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 <linux/ringbuffer/vfs.h>
  32 #include "ltt-debugfs-abi.h"
  33 #include "ltt-events.h"
  34
  35 /*
  36  * This is LTTng's own personal way to create a system call as an external
  37  * module. We use ioctl() on /sys/kernel/debug/lttng.
  38  */
  39
  40 static struct dentry *lttng_dentry;
  41 static const struct file_operations lttng_fops;
  42 static const struct file_operations lttng_session_fops;
  43 static const struct file_operations lttng_channel_fops;
  44 static const struct file_operations lttng_metadata_fops;
  45 static const struct file_operations lttng_event_fops;
  46
  47 enum channel_type {
  48         PER_CPU_CHANNEL,
  49         GLOBAL_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 GLOBAL_CHANNEL:
 190                 transport_name = chan_param.overwrite ?
 191                         "global-relay-overwrite" : "global-relay-discard";
 192                 fops = &lttng_channel_fops;
 193                 break;
 194         case METADATA_CHANNEL:
 195                 transport_name = "global-relay-discard";
 196                 fops = &lttng_metadata_fops;
 197                 break;
 198         default:
 199                 transport_name = "<unknown>";
 200                 break;
 201         }
 202         /*
 203          * We tolerate no failure path after channel creation. It will stay
 204          * invariant for the rest of the session.
 205          */
 206         chan = ltt_channel_create(session, transport_name, NULL,
 207                                   chan_param.subbuf_size,
 208                                   chan_param.num_subbuf,
 209                                   chan_param.switch_timer_interval,
 210                                   chan_param.read_timer_interval);
 211         if (!chan) {
 212                 ret = -EINVAL;
 213                 goto chan_error;
 214         }
 215         chan->file = chan_file;
 216         chan_file->private_data = chan;
 217         fd_install(chan_fd, chan_file);
 218         if (channel_type == METADATA_CHANNEL)
 219                 lttng_metadata_create_events(chan_file);
 220
 221         /* The channel created holds a reference on the session */
 222         atomic_long_inc(&session_file->f_count);
 223
 224         return chan_fd;
 225
 226 chan_error:
 227         fput(chan_file);
 228 file_error:
 229         put_unused_fd(chan_fd);
 230 fd_error:
 231         return ret;
 232 }
 233
 234 /**
 235  *      lttng_session_ioctl - lttng session fd ioctl
 236  *
 237  *      @file: the file
 238  *      @cmd: the command
 239  *      @arg: command arg
 240  *
 241  *      This ioctl implements lttng commands:
 242  *      LTTNG_CHANNEL
 243  *              Returns a LTTng channel file descriptor
 244  *
 245  * The returned channel will be deleted when its file descriptor is closed.
 246  */
 247 static
 248 long lttng_session_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 249 {
 250         struct ltt_session *session = file->private_data;
 251
 252         switch (cmd) {
 253         case LTTNG_CHANNEL:
 254                 return lttng_abi_create_channel(file,
 255                                 (struct lttng_channel __user *)arg,
 256                                 PER_CPU_CHANNEL);
 257         case LTTNG_SESSION_START:
 258                 return ltt_session_start(session);
 259         case LTTNG_SESSION_STOP:
 260                 return ltt_session_stop(session);
 261         case LTTNG_METADATA:
 262                 return lttng_abi_create_channel(file,
 263                                 (struct lttng_channel __user *)arg,
 264                                 METADATA_CHANNEL);
 265         default:
 266                 return -ENOIOCTLCMD;
 267         }
 268 }
 269
 270 /*
 271  * Called when the last file reference is dropped.
 272  *
 273  * Big fat note: channels and events are invariant for the whole session after
 274  * their creation. So this session destruction also destroys all channel and
 275  * event structures specific to this session (they are not destroyed when their
 276  * individual file is released).
 277  */
 278 static
 279 int lttng_session_release(struct inode *inode, struct file *file)
 280 {
 281         struct ltt_session *session = file->private_data;
 282
 283         if (session)
 284                 ltt_session_destroy(session);
 285         return 0;
 286 }
 287
 288 static const struct file_operations lttng_session_fops = {
 289         .release = lttng_session_release,
 290         .unlocked_ioctl = lttng_session_ioctl,
 291 #ifdef CONFIG_COMPAT
 292         .compat_ioctl = lttng_session_ioctl,
 293 #endif
 294 };
 295
 296 static
 297 int lttng_abi_open_stream(struct file *channel_file)
 298 {
 299         struct ltt_channel *channel = channel_file->private_data;
 300         struct lib_ring_buffer *buf;
 301         int stream_fd, ret;
 302         struct file *stream_file;
 303
 304         buf = channel->ops->buffer_read_open(channel->chan);
 305         if (!buf)
 306                 return -ENOENT;
 307
 308         stream_fd = get_unused_fd();
 309         if (stream_fd < 0) {
 310                 ret = stream_fd;
 311                 goto fd_error;
 312         }
 313         stream_file = anon_inode_getfile("[lttng_stream]",
 314                                          &lib_ring_buffer_file_operations,
 315                                          buf, O_RDWR);
 316         if (IS_ERR(stream_file)) {
 317                 ret = PTR_ERR(stream_file);
 318                 goto file_error;
 319         }
 320         /*
 321          * OPEN_FMODE, called within anon_inode_getfile/alloc_file, don't honor
 322          * FMODE_LSEEK, FMODE_PREAD nor FMODE_PWRITE. We need to read from this
 323          * file descriptor, so we set FMODE_PREAD here.
 324          */
 325         stream_file->f_mode |= FMODE_PREAD;
 326         fd_install(stream_fd, stream_file);
 327         /*
 328          * The stream holds a reference to the channel within the generic ring
 329          * buffer library, so no need to hold a refcount on the channel and
 330          * session files here.
 331          */
 332         return stream_fd;
 333
 334 file_error:
 335         put_unused_fd(stream_fd);
 336 fd_error:
 337         channel->ops->buffer_read_close(buf);
 338         return ret;
 339 }
 340
 341 static
 342 int lttng_abi_create_event(struct file *channel_file,
 343                            struct lttng_event __user *uevent_param)
 344 {
 345         struct ltt_channel *channel = channel_file->private_data;
 346         struct ltt_event *event;
 347         char *event_name;
 348         struct lttng_event event_param;
 349         int event_fd, ret;
 350         struct file *event_file;
 351         void *probe;
 352
 353         if (copy_from_user(&event_param, uevent_param, sizeof(event_param)))
 354                 return -EFAULT;
 355         event_name = kmalloc(PATH_MAX, GFP_KERNEL);
 356         if (!event_name)
 357                 return -ENOMEM;
 358         if (strncpy_from_user(event_name, uevent_param->name, PATH_MAX) < 0) {
 359                 ret = -EFAULT;
 360                 goto name_error;
 361         }
 362         event_name[PATH_MAX - 1] = '\0';
 363
 364         probe = ltt_probe_get(event_name);
 365         if (!probe) {
 366                 ret = -ENOENT;
 367                 goto probe_error;
 368         }
 369         event_fd = get_unused_fd();
 370         if (event_fd < 0) {
 371                 ret = event_fd;
 372                 goto fd_error;
 373         }
 374         event_file = anon_inode_getfile("[lttng_event]",
 375                                         &lttng_event_fops,
 376                                         NULL, O_RDWR);
 377         if (IS_ERR(event_file)) {
 378                 ret = PTR_ERR(event_file);
 379                 goto file_error;
 380         }
 381         /*
 382          * We tolerate no failure path after event creation. It will stay
 383          * invariant for the rest of the session.
 384          */
 385         event = ltt_event_create(channel, event_name, event_param.itype,
 386                                  probe, NULL);
 387         if (!event) {
 388                 goto event_error;
 389                 ret = -EEXIST;
 390         }
 391         event_file->private_data = event;
 392         fd_install(event_fd, event_file);
 393         /* The event holds a reference on the channel */
 394         atomic_long_inc(&channel_file->f_count);
 395         kfree(event_name);
 396         return event_fd;
 397
 398 event_error:
 399         fput(event_file);
 400 file_error:
 401         put_unused_fd(event_fd);
 402 fd_error:
 403         ltt_probe_put(probe);
 404 probe_error:
 405 name_error:
 406         kfree(event_name);
 407         return ret;
 408 }
 409
 410 /**
 411  *      lttng_channel_ioctl - lttng syscall through ioctl
 412  *
 413  *      @file: the file
 414  *      @cmd: the command
 415  *      @arg: command arg
 416  *
 417  *      This ioctl implements lttng commands:
 418  *      LTTNG_STREAM
 419  *              Returns an event stream file descriptor or failure.
 420  *              (typically, one event stream records events from one CPU)
 421  *      LTTNG_EVENT
 422  *              Returns an event file descriptor or failure.
 423  *
 424  * Channel and event file descriptors also hold a reference on the session.
 425  */
 426 static
 427 long lttng_channel_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 428 {
 429         switch (cmd) {
 430         case LTTNG_STREAM:
 431                 return lttng_abi_open_stream(file);
 432         case LTTNG_EVENT:
 433                 return lttng_abi_create_event(file, (struct lttng_event __user *)arg);
 434         default:
 435                 return -ENOIOCTLCMD;
 436         }
 437 }
 438
 439 /**
 440  *      lttng_metadata_ioctl - lttng syscall through ioctl
 441  *
 442  *      @file: the file
 443  *      @cmd: the command
 444  *      @arg: command arg
 445  *
 446  *      This ioctl implements lttng commands:
 447  *      LTTNG_STREAM
 448  *              Returns an event stream file descriptor or failure.
 449  *
 450  * Channel and event file descriptors also hold a reference on the session.
 451  */
 452 static
 453 long lttng_metadata_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 454 {
 455         switch (cmd) {
 456         case LTTNG_STREAM:
 457                 return lttng_abi_open_stream(file);
 458         default:
 459                 return -ENOIOCTLCMD;
 460         }
 461 }
 462
 463 /* TODO: poll */
 464 #if 0
 465 /**
 466  *      lttng_channel_poll - lttng stream addition/removal monitoring
 467  *
 468  *      @file: the file
 469  *      @wait: poll table
 470  */
 471 unsigned int lttng_channel_poll(struct file *file, poll_table *wait)
 472 {
 473         struct ltt_channel *channel = file->private_data;
 474         unsigned int mask = 0;
 475
 476         if (file->f_mode & FMODE_READ) {
 477                 poll_wait_set_exclusive(wait);
 478                 poll_wait(file, &channel->notify_wait, wait);
 479
 480                 /* TODO: identify when the channel is being finalized. */
 481                 if (finalized)
 482                         return POLLHUP;
 483                 else
 484                         return POLLIN | POLLRDNORM;
 485         }
 486         return mask;
 487
 488 }
 489 #endif //0
 490
 491 static
 492 int lttng_channel_release(struct inode *inode, struct file *file)
 493 {
 494         struct ltt_channel *channel = file->private_data;
 495
 496         if (channel)
 497                 fput(channel->session->file);
 498         return 0;
 499 }
 500
 501 static const struct file_operations lttng_channel_fops = {
 502         .release = lttng_channel_release,
 503 /* TODO */
 504 #if 0
 505         .poll = lttng_channel_poll,
 506 #endif //0
 507         .unlocked_ioctl = lttng_channel_ioctl,
 508 #ifdef CONFIG_COMPAT
 509         .compat_ioctl = lttng_channel_ioctl,
 510 #endif
 511 };
 512
 513 static const struct file_operations lttng_metadata_fops = {
 514         .release = lttng_channel_release,
 515         .unlocked_ioctl = lttng_metadata_ioctl,
 516 #ifdef CONFIG_COMPAT
 517         .compat_ioctl = lttng_metadata_ioctl,
 518 #endif
 519 };
 520
 521 static
 522 int lttng_event_release(struct inode *inode, struct file *file)
 523 {
 524         struct ltt_event *event = file->private_data;
 525
 526         if (event)
 527                 fput(event->chan->file);
 528         return 0;
 529 }
 530
 531 /* TODO: filter control ioctl */
 532 static const struct file_operations lttng_event_fops = {
 533         .release = lttng_event_release,
 534 };
 535
 536 int __init ltt_debugfs_abi_init(void)
 537 {
 538         int ret = 0;
 539
 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 }