linux/drivers/oprofile/buffer_sync.c
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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/mm.h>
  25#include <linux/workqueue.h>
  26#include <linux/notifier.h>
  27#include <linux/dcookies.h>
  28#include <linux/profile.h>
  29#include <linux/module.h>
  30#include <linux/fs.h>
  31#include <linux/oprofile.h>
  32#include <linux/sched.h>
  33#include <linux/gfp.h>
  34
  35#include "oprofile_stats.h"
  36#include "event_buffer.h"
  37#include "cpu_buffer.h"
  38#include "buffer_sync.h"
  39
  40static LIST_HEAD(dying_tasks);
  41static LIST_HEAD(dead_tasks);
  42static cpumask_var_t marked_cpus;
  43static DEFINE_SPINLOCK(task_mortuary);
  44static void process_task_mortuary(void);
  45
  46/* Take ownership of the task struct and place it on the
  47 * list for processing. Only after two full buffer syncs
  48 * does the task eventually get freed, because by then
  49 * we are sure we will not reference it again.
  50 * Can be invoked from softirq via RCU callback due to
  51 * call_rcu() of the task struct, hence the _irqsave.
  52 */
  53static int
  54task_free_notify(struct notifier_block *self, unsigned long val, void *data)
  55{
  56        unsigned long flags;
  57        struct task_struct *task = data;
  58        spin_lock_irqsave(&task_mortuary, flags);
  59        list_add(&task->tasks, &dying_tasks);
  60        spin_unlock_irqrestore(&task_mortuary, flags);
  61        return NOTIFY_OK;
  62}
  63
  64
  65/* The task is on its way out. A sync of the buffer means we can catch
  66 * any remaining samples for this task.
  67 */
  68static int
  69task_exit_notify(struct notifier_block *self, unsigned long val, void *data)
  70{
  71        /* To avoid latency problems, we only process the current CPU,
  72         * hoping that most samples for the task are on this CPU
  73         */
  74        sync_buffer(raw_smp_processor_id());
  75        return 0;
  76}
  77
  78
  79/* The task is about to try a do_munmap(). We peek at what it's going to
  80 * do, and if it's an executable region, process the samples first, so
  81 * we don't lose any. This does not have to be exact, it's a QoI issue
  82 * only.
  83 */
  84static int
  85munmap_notify(struct notifier_block *self, unsigned long val, void *data)
  86{
  87        unsigned long addr = (unsigned long)data;
  88        struct mm_struct *mm = current->mm;
  89        struct vm_area_struct *mpnt;
  90
  91        down_read(&mm->mmap_sem);
  92
  93        mpnt = find_vma(mm, addr);
  94        if (mpnt && mpnt->vm_file && (mpnt->vm_flags & VM_EXEC)) {
  95                up_read(&mm->mmap_sem);
  96                /* To avoid latency problems, we only process the current CPU,
  97                 * hoping that most samples for the task are on this CPU
  98                 */
  99                sync_buffer(raw_smp_processor_id());
 100                return 0;
 101        }
 102
 103        up_read(&mm->mmap_sem);
 104        return 0;
 105}
 106
 107
 108/* We need to be told about new modules so we don't attribute to a previously
 109 * loaded module, or drop the samples on the floor.
 110 */
 111static int
 112module_load_notify(struct notifier_block *self, unsigned long val, void *data)
 113{
 114#ifdef CONFIG_MODULES
 115        if (val != MODULE_STATE_COMING)
 116                return 0;
 117
 118        /* FIXME: should we process all CPU buffers ? */
 119        mutex_lock(&buffer_mutex);
 120        add_event_entry(ESCAPE_CODE);
 121        add_event_entry(MODULE_LOADED_CODE);
 122        mutex_unlock(&buffer_mutex);
 123#endif
 124        return 0;
 125}
 126
 127
 128static struct notifier_block task_free_nb = {
 129        .notifier_call  = task_free_notify,
 130};
 131
 132static struct notifier_block task_exit_nb = {
 133        .notifier_call  = task_exit_notify,
 134};
 135
 136static struct notifier_block munmap_nb = {
 137        .notifier_call  = munmap_notify,
 138};
 139
 140static struct notifier_block module_load_nb = {
 141        .notifier_call = module_load_notify,
 142};
 143
 144static void free_all_tasks(void)
 145{
 146        /* make sure we don't leak task structs */
 147        process_task_mortuary();
 148        process_task_mortuary();
 149}
 150
 151int sync_start(void)
 152{
 153        int err;
 154
 155        if (!zalloc_cpumask_var(&marked_cpus, GFP_KERNEL))
 156                return -ENOMEM;
 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        start_cpu_work();
 172
 173out:
 174        return err;
 175out4:
 176        profile_event_unregister(PROFILE_MUNMAP, &munmap_nb);
 177out3:
 178        profile_event_unregister(PROFILE_TASK_EXIT, &task_exit_nb);
 179out2:
 180        task_handoff_unregister(&task_free_nb);
 181        free_all_tasks();
 182out1:
 183        free_cpumask_var(marked_cpus);
 184        goto out;
 185}
 186
 187
 188void sync_stop(void)
 189{
 190        end_cpu_work();
 191        unregister_module_notifier(&module_load_nb);
 192        profile_event_unregister(PROFILE_MUNMAP, &munmap_nb);
 193        profile_event_unregister(PROFILE_TASK_EXIT, &task_exit_nb);
 194        task_handoff_unregister(&task_free_nb);
 195        barrier();                      /* do all of the above first */
 196
 197        flush_cpu_work();
 198
 199        free_all_tasks();
 200        free_cpumask_var(marked_cpus);
 201}
 202
 203
 204/* Optimisation. We can manage without taking the dcookie sem
 205 * because we cannot reach this code without at least one
 206 * dcookie user still being registered (namely, the reader
 207 * of the event buffer). */
 208static inline unsigned long fast_get_dcookie(struct path *path)
 209{
 210        unsigned long cookie;
 211
 212        if (path->dentry->d_flags & DCACHE_COOKIE)
 213                return (unsigned long)path->dentry;
 214        get_dcookie(path, &cookie);
 215        return cookie;
 216}
 217
 218
 219/* Look up the dcookie for the task's first VM_EXECUTABLE mapping,
 220 * which corresponds loosely to "application name". This is
 221 * not strictly necessary but allows oprofile to associate
 222 * shared-library samples with particular applications
 223 */
 224static unsigned long get_exec_dcookie(struct mm_struct *mm)
 225{
 226        unsigned long cookie = NO_COOKIE;
 227        struct vm_area_struct *vma;
 228
 229        if (!mm)
 230                goto out;
 231
 232        for (vma = mm->mmap; vma; vma = vma->vm_next) {
 233                if (!vma->vm_file)
 234                        continue;
 235                if (!(vma->vm_flags & VM_EXECUTABLE))
 236                        continue;
 237                cookie = fast_get_dcookie(&vma->vm_file->f_path);
 238                break;
 239        }
 240
 241out:
 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 */
 251static unsigned long
 252lookup_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        for (vma = find_vma(mm, addr); vma; vma = vma->vm_next) {
 258
 259                if (addr < vma->vm_start || addr >= vma->vm_end)
 260                        continue;
 261
 262                if (vma->vm_file) {
 263                        cookie = fast_get_dcookie(&vma->vm_file->f_path);
 264                        *offset = (vma->vm_pgoff << PAGE_SHIFT) + addr -
 265                                vma->vm_start;
 266                } else {
 267                        /* must be an anonymous map */
 268                        *offset = addr;
 269                }
 270
 271                break;
 272        }
 273
 274        if (!vma)
 275                cookie = INVALID_COOKIE;
 276
 277        return cookie;
 278}
 279
 280static unsigned long last_cookie = INVALID_COOKIE;
 281
 282static void add_cpu_switch(int i)
 283{
 284        add_event_entry(ESCAPE_CODE);
 285        add_event_entry(CPU_SWITCH_CODE);
 286        add_event_entry(i);
 287        last_cookie = INVALID_COOKIE;
 288}
 289
 290static void add_kernel_ctx_switch(unsigned int in_kernel)
 291{
 292        add_event_entry(ESCAPE_CODE);
 293        if (in_kernel)
 294                add_event_entry(KERNEL_ENTER_SWITCH_CODE);
 295        else
 296                add_event_entry(KERNEL_EXIT_SWITCH_CODE);
 297}
 298
 299static void
 300add_user_ctx_switch(struct task_struct const *task, unsigned long cookie)
 301{
 302        add_event_entry(ESCAPE_CODE);
 303        add_event_entry(CTX_SWITCH_CODE);
 304        add_event_entry(task->pid);
 305        add_event_entry(cookie);
 306        /* Another code for daemon back-compat */
 307        add_event_entry(ESCAPE_CODE);
 308        add_event_entry(CTX_TGID_CODE);
 309        add_event_entry(task->tgid);
 310}
 311
 312
 313static void add_cookie_switch(unsigned long cookie)
 314{
 315        add_event_entry(ESCAPE_CODE);
 316        add_event_entry(COOKIE_SWITCH_CODE);
 317        add_event_entry(cookie);
 318}
 319
 320
 321static void add_trace_begin(void)
 322{
 323        add_event_entry(ESCAPE_CODE);
 324        add_event_entry(TRACE_BEGIN_CODE);
 325}
 326
 327static void add_data(struct op_entry *entry, struct mm_struct *mm)
 328{
 329        unsigned long code, pc, val;
 330        unsigned long cookie;
 331        off_t offset;
 332
 333        if (!op_cpu_buffer_get_data(entry, &code))
 334                return;
 335        if (!op_cpu_buffer_get_data(entry, &pc))
 336                return;
 337        if (!op_cpu_buffer_get_size(entry))
 338                return;
 339
 340        if (mm) {
 341                cookie = lookup_dcookie(mm, pc, &offset);
 342
 343                if (cookie == NO_COOKIE)
 344                        offset = pc;
 345                if (cookie == INVALID_COOKIE) {
 346                        atomic_inc(&oprofile_stats.sample_lost_no_mapping);
 347                        offset = pc;
 348                }
 349                if (cookie != last_cookie) {
 350                        add_cookie_switch(cookie);
 351                        last_cookie = cookie;
 352                }
 353        } else
 354                offset = pc;
 355
 356        add_event_entry(ESCAPE_CODE);
 357        add_event_entry(code);
 358        add_event_entry(offset);        /* Offset from Dcookie */
 359
 360        while (op_cpu_buffer_get_data(entry, &val))
 361                add_event_entry(val);
 362}
 363
 364static inline void add_sample_entry(unsigned long offset, unsigned long event)
 365{
 366        add_event_entry(offset);
 367        add_event_entry(event);
 368}
 369
 370
 371/*
 372 * Add a sample to the global event buffer. If possible the
 373 * sample is converted into a persistent dentry/offset pair
 374 * for later lookup from userspace. Return 0 on failure.
 375 */
 376static int
 377add_sample(struct mm_struct *mm, struct op_sample *s, int in_kernel)
 378{
 379        unsigned long cookie;
 380        off_t offset;
 381
 382        if (in_kernel) {
 383                add_sample_entry(s->eip, s->event);
 384                return 1;
 385        }
 386
 387        /* add userspace sample */
 388
 389        if (!mm) {
 390                atomic_inc(&oprofile_stats.sample_lost_no_mm);
 391                return 0;
 392        }
 393
 394        cookie = lookup_dcookie(mm, s->eip, &offset);
 395
 396        if (cookie == INVALID_COOKIE) {
 397                atomic_inc(&oprofile_stats.sample_lost_no_mapping);
 398                return 0;
 399        }
 400
 401        if (cookie != last_cookie) {
 402                add_cookie_switch(cookie);
 403                last_cookie = cookie;
 404        }
 405
 406        add_sample_entry(offset, s->event);
 407
 408        return 1;
 409}
 410
 411
 412static void release_mm(struct mm_struct *mm)
 413{
 414        if (!mm)
 415                return;
 416        up_read(&mm->mmap_sem);
 417        mmput(mm);
 418}
 419
 420
 421static struct mm_struct *take_tasks_mm(struct task_struct *task)
 422{
 423        struct mm_struct *mm = get_task_mm(task);
 424        if (mm)
 425                down_read(&mm->mmap_sem);
 426        return mm;
 427}
 428
 429
 430static inline int is_code(unsigned long val)
 431{
 432        return val == ESCAPE_CODE;
 433}
 434
 435
 436/* Move tasks along towards death. Any tasks on dead_tasks
 437 * will definitely have no remaining references in any
 438 * CPU buffers at this point, because we use two lists,
 439 * and to have reached the list, it must have gone through
 440 * one full sync already.
 441 */
 442static void process_task_mortuary(void)
 443{
 444        unsigned long flags;
 445        LIST_HEAD(local_dead_tasks);
 446        struct task_struct *task;
 447        struct task_struct *ttask;
 448
 449        spin_lock_irqsave(&task_mortuary, flags);
 450
 451        list_splice_init(&dead_tasks, &local_dead_tasks);
 452        list_splice_init(&dying_tasks, &dead_tasks);
 453
 454        spin_unlock_irqrestore(&task_mortuary, flags);
 455
 456        list_for_each_entry_safe(task, ttask, &local_dead_tasks, tasks) {
 457                list_del(&task->tasks);
 458                free_task(task);
 459        }
 460}
 461
 462
 463static void mark_done(int cpu)
 464{
 465        int i;
 466
 467        cpumask_set_cpu(cpu, marked_cpus);
 468
 469        for_each_online_cpu(i) {
 470                if (!cpumask_test_cpu(i, marked_cpus))
 471                        return;
 472        }
 473
 474        /* All CPUs have been processed at least once,
 475         * we can process the mortuary once
 476         */
 477        process_task_mortuary();
 478
 479        cpumask_clear(marked_cpus);
 480}
 481
 482
 483/* FIXME: this is not sufficient if we implement syscall barrier backtrace
 484 * traversal, the code switch to sb_sample_start at first kernel enter/exit
 485 * switch so we need a fifth state and some special handling in sync_buffer()
 486 */
 487typedef enum {
 488        sb_bt_ignore = -2,
 489        sb_buffer_start,
 490        sb_bt_start,
 491        sb_sample_start,
 492} sync_buffer_state;
 493
 494/* Sync one of the CPU's buffers into the global event buffer.
 495 * Here we need to go through each batch of samples punctuated
 496 * by context switch notes, taking the task's mmap_sem and doing
 497 * lookup in task->mm->mmap to convert EIP into dcookie/offset
 498 * value.
 499 */
 500void sync_buffer(int cpu)
 501{
 502        struct mm_struct *mm = NULL;
 503        struct mm_struct *oldmm;
 504        unsigned long val;
 505        struct task_struct *new;
 506        unsigned long cookie = 0;
 507        int in_kernel = 1;
 508        sync_buffer_state state = sb_buffer_start;
 509        unsigned int i;
 510        unsigned long available;
 511        unsigned long flags;
 512        struct op_entry entry;
 513        struct op_sample *sample;
 514
 515        mutex_lock(&buffer_mutex);
 516
 517        add_cpu_switch(cpu);
 518
 519        op_cpu_buffer_reset(cpu);
 520        available = op_cpu_buffer_entries(cpu);
 521
 522        for (i = 0; i < available; ++i) {
 523                sample = op_cpu_buffer_read_entry(&entry, cpu);
 524                if (!sample)
 525                        break;
 526
 527                if (is_code(sample->eip)) {
 528                        flags = sample->event;
 529                        if (flags & TRACE_BEGIN) {
 530                                state = sb_bt_start;
 531                                add_trace_begin();
 532                        }
 533                        if (flags & KERNEL_CTX_SWITCH) {
 534                                /* kernel/userspace switch */
 535                                in_kernel = flags & IS_KERNEL;
 536                                if (state == sb_buffer_start)
 537                                        state = sb_sample_start;
 538                                add_kernel_ctx_switch(flags & IS_KERNEL);
 539                        }
 540                        if (flags & USER_CTX_SWITCH
 541                            && op_cpu_buffer_get_data(&entry, &val)) {
 542                                /* userspace context switch */
 543                                new = (struct task_struct *)val;
 544                                oldmm = mm;
 545                                release_mm(oldmm);
 546                                mm = take_tasks_mm(new);
 547                                if (mm != oldmm)
 548                                        cookie = get_exec_dcookie(mm);
 549                                add_user_ctx_switch(new, cookie);
 550                        }
 551                        if (op_cpu_buffer_get_size(&entry))
 552                                add_data(&entry, mm);
 553                        continue;
 554                }
 555
 556                if (state < sb_bt_start)
 557                        /* ignore sample */
 558                        continue;
 559
 560                if (add_sample(mm, sample, in_kernel))
 561                        continue;
 562
 563                /* ignore backtraces if failed to add a sample */
 564                if (state == sb_bt_start) {
 565                        state = sb_bt_ignore;
 566                        atomic_inc(&oprofile_stats.bt_lost_no_mapping);
 567                }
 568        }
 569        release_mm(mm);
 570
 571        mark_done(cpu);
 572
 573        mutex_unlock(&buffer_mutex);
 574}
 575
 576/* The function can be used to add a buffer worth of data directly to
 577 * the kernel buffer. The buffer is assumed to be a circular buffer.
 578 * Take the entries from index start and end at index end, wrapping
 579 * at max_entries.
 580 */
 581void oprofile_put_buff(unsigned long *buf, unsigned int start,
 582                       unsigned int stop, unsigned int max)
 583{
 584        int i;
 585
 586        i = start;
 587
 588        mutex_lock(&buffer_mutex);
 589        while (i != stop) {
 590                add_event_entry(buf[i++]);
 591
 592                if (i >= max)
 593                        i = 0;
 594        }
 595
 596        mutex_unlock(&buffer_mutex);
 597}
 598
 599
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