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 William Lee Irwin III
  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/pstore.h>
  17 #include <linux/fs.h>
  18
  19 #include "trace.h"
  20
  21 /* function tracing enabled */
  22 static int                      ftrace_function_enabled;
  23
  24 static struct trace_array       *func_trace;
  25
  26 static void tracing_start_function_trace(void);
  27 static void tracing_stop_function_trace(void);
  28
  29 static int function_trace_init(struct trace_array *tr)
  30 {
  31         func_trace = tr;
  32         tr->cpu = get_cpu();
  33         put_cpu();
  34
  35         tracing_start_cmdline_record();
  36         tracing_start_function_trace();
  37         return 0;
  38 }
  39
  40 static void function_trace_reset(struct trace_array *tr)
  41 {
  42         tracing_stop_function_trace();
  43         tracing_stop_cmdline_record();
  44 }
  45
  46 static void function_trace_start(struct trace_array *tr)
  47 {
  48         tracing_reset_online_cpus(tr);
  49 }
  50
  51 static void
  52 function_trace_call_preempt_only(unsigned long ip, unsigned long parent_ip)
  53 {
  54         struct trace_array *tr = func_trace;
  55         struct trace_array_cpu *data;
  56         unsigned long flags;
  57         long disabled;
  58         int cpu;
  59         int pc;
  60
  61         if (unlikely(!ftrace_function_enabled))
  62                 return;
  63
  64         pc = preempt_count();
  65         preempt_disable_notrace();
  66         local_save_flags(flags);
  67         cpu = raw_smp_processor_id();
  68         data = tr->data[cpu];
  69         disabled = atomic_inc_return(&data->disabled);
  70
  71         if (likely(disabled == 1))
  72                 trace_function(tr, ip, parent_ip, flags, pc);
  73
  74         atomic_dec(&data->disabled);
  75         preempt_enable_notrace();
  76 }
  77
  78 /* Our two options */
  79 enum {
  80         TRACE_FUNC_OPT_STACK    = 0x1,
  81         TRACE_FUNC_OPT_PSTORE   = 0x2,
  82 };
  83
  84 static struct tracer_flags func_flags;
  85
  86 static void
  87 function_trace_call(unsigned long ip, unsigned long parent_ip)
  88 {
  89         struct trace_array *tr = func_trace;
  90         struct trace_array_cpu *data;
  91         unsigned long flags;
  92         long disabled;
  93         int cpu;
  94         int pc;
  95
  96         if (unlikely(!ftrace_function_enabled))
  97                 return;
  98
  99         /*
 100          * Need to use raw, since this must be called before the
 101          * recursive protection is performed.
 102          */
 103         local_irq_save(flags);
 104         cpu = raw_smp_processor_id();
 105         data = tr->data[cpu];
 106         disabled = atomic_inc_return(&data->disabled);
 107
 108         if (likely(disabled == 1)) {
 109                 /*
 110                  * So far tracing doesn't support multiple buffers, so
 111                  * we make an explicit call for now.
 112                  */
 113                 if (unlikely(func_flags.val & TRACE_FUNC_OPT_PSTORE))
 114                         pstore_ftrace_call(ip, parent_ip);
 115                 pc = preempt_count();
 116                 trace_function(tr, ip, parent_ip, flags, pc);
 117         }
 118
 119         atomic_dec(&data->disabled);
 120         local_irq_restore(flags);
 121 }
 122
 123 static void
 124 function_stack_trace_call(unsigned long ip, unsigned long parent_ip)
 125 {
 126         struct trace_array *tr = func_trace;
 127         struct trace_array_cpu *data;
 128         unsigned long flags;
 129         long disabled;
 130         int cpu;
 131         int pc;
 132
 133         if (unlikely(!ftrace_function_enabled))
 134                 return;
 135
 136         /*
 137          * Need to use raw, since this must be called before the
 138          * recursive protection is performed.
 139          */
 140         local_irq_save(flags);
 141         cpu = raw_smp_processor_id();
 142         data = tr->data[cpu];
 143         disabled = atomic_inc_return(&data->disabled);
 144
 145         if (likely(disabled == 1)) {
 146                 pc = preempt_count();
 147                 trace_function(tr, ip, parent_ip, flags, pc);
 148                 /*
 149                  * skip over 5 funcs:
 150                  *    __ftrace_trace_stack,
 151                  *    __trace_stack,
 152                  *    function_stack_trace_call
 153                  *    ftrace_list_func
 154                  *    ftrace_call
 155                  */
 156                 __trace_stack(tr, flags, 5, pc);
 157         }
 158
 159         atomic_dec(&data->disabled);
 160         local_irq_restore(flags);
 161 }
 162
 163
 164 static struct ftrace_ops trace_ops __read_mostly =
 165 {
 166         .func = function_trace_call,
 167         .flags = FTRACE_OPS_FL_GLOBAL,
 168 };
 169
 170 static struct ftrace_ops trace_stack_ops __read_mostly =
 171 {
 172         .func = function_stack_trace_call,
 173         .flags = FTRACE_OPS_FL_GLOBAL,
 174 };
 175
 176 static struct tracer_opt func_opts[] = {
 177 #ifdef CONFIG_STACKTRACE
 178         { TRACER_OPT(func_stack_trace, TRACE_FUNC_OPT_STACK) },
 179 #endif
 180 #ifdef CONFIG_PSTORE_FTRACE
 181         { TRACER_OPT(func_pstore, TRACE_FUNC_OPT_PSTORE) },
 182 #endif
 183         { } /* Always set a last empty entry */
 184 };
 185
 186 static struct tracer_flags func_flags = {
 187         .val = 0, /* By default: all flags disabled */
 188         .opts = func_opts
 189 };
 190
 191 static void tracing_start_function_trace(void)
 192 {
 193         ftrace_function_enabled = 0;
 194
 195         if (trace_flags & TRACE_ITER_PREEMPTONLY)
 196                 trace_ops.func = function_trace_call_preempt_only;
 197         else
 198                 trace_ops.func = function_trace_call;
 199
 200         if (func_flags.val & TRACE_FUNC_OPT_STACK)
 201                 register_ftrace_function(&trace_stack_ops);
 202         else
 203                 register_ftrace_function(&trace_ops);
 204
 205         ftrace_function_enabled = 1;
 206 }
 207
 208 static void tracing_stop_function_trace(void)
 209 {
 210         ftrace_function_enabled = 0;
 211
 212         if (func_flags.val & TRACE_FUNC_OPT_STACK)
 213                 unregister_ftrace_function(&trace_stack_ops);
 214         else
 215                 unregister_ftrace_function(&trace_ops);
 216 }
 217
 218 static int func_set_flag(u32 old_flags, u32 bit, int set)
 219 {
 220         if (bit == TRACE_FUNC_OPT_STACK) {
 221                 /* do nothing if already set */
 222                 if (!!set == !!(func_flags.val & TRACE_FUNC_OPT_STACK))
 223                         return 0;
 224
 225                 if (set) {
 226                         unregister_ftrace_function(&trace_ops);
 227                         register_ftrace_function(&trace_stack_ops);
 228                 } else {
 229                         unregister_ftrace_function(&trace_stack_ops);
 230                         register_ftrace_function(&trace_ops);
 231                 }
 232
 233                 return 0;
 234         } else if (bit == TRACE_FUNC_OPT_PSTORE) {
 235                 return 0;
 236         }
 237
 238         return -EINVAL;
 239 }
 240
 241 static struct tracer function_trace __read_mostly =
 242 {
 243         .name           = "function",
 244         .init           = function_trace_init,
 245         .reset          = function_trace_reset,
 246         .start          = function_trace_start,
 247         .wait_pipe      = poll_wait_pipe,
 248         .flags          = &func_flags,
 249         .set_flag       = func_set_flag,
 250 #ifdef CONFIG_FTRACE_SELFTEST
 251         .selftest       = trace_selftest_startup_function,
 252 #endif
 253 };
 254
 255 #ifdef CONFIG_DYNAMIC_FTRACE
 256 static void
 257 ftrace_traceon(unsigned long ip, unsigned long parent_ip, void **data)
 258 {
 259         long *count = (long *)data;
 260
 261         if (tracing_is_on())
 262                 return;
 263
 264         if (!*count)
 265                 return;
 266
 267         if (*count != -1)
 268                 (*count)--;
 269
 270         tracing_on();
 271 }
 272
 273 static void
 274 ftrace_traceoff(unsigned long ip, unsigned long parent_ip, void **data)
 275 {
 276         long *count = (long *)data;
 277
 278         if (!tracing_is_on())
 279                 return;
 280
 281         if (!*count)
 282                 return;
 283
 284         if (*count != -1)
 285                 (*count)--;
 286
 287         tracing_off();
 288 }
 289
 290 static int
 291 ftrace_trace_onoff_print(struct seq_file *m, unsigned long ip,
 292                          struct ftrace_probe_ops *ops, void *data);
 293
 294 static struct ftrace_probe_ops traceon_probe_ops = {
 295         .func                   = ftrace_traceon,
 296         .print                  = ftrace_trace_onoff_print,
 297 };
 298
 299 static struct ftrace_probe_ops traceoff_probe_ops = {
 300         .func                   = ftrace_traceoff,
 301         .print                  = ftrace_trace_onoff_print,
 302 };
 303
 304 static int
 305 ftrace_trace_onoff_print(struct seq_file *m, unsigned long ip,
 306                          struct ftrace_probe_ops *ops, void *data)
 307 {
 308         long count = (long)data;
 309
 310         seq_printf(m, "%ps:", (void *)ip);
 311
 312         if (ops == &traceon_probe_ops)
 313                 seq_printf(m, "traceon");
 314         else
 315                 seq_printf(m, "traceoff");
 316
 317         if (count == -1)
 318                 seq_printf(m, ":unlimited\n");
 319         else
 320                 seq_printf(m, ":count=%ld\n", count);
 321
 322         return 0;
 323 }
 324
 325 static int
 326 ftrace_trace_onoff_unreg(char *glob, char *cmd, char *param)
 327 {
 328         struct ftrace_probe_ops *ops;
 329
 330         /* we register both traceon and traceoff to this callback */
 331         if (strcmp(cmd, "traceon") == 0)
 332                 ops = &traceon_probe_ops;
 333         else
 334                 ops = &traceoff_probe_ops;
 335
 336         unregister_ftrace_function_probe_func(glob, ops);
 337
 338         return 0;
 339 }
 340
 341 static int
 342 ftrace_trace_onoff_callback(struct ftrace_hash *hash,
 343                             char *glob, char *cmd, char *param, int enable)
 344 {
 345         struct ftrace_probe_ops *ops;
 346         void *count = (void *)-1;
 347         char *number;
 348         int ret;
 349
 350         /* hash funcs only work with set_ftrace_filter */
 351         if (!enable)
 352                 return -EINVAL;
 353
 354         if (glob[0] == '!')
 355                 return ftrace_trace_onoff_unreg(glob+1, cmd, param);
 356
 357         /* we register both traceon and traceoff to this callback */
 358         if (strcmp(cmd, "traceon") == 0)
 359                 ops = &traceon_probe_ops;
 360         else
 361                 ops = &traceoff_probe_ops;
 362
 363         if (!param)
 364                 goto out_reg;
 365
 366         number = strsep(&param, ":");
 367
 368         if (!strlen(number))
 369                 goto out_reg;
 370
 371         /*
 372          * We use the callback data field (which is a pointer)
 373          * as our counter.
 374          */
 375         ret = strict_strtoul(number, 0, (unsigned long *)&count);
 376         if (ret)
 377                 return ret;
 378
 379  out_reg:
 380         ret = register_ftrace_function_probe(glob, ops, count);
 381
 382         return ret < 0 ? ret : 0;
 383 }
 384
 385 static struct ftrace_func_command ftrace_traceon_cmd = {
 386         .name                   = "traceon",
 387         .func                   = ftrace_trace_onoff_callback,
 388 };
 389
 390 static struct ftrace_func_command ftrace_traceoff_cmd = {
 391         .name                   = "traceoff",
 392         .func                   = ftrace_trace_onoff_callback,
 393 };
 394
 395 static int __init init_func_cmd_traceon(void)
 396 {
 397         int ret;
 398
 399         ret = register_ftrace_command(&ftrace_traceoff_cmd);
 400         if (ret)
 401                 return ret;
 402
 403         ret = register_ftrace_command(&ftrace_traceon_cmd);
 404         if (ret)
 405                 unregister_ftrace_command(&ftrace_traceoff_cmd);
 406         return ret;
 407 }
 408 #else
 409 static inline int init_func_cmd_traceon(void)
 410 {
 411         return 0;
 412 }
 413 #endif /* CONFIG_DYNAMIC_FTRACE */
 414
 415 static __init int init_function_trace(void)
 416 {
 417         init_func_cmd_traceon();
 418         return register_tracer(&function_trace);
 419 }
 420 device_initcall(init_function_trace);
 421