root/drivers/oprofile/buffer_sync.c

DEFINITIONS

1. task_free_notify
2. task_exit_notify
3. munmap_notify
4. module_load_notify
5. free_all_tasks
6. sync_start
7. sync_stop
8. fast_get_dcookie
9. get_exec_dcookie
10. lookup_dcookie
11. add_cpu_switch
12. add_kernel_ctx_switch
13. add_user_ctx_switch
14. add_cookie_switch
15. add_trace_begin
16. add_data
17. add_sample_entry
18. add_sample
19. release_mm
20. is_code
21. process_task_mortuary
22. mark_done
23. sync_buffer
24. oprofile_put_buff

   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
  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
  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
  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
 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 
 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 
 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 
 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). */
 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  */
 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
 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 
 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 
 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
 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 
 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 
 325 static void add_trace_begin(void)
 326 {
 327         add_event_entry(ESCAPE_CODE);
 328         add_event_entry(TRACE_BEGIN_CODE);
 329 }
 330 
 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 
 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
 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 
 416 static void release_mm(struct mm_struct *mm)
 417 {
 418         if (!mm)
 419                 return;
 420         mmput(mm);
 421 }
 422 
 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  */
 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 
 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  */
 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  */
 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