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