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/module.h>
  26 #include <linux/debugfs.h>
  27 #include <linux/anon_inodes.h>
  28 #include <linux/file.h>
  29 #include <linux/uaccess.h>
  30 #include <linux/slab.h>
  31 #include "wrapper/vmalloc.h"    /* for wrapper_vmalloc_sync_all() */
  32 #include "wrapper/ringbuffer/vfs.h"
  33 #include "ltt-debugfs-abi.h"
  34 #include "ltt-events.h"
  35
  36 /*
  37  * This is LTTng's own personal way to create a system call as an external
  38  * module. We use ioctl() on /sys/kernel/debug/lttng.
  39  */
  40
  41 static struct dentry *lttng_dentry;
  42 static const struct file_operations lttng_fops;
  43 static const struct file_operations lttng_session_fops;
  44 static const struct file_operations lttng_channel_fops;
  45 static const struct file_operations lttng_metadata_fops;
  46 static const struct file_operations lttng_event_fops;
  47
  48 enum channel_type {
  49         PER_CPU_CHANNEL,
  50         GLOBAL_CHANNEL,
  51         METADATA_CHANNEL,
  52 };
  53
  54 static
  55 int lttng_abi_create_session(void)
  56 {
  57         struct ltt_session *session;
  58         struct file *session_file;
  59         int session_fd, ret;
  60
  61         session = ltt_session_create();
  62         if (!session)
  63                 return -ENOMEM;
  64         session_fd = get_unused_fd();
  65         if (session_fd < 0) {
  66                 ret = session_fd;
  67                 goto fd_error;
  68         }
  69         session_file = anon_inode_getfile("[lttng_session]",
  70                                           &lttng_session_fops,
  71                                           session, O_RDWR);
  72         if (IS_ERR(session_file)) {
  73                 ret = PTR_ERR(session_file);
  74                 goto file_error;
  75         }
  76         session->file = session_file;
  77         fd_install(session_fd, session_file);
  78         return session_fd;
  79
  80 file_error:
  81         put_unused_fd(session_fd);
  82 fd_error:
  83         ltt_session_destroy(session);
  84         return ret;
  85 }
  86
  87 /**
  88  *      lttng_ioctl - lttng syscall through ioctl
  89  *
  90  *      @file: the file
  91  *      @cmd: the command
  92  *      @arg: command arg
  93  *
  94  *      This ioctl implements lttng commands:
  95  *      LTTNG_SESSION
  96  *              Returns a LTTng trace session file descriptor
  97  *
  98  * The returned session will be deleted when its file descriptor is closed.
  99  */
 100 static
 101 long lttng_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 102 {
 103         switch (cmd) {
 104         case LTTNG_SESSION:
 105                 return lttng_abi_create_session();
 106         default:
 107                 return -ENOIOCTLCMD;
 108         }
 109 }
 110
 111 static const struct file_operations lttng_fops = {
 112         .unlocked_ioctl = lttng_ioctl,
 113 #ifdef CONFIG_COMPAT
 114         .compat_ioctl = lttng_ioctl,
 115 #endif
 116 };
 117
 118 /*
 119  * We tolerate no failure in this function (if one happens, we print a dmesg
 120  * error, but cannot return any error, because the channel information is
 121  * invariant.
 122  */
 123 static
 124 void lttng_metadata_create_events(struct file *channel_file)
 125 {
 126         struct ltt_channel *channel = channel_file->private_data;
 127         char *event_name = "lttng-metadata";
 128         struct ltt_event *event;
 129         int ret;
 130         void *probe;
 131
 132         probe = ltt_probe_get(event_name);
 133         if (!probe) {
 134                 ret = -ENOENT;
 135                 goto probe_error;
 136         }
 137         /*
 138          * We tolerate no failure path after event creation. It will stay
 139          * invariant for the rest of the session.
 140          */
 141         event = ltt_event_create(channel, event_name, INSTRUM_TRACEPOINTS,
 142                                  probe, NULL);
 143         if (!event) {
 144                 goto event_error;
 145                 ret = -EEXIST;
 146         }
 147         return;
 148
 149 event_error:
 150         ltt_probe_put(probe);
 151 probe_error:
 152         WARN_ON(1);
 153         return;         /* not allowed to return error */
 154 }
 155
 156 static
 157 int lttng_abi_create_channel(struct file *session_file,
 158                              struct lttng_channel __user *uchan_param,
 159                              enum channel_type channel_type)
 160 {
 161         struct ltt_session *session = session_file->private_data;
 162         const struct file_operations *fops;
 163         const char *transport_name;
 164         struct ltt_channel *chan;
 165         struct file *chan_file;
 166         struct lttng_channel chan_param;
 167         int chan_fd;
 168         int ret = 0;
 169
 170         if (copy_from_user(&chan_param, uchan_param, sizeof(chan_param)))
 171                 return -EFAULT;
 172         chan_fd = get_unused_fd();
 173         if (chan_fd < 0) {
 174                 ret = chan_fd;
 175                 goto fd_error;
 176         }
 177         chan_file = anon_inode_getfile("[lttng_channel]",
 178                                        &lttng_channel_fops,
 179                                        NULL, O_RDWR);
 180         if (IS_ERR(chan_file)) {
 181                 ret = PTR_ERR(chan_file);
 182                 goto file_error;
 183         }
 184         switch (channel_type) {
 185         case PER_CPU_CHANNEL:
 186                 transport_name = chan_param.overwrite ?
 187                         "relay-overwrite" : "relay-discard";
 188                 fops = &lttng_channel_fops;
 189                 break;
 190         case GLOBAL_CHANNEL:
 191                 transport_name = chan_param.overwrite ?
 192                         "global-relay-overwrite" : "global-relay-discard";
 193                 fops = &lttng_channel_fops;
 194                 break;
 195         case METADATA_CHANNEL:
 196                 transport_name = "global-relay-discard";
 197                 fops = &lttng_metadata_fops;
 198                 break;
 199         default:
 200                 transport_name = "<unknown>";
 201                 break;
 202         }
 203         /*
 204          * We tolerate no failure path after channel creation. It will stay
 205          * invariant for the rest of the session.
 206          */
 207         chan = ltt_channel_create(session, transport_name, NULL,
 208                                   chan_param.subbuf_size,
 209                                   chan_param.num_subbuf,
 210                                   chan_param.switch_timer_interval,
 211                                   chan_param.read_timer_interval);
 212         if (!chan) {
 213                 ret = -EINVAL;
 214                 goto chan_error;
 215         }
 216         chan->file = chan_file;
 217         chan_file->private_data = chan;
 218         fd_install(chan_fd, chan_file);
 219         if (channel_type == METADATA_CHANNEL)
 220                 lttng_metadata_create_events(chan_file);
 221
 222         /* The channel created holds a reference on the session */
 223         atomic_long_inc(&session_file->f_count);
 224
 225         return chan_fd;
 226
 227 chan_error:
 228         fput(chan_file);
 229 file_error:
 230         put_unused_fd(chan_fd);
 231 fd_error:
 232         return ret;
 233 }
 234
 235 /**
 236  *      lttng_session_ioctl - lttng session fd ioctl
 237  *
 238  *      @file: the file
 239  *      @cmd: the command
 240  *      @arg: command arg
 241  *
 242  *      This ioctl implements lttng commands:
 243  *      LTTNG_CHANNEL
 244  *              Returns a LTTng channel file descriptor
 245  *
 246  * The returned channel will be deleted when its file descriptor is closed.
 247  */
 248 static
 249 long lttng_session_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 250 {
 251         struct ltt_session *session = file->private_data;
 252
 253         switch (cmd) {
 254         case LTTNG_CHANNEL:
 255                 return lttng_abi_create_channel(file,
 256                                 (struct lttng_channel __user *)arg,
 257                                 PER_CPU_CHANNEL);
 258         case LTTNG_SESSION_START:
 259                 return ltt_session_start(session);
 260         case LTTNG_SESSION_STOP:
 261                 return ltt_session_stop(session);
 262         case LTTNG_METADATA:
 263                 return lttng_abi_create_channel(file,
 264                                 (struct lttng_channel __user *)arg,
 265                                 METADATA_CHANNEL);
 266         default:
 267                 return -ENOIOCTLCMD;
 268         }
 269 }
 270
 271 /*
 272  * Called when the last file reference is dropped.
 273  *
 274  * Big fat note: channels and events are invariant for the whole session after
 275  * their creation. So this session destruction also destroys all channel and
 276  * event structures specific to this session (they are not destroyed when their
 277  * individual file is released).
 278  */
 279 static
 280 int lttng_session_release(struct inode *inode, struct file *file)
 281 {
 282         struct ltt_session *session = file->private_data;
 283
 284         if (session)
 285                 ltt_session_destroy(session);
 286         return 0;
 287 }
 288
 289 static const struct file_operations lttng_session_fops = {
 290         .release = lttng_session_release,
 291         .unlocked_ioctl = lttng_session_ioctl,
 292 #ifdef CONFIG_COMPAT
 293         .compat_ioctl = lttng_session_ioctl,
 294 #endif
 295 };
 296
 297 static
 298 int lttng_abi_open_stream(struct file *channel_file)
 299 {
 300         struct ltt_channel *channel = channel_file->private_data;
 301         struct lib_ring_buffer *buf;
 302         int stream_fd, ret;
 303         struct file *stream_file;
 304
 305         buf = channel->ops->buffer_read_open(channel->chan);
 306         if (!buf)
 307                 return -ENOENT;
 308
 309         stream_fd = get_unused_fd();
 310         if (stream_fd < 0) {
 311                 ret = stream_fd;
 312                 goto fd_error;
 313         }
 314         stream_file = anon_inode_getfile("[lttng_stream]",
 315                                          &lib_ring_buffer_file_operations,
 316                                          buf, O_RDWR);
 317         if (IS_ERR(stream_file)) {
 318                 ret = PTR_ERR(stream_file);
 319                 goto file_error;
 320         }
 321         /*
 322          * OPEN_FMODE, called within anon_inode_getfile/alloc_file, don't honor
 323          * FMODE_LSEEK, FMODE_PREAD nor FMODE_PWRITE. We need to read from this
 324          * file descriptor, so we set FMODE_PREAD here.
 325          */
 326         stream_file->f_mode |= FMODE_PREAD;
 327         fd_install(stream_fd, stream_file);
 328         /*
 329          * The stream holds a reference to the channel within the generic ring
 330          * buffer library, so no need to hold a refcount on the channel and
 331          * session files here.
 332          */
 333         return stream_fd;
 334
 335 file_error:
 336         put_unused_fd(stream_fd);
 337 fd_error:
 338         channel->ops->buffer_read_close(buf);
 339         return ret;
 340 }
 341
 342 static
 343 int lttng_abi_create_event(struct file *channel_file,
 344                            struct lttng_event __user *uevent_param)
 345 {
 346         struct ltt_channel *channel = channel_file->private_data;
 347         struct ltt_event *event;
 348         char *event_name;
 349         struct lttng_event event_param;
 350         int event_fd, ret;
 351         struct file *event_file;
 352         void *probe;
 353
 354         if (copy_from_user(&event_param, uevent_param, sizeof(event_param)))
 355                 return -EFAULT;
 356         event_name = kmalloc(PATH_MAX, GFP_KERNEL);
 357         if (!event_name)
 358                 return -ENOMEM;
 359         if (strncpy_from_user(event_name, uevent_param->name, PATH_MAX) < 0) {
 360                 ret = -EFAULT;
 361                 goto name_error;
 362         }
 363         event_name[PATH_MAX - 1] = '\0';
 364
 365         probe = ltt_probe_get(event_name);
 366         if (!probe) {
 367                 ret = -ENOENT;
 368                 goto probe_error;
 369         }
 370         event_fd = get_unused_fd();
 371         if (event_fd < 0) {
 372                 ret = event_fd;
 373                 goto fd_error;
 374         }
 375         event_file = anon_inode_getfile("[lttng_event]",
 376                                         &lttng_event_fops,
 377                                         NULL, O_RDWR);
 378         if (IS_ERR(event_file)) {
 379                 ret = PTR_ERR(event_file);
 380                 goto file_error;
 381         }
 382         /*
 383          * We tolerate no failure path after event creation. It will stay
 384          * invariant for the rest of the session.
 385          */
 386         event = ltt_event_create(channel, event_name, event_param.itype,
 387                                  probe, NULL);
 388         if (!event) {
 389                 goto event_error;
 390                 ret = -EEXIST;
 391         }
 392         event_file->private_data = event;
 393         fd_install(event_fd, event_file);
 394         /* The event holds a reference on the channel */
 395         atomic_long_inc(&channel_file->f_count);
 396         kfree(event_name);
 397         return event_fd;
 398
 399 event_error:
 400         fput(event_file);
 401 file_error:
 402         put_unused_fd(event_fd);
 403 fd_error:
 404         ltt_probe_put(probe);
 405 probe_error:
 406 name_error:
 407         kfree(event_name);
 408         return ret;
 409 }
 410
 411 /**
 412  *      lttng_channel_ioctl - lttng syscall through ioctl
 413  *
 414  *      @file: the file
 415  *      @cmd: the command
 416  *      @arg: command arg
 417  *
 418  *      This ioctl implements lttng commands:
 419  *      LTTNG_STREAM
 420  *              Returns an event stream file descriptor or failure.
 421  *              (typically, one event stream records events from one CPU)
 422  *      LTTNG_EVENT
 423  *              Returns an event file descriptor or failure.
 424  *
 425  * Channel and event file descriptors also hold a reference on the session.
 426  */
 427 static
 428 long lttng_channel_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 429 {
 430         switch (cmd) {
 431         case LTTNG_STREAM:
 432                 return lttng_abi_open_stream(file);
 433         case LTTNG_EVENT:
 434                 return lttng_abi_create_event(file, (struct lttng_event __user *)arg);
 435         default:
 436                 return -ENOIOCTLCMD;
 437         }
 438 }
 439
 440 /**
 441  *      lttng_metadata_ioctl - lttng syscall through ioctl
 442  *
 443  *      @file: the file
 444  *      @cmd: the command
 445  *      @arg: command arg
 446  *
 447  *      This ioctl implements lttng commands:
 448  *      LTTNG_STREAM
 449  *              Returns an event stream file descriptor or failure.
 450  *
 451  * Channel and event file descriptors also hold a reference on the session.
 452  */
 453 static
 454 long lttng_metadata_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 455 {
 456         switch (cmd) {
 457         case LTTNG_STREAM:
 458                 return lttng_abi_open_stream(file);
 459         default:
 460                 return -ENOIOCTLCMD;
 461         }
 462 }
 463
 464 /* TODO: poll */
 465 #if 0
 466 /**
 467  *      lttng_channel_poll - lttng stream addition/removal monitoring
 468  *
 469  *      @file: the file
 470  *      @wait: poll table
 471  */
 472 unsigned int lttng_channel_poll(struct file *file, poll_table *wait)
 473 {
 474         struct ltt_channel *channel = file->private_data;
 475         unsigned int mask = 0;
 476
 477         if (file->f_mode & FMODE_READ) {
 478                 poll_wait_set_exclusive(wait);
 479                 poll_wait(file, &channel->notify_wait, wait);
 480
 481                 /* TODO: identify when the channel is being finalized. */
 482                 if (finalized)
 483                         return POLLHUP;
 484                 else
 485                         return POLLIN | POLLRDNORM;
 486         }
 487         return mask;
 488
 489 }
 490 #endif //0
 491
 492 static
 493 int lttng_channel_release(struct inode *inode, struct file *file)
 494 {
 495         struct ltt_channel *channel = file->private_data;
 496
 497         if (channel)
 498                 fput(channel->session->file);
 499         return 0;
 500 }
 501
 502 static const struct file_operations lttng_channel_fops = {
 503         .release = lttng_channel_release,
 504 /* TODO */
 505 #if 0
 506         .poll = lttng_channel_poll,
 507 #endif //0
 508         .unlocked_ioctl = lttng_channel_ioctl,
 509 #ifdef CONFIG_COMPAT
 510         .compat_ioctl = lttng_channel_ioctl,
 511 #endif
 512 };
 513
 514 static const struct file_operations lttng_metadata_fops = {
 515         .release = lttng_channel_release,
 516         .unlocked_ioctl = lttng_metadata_ioctl,
 517 #ifdef CONFIG_COMPAT
 518         .compat_ioctl = lttng_metadata_ioctl,
 519 #endif
 520 };
 521
 522 static
 523 int lttng_event_release(struct inode *inode, struct file *file)
 524 {
 525         struct ltt_event *event = file->private_data;
 526
 527         if (event)
 528                 fput(event->chan->file);
 529         return 0;
 530 }
 531
 532 /* TODO: filter control ioctl */
 533 static const struct file_operations lttng_event_fops = {
 534         .release = lttng_event_release,
 535 };
 536
 537 int __init ltt_debugfs_abi_init(void)
 538 {
 539         int ret = 0;
 540
 541         wrapper_vmalloc_sync_all();
 542         lttng_dentry = debugfs_create_file("lttng", S_IWUSR, NULL, NULL,
 543                                            &lttng_fops);
 544         if (IS_ERR(lttng_dentry) || !lttng_dentry) {
 545                 printk(KERN_ERR "Error creating LTTng control file\n");
 546                 ret = -ENOMEM;
 547                 goto error;
 548         }
 549 error:
 550         return ret;
 551 }
 552
 553 void __exit ltt_debugfs_abi_exit(void)
 554 {
 555         debugfs_remove(lttng_dentry);
 556 }