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