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/fs.h>
  17
  18 #include "trace.h"
  19
  20 /* function tracing enabled */
  21 static int                      ftrace_function_enabled;
  22
  23 static struct trace_array       *func_trace;
  24
  25 static void tracing_start_function_trace(void);
  26 static void tracing_stop_function_trace(void);
  27
  28 static int function_trace_init(struct trace_array *tr)
  29 {
  30         func_trace = tr;
  31         tr->trace_buffer.cpu = get_cpu();
  32         put_cpu();
  33
  34         tracing_start_cmdline_record();
  35         tracing_start_function_trace();
  36         return 0;
  37 }
  38
  39 static void function_trace_reset(struct trace_array *tr)
  40 {
  41         tracing_stop_function_trace();
  42         tracing_stop_cmdline_record();
  43 }
  44
  45 static void function_trace_start(struct trace_array *tr)
  46 {
  47         tracing_reset_online_cpus(&tr->trace_buffer);
  48 }
  49
  50 /* Our option */
  51 enum {
  52         TRACE_FUNC_OPT_STACK    = 0x1,
  53 };
  54
  55 static struct tracer_flags func_flags;
  56
  57 static void
  58 function_trace_call(unsigned long ip, unsigned long parent_ip,
  59                     struct ftrace_ops *op, struct pt_regs *pt_regs)
  60 {
  61         struct trace_array *tr = func_trace;
  62         struct trace_array_cpu *data;
  63         unsigned long flags;
  64         int bit;
  65         int cpu;
  66         int pc;
  67
  68         if (unlikely(!ftrace_function_enabled))
  69                 return;
  70
  71         pc = preempt_count();
  72         preempt_disable_notrace();
  73
  74         bit = trace_test_and_set_recursion(TRACE_FTRACE_START, TRACE_FTRACE_MAX);
  75         if (bit < 0)
  76                 goto out;
  77
  78         cpu = smp_processor_id();
  79         data = per_cpu_ptr(tr->trace_buffer.data, cpu);
  80         if (!atomic_read(&data->disabled)) {
  81                 local_save_flags(flags);
  82                 trace_function(tr, ip, parent_ip, flags, pc);
  83         }
  84         trace_clear_recursion(bit);
  85
  86  out:
  87         preempt_enable_notrace();
  88 }
  89
  90 static void
  91 function_stack_trace_call(unsigned long ip, unsigned long parent_ip,
  92                           struct ftrace_ops *op, struct pt_regs *pt_regs)
  93 {
  94         struct trace_array *tr = func_trace;
  95         struct trace_array_cpu *data;
  96         unsigned long flags;
  97         long disabled;
  98         int cpu;
  99         int pc;
 100
 101         if (unlikely(!ftrace_function_enabled))
 102                 return;
 103
 104         /*
 105          * Need to use raw, since this must be called before the
 106          * recursive protection is performed.
 107          */
 108         local_irq_save(flags);
 109         cpu = raw_smp_processor_id();
 110         data = per_cpu_ptr(tr->trace_buffer.data, cpu);
 111         disabled = atomic_inc_return(&data->disabled);
 112
 113         if (likely(disabled == 1)) {
 114                 pc = preempt_count();
 115                 trace_function(tr, ip, parent_ip, flags, pc);
 116                 /*
 117                  * skip over 5 funcs:
 118                  *    __ftrace_trace_stack,
 119                  *    __trace_stack,
 120                  *    function_stack_trace_call
 121                  *    ftrace_list_func
 122                  *    ftrace_call
 123                  */
 124                 __trace_stack(tr, flags, 5, pc);
 125         }
 126
 127         atomic_dec(&data->disabled);
 128         local_irq_restore(flags);
 129 }
 130
 131
 132 static struct ftrace_ops trace_ops __read_mostly =
 133 {
 134         .func = function_trace_call,
 135         .flags = FTRACE_OPS_FL_GLOBAL | FTRACE_OPS_FL_RECURSION_SAFE,
 136 };
 137
 138 static struct ftrace_ops trace_stack_ops __read_mostly =
 139 {
 140         .func = function_stack_trace_call,
 141         .flags = FTRACE_OPS_FL_GLOBAL | FTRACE_OPS_FL_RECURSION_SAFE,
 142 };
 143
 144 static struct tracer_opt func_opts[] = {
 145 #ifdef CONFIG_STACKTRACE
 146         { TRACER_OPT(func_stack_trace, TRACE_FUNC_OPT_STACK) },
 147 #endif
 148         { } /* Always set a last empty entry */
 149 };
 150
 151 static struct tracer_flags func_flags = {
 152         .val = 0, /* By default: all flags disabled */
 153         .opts = func_opts
 154 };
 155
 156 static void tracing_start_function_trace(void)
 157 {
 158         ftrace_function_enabled = 0;
 159
 160         if (func_flags.val & TRACE_FUNC_OPT_STACK)
 161                 register_ftrace_function(&trace_stack_ops);
 162         else
 163                 register_ftrace_function(&trace_ops);
 164
 165         ftrace_function_enabled = 1;
 166 }
 167
 168 static void tracing_stop_function_trace(void)
 169 {
 170         ftrace_function_enabled = 0;
 171
 172         if (func_flags.val & TRACE_FUNC_OPT_STACK)
 173                 unregister_ftrace_function(&trace_stack_ops);
 174         else
 175                 unregister_ftrace_function(&trace_ops);
 176 }
 177
 178 static int func_set_flag(u32 old_flags, u32 bit, int set)
 179 {
 180         switch (bit) {
 181         case TRACE_FUNC_OPT_STACK:
 182                 /* do nothing if already set */
 183                 if (!!set == !!(func_flags.val & TRACE_FUNC_OPT_STACK))
 184                         break;
 185
 186                 if (set) {
 187                         unregister_ftrace_function(&trace_ops);
 188                         register_ftrace_function(&trace_stack_ops);
 189                 } else {
 190                         unregister_ftrace_function(&trace_stack_ops);
 191                         register_ftrace_function(&trace_ops);
 192                 }
 193
 194                 break;
 195         default:
 196                 return -EINVAL;
 197         }
 198
 199         return 0;
 200 }
 201
 202 static struct tracer function_trace __read_mostly =
 203 {
 204         .name           = "function",
 205         .init           = function_trace_init,
 206         .reset          = function_trace_reset,
 207         .start          = function_trace_start,
 208         .wait_pipe      = poll_wait_pipe,
 209         .flags          = &func_flags,
 210         .set_flag       = func_set_flag,
 211 #ifdef CONFIG_FTRACE_SELFTEST
 212         .selftest       = trace_selftest_startup_function,
 213 #endif
 214 };
 215
 216 #ifdef CONFIG_DYNAMIC_FTRACE
 217 static int update_count(void **data)
 218 {
 219         unsigned long *count = (long *)data;
 220
 221         if (!*count)
 222                 return 0;
 223
 224         if (*count != -1)
 225                 (*count)--;
 226
 227         return 1;
 228 }
 229
 230 static void
 231 ftrace_traceon_count(unsigned long ip, unsigned long parent_ip, void **data)
 232 {
 233         if (tracing_is_on())
 234                 return;
 235
 236         if (update_count(data))
 237                 tracing_on();
 238 }
 239
 240 static void
 241 ftrace_traceoff_count(unsigned long ip, unsigned long parent_ip, void **data)
 242 {
 243         if (!tracing_is_on())
 244                 return;
 245
 246         if (update_count(data))
 247                 tracing_off();
 248 }
 249
 250 static void
 251 ftrace_traceon(unsigned long ip, unsigned long parent_ip, void **data)
 252 {
 253         if (tracing_is_on())
 254                 return;
 255
 256         tracing_on();
 257 }
 258
 259 static void
 260 ftrace_traceoff(unsigned long ip, unsigned long parent_ip, void **data)
 261 {
 262         if (!tracing_is_on())
 263                 return;
 264
 265         tracing_off();
 266 }
 267
 268 /*
 269  * Skip 4:
 270  *   ftrace_stacktrace()
 271  *   function_trace_probe_call()
 272  *   ftrace_ops_list_func()
 273  *   ftrace_call()
 274  */
 275 #define STACK_SKIP 4
 276
 277 static void
 278 ftrace_stacktrace(unsigned long ip, unsigned long parent_ip, void **data)
 279 {
 280         trace_dump_stack(STACK_SKIP);
 281 }
 282
 283 static void
 284 ftrace_stacktrace_count(unsigned long ip, unsigned long parent_ip, void **data)
 285 {
 286         if (!tracing_is_on())
 287                 return;
 288
 289         if (update_count(data))
 290                 trace_dump_stack(STACK_SKIP);
 291 }
 292
 293 static int
 294 ftrace_probe_print(const char *name, struct seq_file *m,
 295                    unsigned long ip, void *data)
 296 {
 297         long count = (long)data;
 298
 299         seq_printf(m, "%ps:%s", (void *)ip, name);
 300
 301         if (count == -1)
 302                 seq_printf(m, ":unlimited\n");
 303         else
 304                 seq_printf(m, ":count=%ld\n", count);
 305
 306         return 0;
 307 }
 308
 309 static int
 310 ftrace_traceon_print(struct seq_file *m, unsigned long ip,
 311                          struct ftrace_probe_ops *ops, void *data)
 312 {
 313         return ftrace_probe_print("traceon", m, ip, data);
 314 }
 315
 316 static int
 317 ftrace_traceoff_print(struct seq_file *m, unsigned long ip,
 318                          struct ftrace_probe_ops *ops, void *data)
 319 {
 320         return ftrace_probe_print("traceoff", m, ip, data);
 321 }
 322
 323 static int
 324 ftrace_stacktrace_print(struct seq_file *m, unsigned long ip,
 325                         struct ftrace_probe_ops *ops, void *data)
 326 {
 327         return ftrace_probe_print("stacktrace", m, ip, data);
 328 }
 329
 330 static struct ftrace_probe_ops traceon_count_probe_ops = {
 331         .func                   = ftrace_traceon_count,
 332         .print                  = ftrace_traceon_print,
 333 };
 334
 335 static struct ftrace_probe_ops traceoff_count_probe_ops = {
 336         .func                   = ftrace_traceoff_count,
 337         .print                  = ftrace_traceoff_print,
 338 };
 339
 340 static struct ftrace_probe_ops stacktrace_count_probe_ops = {
 341         .func                   = ftrace_stacktrace_count,
 342         .print                  = ftrace_stacktrace_print,
 343 };
 344
 345 static struct ftrace_probe_ops traceon_probe_ops = {
 346         .func                   = ftrace_traceon,
 347         .print                  = ftrace_traceon_print,
 348 };
 349
 350 static struct ftrace_probe_ops traceoff_probe_ops = {
 351         .func                   = ftrace_traceoff,
 352         .print                  = ftrace_traceoff_print,
 353 };
 354
 355 static struct ftrace_probe_ops stacktrace_probe_ops = {
 356         .func                   = ftrace_stacktrace,
 357         .print                  = ftrace_stacktrace_print,
 358 };
 359
 360 static int
 361 ftrace_trace_probe_callback(struct ftrace_probe_ops *ops,
 362                             struct ftrace_hash *hash, char *glob,
 363                             char *cmd, char *param, int enable)
 364 {
 365         void *count = (void *)-1;
 366         char *number;
 367         int ret;
 368
 369         /* hash funcs only work with set_ftrace_filter */
 370         if (!enable)
 371                 return -EINVAL;
 372
 373         if (glob[0] == '!') {
 374                 unregister_ftrace_function_probe_func(glob+1, ops);
 375                 return 0;
 376         }
 377
 378         if (!param)
 379                 goto out_reg;
 380
 381         number = strsep(&param, ":");
 382
 383         if (!strlen(number))
 384                 goto out_reg;
 385
 386         /*
 387          * We use the callback data field (which is a pointer)
 388          * as our counter.
 389          */
 390         ret = kstrtoul(number, 0, (unsigned long *)&count);
 391         if (ret)
 392                 return ret;
 393
 394  out_reg:
 395         ret = register_ftrace_function_probe(glob, ops, count);
 396
 397         return ret < 0 ? ret : 0;
 398 }
 399
 400 static int
 401 ftrace_trace_onoff_callback(struct ftrace_hash *hash,
 402                             char *glob, char *cmd, char *param, int enable)
 403 {
 404         struct ftrace_probe_ops *ops;
 405
 406         /* we register both traceon and traceoff to this callback */
 407         if (strcmp(cmd, "traceon") == 0)
 408                 ops = param ? &traceon_count_probe_ops : &traceon_probe_ops;
 409         else
 410                 ops = param ? &traceoff_count_probe_ops : &traceoff_probe_ops;
 411
 412         return ftrace_trace_probe_callback(ops, hash, glob, cmd,
 413                                            param, enable);
 414 }
 415
 416 static int
 417 ftrace_stacktrace_callback(struct ftrace_hash *hash,
 418                            char *glob, char *cmd, char *param, int enable)
 419 {
 420         struct ftrace_probe_ops *ops;
 421
 422         ops = param ? &stacktrace_count_probe_ops : &stacktrace_probe_ops;
 423
 424         return ftrace_trace_probe_callback(ops, hash, glob, cmd,
 425                                            param, enable);
 426 }
 427
 428 static struct ftrace_func_command ftrace_traceon_cmd = {
 429         .name                   = "traceon",
 430         .func                   = ftrace_trace_onoff_callback,
 431 };
 432
 433 static struct ftrace_func_command ftrace_traceoff_cmd = {
 434         .name                   = "traceoff",
 435         .func                   = ftrace_trace_onoff_callback,
 436 };
 437
 438 static struct ftrace_func_command ftrace_stacktrace_cmd = {
 439         .name                   = "stacktrace",
 440         .func                   = ftrace_stacktrace_callback,
 441 };
 442
 443 static int __init init_func_cmd_traceon(void)
 444 {
 445         int ret;
 446
 447         ret = register_ftrace_command(&ftrace_traceoff_cmd);
 448         if (ret)
 449                 return ret;
 450
 451         ret = register_ftrace_command(&ftrace_traceon_cmd);
 452         if (ret)
 453                 unregister_ftrace_command(&ftrace_traceoff_cmd);
 454
 455         ret = register_ftrace_command(&ftrace_stacktrace_cmd);
 456         if (ret) {
 457                 unregister_ftrace_command(&ftrace_traceoff_cmd);
 458                 unregister_ftrace_command(&ftrace_traceon_cmd);
 459         }
 460         return ret;
 461 }
 462 #else
 463 static inline int init_func_cmd_traceon(void)
 464 {
 465         return 0;
 466 }
 467 #endif /* CONFIG_DYNAMIC_FTRACE */
 468
 469 static __init int init_function_trace(void)
 470 {
 471         init_func_cmd_traceon();
 472         return register_tracer(&function_trace);
 473 }
 474 core_initcall(init_function_trace);