kernel/trace/trace_functions.c

   1 /*
   2  * ring buffer based function tracer
   3  *
   4  * Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
   5  * Copyright (C) 2008 Ingo Molnar <mingo@redhat.com>
   6  *
   7  * Based on code from the latency_tracer, that is:
   8  *
   9  *  Copyright (C) 2004-2006 Ingo Molnar
  10  *  Copyright (C) 2004 Nadia Yvette Chambers
  11  */
  12 #include <linux/ring_buffer.h>
  13 #include <linux/debugfs.h>
  14 #include <linux/uaccess.h>
  15 #include <linux/ftrace.h>
  16 #include <linux/slab.h>
  17 #include <linux/fs.h>
  18
  19 #include "trace.h"
  20
  21 static void tracing_start_function_trace(struct trace_array *tr);
  22 static void tracing_stop_function_trace(struct trace_array *tr);
  23 static void
  24 function_trace_call(unsigned long ip, unsigned long parent_ip,
  25                     struct ftrace_ops *op, struct pt_regs *pt_regs);
  26 static void
  27 function_stack_trace_call(unsigned long ip, unsigned long parent_ip,
  28                           struct ftrace_ops *op, struct pt_regs *pt_regs);
  29 static struct tracer_flags func_flags;
  30
  31 /* Our option */
  32 enum {
  33         TRACE_FUNC_OPT_STACK    = 0x1,
  34 };
  35
  36 static int allocate_ftrace_ops(struct trace_array *tr)
  37 {
  38         struct ftrace_ops *ops;
  39
  40         ops = kzalloc(sizeof(*ops), GFP_KERNEL);
  41         if (!ops)
  42                 return -ENOMEM;
  43
  44         /* Currently only the non stack verision is supported */
  45         ops->func = function_trace_call;
  46         ops->flags = FTRACE_OPS_FL_RECURSION_SAFE;
  47
  48         tr->ops = ops;
  49         ops->private = tr;
  50         return 0;
  51 }
  52
  53
  54 int ftrace_create_function_files(struct trace_array *tr,
  55                                  struct dentry *parent)
  56 {
  57         int ret;
  58
  59         /*
  60          * The top level array uses the "global_ops", and the files are
  61          * created on boot up.
  62          */
  63         if (tr->flags & TRACE_ARRAY_FL_GLOBAL)
  64                 return 0;
  65
  66         ret = allocate_ftrace_ops(tr);
  67         if (ret)
  68                 return ret;
  69
  70         ftrace_create_filter_files(tr->ops, parent);
  71
  72         return 0;
  73 }
  74
  75 void ftrace_destroy_function_files(struct trace_array *tr)
  76 {
  77         ftrace_destroy_filter_files(tr->ops);
  78         kfree(tr->ops);
  79         tr->ops = NULL;
  80 }
  81
  82 static int function_trace_init(struct trace_array *tr)
  83 {
  84         ftrace_func_t func;
  85
  86         /*
  87          * Instance trace_arrays get their ops allocated
  88          * at instance creation. Unless it failed
  89          * the allocation.
  90          */
  91         if (!tr->ops)
  92                 return -ENOMEM;
  93
  94         /* Currently only the global instance can do stack tracing */
  95         if (tr->flags & TRACE_ARRAY_FL_GLOBAL &&
  96             func_flags.val & TRACE_FUNC_OPT_STACK)
  97                 func = function_stack_trace_call;
  98         else
  99                 func = function_trace_call;
 100
 101         ftrace_init_array_ops(tr, func);
 102
 103         tr->trace_buffer.cpu = get_cpu();
 104         put_cpu();
 105
 106         tracing_start_cmdline_record();
 107         tracing_start_function_trace(tr);
 108         return 0;
 109 }
 110
 111 static void function_trace_reset(struct trace_array *tr)
 112 {
 113         tracing_stop_function_trace(tr);
 114         tracing_stop_cmdline_record();
 115         ftrace_reset_array_ops(tr);
 116 }
 117
 118 static void function_trace_start(struct trace_array *tr)
 119 {
 120         tracing_reset_online_cpus(&tr->trace_buffer);
 121 }
 122
 123 static void
 124 function_trace_call(unsigned long ip, unsigned long parent_ip,
 125                     struct ftrace_ops *op, struct pt_regs *pt_regs)
 126 {
 127         struct trace_array *tr = op->private;
 128         struct trace_array_cpu *data;
 129         unsigned long flags;
 130         int bit;
 131         int cpu;
 132         int pc;
 133
 134         if (unlikely(!tr->function_enabled))
 135                 return;
 136
 137         pc = preempt_count();
 138         preempt_disable_notrace();
 139
 140         bit = trace_test_and_set_recursion(TRACE_FTRACE_START, TRACE_FTRACE_MAX);
 141         if (bit < 0)
 142                 goto out;
 143
 144         cpu = smp_processor_id();
 145         data = per_cpu_ptr(tr->trace_buffer.data, cpu);
 146         if (!atomic_read(&data->disabled)) {
 147                 local_save_flags(flags);
 148                 trace_function(tr, ip, parent_ip, flags, pc);
 149         }
 150         trace_clear_recursion(bit);
 151
 152  out:
 153         preempt_enable_notrace();
 154 }
 155
 156 static void
 157 function_stack_trace_call(unsigned long ip, unsigned long parent_ip,
 158                           struct ftrace_ops *op, struct pt_regs *pt_regs)
 159 {
 160         struct trace_array *tr = op->private;
 161         struct trace_array_cpu *data;
 162         unsigned long flags;
 163         long disabled;
 164         int cpu;
 165         int pc;
 166
 167         if (unlikely(!tr->function_enabled))
 168                 return;
 169
 170         /*
 171          * Need to use raw, since this must be called before the
 172          * recursive protection is performed.
 173          */
 174         local_irq_save(flags);
 175         cpu = raw_smp_processor_id();
 176         data = per_cpu_ptr(tr->trace_buffer.data, cpu);
 177         disabled = atomic_inc_return(&data->disabled);
 178
 179         if (likely(disabled == 1)) {
 180                 pc = preempt_count();
 181                 trace_function(tr, ip, parent_ip, flags, pc);
 182                 /*
 183                  * skip over 5 funcs:
 184                  *    __ftrace_trace_stack,
 185                  *    __trace_stack,
 186                  *    function_stack_trace_call
 187                  *    ftrace_list_func
 188                  *    ftrace_call
 189                  */
 190                 __trace_stack(tr, flags, 5, pc);
 191         }
 192
 193         atomic_dec(&data->disabled);
 194         local_irq_restore(flags);
 195 }
 196
 197 static struct tracer_opt func_opts[] = {
 198 #ifdef CONFIG_STACKTRACE
 199         { TRACER_OPT(func_stack_trace, TRACE_FUNC_OPT_STACK) },
 200 #endif
 201         { } /* Always set a last empty entry */
 202 };
 203
 204 static struct tracer_flags func_flags = {
 205         .val = 0, /* By default: all flags disabled */
 206         .opts = func_opts
 207 };
 208
 209 static void tracing_start_function_trace(struct trace_array *tr)
 210 {
 211         tr->function_enabled = 0;
 212         register_ftrace_function(tr->ops);
 213         tr->function_enabled = 1;
 214 }
 215
 216 static void tracing_stop_function_trace(struct trace_array *tr)
 217 {
 218         tr->function_enabled = 0;
 219         unregister_ftrace_function(tr->ops);
 220 }
 221
 222 static int
 223 func_set_flag(struct trace_array *tr, u32 old_flags, u32 bit, int set)
 224 {
 225         switch (bit) {
 226         case TRACE_FUNC_OPT_STACK:
 227                 /* do nothing if already set */
 228                 if (!!set == !!(func_flags.val & TRACE_FUNC_OPT_STACK))
 229                         break;
 230
 231                 unregister_ftrace_function(tr->ops);
 232
 233                 if (set) {
 234                         tr->ops->func = function_stack_trace_call;
 235                         register_ftrace_function(tr->ops);
 236                 } else {
 237                         tr->ops->func = function_trace_call;
 238                         register_ftrace_function(tr->ops);
 239                 }
 240
 241                 break;
 242         default:
 243                 return -EINVAL;
 244         }
 245
 246         return 0;
 247 }
 248
 249 static struct tracer function_trace __tracer_data =
 250 {
 251         .name           = "function",
 252         .init           = function_trace_init,
 253         .reset          = function_trace_reset,
 254         .start          = function_trace_start,
 255         .flags          = &func_flags,
 256         .set_flag       = func_set_flag,
 257         .allow_instances = true,
 258 #ifdef CONFIG_FTRACE_SELFTEST
 259         .selftest       = trace_selftest_startup_function,
 260 #endif
 261 };
 262
 263 #ifdef CONFIG_DYNAMIC_FTRACE
 264 static void update_traceon_count(void **data, bool on)
 265 {
 266         long *count = (long *)data;
 267         long old_count = *count;
 268
 269         /*
 270          * Tracing gets disabled (or enabled) once per count.
 271          * This function can be called at the same time on multiple CPUs.
 272          * It is fine if both disable (or enable) tracing, as disabling
 273          * (or enabling) the second time doesn't do anything as the
 274          * state of the tracer is already disabled (or enabled).
 275          * What needs to be synchronized in this case is that the count
 276          * only gets decremented once, even if the tracer is disabled
 277          * (or enabled) twice, as the second one is really a nop.
 278          *
 279          * The memory barriers guarantee that we only decrement the
 280          * counter once. First the count is read to a local variable
 281          * and a read barrier is used to make sure that it is loaded
 282          * before checking if the tracer is in the state we want.
 283          * If the tracer is not in the state we want, then the count
 284          * is guaranteed to be the old count.
 285          *
 286          * Next the tracer is set to the state we want (disabled or enabled)
 287          * then a write memory barrier is used to make sure that
 288          * the new state is visible before changing the counter by
 289          * one minus the old counter. This guarantees that another CPU
 290          * executing this code will see the new state before seeing
 291          * the new counter value, and would not do anything if the new
 292          * counter is seen.
 293          *
 294          * Note, there is no synchronization between this and a user
 295          * setting the tracing_on file. But we currently don't care
 296          * about that.
 297          */
 298         if (!old_count)
 299                 return;
 300
 301         /* Make sure we see count before checking tracing state */
 302         smp_rmb();
 303
 304         if (on == !!tracing_is_on())
 305                 return;
 306
 307         if (on)
 308                 tracing_on();
 309         else
 310                 tracing_off();
 311
 312         /* unlimited? */
 313         if (old_count == -1)
 314                 return;
 315
 316         /* Make sure tracing state is visible before updating count */
 317         smp_wmb();
 318
 319         *count = old_count - 1;
 320 }
 321
 322 static void
 323 ftrace_traceon_count(unsigned long ip, unsigned long parent_ip, void **data)
 324 {
 325         update_traceon_count(data, 1);
 326 }
 327
 328 static void
 329 ftrace_traceoff_count(unsigned long ip, unsigned long parent_ip, void **data)
 330 {
 331         update_traceon_count(data, 0);
 332 }
 333
 334 static void
 335 ftrace_traceon(unsigned long ip, unsigned long parent_ip, void **data)
 336 {
 337         if (tracing_is_on())
 338                 return;
 339
 340         tracing_on();
 341 }
 342
 343 static void
 344 ftrace_traceoff(unsigned long ip, unsigned long parent_ip, void **data)
 345 {
 346         if (!tracing_is_on())
 347                 return;
 348
 349         tracing_off();
 350 }
 351
 352 /*
 353  * Skip 4:
 354  *   ftrace_stacktrace()
 355  *   function_trace_probe_call()
 356  *   ftrace_ops_list_func()
 357  *   ftrace_call()
 358  */
 359 #define STACK_SKIP 4
 360
 361 static void
 362 ftrace_stacktrace(unsigned long ip, unsigned long parent_ip, void **data)
 363 {
 364         trace_dump_stack(STACK_SKIP);
 365 }
 366
 367 static void
 368 ftrace_stacktrace_count(unsigned long ip, unsigned long parent_ip, void **data)
 369 {
 370         long *count = (long *)data;
 371         long old_count;
 372         long new_count;
 373
 374         /*
 375          * Stack traces should only execute the number of times the
 376          * user specified in the counter.
 377          */
 378         do {
 379
 380                 if (!tracing_is_on())
 381                         return;
 382
 383                 old_count = *count;
 384
 385                 if (!old_count)
 386                         return;
 387
 388                 /* unlimited? */
 389                 if (old_count == -1) {
 390                         trace_dump_stack(STACK_SKIP);
 391                         return;
 392                 }
 393
 394                 new_count = old_count - 1;
 395                 new_count = cmpxchg(count, old_count, new_count);
 396                 if (new_count == old_count)
 397                         trace_dump_stack(STACK_SKIP);
 398
 399         } while (new_count != old_count);
 400 }
 401
 402 static int update_count(void **data)
 403 {
 404         unsigned long *count = (long *)data;
 405
 406         if (!*count)
 407                 return 0;
 408
 409         if (*count != -1)
 410                 (*count)--;
 411
 412         return 1;
 413 }
 414
 415 static void
 416 ftrace_dump_probe(unsigned long ip, unsigned long parent_ip, void **data)
 417 {
 418         if (update_count(data))
 419                 ftrace_dump(DUMP_ALL);
 420 }
 421
 422 /* Only dump the current CPU buffer. */
 423 static void
 424 ftrace_cpudump_probe(unsigned long ip, unsigned long parent_ip, void **data)
 425 {
 426         if (update_count(data))
 427                 ftrace_dump(DUMP_ORIG);
 428 }
 429
 430 static int
 431 ftrace_probe_print(const char *name, struct seq_file *m,
 432                    unsigned long ip, void *data)
 433 {
 434         long count = (long)data;
 435
 436         seq_printf(m, "%ps:%s", (void *)ip, name);
 437
 438         if (count == -1)
 439                 seq_puts(m, ":unlimited\n");
 440         else
 441                 seq_printf(m, ":count=%ld\n", count);
 442
 443         return 0;
 444 }
 445
 446 static int
 447 ftrace_traceon_print(struct seq_file *m, unsigned long ip,
 448                          struct ftrace_probe_ops *ops, void *data)
 449 {
 450         return ftrace_probe_print("traceon", m, ip, data);
 451 }
 452
 453 static int
 454 ftrace_traceoff_print(struct seq_file *m, unsigned long ip,
 455                          struct ftrace_probe_ops *ops, void *data)
 456 {
 457         return ftrace_probe_print("traceoff", m, ip, data);
 458 }
 459
 460 static int
 461 ftrace_stacktrace_print(struct seq_file *m, unsigned long ip,
 462                         struct ftrace_probe_ops *ops, void *data)
 463 {
 464         return ftrace_probe_print("stacktrace", m, ip, data);
 465 }
 466
 467 static int
 468 ftrace_dump_print(struct seq_file *m, unsigned long ip,
 469                         struct ftrace_probe_ops *ops, void *data)
 470 {
 471         return ftrace_probe_print("dump", m, ip, data);
 472 }
 473
 474 static int
 475 ftrace_cpudump_print(struct seq_file *m, unsigned long ip,
 476                         struct ftrace_probe_ops *ops, void *data)
 477 {
 478         return ftrace_probe_print("cpudump", m, ip, data);
 479 }
 480
 481 static struct ftrace_probe_ops traceon_count_probe_ops = {
 482         .func                   = ftrace_traceon_count,
 483         .print                  = ftrace_traceon_print,
 484 };
 485
 486 static struct ftrace_probe_ops traceoff_count_probe_ops = {
 487         .func                   = ftrace_traceoff_count,
 488         .print                  = ftrace_traceoff_print,
 489 };
 490
 491 static struct ftrace_probe_ops stacktrace_count_probe_ops = {
 492         .func                   = ftrace_stacktrace_count,
 493         .print                  = ftrace_stacktrace_print,
 494 };
 495
 496 static struct ftrace_probe_ops dump_probe_ops = {
 497         .func                   = ftrace_dump_probe,
 498         .print                  = ftrace_dump_print,
 499 };
 500
 501 static struct ftrace_probe_ops cpudump_probe_ops = {
 502         .func                   = ftrace_cpudump_probe,
 503         .print                  = ftrace_cpudump_print,
 504 };
 505
 506 static struct ftrace_probe_ops traceon_probe_ops = {
 507         .func                   = ftrace_traceon,
 508         .print                  = ftrace_traceon_print,
 509 };
 510
 511 static struct ftrace_probe_ops traceoff_probe_ops = {
 512         .func                   = ftrace_traceoff,
 513         .print                  = ftrace_traceoff_print,
 514 };
 515
 516 static struct ftrace_probe_ops stacktrace_probe_ops = {
 517         .func                   = ftrace_stacktrace,
 518         .print                  = ftrace_stacktrace_print,
 519 };
 520
 521 static int
 522 ftrace_trace_probe_callback(struct ftrace_probe_ops *ops,
 523                             struct ftrace_hash *hash, char *glob,
 524                             char *cmd, char *param, int enable)
 525 {
 526         void *count = (void *)-1;
 527         char *number;
 528         int ret;
 529
 530         /* hash funcs only work with set_ftrace_filter */
 531         if (!enable)
 532                 return -EINVAL;
 533
 534         if (glob[0] == '!') {
 535                 unregister_ftrace_function_probe_func(glob+1, ops);
 536                 return 0;
 537         }
 538
 539         if (!param)
 540                 goto out_reg;
 541
 542         number = strsep(&param, ":");
 543
 544         if (!strlen(number))
 545                 goto out_reg;
 546
 547         /*
 548          * We use the callback data field (which is a pointer)
 549          * as our counter.
 550          */
 551         ret = kstrtoul(number, 0, (unsigned long *)&count);
 552         if (ret)
 553                 return ret;
 554
 555  out_reg:
 556         ret = register_ftrace_function_probe(glob, ops, count);
 557
 558         return ret < 0 ? ret : 0;
 559 }
 560
 561 static int
 562 ftrace_trace_onoff_callback(struct ftrace_hash *hash,
 563                             char *glob, char *cmd, char *param, int enable)
 564 {
 565         struct ftrace_probe_ops *ops;
 566
 567         /* we register both traceon and traceoff to this callback */
 568         if (strcmp(cmd, "traceon") == 0)
 569                 ops = param ? &traceon_count_probe_ops : &traceon_probe_ops;
 570         else
 571                 ops = param ? &traceoff_count_probe_ops : &traceoff_probe_ops;
 572
 573         return ftrace_trace_probe_callback(ops, hash, glob, cmd,
 574                                            param, enable);
 575 }
 576
 577 static int
 578 ftrace_stacktrace_callback(struct ftrace_hash *hash,
 579                            char *glob, char *cmd, char *param, int enable)
 580 {
 581         struct ftrace_probe_ops *ops;
 582
 583         ops = param ? &stacktrace_count_probe_ops : &stacktrace_probe_ops;
 584
 585         return ftrace_trace_probe_callback(ops, hash, glob, cmd,
 586                                            param, enable);
 587 }
 588
 589 static int
 590 ftrace_dump_callback(struct ftrace_hash *hash,
 591                            char *glob, char *cmd, char *param, int enable)
 592 {
 593         struct ftrace_probe_ops *ops;
 594
 595         ops = &dump_probe_ops;
 596
 597         /* Only dump once. */
 598         return ftrace_trace_probe_callback(ops, hash, glob, cmd,
 599                                            "1", enable);
 600 }
 601
 602 static int
 603 ftrace_cpudump_callback(struct ftrace_hash *hash,
 604                            char *glob, char *cmd, char *param, int enable)
 605 {
 606         struct ftrace_probe_ops *ops;
 607
 608         ops = &cpudump_probe_ops;
 609
 610         /* Only dump once. */
 611         return ftrace_trace_probe_callback(ops, hash, glob, cmd,
 612                                            "1", enable);
 613 }
 614
 615 static struct ftrace_func_command ftrace_traceon_cmd = {
 616         .name                   = "traceon",
 617         .func                   = ftrace_trace_onoff_callback,
 618 };
 619
 620 static struct ftrace_func_command ftrace_traceoff_cmd = {
 621         .name                   = "traceoff",
 622         .func                   = ftrace_trace_onoff_callback,
 623 };
 624
 625 static struct ftrace_func_command ftrace_stacktrace_cmd = {
 626         .name                   = "stacktrace",
 627         .func                   = ftrace_stacktrace_callback,
 628 };
 629
 630 static struct ftrace_func_command ftrace_dump_cmd = {
 631         .name                   = "dump",
 632         .func                   = ftrace_dump_callback,
 633 };
 634
 635 static struct ftrace_func_command ftrace_cpudump_cmd = {
 636         .name                   = "cpudump",
 637         .func                   = ftrace_cpudump_callback,
 638 };
 639
 640 static int __init init_func_cmd_traceon(void)
 641 {
 642         int ret;
 643
 644         ret = register_ftrace_command(&ftrace_traceoff_cmd);
 645         if (ret)
 646                 return ret;
 647
 648         ret = register_ftrace_command(&ftrace_traceon_cmd);
 649         if (ret)
 650                 goto out_free_traceoff;
 651
 652         ret = register_ftrace_command(&ftrace_stacktrace_cmd);
 653         if (ret)
 654                 goto out_free_traceon;
 655
 656         ret = register_ftrace_command(&ftrace_dump_cmd);
 657         if (ret)
 658                 goto out_free_stacktrace;
 659
 660         ret = register_ftrace_command(&ftrace_cpudump_cmd);
 661         if (ret)
 662                 goto out_free_dump;
 663
 664         return 0;
 665
 666  out_free_dump:
 667         unregister_ftrace_command(&ftrace_dump_cmd);
 668  out_free_stacktrace:
 669         unregister_ftrace_command(&ftrace_stacktrace_cmd);
 670  out_free_traceon:
 671         unregister_ftrace_command(&ftrace_traceon_cmd);
 672  out_free_traceoff:
 673         unregister_ftrace_command(&ftrace_traceoff_cmd);
 674
 675         return ret;
 676 }
 677 #else
 678 static inline int init_func_cmd_traceon(void)
 679 {
 680         return 0;
 681 }
 682 #endif /* CONFIG_DYNAMIC_FTRACE */
 683
 684 static __init int init_function_trace(void)
 685 {
 686         init_func_cmd_traceon();
 687         return register_tracer(&function_trace);
 688 }
 689 core_initcall(init_function_trace);