kernel/trace/trace_events.c

   1 /*
   2  * event tracer
   3  *
   4  * Copyright (C) 2008 Red Hat Inc, Steven Rostedt <srostedt@redhat.com>
   5  *
   6  */
   7
   8 #include <linux/debugfs.h>
   9 #include <linux/uaccess.h>
  10 #include <linux/module.h>
  11 #include <linux/ctype.h>
  12
  13 #include "trace.h"
  14
  15 #define TRACE_SYSTEM "TRACE_SYSTEM"
  16
  17 #define events_for_each(event)                                          \
  18         for (event = __start_ftrace_events;                             \
  19              (unsigned long)event < (unsigned long)__stop_ftrace_events; \
  20              event++)
  21
  22 void event_trace_printk(unsigned long ip, const char *fmt, ...)
  23 {
  24         va_list ap;
  25
  26         va_start(ap, fmt);
  27         tracing_record_cmdline(current);
  28         trace_vprintk(ip, task_curr_ret_stack(current), fmt, ap);
  29         va_end(ap);
  30 }
  31
  32 static void ftrace_clear_events(void)
  33 {
  34         struct ftrace_event_call *call = (void *)__start_ftrace_events;
  35
  36
  37         while ((unsigned long)call < (unsigned long)__stop_ftrace_events) {
  38
  39                 if (call->enabled) {
  40                         call->enabled = 0;
  41                         call->unregfunc();
  42                 }
  43                 call++;
  44         }
  45 }
  46
  47 static int ftrace_set_clr_event(char *buf, int set)
  48 {
  49         struct ftrace_event_call *call = __start_ftrace_events;
  50         char *event = NULL, *sub = NULL, *match;
  51         int ret = -EINVAL;
  52
  53         /*
  54          * The buf format can be <subsystem>:<event-name>
  55          *  *:<event-name> means any event by that name.
  56          *  :<event-name> is the same.
  57          *
  58          *  <subsystem>:* means all events in that subsystem
  59          *  <subsystem>: means the same.
  60          *
  61          *  <name> (no ':') means all events in a subsystem with
  62          *  the name <name> or any event that matches <name>
  63          */
  64
  65         match = strsep(&buf, ":");
  66         if (buf) {
  67                 sub = match;
  68                 event = buf;
  69                 match = NULL;
  70
  71                 if (!strlen(sub) || strcmp(sub, "*") == 0)
  72                         sub = NULL;
  73                 if (!strlen(event) || strcmp(event, "*") == 0)
  74                         event = NULL;
  75         }
  76
  77         events_for_each(call) {
  78
  79                 if (!call->name)
  80                         continue;
  81
  82                 if (match &&
  83                     strcmp(match, call->name) != 0 &&
  84                     strcmp(match, call->system) != 0)
  85                         continue;
  86
  87                 if (sub && strcmp(sub, call->system) != 0)
  88                         continue;
  89
  90                 if (event && strcmp(event, call->name) != 0)
  91                         continue;
  92
  93                 if (set) {
  94                         /* Already set? */
  95                         if (call->enabled)
  96                                 return 0;
  97                         call->enabled = 1;
  98                         call->regfunc();
  99                 } else {
 100                         /* Already cleared? */
 101                         if (!call->enabled)
 102                                 return 0;
 103                         call->enabled = 0;
 104                         call->unregfunc();
 105                 }
 106                 ret = 0;
 107         }
 108         return ret;
 109 }
 110
 111 /* 128 should be much more than enough */
 112 #define EVENT_BUF_SIZE          127
 113
 114 static ssize_t
 115 ftrace_event_write(struct file *file, const char __user *ubuf,
 116                    size_t cnt, loff_t *ppos)
 117 {
 118         size_t read = 0;
 119         int i, set = 1;
 120         ssize_t ret;
 121         char *buf;
 122         char ch;
 123
 124         if (!cnt || cnt < 0)
 125                 return 0;
 126
 127         ret = get_user(ch, ubuf++);
 128         if (ret)
 129                 return ret;
 130         read++;
 131         cnt--;
 132
 133         /* skip white space */
 134         while (cnt && isspace(ch)) {
 135                 ret = get_user(ch, ubuf++);
 136                 if (ret)
 137                         return ret;
 138                 read++;
 139                 cnt--;
 140         }
 141
 142         /* Only white space found? */
 143         if (isspace(ch)) {
 144                 file->f_pos += read;
 145                 ret = read;
 146                 return ret;
 147         }
 148
 149         buf = kmalloc(EVENT_BUF_SIZE+1, GFP_KERNEL);
 150         if (!buf)
 151                 return -ENOMEM;
 152
 153         if (cnt > EVENT_BUF_SIZE)
 154                 cnt = EVENT_BUF_SIZE;
 155
 156         i = 0;
 157         while (cnt && !isspace(ch)) {
 158                 if (!i && ch == '!')
 159                         set = 0;
 160                 else
 161                         buf[i++] = ch;
 162
 163                 ret = get_user(ch, ubuf++);
 164                 if (ret)
 165                         goto out_free;
 166                 read++;
 167                 cnt--;
 168         }
 169         buf[i] = 0;
 170
 171         file->f_pos += read;
 172
 173         ret = ftrace_set_clr_event(buf, set);
 174         if (ret)
 175                 goto out_free;
 176
 177         ret = read;
 178
 179  out_free:
 180         kfree(buf);
 181
 182         return ret;
 183 }
 184
 185 static void *
 186 t_next(struct seq_file *m, void *v, loff_t *pos)
 187 {
 188         struct ftrace_event_call *call = m->private;
 189         struct ftrace_event_call *next = call;
 190
 191         (*pos)++;
 192
 193         if ((unsigned long)call >= (unsigned long)__stop_ftrace_events)
 194                 return NULL;
 195
 196         m->private = ++next;
 197
 198         return call;
 199 }
 200
 201 static void *t_start(struct seq_file *m, loff_t *pos)
 202 {
 203         return t_next(m, NULL, pos);
 204 }
 205
 206 static void *
 207 s_next(struct seq_file *m, void *v, loff_t *pos)
 208 {
 209         struct ftrace_event_call *call = m->private;
 210         struct ftrace_event_call *next;
 211
 212         (*pos)++;
 213
 214  retry:
 215         if ((unsigned long)call >= (unsigned long)__stop_ftrace_events)
 216                 return NULL;
 217
 218         if (!call->enabled) {
 219                 call++;
 220                 goto retry;
 221         }
 222
 223         next = call;
 224         m->private = ++next;
 225
 226         return call;
 227 }
 228
 229 static void *s_start(struct seq_file *m, loff_t *pos)
 230 {
 231         return s_next(m, NULL, pos);
 232 }
 233
 234 static int t_show(struct seq_file *m, void *v)
 235 {
 236         struct ftrace_event_call *call = v;
 237
 238         if (strcmp(call->system, TRACE_SYSTEM) != 0)
 239                 seq_printf(m, "%s:", call->system);
 240         seq_printf(m, "%s\n", call->name);
 241
 242         return 0;
 243 }
 244
 245 static void t_stop(struct seq_file *m, void *p)
 246 {
 247 }
 248
 249 static int
 250 ftrace_event_seq_open(struct inode *inode, struct file *file)
 251 {
 252         int ret;
 253         const struct seq_operations *seq_ops;
 254
 255         if ((file->f_mode & FMODE_WRITE) &&
 256             !(file->f_flags & O_APPEND))
 257                 ftrace_clear_events();
 258
 259         seq_ops = inode->i_private;
 260         ret = seq_open(file, seq_ops);
 261         if (!ret) {
 262                 struct seq_file *m = file->private_data;
 263
 264                 m->private = __start_ftrace_events;
 265         }
 266         return ret;
 267 }
 268
 269 static ssize_t
 270 event_enable_read(struct file *filp, char __user *ubuf, size_t cnt,
 271                   loff_t *ppos)
 272 {
 273         struct ftrace_event_call *call = filp->private_data;
 274         char *buf;
 275
 276         if (call->enabled)
 277                 buf = "1\n";
 278         else
 279                 buf = "0\n";
 280
 281         return simple_read_from_buffer(ubuf, cnt, ppos, buf, 2);
 282 }
 283
 284 static ssize_t
 285 event_enable_write(struct file *filp, const char __user *ubuf, size_t cnt,
 286                    loff_t *ppos)
 287 {
 288         struct ftrace_event_call *call = filp->private_data;
 289         char buf[64];
 290         unsigned long val;
 291         int ret;
 292
 293         if (cnt >= sizeof(buf))
 294                 return -EINVAL;
 295
 296         if (copy_from_user(&buf, ubuf, cnt))
 297                 return -EFAULT;
 298
 299         buf[cnt] = 0;
 300
 301         ret = strict_strtoul(buf, 10, &val);
 302         if (ret < 0)
 303                 return ret;
 304
 305         switch (val) {
 306         case 0:
 307                 if (!call->enabled)
 308                         break;
 309
 310                 call->enabled = 0;
 311                 call->unregfunc();
 312                 break;
 313         case 1:
 314                 if (call->enabled)
 315                         break;
 316
 317                 call->enabled = 1;
 318                 call->regfunc();
 319                 break;
 320
 321         default:
 322                 return -EINVAL;
 323         }
 324
 325         *ppos += cnt;
 326
 327         return cnt;
 328 }
 329
 330 static const struct seq_operations show_event_seq_ops = {
 331         .start = t_start,
 332         .next = t_next,
 333         .show = t_show,
 334         .stop = t_stop,
 335 };
 336
 337 static const struct seq_operations show_set_event_seq_ops = {
 338         .start = s_start,
 339         .next = s_next,
 340         .show = t_show,
 341         .stop = t_stop,
 342 };
 343
 344 static const struct file_operations ftrace_avail_fops = {
 345         .open = ftrace_event_seq_open,
 346         .read = seq_read,
 347         .llseek = seq_lseek,
 348         .release = seq_release,
 349 };
 350
 351 static const struct file_operations ftrace_set_event_fops = {
 352         .open = ftrace_event_seq_open,
 353         .read = seq_read,
 354         .write = ftrace_event_write,
 355         .llseek = seq_lseek,
 356         .release = seq_release,
 357 };
 358
 359 static const struct file_operations ftrace_enable_fops = {
 360         .open = tracing_open_generic,
 361         .read = event_enable_read,
 362         .write = event_enable_write,
 363 };
 364
 365 static struct dentry *event_trace_events_dir(void)
 366 {
 367         static struct dentry *d_tracer;
 368         static struct dentry *d_events;
 369
 370         if (d_events)
 371                 return d_events;
 372
 373         d_tracer = tracing_init_dentry();
 374         if (!d_tracer)
 375                 return NULL;
 376
 377         d_events = debugfs_create_dir("events", d_tracer);
 378         if (!d_events)
 379                 pr_warning("Could not create debugfs "
 380                            "'events' directory\n");
 381
 382         return d_events;
 383 }
 384
 385 struct event_subsystem {
 386         struct list_head        list;
 387         const char              *name;
 388         struct dentry           *entry;
 389 };
 390
 391 static LIST_HEAD(event_subsystems);
 392
 393 static struct dentry *
 394 event_subsystem_dir(const char *name, struct dentry *d_events)
 395 {
 396         struct event_subsystem *system;
 397
 398         /* First see if we did not already create this dir */
 399         list_for_each_entry(system, &event_subsystems, list) {
 400                 if (strcmp(system->name, name) == 0)
 401                         return system->entry;
 402         }
 403
 404         /* need to create new entry */
 405         system = kmalloc(sizeof(*system), GFP_KERNEL);
 406         if (!system) {
 407                 pr_warning("No memory to create event subsystem %s\n",
 408                            name);
 409                 return d_events;
 410         }
 411
 412         system->entry = debugfs_create_dir(name, d_events);
 413         if (!system->entry) {
 414                 pr_warning("Could not create event subsystem %s\n",
 415                            name);
 416                 kfree(system);
 417                 return d_events;
 418         }
 419
 420         system->name = name;
 421         list_add(&system->list, &event_subsystems);
 422
 423         return system->entry;
 424 }
 425
 426 static int
 427 event_create_dir(struct ftrace_event_call *call, struct dentry *d_events)
 428 {
 429         struct dentry *entry;
 430
 431         /*
 432          * If the trace point header did not define TRACE_SYSTEM
 433          * then the system would be called "TRACE_SYSTEM".
 434          */
 435         if (strcmp(call->system, "TRACE_SYSTEM") != 0)
 436                 d_events = event_subsystem_dir(call->system, d_events);
 437
 438         call->dir = debugfs_create_dir(call->name, d_events);
 439         if (!call->dir) {
 440                 pr_warning("Could not create debugfs "
 441                            "'%s' directory\n", call->name);
 442                 return -1;
 443         }
 444
 445         entry = debugfs_create_file("enable", 0644, call->dir, call,
 446                                     &ftrace_enable_fops);
 447         if (!entry)
 448                 pr_warning("Could not create debugfs "
 449                            "'%s/enable' entry\n", call->name);
 450
 451         return 0;
 452 }
 453
 454 static __init int event_trace_init(void)
 455 {
 456         struct ftrace_event_call *call = __start_ftrace_events;
 457         struct dentry *d_tracer;
 458         struct dentry *entry;
 459         struct dentry *d_events;
 460
 461         d_tracer = tracing_init_dentry();
 462         if (!d_tracer)
 463                 return 0;
 464
 465         entry = debugfs_create_file("available_events", 0444, d_tracer,
 466                                     (void *)&show_event_seq_ops,
 467                                     &ftrace_avail_fops);
 468         if (!entry)
 469                 pr_warning("Could not create debugfs "
 470                            "'available_events' entry\n");
 471
 472         entry = debugfs_create_file("set_event", 0644, d_tracer,
 473                                     (void *)&show_set_event_seq_ops,
 474                                     &ftrace_set_event_fops);
 475         if (!entry)
 476                 pr_warning("Could not create debugfs "
 477                            "'set_event' entry\n");
 478
 479         d_events = event_trace_events_dir();
 480         if (!d_events)
 481                 return 0;
 482
 483         events_for_each(call) {
 484                 /* The linker may leave blanks */
 485                 if (!call->name)
 486                         continue;
 487                 event_create_dir(call, d_events);
 488         }
 489
 490         return 0;
 491 }
 492 fs_initcall(event_trace_init);