ltt-debugfs-abi.c

   1 /*
   2  * ltt-debugfs-abi.c
   3  *
   4  * Copyright 2010 (c) - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   5  *
   6  * LTTng debugfs ABI
   7  *
   8  * Mimic system calls for:
   9  * - session creation, returns a file descriptor or failure.
  10  *   - channel creation, returns a file descriptor or failure.
  11  *     - Operates on a session file descriptor
  12  *     - Takes all channel options as parameters.
  13  *   - stream get, returns a file descriptor or failure.
  14  *     - Operates on a channel file descriptor.
  15  *   - stream notifier get, returns a file descriptor or failure.
  16  *     - Operates on a channel file descriptor.
  17  *   - event creation, returns a file descriptor or failure.
  18  *     - Operates on a channel file descriptor
  19  *     - Takes an event name as parameter
  20  *     - Takes an instrumentation source as parameter
  21  *       - e.g. tracepoints, dynamic_probes...
  22  *     - Takes instrumentation source specific arguments.
  23  */
  24
  25 #include <linux/debugfs.h>
  26 #include "ltt-events.h"
  27
  28 /*
  29  * This is LTTng's own personal way to create a system call as an external
  30  * module. We use ioctl() on /sys/kernel/debug/lttng.
  31  */
  32
  33 static struct dentry *lttng_dentry;
  34 static const struct file_operations lttng_fops;
  35 static const struct file_operations lttng_session_fops;
  36 static const struct file_operations lttng_channel_fops;
  37 static const struct file_operations lttng_event_fops;
  38
  39 /*
  40  * LTTng DebugFS ABI structures.
  41  */
  42
  43 struct lttng_channel {
  44         int overwrite;                  /* 1: overwrite, 0: discard */
  45         u64 subbuf_size;
  46         u64 num_subbuf;
  47         unsigned int switch_timer_interval;
  48         unsigned int read_timer_interval;
  49 };
  50
  51 struct lttng_event {
  52         enum instrum_type itype;
  53         char name[];
  54 };
  55
  56 static
  57 int lttng_abi_create_session(void)
  58 {
  59         struct ltt_session *session;
  60         struct file *session_file;
  61         int session_fd;
  62
  63         session = ltt_session_create();
  64         if (!session)
  65                 return -ENOMEM;
  66         session_fd = get_unused_fd_flags(O_RDWR);
  67         if (session_fd < 0) {
  68                 ret = session_fd;
  69                 goto fd_error;
  70         }
  71         session_file = anon_inode_getfile("[lttng_session]",
  72                                           &lttng_session_fops,
  73                                           session, O_RDWR);
  74         if (IS_ERR(session_file)) {
  75                 ret = PTR_ERR(session_file);
  76                 goto file_error;
  77         }
  78         session->file = session_file;
  79         fd_install(session_fd, session_file);
  80         return session_fd;
  81
  82 file_error:
  83         put_unused_fd(session_fd);
  84 fd_error:
  85         ltt_session_destroy(session);
  86         return ret;
  87 }
  88
  89 /**
  90  *      lttng_ioctl - lttng syscall through ioctl
  91  *
  92  *      @file: the file
  93  *      @cmd: the command
  94  *      @arg: command arg
  95  *
  96  *      This ioctl implements lttng commands:
  97  *      LTTNG_SESSION
  98  *              Returns a LTTng trace session file descriptor
  99  *
 100  * The returned session will be deleted when its file descriptor is closed.
 101  */
 102 static
 103 long lttng_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 104 {
 105         switch (cmd) {
 106         case LTTNG_SESSION:
 107                 return lttng_abi_create_session();
 108         default:
 109                 return -ENOIOCTLCMD;
 110         }
 111 }
 112
 113 static const struct file_operations lttng_fops = {
 114         .unlocked_ioctl = lttng_ioctl,
 115 #ifdef CONFIG_COMPAT
 116         .compat_ioctl = lttng_ioctl,
 117 #endif
 118 }
 119
 120 int lttng_abi_create_channel(struct file *session_file,
 121                              struct lttng_channel __user *uchan_param)
 122 {
 123         struct ltt_session *session = session_file->private_data;
 124         struct ltt_channel *chan;
 125         struct file *chan_file;
 126         struct lttng_channel chan_param;
 127         int chan_fd;
 128         int ret = 0;
 129
 130         if (copy_from_user(&chan_param, uchan_param, sizeof(chan_param)))
 131                 return -EFAULT;
 132         chan_fd = get_unused_fd_flags(O_RDWR);
 133         if (chan_fd < 0) {
 134                 ret = chan_fd;
 135                 goto fd_error;
 136         }
 137         chan_file = anon_inode_getfile("[lttng_channel]",
 138                                        &lttng_channel_fops,
 139                                        NULL, O_RDWR);
 140         if (IS_ERR(chan_file)) {
 141                 ret = PTR_ERR(chan_file);
 142                 goto file_error;
 143         }
 144         /*
 145          * We tolerate no failure path after channel creation. It will stay
 146          * invariant for the rest of the session.
 147          */
 148         chan = ltt_channel_create(session, chan_param->overwrite, NULL,
 149                                   chan_param->subbuf_size,
 150                                   chan_param->num_subbuf,
 151                                   chan_param->switch_timer_interval,
 152                                   chan_param->read_timer_interval);
 153         if (!chan) {
 154                 ret = -ENOMEM;
 155                 goto chan_error;
 156         }
 157         channel->file = chan_file;
 158         chan_file->private_data = chan;
 159         fd_install(chan_fd, chan_file);
 160         /* The channel created holds a reference on the session */
 161         atomic_inc(&session_file->f_count);
 162
 163         return chan_fd;
 164
 165 chan_error:
 166         fput(chan_file);
 167 file_error:
 168         put_unused_fd(chan_fd);
 169 fd_error:
 170         return ret;
 171 }
 172
 173 /**
 174  *      lttng_session_ioctl - lttng session fd ioctl
 175  *
 176  *      @file: the file
 177  *      @cmd: the command
 178  *      @arg: command arg
 179  *
 180  *      This ioctl implements lttng commands:
 181  *      LTTNG_CHANNEL
 182  *              Returns a LTTng channel file descriptor
 183  *
 184  * The returned channel will be deleted when its file descriptor is closed.
 185  */
 186 static
 187 long lttng_session_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 188 {
 189         struct ltt_session *session = file->private_data;
 190
 191         switch (cmd) {
 192         case LTTNG_CHANNEL:
 193                 return lttng_abi_create_channel(file, (struct lttng_channel __user *)arg);
 194         case LTTNG_SESSION_START:
 195                 return ltt_session_start(session);
 196         case LTTNG_SESSION_STOP:
 197                 return ltt_session_stop(session);
 198         case LTTNG_SESSION_FINALIZE:
 199                 return ltt_session_finalize(session);
 200         default:
 201                 return -ENOIOCTLCMD;
 202         }
 203 }
 204
 205 /*
 206  * Called when the last file reference is dropped.
 207  *
 208  * Big fat note: channels and events are invariant for the whole session after
 209  * their creation. So this session destruction also destroys all channel and
 210  * event structures specific to this session (they are not destroyed when their
 211  * individual file is released).
 212  */
 213 static
 214 int lttng_session_release(struct inode *inode, struct file *file)
 215 {
 216         struct ltt_session *session = file->private_data;
 217         return ltt_session_destroy(session);
 218 }
 219
 220 static const struct file_operations lttng_session_fops = {
 221         .release = lttng_session_release,
 222         .unlocked_ioctl = lttng_session_ioctl,
 223 #ifdef CONFIG_COMPAT
 224         .compat_ioctl = lttng_session_ioctl,
 225 #endif
 226 }
 227
 228 static
 229 int lttng_abi_open_stream(struct file *channel_file)
 230 {
 231         struct ltt_channel *channel = channel_file->private_data;
 232         struct lib_ring_buffer *buf;
 233         int stream_fd, ret;
 234
 235         buf = ltt_buffer_read_open(channel->chan);
 236         if (!buf)
 237                 return -ENOENT;
 238
 239         stream_fd = get_unused_fd_flags(O_RDWR);
 240         if (stream_fd < 0) {
 241                 ret = stream_fd;
 242                 goto fd_error;
 243         }
 244         stream_file = anon_inode_getfile("[lttng_stream]",
 245                                          &lib_ring_buffer_file_operations,
 246                                          buf, O_RDWR);
 247         if (IS_ERR(stream_file)) {
 248                 ret = PTR_ERR(stream_file);
 249                 goto file_error;
 250         }
 251         fd_install(stream_fd, stream_file);
 252         /* The stream holds a reference on the channel */
 253         atomic_inc(&channel_file->f_count);
 254         return stream_fd;
 255
 256 file_error:
 257         put_unused_fd(stream_fd);
 258 fd_error:
 259         ltt_buffer_read_close(buf);
 260         return ret;
 261 }
 262
 263 static
 264 int lttng_abi_create_event(struct file *channel_file,
 265                            struct lttng_event __user *uevent_param)
 266 {
 267         struct ltt_channel *channel = channel_file->private_data;
 268         struct ltt_event *event;
 269         char *event_name;
 270         struct lttng_event event_param;
 271         int event_fd, ret;
 272
 273         if (copy_from_user(&event_param, uevent_param, sizeof(event_param)))
 274                 return -EFAULT;
 275         event_name = kmalloc(PATH_MAX, GFP_KERNEL);
 276         if (!event_name)
 277                 return -ENOMEM;
 278         if (strncpy_from_user(event_name, &uevent_param->name, PATH_MAX)) {
 279                 ret = -EFAULT;
 280                 goto name_error;
 281         }
 282         event_name[PATH_MAX - 1] = '\0';
 283         event_fd = get_unused_fd_flags(O_RDWR);
 284         if (event_fd < 0) {
 285                 ret = event_fd;
 286                 goto fd_error;
 287         }
 288         event_file = anon_inode_getfile("[lttng_event]",
 289                                         &lttng_event_fops, /* TODO: filter */
 290                                         NULL, O_RDWR);
 291         if (IS_ERR(event_file)) {
 292                 ret = PTR_ERR(event_file);
 293                 goto file_error;
 294         }
 295         /*
 296          * We tolerate no failure path after event creation. It will stay
 297          * invariant for the rest of the session.
 298          */
 299         event = ltt_event_create(channel, event_param->itype, event_name, NULL);
 300         if (!event) {
 301                 goto event_error;
 302                 ret = -EEXIST;
 303         }
 304         event_file->private_data = event;
 305         fd_install(event_fd, event_file);
 306         /* The event holds a reference on the channel */
 307         atomic_inc(&channel_file->f_count);
 308         kfree(event_name);
 309         return event_fd;
 310
 311 event_error:
 312         fput(event_file);
 313 file_error:
 314         put_unused_fd(event_fd);
 315 fd_error:
 316 name_error:
 317         kfree(event_name);
 318         return ret;
 319 }
 320
 321 /**
 322  *      lttng_channel_ioctl - lttng syscall through ioctl
 323  *
 324  *      @file: the file
 325  *      @cmd: the command
 326  *      @arg: command arg
 327  *
 328  *      This ioctl implements lttng commands:
 329  *      LTTNG_STREAM
 330  *              Returns an event stream file descriptor or failure.
 331  *              (typically, one event stream records events from one CPU)
 332  *      LTTNG_EVENT
 333  *              Returns an event file descriptor or failure.
 334  *
 335  * The returned session will be deleted when its file descriptor is closed.
 336  * Channel and event file descriptors also hold a reference on the session.
 337  */
 338 static
 339 long lttng_channel_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 340 {
 341         switch (cmd) {
 342         case LTTNG_STREAM:
 343                 return lttng_abi_open_stream(file);
 344         case LTTNG_EVENT:
 345                 return lttng_abi_create_event(file, (struct lttng_event __user *)arg);
 346         default:
 347                 return -ENOIOCTLCMD;
 348         }
 349 }
 350
 351 /**
 352  *      lttng_channel_poll - lttng stream addition/removal monitoring
 353  *
 354  *      @file: the file
 355  *      @wait: poll table
 356  */
 357 unsigned int lttng_channel_poll(struct file *file, poll_table *wait)
 358 {
 359         struct ltt_channel *channel = file->private_data;
 360         unsigned int mask = 0;
 361
 362         if (file->f_mode & FMODE_READ) {
 363                 poll_wait_set_exclusive(wait);
 364                 poll_wait(file, &channel->notify_wait, wait);
 365
 366                 /* TODO: identify when the channel is being finalized. */
 367                 if (finalized)
 368                         return POLLHUP;
 369                 else
 370                         return POLLIN | POLLRDNORM;
 371         }
 372         return mask;
 373
 374 }
 375
 376 static
 377 int lttng_channel_release(struct inode *inode, struct file *file)
 378 {
 379         struct ltt_channel *channel = file->private_data;
 380         fput(channel->session->file);
 381         return 0;
 382 }
 383
 384 static const struct file_operations lttng_channel_fops = {
 385         .release = lttng_channel_release,
 386         .poll = lttng_channel_poll,
 387         .unlocked_ioctl = lttng_channel_ioctl,
 388 #ifdef CONFIG_COMPAT
 389         .compat_ioctl = lttng_channel_ioctl,
 390 #endif
 391 }
 392
 393 static
 394 int lttng_event_release(struct inode *inode, struct file *file)
 395 {
 396         struct ltt_event *event = file->private_data;
 397         fput(event->chan->file);
 398         return 0;
 399 }
 400
 401 static const struct file_operations lttng_event_fops = {
 402         .release = lttng_event_release,
 403 }
 404
 405 static int __init ltt_debugfs_abi_init(void)
 406 {
 407         int ret = 0;
 408
 409         lttng_dentry = debugfs_create_file("lttng", NULL);
 410         if (IS_ERR(lttng_dentry) || !lttng_dentry)
 411                 printk(KERN_ERR "Error creating LTTng control file\n");
 412                 ret = -ENOMEM;
 413                 goto error;
 414         }
 415 error:
 416         return ret;
 417 }
 418
 419 static void __exit ltt_debugfs_abi_exit(void)
 420 {
 421         debugfs_remote(lttng_dentry);
 422 }