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 /**
 140  *      lttng_ioctl - lttng syscall through ioctl
 141  *
 142  *      @file: the file
 143  *      @cmd: the command
 144  *      @arg: command arg
 145  *
 146  *      This ioctl implements lttng commands:
 147  *      LTTNG_KERNEL_SESSION
 148  *              Returns a LTTng trace session file descriptor
 149  *      LTTNG_KERNEL_TRACER_VERSION
 150  *              Returns the LTTng kernel tracer version
 151  *      LTTNG_KERNEL_TRACEPOINT_LIST
 152  *              Returns a file descriptor listing available tracepoints
 153  *
 154  * The returned session will be deleted when its file descriptor is closed.
 155  */
 156 static
 157 long lttng_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 158 {
 159         switch (cmd) {
 160         case LTTNG_KERNEL_SESSION:
 161                 return lttng_abi_create_session();
 162         case LTTNG_KERNEL_TRACER_VERSION:
 163                 return lttng_abi_tracer_version(file,
 164                                 (struct lttng_kernel_tracer_version __user *) arg);
 165         case LTTNG_KERNEL_TRACEPOINT_LIST:
 166                 return lttng_abi_tracepoint_list();
 167         default:
 168                 return -ENOIOCTLCMD;
 169         }
 170 }
 171
 172 static const struct file_operations lttng_fops = {
 173         .unlocked_ioctl = lttng_ioctl,
 174 #ifdef CONFIG_COMPAT
 175         .compat_ioctl = lttng_ioctl,
 176 #endif
 177 };
 178
 179 /*
 180  * We tolerate no failure in this function (if one happens, we print a dmesg
 181  * error, but cannot return any error, because the channel information is
 182  * invariant.
 183  */
 184 static
 185 void lttng_metadata_create_events(struct file *channel_file)
 186 {
 187         struct ltt_channel *channel = channel_file->private_data;
 188         static struct lttng_kernel_event metadata_params = {
 189                 .instrumentation = LTTNG_KERNEL_TRACEPOINT,
 190                 .name = "lttng_metadata",
 191         };
 192         struct ltt_event *event;
 193         int ret;
 194
 195         /*
 196          * We tolerate no failure path after event creation. It will stay
 197          * invariant for the rest of the session.
 198          */
 199         event = ltt_event_create(channel, &metadata_params, NULL);
 200         if (!event) {
 201                 ret = -EINVAL;
 202                 goto create_error;
 203         }
 204         return;
 205
 206 create_error:
 207         WARN_ON(1);
 208         return;         /* not allowed to return error */
 209 }
 210
 211 static
 212 int lttng_abi_create_channel(struct file *session_file,
 213                              struct lttng_kernel_channel __user *uchan_param,
 214                              enum channel_type channel_type)
 215 {
 216         struct ltt_session *session = session_file->private_data;
 217         const struct file_operations *fops;
 218         const char *transport_name;
 219         struct ltt_channel *chan;
 220         struct file *chan_file;
 221         struct lttng_kernel_channel chan_param;
 222         int chan_fd;
 223         int ret = 0;
 224
 225         if (copy_from_user(&chan_param, uchan_param, sizeof(chan_param)))
 226                 return -EFAULT;
 227         chan_fd = get_unused_fd();
 228         if (chan_fd < 0) {
 229                 ret = chan_fd;
 230                 goto fd_error;
 231         }
 232         chan_file = anon_inode_getfile("[lttng_channel]",
 233                                        &lttng_channel_fops,
 234                                        NULL, O_RDWR);
 235         if (IS_ERR(chan_file)) {
 236                 ret = PTR_ERR(chan_file);
 237                 goto file_error;
 238         }
 239         switch (channel_type) {
 240         case PER_CPU_CHANNEL:
 241                 transport_name = chan_param.overwrite ?
 242                         "relay-overwrite" : "relay-discard";
 243                 fops = &lttng_channel_fops;
 244                 break;
 245         case METADATA_CHANNEL:
 246                 transport_name = "relay-metadata";
 247                 fops = &lttng_metadata_fops;
 248                 break;
 249         default:
 250                 transport_name = "<unknown>";
 251                 break;
 252         }
 253         /*
 254          * We tolerate no failure path after channel creation. It will stay
 255          * invariant for the rest of the session.
 256          */
 257         chan = ltt_channel_create(session, transport_name, NULL,
 258                                   chan_param.subbuf_size,
 259                                   chan_param.num_subbuf,
 260                                   chan_param.switch_timer_interval,
 261                                   chan_param.read_timer_interval);
 262         if (!chan) {
 263                 ret = -EINVAL;
 264                 goto chan_error;
 265         }
 266         chan->file = chan_file;
 267         chan_file->private_data = chan;
 268         fd_install(chan_fd, chan_file);
 269         if (channel_type == METADATA_CHANNEL) {
 270                 session->metadata = chan;
 271                 lttng_metadata_create_events(chan_file);
 272         }
 273
 274         /* The channel created holds a reference on the session */
 275         atomic_long_inc(&session_file->f_count);
 276
 277         return chan_fd;
 278
 279 chan_error:
 280         fput(chan_file);
 281 file_error:
 282         put_unused_fd(chan_fd);
 283 fd_error:
 284         return ret;
 285 }
 286
 287 /**
 288  *      lttng_session_ioctl - lttng session fd ioctl
 289  *
 290  *      @file: the file
 291  *      @cmd: the command
 292  *      @arg: command arg
 293  *
 294  *      This ioctl implements lttng commands:
 295  *      LTTNG_KERNEL_CHANNEL
 296  *              Returns a LTTng channel file descriptor
 297  *
 298  * The returned channel will be deleted when its file descriptor is closed.
 299  */
 300 static
 301 long lttng_session_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 302 {
 303         struct ltt_session *session = file->private_data;
 304
 305         switch (cmd) {
 306         case LTTNG_KERNEL_CHANNEL:
 307                 return lttng_abi_create_channel(file,
 308                                 (struct lttng_kernel_channel __user *) arg,
 309                                 PER_CPU_CHANNEL);
 310         case LTTNG_KERNEL_SESSION_START:
 311                 return ltt_session_start(session);
 312         case LTTNG_KERNEL_SESSION_STOP:
 313                 return ltt_session_stop(session);
 314         case LTTNG_KERNEL_METADATA:
 315                 return lttng_abi_create_channel(file,
 316                                 (struct lttng_kernel_channel __user *) arg,
 317                                 METADATA_CHANNEL);
 318         default:
 319                 return -ENOIOCTLCMD;
 320         }
 321 }
 322
 323 /*
 324  * Called when the last file reference is dropped.
 325  *
 326  * Big fat note: channels and events are invariant for the whole session after
 327  * their creation. So this session destruction also destroys all channel and
 328  * event structures specific to this session (they are not destroyed when their
 329  * individual file is released).
 330  */
 331 static
 332 int lttng_session_release(struct inode *inode, struct file *file)
 333 {
 334         struct ltt_session *session = file->private_data;
 335
 336         if (session)
 337                 ltt_session_destroy(session);
 338         return 0;
 339 }
 340
 341 static const struct file_operations lttng_session_fops = {
 342         .release = lttng_session_release,
 343         .unlocked_ioctl = lttng_session_ioctl,
 344 #ifdef CONFIG_COMPAT
 345         .compat_ioctl = lttng_session_ioctl,
 346 #endif
 347 };
 348
 349 static
 350 int lttng_abi_open_stream(struct file *channel_file)
 351 {
 352         struct ltt_channel *channel = channel_file->private_data;
 353         struct lib_ring_buffer *buf;
 354         int stream_fd, ret;
 355         struct file *stream_file;
 356
 357         buf = channel->ops->buffer_read_open(channel->chan);
 358         if (!buf)
 359                 return -ENOENT;
 360
 361         stream_fd = get_unused_fd();
 362         if (stream_fd < 0) {
 363                 ret = stream_fd;
 364                 goto fd_error;
 365         }
 366         stream_file = anon_inode_getfile("[lttng_stream]",
 367                                          &lib_ring_buffer_file_operations,
 368                                          buf, O_RDWR);
 369         if (IS_ERR(stream_file)) {
 370                 ret = PTR_ERR(stream_file);
 371                 goto file_error;
 372         }
 373         /*
 374          * OPEN_FMODE, called within anon_inode_getfile/alloc_file, don't honor
 375          * FMODE_LSEEK, FMODE_PREAD nor FMODE_PWRITE. We need to read from this
 376          * file descriptor, so we set FMODE_PREAD here.
 377          */
 378         stream_file->f_mode |= FMODE_PREAD;
 379         fd_install(stream_fd, stream_file);
 380         /*
 381          * The stream holds a reference to the channel within the generic ring
 382          * buffer library, so no need to hold a refcount on the channel and
 383          * session files here.
 384          */
 385         return stream_fd;
 386
 387 file_error:
 388         put_unused_fd(stream_fd);
 389 fd_error:
 390         channel->ops->buffer_read_close(buf);
 391         return ret;
 392 }
 393
 394 static
 395 int lttng_abi_create_event(struct file *channel_file,
 396                            struct lttng_kernel_event __user *uevent_param)
 397 {
 398         struct ltt_channel *channel = channel_file->private_data;
 399         struct ltt_event *event;
 400         struct lttng_kernel_event event_param;
 401         int event_fd, ret;
 402         struct file *event_file;
 403
 404         if (copy_from_user(&event_param, uevent_param, sizeof(event_param)))
 405                 return -EFAULT;
 406         event_param.name[LTTNG_SYM_NAME_LEN - 1] = '\0';
 407         switch (event_param.instrumentation) {
 408         case LTTNG_KERNEL_KPROBE:
 409                 event_param.u.kprobe.symbol_name[LTTNG_SYM_NAME_LEN - 1] = '\0';
 410                 break;
 411         case LTTNG_KERNEL_FUNCTION:
 412                 event_param.u.ftrace.symbol_name[LTTNG_SYM_NAME_LEN - 1] = '\0';
 413                 break;
 414         default:
 415                 break;
 416         }
 417         event_fd = get_unused_fd();
 418         if (event_fd < 0) {
 419                 ret = event_fd;
 420                 goto fd_error;
 421         }
 422         event_file = anon_inode_getfile("[lttng_event]",
 423                                         &lttng_event_fops,
 424                                         NULL, O_RDWR);
 425         if (IS_ERR(event_file)) {
 426                 ret = PTR_ERR(event_file);
 427                 goto file_error;
 428         }
 429         /*
 430          * We tolerate no failure path after event creation. It will stay
 431          * invariant for the rest of the session.
 432          */
 433         event = ltt_event_create(channel, &event_param, NULL);
 434         if (!event) {
 435                 ret = -EINVAL;
 436                 goto event_error;
 437         }
 438         event_file->private_data = event;
 439         fd_install(event_fd, event_file);
 440         /* The event holds a reference on the channel */
 441         atomic_long_inc(&channel_file->f_count);
 442         return event_fd;
 443
 444 event_error:
 445         fput(event_file);
 446 file_error:
 447         put_unused_fd(event_fd);
 448 fd_error:
 449         return ret;
 450 }
 451
 452 /**
 453  *      lttng_channel_ioctl - lttng syscall through ioctl
 454  *
 455  *      @file: the file
 456  *      @cmd: the command
 457  *      @arg: command arg
 458  *
 459  *      This ioctl implements lttng commands:
 460  *      LTTNG_KERNEL_STREAM
 461  *              Returns an event stream file descriptor or failure.
 462  *              (typically, one event stream records events from one CPU)
 463  *      LTTNG_KERNEL_EVENT
 464  *              Returns an event file descriptor or failure.
 465  *
 466  * Channel and event file descriptors also hold a reference on the session.
 467  */
 468 static
 469 long lttng_channel_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 470 {
 471         switch (cmd) {
 472         case LTTNG_KERNEL_STREAM:
 473                 return lttng_abi_open_stream(file);
 474         case LTTNG_KERNEL_EVENT:
 475                 return lttng_abi_create_event(file, (struct lttng_kernel_event __user *) arg);
 476         default:
 477                 return -ENOIOCTLCMD;
 478         }
 479 }
 480
 481 /**
 482  *      lttng_metadata_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  *
 492  * Channel and event file descriptors also hold a reference on the session.
 493  */
 494 static
 495 long lttng_metadata_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 496 {
 497         switch (cmd) {
 498         case LTTNG_KERNEL_STREAM:
 499                 return lttng_abi_open_stream(file);
 500         default:
 501                 return -ENOIOCTLCMD;
 502         }
 503 }
 504
 505 /* TODO: poll */
 506 #if 0
 507 /**
 508  *      lttng_channel_poll - lttng stream addition/removal monitoring
 509  *
 510  *      @file: the file
 511  *      @wait: poll table
 512  */
 513 unsigned int lttng_channel_poll(struct file *file, poll_table *wait)
 514 {
 515         struct ltt_channel *channel = file->private_data;
 516         unsigned int mask = 0;
 517
 518         if (file->f_mode & FMODE_READ) {
 519                 poll_wait_set_exclusive(wait);
 520                 poll_wait(file, &channel->notify_wait, wait);
 521
 522                 /* TODO: identify when the channel is being finalized. */
 523                 if (finalized)
 524                         return POLLHUP;
 525                 else
 526                         return POLLIN | POLLRDNORM;
 527         }
 528         return mask;
 529
 530 }
 531 #endif //0
 532
 533 static
 534 int lttng_channel_release(struct inode *inode, struct file *file)
 535 {
 536         struct ltt_channel *channel = file->private_data;
 537
 538         if (channel)
 539                 fput(channel->session->file);
 540         return 0;
 541 }
 542
 543 static const struct file_operations lttng_channel_fops = {
 544         .release = lttng_channel_release,
 545 /* TODO */
 546 #if 0
 547         .poll = lttng_channel_poll,
 548 #endif //0
 549         .unlocked_ioctl = lttng_channel_ioctl,
 550 #ifdef CONFIG_COMPAT
 551         .compat_ioctl = lttng_channel_ioctl,
 552 #endif
 553 };
 554
 555 static const struct file_operations lttng_metadata_fops = {
 556         .release = lttng_channel_release,
 557         .unlocked_ioctl = lttng_metadata_ioctl,
 558 #ifdef CONFIG_COMPAT
 559         .compat_ioctl = lttng_metadata_ioctl,
 560 #endif
 561 };
 562
 563 static
 564 int lttng_event_release(struct inode *inode, struct file *file)
 565 {
 566         struct ltt_event *event = file->private_data;
 567
 568         if (event)
 569                 fput(event->chan->file);
 570         return 0;
 571 }
 572
 573 /* TODO: filter control ioctl */
 574 static const struct file_operations lttng_event_fops = {
 575         .release = lttng_event_release,
 576 };
 577
 578 int __init ltt_debugfs_abi_init(void)
 579 {
 580         int ret = 0;
 581
 582         wrapper_vmalloc_sync_all();
 583         lttng_dentry = debugfs_create_file("lttng", S_IWUSR, NULL, NULL,
 584                                            &lttng_fops);
 585         if (IS_ERR(lttng_dentry) || !lttng_dentry) {
 586                 printk(KERN_ERR "Error creating LTTng control file\n");
 587                 ret = -ENOMEM;
 588                 goto error;
 589         }
 590 error:
 591         return ret;
 592 }
 593
 594 void __exit ltt_debugfs_abi_exit(void)
 595 {
 596         debugfs_remove(lttng_dentry);
 597 }