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_NICE:
 158                 return lttng_add_nice_to_ctx(ctx);
 159         case LTTNG_KERNEL_CONTEXT_PERF_COUNTER:
 160                 return -ENOSYS;
 161         case LTTNG_KERNEL_CONTEXT_COMM:
 162                 return lttng_add_comm_to_ctx(ctx);
 163         default:
 164                 return -EINVAL;
 165         }
 166 }
 167
 168 /**
 169  *      lttng_ioctl - lttng syscall through ioctl
 170  *
 171  *      @file: the file
 172  *      @cmd: the command
 173  *      @arg: command arg
 174  *
 175  *      This ioctl implements lttng commands:
 176  *      LTTNG_KERNEL_SESSION
 177  *              Returns a LTTng trace session file descriptor
 178  *      LTTNG_KERNEL_TRACER_VERSION
 179  *              Returns the LTTng kernel tracer version
 180  *      LTTNG_KERNEL_TRACEPOINT_LIST
 181  *              Returns a file descriptor listing available tracepoints
 182  *
 183  * The returned session will be deleted when its file descriptor is closed.
 184  */
 185 static
 186 long lttng_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 187 {
 188         switch (cmd) {
 189         case LTTNG_KERNEL_SESSION:
 190                 return lttng_abi_create_session();
 191         case LTTNG_KERNEL_TRACER_VERSION:
 192                 return lttng_abi_tracer_version(file,
 193                                 (struct lttng_kernel_tracer_version __user *) arg);
 194         case LTTNG_KERNEL_TRACEPOINT_LIST:
 195                 return lttng_abi_tracepoint_list();
 196         default:
 197                 return -ENOIOCTLCMD;
 198         }
 199 }
 200
 201 static const struct file_operations lttng_fops = {
 202         .unlocked_ioctl = lttng_ioctl,
 203 #ifdef CONFIG_COMPAT
 204         .compat_ioctl = lttng_ioctl,
 205 #endif
 206 };
 207
 208 /*
 209  * We tolerate no failure in this function (if one happens, we print a dmesg
 210  * error, but cannot return any error, because the channel information is
 211  * invariant.
 212  */
 213 static
 214 void lttng_metadata_create_events(struct file *channel_file)
 215 {
 216         struct ltt_channel *channel = channel_file->private_data;
 217         static struct lttng_kernel_event metadata_params = {
 218                 .instrumentation = LTTNG_KERNEL_TRACEPOINT,
 219                 .name = "lttng_metadata",
 220         };
 221         struct ltt_event *event;
 222         int ret;
 223
 224         /*
 225          * We tolerate no failure path after event creation. It will stay
 226          * invariant for the rest of the session.
 227          */
 228         event = ltt_event_create(channel, &metadata_params, NULL);
 229         if (!event) {
 230                 ret = -EINVAL;
 231                 goto create_error;
 232         }
 233         return;
 234
 235 create_error:
 236         WARN_ON(1);
 237         return;         /* not allowed to return error */
 238 }
 239
 240 static
 241 int lttng_abi_create_channel(struct file *session_file,
 242                              struct lttng_kernel_channel __user *uchan_param,
 243                              enum channel_type channel_type)
 244 {
 245         struct ltt_session *session = session_file->private_data;
 246         const struct file_operations *fops;
 247         const char *transport_name;
 248         struct ltt_channel *chan;
 249         struct file *chan_file;
 250         struct lttng_kernel_channel chan_param;
 251         int chan_fd;
 252         int ret = 0;
 253
 254         if (copy_from_user(&chan_param, uchan_param, sizeof(chan_param)))
 255                 return -EFAULT;
 256         chan_fd = get_unused_fd();
 257         if (chan_fd < 0) {
 258                 ret = chan_fd;
 259                 goto fd_error;
 260         }
 261         chan_file = anon_inode_getfile("[lttng_channel]",
 262                                        &lttng_channel_fops,
 263                                        NULL, O_RDWR);
 264         if (IS_ERR(chan_file)) {
 265                 ret = PTR_ERR(chan_file);
 266                 goto file_error;
 267         }
 268         switch (channel_type) {
 269         case PER_CPU_CHANNEL:
 270                 transport_name = chan_param.overwrite ?
 271                         "relay-overwrite" : "relay-discard";
 272                 fops = &lttng_channel_fops;
 273                 break;
 274         case METADATA_CHANNEL:
 275                 transport_name = "relay-metadata";
 276                 fops = &lttng_metadata_fops;
 277                 break;
 278         default:
 279                 transport_name = "<unknown>";
 280                 break;
 281         }
 282         /*
 283          * We tolerate no failure path after channel creation. It will stay
 284          * invariant for the rest of the session.
 285          */
 286         chan = ltt_channel_create(session, transport_name, NULL,
 287                                   chan_param.subbuf_size,
 288                                   chan_param.num_subbuf,
 289                                   chan_param.switch_timer_interval,
 290                                   chan_param.read_timer_interval);
 291         if (!chan) {
 292                 ret = -EINVAL;
 293                 goto chan_error;
 294         }
 295         chan->file = chan_file;
 296         chan_file->private_data = chan;
 297         fd_install(chan_fd, chan_file);
 298         if (channel_type == METADATA_CHANNEL) {
 299                 session->metadata = chan;
 300                 lttng_metadata_create_events(chan_file);
 301         }
 302
 303         /* The channel created holds a reference on the session */
 304         atomic_long_inc(&session_file->f_count);
 305
 306         return chan_fd;
 307
 308 chan_error:
 309         fput(chan_file);
 310 file_error:
 311         put_unused_fd(chan_fd);
 312 fd_error:
 313         return ret;
 314 }
 315
 316 /**
 317  *      lttng_session_ioctl - lttng session fd ioctl
 318  *
 319  *      @file: the file
 320  *      @cmd: the command
 321  *      @arg: command arg
 322  *
 323  *      This ioctl implements lttng commands:
 324  *      LTTNG_KERNEL_CHANNEL
 325  *              Returns a LTTng channel file descriptor
 326  *      LTTNG_KERNEL_SESSION_START
 327  *              Starts tracing session
 328  *      LTTNG_KERNEL_SESSION_STOP
 329  *              Stops tracing session
 330  *      LTTNG_KERNEL_METADATA
 331  *              Returns a LTTng metadata file descriptor
 332  *
 333  * The returned channel will be deleted when its file descriptor is closed.
 334  */
 335 static
 336 long lttng_session_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 337 {
 338         struct ltt_session *session = file->private_data;
 339
 340         switch (cmd) {
 341         case LTTNG_KERNEL_CHANNEL:
 342                 return lttng_abi_create_channel(file,
 343                                 (struct lttng_kernel_channel __user *) arg,
 344                                 PER_CPU_CHANNEL);
 345         case LTTNG_KERNEL_SESSION_START:
 346                 return ltt_session_start(session);
 347         case LTTNG_KERNEL_SESSION_STOP:
 348                 return ltt_session_stop(session);
 349         case LTTNG_KERNEL_METADATA:
 350                 return lttng_abi_create_channel(file,
 351                                 (struct lttng_kernel_channel __user *) arg,
 352                                 METADATA_CHANNEL);
 353         default:
 354                 return -ENOIOCTLCMD;
 355         }
 356 }
 357
 358 /*
 359  * Called when the last file reference is dropped.
 360  *
 361  * Big fat note: channels and events are invariant for the whole session after
 362  * their creation. So this session destruction also destroys all channel and
 363  * event structures specific to this session (they are not destroyed when their
 364  * individual file is released).
 365  */
 366 static
 367 int lttng_session_release(struct inode *inode, struct file *file)
 368 {
 369         struct ltt_session *session = file->private_data;
 370
 371         if (session)
 372                 ltt_session_destroy(session);
 373         return 0;
 374 }
 375
 376 static const struct file_operations lttng_session_fops = {
 377         .release = lttng_session_release,
 378         .unlocked_ioctl = lttng_session_ioctl,
 379 #ifdef CONFIG_COMPAT
 380         .compat_ioctl = lttng_session_ioctl,
 381 #endif
 382 };
 383
 384 static
 385 int lttng_abi_open_stream(struct file *channel_file)
 386 {
 387         struct ltt_channel *channel = channel_file->private_data;
 388         struct lib_ring_buffer *buf;
 389         int stream_fd, ret;
 390         struct file *stream_file;
 391
 392         buf = channel->ops->buffer_read_open(channel->chan);
 393         if (!buf)
 394                 return -ENOENT;
 395
 396         stream_fd = get_unused_fd();
 397         if (stream_fd < 0) {
 398                 ret = stream_fd;
 399                 goto fd_error;
 400         }
 401         stream_file = anon_inode_getfile("[lttng_stream]",
 402                                          &lib_ring_buffer_file_operations,
 403                                          buf, O_RDWR);
 404         if (IS_ERR(stream_file)) {
 405                 ret = PTR_ERR(stream_file);
 406                 goto file_error;
 407         }
 408         /*
 409          * OPEN_FMODE, called within anon_inode_getfile/alloc_file, don't honor
 410          * FMODE_LSEEK, FMODE_PREAD nor FMODE_PWRITE. We need to read from this
 411          * file descriptor, so we set FMODE_PREAD here.
 412          */
 413         stream_file->f_mode |= FMODE_PREAD;
 414         fd_install(stream_fd, stream_file);
 415         /*
 416          * The stream holds a reference to the channel within the generic ring
 417          * buffer library, so no need to hold a refcount on the channel and
 418          * session files here.
 419          */
 420         return stream_fd;
 421
 422 file_error:
 423         put_unused_fd(stream_fd);
 424 fd_error:
 425         channel->ops->buffer_read_close(buf);
 426         return ret;
 427 }
 428
 429 static
 430 int lttng_abi_create_event(struct file *channel_file,
 431                            struct lttng_kernel_event __user *uevent_param)
 432 {
 433         struct ltt_channel *channel = channel_file->private_data;
 434         struct ltt_event *event;
 435         struct lttng_kernel_event event_param;
 436         int event_fd, ret;
 437         struct file *event_file;
 438
 439         if (copy_from_user(&event_param, uevent_param, sizeof(event_param)))
 440                 return -EFAULT;
 441         event_param.name[LTTNG_SYM_NAME_LEN - 1] = '\0';
 442         switch (event_param.instrumentation) {
 443         case LTTNG_KERNEL_KPROBE:
 444                 event_param.u.kprobe.symbol_name[LTTNG_SYM_NAME_LEN - 1] = '\0';
 445                 break;
 446         case LTTNG_KERNEL_FUNCTION:
 447                 event_param.u.ftrace.symbol_name[LTTNG_SYM_NAME_LEN - 1] = '\0';
 448                 break;
 449         default:
 450                 break;
 451         }
 452         event_fd = get_unused_fd();
 453         if (event_fd < 0) {
 454                 ret = event_fd;
 455                 goto fd_error;
 456         }
 457         event_file = anon_inode_getfile("[lttng_event]",
 458                                         &lttng_event_fops,
 459                                         NULL, O_RDWR);
 460         if (IS_ERR(event_file)) {
 461                 ret = PTR_ERR(event_file);
 462                 goto file_error;
 463         }
 464         /*
 465          * We tolerate no failure path after event creation. It will stay
 466          * invariant for the rest of the session.
 467          */
 468         event = ltt_event_create(channel, &event_param, NULL);
 469         if (!event) {
 470                 ret = -EINVAL;
 471                 goto event_error;
 472         }
 473         event_file->private_data = event;
 474         fd_install(event_fd, event_file);
 475         /* The event holds a reference on the channel */
 476         atomic_long_inc(&channel_file->f_count);
 477         return event_fd;
 478
 479 event_error:
 480         fput(event_file);
 481 file_error:
 482         put_unused_fd(event_fd);
 483 fd_error:
 484         return ret;
 485 }
 486
 487 /**
 488  *      lttng_channel_ioctl - lttng syscall through ioctl
 489  *
 490  *      @file: the file
 491  *      @cmd: the command
 492  *      @arg: command arg
 493  *
 494  *      This ioctl implements lttng commands:
 495  *      LTTNG_KERNEL_STREAM
 496  *              Returns an event stream file descriptor or failure.
 497  *              (typically, one event stream records events from one CPU)
 498  *      LTTNG_KERNEL_EVENT
 499  *              Returns an event file descriptor or failure.
 500  *      LTTNG_KERNEL_CONTEXT
 501  *              Prepend a context field to each event in the channel
 502  *
 503  * Channel and event file descriptors also hold a reference on the session.
 504  */
 505 static
 506 long lttng_channel_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 507 {
 508         struct ltt_channel *channel = file->private_data;
 509
 510         switch (cmd) {
 511         case LTTNG_KERNEL_STREAM:
 512                 return lttng_abi_open_stream(file);
 513         case LTTNG_KERNEL_EVENT:
 514                 return lttng_abi_create_event(file, (struct lttng_kernel_event __user *) arg);
 515         case LTTNG_KERNEL_CONTEXT:
 516                 return lttng_abi_add_context(file,
 517                                 (struct lttng_kernel_context __user *) arg,
 518                                 &channel->ctx, channel->session);
 519         default:
 520                 return -ENOIOCTLCMD;
 521         }
 522 }
 523
 524 /**
 525  *      lttng_metadata_ioctl - lttng syscall through ioctl
 526  *
 527  *      @file: the file
 528  *      @cmd: the command
 529  *      @arg: command arg
 530  *
 531  *      This ioctl implements lttng commands:
 532  *      LTTNG_KERNEL_STREAM
 533  *              Returns an event stream file descriptor or failure.
 534  *
 535  * Channel and event file descriptors also hold a reference on the session.
 536  */
 537 static
 538 long lttng_metadata_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 539 {
 540         switch (cmd) {
 541         case LTTNG_KERNEL_STREAM:
 542                 return lttng_abi_open_stream(file);
 543         default:
 544                 return -ENOIOCTLCMD;
 545         }
 546 }
 547
 548 /* TODO: poll */
 549 #if 0
 550 /**
 551  *      lttng_channel_poll - lttng stream addition/removal monitoring
 552  *
 553  *      @file: the file
 554  *      @wait: poll table
 555  */
 556 unsigned int lttng_channel_poll(struct file *file, poll_table *wait)
 557 {
 558         struct ltt_channel *channel = file->private_data;
 559         unsigned int mask = 0;
 560
 561         if (file->f_mode & FMODE_READ) {
 562                 poll_wait_set_exclusive(wait);
 563                 poll_wait(file, &channel->notify_wait, wait);
 564
 565                 /* TODO: identify when the channel is being finalized. */
 566                 if (finalized)
 567                         return POLLHUP;
 568                 else
 569                         return POLLIN | POLLRDNORM;
 570         }
 571         return mask;
 572
 573 }
 574 #endif //0
 575
 576 static
 577 int lttng_channel_release(struct inode *inode, struct file *file)
 578 {
 579         struct ltt_channel *channel = file->private_data;
 580
 581         if (channel)
 582                 fput(channel->session->file);
 583         return 0;
 584 }
 585
 586 static const struct file_operations lttng_channel_fops = {
 587         .release = lttng_channel_release,
 588 /* TODO */
 589 #if 0
 590         .poll = lttng_channel_poll,
 591 #endif //0
 592         .unlocked_ioctl = lttng_channel_ioctl,
 593 #ifdef CONFIG_COMPAT
 594         .compat_ioctl = lttng_channel_ioctl,
 595 #endif
 596 };
 597
 598 static const struct file_operations lttng_metadata_fops = {
 599         .release = lttng_channel_release,
 600         .unlocked_ioctl = lttng_metadata_ioctl,
 601 #ifdef CONFIG_COMPAT
 602         .compat_ioctl = lttng_metadata_ioctl,
 603 #endif
 604 };
 605
 606 /**
 607  *      lttng_event_ioctl - lttng syscall through ioctl
 608  *
 609  *      @file: the file
 610  *      @cmd: the command
 611  *      @arg: command arg
 612  *
 613  *      This ioctl implements lttng commands:
 614  *      LTTNG_KERNEL_STREAM
 615  *              Returns an event stream file descriptor or failure.
 616  *              (typically, one event stream records events from one CPU)
 617  *      LTTNG_KERNEL_EVENT
 618  *              Returns an event file descriptor or failure.
 619  *      LTTNG_KERNEL_CONTEXT
 620  *              Prepend a context field to each record of this event
 621  */
 622 static
 623 long lttng_event_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 624 {
 625         struct ltt_event *event = file->private_data;
 626
 627         switch (cmd) {
 628         case LTTNG_KERNEL_CONTEXT:
 629                 return lttng_abi_add_context(file,
 630                                 (struct lttng_kernel_context __user *) arg,
 631                                 &event->ctx, event->chan->session);
 632         default:
 633                 return -ENOIOCTLCMD;
 634         }
 635 }
 636
 637 static
 638 int lttng_event_release(struct inode *inode, struct file *file)
 639 {
 640         struct ltt_event *event = file->private_data;
 641
 642         if (event)
 643                 fput(event->chan->file);
 644         return 0;
 645 }
 646
 647 /* TODO: filter control ioctl */
 648 static const struct file_operations lttng_event_fops = {
 649         .release = lttng_event_release,
 650         .unlocked_ioctl = lttng_event_ioctl,
 651 #ifdef CONFIG_COMPAT
 652         .compat_ioctl = lttng_event_ioctl,
 653 #endif
 654 };
 655
 656 int __init ltt_debugfs_abi_init(void)
 657 {
 658         int ret = 0;
 659
 660         wrapper_vmalloc_sync_all();
 661         lttng_dentry = debugfs_create_file("lttng", S_IWUSR, NULL, NULL,
 662                                            &lttng_fops);
 663         if (IS_ERR(lttng_dentry) || !lttng_dentry) {
 664                 printk(KERN_ERR "Error creating LTTng control file\n");
 665                 ret = -ENOMEM;
 666                 goto error;
 667         }
 668 error:
 669         return ret;
 670 }
 671
 672 void __exit ltt_debugfs_abi_exit(void)
 673 {
 674         debugfs_remove(lttng_dentry);
 675 }