322 | ||
323 | static void add_trace_begin(void) | |
324 | { | |
325 | add_event_entry(ESCAPE_CODE); | |
326 | add_event_entry(TRACE_BEGIN_CODE); | |
327 | } | |
328 | ||
329 | static void add_data(struct op_entry *entry, struct mm_struct *mm) | |
330 | { | |
331 | unsigned long code, pc, val; | |
332 | unsigned long cookie; | |
333 | off_t offset; | |
334 | ||
335 | if (!op_cpu_buffer_get_data(entry, &code)) | |
336 | return; | |
337 | if (!op_cpu_buffer_get_data(entry, &pc)) | |
338 | return; | |
339 | if (!op_cpu_buffer_get_size(entry)) | |
340 | return; | |
341 | ||
342 | if (mm) { | |
343 | cookie = lookup_dcookie(mm, pc, &offset); | |
344 | ||
345 | if (cookie == NO_COOKIE) | |
346 | offset = pc; | |
347 | if (cookie == INVALID_COOKIE) { | |
348 | atomic_inc(&oprofile_stats.sample_lost_no_mapping); | |
349 | offset = pc; | |
350 | } | |
351 | if (cookie != last_cookie) { | |
352 | add_cookie_switch(cookie); | |
353 | last_cookie = cookie; | |
354 | } | |
355 | } else | |
356 | offset = pc; | |
357 | ||
358 | add_event_entry(ESCAPE_CODE); | |
359 | add_event_entry(code); | |
360 | add_event_entry(offset); /* Offset from Dcookie */ | |
361 | ||
362 | while (op_cpu_buffer_get_data(entry, &val)) | |
363 | add_event_entry(val); | |
364 | } | |
365 | ||
366 | static inline void add_sample_entry(unsigned long offset, unsigned long event) | |
367 | { | |
368 | add_event_entry(offset); | |
369 | add_event_entry(event); | |
370 | } | |
371 | ||
372 | ||
373 | /* | |
374 | * Add a sample to the global event buffer. If possible the | |
375 | * sample is converted into a persistent dentry/offset pair | |
376 | * for later lookup from userspace. Return 0 on failure. | |
377 | */ | |
378 | static int | |
379 | add_sample(struct mm_struct *mm, struct op_sample *s, int in_kernel) | |
380 | { | |
381 | unsigned long cookie; | |
382 | off_t offset; | |
383 | ||
384 | if (in_kernel) { | |
385 | add_sample_entry(s->eip, s->event); | |
386 | return 1; | |
387 | } | |
388 | ||
389 | /* add userspace sample */ | |
390 | ||
391 | if (!mm) { | |
392 | atomic_inc(&oprofile_stats.sample_lost_no_mm); | |
393 | return 0; | |
394 | } | |
395 | ||
396 | cookie = lookup_dcookie(mm, s->eip, &offset); | |
397 | ||
398 | if (cookie == INVALID_COOKIE) { | |
399 | atomic_inc(&oprofile_stats.sample_lost_no_mapping); | |
400 | return 0; | |
401 | } | |
402 | ||
403 | if (cookie != last_cookie) { | |
404 | add_cookie_switch(cookie); | |
405 | last_cookie = cookie; | |
406 | } | |
407 | ||
408 | add_sample_entry(offset, s->event); | |
409 | ||
410 | return 1; | |
411 | } | |
412 | ||
413 | ||
414 | static void release_mm(struct mm_struct *mm) | |
415 | { | |
416 | if (!mm) | |
417 | return; | |
418 | mmput(mm); | |
419 | } | |
420 | ||
421 | static inline int is_code(unsigned long val) | |
422 | { | |
423 | return val == ESCAPE_CODE; | |
424 | } | |
425 | ||
426 | ||
427 | /* Move tasks along towards death. Any tasks on dead_tasks | |
428 | * will definitely have no remaining references in any | |
429 | * CPU buffers at this point, because we use two lists, | |
430 | * and to have reached the list, it must have gone through | |
431 | * one full sync already. | |
432 | */ | |
433 | static void process_task_mortuary(void) | |
434 | { | |
435 | unsigned long flags; | |
436 | LIST_HEAD(local_dead_tasks); | |
437 | struct task_struct *task; | |
438 | struct task_struct *ttask; | |
439 | ||
440 | spin_lock_irqsave(&task_mortuary, flags); | |
441 | ||
442 | list_splice_init(&dead_tasks, &local_dead_tasks); | |
443 | list_splice_init(&dying_tasks, &dead_tasks); | |
444 | ||
445 | spin_unlock_irqrestore(&task_mortuary, flags); | |
446 | ||
447 | list_for_each_entry_safe(task, ttask, &local_dead_tasks, tasks) { | |
448 | list_del(&task->tasks); | |
449 | free_task(task); | |
450 | } | |
451 | } | |
452 | ||
453 | ||
454 | static void mark_done(int cpu) | |
455 | { | |
456 | int i; | |
457 | ||
458 | cpumask_set_cpu(cpu, marked_cpus); | |
459 | ||
460 | for_each_online_cpu(i) { | |
461 | if (!cpumask_test_cpu(i, marked_cpus)) | |
462 | return; | |
463 | } | |
464 | ||
465 | /* All CPUs have been processed at least once, | |
466 | * we can process the mortuary once | |
467 | */ | |
468 | process_task_mortuary(); | |
469 | ||
470 | cpumask_clear(marked_cpus); | |
471 | } | |
472 | ||
473 | ||
474 | /* FIXME: this is not sufficient if we implement syscall barrier backtrace | |
475 | * traversal, the code switch to sb_sample_start at first kernel enter/exit | |
476 | * switch so we need a fifth state and some special handling in sync_buffer() | |
477 | */ | |
478 | typedef enum { | |
479 | sb_bt_ignore = -2, | |
480 | sb_buffer_start, | |
481 | sb_bt_start, | |
482 | sb_sample_start, | |
483 | } sync_buffer_state; | |
484 | ||
485 | /* Sync one of the CPU's buffers into the global event buffer. | |
486 | * Here we need to go through each batch of samples punctuated | |
487 | * by context switch notes, taking the task's mmap_sem and doing | |
488 | * lookup in task->mm->mmap to convert EIP into dcookie/offset | |
489 | * value. | |
490 | */ | |
491 | void sync_buffer(int cpu) | |
492 | { | |
493 | struct mm_struct *mm = NULL; | |
494 | struct mm_struct *oldmm; | |
495 | unsigned long val; | |
496 | struct task_struct *new; | |
497 | unsigned long cookie = 0; | |
498 | int in_kernel = 1; | |
499 | sync_buffer_state state = sb_buffer_start; | |
500 | unsigned int i; | |
501 | unsigned long available; | |
502 | unsigned long flags; | |
503 | struct op_entry entry; | |
504 | struct op_sample *sample; | |
505 | ||
506 | mutex_lock(&buffer_mutex); | |
507 | ||
508 | add_cpu_switch(cpu); | |
509 | ||
510 | op_cpu_buffer_reset(cpu); | |
511 | available = op_cpu_buffer_entries(cpu); | |
512 | ||
513 | for (i = 0; i < available; ++i) { | |
514 | sample = op_cpu_buffer_read_entry(&entry, cpu); | |
515 | if (!sample) | |
516 | break; | |
517 | ||
518 | if (is_code(sample->eip)) { | |
519 | flags = sample->event; | |
520 | if (flags & TRACE_BEGIN) { | |
521 | state = sb_bt_start; | |
522 | add_trace_begin(); | |
523 | } | |
524 | if (flags & KERNEL_CTX_SWITCH) { | |
525 | /* kernel/userspace switch */ | |
526 | in_kernel = flags & IS_KERNEL; | |
527 | if (state == sb_buffer_start) | |
528 | state = sb_sample_start; | |
529 | add_kernel_ctx_switch(flags & IS_KERNEL); | |
530 | } | |
531 | if (flags & USER_CTX_SWITCH | |
532 | && op_cpu_buffer_get_data(&entry, &val)) { | |
533 | /* userspace context switch */ | |
534 | new = (struct task_struct *)val; | |
535 | oldmm = mm; | |
536 | release_mm(oldmm); | |
537 | mm = get_task_mm(new); | |
538 | if (mm != oldmm) | |
539 | cookie = get_exec_dcookie(mm); | |
540 | add_user_ctx_switch(new, cookie); | |
541 | } | |
542 | if (op_cpu_buffer_get_size(&entry)) | |
543 | add_data(&entry, mm); | |
544 | continue; | |
545 | } | |
546 | ||
547 | if (state < sb_bt_start) | |
548 | /* ignore sample */ | |
549 | continue; | |
550 | ||
551 | if (add_sample(mm, sample, in_kernel)) | |
552 | continue; | |
553 | ||
554 | /* ignore backtraces if failed to add a sample */ | |
555 | if (state == sb_bt_start) { | |
556 | state = sb_bt_ignore; | |
557 | atomic_inc(&oprofile_stats.bt_lost_no_mapping); | |
558 | } | |
559 | } | |
560 | release_mm(mm); | |
561 | ||
562 | mark_done(cpu); | |
563 | ||
564 | mutex_unlock(&buffer_mutex); | |
565 | } | |
566 | ||
567 | /* The function can be used to add a buffer worth of data directly to | |
568 | * the kernel buffer. The buffer is assumed to be a circular buffer. | |
569 | * Take the entries from index start and end at index end, wrapping | |
570 | * at max_entries. | |
571 | */ | |
572 | void oprofile_put_buff(unsigned long *buf, unsigned int start, | |
573 | unsigned int stop, unsigned int max) | |
574 | { | |
575 | int i; | |
576 | ||
577 | i = start; | |
578 | ||
579 | mutex_lock(&buffer_mutex); | |
580 | while (i != stop) { | |
581 | add_event_entry(buf[i++]); | |
582 | ||
583 | if (i >= max) | |
584 | i = 0; | |
585 | } | |
586 | ||
587 | mutex_unlock(&buffer_mutex); | |
588 | } | |
589 |