kernel/trace/ftrace.c

   1 /*
   2  * Infrastructure for profiling code inserted by 'gcc -pg'.
   3  *
   4  * Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
   5  * Copyright (C) 2004-2008 Ingo Molnar <mingo@redhat.com>
   6  *
   7  * Originally ported from the -rt patch by:
   8  *   Copyright (C) 2007 Arnaldo Carvalho de Melo <acme@redhat.com>
   9  *
  10  * Based on code in the latency_tracer, that is:
  11  *
  12  *  Copyright (C) 2004-2006 Ingo Molnar
  13  *  Copyright (C) 2004 William Lee Irwin III
  14  */
  15
  16 #include <linux/stop_machine.h>
  17 #include <linux/clocksource.h>
  18 #include <linux/kallsyms.h>
  19 #include <linux/seq_file.h>
  20 #include <linux/debugfs.h>
  21 #include <linux/hardirq.h>
  22 #include <linux/kthread.h>
  23 #include <linux/uaccess.h>
  24 #include <linux/kprobes.h>
  25 #include <linux/ftrace.h>
  26 #include <linux/sysctl.h>
  27 #include <linux/ctype.h>
  28 #include <linux/list.h>
  29
  30 #include <asm/ftrace.h>
  31
  32 #include "trace.h"
  33
  34 #define FTRACE_WARN_ON(cond)                    \
  35         do {                                    \
  36                 if (WARN_ON(cond))              \
  37                         ftrace_kill();          \
  38         } while (0)
  39
  40 #define FTRACE_WARN_ON_ONCE(cond)               \
  41         do {                                    \
  42                 if (WARN_ON_ONCE(cond))         \
  43                         ftrace_kill();          \
  44         } while (0)
  45
  46 /* ftrace_enabled is a method to turn ftrace on or off */
  47 int ftrace_enabled __read_mostly;
  48 static int last_ftrace_enabled;
  49
  50 /* Quick disabling of function tracer. */
  51 int function_trace_stop;
  52
  53 /*
  54  * ftrace_disabled is set when an anomaly is discovered.
  55  * ftrace_disabled is much stronger than ftrace_enabled.
  56  */
  57 static int ftrace_disabled __read_mostly;
  58
  59 static DEFINE_SPINLOCK(ftrace_lock);
  60 static DEFINE_MUTEX(ftrace_sysctl_lock);
  61
  62 static struct ftrace_ops ftrace_list_end __read_mostly =
  63 {
  64         .func = ftrace_stub,
  65 };
  66
  67 static struct ftrace_ops *ftrace_list __read_mostly = &ftrace_list_end;
  68 ftrace_func_t ftrace_trace_function __read_mostly = ftrace_stub;
  69 ftrace_func_t __ftrace_trace_function __read_mostly = ftrace_stub;
  70
  71 static void ftrace_list_func(unsigned long ip, unsigned long parent_ip)
  72 {
  73         struct ftrace_ops *op = ftrace_list;
  74
  75         /* in case someone actually ports this to alpha! */
  76         read_barrier_depends();
  77
  78         while (op != &ftrace_list_end) {
  79                 /* silly alpha */
  80                 read_barrier_depends();
  81                 op->func(ip, parent_ip);
  82                 op = op->next;
  83         };
  84 }
  85
  86 /**
  87  * clear_ftrace_function - reset the ftrace function
  88  *
  89  * This NULLs the ftrace function and in essence stops
  90  * tracing.  There may be lag
  91  */
  92 void clear_ftrace_function(void)
  93 {
  94         ftrace_trace_function = ftrace_stub;
  95         __ftrace_trace_function = ftrace_stub;
  96 }
  97
  98 #ifndef CONFIG_HAVE_FUNCTION_TRACE_MCOUNT_TEST
  99 /*
 100  * For those archs that do not test ftrace_trace_stop in their
 101  * mcount call site, we need to do it from C.
 102  */
 103 static void ftrace_test_stop_func(unsigned long ip, unsigned long parent_ip)
 104 {
 105         if (function_trace_stop)
 106                 return;
 107
 108         __ftrace_trace_function(ip, parent_ip);
 109 }
 110 #endif
 111
 112 static int __register_ftrace_function(struct ftrace_ops *ops)
 113 {
 114         /* should not be called from interrupt context */
 115         spin_lock(&ftrace_lock);
 116
 117         ops->next = ftrace_list;
 118         /*
 119          * We are entering ops into the ftrace_list but another
 120          * CPU might be walking that list. We need to make sure
 121          * the ops->next pointer is valid before another CPU sees
 122          * the ops pointer included into the ftrace_list.
 123          */
 124         smp_wmb();
 125         ftrace_list = ops;
 126
 127         if (ftrace_enabled) {
 128                 /*
 129                  * For one func, simply call it directly.
 130                  * For more than one func, call the chain.
 131                  */
 132 #ifdef CONFIG_HAVE_FUNCTION_TRACE_MCOUNT_TEST
 133                 if (ops->next == &ftrace_list_end)
 134                         ftrace_trace_function = ops->func;
 135                 else
 136                         ftrace_trace_function = ftrace_list_func;
 137 #else
 138                 if (ops->next == &ftrace_list_end)
 139                         __ftrace_trace_function = ops->func;
 140                 else
 141                         __ftrace_trace_function = ftrace_list_func;
 142                 ftrace_trace_function = ftrace_test_stop_func;
 143 #endif
 144         }
 145
 146         spin_unlock(&ftrace_lock);
 147
 148         return 0;
 149 }
 150
 151 static int __unregister_ftrace_function(struct ftrace_ops *ops)
 152 {
 153         struct ftrace_ops **p;
 154         int ret = 0;
 155
 156         /* should not be called from interrupt context */
 157         spin_lock(&ftrace_lock);
 158
 159         /*
 160          * If we are removing the last function, then simply point
 161          * to the ftrace_stub.
 162          */
 163         if (ftrace_list == ops && ops->next == &ftrace_list_end) {
 164                 ftrace_trace_function = ftrace_stub;
 165                 ftrace_list = &ftrace_list_end;
 166                 goto out;
 167         }
 168
 169         for (p = &ftrace_list; *p != &ftrace_list_end; p = &(*p)->next)
 170                 if (*p == ops)
 171                         break;
 172
 173         if (*p != ops) {
 174                 ret = -1;
 175                 goto out;
 176         }
 177
 178         *p = (*p)->next;
 179
 180         if (ftrace_enabled) {
 181                 /* If we only have one func left, then call that directly */
 182                 if (ftrace_list->next == &ftrace_list_end)
 183                         ftrace_trace_function = ftrace_list->func;
 184         }
 185
 186  out:
 187         spin_unlock(&ftrace_lock);
 188
 189         return ret;
 190 }
 191
 192 #ifdef CONFIG_DYNAMIC_FTRACE
 193 #ifndef CONFIG_FTRACE_MCOUNT_RECORD
 194 # error Dynamic ftrace depends on MCOUNT_RECORD
 195 #endif
 196
 197 /*
 198  * Since MCOUNT_ADDR may point to mcount itself, we do not want
 199  * to get it confused by reading a reference in the code as we
 200  * are parsing on objcopy output of text. Use a variable for
 201  * it instead.
 202  */
 203 static unsigned long mcount_addr = MCOUNT_ADDR;
 204
 205 enum {
 206         FTRACE_ENABLE_CALLS             = (1 << 0),
 207         FTRACE_DISABLE_CALLS            = (1 << 1),
 208         FTRACE_UPDATE_TRACE_FUNC        = (1 << 2),
 209         FTRACE_ENABLE_MCOUNT            = (1 << 3),
 210         FTRACE_DISABLE_MCOUNT           = (1 << 4),
 211 };
 212
 213 static int ftrace_filtered;
 214
 215 static LIST_HEAD(ftrace_new_addrs);
 216
 217 static DEFINE_MUTEX(ftrace_regex_lock);
 218
 219 struct ftrace_page {
 220         struct ftrace_page      *next;
 221         unsigned long           index;
 222         struct dyn_ftrace       records[];
 223 };
 224
 225 #define ENTRIES_PER_PAGE \
 226   ((PAGE_SIZE - sizeof(struct ftrace_page)) / sizeof(struct dyn_ftrace))
 227
 228 /* estimate from running different kernels */
 229 #define NR_TO_INIT              10000
 230
 231 static struct ftrace_page       *ftrace_pages_start;
 232 static struct ftrace_page       *ftrace_pages;
 233
 234 static struct dyn_ftrace *ftrace_free_records;
 235
 236
 237 #ifdef CONFIG_KPROBES
 238
 239 static int frozen_record_count;
 240
 241 static inline void freeze_record(struct dyn_ftrace *rec)
 242 {
 243         if (!(rec->flags & FTRACE_FL_FROZEN)) {
 244                 rec->flags |= FTRACE_FL_FROZEN;
 245                 frozen_record_count++;
 246         }
 247 }
 248
 249 static inline void unfreeze_record(struct dyn_ftrace *rec)
 250 {
 251         if (rec->flags & FTRACE_FL_FROZEN) {
 252                 rec->flags &= ~FTRACE_FL_FROZEN;
 253                 frozen_record_count--;
 254         }
 255 }
 256
 257 static inline int record_frozen(struct dyn_ftrace *rec)
 258 {
 259         return rec->flags & FTRACE_FL_FROZEN;
 260 }
 261 #else
 262 # define freeze_record(rec)                     ({ 0; })
 263 # define unfreeze_record(rec)                   ({ 0; })
 264 # define record_frozen(rec)                     ({ 0; })
 265 #endif /* CONFIG_KPROBES */
 266
 267 static void ftrace_free_rec(struct dyn_ftrace *rec)
 268 {
 269         rec->ip = (unsigned long)ftrace_free_records;
 270         ftrace_free_records = rec;
 271         rec->flags |= FTRACE_FL_FREE;
 272 }
 273
 274 void ftrace_release(void *start, unsigned long size)
 275 {
 276         struct dyn_ftrace *rec;
 277         struct ftrace_page *pg;
 278         unsigned long s = (unsigned long)start;
 279         unsigned long e = s + size;
 280         int i;
 281
 282         if (ftrace_disabled || !start)
 283                 return;
 284
 285         /* should not be called from interrupt context */
 286         spin_lock(&ftrace_lock);
 287
 288         for (pg = ftrace_pages_start; pg; pg = pg->next) {
 289                 for (i = 0; i < pg->index; i++) {
 290                         rec = &pg->records[i];
 291
 292                         if ((rec->ip >= s) && (rec->ip < e))
 293                                 ftrace_free_rec(rec);
 294                 }
 295         }
 296         spin_unlock(&ftrace_lock);
 297 }
 298
 299 static struct dyn_ftrace *ftrace_alloc_dyn_node(unsigned long ip)
 300 {
 301         struct dyn_ftrace *rec;
 302
 303         /* First check for freed records */
 304         if (ftrace_free_records) {
 305                 rec = ftrace_free_records;
 306
 307                 if (unlikely(!(rec->flags & FTRACE_FL_FREE))) {
 308                         FTRACE_WARN_ON_ONCE(1);
 309                         ftrace_free_records = NULL;
 310                         return NULL;
 311                 }
 312
 313                 ftrace_free_records = (void *)rec->ip;
 314                 memset(rec, 0, sizeof(*rec));
 315                 return rec;
 316         }
 317
 318         if (ftrace_pages->index == ENTRIES_PER_PAGE) {
 319                 if (!ftrace_pages->next) {
 320                         /* allocate another page */
 321                         ftrace_pages->next =
 322                                 (void *)get_zeroed_page(GFP_KERNEL);
 323                         if (!ftrace_pages->next)
 324                                 return NULL;
 325                 }
 326                 ftrace_pages = ftrace_pages->next;
 327         }
 328
 329         return &ftrace_pages->records[ftrace_pages->index++];
 330 }
 331
 332 static struct dyn_ftrace *
 333 ftrace_record_ip(unsigned long ip)
 334 {
 335         struct dyn_ftrace *rec;
 336
 337         if (ftrace_disabled)
 338                 return NULL;
 339
 340         rec = ftrace_alloc_dyn_node(ip);
 341         if (!rec)
 342                 return NULL;
 343
 344         rec->ip = ip;
 345
 346         list_add(&rec->list, &ftrace_new_addrs);
 347
 348         return rec;
 349 }
 350
 351 static void print_ip_ins(const char *fmt, unsigned char *p)
 352 {
 353         int i;
 354
 355         printk(KERN_CONT "%s", fmt);
 356
 357         for (i = 0; i < MCOUNT_INSN_SIZE; i++)
 358                 printk(KERN_CONT "%s%02x", i ? ":" : "", p[i]);
 359 }
 360
 361 static void ftrace_bug(int failed, unsigned long ip,
 362                        unsigned char *expected,
 363                        unsigned char *replace)
 364 {
 365         switch (failed) {
 366         case -EFAULT:
 367                 FTRACE_WARN_ON_ONCE(1);
 368                 pr_info("ftrace faulted on modifying ");
 369                 print_ip_sym(ip);
 370                 break;
 371         case -EINVAL:
 372                 FTRACE_WARN_ON_ONCE(1);
 373                 pr_info("ftrace failed to modify ");
 374                 print_ip_sym(ip);
 375                 print_ip_ins(" expected: ", expected);
 376                 print_ip_ins(" actual: ", (unsigned char *)ip);
 377                 print_ip_ins(" replace: ", replace);
 378                 printk(KERN_CONT "\n");
 379                 break;
 380         case -EPERM:
 381                 FTRACE_WARN_ON_ONCE(1);
 382                 pr_info("ftrace faulted on writing ");
 383                 print_ip_sym(ip);
 384                 break;
 385         default:
 386                 FTRACE_WARN_ON_ONCE(1);
 387                 pr_info("ftrace faulted on unknown error ");
 388                 print_ip_sym(ip);
 389         }
 390 }
 391
 392 #define FTRACE_ADDR ((long)(ftrace_caller))
 393
 394 static int
 395 __ftrace_replace_code(struct dyn_ftrace *rec,
 396                       unsigned char *old, unsigned char *new, int enable)
 397 {
 398         unsigned long ip, fl;
 399
 400         ip = rec->ip;
 401
 402         if (ftrace_filtered && enable) {
 403                 /*
 404                  * If filtering is on:
 405                  *
 406                  * If this record is set to be filtered and
 407                  * is enabled then do nothing.
 408                  *
 409                  * If this record is set to be filtered and
 410                  * it is not enabled, enable it.
 411                  *
 412                  * If this record is not set to be filtered
 413                  * and it is not enabled do nothing.
 414                  *
 415                  * If this record is set not to trace then
 416                  * do nothing.
 417                  *
 418                  * If this record is set not to trace and
 419                  * it is enabled then disable it.
 420                  *
 421                  * If this record is not set to be filtered and
 422                  * it is enabled, disable it.
 423                  */
 424
 425                 fl = rec->flags & (FTRACE_FL_FILTER | FTRACE_FL_NOTRACE |
 426                                    FTRACE_FL_ENABLED);
 427
 428                 if ((fl ==  (FTRACE_FL_FILTER | FTRACE_FL_ENABLED)) ||
 429                     (fl ==  (FTRACE_FL_FILTER | FTRACE_FL_NOTRACE)) ||
 430                     !fl || (fl == FTRACE_FL_NOTRACE))
 431                         return 0;
 432
 433                 /*
 434                  * If it is enabled disable it,
 435                  * otherwise enable it!
 436                  */
 437                 if (fl & FTRACE_FL_ENABLED) {
 438                         /* swap new and old */
 439                         new = old;
 440                         old = ftrace_call_replace(ip, FTRACE_ADDR);
 441                         rec->flags &= ~FTRACE_FL_ENABLED;
 442                 } else {
 443                         new = ftrace_call_replace(ip, FTRACE_ADDR);
 444                         rec->flags |= FTRACE_FL_ENABLED;
 445                 }
 446         } else {
 447
 448                 if (enable) {
 449                         /*
 450                          * If this record is set not to trace and is
 451                          * not enabled, do nothing.
 452                          */
 453                         fl = rec->flags & (FTRACE_FL_NOTRACE | FTRACE_FL_ENABLED);
 454                         if (fl == FTRACE_FL_NOTRACE)
 455                                 return 0;
 456
 457                         new = ftrace_call_replace(ip, FTRACE_ADDR);
 458                 } else
 459                         old = ftrace_call_replace(ip, FTRACE_ADDR);
 460
 461                 if (enable) {
 462                         if (rec->flags & FTRACE_FL_ENABLED)
 463                                 return 0;
 464                         rec->flags |= FTRACE_FL_ENABLED;
 465                 } else {
 466                         if (!(rec->flags & FTRACE_FL_ENABLED))
 467                                 return 0;
 468                         rec->flags &= ~FTRACE_FL_ENABLED;
 469                 }
 470         }
 471
 472         return ftrace_modify_code(ip, old, new);
 473 }
 474
 475 static void ftrace_replace_code(int enable)
 476 {
 477         int i, failed;
 478         unsigned char *new = NULL, *old = NULL;
 479         struct dyn_ftrace *rec;
 480         struct ftrace_page *pg;
 481
 482         if (enable)
 483                 old = ftrace_nop_replace();
 484         else
 485                 new = ftrace_nop_replace();
 486
 487         for (pg = ftrace_pages_start; pg; pg = pg->next) {
 488                 for (i = 0; i < pg->index; i++) {
 489                         rec = &pg->records[i];
 490
 491                         /*
 492                          * Skip over free records and records that have
 493                          * failed.
 494                          */
 495                         if (rec->flags & FTRACE_FL_FREE ||
 496                             rec->flags & FTRACE_FL_FAILED)
 497                                 continue;
 498
 499                         /* ignore updates to this record's mcount site */
 500                         if (get_kprobe((void *)rec->ip)) {
 501                                 freeze_record(rec);
 502                                 continue;
 503                         } else {
 504                                 unfreeze_record(rec);
 505                         }
 506
 507                         failed = __ftrace_replace_code(rec, old, new, enable);
 508                         if (failed && (rec->flags & FTRACE_FL_CONVERTED)) {
 509                                 rec->flags |= FTRACE_FL_FAILED;
 510                                 if ((system_state == SYSTEM_BOOTING) ||
 511                                     !core_kernel_text(rec->ip)) {
 512                                         ftrace_free_rec(rec);
 513                                 } else
 514                                         ftrace_bug(failed, rec->ip, old, new);
 515                         }
 516                 }
 517         }
 518 }
 519
 520 static int
 521 ftrace_code_disable(struct dyn_ftrace *rec)
 522 {
 523         unsigned long ip;
 524         unsigned char *nop, *call;
 525         int ret;
 526
 527         ip = rec->ip;
 528
 529         nop = ftrace_nop_replace();
 530         call = ftrace_call_replace(ip, mcount_addr);
 531
 532         ret = ftrace_modify_code(ip, call, nop);
 533         if (ret) {
 534                 ftrace_bug(ret, ip, call, nop);
 535                 rec->flags |= FTRACE_FL_FAILED;
 536                 return 0;
 537         }
 538         return 1;
 539 }
 540
 541 static int __ftrace_modify_code(void *data)
 542 {
 543         int *command = data;
 544
 545         if (*command & FTRACE_ENABLE_CALLS)
 546                 ftrace_replace_code(1);
 547         else if (*command & FTRACE_DISABLE_CALLS)
 548                 ftrace_replace_code(0);
 549
 550         if (*command & FTRACE_UPDATE_TRACE_FUNC)
 551                 ftrace_update_ftrace_func(ftrace_trace_function);
 552
 553         return 0;
 554 }
 555
 556 static void ftrace_run_update_code(int command)
 557 {
 558         stop_machine(__ftrace_modify_code, &command, NULL);
 559 }
 560
 561 static ftrace_func_t saved_ftrace_func;
 562 static int ftrace_start_up;
 563 static DEFINE_MUTEX(ftrace_start_lock);
 564
 565 static void ftrace_startup(void)
 566 {
 567         int command = 0;
 568
 569         if (unlikely(ftrace_disabled))
 570                 return;
 571
 572         mutex_lock(&ftrace_start_lock);
 573         ftrace_start_up++;
 574         if (ftrace_start_up == 1)
 575                 command |= FTRACE_ENABLE_CALLS;
 576
 577         if (saved_ftrace_func != ftrace_trace_function) {
 578                 saved_ftrace_func = ftrace_trace_function;
 579                 command |= FTRACE_UPDATE_TRACE_FUNC;
 580         }
 581
 582         if (!command || !ftrace_enabled)
 583                 goto out;
 584
 585         ftrace_run_update_code(command);
 586  out:
 587         mutex_unlock(&ftrace_start_lock);
 588 }
 589
 590 static void ftrace_shutdown(void)
 591 {
 592         int command = 0;
 593
 594         if (unlikely(ftrace_disabled))
 595                 return;
 596
 597         mutex_lock(&ftrace_start_lock);
 598         ftrace_start_up--;
 599         if (!ftrace_start_up)
 600                 command |= FTRACE_DISABLE_CALLS;
 601
 602         if (saved_ftrace_func != ftrace_trace_function) {
 603                 saved_ftrace_func = ftrace_trace_function;
 604                 command |= FTRACE_UPDATE_TRACE_FUNC;
 605         }
 606
 607         if (!command || !ftrace_enabled)
 608                 goto out;
 609
 610         ftrace_run_update_code(command);
 611  out:
 612         mutex_unlock(&ftrace_start_lock);
 613 }
 614
 615 static void ftrace_startup_sysctl(void)
 616 {
 617         int command = FTRACE_ENABLE_MCOUNT;
 618
 619         if (unlikely(ftrace_disabled))
 620                 return;
 621
 622         mutex_lock(&ftrace_start_lock);
 623         /* Force update next time */
 624         saved_ftrace_func = NULL;
 625         /* ftrace_start_up is true if we want ftrace running */
 626         if (ftrace_start_up)
 627                 command |= FTRACE_ENABLE_CALLS;
 628
 629         ftrace_run_update_code(command);
 630         mutex_unlock(&ftrace_start_lock);
 631 }
 632
 633 static void ftrace_shutdown_sysctl(void)
 634 {
 635         int command = FTRACE_DISABLE_MCOUNT;
 636
 637         if (unlikely(ftrace_disabled))
 638                 return;
 639
 640         mutex_lock(&ftrace_start_lock);
 641         /* ftrace_start_up is true if ftrace is running */
 642         if (ftrace_start_up)
 643                 command |= FTRACE_DISABLE_CALLS;
 644
 645         ftrace_run_update_code(command);
 646         mutex_unlock(&ftrace_start_lock);
 647 }
 648
 649 static cycle_t          ftrace_update_time;
 650 static unsigned long    ftrace_update_cnt;
 651 unsigned long           ftrace_update_tot_cnt;
 652
 653 static int ftrace_update_code(void)
 654 {
 655         struct dyn_ftrace *p, *t;
 656         cycle_t start, stop;
 657
 658         start = ftrace_now(raw_smp_processor_id());
 659         ftrace_update_cnt = 0;
 660
 661         list_for_each_entry_safe(p, t, &ftrace_new_addrs, list) {
 662
 663                 /* If something went wrong, bail without enabling anything */
 664                 if (unlikely(ftrace_disabled))
 665                         return -1;
 666
 667                 list_del_init(&p->list);
 668
 669                 /* convert record (i.e, patch mcount-call with NOP) */
 670                 if (ftrace_code_disable(p)) {
 671                         p->flags |= FTRACE_FL_CONVERTED;
 672                         ftrace_update_cnt++;
 673                 } else
 674                         ftrace_free_rec(p);
 675         }
 676
 677         stop = ftrace_now(raw_smp_processor_id());
 678         ftrace_update_time = stop - start;
 679         ftrace_update_tot_cnt += ftrace_update_cnt;
 680
 681         return 0;
 682 }
 683
 684 static int __init ftrace_dyn_table_alloc(unsigned long num_to_init)
 685 {
 686         struct ftrace_page *pg;
 687         int cnt;
 688         int i;
 689
 690         /* allocate a few pages */
 691         ftrace_pages_start = (void *)get_zeroed_page(GFP_KERNEL);
 692         if (!ftrace_pages_start)
 693                 return -1;
 694
 695         /*
 696          * Allocate a few more pages.
 697          *
 698          * TODO: have some parser search vmlinux before
 699          *   final linking to find all calls to ftrace.
 700          *   Then we can:
 701          *    a) know how many pages to allocate.
 702          *     and/or
 703          *    b) set up the table then.
 704          *
 705          *  The dynamic code is still necessary for
 706          *  modules.
 707          */
 708
 709         pg = ftrace_pages = ftrace_pages_start;
 710
 711         cnt = num_to_init / ENTRIES_PER_PAGE;
 712         pr_info("ftrace: allocating %ld entries in %d pages\n",
 713                 num_to_init, cnt);
 714
 715         for (i = 0; i < cnt; i++) {
 716                 pg->next = (void *)get_zeroed_page(GFP_KERNEL);
 717
 718                 /* If we fail, we'll try later anyway */
 719                 if (!pg->next)
 720                         break;
 721
 722                 pg = pg->next;
 723         }
 724
 725         return 0;
 726 }
 727
 728 enum {
 729         FTRACE_ITER_FILTER      = (1 << 0),
 730         FTRACE_ITER_CONT        = (1 << 1),
 731         FTRACE_ITER_NOTRACE     = (1 << 2),
 732         FTRACE_ITER_FAILURES    = (1 << 3),
 733 };
 734
 735 #define FTRACE_BUFF_MAX (KSYM_SYMBOL_LEN+4) /* room for wildcards */
 736
 737 struct ftrace_iterator {
 738         loff_t                  pos;
 739         struct ftrace_page      *pg;
 740         unsigned                idx;
 741         unsigned                flags;
 742         unsigned char           buffer[FTRACE_BUFF_MAX+1];
 743         unsigned                buffer_idx;
 744         unsigned                filtered;
 745 };
 746
 747 static void *
 748 t_next(struct seq_file *m, void *v, loff_t *pos)
 749 {
 750         struct ftrace_iterator *iter = m->private;
 751         struct dyn_ftrace *rec = NULL;
 752
 753         (*pos)++;
 754
 755         /* should not be called from interrupt context */
 756         spin_lock(&ftrace_lock);
 757  retry:
 758         if (iter->idx >= iter->pg->index) {
 759                 if (iter->pg->next) {
 760                         iter->pg = iter->pg->next;
 761                         iter->idx = 0;
 762                         goto retry;
 763                 }
 764         } else {
 765                 rec = &iter->pg->records[iter->idx++];
 766                 if ((rec->flags & FTRACE_FL_FREE) ||
 767
 768                     (!(iter->flags & FTRACE_ITER_FAILURES) &&
 769                      (rec->flags & FTRACE_FL_FAILED)) ||
 770
 771                     ((iter->flags & FTRACE_ITER_FAILURES) &&
 772                      !(rec->flags & FTRACE_FL_FAILED)) ||
 773
 774                     ((iter->flags & FTRACE_ITER_FILTER) &&
 775                      !(rec->flags & FTRACE_FL_FILTER)) ||
 776
 777                     ((iter->flags & FTRACE_ITER_NOTRACE) &&
 778                      !(rec->flags & FTRACE_FL_NOTRACE))) {
 779                         rec = NULL;
 780                         goto retry;
 781                 }
 782         }
 783         spin_unlock(&ftrace_lock);
 784
 785         iter->pos = *pos;
 786
 787         return rec;
 788 }
 789
 790 static void *t_start(struct seq_file *m, loff_t *pos)
 791 {
 792         struct ftrace_iterator *iter = m->private;
 793         void *p = NULL;
 794         loff_t l = -1;
 795
 796         if (*pos != iter->pos) {
 797                 for (p = t_next(m, p, &l); p && l < *pos; p = t_next(m, p, &l))
 798                         ;
 799         } else {
 800                 l = *pos;
 801                 p = t_next(m, p, &l);
 802         }
 803
 804         return p;
 805 }
 806
 807 static void t_stop(struct seq_file *m, void *p)
 808 {
 809 }
 810
 811 static int t_show(struct seq_file *m, void *v)
 812 {
 813         struct dyn_ftrace *rec = v;
 814         char str[KSYM_SYMBOL_LEN];
 815
 816         if (!rec)
 817                 return 0;
 818
 819         kallsyms_lookup(rec->ip, NULL, NULL, NULL, str);
 820
 821         seq_printf(m, "%s\n", str);
 822
 823         return 0;
 824 }
 825
 826 static struct seq_operations show_ftrace_seq_ops = {
 827         .start = t_start,
 828         .next = t_next,
 829         .stop = t_stop,
 830         .show = t_show,
 831 };
 832
 833 static int
 834 ftrace_avail_open(struct inode *inode, struct file *file)
 835 {
 836         struct ftrace_iterator *iter;
 837         int ret;
 838
 839         if (unlikely(ftrace_disabled))
 840                 return -ENODEV;
 841
 842         iter = kzalloc(sizeof(*iter), GFP_KERNEL);
 843         if (!iter)
 844                 return -ENOMEM;
 845
 846         iter->pg = ftrace_pages_start;
 847         iter->pos = -1;
 848
 849         ret = seq_open(file, &show_ftrace_seq_ops);
 850         if (!ret) {
 851                 struct seq_file *m = file->private_data;
 852
 853                 m->private = iter;
 854         } else {
 855                 kfree(iter);
 856         }
 857
 858         return ret;
 859 }
 860
 861 int ftrace_avail_release(struct inode *inode, struct file *file)
 862 {
 863         struct seq_file *m = (struct seq_file *)file->private_data;
 864         struct ftrace_iterator *iter = m->private;
 865
 866         seq_release(inode, file);
 867         kfree(iter);
 868
 869         return 0;
 870 }
 871
 872 static int
 873 ftrace_failures_open(struct inode *inode, struct file *file)
 874 {
 875         int ret;
 876         struct seq_file *m;
 877         struct ftrace_iterator *iter;
 878
 879         ret = ftrace_avail_open(inode, file);
 880         if (!ret) {
 881                 m = (struct seq_file *)file->private_data;
 882                 iter = (struct ftrace_iterator *)m->private;
 883                 iter->flags = FTRACE_ITER_FAILURES;
 884         }
 885
 886         return ret;
 887 }
 888
 889
 890 static void ftrace_filter_reset(int enable)
 891 {
 892         struct ftrace_page *pg;
 893         struct dyn_ftrace *rec;
 894         unsigned long type = enable ? FTRACE_FL_FILTER : FTRACE_FL_NOTRACE;
 895         unsigned i;
 896
 897         /* should not be called from interrupt context */
 898         spin_lock(&ftrace_lock);
 899         if (enable)
 900                 ftrace_filtered = 0;
 901         pg = ftrace_pages_start;
 902         while (pg) {
 903                 for (i = 0; i < pg->index; i++) {
 904                         rec = &pg->records[i];
 905                         if (rec->flags & FTRACE_FL_FAILED)
 906                                 continue;
 907                         rec->flags &= ~type;
 908                 }
 909                 pg = pg->next;
 910         }
 911         spin_unlock(&ftrace_lock);
 912 }
 913
 914 static int
 915 ftrace_regex_open(struct inode *inode, struct file *file, int enable)
 916 {
 917         struct ftrace_iterator *iter;
 918         int ret = 0;
 919
 920         if (unlikely(ftrace_disabled))
 921                 return -ENODEV;
 922
 923         iter = kzalloc(sizeof(*iter), GFP_KERNEL);
 924         if (!iter)
 925                 return -ENOMEM;
 926
 927         mutex_lock(&ftrace_regex_lock);
 928         if ((file->f_mode & FMODE_WRITE) &&
 929             !(file->f_flags & O_APPEND))
 930                 ftrace_filter_reset(enable);
 931
 932         if (file->f_mode & FMODE_READ) {
 933                 iter->pg = ftrace_pages_start;
 934                 iter->pos = -1;
 935                 iter->flags = enable ? FTRACE_ITER_FILTER :
 936                         FTRACE_ITER_NOTRACE;
 937
 938                 ret = seq_open(file, &show_ftrace_seq_ops);
 939                 if (!ret) {
 940                         struct seq_file *m = file->private_data;
 941                         m->private = iter;
 942                 } else
 943                         kfree(iter);
 944         } else
 945                 file->private_data = iter;
 946         mutex_unlock(&ftrace_regex_lock);
 947
 948         return ret;
 949 }
 950
 951 static int
 952 ftrace_filter_open(struct inode *inode, struct file *file)
 953 {
 954         return ftrace_regex_open(inode, file, 1);
 955 }
 956
 957 static int
 958 ftrace_notrace_open(struct inode *inode, struct file *file)
 959 {
 960         return ftrace_regex_open(inode, file, 0);
 961 }
 962
 963 static ssize_t
 964 ftrace_regex_read(struct file *file, char __user *ubuf,
 965                        size_t cnt, loff_t *ppos)
 966 {
 967         if (file->f_mode & FMODE_READ)
 968                 return seq_read(file, ubuf, cnt, ppos);
 969         else
 970                 return -EPERM;
 971 }
 972
 973 static loff_t
 974 ftrace_regex_lseek(struct file *file, loff_t offset, int origin)
 975 {
 976         loff_t ret;
 977
 978         if (file->f_mode & FMODE_READ)
 979                 ret = seq_lseek(file, offset, origin);
 980         else
 981                 file->f_pos = ret = 1;
 982
 983         return ret;
 984 }
 985
 986 enum {
 987         MATCH_FULL,
 988         MATCH_FRONT_ONLY,
 989         MATCH_MIDDLE_ONLY,
 990         MATCH_END_ONLY,
 991 };
 992
 993 static void
 994 ftrace_match(unsigned char *buff, int len, int enable)
 995 {
 996         char str[KSYM_SYMBOL_LEN];
 997         char *search = NULL;
 998         struct ftrace_page *pg;
 999         struct dyn_ftrace *rec;
1000         int type = MATCH_FULL;
1001         unsigned long flag = enable ? FTRACE_FL_FILTER : FTRACE_FL_NOTRACE;
1002         unsigned i, match = 0, search_len = 0;
1003
1004         for (i = 0; i < len; i++) {
1005                 if (buff[i] == '*') {
1006                         if (!i) {
1007                                 search = buff + i + 1;
1008                                 type = MATCH_END_ONLY;
1009                                 search_len = len - (i + 1);
1010                         } else {
1011                                 if (type == MATCH_END_ONLY) {
1012                                         type = MATCH_MIDDLE_ONLY;
1013                                 } else {
1014                                         match = i;
1015                                         type = MATCH_FRONT_ONLY;
1016                                 }
1017                                 buff[i] = 0;
1018                                 break;
1019                         }
1020                 }
1021         }
1022
1023         /* should not be called from interrupt context */
1024         spin_lock(&ftrace_lock);
1025         if (enable)
1026                 ftrace_filtered = 1;
1027         pg = ftrace_pages_start;
1028         while (pg) {
1029                 for (i = 0; i < pg->index; i++) {
1030                         int matched = 0;
1031                         char *ptr;
1032
1033                         rec = &pg->records[i];
1034                         if (rec->flags & FTRACE_FL_FAILED)
1035                                 continue;
1036                         kallsyms_lookup(rec->ip, NULL, NULL, NULL, str);
1037                         switch (type) {
1038                         case MATCH_FULL:
1039                                 if (strcmp(str, buff) == 0)
1040                                         matched = 1;
1041                                 break;
1042                         case MATCH_FRONT_ONLY:
1043                                 if (memcmp(str, buff, match) == 0)
1044                                         matched = 1;
1045                                 break;
1046                         case MATCH_MIDDLE_ONLY:
1047                                 if (strstr(str, search))
1048                                         matched = 1;
1049                                 break;
1050                         case MATCH_END_ONLY:
1051                                 ptr = strstr(str, search);
1052                                 if (ptr && (ptr[search_len] == 0))
1053                                         matched = 1;
1054                                 break;
1055                         }
1056                         if (matched)
1057                                 rec->flags |= flag;
1058                 }
1059                 pg = pg->next;
1060         }
1061         spin_unlock(&ftrace_lock);
1062 }
1063
1064 static ssize_t
1065 ftrace_regex_write(struct file *file, const char __user *ubuf,
1066                    size_t cnt, loff_t *ppos, int enable)
1067 {
1068         struct ftrace_iterator *iter;
1069         char ch;
1070         size_t read = 0;
1071         ssize_t ret;
1072
1073         if (!cnt || cnt < 0)
1074                 return 0;
1075
1076         mutex_lock(&ftrace_regex_lock);
1077
1078         if (file->f_mode & FMODE_READ) {
1079                 struct seq_file *m = file->private_data;
1080                 iter = m->private;
1081         } else
1082                 iter = file->private_data;
1083
1084         if (!*ppos) {
1085                 iter->flags &= ~FTRACE_ITER_CONT;
1086                 iter->buffer_idx = 0;
1087         }
1088
1089         ret = get_user(ch, ubuf++);
1090         if (ret)
1091                 goto out;
1092         read++;
1093         cnt--;
1094
1095         if (!(iter->flags & ~FTRACE_ITER_CONT)) {
1096                 /* skip white space */
1097                 while (cnt && isspace(ch)) {
1098                         ret = get_user(ch, ubuf++);
1099                         if (ret)
1100                                 goto out;
1101                         read++;
1102                         cnt--;
1103                 }
1104
1105                 if (isspace(ch)) {
1106                         file->f_pos += read;
1107                         ret = read;
1108                         goto out;
1109                 }
1110
1111                 iter->buffer_idx = 0;
1112         }
1113
1114         while (cnt && !isspace(ch)) {
1115                 if (iter->buffer_idx < FTRACE_BUFF_MAX)
1116                         iter->buffer[iter->buffer_idx++] = ch;
1117                 else {
1118                         ret = -EINVAL;
1119                         goto out;
1120                 }
1121                 ret = get_user(ch, ubuf++);
1122                 if (ret)
1123                         goto out;
1124                 read++;
1125                 cnt--;
1126         }
1127
1128         if (isspace(ch)) {
1129                 iter->filtered++;
1130                 iter->buffer[iter->buffer_idx] = 0;
1131                 ftrace_match(iter->buffer, iter->buffer_idx, enable);
1132                 iter->buffer_idx = 0;
1133         } else
1134                 iter->flags |= FTRACE_ITER_CONT;
1135
1136
1137         file->f_pos += read;
1138
1139         ret = read;
1140  out:
1141         mutex_unlock(&ftrace_regex_lock);
1142
1143         return ret;
1144 }
1145
1146 static ssize_t
1147 ftrace_filter_write(struct file *file, const char __user *ubuf,
1148                     size_t cnt, loff_t *ppos)
1149 {
1150         return ftrace_regex_write(file, ubuf, cnt, ppos, 1);
1151 }
1152
1153 static ssize_t
1154 ftrace_notrace_write(struct file *file, const char __user *ubuf,
1155                      size_t cnt, loff_t *ppos)
1156 {
1157         return ftrace_regex_write(file, ubuf, cnt, ppos, 0);
1158 }
1159
1160 static void
1161 ftrace_set_regex(unsigned char *buf, int len, int reset, int enable)
1162 {
1163         if (unlikely(ftrace_disabled))
1164                 return;
1165
1166         mutex_lock(&ftrace_regex_lock);
1167         if (reset)
1168                 ftrace_filter_reset(enable);
1169         if (buf)
1170                 ftrace_match(buf, len, enable);
1171         mutex_unlock(&ftrace_regex_lock);
1172 }
1173
1174 /**
1175  * ftrace_set_filter - set a function to filter on in ftrace
1176  * @buf - the string that holds the function filter text.
1177  * @len - the length of the string.
1178  * @reset - non zero to reset all filters before applying this filter.
1179  *
1180  * Filters denote which functions should be enabled when tracing is enabled.
1181  * If @buf is NULL and reset is set, all functions will be enabled for tracing.
1182  */
1183 void ftrace_set_filter(unsigned char *buf, int len, int reset)
1184 {
1185         ftrace_set_regex(buf, len, reset, 1);
1186 }
1187
1188 /**
1189  * ftrace_set_notrace - set a function to not trace in ftrace
1190  * @buf - the string that holds the function notrace text.
1191  * @len - the length of the string.
1192  * @reset - non zero to reset all filters before applying this filter.
1193  *
1194  * Notrace Filters denote which functions should not be enabled when tracing
1195  * is enabled. If @buf is NULL and reset is set, all functions will be enabled
1196  * for tracing.
1197  */
1198 void ftrace_set_notrace(unsigned char *buf, int len, int reset)
1199 {
1200         ftrace_set_regex(buf, len, reset, 0);
1201 }
1202
1203 static int
1204 ftrace_regex_release(struct inode *inode, struct file *file, int enable)
1205 {
1206         struct seq_file *m = (struct seq_file *)file->private_data;
1207         struct ftrace_iterator *iter;
1208
1209         mutex_lock(&ftrace_regex_lock);
1210         if (file->f_mode & FMODE_READ) {
1211                 iter = m->private;
1212
1213                 seq_release(inode, file);
1214         } else
1215                 iter = file->private_data;
1216
1217         if (iter->buffer_idx) {
1218                 iter->filtered++;
1219                 iter->buffer[iter->buffer_idx] = 0;
1220                 ftrace_match(iter->buffer, iter->buffer_idx, enable);
1221         }
1222
1223         mutex_lock(&ftrace_sysctl_lock);
1224         mutex_lock(&ftrace_start_lock);
1225         if (iter->filtered && ftrace_start_up && ftrace_enabled)
1226                 ftrace_run_update_code(FTRACE_ENABLE_CALLS);
1227         mutex_unlock(&ftrace_start_lock);
1228         mutex_unlock(&ftrace_sysctl_lock);
1229
1230         kfree(iter);
1231         mutex_unlock(&ftrace_regex_lock);
1232         return 0;
1233 }
1234
1235 static int
1236 ftrace_filter_release(struct inode *inode, struct file *file)
1237 {
1238         return ftrace_regex_release(inode, file, 1);
1239 }
1240
1241 static int
1242 ftrace_notrace_release(struct inode *inode, struct file *file)
1243 {
1244         return ftrace_regex_release(inode, file, 0);
1245 }
1246
1247 static struct file_operations ftrace_avail_fops = {
1248         .open = ftrace_avail_open,
1249         .read = seq_read,
1250         .llseek = seq_lseek,
1251         .release = ftrace_avail_release,
1252 };
1253
1254 static struct file_operations ftrace_failures_fops = {
1255         .open = ftrace_failures_open,
1256         .read = seq_read,
1257         .llseek = seq_lseek,
1258         .release = ftrace_avail_release,
1259 };
1260
1261 static struct file_operations ftrace_filter_fops = {
1262         .open = ftrace_filter_open,
1263         .read = ftrace_regex_read,
1264         .write = ftrace_filter_write,
1265         .llseek = ftrace_regex_lseek,
1266         .release = ftrace_filter_release,
1267 };
1268
1269 static struct file_operations ftrace_notrace_fops = {
1270         .open = ftrace_notrace_open,
1271         .read = ftrace_regex_read,
1272         .write = ftrace_notrace_write,
1273         .llseek = ftrace_regex_lseek,
1274         .release = ftrace_notrace_release,
1275 };
1276
1277 static __init int ftrace_init_debugfs(void)
1278 {
1279         struct dentry *d_tracer;
1280         struct dentry *entry;
1281
1282         d_tracer = tracing_init_dentry();
1283
1284         entry = debugfs_create_file("available_filter_functions", 0444,
1285                                     d_tracer, NULL, &ftrace_avail_fops);
1286         if (!entry)
1287                 pr_warning("Could not create debugfs "
1288                            "'available_filter_functions' entry\n");
1289
1290         entry = debugfs_create_file("failures", 0444,
1291                                     d_tracer, NULL, &ftrace_failures_fops);
1292         if (!entry)
1293                 pr_warning("Could not create debugfs 'failures' entry\n");
1294
1295         entry = debugfs_create_file("set_ftrace_filter", 0644, d_tracer,
1296                                     NULL, &ftrace_filter_fops);
1297         if (!entry)
1298                 pr_warning("Could not create debugfs "
1299                            "'set_ftrace_filter' entry\n");
1300
1301         entry = debugfs_create_file("set_ftrace_notrace", 0644, d_tracer,
1302                                     NULL, &ftrace_notrace_fops);
1303         if (!entry)
1304                 pr_warning("Could not create debugfs "
1305                            "'set_ftrace_notrace' entry\n");
1306
1307         return 0;
1308 }
1309
1310 fs_initcall(ftrace_init_debugfs);
1311
1312 static int ftrace_convert_nops(unsigned long *start,
1313                                unsigned long *end)
1314 {
1315         unsigned long *p;
1316         unsigned long addr;
1317         unsigned long flags;
1318
1319         mutex_lock(&ftrace_start_lock);
1320         p = start;
1321         while (p < end) {
1322                 addr = ftrace_call_adjust(*p++);
1323                 ftrace_record_ip(addr);
1324         }
1325
1326         /* disable interrupts to prevent kstop machine */
1327         local_irq_save(flags);
1328         ftrace_update_code();
1329         local_irq_restore(flags);
1330         mutex_unlock(&ftrace_start_lock);
1331
1332         return 0;
1333 }
1334
1335 void ftrace_init_module(unsigned long *start, unsigned long *end)
1336 {
1337         if (ftrace_disabled || start == end)
1338                 return;
1339         ftrace_convert_nops(start, end);
1340 }
1341
1342 extern unsigned long __start_mcount_loc[];
1343 extern unsigned long __stop_mcount_loc[];
1344
1345 void __init ftrace_init(void)
1346 {
1347         unsigned long count, addr, flags;
1348         int ret;
1349
1350         /* Keep the ftrace pointer to the stub */
1351         addr = (unsigned long)ftrace_stub;
1352
1353         local_irq_save(flags);
1354         ftrace_dyn_arch_init(&addr);
1355         local_irq_restore(flags);
1356
1357         /* ftrace_dyn_arch_init places the return code in addr */
1358         if (addr)
1359                 goto failed;
1360
1361         count = __stop_mcount_loc - __start_mcount_loc;
1362
1363         ret = ftrace_dyn_table_alloc(count);
1364         if (ret)
1365                 goto failed;
1366
1367         last_ftrace_enabled = ftrace_enabled = 1;
1368
1369         ret = ftrace_convert_nops(__start_mcount_loc,
1370                                   __stop_mcount_loc);
1371
1372         return;
1373  failed:
1374         ftrace_disabled = 1;
1375 }
1376
1377 #else
1378
1379 static int __init ftrace_nodyn_init(void)
1380 {
1381         ftrace_enabled = 1;
1382         return 0;
1383 }
1384 device_initcall(ftrace_nodyn_init);
1385
1386 # define ftrace_startup()               do { } while (0)
1387 # define ftrace_shutdown()              do { } while (0)
1388 # define ftrace_startup_sysctl()        do { } while (0)
1389 # define ftrace_shutdown_sysctl()       do { } while (0)
1390 #endif /* CONFIG_DYNAMIC_FTRACE */
1391
1392 /**
1393  * ftrace_kill - kill ftrace
1394  *
1395  * This function should be used by panic code. It stops ftrace
1396  * but in a not so nice way. If you need to simply kill ftrace
1397  * from a non-atomic section, use ftrace_kill.
1398  */
1399 void ftrace_kill(void)
1400 {
1401         ftrace_disabled = 1;
1402         ftrace_enabled = 0;
1403         clear_ftrace_function();
1404 }
1405
1406 /**
1407  * register_ftrace_function - register a function for profiling
1408  * @ops - ops structure that holds the function for profiling.
1409  *
1410  * Register a function to be called by all functions in the
1411  * kernel.
1412  *
1413  * Note: @ops->func and all the functions it calls must be labeled
1414  *       with "notrace", otherwise it will go into a
1415  *       recursive loop.
1416  */
1417 int register_ftrace_function(struct ftrace_ops *ops)
1418 {
1419         int ret;
1420
1421         if (unlikely(ftrace_disabled))
1422                 return -1;
1423
1424         mutex_lock(&ftrace_sysctl_lock);
1425         ret = __register_ftrace_function(ops);
1426         ftrace_startup();
1427         mutex_unlock(&ftrace_sysctl_lock);
1428
1429         return ret;
1430 }
1431
1432 /**
1433  * unregister_ftrace_function - unresgister a function for profiling.
1434  * @ops - ops structure that holds the function to unregister
1435  *
1436  * Unregister a function that was added to be called by ftrace profiling.
1437  */
1438 int unregister_ftrace_function(struct ftrace_ops *ops)
1439 {
1440         int ret;
1441
1442         mutex_lock(&ftrace_sysctl_lock);
1443         ret = __unregister_ftrace_function(ops);
1444         ftrace_shutdown();
1445         mutex_unlock(&ftrace_sysctl_lock);
1446
1447         return ret;
1448 }
1449
1450 int
1451 ftrace_enable_sysctl(struct ctl_table *table, int write,
1452                      struct file *file, void __user *buffer, size_t *lenp,
1453                      loff_t *ppos)
1454 {
1455         int ret;
1456
1457         if (unlikely(ftrace_disabled))
1458                 return -ENODEV;
1459
1460         mutex_lock(&ftrace_sysctl_lock);
1461
1462         ret  = proc_dointvec(table, write, file, buffer, lenp, ppos);
1463
1464         if (ret || !write || (last_ftrace_enabled == ftrace_enabled))
1465                 goto out;
1466
1467         last_ftrace_enabled = ftrace_enabled;
1468
1469         if (ftrace_enabled) {
1470
1471                 ftrace_startup_sysctl();
1472
1473                 /* we are starting ftrace again */
1474                 if (ftrace_list != &ftrace_list_end) {
1475                         if (ftrace_list->next == &ftrace_list_end)
1476                                 ftrace_trace_function = ftrace_list->func;
1477                         else
1478                                 ftrace_trace_function = ftrace_list_func;
1479                 }
1480
1481         } else {
1482                 /* stopping ftrace calls (just send to ftrace_stub) */
1483                 ftrace_trace_function = ftrace_stub;
1484
1485                 ftrace_shutdown_sysctl();
1486         }
1487
1488  out:
1489         mutex_unlock(&ftrace_sysctl_lock);
1490         return ret;
1491 }
1492
1493 #ifdef CONFIG_FUNCTION_RET_TRACER
1494 trace_function_return_t ftrace_function_return =
1495                         (trace_function_return_t)ftrace_stub;
1496 void register_ftrace_return(trace_function_return_t func)
1497 {
1498         ftrace_function_return = func;
1499 }
1500
1501 void unregister_ftrace_return(void)
1502 {
1503         ftrace_function_return = (trace_function_return_t)ftrace_stub;
1504 }
1505 #endif
1506
1507
1508