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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(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