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         struct ltt_event *event;
 128         int ret;
 129         void *probe;
 130
 131         probe = ltt_probe_get(event_name);
 132         if (!probe) {
 133                 ret = -ENOENT;
 134                 goto probe_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                                  probe, NULL);
 142         if (!event) {
 143                 goto event_error;
 144                 ret = -EEXIST;
 145         }
 146         return;
 147
 148 event_error:
 149         ltt_probe_put(probe);
 150 probe_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
 216         /* The channel created holds a reference on the session */
 217         atomic_long_inc(&session_file->f_count);
 218
 219         return chan_fd;
 220
 221 chan_error:
 222         fput(chan_file);
 223 file_error:
 224         put_unused_fd(chan_fd);
 225 fd_error:
 226         return ret;
 227 }
 228
 229 /**
 230  *      lttng_session_ioctl - lttng session fd ioctl
 231  *
 232  *      @file: the file
 233  *      @cmd: the command
 234  *      @arg: command arg
 235  *
 236  *      This ioctl implements lttng commands:
 237  *      LTTNG_CHANNEL
 238  *              Returns a LTTng channel file descriptor
 239  *
 240  * The returned channel will be deleted when its file descriptor is closed.
 241  */
 242 static
 243 long lttng_session_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 244 {
 245         struct ltt_session *session = file->private_data;
 246
 247         switch (cmd) {
 248         case LTTNG_CHANNEL:
 249                 return lttng_abi_create_channel(file,
 250                                 (struct lttng_channel __user *)arg,
 251                                 PER_CPU_CHANNEL);
 252         case LTTNG_SESSION_START:
 253                 return ltt_session_start(session);
 254         case LTTNG_SESSION_STOP:
 255                 return ltt_session_stop(session);
 256         case LTTNG_METADATA:
 257                 return lttng_abi_create_channel(file,
 258                                 (struct lttng_channel __user *)arg,
 259                                 METADATA_CHANNEL);
 260         default:
 261                 return -ENOIOCTLCMD;
 262         }
 263 }
 264
 265 /*
 266  * Called when the last file reference is dropped.
 267  *
 268  * Big fat note: channels and events are invariant for the whole session after
 269  * their creation. So this session destruction also destroys all channel and
 270  * event structures specific to this session (they are not destroyed when their
 271  * individual file is released).
 272  */
 273 static
 274 int lttng_session_release(struct inode *inode, struct file *file)
 275 {
 276         struct ltt_session *session = file->private_data;
 277
 278         if (session)
 279                 ltt_session_destroy(session);
 280         return 0;
 281 }
 282
 283 static const struct file_operations lttng_session_fops = {
 284         .release = lttng_session_release,
 285         .unlocked_ioctl = lttng_session_ioctl,
 286 #ifdef CONFIG_COMPAT
 287         .compat_ioctl = lttng_session_ioctl,
 288 #endif
 289 };
 290
 291 static
 292 int lttng_abi_open_stream(struct file *channel_file)
 293 {
 294         struct ltt_channel *channel = channel_file->private_data;
 295         struct lib_ring_buffer *buf;
 296         int stream_fd, ret;
 297         struct file *stream_file;
 298
 299         buf = channel->ops->buffer_read_open(channel->chan);
 300         if (!buf)
 301                 return -ENOENT;
 302
 303         stream_fd = get_unused_fd();
 304         if (stream_fd < 0) {
 305                 ret = stream_fd;
 306                 goto fd_error;
 307         }
 308         stream_file = anon_inode_getfile("[lttng_stream]",
 309                                          &lib_ring_buffer_file_operations,
 310                                          buf, O_RDWR);
 311         if (IS_ERR(stream_file)) {
 312                 ret = PTR_ERR(stream_file);
 313                 goto file_error;
 314         }
 315         /*
 316          * OPEN_FMODE, called within anon_inode_getfile/alloc_file, don't honor
 317          * FMODE_LSEEK, FMODE_PREAD nor FMODE_PWRITE. We need to read from this
 318          * file descriptor, so we set FMODE_PREAD here.
 319          */
 320         stream_file->f_mode |= FMODE_PREAD;
 321         fd_install(stream_fd, stream_file);
 322         /*
 323          * The stream holds a reference to the channel within the generic ring
 324          * buffer library, so no need to hold a refcount on the channel and
 325          * session files here.
 326          */
 327         return stream_fd;
 328
 329 file_error:
 330         put_unused_fd(stream_fd);
 331 fd_error:
 332         channel->ops->buffer_read_close(buf);
 333         return ret;
 334 }
 335
 336 static
 337 int lttng_abi_create_event(struct file *channel_file,
 338                            struct lttng_event __user *uevent_param)
 339 {
 340         struct ltt_channel *channel = channel_file->private_data;
 341         struct ltt_event *event;
 342         char *event_name;
 343         struct lttng_event event_param;
 344         int event_fd, ret;
 345         struct file *event_file;
 346         void *probe;
 347
 348         if (copy_from_user(&event_param, uevent_param, sizeof(event_param)))
 349                 return -EFAULT;
 350         event_name = kmalloc(PATH_MAX, GFP_KERNEL);
 351         if (!event_name)
 352                 return -ENOMEM;
 353         if (strncpy_from_user(event_name, uevent_param->name, PATH_MAX) < 0) {
 354                 ret = -EFAULT;
 355                 goto name_error;
 356         }
 357         event_name[PATH_MAX - 1] = '\0';
 358
 359         probe = ltt_probe_get(event_name);
 360         if (!probe) {
 361                 ret = -ENOENT;
 362                 goto probe_error;
 363         }
 364         event_fd = get_unused_fd();
 365         if (event_fd < 0) {
 366                 ret = event_fd;
 367                 goto fd_error;
 368         }
 369         event_file = anon_inode_getfile("[lttng_event]",
 370                                         &lttng_event_fops,
 371                                         NULL, O_RDWR);
 372         if (IS_ERR(event_file)) {
 373                 ret = PTR_ERR(event_file);
 374                 goto file_error;
 375         }
 376         /*
 377          * We tolerate no failure path after event creation. It will stay
 378          * invariant for the rest of the session.
 379          */
 380         event = ltt_event_create(channel, event_name, event_param.itype,
 381                                  probe, NULL);
 382         if (!event) {
 383                 goto event_error;
 384                 ret = -EEXIST;
 385         }
 386         event_file->private_data = event;
 387         fd_install(event_fd, event_file);
 388         /* The event holds a reference on the channel */
 389         atomic_long_inc(&channel_file->f_count);
 390         kfree(event_name);
 391         return event_fd;
 392
 393 event_error:
 394         fput(event_file);
 395 file_error:
 396         put_unused_fd(event_fd);
 397 fd_error:
 398         ltt_probe_put(probe);
 399 probe_error:
 400 name_error:
 401         kfree(event_name);
 402         return ret;
 403 }
 404
 405 /**
 406  *      lttng_channel_ioctl - lttng syscall through ioctl
 407  *
 408  *      @file: the file
 409  *      @cmd: the command
 410  *      @arg: command arg
 411  *
 412  *      This ioctl implements lttng commands:
 413  *      LTTNG_STREAM
 414  *              Returns an event stream file descriptor or failure.
 415  *              (typically, one event stream records events from one CPU)
 416  *      LTTNG_EVENT
 417  *              Returns an event file descriptor or failure.
 418  *
 419  * Channel and event file descriptors also hold a reference on the session.
 420  */
 421 static
 422 long lttng_channel_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 423 {
 424         switch (cmd) {
 425         case LTTNG_STREAM:
 426                 return lttng_abi_open_stream(file);
 427         case LTTNG_EVENT:
 428                 return lttng_abi_create_event(file, (struct lttng_event __user *)arg);
 429         default:
 430                 return -ENOIOCTLCMD;
 431         }
 432 }
 433
 434 /**
 435  *      lttng_metadata_ioctl - lttng syscall through ioctl
 436  *
 437  *      @file: the file
 438  *      @cmd: the command
 439  *      @arg: command arg
 440  *
 441  *      This ioctl implements lttng commands:
 442  *      LTTNG_STREAM
 443  *              Returns an event stream file descriptor or failure.
 444  *
 445  * Channel and event file descriptors also hold a reference on the session.
 446  */
 447 static
 448 long lttng_metadata_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 449 {
 450         switch (cmd) {
 451         case LTTNG_STREAM:
 452                 return lttng_abi_open_stream(file);
 453         default:
 454                 return -ENOIOCTLCMD;
 455         }
 456 }
 457
 458 /* TODO: poll */
 459 #if 0
 460 /**
 461  *      lttng_channel_poll - lttng stream addition/removal monitoring
 462  *
 463  *      @file: the file
 464  *      @wait: poll table
 465  */
 466 unsigned int lttng_channel_poll(struct file *file, poll_table *wait)
 467 {
 468         struct ltt_channel *channel = file->private_data;
 469         unsigned int mask = 0;
 470
 471         if (file->f_mode & FMODE_READ) {
 472                 poll_wait_set_exclusive(wait);
 473                 poll_wait(file, &channel->notify_wait, wait);
 474
 475                 /* TODO: identify when the channel is being finalized. */
 476                 if (finalized)
 477                         return POLLHUP;
 478                 else
 479                         return POLLIN | POLLRDNORM;
 480         }
 481         return mask;
 482
 483 }
 484 #endif //0
 485
 486 static
 487 int lttng_channel_release(struct inode *inode, struct file *file)
 488 {
 489         struct ltt_channel *channel = file->private_data;
 490
 491         if (channel)
 492                 fput(channel->session->file);
 493         return 0;
 494 }
 495
 496 static const struct file_operations lttng_channel_fops = {
 497         .release = lttng_channel_release,
 498 /* TODO */
 499 #if 0
 500         .poll = lttng_channel_poll,
 501 #endif //0
 502         .unlocked_ioctl = lttng_channel_ioctl,
 503 #ifdef CONFIG_COMPAT
 504         .compat_ioctl = lttng_channel_ioctl,
 505 #endif
 506 };
 507
 508 static const struct file_operations lttng_metadata_fops = {
 509         .release = lttng_channel_release,
 510         .unlocked_ioctl = lttng_metadata_ioctl,
 511 #ifdef CONFIG_COMPAT
 512         .compat_ioctl = lttng_metadata_ioctl,
 513 #endif
 514 };
 515
 516 static
 517 int lttng_event_release(struct inode *inode, struct file *file)
 518 {
 519         struct ltt_event *event = file->private_data;
 520
 521         if (event)
 522                 fput(event->chan->file);
 523         return 0;
 524 }
 525
 526 /* TODO: filter control ioctl */
 527 static const struct file_operations lttng_event_fops = {
 528         .release = lttng_event_release,
 529 };
 530
 531 int __init ltt_debugfs_abi_init(void)
 532 {
 533         int ret = 0;
 534
 535         wrapper_vmalloc_sync_all();
 536         lttng_dentry = debugfs_create_file("lttng", S_IWUSR, NULL, NULL,
 537                                            &lttng_fops);
 538         if (IS_ERR(lttng_dentry) || !lttng_dentry) {
 539                 printk(KERN_ERR "Error creating LTTng control file\n");
 540                 ret = -ENOMEM;
 541                 goto error;
 542         }
 543 error:
 544         return ret;
 545 }
 546
 547 void __exit ltt_debugfs_abi_exit(void)
 548 {
 549         debugfs_remove(lttng_dentry);
 550 }