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1da177e4 LT |
1 | /** |
2 | * @file buffer_sync.c | |
3 | * | |
4 | * @remark Copyright 2002 OProfile authors | |
5 | * @remark Read the file COPYING | |
6 | * | |
7 | * @author John Levon <levon@movementarian.org> | |
8 | * | |
9 | * This is the core of the buffer management. Each | |
10 | * CPU buffer is processed and entered into the | |
11 | * global event buffer. Such processing is necessary | |
12 | * in several circumstances, mentioned below. | |
13 | * | |
14 | * The processing does the job of converting the | |
15 | * transitory EIP value into a persistent dentry/offset | |
16 | * value that the profiler can record at its leisure. | |
17 | * | |
18 | * See fs/dcookies.c for a description of the dentry/offset | |
19 | * objects. | |
20 | */ | |
21 | ||
22 | #include <linux/mm.h> | |
23 | #include <linux/workqueue.h> | |
24 | #include <linux/notifier.h> | |
25 | #include <linux/dcookies.h> | |
26 | #include <linux/profile.h> | |
27 | #include <linux/module.h> | |
28 | #include <linux/fs.h> | |
1474855d | 29 | #include <linux/oprofile.h> |
e8edc6e0 | 30 | #include <linux/sched.h> |
1474855d | 31 | |
1da177e4 LT |
32 | #include "oprofile_stats.h" |
33 | #include "event_buffer.h" | |
34 | #include "cpu_buffer.h" | |
35 | #include "buffer_sync.h" | |
73185e0a | 36 | |
1da177e4 LT |
37 | static LIST_HEAD(dying_tasks); |
38 | static LIST_HEAD(dead_tasks); | |
39 | static cpumask_t marked_cpus = CPU_MASK_NONE; | |
40 | static DEFINE_SPINLOCK(task_mortuary); | |
41 | static void process_task_mortuary(void); | |
42 | ||
43 | ||
44 | /* Take ownership of the task struct and place it on the | |
45 | * list for processing. Only after two full buffer syncs | |
46 | * does the task eventually get freed, because by then | |
47 | * we are sure we will not reference it again. | |
4369ef3c PM |
48 | * Can be invoked from softirq via RCU callback due to |
49 | * call_rcu() of the task struct, hence the _irqsave. | |
1da177e4 | 50 | */ |
73185e0a RR |
51 | static int |
52 | task_free_notify(struct notifier_block *self, unsigned long val, void *data) | |
1da177e4 | 53 | { |
4369ef3c | 54 | unsigned long flags; |
73185e0a | 55 | struct task_struct *task = data; |
4369ef3c | 56 | spin_lock_irqsave(&task_mortuary, flags); |
1da177e4 | 57 | list_add(&task->tasks, &dying_tasks); |
4369ef3c | 58 | spin_unlock_irqrestore(&task_mortuary, flags); |
1da177e4 LT |
59 | return NOTIFY_OK; |
60 | } | |
61 | ||
62 | ||
63 | /* The task is on its way out. A sync of the buffer means we can catch | |
64 | * any remaining samples for this task. | |
65 | */ | |
73185e0a RR |
66 | static int |
67 | task_exit_notify(struct notifier_block *self, unsigned long val, void *data) | |
1da177e4 LT |
68 | { |
69 | /* To avoid latency problems, we only process the current CPU, | |
70 | * hoping that most samples for the task are on this CPU | |
71 | */ | |
39c715b7 | 72 | sync_buffer(raw_smp_processor_id()); |
73185e0a | 73 | return 0; |
1da177e4 LT |
74 | } |
75 | ||
76 | ||
77 | /* The task is about to try a do_munmap(). We peek at what it's going to | |
78 | * do, and if it's an executable region, process the samples first, so | |
79 | * we don't lose any. This does not have to be exact, it's a QoI issue | |
80 | * only. | |
81 | */ | |
73185e0a RR |
82 | static int |
83 | munmap_notify(struct notifier_block *self, unsigned long val, void *data) | |
1da177e4 LT |
84 | { |
85 | unsigned long addr = (unsigned long)data; | |
73185e0a RR |
86 | struct mm_struct *mm = current->mm; |
87 | struct vm_area_struct *mpnt; | |
1da177e4 LT |
88 | |
89 | down_read(&mm->mmap_sem); | |
90 | ||
91 | mpnt = find_vma(mm, addr); | |
92 | if (mpnt && mpnt->vm_file && (mpnt->vm_flags & VM_EXEC)) { | |
93 | up_read(&mm->mmap_sem); | |
94 | /* To avoid latency problems, we only process the current CPU, | |
95 | * hoping that most samples for the task are on this CPU | |
96 | */ | |
39c715b7 | 97 | sync_buffer(raw_smp_processor_id()); |
1da177e4 LT |
98 | return 0; |
99 | } | |
100 | ||
101 | up_read(&mm->mmap_sem); | |
102 | return 0; | |
103 | } | |
104 | ||
73185e0a | 105 | |
1da177e4 LT |
106 | /* We need to be told about new modules so we don't attribute to a previously |
107 | * loaded module, or drop the samples on the floor. | |
108 | */ | |
73185e0a RR |
109 | static int |
110 | module_load_notify(struct notifier_block *self, unsigned long val, void *data) | |
1da177e4 LT |
111 | { |
112 | #ifdef CONFIG_MODULES | |
113 | if (val != MODULE_STATE_COMING) | |
114 | return 0; | |
115 | ||
116 | /* FIXME: should we process all CPU buffers ? */ | |
59cc185a | 117 | mutex_lock(&buffer_mutex); |
1da177e4 LT |
118 | add_event_entry(ESCAPE_CODE); |
119 | add_event_entry(MODULE_LOADED_CODE); | |
59cc185a | 120 | mutex_unlock(&buffer_mutex); |
1da177e4 LT |
121 | #endif |
122 | return 0; | |
123 | } | |
124 | ||
73185e0a | 125 | |
1da177e4 LT |
126 | static struct notifier_block task_free_nb = { |
127 | .notifier_call = task_free_notify, | |
128 | }; | |
129 | ||
130 | static struct notifier_block task_exit_nb = { | |
131 | .notifier_call = task_exit_notify, | |
132 | }; | |
133 | ||
134 | static struct notifier_block munmap_nb = { | |
135 | .notifier_call = munmap_notify, | |
136 | }; | |
137 | ||
138 | static struct notifier_block module_load_nb = { | |
139 | .notifier_call = module_load_notify, | |
140 | }; | |
141 | ||
73185e0a | 142 | |
1da177e4 LT |
143 | static void end_sync(void) |
144 | { | |
145 | end_cpu_work(); | |
146 | /* make sure we don't leak task structs */ | |
147 | process_task_mortuary(); | |
148 | process_task_mortuary(); | |
149 | } | |
150 | ||
151 | ||
152 | int sync_start(void) | |
153 | { | |
154 | int err; | |
155 | ||
156 | start_cpu_work(); | |
157 | ||
158 | err = task_handoff_register(&task_free_nb); | |
159 | if (err) | |
160 | goto out1; | |
161 | err = profile_event_register(PROFILE_TASK_EXIT, &task_exit_nb); | |
162 | if (err) | |
163 | goto out2; | |
164 | err = profile_event_register(PROFILE_MUNMAP, &munmap_nb); | |
165 | if (err) | |
166 | goto out3; | |
167 | err = register_module_notifier(&module_load_nb); | |
168 | if (err) | |
169 | goto out4; | |
170 | ||
171 | out: | |
172 | return err; | |
173 | out4: | |
174 | profile_event_unregister(PROFILE_MUNMAP, &munmap_nb); | |
175 | out3: | |
176 | profile_event_unregister(PROFILE_TASK_EXIT, &task_exit_nb); | |
177 | out2: | |
178 | task_handoff_unregister(&task_free_nb); | |
179 | out1: | |
180 | end_sync(); | |
181 | goto out; | |
182 | } | |
183 | ||
184 | ||
185 | void sync_stop(void) | |
186 | { | |
187 | unregister_module_notifier(&module_load_nb); | |
188 | profile_event_unregister(PROFILE_MUNMAP, &munmap_nb); | |
189 | profile_event_unregister(PROFILE_TASK_EXIT, &task_exit_nb); | |
190 | task_handoff_unregister(&task_free_nb); | |
191 | end_sync(); | |
192 | } | |
193 | ||
448678a0 | 194 | |
1da177e4 LT |
195 | /* Optimisation. We can manage without taking the dcookie sem |
196 | * because we cannot reach this code without at least one | |
197 | * dcookie user still being registered (namely, the reader | |
198 | * of the event buffer). */ | |
448678a0 | 199 | static inline unsigned long fast_get_dcookie(struct path *path) |
1da177e4 LT |
200 | { |
201 | unsigned long cookie; | |
448678a0 JB |
202 | |
203 | if (path->dentry->d_cookie) | |
204 | return (unsigned long)path->dentry; | |
205 | get_dcookie(path, &cookie); | |
1da177e4 LT |
206 | return cookie; |
207 | } | |
208 | ||
448678a0 | 209 | |
1da177e4 LT |
210 | /* Look up the dcookie for the task's first VM_EXECUTABLE mapping, |
211 | * which corresponds loosely to "application name". This is | |
212 | * not strictly necessary but allows oprofile to associate | |
213 | * shared-library samples with particular applications | |
214 | */ | |
73185e0a | 215 | static unsigned long get_exec_dcookie(struct mm_struct *mm) |
1da177e4 | 216 | { |
0c0a400d | 217 | unsigned long cookie = NO_COOKIE; |
73185e0a RR |
218 | struct vm_area_struct *vma; |
219 | ||
1da177e4 LT |
220 | if (!mm) |
221 | goto out; | |
73185e0a | 222 | |
1da177e4 LT |
223 | for (vma = mm->mmap; vma; vma = vma->vm_next) { |
224 | if (!vma->vm_file) | |
225 | continue; | |
226 | if (!(vma->vm_flags & VM_EXECUTABLE)) | |
227 | continue; | |
448678a0 | 228 | cookie = fast_get_dcookie(&vma->vm_file->f_path); |
1da177e4 LT |
229 | break; |
230 | } | |
231 | ||
232 | out: | |
233 | return cookie; | |
234 | } | |
235 | ||
236 | ||
237 | /* Convert the EIP value of a sample into a persistent dentry/offset | |
238 | * pair that can then be added to the global event buffer. We make | |
239 | * sure to do this lookup before a mm->mmap modification happens so | |
240 | * we don't lose track. | |
241 | */ | |
73185e0a RR |
242 | static unsigned long |
243 | lookup_dcookie(struct mm_struct *mm, unsigned long addr, off_t *offset) | |
1da177e4 | 244 | { |
0c0a400d | 245 | unsigned long cookie = NO_COOKIE; |
73185e0a | 246 | struct vm_area_struct *vma; |
1da177e4 LT |
247 | |
248 | for (vma = find_vma(mm, addr); vma; vma = vma->vm_next) { | |
73185e0a | 249 | |
1da177e4 LT |
250 | if (addr < vma->vm_start || addr >= vma->vm_end) |
251 | continue; | |
252 | ||
0c0a400d | 253 | if (vma->vm_file) { |
448678a0 | 254 | cookie = fast_get_dcookie(&vma->vm_file->f_path); |
0c0a400d JL |
255 | *offset = (vma->vm_pgoff << PAGE_SHIFT) + addr - |
256 | vma->vm_start; | |
257 | } else { | |
258 | /* must be an anonymous map */ | |
259 | *offset = addr; | |
260 | } | |
261 | ||
1da177e4 LT |
262 | break; |
263 | } | |
264 | ||
0c0a400d JL |
265 | if (!vma) |
266 | cookie = INVALID_COOKIE; | |
267 | ||
1da177e4 LT |
268 | return cookie; |
269 | } | |
270 | ||
5e11f98d RR |
271 | static void increment_tail(struct oprofile_cpu_buffer *b) |
272 | { | |
273 | unsigned long new_tail = b->tail_pos + 1; | |
274 | ||
275 | rmb(); | |
276 | ||
277 | if (new_tail < b->buffer_size) | |
278 | b->tail_pos = new_tail; | |
279 | else | |
280 | b->tail_pos = 0; | |
281 | } | |
1da177e4 | 282 | |
0c0a400d | 283 | static unsigned long last_cookie = INVALID_COOKIE; |
73185e0a | 284 | |
1da177e4 LT |
285 | static void add_cpu_switch(int i) |
286 | { | |
287 | add_event_entry(ESCAPE_CODE); | |
288 | add_event_entry(CPU_SWITCH_CODE); | |
289 | add_event_entry(i); | |
0c0a400d | 290 | last_cookie = INVALID_COOKIE; |
1da177e4 LT |
291 | } |
292 | ||
293 | static void add_kernel_ctx_switch(unsigned int in_kernel) | |
294 | { | |
295 | add_event_entry(ESCAPE_CODE); | |
296 | if (in_kernel) | |
73185e0a | 297 | add_event_entry(KERNEL_ENTER_SWITCH_CODE); |
1da177e4 | 298 | else |
73185e0a | 299 | add_event_entry(KERNEL_EXIT_SWITCH_CODE); |
1da177e4 | 300 | } |
73185e0a | 301 | |
1da177e4 | 302 | static void |
73185e0a | 303 | add_user_ctx_switch(struct task_struct const *task, unsigned long cookie) |
1da177e4 LT |
304 | { |
305 | add_event_entry(ESCAPE_CODE); | |
73185e0a | 306 | add_event_entry(CTX_SWITCH_CODE); |
1da177e4 LT |
307 | add_event_entry(task->pid); |
308 | add_event_entry(cookie); | |
309 | /* Another code for daemon back-compat */ | |
310 | add_event_entry(ESCAPE_CODE); | |
311 | add_event_entry(CTX_TGID_CODE); | |
312 | add_event_entry(task->tgid); | |
313 | } | |
314 | ||
73185e0a | 315 | |
1da177e4 LT |
316 | static void add_cookie_switch(unsigned long cookie) |
317 | { | |
318 | add_event_entry(ESCAPE_CODE); | |
319 | add_event_entry(COOKIE_SWITCH_CODE); | |
320 | add_event_entry(cookie); | |
321 | } | |
322 | ||
73185e0a | 323 | |
1da177e4 LT |
324 | static void add_trace_begin(void) |
325 | { | |
326 | add_event_entry(ESCAPE_CODE); | |
327 | add_event_entry(TRACE_BEGIN_CODE); | |
328 | } | |
329 | ||
330 | ||
331 | static void add_sample_entry(unsigned long offset, unsigned long event) | |
332 | { | |
333 | add_event_entry(offset); | |
334 | add_event_entry(event); | |
335 | } | |
336 | ||
337 | ||
73185e0a | 338 | static int add_us_sample(struct mm_struct *mm, struct op_sample *s) |
1da177e4 LT |
339 | { |
340 | unsigned long cookie; | |
341 | off_t offset; | |
73185e0a RR |
342 | |
343 | cookie = lookup_dcookie(mm, s->eip, &offset); | |
344 | ||
0c0a400d | 345 | if (cookie == INVALID_COOKIE) { |
1da177e4 LT |
346 | atomic_inc(&oprofile_stats.sample_lost_no_mapping); |
347 | return 0; | |
348 | } | |
349 | ||
350 | if (cookie != last_cookie) { | |
351 | add_cookie_switch(cookie); | |
352 | last_cookie = cookie; | |
353 | } | |
354 | ||
355 | add_sample_entry(offset, s->event); | |
356 | ||
357 | return 1; | |
358 | } | |
359 | ||
73185e0a | 360 | |
1da177e4 LT |
361 | /* Add a sample to the global event buffer. If possible the |
362 | * sample is converted into a persistent dentry/offset pair | |
363 | * for later lookup from userspace. | |
364 | */ | |
365 | static int | |
73185e0a | 366 | add_sample(struct mm_struct *mm, struct op_sample *s, int in_kernel) |
1da177e4 LT |
367 | { |
368 | if (in_kernel) { | |
369 | add_sample_entry(s->eip, s->event); | |
370 | return 1; | |
371 | } else if (mm) { | |
372 | return add_us_sample(mm, s); | |
373 | } else { | |
374 | atomic_inc(&oprofile_stats.sample_lost_no_mm); | |
375 | } | |
376 | return 0; | |
377 | } | |
1da177e4 | 378 | |
73185e0a RR |
379 | |
380 | static void release_mm(struct mm_struct *mm) | |
1da177e4 LT |
381 | { |
382 | if (!mm) | |
383 | return; | |
384 | up_read(&mm->mmap_sem); | |
385 | mmput(mm); | |
386 | } | |
387 | ||
388 | ||
73185e0a | 389 | static struct mm_struct *take_tasks_mm(struct task_struct *task) |
1da177e4 | 390 | { |
73185e0a | 391 | struct mm_struct *mm = get_task_mm(task); |
1da177e4 LT |
392 | if (mm) |
393 | down_read(&mm->mmap_sem); | |
394 | return mm; | |
395 | } | |
396 | ||
397 | ||
398 | static inline int is_code(unsigned long val) | |
399 | { | |
400 | return val == ESCAPE_CODE; | |
401 | } | |
73185e0a | 402 | |
1da177e4 LT |
403 | |
404 | /* "acquire" as many cpu buffer slots as we can */ | |
73185e0a | 405 | static unsigned long get_slots(struct oprofile_cpu_buffer *b) |
1da177e4 LT |
406 | { |
407 | unsigned long head = b->head_pos; | |
408 | unsigned long tail = b->tail_pos; | |
409 | ||
410 | /* | |
411 | * Subtle. This resets the persistent last_task | |
412 | * and in_kernel values used for switching notes. | |
413 | * BUT, there is a small window between reading | |
414 | * head_pos, and this call, that means samples | |
415 | * can appear at the new head position, but not | |
416 | * be prefixed with the notes for switching | |
417 | * kernel mode or a task switch. This small hole | |
418 | * can lead to mis-attribution or samples where | |
419 | * we don't know if it's in the kernel or not, | |
420 | * at the start of an event buffer. | |
421 | */ | |
422 | cpu_buffer_reset(b); | |
423 | ||
424 | if (head >= tail) | |
425 | return head - tail; | |
426 | ||
427 | return head + (b->buffer_size - tail); | |
428 | } | |
429 | ||
430 | ||
1da177e4 LT |
431 | /* Move tasks along towards death. Any tasks on dead_tasks |
432 | * will definitely have no remaining references in any | |
433 | * CPU buffers at this point, because we use two lists, | |
434 | * and to have reached the list, it must have gone through | |
435 | * one full sync already. | |
436 | */ | |
437 | static void process_task_mortuary(void) | |
438 | { | |
4369ef3c PM |
439 | unsigned long flags; |
440 | LIST_HEAD(local_dead_tasks); | |
73185e0a RR |
441 | struct task_struct *task; |
442 | struct task_struct *ttask; | |
1da177e4 | 443 | |
4369ef3c | 444 | spin_lock_irqsave(&task_mortuary, flags); |
1da177e4 | 445 | |
4369ef3c PM |
446 | list_splice_init(&dead_tasks, &local_dead_tasks); |
447 | list_splice_init(&dying_tasks, &dead_tasks); | |
1da177e4 | 448 | |
4369ef3c PM |
449 | spin_unlock_irqrestore(&task_mortuary, flags); |
450 | ||
451 | list_for_each_entry_safe(task, ttask, &local_dead_tasks, tasks) { | |
1da177e4 | 452 | list_del(&task->tasks); |
4369ef3c | 453 | free_task(task); |
1da177e4 | 454 | } |
1da177e4 LT |
455 | } |
456 | ||
457 | ||
458 | static void mark_done(int cpu) | |
459 | { | |
460 | int i; | |
461 | ||
462 | cpu_set(cpu, marked_cpus); | |
463 | ||
464 | for_each_online_cpu(i) { | |
465 | if (!cpu_isset(i, marked_cpus)) | |
466 | return; | |
467 | } | |
468 | ||
469 | /* All CPUs have been processed at least once, | |
470 | * we can process the mortuary once | |
471 | */ | |
472 | process_task_mortuary(); | |
473 | ||
474 | cpus_clear(marked_cpus); | |
475 | } | |
476 | ||
477 | ||
478 | /* FIXME: this is not sufficient if we implement syscall barrier backtrace | |
479 | * traversal, the code switch to sb_sample_start at first kernel enter/exit | |
480 | * switch so we need a fifth state and some special handling in sync_buffer() | |
481 | */ | |
482 | typedef enum { | |
483 | sb_bt_ignore = -2, | |
484 | sb_buffer_start, | |
485 | sb_bt_start, | |
486 | sb_sample_start, | |
487 | } sync_buffer_state; | |
488 | ||
489 | /* Sync one of the CPU's buffers into the global event buffer. | |
490 | * Here we need to go through each batch of samples punctuated | |
491 | * by context switch notes, taking the task's mmap_sem and doing | |
492 | * lookup in task->mm->mmap to convert EIP into dcookie/offset | |
493 | * value. | |
494 | */ | |
495 | void sync_buffer(int cpu) | |
496 | { | |
608dfddd | 497 | struct oprofile_cpu_buffer *cpu_buf = &per_cpu(cpu_buffer, cpu); |
1da177e4 | 498 | struct mm_struct *mm = NULL; |
73185e0a | 499 | struct task_struct *new; |
1da177e4 LT |
500 | unsigned long cookie = 0; |
501 | int in_kernel = 1; | |
502 | unsigned int i; | |
503 | sync_buffer_state state = sb_buffer_start; | |
504 | unsigned long available; | |
505 | ||
59cc185a | 506 | mutex_lock(&buffer_mutex); |
73185e0a | 507 | |
1da177e4 LT |
508 | add_cpu_switch(cpu); |
509 | ||
510 | /* Remember, only we can modify tail_pos */ | |
511 | ||
512 | available = get_slots(cpu_buf); | |
513 | ||
514 | for (i = 0; i < available; ++i) { | |
73185e0a RR |
515 | struct op_sample *s = &cpu_buf->buffer[cpu_buf->tail_pos]; |
516 | ||
1da177e4 LT |
517 | if (is_code(s->eip)) { |
518 | if (s->event <= CPU_IS_KERNEL) { | |
519 | /* kernel/userspace switch */ | |
520 | in_kernel = s->event; | |
521 | if (state == sb_buffer_start) | |
522 | state = sb_sample_start; | |
523 | add_kernel_ctx_switch(s->event); | |
524 | } else if (s->event == CPU_TRACE_BEGIN) { | |
525 | state = sb_bt_start; | |
526 | add_trace_begin(); | |
527 | } else { | |
73185e0a | 528 | struct mm_struct *oldmm = mm; |
1da177e4 LT |
529 | |
530 | /* userspace context switch */ | |
531 | new = (struct task_struct *)s->event; | |
532 | ||
533 | release_mm(oldmm); | |
534 | mm = take_tasks_mm(new); | |
535 | if (mm != oldmm) | |
536 | cookie = get_exec_dcookie(mm); | |
537 | add_user_ctx_switch(new, cookie); | |
538 | } | |
73185e0a RR |
539 | } else if (state >= sb_bt_start && |
540 | !add_sample(mm, s, in_kernel)) { | |
541 | if (state == sb_bt_start) { | |
542 | state = sb_bt_ignore; | |
543 | atomic_inc(&oprofile_stats.bt_lost_no_mapping); | |
1da177e4 LT |
544 | } |
545 | } | |
546 | ||
547 | increment_tail(cpu_buf); | |
548 | } | |
549 | release_mm(mm); | |
550 | ||
551 | mark_done(cpu); | |
552 | ||
59cc185a | 553 | mutex_unlock(&buffer_mutex); |
1da177e4 | 554 | } |