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_events.h"
  14
  15 #define events_for_each(event)                                          \
  16         for (event = __start_ftrace_events;                             \
  17              (unsigned long)event < (unsigned long)__stop_ftrace_events; \
  18              event++)
  19
  20 void event_trace_printk(unsigned long ip, const char *fmt, ...)
  21 {
  22         va_list ap;
  23
  24         va_start(ap, fmt);
  25         tracing_record_cmdline(current);
  26         trace_vprintk(ip, task_curr_ret_stack(current), fmt, ap);
  27         va_end(ap);
  28 }
  29
  30 static void ftrace_clear_events(void)
  31 {
  32         struct ftrace_event_call *call = (void *)__start_ftrace_events;
  33
  34
  35         while ((unsigned long)call < (unsigned long)__stop_ftrace_events) {
  36
  37                 if (call->enabled) {
  38                         call->enabled = 0;
  39                         call->unregfunc();
  40                 }
  41                 call++;
  42         }
  43 }
  44
  45 static int ftrace_set_clr_event(char *buf, int set)
  46 {
  47         struct ftrace_event_call *call = __start_ftrace_events;
  48
  49
  50         events_for_each(call) {
  51
  52                 if (!call->name)
  53                         continue;
  54
  55                 if (strcmp(buf, call->name) != 0)
  56                         continue;
  57
  58                 if (set) {
  59                         /* Already set? */
  60                         if (call->enabled)
  61                                 return 0;
  62                         call->enabled = 1;
  63                         call->regfunc();
  64                 } else {
  65                         /* Already cleared? */
  66                         if (!call->enabled)
  67                                 return 0;
  68                         call->enabled = 0;
  69                         call->unregfunc();
  70                 }
  71                 return 0;
  72         }
  73         return -EINVAL;
  74 }
  75
  76 /* 128 should be much more than enough */
  77 #define EVENT_BUF_SIZE          127
  78
  79 static ssize_t
  80 ftrace_event_write(struct file *file, const char __user *ubuf,
  81                    size_t cnt, loff_t *ppos)
  82 {
  83         size_t read = 0;
  84         int i, set = 1;
  85         ssize_t ret;
  86         char *buf;
  87         char ch;
  88
  89         if (!cnt || cnt < 0)
  90                 return 0;
  91
  92         ret = get_user(ch, ubuf++);
  93         if (ret)
  94                 return ret;
  95         read++;
  96         cnt--;
  97
  98         /* skip white space */
  99         while (cnt && isspace(ch)) {
 100                 ret = get_user(ch, ubuf++);
 101                 if (ret)
 102                         return ret;
 103                 read++;
 104                 cnt--;
 105         }
 106
 107         /* Only white space found? */
 108         if (isspace(ch)) {
 109                 file->f_pos += read;
 110                 ret = read;
 111                 return ret;
 112         }
 113
 114         buf = kmalloc(EVENT_BUF_SIZE+1, GFP_KERNEL);
 115         if (!buf)
 116                 return -ENOMEM;
 117
 118         if (cnt > EVENT_BUF_SIZE)
 119                 cnt = EVENT_BUF_SIZE;
 120
 121         i = 0;
 122         while (cnt && !isspace(ch)) {
 123                 if (!i && ch == '!')
 124                         set = 0;
 125                 else
 126                         buf[i++] = ch;
 127
 128                 ret = get_user(ch, ubuf++);
 129                 if (ret)
 130                         goto out_free;
 131                 read++;
 132                 cnt--;
 133         }
 134         buf[i] = 0;
 135
 136         file->f_pos += read;
 137
 138         ret = ftrace_set_clr_event(buf, set);
 139         if (ret)
 140                 goto out_free;
 141
 142         ret = read;
 143
 144  out_free:
 145         kfree(buf);
 146
 147         return ret;
 148 }
 149
 150 static void *
 151 t_next(struct seq_file *m, void *v, loff_t *pos)
 152 {
 153         struct ftrace_event_call *call = m->private;
 154         struct ftrace_event_call *next = call;
 155
 156         (*pos)++;
 157
 158         if ((unsigned long)call >= (unsigned long)__stop_ftrace_events)
 159                 return NULL;
 160
 161         m->private = ++next;
 162
 163         return call;
 164 }
 165
 166 static void *t_start(struct seq_file *m, loff_t *pos)
 167 {
 168         return t_next(m, NULL, pos);
 169 }
 170
 171 static void *
 172 s_next(struct seq_file *m, void *v, loff_t *pos)
 173 {
 174         struct ftrace_event_call *call = m->private;
 175         struct ftrace_event_call *next;
 176
 177         (*pos)++;
 178
 179  retry:
 180         if ((unsigned long)call >= (unsigned long)__stop_ftrace_events)
 181                 return NULL;
 182
 183         if (!call->enabled) {
 184                 call++;
 185                 goto retry;
 186         }
 187
 188         next = call;
 189         m->private = ++next;
 190
 191         return call;
 192 }
 193
 194 static void *s_start(struct seq_file *m, loff_t *pos)
 195 {
 196         return s_next(m, NULL, pos);
 197 }
 198
 199 static int t_show(struct seq_file *m, void *v)
 200 {
 201         struct ftrace_event_call *call = v;
 202
 203         seq_printf(m, "%s\n", call->name);
 204
 205         return 0;
 206 }
 207
 208 static void t_stop(struct seq_file *m, void *p)
 209 {
 210 }
 211
 212 static int
 213 ftrace_event_seq_open(struct inode *inode, struct file *file)
 214 {
 215         int ret;
 216         const struct seq_operations *seq_ops;
 217
 218         if ((file->f_mode & FMODE_WRITE) &&
 219             !(file->f_flags & O_APPEND))
 220                 ftrace_clear_events();
 221
 222         seq_ops = inode->i_private;
 223         ret = seq_open(file, seq_ops);
 224         if (!ret) {
 225                 struct seq_file *m = file->private_data;
 226
 227                 m->private = __start_ftrace_events;
 228         }
 229         return ret;
 230 }
 231
 232 static ssize_t
 233 event_enable_read(struct file *filp, char __user *ubuf, size_t cnt,
 234                   loff_t *ppos)
 235 {
 236         struct ftrace_event_call *call = filp->private_data;
 237         char *buf;
 238
 239         if (call->enabled)
 240                 buf = "1\n";
 241         else
 242                 buf = "0\n";
 243
 244         return simple_read_from_buffer(ubuf, cnt, ppos, buf, 2);
 245 }
 246
 247 static ssize_t
 248 event_enable_write(struct file *filp, const char __user *ubuf, size_t cnt,
 249                    loff_t *ppos)
 250 {
 251         struct ftrace_event_call *call = filp->private_data;
 252         char buf[64];
 253         unsigned long val;
 254         int ret;
 255
 256         if (cnt >= sizeof(buf))
 257                 return -EINVAL;
 258
 259         if (copy_from_user(&buf, ubuf, cnt))
 260                 return -EFAULT;
 261
 262         buf[cnt] = 0;
 263
 264         ret = strict_strtoul(buf, 10, &val);
 265         if (ret < 0)
 266                 return ret;
 267
 268         switch (val) {
 269         case 0:
 270                 if (!call->enabled)
 271                         break;
 272
 273                 call->enabled = 0;
 274                 call->unregfunc();
 275                 break;
 276         case 1:
 277                 if (call->enabled)
 278                         break;
 279
 280                 call->enabled = 1;
 281                 call->regfunc();
 282                 break;
 283
 284         default:
 285                 return -EINVAL;
 286         }
 287
 288         *ppos += cnt;
 289
 290         return cnt;
 291 }
 292
 293 static const struct seq_operations show_event_seq_ops = {
 294         .start = t_start,
 295         .next = t_next,
 296         .show = t_show,
 297         .stop = t_stop,
 298 };
 299
 300 static const struct seq_operations show_set_event_seq_ops = {
 301         .start = s_start,
 302         .next = s_next,
 303         .show = t_show,
 304         .stop = t_stop,
 305 };
 306
 307 static const struct file_operations ftrace_avail_fops = {
 308         .open = ftrace_event_seq_open,
 309         .read = seq_read,
 310         .llseek = seq_lseek,
 311         .release = seq_release,
 312 };
 313
 314 static const struct file_operations ftrace_set_event_fops = {
 315         .open = ftrace_event_seq_open,
 316         .read = seq_read,
 317         .write = ftrace_event_write,
 318         .llseek = seq_lseek,
 319         .release = seq_release,
 320 };
 321
 322 static const struct file_operations ftrace_enable_fops = {
 323         .open = tracing_open_generic,
 324         .read = event_enable_read,
 325         .write = event_enable_write,
 326 };
 327
 328 static struct dentry *event_trace_events_dir(void)
 329 {
 330         static struct dentry *d_tracer;
 331         static struct dentry *d_events;
 332
 333         if (d_events)
 334                 return d_events;
 335
 336         d_tracer = tracing_init_dentry();
 337         if (!d_tracer)
 338                 return NULL;
 339
 340         d_events = debugfs_create_dir("events", d_tracer);
 341         if (!d_events)
 342                 pr_warning("Could not create debugfs "
 343                            "'events' directory\n");
 344
 345         return d_events;
 346 }
 347
 348 static int
 349 event_create_dir(struct ftrace_event_call *call, struct dentry *d_events)
 350 {
 351         struct dentry *entry;
 352
 353         call->dir = debugfs_create_dir(call->name, d_events);
 354         if (!call->dir) {
 355                 pr_warning("Could not create debugfs "
 356                            "'%s' directory\n", call->name);
 357                 return -1;
 358         }
 359
 360         entry = debugfs_create_file("enable", 0644, call->dir, call,
 361                                     &ftrace_enable_fops);
 362         if (!entry)
 363                 pr_warning("Could not create debugfs "
 364                            "'%s/enable' entry\n", call->name);
 365
 366         return 0;
 367 }
 368
 369 static __init int event_trace_init(void)
 370 {
 371         struct ftrace_event_call *call = __start_ftrace_events;
 372         struct dentry *d_tracer;
 373         struct dentry *entry;
 374         struct dentry *d_events;
 375
 376         d_tracer = tracing_init_dentry();
 377         if (!d_tracer)
 378                 return 0;
 379
 380         entry = debugfs_create_file("available_events", 0444, d_tracer,
 381                                     (void *)&show_event_seq_ops,
 382                                     &ftrace_avail_fops);
 383         if (!entry)
 384                 pr_warning("Could not create debugfs "
 385                            "'available_events' entry\n");
 386
 387         entry = debugfs_create_file("set_event", 0644, d_tracer,
 388                                     (void *)&show_set_event_seq_ops,
 389                                     &ftrace_set_event_fops);
 390         if (!entry)
 391                 pr_warning("Could not create debugfs "
 392                            "'set_event' entry\n");
 393
 394         d_events = event_trace_events_dir();
 395         if (!d_events)
 396                 return 0;
 397
 398         events_for_each(call) {
 399                 /* The linker may leave blanks */
 400                 if (!call->name)
 401                         continue;
 402                 event_create_dir(call, d_events);
 403         }
 404
 405         return 0;
 406 }
 407 fs_initcall(event_trace_init);