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  * Dual LGPL v2.1/GPL v2 license.
  25  */
  26
  27 #include <linux/module.h>
  28 #include <linux/debugfs.h>
  29 #include <linux/anon_inodes.h>
  30 #include <linux/file.h>
  31 #include <linux/uaccess.h>
  32 #include <linux/slab.h>
  33 #include "wrapper/vmalloc.h"    /* for wrapper_vmalloc_sync_all() */
  34 #include "wrapper/ringbuffer/vfs.h"
  35 #include "wrapper/poll.h"
  36 #include "ltt-debugfs-abi.h"
  37 #include "ltt-events.h"
  38 #include "ltt-tracer.h"
  39
  40 /*
  41  * This is LTTng's own personal way to create a system call as an external
  42  * module. We use ioctl() on /sys/kernel/debug/lttng.
  43  */
  44
  45 static struct dentry *lttng_dentry;
  46 static const struct file_operations lttng_fops;
  47 static const struct file_operations lttng_session_fops;
  48 static const struct file_operations lttng_channel_fops;
  49 static const struct file_operations lttng_metadata_fops;
  50 static const struct file_operations lttng_event_fops;
  51
  52 enum channel_type {
  53         PER_CPU_CHANNEL,
  54         METADATA_CHANNEL,
  55 };
  56
  57 static
  58 int lttng_abi_create_session(void)
  59 {
  60         struct ltt_session *session;
  61         struct file *session_file;
  62         int session_fd, ret;
  63
  64         session = ltt_session_create();
  65         if (!session)
  66                 return -ENOMEM;
  67         session_fd = get_unused_fd();
  68         if (session_fd < 0) {
  69                 ret = session_fd;
  70                 goto fd_error;
  71         }
  72         session_file = anon_inode_getfile("[lttng_session]",
  73                                           &lttng_session_fops,
  74                                           session, O_RDWR);
  75         if (IS_ERR(session_file)) {
  76                 ret = PTR_ERR(session_file);
  77                 goto file_error;
  78         }
  79         session->file = session_file;
  80         fd_install(session_fd, session_file);
  81         return session_fd;
  82
  83 file_error:
  84         put_unused_fd(session_fd);
  85 fd_error:
  86         ltt_session_destroy(session);
  87         return ret;
  88 }
  89
  90 static
  91 int lttng_abi_tracepoint_list(void)
  92 {
  93         struct file *tracepoint_list_file;
  94         int file_fd, ret;
  95
  96         file_fd = get_unused_fd();
  97         if (file_fd < 0) {
  98                 ret = file_fd;
  99                 goto fd_error;
 100         }
 101
 102         tracepoint_list_file = anon_inode_getfile("[lttng_session]",
 103                                           &lttng_tracepoint_list_fops,
 104                                           NULL, O_RDWR);
 105         if (IS_ERR(tracepoint_list_file)) {
 106                 ret = PTR_ERR(tracepoint_list_file);
 107                 goto file_error;
 108         }
 109         ret = lttng_tracepoint_list_fops.open(NULL, tracepoint_list_file);
 110         if (ret < 0)
 111                 goto open_error;
 112         fd_install(file_fd, tracepoint_list_file);
 113         if (file_fd < 0) {
 114                 ret = file_fd;
 115                 goto fd_error;
 116         }
 117         return file_fd;
 118
 119 open_error:
 120         fput(tracepoint_list_file);
 121 file_error:
 122         put_unused_fd(file_fd);
 123 fd_error:
 124         return ret;
 125 }
 126
 127 static
 128 long lttng_abi_tracer_version(struct file *file,
 129         struct lttng_kernel_tracer_version __user *uversion_param)
 130 {
 131         struct lttng_kernel_tracer_version v;
 132
 133         v.version = LTTNG_VERSION;
 134         v.patchlevel = LTTNG_PATCHLEVEL;
 135         v.sublevel = LTTNG_SUBLEVEL;
 136
 137         if (copy_to_user(uversion_param, &v, sizeof(v)))
 138                 return -EFAULT;
 139         return 0;
 140 }
 141
 142 static
 143 long lttng_abi_add_context(struct file *file,
 144         struct lttng_kernel_context __user *ucontext_param,
 145         struct lttng_ctx **ctx, struct ltt_session *session)
 146 {
 147         struct lttng_kernel_context context_param;
 148
 149         if (session->been_active)
 150                 return -EPERM;
 151
 152         if (copy_from_user(&context_param, ucontext_param, sizeof(context_param)))
 153                 return -EFAULT;
 154
 155         switch (context_param.ctx) {
 156         case LTTNG_KERNEL_CONTEXT_PID:
 157                 return lttng_add_pid_to_ctx(ctx);
 158         case LTTNG_KERNEL_CONTEXT_PRIO:
 159                 return lttng_add_prio_to_ctx(ctx);
 160         case LTTNG_KERNEL_CONTEXT_NICE:
 161                 return lttng_add_nice_to_ctx(ctx);
 162         case LTTNG_KERNEL_CONTEXT_VPID:
 163                 return lttng_add_vpid_to_ctx(ctx);
 164         case LTTNG_KERNEL_CONTEXT_TID:
 165                 return lttng_add_tid_to_ctx(ctx);
 166         case LTTNG_KERNEL_CONTEXT_VTID:
 167                 return lttng_add_vtid_to_ctx(ctx);
 168         case LTTNG_KERNEL_CONTEXT_PPID:
 169                 return lttng_add_ppid_to_ctx(ctx);
 170         case LTTNG_KERNEL_CONTEXT_VPPID:
 171                 return lttng_add_vppid_to_ctx(ctx);
 172         case LTTNG_KERNEL_CONTEXT_PERF_COUNTER:
 173                 context_param.u.perf_counter.name[LTTNG_SYM_NAME_LEN - 1] = '\0';
 174                 return lttng_add_perf_counter_to_ctx(context_param.u.perf_counter.type,
 175                                 context_param.u.perf_counter.config,
 176                                 context_param.u.perf_counter.name,
 177                                 ctx);
 178         case LTTNG_KERNEL_CONTEXT_COMM:
 179                 return lttng_add_comm_to_ctx(ctx);
 180         default:
 181                 return -EINVAL;
 182         }
 183 }
 184
 185 /**
 186  *      lttng_ioctl - lttng syscall through ioctl
 187  *
 188  *      @file: the file
 189  *      @cmd: the command
 190  *      @arg: command arg
 191  *
 192  *      This ioctl implements lttng commands:
 193  *      LTTNG_KERNEL_SESSION
 194  *              Returns a LTTng trace session file descriptor
 195  *      LTTNG_KERNEL_TRACER_VERSION
 196  *              Returns the LTTng kernel tracer version
 197  *      LTTNG_KERNEL_TRACEPOINT_LIST
 198  *              Returns a file descriptor listing available tracepoints
 199  *      LTTNG_KERNEL_WAIT_QUIESCENT
 200  *              Returns after all previously running probes have completed
 201  *
 202  * The returned session will be deleted when its file descriptor is closed.
 203  */
 204 static
 205 long lttng_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 206 {
 207         switch (cmd) {
 208         case LTTNG_KERNEL_SESSION:
 209                 return lttng_abi_create_session();
 210         case LTTNG_KERNEL_TRACER_VERSION:
 211                 return lttng_abi_tracer_version(file,
 212                                 (struct lttng_kernel_tracer_version __user *) arg);
 213         case LTTNG_KERNEL_TRACEPOINT_LIST:
 214                 return lttng_abi_tracepoint_list();
 215         case LTTNG_KERNEL_WAIT_QUIESCENT:
 216                 synchronize_trace();
 217                 return 0;
 218         default:
 219                 return -ENOIOCTLCMD;
 220         }
 221 }
 222
 223 static const struct file_operations lttng_fops = {
 224         .unlocked_ioctl = lttng_ioctl,
 225 #ifdef CONFIG_COMPAT
 226         .compat_ioctl = lttng_ioctl,
 227 #endif
 228 };
 229
 230 /*
 231  * We tolerate no failure in this function (if one happens, we print a dmesg
 232  * error, but cannot return any error, because the channel information is
 233  * invariant.
 234  */
 235 static
 236 void lttng_metadata_create_events(struct file *channel_file)
 237 {
 238         struct ltt_channel *channel = channel_file->private_data;
 239         static struct lttng_kernel_event metadata_params = {
 240                 .instrumentation = LTTNG_KERNEL_TRACEPOINT,
 241                 .name = "lttng_metadata",
 242         };
 243         struct ltt_event *event;
 244         int ret;
 245
 246         /*
 247          * We tolerate no failure path after event creation. It will stay
 248          * invariant for the rest of the session.
 249          */
 250         event = ltt_event_create(channel, &metadata_params, NULL);
 251         if (!event) {
 252                 ret = -EINVAL;
 253                 goto create_error;
 254         }
 255         return;
 256
 257 create_error:
 258         WARN_ON(1);
 259         return;         /* not allowed to return error */
 260 }
 261
 262 static
 263 int lttng_abi_create_channel(struct file *session_file,
 264                              struct lttng_kernel_channel __user *uchan_param,
 265                              enum channel_type channel_type)
 266 {
 267         struct ltt_session *session = session_file->private_data;
 268         const struct file_operations *fops;
 269         const char *transport_name;
 270         struct ltt_channel *chan;
 271         struct file *chan_file;
 272         struct lttng_kernel_channel chan_param;
 273         int chan_fd;
 274         int ret = 0;
 275
 276         if (copy_from_user(&chan_param, uchan_param, sizeof(chan_param)))
 277                 return -EFAULT;
 278         chan_fd = get_unused_fd();
 279         if (chan_fd < 0) {
 280                 ret = chan_fd;
 281                 goto fd_error;
 282         }
 283         chan_file = anon_inode_getfile("[lttng_channel]",
 284                                        &lttng_channel_fops,
 285                                        NULL, O_RDWR);
 286         if (IS_ERR(chan_file)) {
 287                 ret = PTR_ERR(chan_file);
 288                 goto file_error;
 289         }
 290         switch (channel_type) {
 291         case PER_CPU_CHANNEL:
 292                 if (chan_param.output == LTTNG_KERNEL_SPLICE) {
 293                         transport_name = chan_param.overwrite ?
 294                                 "relay-overwrite" : "relay-discard";
 295                 } else if (chan_param.output == LTTNG_KERNEL_MMAP) {
 296                         transport_name = chan_param.overwrite ?
 297                                 "relay-overwrite-mmap" : "relay-discard-mmap";
 298                 } else {
 299                         return -EINVAL;
 300                 }
 301                 fops = &lttng_channel_fops;
 302                 break;
 303         case METADATA_CHANNEL:
 304                 if (chan_param.output == LTTNG_KERNEL_SPLICE)
 305                         transport_name = "relay-metadata";
 306                 else if (chan_param.output == LTTNG_KERNEL_MMAP)
 307                         transport_name = "relay-metadata-mmap";
 308                 else
 309                         return -EINVAL;
 310                 fops = &lttng_metadata_fops;
 311                 break;
 312         default:
 313                 transport_name = "<unknown>";
 314                 break;
 315         }
 316         /*
 317          * We tolerate no failure path after channel creation. It will stay
 318          * invariant for the rest of the session.
 319          */
 320         chan = ltt_channel_create(session, transport_name, NULL,
 321                                   chan_param.subbuf_size,
 322                                   chan_param.num_subbuf,
 323                                   chan_param.switch_timer_interval,
 324                                   chan_param.read_timer_interval);
 325         if (!chan) {
 326                 ret = -EINVAL;
 327                 goto chan_error;
 328         }
 329         chan->file = chan_file;
 330         chan_file->private_data = chan;
 331         fd_install(chan_fd, chan_file);
 332         if (channel_type == METADATA_CHANNEL) {
 333                 session->metadata = chan;
 334                 lttng_metadata_create_events(chan_file);
 335         }
 336
 337         /* The channel created holds a reference on the session */
 338         atomic_long_inc(&session_file->f_count);
 339
 340         return chan_fd;
 341
 342 chan_error:
 343         fput(chan_file);
 344 file_error:
 345         put_unused_fd(chan_fd);
 346 fd_error:
 347         return ret;
 348 }
 349
 350 /**
 351  *      lttng_session_ioctl - lttng session fd ioctl
 352  *
 353  *      @file: the file
 354  *      @cmd: the command
 355  *      @arg: command arg
 356  *
 357  *      This ioctl implements lttng commands:
 358  *      LTTNG_KERNEL_CHANNEL
 359  *              Returns a LTTng channel file descriptor
 360  *      LTTNG_KERNEL_ENABLE
 361  *              Enables tracing for a session (weak enable)
 362  *      LTTNG_KERNEL_DISABLE
 363  *              Disables tracing for a session (strong disable)
 364  *      LTTNG_KERNEL_METADATA
 365  *              Returns a LTTng metadata file descriptor
 366  *
 367  * The returned channel will be deleted when its file descriptor is closed.
 368  */
 369 static
 370 long lttng_session_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 371 {
 372         struct ltt_session *session = file->private_data;
 373
 374         switch (cmd) {
 375         case LTTNG_KERNEL_CHANNEL:
 376                 return lttng_abi_create_channel(file,
 377                                 (struct lttng_kernel_channel __user *) arg,
 378                                 PER_CPU_CHANNEL);
 379         case LTTNG_KERNEL_SESSION_START:
 380         case LTTNG_KERNEL_ENABLE:
 381                 return ltt_session_enable(session);
 382         case LTTNG_KERNEL_SESSION_STOP:
 383         case LTTNG_KERNEL_DISABLE:
 384                 return ltt_session_disable(session);
 385         case LTTNG_KERNEL_METADATA:
 386                 return lttng_abi_create_channel(file,
 387                                 (struct lttng_kernel_channel __user *) arg,
 388                                 METADATA_CHANNEL);
 389         default:
 390                 return -ENOIOCTLCMD;
 391         }
 392 }
 393
 394 /*
 395  * Called when the last file reference is dropped.
 396  *
 397  * Big fat note: channels and events are invariant for the whole session after
 398  * their creation. So this session destruction also destroys all channel and
 399  * event structures specific to this session (they are not destroyed when their
 400  * individual file is released).
 401  */
 402 static
 403 int lttng_session_release(struct inode *inode, struct file *file)
 404 {
 405         struct ltt_session *session = file->private_data;
 406
 407         if (session)
 408                 ltt_session_destroy(session);
 409         return 0;
 410 }
 411
 412 static const struct file_operations lttng_session_fops = {
 413         .release = lttng_session_release,
 414         .unlocked_ioctl = lttng_session_ioctl,
 415 #ifdef CONFIG_COMPAT
 416         .compat_ioctl = lttng_session_ioctl,
 417 #endif
 418 };
 419
 420 static
 421 int lttng_abi_open_stream(struct file *channel_file)
 422 {
 423         struct ltt_channel *channel = channel_file->private_data;
 424         struct lib_ring_buffer *buf;
 425         int stream_fd, ret;
 426         struct file *stream_file;
 427
 428         buf = channel->ops->buffer_read_open(channel->chan);
 429         if (!buf)
 430                 return -ENOENT;
 431
 432         stream_fd = get_unused_fd();
 433         if (stream_fd < 0) {
 434                 ret = stream_fd;
 435                 goto fd_error;
 436         }
 437         stream_file = anon_inode_getfile("[lttng_stream]",
 438                                          &lib_ring_buffer_file_operations,
 439                                          buf, O_RDWR);
 440         if (IS_ERR(stream_file)) {
 441                 ret = PTR_ERR(stream_file);
 442                 goto file_error;
 443         }
 444         /*
 445          * OPEN_FMODE, called within anon_inode_getfile/alloc_file, don't honor
 446          * FMODE_LSEEK, FMODE_PREAD nor FMODE_PWRITE. We need to read from this
 447          * file descriptor, so we set FMODE_PREAD here.
 448          */
 449         stream_file->f_mode |= FMODE_PREAD;
 450         fd_install(stream_fd, stream_file);
 451         /*
 452          * The stream holds a reference to the channel within the generic ring
 453          * buffer library, so no need to hold a refcount on the channel and
 454          * session files here.
 455          */
 456         return stream_fd;
 457
 458 file_error:
 459         put_unused_fd(stream_fd);
 460 fd_error:
 461         channel->ops->buffer_read_close(buf);
 462         return ret;
 463 }
 464
 465 static
 466 int lttng_abi_create_event(struct file *channel_file,
 467                            struct lttng_kernel_event __user *uevent_param)
 468 {
 469         struct ltt_channel *channel = channel_file->private_data;
 470         struct ltt_event *event;
 471         struct lttng_kernel_event event_param;
 472         int event_fd, ret;
 473         struct file *event_file;
 474
 475         if (copy_from_user(&event_param, uevent_param, sizeof(event_param)))
 476                 return -EFAULT;
 477         event_param.name[LTTNG_SYM_NAME_LEN - 1] = '\0';
 478         switch (event_param.instrumentation) {
 479         case LTTNG_KERNEL_KPROBE:
 480                 event_param.u.kprobe.symbol_name[LTTNG_SYM_NAME_LEN - 1] = '\0';
 481                 break;
 482         case LTTNG_KERNEL_FUNCTION:
 483                 event_param.u.ftrace.symbol_name[LTTNG_SYM_NAME_LEN - 1] = '\0';
 484                 break;
 485         default:
 486                 break;
 487         }
 488         event_fd = get_unused_fd();
 489         if (event_fd < 0) {
 490                 ret = event_fd;
 491                 goto fd_error;
 492         }
 493         event_file = anon_inode_getfile("[lttng_event]",
 494                                         &lttng_event_fops,
 495                                         NULL, O_RDWR);
 496         if (IS_ERR(event_file)) {
 497                 ret = PTR_ERR(event_file);
 498                 goto file_error;
 499         }
 500         /*
 501          * We tolerate no failure path after event creation. It will stay
 502          * invariant for the rest of the session.
 503          */
 504         event = ltt_event_create(channel, &event_param, NULL);
 505         if (!event) {
 506                 ret = -EINVAL;
 507                 goto event_error;
 508         }
 509         event_file->private_data = event;
 510         fd_install(event_fd, event_file);
 511         /* The event holds a reference on the channel */
 512         atomic_long_inc(&channel_file->f_count);
 513         return event_fd;
 514
 515 event_error:
 516         fput(event_file);
 517 file_error:
 518         put_unused_fd(event_fd);
 519 fd_error:
 520         return ret;
 521 }
 522
 523 /**
 524  *      lttng_channel_ioctl - lttng syscall through ioctl
 525  *
 526  *      @file: the file
 527  *      @cmd: the command
 528  *      @arg: command arg
 529  *
 530  *      This ioctl implements lttng commands:
 531  *      LTTNG_KERNEL_STREAM
 532  *              Returns an event stream file descriptor or failure.
 533  *              (typically, one event stream records events from one CPU)
 534  *      LTTNG_KERNEL_EVENT
 535  *              Returns an event file descriptor or failure.
 536  *      LTTNG_KERNEL_CONTEXT
 537  *              Prepend a context field to each event in the channel
 538  *      LTTNG_KERNEL_ENABLE
 539  *              Enable recording for events in this channel (weak enable)
 540  *      LTTNG_KERNEL_DISABLE
 541  *              Disable recording for events in this channel (strong disable)
 542  *
 543  * Channel and event file descriptors also hold a reference on the session.
 544  */
 545 static
 546 long lttng_channel_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 547 {
 548         struct ltt_channel *channel = file->private_data;
 549
 550         switch (cmd) {
 551         case LTTNG_KERNEL_STREAM:
 552                 return lttng_abi_open_stream(file);
 553         case LTTNG_KERNEL_EVENT:
 554                 return lttng_abi_create_event(file, (struct lttng_kernel_event __user *) arg);
 555         case LTTNG_KERNEL_CONTEXT:
 556                 return lttng_abi_add_context(file,
 557                                 (struct lttng_kernel_context __user *) arg,
 558                                 &channel->ctx, channel->session);
 559         case LTTNG_KERNEL_ENABLE:
 560                 return ltt_channel_enable(channel);
 561         case LTTNG_KERNEL_DISABLE:
 562                 return ltt_channel_disable(channel);
 563         default:
 564                 return -ENOIOCTLCMD;
 565         }
 566 }
 567
 568 /**
 569  *      lttng_metadata_ioctl - lttng syscall through ioctl
 570  *
 571  *      @file: the file
 572  *      @cmd: the command
 573  *      @arg: command arg
 574  *
 575  *      This ioctl implements lttng commands:
 576  *      LTTNG_KERNEL_STREAM
 577  *              Returns an event stream file descriptor or failure.
 578  *
 579  * Channel and event file descriptors also hold a reference on the session.
 580  */
 581 static
 582 long lttng_metadata_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 583 {
 584         switch (cmd) {
 585         case LTTNG_KERNEL_STREAM:
 586                 return lttng_abi_open_stream(file);
 587         default:
 588                 return -ENOIOCTLCMD;
 589         }
 590 }
 591
 592 /**
 593  *      lttng_channel_poll - lttng stream addition/removal monitoring
 594  *
 595  *      @file: the file
 596  *      @wait: poll table
 597  */
 598 unsigned int lttng_channel_poll(struct file *file, poll_table *wait)
 599 {
 600         struct ltt_channel *channel = file->private_data;
 601         unsigned int mask = 0;
 602
 603         if (file->f_mode & FMODE_READ) {
 604                 poll_wait_set_exclusive(wait);
 605                 poll_wait(file, channel->ops->get_hp_wait_queue(channel->chan),
 606                           wait);
 607
 608                 if (channel->ops->is_disabled(channel->chan))
 609                         return POLLERR;
 610                 if (channel->ops->is_finalized(channel->chan))
 611                         return POLLHUP;
 612                 else
 613                         return POLLIN | POLLRDNORM;
 614         }
 615         return mask;
 616
 617 }
 618
 619 static
 620 int lttng_channel_release(struct inode *inode, struct file *file)
 621 {
 622         struct ltt_channel *channel = file->private_data;
 623
 624         if (channel)
 625                 fput(channel->session->file);
 626         return 0;
 627 }
 628
 629 static const struct file_operations lttng_channel_fops = {
 630         .release = lttng_channel_release,
 631         .poll = lttng_channel_poll,
 632         .unlocked_ioctl = lttng_channel_ioctl,
 633 #ifdef CONFIG_COMPAT
 634         .compat_ioctl = lttng_channel_ioctl,
 635 #endif
 636 };
 637
 638 static const struct file_operations lttng_metadata_fops = {
 639         .release = lttng_channel_release,
 640         .unlocked_ioctl = lttng_metadata_ioctl,
 641 #ifdef CONFIG_COMPAT
 642         .compat_ioctl = lttng_metadata_ioctl,
 643 #endif
 644 };
 645
 646 /**
 647  *      lttng_event_ioctl - lttng syscall through ioctl
 648  *
 649  *      @file: the file
 650  *      @cmd: the command
 651  *      @arg: command arg
 652  *
 653  *      This ioctl implements lttng commands:
 654  *      LTTNG_KERNEL_CONTEXT
 655  *              Prepend a context field to each record of this event
 656  *      LTTNG_KERNEL_ENABLE
 657  *              Enable recording for this event (weak enable)
 658  *      LTTNG_KERNEL_DISABLE
 659  *              Disable recording for this event (strong disable)
 660  */
 661 static
 662 long lttng_event_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 663 {
 664         struct ltt_event *event = file->private_data;
 665
 666         switch (cmd) {
 667         case LTTNG_KERNEL_CONTEXT:
 668                 return lttng_abi_add_context(file,
 669                                 (struct lttng_kernel_context __user *) arg,
 670                                 &event->ctx, event->chan->session);
 671         case LTTNG_KERNEL_ENABLE:
 672                 return ltt_event_enable(event);
 673         case LTTNG_KERNEL_DISABLE:
 674                 return ltt_event_disable(event);
 675         default:
 676                 return -ENOIOCTLCMD;
 677         }
 678 }
 679
 680 static
 681 int lttng_event_release(struct inode *inode, struct file *file)
 682 {
 683         struct ltt_event *event = file->private_data;
 684
 685         if (event)
 686                 fput(event->chan->file);
 687         return 0;
 688 }
 689
 690 /* TODO: filter control ioctl */
 691 static const struct file_operations lttng_event_fops = {
 692         .release = lttng_event_release,
 693         .unlocked_ioctl = lttng_event_ioctl,
 694 #ifdef CONFIG_COMPAT
 695         .compat_ioctl = lttng_event_ioctl,
 696 #endif
 697 };
 698
 699 int __init ltt_debugfs_abi_init(void)
 700 {
 701         int ret = 0;
 702
 703         wrapper_vmalloc_sync_all();
 704         lttng_dentry = debugfs_create_file("lttng", S_IWUSR, NULL, NULL,
 705                                            &lttng_fops);
 706         if (IS_ERR(lttng_dentry) || !lttng_dentry) {
 707                 printk(KERN_ERR "Error creating LTTng control file\n");
 708                 ret = -ENOMEM;
 709                 goto error;
 710         }
 711 error:
 712         return ret;
 713 }
 714
 715 void __exit ltt_debugfs_abi_exit(void)
 716 {
 717         debugfs_remove(lttng_dentry);
 718 }