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