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 long lttng_abi_tracer_version(struct file *file,
  89         struct lttng_kernel_tracer_version __user *uversion_param)
  90 {
  91         struct lttng_kernel_tracer_version v;
  92
  93         v.version = LTTNG_VERSION;
  94         v.patchlevel = LTTNG_PATCHLEVEL;
  95         v.sublevel = LTTNG_SUBLEVEL;
  96
  97         if (copy_to_user(uversion_param, &v, sizeof(v)))
  98                 return -EFAULT;
  99         return 0;
 100 }
 101
 102 /**
 103  *      lttng_ioctl - lttng syscall through ioctl
 104  *
 105  *      @file: the file
 106  *      @cmd: the command
 107  *      @arg: command arg
 108  *
 109  *      This ioctl implements lttng commands:
 110  *      LTTNG_KERNEL_SESSION
 111  *              Returns a LTTng trace session file descriptor
 112  *
 113  * The returned session will be deleted when its file descriptor is closed.
 114  */
 115 static
 116 long lttng_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 117 {
 118         switch (cmd) {
 119         case LTTNG_KERNEL_SESSION:
 120                 return lttng_abi_create_session();
 121         case LTTNG_KERNEL_TRACER_VERSION:
 122                 return lttng_abi_tracer_version(file,
 123                                 (struct lttng_kernel_tracer_version __user *) arg);
 124         default:
 125                 return -ENOIOCTLCMD;
 126         }
 127 }
 128
 129 static const struct file_operations lttng_fops = {
 130         .unlocked_ioctl = lttng_ioctl,
 131 #ifdef CONFIG_COMPAT
 132         .compat_ioctl = lttng_ioctl,
 133 #endif
 134 };
 135
 136 /*
 137  * We tolerate no failure in this function (if one happens, we print a dmesg
 138  * error, but cannot return any error, because the channel information is
 139  * invariant.
 140  */
 141 static
 142 void lttng_metadata_create_events(struct file *channel_file)
 143 {
 144         struct ltt_channel *channel = channel_file->private_data;
 145         char *event_name = "lttng_metadata";
 146         const struct lttng_event_desc *event_desc;
 147         struct ltt_event *event;
 148         int ret;
 149
 150         event_desc = ltt_event_get(event_name);
 151         if (!event_desc) {
 152                 ret = -ENOENT;
 153                 goto get_error;
 154         }
 155         /*
 156          * We tolerate no failure path after event creation. It will stay
 157          * invariant for the rest of the session.
 158          */
 159         event = ltt_event_create(channel, event_name, LTTNG_KERNEL_TRACEPOINTS,
 160                                  event_desc, NULL);
 161         if (!event) {
 162                 goto create_error;
 163                 ret = -EEXIST;
 164         }
 165         return;
 166
 167 create_error:
 168         ltt_event_put(event_desc);
 169 get_error:
 170         WARN_ON(1);
 171         return;         /* not allowed to return error */
 172 }
 173
 174 static
 175 int lttng_abi_create_channel(struct file *session_file,
 176                              struct lttng_kernel_channel __user *uchan_param,
 177                              enum channel_type channel_type)
 178 {
 179         struct ltt_session *session = session_file->private_data;
 180         const struct file_operations *fops;
 181         const char *transport_name;
 182         struct ltt_channel *chan;
 183         struct file *chan_file;
 184         struct lttng_kernel_channel chan_param;
 185         int chan_fd;
 186         int ret = 0;
 187
 188         if (copy_from_user(&chan_param, uchan_param, sizeof(chan_param)))
 189                 return -EFAULT;
 190         chan_fd = get_unused_fd();
 191         if (chan_fd < 0) {
 192                 ret = chan_fd;
 193                 goto fd_error;
 194         }
 195         chan_file = anon_inode_getfile("[lttng_channel]",
 196                                        &lttng_channel_fops,
 197                                        NULL, O_RDWR);
 198         if (IS_ERR(chan_file)) {
 199                 ret = PTR_ERR(chan_file);
 200                 goto file_error;
 201         }
 202         switch (channel_type) {
 203         case PER_CPU_CHANNEL:
 204                 transport_name = chan_param.overwrite ?
 205                         "relay-overwrite" : "relay-discard";
 206                 fops = &lttng_channel_fops;
 207                 break;
 208         case METADATA_CHANNEL:
 209                 transport_name = "relay-metadata";
 210                 fops = &lttng_metadata_fops;
 211                 break;
 212         default:
 213                 transport_name = "<unknown>";
 214                 break;
 215         }
 216         /*
 217          * We tolerate no failure path after channel creation. It will stay
 218          * invariant for the rest of the session.
 219          */
 220         chan = ltt_channel_create(session, transport_name, NULL,
 221                                   chan_param.subbuf_size,
 222                                   chan_param.num_subbuf,
 223                                   chan_param.switch_timer_interval,
 224                                   chan_param.read_timer_interval);
 225         if (!chan) {
 226                 ret = -EINVAL;
 227                 goto chan_error;
 228         }
 229         chan->file = chan_file;
 230         chan_file->private_data = chan;
 231         fd_install(chan_fd, chan_file);
 232         if (channel_type == METADATA_CHANNEL) {
 233                 lttng_metadata_create_events(chan_file);
 234                 session->metadata = chan;
 235         }
 236
 237         /* The channel created holds a reference on the session */
 238         atomic_long_inc(&session_file->f_count);
 239
 240         return chan_fd;
 241
 242 chan_error:
 243         fput(chan_file);
 244 file_error:
 245         put_unused_fd(chan_fd);
 246 fd_error:
 247         return ret;
 248 }
 249
 250 /**
 251  *      lttng_session_ioctl - lttng session fd ioctl
 252  *
 253  *      @file: the file
 254  *      @cmd: the command
 255  *      @arg: command arg
 256  *
 257  *      This ioctl implements lttng commands:
 258  *      LTTNG_KERNEL_CHANNEL
 259  *              Returns a LTTng channel file descriptor
 260  *
 261  * The returned channel will be deleted when its file descriptor is closed.
 262  */
 263 static
 264 long lttng_session_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 265 {
 266         struct ltt_session *session = file->private_data;
 267
 268         switch (cmd) {
 269         case LTTNG_KERNEL_CHANNEL:
 270                 return lttng_abi_create_channel(file,
 271                                 (struct lttng_kernel_channel __user *) arg,
 272                                 PER_CPU_CHANNEL);
 273         case LTTNG_KERNEL_SESSION_START:
 274                 return ltt_session_start(session);
 275         case LTTNG_KERNEL_SESSION_STOP:
 276                 return ltt_session_stop(session);
 277         case LTTNG_KERNEL_METADATA:
 278                 return lttng_abi_create_channel(file,
 279                                 (struct lttng_kernel_channel __user *) arg,
 280                                 METADATA_CHANNEL);
 281         default:
 282                 return -ENOIOCTLCMD;
 283         }
 284 }
 285
 286 /*
 287  * Called when the last file reference is dropped.
 288  *
 289  * Big fat note: channels and events are invariant for the whole session after
 290  * their creation. So this session destruction also destroys all channel and
 291  * event structures specific to this session (they are not destroyed when their
 292  * individual file is released).
 293  */
 294 static
 295 int lttng_session_release(struct inode *inode, struct file *file)
 296 {
 297         struct ltt_session *session = file->private_data;
 298
 299         if (session)
 300                 ltt_session_destroy(session);
 301         return 0;
 302 }
 303
 304 static const struct file_operations lttng_session_fops = {
 305         .release = lttng_session_release,
 306         .unlocked_ioctl = lttng_session_ioctl,
 307 #ifdef CONFIG_COMPAT
 308         .compat_ioctl = lttng_session_ioctl,
 309 #endif
 310 };
 311
 312 static
 313 int lttng_abi_open_stream(struct file *channel_file)
 314 {
 315         struct ltt_channel *channel = channel_file->private_data;
 316         struct lib_ring_buffer *buf;
 317         int stream_fd, ret;
 318         struct file *stream_file;
 319
 320         buf = channel->ops->buffer_read_open(channel->chan);
 321         if (!buf)
 322                 return -ENOENT;
 323
 324         stream_fd = get_unused_fd();
 325         if (stream_fd < 0) {
 326                 ret = stream_fd;
 327                 goto fd_error;
 328         }
 329         stream_file = anon_inode_getfile("[lttng_stream]",
 330                                          &lib_ring_buffer_file_operations,
 331                                          buf, O_RDWR);
 332         if (IS_ERR(stream_file)) {
 333                 ret = PTR_ERR(stream_file);
 334                 goto file_error;
 335         }
 336         /*
 337          * OPEN_FMODE, called within anon_inode_getfile/alloc_file, don't honor
 338          * FMODE_LSEEK, FMODE_PREAD nor FMODE_PWRITE. We need to read from this
 339          * file descriptor, so we set FMODE_PREAD here.
 340          */
 341         stream_file->f_mode |= FMODE_PREAD;
 342         fd_install(stream_fd, stream_file);
 343         /*
 344          * The stream holds a reference to the channel within the generic ring
 345          * buffer library, so no need to hold a refcount on the channel and
 346          * session files here.
 347          */
 348         return stream_fd;
 349
 350 file_error:
 351         put_unused_fd(stream_fd);
 352 fd_error:
 353         channel->ops->buffer_read_close(buf);
 354         return ret;
 355 }
 356
 357 static
 358 int lttng_abi_create_event(struct file *channel_file,
 359                            struct lttng_kernel_event __user *uevent_param)
 360 {
 361         struct ltt_channel *channel = channel_file->private_data;
 362         const struct lttng_event_desc *event_desc;
 363         struct ltt_event *event;
 364         char *event_name;
 365         struct lttng_kernel_event event_param;
 366         int event_fd, ret;
 367         struct file *event_file;
 368
 369         if (copy_from_user(&event_param, uevent_param, sizeof(event_param)))
 370                 return -EFAULT;
 371         event_name = kmalloc(PATH_MAX, GFP_KERNEL);
 372         if (!event_name)
 373                 return -ENOMEM;
 374         if (strncpy_from_user(event_name, uevent_param->name, PATH_MAX) < 0) {
 375                 ret = -EFAULT;
 376                 goto name_error;
 377         }
 378         event_name[PATH_MAX - 1] = '\0';
 379
 380         event_desc = ltt_event_get(event_name);
 381         if (!event_desc) {
 382                 ret = -ENOENT;
 383                 goto get_error;
 384         }
 385         event_fd = get_unused_fd();
 386         if (event_fd < 0) {
 387                 ret = event_fd;
 388                 goto fd_error;
 389         }
 390         event_file = anon_inode_getfile("[lttng_event]",
 391                                         &lttng_event_fops,
 392                                         NULL, O_RDWR);
 393         if (IS_ERR(event_file)) {
 394                 ret = PTR_ERR(event_file);
 395                 goto file_error;
 396         }
 397         /*
 398          * We tolerate no failure path after event creation. It will stay
 399          * invariant for the rest of the session.
 400          */
 401         event = ltt_event_create(channel, event_name, event_param.instrumentation,
 402                                  event_desc, NULL);
 403         if (!event) {
 404                 goto event_error;
 405                 ret = -EEXIST;
 406         }
 407         event_file->private_data = event;
 408         fd_install(event_fd, event_file);
 409         /* The event holds a reference on the channel */
 410         atomic_long_inc(&channel_file->f_count);
 411         kfree(event_name);
 412         return event_fd;
 413
 414 event_error:
 415         fput(event_file);
 416 file_error:
 417         put_unused_fd(event_fd);
 418 fd_error:
 419         ltt_event_put(event_desc);
 420 get_error:
 421 name_error:
 422         kfree(event_name);
 423         return ret;
 424 }
 425
 426 /**
 427  *      lttng_channel_ioctl - lttng syscall through ioctl
 428  *
 429  *      @file: the file
 430  *      @cmd: the command
 431  *      @arg: command arg
 432  *
 433  *      This ioctl implements lttng commands:
 434  *      LTTNG_KERNEL_STREAM
 435  *              Returns an event stream file descriptor or failure.
 436  *              (typically, one event stream records events from one CPU)
 437  *      LTTNG_KERNEL_EVENT
 438  *              Returns an event file descriptor or failure.
 439  *
 440  * Channel and event file descriptors also hold a reference on the session.
 441  */
 442 static
 443 long lttng_channel_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 444 {
 445         switch (cmd) {
 446         case LTTNG_KERNEL_STREAM:
 447                 return lttng_abi_open_stream(file);
 448         case LTTNG_KERNEL_EVENT:
 449                 return lttng_abi_create_event(file, (struct lttng_kernel_event __user *) arg);
 450         default:
 451                 return -ENOIOCTLCMD;
 452         }
 453 }
 454
 455 /**
 456  *      lttng_metadata_ioctl - lttng syscall through ioctl
 457  *
 458  *      @file: the file
 459  *      @cmd: the command
 460  *      @arg: command arg
 461  *
 462  *      This ioctl implements lttng commands:
 463  *      LTTNG_KERNEL_STREAM
 464  *              Returns an event stream file descriptor or failure.
 465  *
 466  * Channel and event file descriptors also hold a reference on the session.
 467  */
 468 static
 469 long lttng_metadata_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         default:
 475                 return -ENOIOCTLCMD;
 476         }
 477 }
 478
 479 /* TODO: poll */
 480 #if 0
 481 /**
 482  *      lttng_channel_poll - lttng stream addition/removal monitoring
 483  *
 484  *      @file: the file
 485  *      @wait: poll table
 486  */
 487 unsigned int lttng_channel_poll(struct file *file, poll_table *wait)
 488 {
 489         struct ltt_channel *channel = file->private_data;
 490         unsigned int mask = 0;
 491
 492         if (file->f_mode & FMODE_READ) {
 493                 poll_wait_set_exclusive(wait);
 494                 poll_wait(file, &channel->notify_wait, wait);
 495
 496                 /* TODO: identify when the channel is being finalized. */
 497                 if (finalized)
 498                         return POLLHUP;
 499                 else
 500                         return POLLIN | POLLRDNORM;
 501         }
 502         return mask;
 503
 504 }
 505 #endif //0
 506
 507 static
 508 int lttng_channel_release(struct inode *inode, struct file *file)
 509 {
 510         struct ltt_channel *channel = file->private_data;
 511
 512         if (channel)
 513                 fput(channel->session->file);
 514         return 0;
 515 }
 516
 517 static const struct file_operations lttng_channel_fops = {
 518         .release = lttng_channel_release,
 519 /* TODO */
 520 #if 0
 521         .poll = lttng_channel_poll,
 522 #endif //0
 523         .unlocked_ioctl = lttng_channel_ioctl,
 524 #ifdef CONFIG_COMPAT
 525         .compat_ioctl = lttng_channel_ioctl,
 526 #endif
 527 };
 528
 529 static const struct file_operations lttng_metadata_fops = {
 530         .release = lttng_channel_release,
 531         .unlocked_ioctl = lttng_metadata_ioctl,
 532 #ifdef CONFIG_COMPAT
 533         .compat_ioctl = lttng_metadata_ioctl,
 534 #endif
 535 };
 536
 537 static
 538 int lttng_event_release(struct inode *inode, struct file *file)
 539 {
 540         struct ltt_event *event = file->private_data;
 541
 542         if (event) {
 543                 ltt_event_unregister(event);
 544                 fput(event->chan->file);
 545         }
 546         return 0;
 547 }
 548
 549 /* TODO: filter control ioctl */
 550 static const struct file_operations lttng_event_fops = {
 551         .release = lttng_event_release,
 552 };
 553
 554 int __init ltt_debugfs_abi_init(void)
 555 {
 556         int ret = 0;
 557
 558         wrapper_vmalloc_sync_all();
 559         lttng_dentry = debugfs_create_file("lttng", S_IWUSR, NULL, NULL,
 560                                            &lttng_fops);
 561         if (IS_ERR(lttng_dentry) || !lttng_dentry) {
 562                 printk(KERN_ERR "Error creating LTTng control file\n");
 563                 ret = -ENOMEM;
 564                 goto error;
 565         }
 566 error:
 567         return ret;
 568 }
 569
 570 void __exit ltt_debugfs_abi_exit(void)
 571 {
 572         debugfs_remove(lttng_dentry);
 573 }