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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/sched/mm.h>
35 #include <linux/sched/task.h>
36 #include <linux/gfp.h>
37 
38 #include "oprofile_stats.h"
39 #include "event_buffer.h"
40 #include "cpu_buffer.h"
41 #include "buffer_sync.h"
42 
43 static LIST_HEAD(dying_tasks);
44 static LIST_HEAD(dead_tasks);
45 static cpumask_var_t marked_cpus;
46 static DEFINE_SPINLOCK(task_mortuary);
47 static void process_task_mortuary(void);
48 
49 /* Take ownership of the task struct and place it on the
50  * list for processing. Only after two full buffer syncs
51  * does the task eventually get freed, because by then
52  * we are sure we will not reference it again.
53  * Can be invoked from softirq via RCU callback due to
54  * call_rcu() of the task struct, hence the _irqsave.
55  */
56 static int
task_free_notify(struct notifier_block * self,unsigned long val,void * data)57 task_free_notify(struct notifier_block *self, unsigned long val, void *data)
58 {
59 	unsigned long flags;
60 	struct task_struct *task = data;
61 	spin_lock_irqsave(&task_mortuary, flags);
62 	list_add(&task->tasks, &dying_tasks);
63 	spin_unlock_irqrestore(&task_mortuary, flags);
64 	return NOTIFY_OK;
65 }
66 
67 
68 /* The task is on its way out. A sync of the buffer means we can catch
69  * any remaining samples for this task.
70  */
71 static int
task_exit_notify(struct notifier_block * self,unsigned long val,void * data)72 task_exit_notify(struct notifier_block *self, unsigned long val, void *data)
73 {
74 	/* To avoid latency problems, we only process the current CPU,
75 	 * hoping that most samples for the task are on this CPU
76 	 */
77 	sync_buffer(raw_smp_processor_id());
78 	return 0;
79 }
80 
81 
82 /* The task is about to try a do_munmap(). We peek at what it's going to
83  * do, and if it's an executable region, process the samples first, so
84  * we don't lose any. This does not have to be exact, it's a QoI issue
85  * only.
86  */
87 static int
munmap_notify(struct notifier_block * self,unsigned long val,void * data)88 munmap_notify(struct notifier_block *self, unsigned long val, void *data)
89 {
90 	unsigned long addr = (unsigned long)data;
91 	struct mm_struct *mm = current->mm;
92 	struct vm_area_struct *mpnt;
93 
94 	down_read(&mm->mmap_sem);
95 
96 	mpnt = find_vma(mm, addr);
97 	if (mpnt && mpnt->vm_file && (mpnt->vm_flags & VM_EXEC)) {
98 		up_read(&mm->mmap_sem);
99 		/* To avoid latency problems, we only process the current CPU,
100 		 * hoping that most samples for the task are on this CPU
101 		 */
102 		sync_buffer(raw_smp_processor_id());
103 		return 0;
104 	}
105 
106 	up_read(&mm->mmap_sem);
107 	return 0;
108 }
109 
110 
111 /* We need to be told about new modules so we don't attribute to a previously
112  * loaded module, or drop the samples on the floor.
113  */
114 static int
module_load_notify(struct notifier_block * self,unsigned long val,void * data)115 module_load_notify(struct notifier_block *self, unsigned long val, void *data)
116 {
117 #ifdef CONFIG_MODULES
118 	if (val != MODULE_STATE_COMING)
119 		return 0;
120 
121 	/* FIXME: should we process all CPU buffers ? */
122 	mutex_lock(&buffer_mutex);
123 	add_event_entry(ESCAPE_CODE);
124 	add_event_entry(MODULE_LOADED_CODE);
125 	mutex_unlock(&buffer_mutex);
126 #endif
127 	return 0;
128 }
129 
130 
131 static struct notifier_block task_free_nb = {
132 	.notifier_call	= task_free_notify,
133 };
134 
135 static struct notifier_block task_exit_nb = {
136 	.notifier_call	= task_exit_notify,
137 };
138 
139 static struct notifier_block munmap_nb = {
140 	.notifier_call	= munmap_notify,
141 };
142 
143 static struct notifier_block module_load_nb = {
144 	.notifier_call = module_load_notify,
145 };
146 
free_all_tasks(void)147 static void free_all_tasks(void)
148 {
149 	/* make sure we don't leak task structs */
150 	process_task_mortuary();
151 	process_task_mortuary();
152 }
153 
sync_start(void)154 int sync_start(void)
155 {
156 	int err;
157 
158 	if (!zalloc_cpumask_var(&marked_cpus, GFP_KERNEL))
159 		return -ENOMEM;
160 
161 	err = task_handoff_register(&task_free_nb);
162 	if (err)
163 		goto out1;
164 	err = profile_event_register(PROFILE_TASK_EXIT, &task_exit_nb);
165 	if (err)
166 		goto out2;
167 	err = profile_event_register(PROFILE_MUNMAP, &munmap_nb);
168 	if (err)
169 		goto out3;
170 	err = register_module_notifier(&module_load_nb);
171 	if (err)
172 		goto out4;
173 
174 	start_cpu_work();
175 
176 out:
177 	return err;
178 out4:
179 	profile_event_unregister(PROFILE_MUNMAP, &munmap_nb);
180 out3:
181 	profile_event_unregister(PROFILE_TASK_EXIT, &task_exit_nb);
182 out2:
183 	task_handoff_unregister(&task_free_nb);
184 	free_all_tasks();
185 out1:
186 	free_cpumask_var(marked_cpus);
187 	goto out;
188 }
189 
190 
sync_stop(void)191 void sync_stop(void)
192 {
193 	end_cpu_work();
194 	unregister_module_notifier(&module_load_nb);
195 	profile_event_unregister(PROFILE_MUNMAP, &munmap_nb);
196 	profile_event_unregister(PROFILE_TASK_EXIT, &task_exit_nb);
197 	task_handoff_unregister(&task_free_nb);
198 	barrier();			/* do all of the above first */
199 
200 	flush_cpu_work();
201 
202 	free_all_tasks();
203 	free_cpumask_var(marked_cpus);
204 }
205 
206 
207 /* Optimisation. We can manage without taking the dcookie sem
208  * because we cannot reach this code without at least one
209  * dcookie user still being registered (namely, the reader
210  * of the event buffer). */
fast_get_dcookie(const struct path * path)211 static inline unsigned long fast_get_dcookie(const struct path *path)
212 {
213 	unsigned long cookie;
214 
215 	if (path->dentry->d_flags & DCACHE_COOKIE)
216 		return (unsigned long)path->dentry;
217 	get_dcookie(path, &cookie);
218 	return cookie;
219 }
220 
221 
222 /* Look up the dcookie for the task's mm->exe_file,
223  * which corresponds loosely to "application name". This is
224  * not strictly necessary but allows oprofile to associate
225  * shared-library samples with particular applications
226  */
get_exec_dcookie(struct mm_struct * mm)227 static unsigned long get_exec_dcookie(struct mm_struct *mm)
228 {
229 	unsigned long cookie = NO_COOKIE;
230 	struct file *exe_file;
231 
232 	if (!mm)
233 		goto done;
234 
235 	exe_file = get_mm_exe_file(mm);
236 	if (!exe_file)
237 		goto done;
238 
239 	cookie = fast_get_dcookie(&exe_file->f_path);
240 	fput(exe_file);
241 done:
242 	return cookie;
243 }
244 
245 
246 /* Convert the EIP value of a sample into a persistent dentry/offset
247  * pair that can then be added to the global event buffer. We make
248  * sure to do this lookup before a mm->mmap modification happens so
249  * we don't lose track.
250  *
251  * The caller must ensure the mm is not nil (ie: not a kernel thread).
252  */
253 static unsigned long
lookup_dcookie(struct mm_struct * mm,unsigned long addr,off_t * offset)254 lookup_dcookie(struct mm_struct *mm, unsigned long addr, off_t *offset)
255 {
256 	unsigned long cookie = NO_COOKIE;
257 	struct vm_area_struct *vma;
258 
259 	down_read(&mm->mmap_sem);
260 	for (vma = find_vma(mm, addr); vma; vma = vma->vm_next) {
261 
262 		if (addr < vma->vm_start || addr >= vma->vm_end)
263 			continue;
264 
265 		if (vma->vm_file) {
266 			cookie = fast_get_dcookie(&vma->vm_file->f_path);
267 			*offset = (vma->vm_pgoff << PAGE_SHIFT) + addr -
268 				vma->vm_start;
269 		} else {
270 			/* must be an anonymous map */
271 			*offset = addr;
272 		}
273 
274 		break;
275 	}
276 
277 	if (!vma)
278 		cookie = INVALID_COOKIE;
279 	up_read(&mm->mmap_sem);
280 
281 	return cookie;
282 }
283 
284 static unsigned long last_cookie = INVALID_COOKIE;
285 
add_cpu_switch(int i)286 static void add_cpu_switch(int i)
287 {
288 	add_event_entry(ESCAPE_CODE);
289 	add_event_entry(CPU_SWITCH_CODE);
290 	add_event_entry(i);
291 	last_cookie = INVALID_COOKIE;
292 }
293 
add_kernel_ctx_switch(unsigned int in_kernel)294 static void add_kernel_ctx_switch(unsigned int in_kernel)
295 {
296 	add_event_entry(ESCAPE_CODE);
297 	if (in_kernel)
298 		add_event_entry(KERNEL_ENTER_SWITCH_CODE);
299 	else
300 		add_event_entry(KERNEL_EXIT_SWITCH_CODE);
301 }
302 
303 static void
add_user_ctx_switch(struct task_struct const * task,unsigned long cookie)304 add_user_ctx_switch(struct task_struct const *task, unsigned long cookie)
305 {
306 	add_event_entry(ESCAPE_CODE);
307 	add_event_entry(CTX_SWITCH_CODE);
308 	add_event_entry(task->pid);
309 	add_event_entry(cookie);
310 	/* Another code for daemon back-compat */
311 	add_event_entry(ESCAPE_CODE);
312 	add_event_entry(CTX_TGID_CODE);
313 	add_event_entry(task->tgid);
314 }
315 
316 
add_cookie_switch(unsigned long cookie)317 static void add_cookie_switch(unsigned long cookie)
318 {
319 	add_event_entry(ESCAPE_CODE);
320 	add_event_entry(COOKIE_SWITCH_CODE);
321 	add_event_entry(cookie);
322 }
323 
324 
add_trace_begin(void)325 static void add_trace_begin(void)
326 {
327 	add_event_entry(ESCAPE_CODE);
328 	add_event_entry(TRACE_BEGIN_CODE);
329 }
330 
add_data(struct op_entry * entry,struct mm_struct * mm)331 static void add_data(struct op_entry *entry, struct mm_struct *mm)
332 {
333 	unsigned long code, pc, val;
334 	unsigned long cookie;
335 	off_t offset;
336 
337 	if (!op_cpu_buffer_get_data(entry, &code))
338 		return;
339 	if (!op_cpu_buffer_get_data(entry, &pc))
340 		return;
341 	if (!op_cpu_buffer_get_size(entry))
342 		return;
343 
344 	if (mm) {
345 		cookie = lookup_dcookie(mm, pc, &offset);
346 
347 		if (cookie == NO_COOKIE)
348 			offset = pc;
349 		if (cookie == INVALID_COOKIE) {
350 			atomic_inc(&oprofile_stats.sample_lost_no_mapping);
351 			offset = pc;
352 		}
353 		if (cookie != last_cookie) {
354 			add_cookie_switch(cookie);
355 			last_cookie = cookie;
356 		}
357 	} else
358 		offset = pc;
359 
360 	add_event_entry(ESCAPE_CODE);
361 	add_event_entry(code);
362 	add_event_entry(offset);	/* Offset from Dcookie */
363 
364 	while (op_cpu_buffer_get_data(entry, &val))
365 		add_event_entry(val);
366 }
367 
add_sample_entry(unsigned long offset,unsigned long event)368 static inline void add_sample_entry(unsigned long offset, unsigned long event)
369 {
370 	add_event_entry(offset);
371 	add_event_entry(event);
372 }
373 
374 
375 /*
376  * Add a sample to the global event buffer. If possible the
377  * sample is converted into a persistent dentry/offset pair
378  * for later lookup from userspace. Return 0 on failure.
379  */
380 static int
add_sample(struct mm_struct * mm,struct op_sample * s,int in_kernel)381 add_sample(struct mm_struct *mm, struct op_sample *s, int in_kernel)
382 {
383 	unsigned long cookie;
384 	off_t offset;
385 
386 	if (in_kernel) {
387 		add_sample_entry(s->eip, s->event);
388 		return 1;
389 	}
390 
391 	/* add userspace sample */
392 
393 	if (!mm) {
394 		atomic_inc(&oprofile_stats.sample_lost_no_mm);
395 		return 0;
396 	}
397 
398 	cookie = lookup_dcookie(mm, s->eip, &offset);
399 
400 	if (cookie == INVALID_COOKIE) {
401 		atomic_inc(&oprofile_stats.sample_lost_no_mapping);
402 		return 0;
403 	}
404 
405 	if (cookie != last_cookie) {
406 		add_cookie_switch(cookie);
407 		last_cookie = cookie;
408 	}
409 
410 	add_sample_entry(offset, s->event);
411 
412 	return 1;
413 }
414 
415 
release_mm(struct mm_struct * mm)416 static void release_mm(struct mm_struct *mm)
417 {
418 	if (!mm)
419 		return;
420 	mmput(mm);
421 }
422 
is_code(unsigned long val)423 static inline int is_code(unsigned long val)
424 {
425 	return val == ESCAPE_CODE;
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  */
process_task_mortuary(void)435 static void process_task_mortuary(void)
436 {
437 	unsigned long flags;
438 	LIST_HEAD(local_dead_tasks);
439 	struct task_struct *task;
440 	struct task_struct *ttask;
441 
442 	spin_lock_irqsave(&task_mortuary, flags);
443 
444 	list_splice_init(&dead_tasks, &local_dead_tasks);
445 	list_splice_init(&dying_tasks, &dead_tasks);
446 
447 	spin_unlock_irqrestore(&task_mortuary, flags);
448 
449 	list_for_each_entry_safe(task, ttask, &local_dead_tasks, tasks) {
450 		list_del(&task->tasks);
451 		free_task(task);
452 	}
453 }
454 
455 
mark_done(int cpu)456 static void mark_done(int cpu)
457 {
458 	int i;
459 
460 	cpumask_set_cpu(cpu, marked_cpus);
461 
462 	for_each_online_cpu(i) {
463 		if (!cpumask_test_cpu(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 	cpumask_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  */
sync_buffer(int cpu)493 void sync_buffer(int cpu)
494 {
495 	struct mm_struct *mm = NULL;
496 	struct mm_struct *oldmm;
497 	unsigned long val;
498 	struct task_struct *new;
499 	unsigned long cookie = 0;
500 	int in_kernel = 1;
501 	sync_buffer_state state = sb_buffer_start;
502 	unsigned int i;
503 	unsigned long available;
504 	unsigned long flags;
505 	struct op_entry entry;
506 	struct op_sample *sample;
507 
508 	mutex_lock(&buffer_mutex);
509 
510 	add_cpu_switch(cpu);
511 
512 	op_cpu_buffer_reset(cpu);
513 	available = op_cpu_buffer_entries(cpu);
514 
515 	for (i = 0; i < available; ++i) {
516 		sample = op_cpu_buffer_read_entry(&entry, cpu);
517 		if (!sample)
518 			break;
519 
520 		if (is_code(sample->eip)) {
521 			flags = sample->event;
522 			if (flags & TRACE_BEGIN) {
523 				state = sb_bt_start;
524 				add_trace_begin();
525 			}
526 			if (flags & KERNEL_CTX_SWITCH) {
527 				/* kernel/userspace switch */
528 				in_kernel = flags & IS_KERNEL;
529 				if (state == sb_buffer_start)
530 					state = sb_sample_start;
531 				add_kernel_ctx_switch(flags & IS_KERNEL);
532 			}
533 			if (flags & USER_CTX_SWITCH
534 			    && op_cpu_buffer_get_data(&entry, &val)) {
535 				/* userspace context switch */
536 				new = (struct task_struct *)val;
537 				oldmm = mm;
538 				release_mm(oldmm);
539 				mm = get_task_mm(new);
540 				if (mm != oldmm)
541 					cookie = get_exec_dcookie(mm);
542 				add_user_ctx_switch(new, cookie);
543 			}
544 			if (op_cpu_buffer_get_size(&entry))
545 				add_data(&entry, mm);
546 			continue;
547 		}
548 
549 		if (state < sb_bt_start)
550 			/* ignore sample */
551 			continue;
552 
553 		if (add_sample(mm, sample, in_kernel))
554 			continue;
555 
556 		/* ignore backtraces if failed to add a sample */
557 		if (state == sb_bt_start) {
558 			state = sb_bt_ignore;
559 			atomic_inc(&oprofile_stats.bt_lost_no_mapping);
560 		}
561 	}
562 	release_mm(mm);
563 
564 	mark_done(cpu);
565 
566 	mutex_unlock(&buffer_mutex);
567 }
568 
569 /* The function can be used to add a buffer worth of data directly to
570  * the kernel buffer. The buffer is assumed to be a circular buffer.
571  * Take the entries from index start and end at index end, wrapping
572  * at max_entries.
573  */
oprofile_put_buff(unsigned long * buf,unsigned int start,unsigned int stop,unsigned int max)574 void oprofile_put_buff(unsigned long *buf, unsigned int start,
575 		       unsigned int stop, unsigned int max)
576 {
577 	int i;
578 
579 	i = start;
580 
581 	mutex_lock(&buffer_mutex);
582 	while (i != stop) {
583 		add_event_entry(buf[i++]);
584 
585 		if (i >= max)
586 			i = 0;
587 	}
588 
589 	mutex_unlock(&buffer_mutex);
590 }
591 
592