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