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