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, resched;
  58         int pc;
  59
  60         if (unlikely(!ftrace_function_enabled))
  61                 return;
  62
  63         pc = preempt_count();
  64         resched = ftrace_preempt_disable();
  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         ftrace_preempt_enable(resched);
  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         /* OK if they are not registered */
 197         unregister_ftrace_function(&trace_stack_ops);
 198         unregister_ftrace_function(&trace_ops);
 199 }
 200
 201 static int func_set_flag(u32 old_flags, u32 bit, int set)
 202 {
 203         if (bit == TRACE_FUNC_OPT_STACK) {
 204                 /* do nothing if already set */
 205                 if (!!set == !!(func_flags.val & TRACE_FUNC_OPT_STACK))
 206                         return 0;
 207
 208                 if (set) {
 209                         unregister_ftrace_function(&trace_ops);
 210                         register_ftrace_function(&trace_stack_ops);
 211                 } else {
 212                         unregister_ftrace_function(&trace_stack_ops);
 213                         register_ftrace_function(&trace_ops);
 214                 }
 215
 216                 return 0;
 217         }
 218
 219         return -EINVAL;
 220 }
 221
 222 static struct tracer function_trace __read_mostly =
 223 {
 224         .name           = "function",
 225         .init           = function_trace_init,
 226         .reset          = function_trace_reset,
 227         .start          = function_trace_start,
 228         .flags          = &func_flags,
 229         .set_flag       = func_set_flag,
 230 #ifdef CONFIG_FTRACE_SELFTEST
 231         .selftest       = trace_selftest_startup_function,
 232 #endif
 233 };
 234
 235 #ifdef CONFIG_DYNAMIC_FTRACE
 236 static void
 237 ftrace_traceon(unsigned long ip, unsigned long parent_ip, void **data)
 238 {
 239         long *count = (long *)data;
 240
 241         if (tracing_is_on())
 242                 return;
 243
 244         if (!*count)
 245                 return;
 246
 247         if (*count != -1)
 248                 (*count)--;
 249
 250         tracing_on();
 251 }
 252
 253 static void
 254 ftrace_traceoff(unsigned long ip, unsigned long parent_ip, void **data)
 255 {
 256         long *count = (long *)data;
 257
 258         if (!tracing_is_on())
 259                 return;
 260
 261         if (!*count)
 262                 return;
 263
 264         if (*count != -1)
 265                 (*count)--;
 266
 267         tracing_off();
 268 }
 269
 270 static int
 271 ftrace_trace_onoff_print(struct seq_file *m, unsigned long ip,
 272                          struct ftrace_hook_ops *ops, void *data);
 273
 274 static struct ftrace_hook_ops traceon_hook_ops = {
 275         .func                   = ftrace_traceon,
 276         .print                  = ftrace_trace_onoff_print,
 277 };
 278
 279 static struct ftrace_hook_ops traceoff_hook_ops = {
 280         .func                   = ftrace_traceoff,
 281         .print                  = ftrace_trace_onoff_print,
 282 };
 283
 284 static int
 285 ftrace_trace_onoff_print(struct seq_file *m, unsigned long ip,
 286                          struct ftrace_hook_ops *ops, void *data)
 287 {
 288         char str[KSYM_SYMBOL_LEN];
 289         long count = (long)data;
 290
 291         kallsyms_lookup(ip, NULL, NULL, NULL, str);
 292         seq_printf(m, "%s:", str);
 293
 294         if (ops == &traceon_hook_ops)
 295                 seq_printf(m, "traceon");
 296         else
 297                 seq_printf(m, "traceoff");
 298
 299         if (count != -1)
 300                 seq_printf(m, ":count=%ld", count);
 301         seq_putc(m, '\n');
 302
 303         return 0;
 304 }
 305
 306 static int
 307 ftrace_trace_onoff_unreg(char *glob, char *cmd, char *param)
 308 {
 309         struct ftrace_hook_ops *ops;
 310
 311         /* we register both traceon and traceoff to this callback */
 312         if (strcmp(cmd, "traceon") == 0)
 313                 ops = &traceon_hook_ops;
 314         else
 315                 ops = &traceoff_hook_ops;
 316
 317         unregister_ftrace_function_hook_func(glob, ops);
 318
 319         return 0;
 320 }
 321
 322 static int
 323 ftrace_trace_onoff_callback(char *glob, char *cmd, char *param, int enable)
 324 {
 325         struct ftrace_hook_ops *ops;
 326         void *count = (void *)-1;
 327         char *number;
 328         int ret;
 329
 330         /* hash funcs only work with set_ftrace_filter */
 331         if (!enable)
 332                 return -EINVAL;
 333
 334         if (glob[0] == '!')
 335                 return ftrace_trace_onoff_unreg(glob+1, cmd, param);
 336
 337         /* we register both traceon and traceoff to this callback */
 338         if (strcmp(cmd, "traceon") == 0)
 339                 ops = &traceon_hook_ops;
 340         else
 341                 ops = &traceoff_hook_ops;
 342
 343         if (!param)
 344                 goto out_reg;
 345
 346         number = strsep(&param, ":");
 347
 348         if (!strlen(number))
 349                 goto out_reg;
 350
 351         /*
 352          * We use the callback data field (which is a pointer)
 353          * as our counter.
 354          */
 355         ret = strict_strtoul(number, 0, (unsigned long *)&count);
 356         if (ret)
 357                 return ret;
 358
 359  out_reg:
 360         ret = register_ftrace_function_hook(glob, ops, count);
 361
 362         return ret;
 363 }
 364
 365 static struct ftrace_func_command ftrace_traceon_cmd = {
 366         .name                   = "traceon",
 367         .func                   = ftrace_trace_onoff_callback,
 368 };
 369
 370 static struct ftrace_func_command ftrace_traceoff_cmd = {
 371         .name                   = "traceoff",
 372         .func                   = ftrace_trace_onoff_callback,
 373 };
 374
 375 static int __init init_func_cmd_traceon(void)
 376 {
 377         int ret;
 378
 379         ret = register_ftrace_command(&ftrace_traceoff_cmd);
 380         if (ret)
 381                 return ret;
 382
 383         ret = register_ftrace_command(&ftrace_traceon_cmd);
 384         if (ret)
 385                 unregister_ftrace_command(&ftrace_traceoff_cmd);
 386         return ret;
 387 }
 388 #else
 389 static inline int init_func_cmd_traceon(void)
 390 {
 391         return 0;
 392 }
 393 #endif /* CONFIG_DYNAMIC_FTRACE */
 394
 395 static __init int init_function_trace(void)
 396 {
 397         init_func_cmd_traceon();
 398         return register_tracer(&function_trace);
 399 }
 400
 401 device_initcall(init_function_trace);
 402