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