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