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 | FTRACE_OPS_FL_PID;
  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 struct tracer function_trace;
 223
 224 static int
 225 func_set_flag(struct trace_array *tr, u32 old_flags, u32 bit, int set)
 226 {
 227         switch (bit) {
 228         case TRACE_FUNC_OPT_STACK:
 229                 /* do nothing if already set */
 230                 if (!!set == !!(func_flags.val & TRACE_FUNC_OPT_STACK))
 231                         break;
 232
 233                 /* We can change this flag when not running. */
 234                 if (tr->current_trace != &function_trace)
 235                         break;
 236
 237                 unregister_ftrace_function(tr->ops);
 238
 239                 if (set) {
 240                         tr->ops->func = function_stack_trace_call;
 241                         register_ftrace_function(tr->ops);
 242                 } else {
 243                         tr->ops->func = function_trace_call;
 244                         register_ftrace_function(tr->ops);
 245                 }
 246
 247                 break;
 248         default:
 249                 return -EINVAL;
 250         }
 251
 252         return 0;
 253 }
 254
 255 static struct tracer function_trace __tracer_data =
 256 {
 257         .name           = "function",
 258         .init           = function_trace_init,
 259         .reset          = function_trace_reset,
 260         .start          = function_trace_start,
 261         .flags          = &func_flags,
 262         .set_flag       = func_set_flag,
 263         .allow_instances = true,
 264 #ifdef CONFIG_FTRACE_SELFTEST
 265         .selftest       = trace_selftest_startup_function,
 266 #endif
 267 };
 268
 269 #ifdef CONFIG_DYNAMIC_FTRACE
 270 static void update_traceon_count(void **data, bool on)
 271 {
 272         long *count = (long *)data;
 273         long old_count = *count;
 274
 275         /*
 276          * Tracing gets disabled (or enabled) once per count.
 277          * This function can be called at the same time on multiple CPUs.
 278          * It is fine if both disable (or enable) tracing, as disabling
 279          * (or enabling) the second time doesn't do anything as the
 280          * state of the tracer is already disabled (or enabled).
 281          * What needs to be synchronized in this case is that the count
 282          * only gets decremented once, even if the tracer is disabled
 283          * (or enabled) twice, as the second one is really a nop.
 284          *
 285          * The memory barriers guarantee that we only decrement the
 286          * counter once. First the count is read to a local variable
 287          * and a read barrier is used to make sure that it is loaded
 288          * before checking if the tracer is in the state we want.
 289          * If the tracer is not in the state we want, then the count
 290          * is guaranteed to be the old count.
 291          *
 292          * Next the tracer is set to the state we want (disabled or enabled)
 293          * then a write memory barrier is used to make sure that
 294          * the new state is visible before changing the counter by
 295          * one minus the old counter. This guarantees that another CPU
 296          * executing this code will see the new state before seeing
 297          * the new counter value, and would not do anything if the new
 298          * counter is seen.
 299          *
 300          * Note, there is no synchronization between this and a user
 301          * setting the tracing_on file. But we currently don't care
 302          * about that.
 303          */
 304         if (!old_count)
 305                 return;
 306
 307         /* Make sure we see count before checking tracing state */
 308         smp_rmb();
 309
 310         if (on == !!tracing_is_on())
 311                 return;
 312
 313         if (on)
 314                 tracing_on();
 315         else
 316                 tracing_off();
 317
 318         /* unlimited? */
 319         if (old_count == -1)
 320                 return;
 321
 322         /* Make sure tracing state is visible before updating count */
 323         smp_wmb();
 324
 325         *count = old_count - 1;
 326 }
 327
 328 static void
 329 ftrace_traceon_count(unsigned long ip, unsigned long parent_ip, void **data)
 330 {
 331         update_traceon_count(data, 1);
 332 }
 333
 334 static void
 335 ftrace_traceoff_count(unsigned long ip, unsigned long parent_ip, void **data)
 336 {
 337         update_traceon_count(data, 0);
 338 }
 339
 340 static void
 341 ftrace_traceon(unsigned long ip, unsigned long parent_ip, void **data)
 342 {
 343         if (tracing_is_on())
 344                 return;
 345
 346         tracing_on();
 347 }
 348
 349 static void
 350 ftrace_traceoff(unsigned long ip, unsigned long parent_ip, void **data)
 351 {
 352         if (!tracing_is_on())
 353                 return;
 354
 355         tracing_off();
 356 }
 357
 358 /*
 359  * Skip 4:
 360  *   ftrace_stacktrace()
 361  *   function_trace_probe_call()
 362  *   ftrace_ops_list_func()
 363  *   ftrace_call()
 364  */
 365 #define STACK_SKIP 4
 366
 367 static void
 368 ftrace_stacktrace(unsigned long ip, unsigned long parent_ip, void **data)
 369 {
 370         trace_dump_stack(STACK_SKIP);
 371 }
 372
 373 static void
 374 ftrace_stacktrace_count(unsigned long ip, unsigned long parent_ip, void **data)
 375 {
 376         long *count = (long *)data;
 377         long old_count;
 378         long new_count;
 379
 380         /*
 381          * Stack traces should only execute the number of times the
 382          * user specified in the counter.
 383          */
 384         do {
 385
 386                 if (!tracing_is_on())
 387                         return;
 388
 389                 old_count = *count;
 390
 391                 if (!old_count)
 392                         return;
 393
 394                 /* unlimited? */
 395                 if (old_count == -1) {
 396                         trace_dump_stack(STACK_SKIP);
 397                         return;
 398                 }
 399
 400                 new_count = old_count - 1;
 401                 new_count = cmpxchg(count, old_count, new_count);
 402                 if (new_count == old_count)
 403                         trace_dump_stack(STACK_SKIP);
 404
 405         } while (new_count != old_count);
 406 }
 407
 408 static int update_count(void **data)
 409 {
 410         unsigned long *count = (long *)data;
 411
 412         if (!*count)
 413                 return 0;
 414
 415         if (*count != -1)
 416                 (*count)--;
 417
 418         return 1;
 419 }
 420
 421 static void
 422 ftrace_dump_probe(unsigned long ip, unsigned long parent_ip, void **data)
 423 {
 424         if (update_count(data))
 425                 ftrace_dump(DUMP_ALL);
 426 }
 427
 428 /* Only dump the current CPU buffer. */
 429 static void
 430 ftrace_cpudump_probe(unsigned long ip, unsigned long parent_ip, void **data)
 431 {
 432         if (update_count(data))
 433                 ftrace_dump(DUMP_ORIG);
 434 }
 435
 436 static int
 437 ftrace_probe_print(const char *name, struct seq_file *m,
 438                    unsigned long ip, void *data)
 439 {
 440         long count = (long)data;
 441
 442         seq_printf(m, "%ps:%s", (void *)ip, name);
 443
 444         if (count == -1)
 445                 seq_puts(m, ":unlimited\n");
 446         else
 447                 seq_printf(m, ":count=%ld\n", count);
 448
 449         return 0;
 450 }
 451
 452 static int
 453 ftrace_traceon_print(struct seq_file *m, unsigned long ip,
 454                          struct ftrace_probe_ops *ops, void *data)
 455 {
 456         return ftrace_probe_print("traceon", m, ip, data);
 457 }
 458
 459 static int
 460 ftrace_traceoff_print(struct seq_file *m, unsigned long ip,
 461                          struct ftrace_probe_ops *ops, void *data)
 462 {
 463         return ftrace_probe_print("traceoff", m, ip, data);
 464 }
 465
 466 static int
 467 ftrace_stacktrace_print(struct seq_file *m, unsigned long ip,
 468                         struct ftrace_probe_ops *ops, void *data)
 469 {
 470         return ftrace_probe_print("stacktrace", m, ip, data);
 471 }
 472
 473 static int
 474 ftrace_dump_print(struct seq_file *m, unsigned long ip,
 475                         struct ftrace_probe_ops *ops, void *data)
 476 {
 477         return ftrace_probe_print("dump", m, ip, data);
 478 }
 479
 480 static int
 481 ftrace_cpudump_print(struct seq_file *m, unsigned long ip,
 482                         struct ftrace_probe_ops *ops, void *data)
 483 {
 484         return ftrace_probe_print("cpudump", m, ip, data);
 485 }
 486
 487 static struct ftrace_probe_ops traceon_count_probe_ops = {
 488         .func                   = ftrace_traceon_count,
 489         .print                  = ftrace_traceon_print,
 490 };
 491
 492 static struct ftrace_probe_ops traceoff_count_probe_ops = {
 493         .func                   = ftrace_traceoff_count,
 494         .print                  = ftrace_traceoff_print,
 495 };
 496
 497 static struct ftrace_probe_ops stacktrace_count_probe_ops = {
 498         .func                   = ftrace_stacktrace_count,
 499         .print                  = ftrace_stacktrace_print,
 500 };
 501
 502 static struct ftrace_probe_ops dump_probe_ops = {
 503         .func                   = ftrace_dump_probe,
 504         .print                  = ftrace_dump_print,
 505 };
 506
 507 static struct ftrace_probe_ops cpudump_probe_ops = {
 508         .func                   = ftrace_cpudump_probe,
 509         .print                  = ftrace_cpudump_print,
 510 };
 511
 512 static struct ftrace_probe_ops traceon_probe_ops = {
 513         .func                   = ftrace_traceon,
 514         .print                  = ftrace_traceon_print,
 515 };
 516
 517 static struct ftrace_probe_ops traceoff_probe_ops = {
 518         .func                   = ftrace_traceoff,
 519         .print                  = ftrace_traceoff_print,
 520 };
 521
 522 static struct ftrace_probe_ops stacktrace_probe_ops = {
 523         .func                   = ftrace_stacktrace,
 524         .print                  = ftrace_stacktrace_print,
 525 };
 526
 527 static int
 528 ftrace_trace_probe_callback(struct ftrace_probe_ops *ops,
 529                             struct ftrace_hash *hash, char *glob,
 530                             char *cmd, char *param, int enable)
 531 {
 532         void *count = (void *)-1;
 533         char *number;
 534         int ret;
 535
 536         /* hash funcs only work with set_ftrace_filter */
 537         if (!enable)
 538                 return -EINVAL;
 539
 540         if (glob[0] == '!') {
 541                 unregister_ftrace_function_probe_func(glob+1, ops);
 542                 return 0;
 543         }
 544
 545         if (!param)
 546                 goto out_reg;
 547
 548         number = strsep(&param, ":");
 549
 550         if (!strlen(number))
 551                 goto out_reg;
 552
 553         /*
 554          * We use the callback data field (which is a pointer)
 555          * as our counter.
 556          */
 557         ret = kstrtoul(number, 0, (unsigned long *)&count);
 558         if (ret)
 559                 return ret;
 560
 561  out_reg:
 562         ret = register_ftrace_function_probe(glob, ops, count);
 563
 564         return ret < 0 ? ret : 0;
 565 }
 566
 567 static int
 568 ftrace_trace_onoff_callback(struct ftrace_hash *hash,
 569                             char *glob, char *cmd, char *param, int enable)
 570 {
 571         struct ftrace_probe_ops *ops;
 572
 573         /* we register both traceon and traceoff to this callback */
 574         if (strcmp(cmd, "traceon") == 0)
 575                 ops = param ? &traceon_count_probe_ops : &traceon_probe_ops;
 576         else
 577                 ops = param ? &traceoff_count_probe_ops : &traceoff_probe_ops;
 578
 579         return ftrace_trace_probe_callback(ops, hash, glob, cmd,
 580                                            param, enable);
 581 }
 582
 583 static int
 584 ftrace_stacktrace_callback(struct ftrace_hash *hash,
 585                            char *glob, char *cmd, char *param, int enable)
 586 {
 587         struct ftrace_probe_ops *ops;
 588
 589         ops = param ? &stacktrace_count_probe_ops : &stacktrace_probe_ops;
 590
 591         return ftrace_trace_probe_callback(ops, hash, glob, cmd,
 592                                            param, enable);
 593 }
 594
 595 static int
 596 ftrace_dump_callback(struct ftrace_hash *hash,
 597                            char *glob, char *cmd, char *param, int enable)
 598 {
 599         struct ftrace_probe_ops *ops;
 600
 601         ops = &dump_probe_ops;
 602
 603         /* Only dump once. */
 604         return ftrace_trace_probe_callback(ops, hash, glob, cmd,
 605                                            "1", enable);
 606 }
 607
 608 static int
 609 ftrace_cpudump_callback(struct ftrace_hash *hash,
 610                            char *glob, char *cmd, char *param, int enable)
 611 {
 612         struct ftrace_probe_ops *ops;
 613
 614         ops = &cpudump_probe_ops;
 615
 616         /* Only dump once. */
 617         return ftrace_trace_probe_callback(ops, hash, glob, cmd,
 618                                            "1", enable);
 619 }
 620
 621 static struct ftrace_func_command ftrace_traceon_cmd = {
 622         .name                   = "traceon",
 623         .func                   = ftrace_trace_onoff_callback,
 624 };
 625
 626 static struct ftrace_func_command ftrace_traceoff_cmd = {
 627         .name                   = "traceoff",
 628         .func                   = ftrace_trace_onoff_callback,
 629 };
 630
 631 static struct ftrace_func_command ftrace_stacktrace_cmd = {
 632         .name                   = "stacktrace",
 633         .func                   = ftrace_stacktrace_callback,
 634 };
 635
 636 static struct ftrace_func_command ftrace_dump_cmd = {
 637         .name                   = "dump",
 638         .func                   = ftrace_dump_callback,
 639 };
 640
 641 static struct ftrace_func_command ftrace_cpudump_cmd = {
 642         .name                   = "cpudump",
 643         .func                   = ftrace_cpudump_callback,
 644 };
 645
 646 static int __init init_func_cmd_traceon(void)
 647 {
 648         int ret;
 649
 650         ret = register_ftrace_command(&ftrace_traceoff_cmd);
 651         if (ret)
 652                 return ret;
 653
 654         ret = register_ftrace_command(&ftrace_traceon_cmd);
 655         if (ret)
 656                 goto out_free_traceoff;
 657
 658         ret = register_ftrace_command(&ftrace_stacktrace_cmd);
 659         if (ret)
 660                 goto out_free_traceon;
 661
 662         ret = register_ftrace_command(&ftrace_dump_cmd);
 663         if (ret)
 664                 goto out_free_stacktrace;
 665
 666         ret = register_ftrace_command(&ftrace_cpudump_cmd);
 667         if (ret)
 668                 goto out_free_dump;
 669
 670         return 0;
 671
 672  out_free_dump:
 673         unregister_ftrace_command(&ftrace_dump_cmd);
 674  out_free_stacktrace:
 675         unregister_ftrace_command(&ftrace_stacktrace_cmd);
 676  out_free_traceon:
 677         unregister_ftrace_command(&ftrace_traceon_cmd);
 678  out_free_traceoff:
 679         unregister_ftrace_command(&ftrace_traceoff_cmd);
 680
 681         return ret;
 682 }
 683 #else
 684 static inline int init_func_cmd_traceon(void)
 685 {
 686         return 0;
 687 }
 688 #endif /* CONFIG_DYNAMIC_FTRACE */
 689
 690 static __init int init_function_trace(void)
 691 {
 692         init_func_cmd_traceon();
 693         return register_tracer(&function_trace);
 694 }
 695 core_initcall(init_function_trace);