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
  36 /*
  37  * This is LTTng's own personal way to create a system call as an external
  38  * module. We use ioctl() on /sys/kernel/debug/lttng.
  39  */
  40
  41 static struct dentry *lttng_dentry;
  42 static const struct file_operations lttng_fops;
  43 static const struct file_operations lttng_session_fops;
  44 static const struct file_operations lttng_channel_fops;
  45 static const struct file_operations lttng_metadata_fops;
  46 static const struct file_operations lttng_event_fops;
  47
  48 enum channel_type {
  49         PER_CPU_CHANNEL,
  50         METADATA_CHANNEL,
  51 };
  52
  53 static
  54 int lttng_abi_create_session(void)
  55 {
  56         struct ltt_session *session;
  57         struct file *session_file;
  58         int session_fd, ret;
  59
  60         session = ltt_session_create();
  61         if (!session)
  62                 return -ENOMEM;
  63         session_fd = get_unused_fd();
  64         if (session_fd < 0) {
  65                 ret = session_fd;
  66                 goto fd_error;
  67         }
  68         session_file = anon_inode_getfile("[lttng_session]",
  69                                           &lttng_session_fops,
  70                                           session, O_RDWR);
  71         if (IS_ERR(session_file)) {
  72                 ret = PTR_ERR(session_file);
  73                 goto file_error;
  74         }
  75         session->file = session_file;
  76         fd_install(session_fd, session_file);
  77         return session_fd;
  78
  79 file_error:
  80         put_unused_fd(session_fd);
  81 fd_error:
  82         ltt_session_destroy(session);
  83         return ret;
  84 }
  85
  86 /**
  87  *      lttng_ioctl - lttng syscall through ioctl
  88  *
  89  *      @file: the file
  90  *      @cmd: the command
  91  *      @arg: command arg
  92  *
  93  *      This ioctl implements lttng commands:
  94  *      LTTNG_SESSION
  95  *              Returns a LTTng trace session file descriptor
  96  *
  97  * The returned session will be deleted when its file descriptor is closed.
  98  */
  99 static
 100 long lttng_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 101 {
 102         switch (cmd) {
 103         case LTTNG_SESSION:
 104                 return lttng_abi_create_session();
 105         default:
 106                 return -ENOIOCTLCMD;
 107         }
 108 }
 109
 110 static const struct file_operations lttng_fops = {
 111         .unlocked_ioctl = lttng_ioctl,
 112 #ifdef CONFIG_COMPAT
 113         .compat_ioctl = lttng_ioctl,
 114 #endif
 115 };
 116
 117 /*
 118  * We tolerate no failure in this function (if one happens, we print a dmesg
 119  * error, but cannot return any error, because the channel information is
 120  * invariant.
 121  */
 122 static
 123 void lttng_metadata_create_events(struct file *channel_file)
 124 {
 125         struct ltt_channel *channel = channel_file->private_data;
 126         char *event_name = "lttng_metadata";
 127         const struct lttng_event_desc *event_desc;
 128         struct ltt_event *event;
 129         int ret;
 130
 131         event_desc = ltt_event_get(event_name);
 132         if (!event_desc) {
 133                 ret = -ENOENT;
 134                 goto get_error;
 135         }
 136         /*
 137          * We tolerate no failure path after event creation. It will stay
 138          * invariant for the rest of the session.
 139          */
 140         event = ltt_event_create(channel, event_name, INSTRUM_TRACEPOINTS,
 141                                  event_desc, NULL);
 142         if (!event) {
 143                 goto create_error;
 144                 ret = -EEXIST;
 145         }
 146         return;
 147
 148 create_error:
 149         ltt_event_put(event_desc);
 150 get_error:
 151         WARN_ON(1);
 152         return;         /* not allowed to return error */
 153 }
 154
 155 static
 156 int lttng_abi_create_channel(struct file *session_file,
 157                              struct lttng_channel __user *uchan_param,
 158                              enum channel_type channel_type)
 159 {
 160         struct ltt_session *session = session_file->private_data;
 161         const struct file_operations *fops;
 162         const char *transport_name;
 163         struct ltt_channel *chan;
 164         struct file *chan_file;
 165         struct lttng_channel chan_param;
 166         int chan_fd;
 167         int ret = 0;
 168
 169         if (copy_from_user(&chan_param, uchan_param, sizeof(chan_param)))
 170                 return -EFAULT;
 171         chan_fd = get_unused_fd();
 172         if (chan_fd < 0) {
 173                 ret = chan_fd;
 174                 goto fd_error;
 175         }
 176         chan_file = anon_inode_getfile("[lttng_channel]",
 177                                        &lttng_channel_fops,
 178                                        NULL, O_RDWR);
 179         if (IS_ERR(chan_file)) {
 180                 ret = PTR_ERR(chan_file);
 181                 goto file_error;
 182         }
 183         switch (channel_type) {
 184         case PER_CPU_CHANNEL:
 185                 transport_name = chan_param.overwrite ?
 186                         "relay-overwrite" : "relay-discard";
 187                 fops = &lttng_channel_fops;
 188                 break;
 189         case METADATA_CHANNEL:
 190                 transport_name = "relay-metadata";
 191                 fops = &lttng_metadata_fops;
 192                 break;
 193         default:
 194                 transport_name = "<unknown>";
 195                 break;
 196         }
 197         /*
 198          * We tolerate no failure path after channel creation. It will stay
 199          * invariant for the rest of the session.
 200          */
 201         chan = ltt_channel_create(session, transport_name, NULL,
 202                                   chan_param.subbuf_size,
 203                                   chan_param.num_subbuf,
 204                                   chan_param.switch_timer_interval,
 205                                   chan_param.read_timer_interval);
 206         if (!chan) {
 207                 ret = -EINVAL;
 208                 goto chan_error;
 209         }
 210         chan->file = chan_file;
 211         chan_file->private_data = chan;
 212         fd_install(chan_fd, chan_file);
 213         if (channel_type == METADATA_CHANNEL) {
 214                 lttng_metadata_create_events(chan_file);
 215                 session->metadata = chan;
 216         }
 217
 218         /* The channel created holds a reference on the session */
 219         atomic_long_inc(&session_file->f_count);
 220
 221         return chan_fd;
 222
 223 chan_error:
 224         fput(chan_file);
 225 file_error:
 226         put_unused_fd(chan_fd);
 227 fd_error:
 228         return ret;
 229 }
 230
 231 /**
 232  *      lttng_session_ioctl - lttng session fd ioctl
 233  *
 234  *      @file: the file
 235  *      @cmd: the command
 236  *      @arg: command arg
 237  *
 238  *      This ioctl implements lttng commands:
 239  *      LTTNG_CHANNEL
 240  *              Returns a LTTng channel file descriptor
 241  *
 242  * The returned channel will be deleted when its file descriptor is closed.
 243  */
 244 static
 245 long lttng_session_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 246 {
 247         struct ltt_session *session = file->private_data;
 248
 249         switch (cmd) {
 250         case LTTNG_CHANNEL:
 251                 return lttng_abi_create_channel(file,
 252                                 (struct lttng_channel __user *)arg,
 253                                 PER_CPU_CHANNEL);
 254         case LTTNG_SESSION_START:
 255                 return ltt_session_start(session);
 256         case LTTNG_SESSION_STOP:
 257                 return ltt_session_stop(session);
 258         case LTTNG_METADATA:
 259                 return lttng_abi_create_channel(file,
 260                                 (struct lttng_channel __user *)arg,
 261                                 METADATA_CHANNEL);
 262         default:
 263                 return -ENOIOCTLCMD;
 264         }
 265 }
 266
 267 /*
 268  * Called when the last file reference is dropped.
 269  *
 270  * Big fat note: channels and events are invariant for the whole session after
 271  * their creation. So this session destruction also destroys all channel and
 272  * event structures specific to this session (they are not destroyed when their
 273  * individual file is released).
 274  */
 275 static
 276 int lttng_session_release(struct inode *inode, struct file *file)
 277 {
 278         struct ltt_session *session = file->private_data;
 279
 280         if (session)
 281                 ltt_session_destroy(session);
 282         return 0;
 283 }
 284
 285 static const struct file_operations lttng_session_fops = {
 286         .release = lttng_session_release,
 287         .unlocked_ioctl = lttng_session_ioctl,
 288 #ifdef CONFIG_COMPAT
 289         .compat_ioctl = lttng_session_ioctl,
 290 #endif
 291 };
 292
 293 static
 294 int lttng_abi_open_stream(struct file *channel_file)
 295 {
 296         struct ltt_channel *channel = channel_file->private_data;
 297         struct lib_ring_buffer *buf;
 298         int stream_fd, ret;
 299         struct file *stream_file;
 300
 301         buf = channel->ops->buffer_read_open(channel->chan);
 302         if (!buf)
 303                 return -ENOENT;
 304
 305         stream_fd = get_unused_fd();
 306         if (stream_fd < 0) {
 307                 ret = stream_fd;
 308                 goto fd_error;
 309         }
 310         stream_file = anon_inode_getfile("[lttng_stream]",
 311                                          &lib_ring_buffer_file_operations,
 312                                          buf, O_RDWR);
 313         if (IS_ERR(stream_file)) {
 314                 ret = PTR_ERR(stream_file);
 315                 goto file_error;
 316         }
 317         /*
 318          * OPEN_FMODE, called within anon_inode_getfile/alloc_file, don't honor
 319          * FMODE_LSEEK, FMODE_PREAD nor FMODE_PWRITE. We need to read from this
 320          * file descriptor, so we set FMODE_PREAD here.
 321          */
 322         stream_file->f_mode |= FMODE_PREAD;
 323         fd_install(stream_fd, stream_file);
 324         /*
 325          * The stream holds a reference to the channel within the generic ring
 326          * buffer library, so no need to hold a refcount on the channel and
 327          * session files here.
 328          */
 329         return stream_fd;
 330
 331 file_error:
 332         put_unused_fd(stream_fd);
 333 fd_error:
 334         channel->ops->buffer_read_close(buf);
 335         return ret;
 336 }
 337
 338 static
 339 int lttng_abi_create_event(struct file *channel_file,
 340                            struct lttng_event __user *uevent_param)
 341 {
 342         struct ltt_channel *channel = channel_file->private_data;
 343         const struct lttng_event_desc *event_desc;
 344         struct ltt_event *event;
 345         char *event_name;
 346         struct lttng_event event_param;
 347         int event_fd, ret;
 348         struct file *event_file;
 349
 350         if (copy_from_user(&event_param, uevent_param, sizeof(event_param)))
 351                 return -EFAULT;
 352         event_name = kmalloc(PATH_MAX, GFP_KERNEL);
 353         if (!event_name)
 354                 return -ENOMEM;
 355         if (strncpy_from_user(event_name, uevent_param->name, PATH_MAX) < 0) {
 356                 ret = -EFAULT;
 357                 goto name_error;
 358         }
 359         event_name[PATH_MAX - 1] = '\0';
 360
 361         event_desc = ltt_event_get(event_name);
 362         if (!event_desc) {
 363                 ret = -ENOENT;
 364                 goto get_error;
 365         }
 366         event_fd = get_unused_fd();
 367         if (event_fd < 0) {
 368                 ret = event_fd;
 369                 goto fd_error;
 370         }
 371         event_file = anon_inode_getfile("[lttng_event]",
 372                                         &lttng_event_fops,
 373                                         NULL, O_RDWR);
 374         if (IS_ERR(event_file)) {
 375                 ret = PTR_ERR(event_file);
 376                 goto file_error;
 377         }
 378         /*
 379          * We tolerate no failure path after event creation. It will stay
 380          * invariant for the rest of the session.
 381          */
 382         event = ltt_event_create(channel, event_name, event_param.itype,
 383                                  event_desc, NULL);
 384         if (!event) {
 385                 goto event_error;
 386                 ret = -EEXIST;
 387         }
 388         event_file->private_data = event;
 389         fd_install(event_fd, event_file);
 390         /* The event holds a reference on the channel */
 391         atomic_long_inc(&channel_file->f_count);
 392         kfree(event_name);
 393         return event_fd;
 394
 395 event_error:
 396         fput(event_file);
 397 file_error:
 398         put_unused_fd(event_fd);
 399 fd_error:
 400         ltt_event_put(event_desc);
 401 get_error:
 402 name_error:
 403         kfree(event_name);
 404         return ret;
 405 }
 406
 407 /**
 408  *      lttng_channel_ioctl - lttng syscall through ioctl
 409  *
 410  *      @file: the file
 411  *      @cmd: the command
 412  *      @arg: command arg
 413  *
 414  *      This ioctl implements lttng commands:
 415  *      LTTNG_STREAM
 416  *              Returns an event stream file descriptor or failure.
 417  *              (typically, one event stream records events from one CPU)
 418  *      LTTNG_EVENT
 419  *              Returns an event file descriptor or failure.
 420  *
 421  * Channel and event file descriptors also hold a reference on the session.
 422  */
 423 static
 424 long lttng_channel_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 425 {
 426         switch (cmd) {
 427         case LTTNG_STREAM:
 428                 return lttng_abi_open_stream(file);
 429         case LTTNG_EVENT:
 430                 return lttng_abi_create_event(file, (struct lttng_event __user *)arg);
 431         default:
 432                 return -ENOIOCTLCMD;
 433         }
 434 }
 435
 436 /**
 437  *      lttng_metadata_ioctl - lttng syscall through ioctl
 438  *
 439  *      @file: the file
 440  *      @cmd: the command
 441  *      @arg: command arg
 442  *
 443  *      This ioctl implements lttng commands:
 444  *      LTTNG_STREAM
 445  *              Returns an event stream file descriptor or failure.
 446  *
 447  * Channel and event file descriptors also hold a reference on the session.
 448  */
 449 static
 450 long lttng_metadata_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 451 {
 452         switch (cmd) {
 453         case LTTNG_STREAM:
 454                 return lttng_abi_open_stream(file);
 455         default:
 456                 return -ENOIOCTLCMD;
 457         }
 458 }
 459
 460 /* TODO: poll */
 461 #if 0
 462 /**
 463  *      lttng_channel_poll - lttng stream addition/removal monitoring
 464  *
 465  *      @file: the file
 466  *      @wait: poll table
 467  */
 468 unsigned int lttng_channel_poll(struct file *file, poll_table *wait)
 469 {
 470         struct ltt_channel *channel = file->private_data;
 471         unsigned int mask = 0;
 472
 473         if (file->f_mode & FMODE_READ) {
 474                 poll_wait_set_exclusive(wait);
 475                 poll_wait(file, &channel->notify_wait, wait);
 476
 477                 /* TODO: identify when the channel is being finalized. */
 478                 if (finalized)
 479                         return POLLHUP;
 480                 else
 481                         return POLLIN | POLLRDNORM;
 482         }
 483         return mask;
 484
 485 }
 486 #endif //0
 487
 488 static
 489 int lttng_channel_release(struct inode *inode, struct file *file)
 490 {
 491         struct ltt_channel *channel = file->private_data;
 492
 493         if (channel)
 494                 fput(channel->session->file);
 495         return 0;
 496 }
 497
 498 static const struct file_operations lttng_channel_fops = {
 499         .release = lttng_channel_release,
 500 /* TODO */
 501 #if 0
 502         .poll = lttng_channel_poll,
 503 #endif //0
 504         .unlocked_ioctl = lttng_channel_ioctl,
 505 #ifdef CONFIG_COMPAT
 506         .compat_ioctl = lttng_channel_ioctl,
 507 #endif
 508 };
 509
 510 static const struct file_operations lttng_metadata_fops = {
 511         .release = lttng_channel_release,
 512         .unlocked_ioctl = lttng_metadata_ioctl,
 513 #ifdef CONFIG_COMPAT
 514         .compat_ioctl = lttng_metadata_ioctl,
 515 #endif
 516 };
 517
 518 static
 519 int lttng_event_release(struct inode *inode, struct file *file)
 520 {
 521         struct ltt_event *event = file->private_data;
 522
 523         if (event) {
 524                 ltt_event_unregister(event);
 525                 fput(event->chan->file);
 526         }
 527         return 0;
 528 }
 529
 530 /* TODO: filter control ioctl */
 531 static const struct file_operations lttng_event_fops = {
 532         .release = lttng_event_release,
 533 };
 534
 535 int __init ltt_debugfs_abi_init(void)
 536 {
 537         int ret = 0;
 538
 539         wrapper_vmalloc_sync_all();
 540         lttng_dentry = debugfs_create_file("lttng", S_IWUSR, NULL, NULL,
 541                                            &lttng_fops);
 542         if (IS_ERR(lttng_dentry) || !lttng_dentry) {
 543                 printk(KERN_ERR "Error creating LTTng control file\n");
 544                 ret = -ENOMEM;
 545                 goto error;
 546         }
 547 error:
 548         return ret;
 549 }
 550
 551 void __exit ltt_debugfs_abi_exit(void)
 552 {
 553         debugfs_remove(lttng_dentry);
 554 }