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 /*
  53  * Teardown management: opened file descriptors keep a refcount on the module,
  54  * so it can only exit when all file descriptors are closed.
  55  */
  56
  57 enum channel_type {
  58         PER_CPU_CHANNEL,
  59         METADATA_CHANNEL,
  60 };
  61
  62 static
  63 int lttng_abi_create_session(void)
  64 {
  65         struct ltt_session *session;
  66         struct file *session_file;
  67         int session_fd, ret;
  68
  69         session = ltt_session_create();
  70         if (!session)
  71                 return -ENOMEM;
  72         session_fd = get_unused_fd();
  73         if (session_fd < 0) {
  74                 ret = session_fd;
  75                 goto fd_error;
  76         }
  77         session_file = anon_inode_getfile("[lttng_session]",
  78                                           &lttng_session_fops,
  79                                           session, O_RDWR);
  80         if (IS_ERR(session_file)) {
  81                 ret = PTR_ERR(session_file);
  82                 goto file_error;
  83         }
  84         session->file = session_file;
  85         fd_install(session_fd, session_file);
  86         return session_fd;
  87
  88 file_error:
  89         put_unused_fd(session_fd);
  90 fd_error:
  91         ltt_session_destroy(session);
  92         return ret;
  93 }
  94
  95 static
  96 int lttng_abi_tracepoint_list(void)
  97 {
  98         struct file *tracepoint_list_file;
  99         int file_fd, ret;
 100
 101         file_fd = get_unused_fd();
 102         if (file_fd < 0) {
 103                 ret = file_fd;
 104                 goto fd_error;
 105         }
 106
 107         tracepoint_list_file = anon_inode_getfile("[lttng_session]",
 108                                           &lttng_tracepoint_list_fops,
 109                                           NULL, O_RDWR);
 110         if (IS_ERR(tracepoint_list_file)) {
 111                 ret = PTR_ERR(tracepoint_list_file);
 112                 goto file_error;
 113         }
 114         ret = lttng_tracepoint_list_fops.open(NULL, tracepoint_list_file);
 115         if (ret < 0)
 116                 goto open_error;
 117         fd_install(file_fd, tracepoint_list_file);
 118         if (file_fd < 0) {
 119                 ret = file_fd;
 120                 goto fd_error;
 121         }
 122         return file_fd;
 123
 124 open_error:
 125         fput(tracepoint_list_file);
 126 file_error:
 127         put_unused_fd(file_fd);
 128 fd_error:
 129         return ret;
 130 }
 131
 132 static
 133 long lttng_abi_tracer_version(struct file *file,
 134         struct lttng_kernel_tracer_version __user *uversion_param)
 135 {
 136         struct lttng_kernel_tracer_version v;
 137
 138         v.version = LTTNG_VERSION;
 139         v.patchlevel = LTTNG_PATCHLEVEL;
 140         v.sublevel = LTTNG_SUBLEVEL;
 141
 142         if (copy_to_user(uversion_param, &v, sizeof(v)))
 143                 return -EFAULT;
 144         return 0;
 145 }
 146
 147 static
 148 long lttng_abi_add_context(struct file *file,
 149         struct lttng_kernel_context __user *ucontext_param,
 150         struct lttng_ctx **ctx, struct ltt_session *session)
 151 {
 152         struct lttng_kernel_context context_param;
 153
 154         if (session->been_active)
 155                 return -EPERM;
 156
 157         if (copy_from_user(&context_param, ucontext_param, sizeof(context_param)))
 158                 return -EFAULT;
 159
 160         switch (context_param.ctx) {
 161         case LTTNG_KERNEL_CONTEXT_PID:
 162                 return lttng_add_pid_to_ctx(ctx);
 163         case LTTNG_KERNEL_CONTEXT_PRIO:
 164                 return lttng_add_prio_to_ctx(ctx);
 165         case LTTNG_KERNEL_CONTEXT_NICE:
 166                 return lttng_add_nice_to_ctx(ctx);
 167         case LTTNG_KERNEL_CONTEXT_VPID:
 168                 return lttng_add_vpid_to_ctx(ctx);
 169         case LTTNG_KERNEL_CONTEXT_TID:
 170                 return lttng_add_tid_to_ctx(ctx);
 171         case LTTNG_KERNEL_CONTEXT_VTID:
 172                 return lttng_add_vtid_to_ctx(ctx);
 173         case LTTNG_KERNEL_CONTEXT_PPID:
 174                 return lttng_add_ppid_to_ctx(ctx);
 175         case LTTNG_KERNEL_CONTEXT_VPPID:
 176                 return lttng_add_vppid_to_ctx(ctx);
 177         case LTTNG_KERNEL_CONTEXT_PERF_COUNTER:
 178                 context_param.u.perf_counter.name[LTTNG_SYM_NAME_LEN - 1] = '\0';
 179                 return lttng_add_perf_counter_to_ctx(context_param.u.perf_counter.type,
 180                                 context_param.u.perf_counter.config,
 181                                 context_param.u.perf_counter.name,
 182                                 ctx);
 183         case LTTNG_KERNEL_CONTEXT_COMM:
 184                 return lttng_add_comm_to_ctx(ctx);
 185         default:
 186                 return -EINVAL;
 187         }
 188 }
 189
 190 /**
 191  *      lttng_ioctl - lttng syscall through ioctl
 192  *
 193  *      @file: the file
 194  *      @cmd: the command
 195  *      @arg: command arg
 196  *
 197  *      This ioctl implements lttng commands:
 198  *      LTTNG_KERNEL_SESSION
 199  *              Returns a LTTng trace session file descriptor
 200  *      LTTNG_KERNEL_TRACER_VERSION
 201  *              Returns the LTTng kernel tracer version
 202  *      LTTNG_KERNEL_TRACEPOINT_LIST
 203  *              Returns a file descriptor listing available tracepoints
 204  *      LTTNG_KERNEL_WAIT_QUIESCENT
 205  *              Returns after all previously running probes have completed
 206  *
 207  * The returned session will be deleted when its file descriptor is closed.
 208  */
 209 static
 210 long lttng_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 211 {
 212         switch (cmd) {
 213         case LTTNG_KERNEL_SESSION:
 214                 return lttng_abi_create_session();
 215         case LTTNG_KERNEL_TRACER_VERSION:
 216                 return lttng_abi_tracer_version(file,
 217                                 (struct lttng_kernel_tracer_version __user *) arg);
 218         case LTTNG_KERNEL_TRACEPOINT_LIST:
 219                 return lttng_abi_tracepoint_list();
 220         case LTTNG_KERNEL_WAIT_QUIESCENT:
 221                 synchronize_trace();
 222                 return 0;
 223         default:
 224                 return -ENOIOCTLCMD;
 225         }
 226 }
 227
 228 static const struct file_operations lttng_fops = {
 229         .owner = THIS_MODULE,
 230         .unlocked_ioctl = lttng_ioctl,
 231 #ifdef CONFIG_COMPAT
 232         .compat_ioctl = lttng_ioctl,
 233 #endif
 234 };
 235
 236 /*
 237  * We tolerate no failure in this function (if one happens, we print a dmesg
 238  * error, but cannot return any error, because the channel information is
 239  * invariant.
 240  */
 241 static
 242 void lttng_metadata_create_events(struct file *channel_file)
 243 {
 244         struct ltt_channel *channel = channel_file->private_data;
 245         static struct lttng_kernel_event metadata_params = {
 246                 .instrumentation = LTTNG_KERNEL_TRACEPOINT,
 247                 .name = "lttng_metadata",
 248         };
 249         struct ltt_event *event;
 250
 251         /*
 252          * We tolerate no failure path after event creation. It will stay
 253          * invariant for the rest of the session.
 254          */
 255         event = ltt_event_create(channel, &metadata_params, NULL);
 256         if (!event) {
 257                 goto create_error;
 258         }
 259         return;
 260
 261 create_error:
 262         WARN_ON(1);
 263         return;         /* not allowed to return error */
 264 }
 265
 266 static
 267 int lttng_abi_create_channel(struct file *session_file,
 268                              struct lttng_kernel_channel __user *uchan_param,
 269                              enum channel_type channel_type)
 270 {
 271         struct ltt_session *session = session_file->private_data;
 272         const struct file_operations *fops = NULL;
 273         const char *transport_name;
 274         struct ltt_channel *chan;
 275         struct file *chan_file;
 276         struct lttng_kernel_channel chan_param;
 277         int chan_fd;
 278         int ret = 0;
 279
 280         if (copy_from_user(&chan_param, uchan_param, sizeof(chan_param)))
 281                 return -EFAULT;
 282         chan_fd = get_unused_fd();
 283         if (chan_fd < 0) {
 284                 ret = chan_fd;
 285                 goto fd_error;
 286         }
 287         switch (channel_type) {
 288         case PER_CPU_CHANNEL:
 289                 fops = &lttng_channel_fops;
 290                 break;
 291         case METADATA_CHANNEL:
 292                 fops = &lttng_metadata_fops;
 293                 break;
 294         }
 295
 296         chan_file = anon_inode_getfile("[lttng_channel]",
 297                                        fops,
 298                                        NULL, O_RDWR);
 299         if (IS_ERR(chan_file)) {
 300                 ret = PTR_ERR(chan_file);
 301                 goto file_error;
 302         }
 303         switch (channel_type) {
 304         case PER_CPU_CHANNEL:
 305                 if (chan_param.output == LTTNG_KERNEL_SPLICE) {
 306                         transport_name = chan_param.overwrite ?
 307                                 "relay-overwrite" : "relay-discard";
 308                 } else if (chan_param.output == LTTNG_KERNEL_MMAP) {
 309                         transport_name = chan_param.overwrite ?
 310                                 "relay-overwrite-mmap" : "relay-discard-mmap";
 311                 } else {
 312                         return -EINVAL;
 313                 }
 314                 break;
 315         case METADATA_CHANNEL:
 316                 if (chan_param.output == LTTNG_KERNEL_SPLICE)
 317                         transport_name = "relay-metadata";
 318                 else if (chan_param.output == LTTNG_KERNEL_MMAP)
 319                         transport_name = "relay-metadata-mmap";
 320                 else
 321                         return -EINVAL;
 322                 break;
 323         default:
 324                 transport_name = "<unknown>";
 325                 break;
 326         }
 327         /*
 328          * We tolerate no failure path after channel creation. It will stay
 329          * invariant for the rest of the session.
 330          */
 331         chan = ltt_channel_create(session, transport_name, NULL,
 332                                   chan_param.subbuf_size,
 333                                   chan_param.num_subbuf,
 334                                   chan_param.switch_timer_interval,
 335                                   chan_param.read_timer_interval);
 336         if (!chan) {
 337                 ret = -EINVAL;
 338                 goto chan_error;
 339         }
 340         chan->file = chan_file;
 341         chan_file->private_data = chan;
 342         fd_install(chan_fd, chan_file);
 343         if (channel_type == METADATA_CHANNEL) {
 344                 session->metadata = chan;
 345                 lttng_metadata_create_events(chan_file);
 346         }
 347
 348         /* The channel created holds a reference on the session */
 349         atomic_long_inc(&session_file->f_count);
 350
 351         return chan_fd;
 352
 353 chan_error:
 354         fput(chan_file);
 355 file_error:
 356         put_unused_fd(chan_fd);
 357 fd_error:
 358         return ret;
 359 }
 360
 361 /**
 362  *      lttng_session_ioctl - lttng session fd ioctl
 363  *
 364  *      @file: the file
 365  *      @cmd: the command
 366  *      @arg: command arg
 367  *
 368  *      This ioctl implements lttng commands:
 369  *      LTTNG_KERNEL_CHANNEL
 370  *              Returns a LTTng channel file descriptor
 371  *      LTTNG_KERNEL_ENABLE
 372  *              Enables tracing for a session (weak enable)
 373  *      LTTNG_KERNEL_DISABLE
 374  *              Disables tracing for a session (strong disable)
 375  *      LTTNG_KERNEL_METADATA
 376  *              Returns a LTTng metadata file descriptor
 377  *
 378  * The returned channel will be deleted when its file descriptor is closed.
 379  */
 380 static
 381 long lttng_session_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 382 {
 383         struct ltt_session *session = file->private_data;
 384
 385         switch (cmd) {
 386         case LTTNG_KERNEL_CHANNEL:
 387                 return lttng_abi_create_channel(file,
 388                                 (struct lttng_kernel_channel __user *) arg,
 389                                 PER_CPU_CHANNEL);
 390         case LTTNG_KERNEL_SESSION_START:
 391         case LTTNG_KERNEL_ENABLE:
 392                 return ltt_session_enable(session);
 393         case LTTNG_KERNEL_SESSION_STOP:
 394         case LTTNG_KERNEL_DISABLE:
 395                 return ltt_session_disable(session);
 396         case LTTNG_KERNEL_METADATA:
 397                 return lttng_abi_create_channel(file,
 398                                 (struct lttng_kernel_channel __user *) arg,
 399                                 METADATA_CHANNEL);
 400         default:
 401                 return -ENOIOCTLCMD;
 402         }
 403 }
 404
 405 /*
 406  * Called when the last file reference is dropped.
 407  *
 408  * Big fat note: channels and events are invariant for the whole session after
 409  * their creation. So this session destruction also destroys all channel and
 410  * event structures specific to this session (they are not destroyed when their
 411  * individual file is released).
 412  */
 413 static
 414 int lttng_session_release(struct inode *inode, struct file *file)
 415 {
 416         struct ltt_session *session = file->private_data;
 417
 418         if (session)
 419                 ltt_session_destroy(session);
 420         return 0;
 421 }
 422
 423 static const struct file_operations lttng_session_fops = {
 424         .owner = THIS_MODULE,
 425         .release = lttng_session_release,
 426         .unlocked_ioctl = lttng_session_ioctl,
 427 #ifdef CONFIG_COMPAT
 428         .compat_ioctl = lttng_session_ioctl,
 429 #endif
 430 };
 431
 432 static
 433 int lttng_abi_open_stream(struct file *channel_file)
 434 {
 435         struct ltt_channel *channel = channel_file->private_data;
 436         struct lib_ring_buffer *buf;
 437         int stream_fd, ret;
 438         struct file *stream_file;
 439
 440         buf = channel->ops->buffer_read_open(channel->chan);
 441         if (!buf)
 442                 return -ENOENT;
 443
 444         stream_fd = get_unused_fd();
 445         if (stream_fd < 0) {
 446                 ret = stream_fd;
 447                 goto fd_error;
 448         }
 449         stream_file = anon_inode_getfile("[lttng_stream]",
 450                                          &lib_ring_buffer_file_operations,
 451                                          buf, O_RDWR);
 452         if (IS_ERR(stream_file)) {
 453                 ret = PTR_ERR(stream_file);
 454                 goto file_error;
 455         }
 456         /*
 457          * OPEN_FMODE, called within anon_inode_getfile/alloc_file, don't honor
 458          * FMODE_LSEEK, FMODE_PREAD nor FMODE_PWRITE. We need to read from this
 459          * file descriptor, so we set FMODE_PREAD here.
 460          */
 461         stream_file->f_mode |= FMODE_PREAD;
 462         fd_install(stream_fd, stream_file);
 463         /*
 464          * The stream holds a reference to the channel within the generic ring
 465          * buffer library, so no need to hold a refcount on the channel and
 466          * session files here.
 467          */
 468         return stream_fd;
 469
 470 file_error:
 471         put_unused_fd(stream_fd);
 472 fd_error:
 473         channel->ops->buffer_read_close(buf);
 474         return ret;
 475 }
 476
 477 static
 478 int lttng_abi_create_event(struct file *channel_file,
 479                            struct lttng_kernel_event __user *uevent_param)
 480 {
 481         struct ltt_channel *channel = channel_file->private_data;
 482         struct ltt_event *event;
 483         struct lttng_kernel_event event_param;
 484         int event_fd, ret;
 485         struct file *event_file;
 486
 487         if (copy_from_user(&event_param, uevent_param, sizeof(event_param)))
 488                 return -EFAULT;
 489         event_param.name[LTTNG_SYM_NAME_LEN - 1] = '\0';
 490         switch (event_param.instrumentation) {
 491         case LTTNG_KERNEL_KPROBE:
 492                 event_param.u.kprobe.symbol_name[LTTNG_SYM_NAME_LEN - 1] = '\0';
 493                 break;
 494         case LTTNG_KERNEL_FUNCTION:
 495                 event_param.u.ftrace.symbol_name[LTTNG_SYM_NAME_LEN - 1] = '\0';
 496                 break;
 497         default:
 498                 break;
 499         }
 500         event_fd = get_unused_fd();
 501         if (event_fd < 0) {
 502                 ret = event_fd;
 503                 goto fd_error;
 504         }
 505         event_file = anon_inode_getfile("[lttng_event]",
 506                                         &lttng_event_fops,
 507                                         NULL, O_RDWR);
 508         if (IS_ERR(event_file)) {
 509                 ret = PTR_ERR(event_file);
 510                 goto file_error;
 511         }
 512         /*
 513          * We tolerate no failure path after event creation. It will stay
 514          * invariant for the rest of the session.
 515          */
 516         event = ltt_event_create(channel, &event_param, NULL);
 517         if (!event) {
 518                 ret = -EINVAL;
 519                 goto event_error;
 520         }
 521         event_file->private_data = event;
 522         fd_install(event_fd, event_file);
 523         /* The event holds a reference on the channel */
 524         atomic_long_inc(&channel_file->f_count);
 525         return event_fd;
 526
 527 event_error:
 528         fput(event_file);
 529 file_error:
 530         put_unused_fd(event_fd);
 531 fd_error:
 532         return ret;
 533 }
 534
 535 /**
 536  *      lttng_channel_ioctl - lttng syscall through ioctl
 537  *
 538  *      @file: the file
 539  *      @cmd: the command
 540  *      @arg: command arg
 541  *
 542  *      This ioctl implements lttng commands:
 543  *      LTTNG_KERNEL_STREAM
 544  *              Returns an event stream file descriptor or failure.
 545  *              (typically, one event stream records events from one CPU)
 546  *      LTTNG_KERNEL_EVENT
 547  *              Returns an event file descriptor or failure.
 548  *      LTTNG_KERNEL_CONTEXT
 549  *              Prepend a context field to each event in the channel
 550  *      LTTNG_KERNEL_ENABLE
 551  *              Enable recording for events in this channel (weak enable)
 552  *      LTTNG_KERNEL_DISABLE
 553  *              Disable recording for events in this channel (strong disable)
 554  *
 555  * Channel and event file descriptors also hold a reference on the session.
 556  */
 557 static
 558 long lttng_channel_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 559 {
 560         struct ltt_channel *channel = file->private_data;
 561
 562         switch (cmd) {
 563         case LTTNG_KERNEL_STREAM:
 564                 return lttng_abi_open_stream(file);
 565         case LTTNG_KERNEL_EVENT:
 566                 return lttng_abi_create_event(file, (struct lttng_kernel_event __user *) arg);
 567         case LTTNG_KERNEL_CONTEXT:
 568                 return lttng_abi_add_context(file,
 569                                 (struct lttng_kernel_context __user *) arg,
 570                                 &channel->ctx, channel->session);
 571         case LTTNG_KERNEL_ENABLE:
 572                 return ltt_channel_enable(channel);
 573         case LTTNG_KERNEL_DISABLE:
 574                 return ltt_channel_disable(channel);
 575         default:
 576                 return -ENOIOCTLCMD;
 577         }
 578 }
 579
 580 /**
 581  *      lttng_metadata_ioctl - lttng syscall through ioctl
 582  *
 583  *      @file: the file
 584  *      @cmd: the command
 585  *      @arg: command arg
 586  *
 587  *      This ioctl implements lttng commands:
 588  *      LTTNG_KERNEL_STREAM
 589  *              Returns an event stream file descriptor or failure.
 590  *
 591  * Channel and event file descriptors also hold a reference on the session.
 592  */
 593 static
 594 long lttng_metadata_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 595 {
 596         switch (cmd) {
 597         case LTTNG_KERNEL_STREAM:
 598                 return lttng_abi_open_stream(file);
 599         default:
 600                 return -ENOIOCTLCMD;
 601         }
 602 }
 603
 604 /**
 605  *      lttng_channel_poll - lttng stream addition/removal monitoring
 606  *
 607  *      @file: the file
 608  *      @wait: poll table
 609  */
 610 unsigned int lttng_channel_poll(struct file *file, poll_table *wait)
 611 {
 612         struct ltt_channel *channel = file->private_data;
 613         unsigned int mask = 0;
 614
 615         if (file->f_mode & FMODE_READ) {
 616                 poll_wait_set_exclusive(wait);
 617                 poll_wait(file, channel->ops->get_hp_wait_queue(channel->chan),
 618                           wait);
 619
 620                 if (channel->ops->is_disabled(channel->chan))
 621                         return POLLERR;
 622                 if (channel->ops->is_finalized(channel->chan))
 623                         return POLLHUP;
 624                 if (channel->ops->buffer_has_read_closed_stream(channel->chan))
 625                         return POLLIN | POLLRDNORM;
 626                 return 0;
 627         }
 628         return mask;
 629
 630 }
 631
 632 static
 633 int lttng_channel_release(struct inode *inode, struct file *file)
 634 {
 635         struct ltt_channel *channel = file->private_data;
 636
 637         if (channel)
 638                 fput(channel->session->file);
 639         return 0;
 640 }
 641
 642 static const struct file_operations lttng_channel_fops = {
 643         .owner = THIS_MODULE,
 644         .release = lttng_channel_release,
 645         .poll = lttng_channel_poll,
 646         .unlocked_ioctl = lttng_channel_ioctl,
 647 #ifdef CONFIG_COMPAT
 648         .compat_ioctl = lttng_channel_ioctl,
 649 #endif
 650 };
 651
 652 static const struct file_operations lttng_metadata_fops = {
 653         .owner = THIS_MODULE,
 654         .release = lttng_channel_release,
 655         .unlocked_ioctl = lttng_metadata_ioctl,
 656 #ifdef CONFIG_COMPAT
 657         .compat_ioctl = lttng_metadata_ioctl,
 658 #endif
 659 };
 660
 661 /**
 662  *      lttng_event_ioctl - lttng syscall through ioctl
 663  *
 664  *      @file: the file
 665  *      @cmd: the command
 666  *      @arg: command arg
 667  *
 668  *      This ioctl implements lttng commands:
 669  *      LTTNG_KERNEL_CONTEXT
 670  *              Prepend a context field to each record of this event
 671  *      LTTNG_KERNEL_ENABLE
 672  *              Enable recording for this event (weak enable)
 673  *      LTTNG_KERNEL_DISABLE
 674  *              Disable recording for this event (strong disable)
 675  */
 676 static
 677 long lttng_event_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 678 {
 679         struct ltt_event *event = file->private_data;
 680
 681         switch (cmd) {
 682         case LTTNG_KERNEL_CONTEXT:
 683                 return lttng_abi_add_context(file,
 684                                 (struct lttng_kernel_context __user *) arg,
 685                                 &event->ctx, event->chan->session);
 686         case LTTNG_KERNEL_ENABLE:
 687                 return ltt_event_enable(event);
 688         case LTTNG_KERNEL_DISABLE:
 689                 return ltt_event_disable(event);
 690         default:
 691                 return -ENOIOCTLCMD;
 692         }
 693 }
 694
 695 static
 696 int lttng_event_release(struct inode *inode, struct file *file)
 697 {
 698         struct ltt_event *event = file->private_data;
 699
 700         if (event)
 701                 fput(event->chan->file);
 702         return 0;
 703 }
 704
 705 /* TODO: filter control ioctl */
 706 static const struct file_operations lttng_event_fops = {
 707         .owner = THIS_MODULE,
 708         .release = lttng_event_release,
 709         .unlocked_ioctl = lttng_event_ioctl,
 710 #ifdef CONFIG_COMPAT
 711         .compat_ioctl = lttng_event_ioctl,
 712 #endif
 713 };
 714
 715 int __init ltt_debugfs_abi_init(void)
 716 {
 717         int ret = 0;
 718
 719         wrapper_vmalloc_sync_all();
 720         lttng_dentry = debugfs_create_file("lttng", S_IWUSR, NULL, NULL,
 721                                            &lttng_fops);
 722         if (IS_ERR(lttng_dentry) || !lttng_dentry) {
 723                 printk(KERN_ERR "Error creating LTTng control file\n");
 724                 ret = -ENOMEM;
 725                 goto error;
 726         }
 727 error:
 728         return ret;
 729 }
 730
 731 void __exit ltt_debugfs_abi_exit(void)
 732 {
 733         debugfs_remove(lttng_dentry);
 734 }