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 };
 153
 154 static struct ftrace_ops trace_stack_ops __read_mostly =
 155 {
 156         .func = function_stack_trace_call,
 157 };
 158
 159 /* Our two options */
 160 enum {
 161         TRACE_FUNC_OPT_STACK = 0x1,
 162 };
 163
 164 static struct tracer_opt func_opts[] = {
 165 #ifdef CONFIG_STACKTRACE
 166         { TRACER_OPT(func_stack_trace, TRACE_FUNC_OPT_STACK) },
 167 #endif
 168         { } /* Always set a last empty entry */
 169 };
 170
 171 static struct tracer_flags func_flags = {
 172         .val = 0, /* By default: all flags disabled */
 173         .opts = func_opts
 174 };
 175
 176 static void tracing_start_function_trace(void)
 177 {
 178         ftrace_function_enabled = 0;
 179
 180         if (trace_flags & TRACE_ITER_PREEMPTONLY)
 181                 trace_ops.func = function_trace_call_preempt_only;
 182         else
 183                 trace_ops.func = function_trace_call;
 184
 185         if (func_flags.val & TRACE_FUNC_OPT_STACK)
 186                 register_ftrace_function(&trace_stack_ops);
 187         else
 188                 register_ftrace_function(&trace_ops);
 189
 190         ftrace_function_enabled = 1;
 191 }
 192
 193 static void tracing_stop_function_trace(void)
 194 {
 195         ftrace_function_enabled = 0;
 196
 197         if (func_flags.val & TRACE_FUNC_OPT_STACK)
 198                 unregister_ftrace_function(&trace_stack_ops);
 199         else
 200                 unregister_ftrace_function(&trace_ops);
 201 }
 202
 203 static int func_set_flag(u32 old_flags, u32 bit, int set)
 204 {
 205         if (bit == TRACE_FUNC_OPT_STACK) {
 206                 /* do nothing if already set */
 207                 if (!!set == !!(func_flags.val & TRACE_FUNC_OPT_STACK))
 208                         return 0;
 209
 210                 if (set) {
 211                         unregister_ftrace_function(&trace_ops);
 212                         register_ftrace_function(&trace_stack_ops);
 213                 } else {
 214                         unregister_ftrace_function(&trace_stack_ops);
 215                         register_ftrace_function(&trace_ops);
 216                 }
 217
 218                 return 0;
 219         }
 220
 221         return -EINVAL;
 222 }
 223
 224 static struct tracer function_trace __read_mostly =
 225 {
 226         .name           = "function",
 227         .init           = function_trace_init,
 228         .reset          = function_trace_reset,
 229         .start          = function_trace_start,
 230         .wait_pipe      = poll_wait_pipe,
 231         .flags          = &func_flags,
 232         .set_flag       = func_set_flag,
 233 #ifdef CONFIG_FTRACE_SELFTEST
 234         .selftest       = trace_selftest_startup_function,
 235 #endif
 236 };
 237
 238 #ifdef CONFIG_DYNAMIC_FTRACE
 239 static void
 240 ftrace_traceon(unsigned long ip, unsigned long parent_ip, void **data)
 241 {
 242         long *count = (long *)data;
 243
 244         if (tracing_is_on())
 245                 return;
 246
 247         if (!*count)
 248                 return;
 249
 250         if (*count != -1)
 251                 (*count)--;
 252
 253         tracing_on();
 254 }
 255
 256 static void
 257 ftrace_traceoff(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_off();
 271 }
 272
 273 static int
 274 ftrace_trace_onoff_print(struct seq_file *m, unsigned long ip,
 275                          struct ftrace_probe_ops *ops, void *data);
 276
 277 static struct ftrace_probe_ops traceon_probe_ops = {
 278         .func                   = ftrace_traceon,
 279         .print                  = ftrace_trace_onoff_print,
 280 };
 281
 282 static struct ftrace_probe_ops traceoff_probe_ops = {
 283         .func                   = ftrace_traceoff,
 284         .print                  = ftrace_trace_onoff_print,
 285 };
 286
 287 static int
 288 ftrace_trace_onoff_print(struct seq_file *m, unsigned long ip,
 289                          struct ftrace_probe_ops *ops, void *data)
 290 {
 291         long count = (long)data;
 292
 293         seq_printf(m, "%ps:", (void *)ip);
 294
 295         if (ops == &traceon_probe_ops)
 296                 seq_printf(m, "traceon");
 297         else
 298                 seq_printf(m, "traceoff");
 299
 300         if (count == -1)
 301                 seq_printf(m, ":unlimited\n");
 302         else
 303                 seq_printf(m, ":count=%ld\n", count);
 304
 305         return 0;
 306 }
 307
 308 static int
 309 ftrace_trace_onoff_unreg(char *glob, char *cmd, char *param)
 310 {
 311         struct ftrace_probe_ops *ops;
 312
 313         /* we register both traceon and traceoff to this callback */
 314         if (strcmp(cmd, "traceon") == 0)
 315                 ops = &traceon_probe_ops;
 316         else
 317                 ops = &traceoff_probe_ops;
 318
 319         unregister_ftrace_function_probe_func(glob, ops);
 320
 321         return 0;
 322 }
 323
 324 static int
 325 ftrace_trace_onoff_callback(char *glob, char *cmd, char *param, int enable)
 326 {
 327         struct ftrace_probe_ops *ops;
 328         void *count = (void *)-1;
 329         char *number;
 330         int ret;
 331
 332         /* hash funcs only work with set_ftrace_filter */
 333         if (!enable)
 334                 return -EINVAL;
 335
 336         if (glob[0] == '!')
 337                 return ftrace_trace_onoff_unreg(glob+1, cmd, param);
 338
 339         /* we register both traceon and traceoff to this callback */
 340         if (strcmp(cmd, "traceon") == 0)
 341                 ops = &traceon_probe_ops;
 342         else
 343                 ops = &traceoff_probe_ops;
 344
 345         if (!param)
 346                 goto out_reg;
 347
 348         number = strsep(&param, ":");
 349
 350         if (!strlen(number))
 351                 goto out_reg;
 352
 353         /*
 354          * We use the callback data field (which is a pointer)
 355          * as our counter.
 356          */
 357         ret = strict_strtoul(number, 0, (unsigned long *)&count);
 358         if (ret)
 359                 return ret;
 360
 361  out_reg:
 362         ret = register_ftrace_function_probe(glob, ops, count);
 363
 364         return ret < 0 ? ret : 0;
 365 }
 366
 367 static struct ftrace_func_command ftrace_traceon_cmd = {
 368         .name                   = "traceon",
 369         .func                   = ftrace_trace_onoff_callback,
 370 };
 371
 372 static struct ftrace_func_command ftrace_traceoff_cmd = {
 373         .name                   = "traceoff",
 374         .func                   = ftrace_trace_onoff_callback,
 375 };
 376
 377 static int __init init_func_cmd_traceon(void)
 378 {
 379         int ret;
 380
 381         ret = register_ftrace_command(&ftrace_traceoff_cmd);
 382         if (ret)
 383                 return ret;
 384
 385         ret = register_ftrace_command(&ftrace_traceon_cmd);
 386         if (ret)
 387                 unregister_ftrace_command(&ftrace_traceoff_cmd);
 388         return ret;
 389 }
 390 #else
 391 static inline int init_func_cmd_traceon(void)
 392 {
 393         return 0;
 394 }
 395 #endif /* CONFIG_DYNAMIC_FTRACE */
 396
 397 static __init int init_function_trace(void)
 398 {
 399         init_func_cmd_traceon();
 400         return register_tracer(&function_trace);
 401 }
 402 device_initcall(init_function_trace);
 403