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         static struct lttng_kernel_event metadata_params = {
 146                 .instrumentation = LTTNG_KERNEL_TRACEPOINTS,
 147                 .name = "lttng_metadata",
 148         };
 149         struct ltt_event *event;
 150         int ret;
 151
 152         /*
 153          * We tolerate no failure path after event creation. It will stay
 154          * invariant for the rest of the session.
 155          */
 156         event = ltt_event_create(channel, &metadata_params, NULL);
 157         if (!event) {
 158                 goto create_error;
 159                 ret = -EEXIST;
 160         }
 161         return;
 162
 163 create_error:
 164         WARN_ON(1);
 165         return;         /* not allowed to return error */
 166 }
 167
 168 static
 169 int lttng_abi_create_channel(struct file *session_file,
 170                              struct lttng_kernel_channel __user *uchan_param,
 171                              enum channel_type channel_type)
 172 {
 173         struct ltt_session *session = session_file->private_data;
 174         const struct file_operations *fops;
 175         const char *transport_name;
 176         struct ltt_channel *chan;
 177         struct file *chan_file;
 178         struct lttng_kernel_channel chan_param;
 179         int chan_fd;
 180         int ret = 0;
 181
 182         if (copy_from_user(&chan_param, uchan_param, sizeof(chan_param)))
 183                 return -EFAULT;
 184         chan_fd = get_unused_fd();
 185         if (chan_fd < 0) {
 186                 ret = chan_fd;
 187                 goto fd_error;
 188         }
 189         chan_file = anon_inode_getfile("[lttng_channel]",
 190                                        &lttng_channel_fops,
 191                                        NULL, O_RDWR);
 192         if (IS_ERR(chan_file)) {
 193                 ret = PTR_ERR(chan_file);
 194                 goto file_error;
 195         }
 196         switch (channel_type) {
 197         case PER_CPU_CHANNEL:
 198                 transport_name = chan_param.overwrite ?
 199                         "relay-overwrite" : "relay-discard";
 200                 fops = &lttng_channel_fops;
 201                 break;
 202         case METADATA_CHANNEL:
 203                 transport_name = "relay-metadata";
 204                 fops = &lttng_metadata_fops;
 205                 break;
 206         default:
 207                 transport_name = "<unknown>";
 208                 break;
 209         }
 210         /*
 211          * We tolerate no failure path after channel creation. It will stay
 212          * invariant for the rest of the session.
 213          */
 214         chan = ltt_channel_create(session, transport_name, NULL,
 215                                   chan_param.subbuf_size,
 216                                   chan_param.num_subbuf,
 217                                   chan_param.switch_timer_interval,
 218                                   chan_param.read_timer_interval);
 219         if (!chan) {
 220                 ret = -EINVAL;
 221                 goto chan_error;
 222         }
 223         chan->file = chan_file;
 224         chan_file->private_data = chan;
 225         fd_install(chan_fd, chan_file);
 226         if (channel_type == METADATA_CHANNEL) {
 227                 session->metadata = chan;
 228                 lttng_metadata_create_events(chan_file);
 229         }
 230
 231         /* The channel created holds a reference on the session */
 232         atomic_long_inc(&session_file->f_count);
 233
 234         return chan_fd;
 235
 236 chan_error:
 237         fput(chan_file);
 238 file_error:
 239         put_unused_fd(chan_fd);
 240 fd_error:
 241         return ret;
 242 }
 243
 244 /**
 245  *      lttng_session_ioctl - lttng session fd ioctl
 246  *
 247  *      @file: the file
 248  *      @cmd: the command
 249  *      @arg: command arg
 250  *
 251  *      This ioctl implements lttng commands:
 252  *      LTTNG_KERNEL_CHANNEL
 253  *              Returns a LTTng channel file descriptor
 254  *
 255  * The returned channel will be deleted when its file descriptor is closed.
 256  */
 257 static
 258 long lttng_session_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 259 {
 260         struct ltt_session *session = file->private_data;
 261
 262         switch (cmd) {
 263         case LTTNG_KERNEL_CHANNEL:
 264                 return lttng_abi_create_channel(file,
 265                                 (struct lttng_kernel_channel __user *) arg,
 266                                 PER_CPU_CHANNEL);
 267         case LTTNG_KERNEL_SESSION_START:
 268                 return ltt_session_start(session);
 269         case LTTNG_KERNEL_SESSION_STOP:
 270                 return ltt_session_stop(session);
 271         case LTTNG_KERNEL_METADATA:
 272                 return lttng_abi_create_channel(file,
 273                                 (struct lttng_kernel_channel __user *) arg,
 274                                 METADATA_CHANNEL);
 275         default:
 276                 return -ENOIOCTLCMD;
 277         }
 278 }
 279
 280 /*
 281  * Called when the last file reference is dropped.
 282  *
 283  * Big fat note: channels and events are invariant for the whole session after
 284  * their creation. So this session destruction also destroys all channel and
 285  * event structures specific to this session (they are not destroyed when their
 286  * individual file is released).
 287  */
 288 static
 289 int lttng_session_release(struct inode *inode, struct file *file)
 290 {
 291         struct ltt_session *session = file->private_data;
 292
 293         if (session)
 294                 ltt_session_destroy(session);
 295         return 0;
 296 }
 297
 298 static const struct file_operations lttng_session_fops = {
 299         .release = lttng_session_release,
 300         .unlocked_ioctl = lttng_session_ioctl,
 301 #ifdef CONFIG_COMPAT
 302         .compat_ioctl = lttng_session_ioctl,
 303 #endif
 304 };
 305
 306 static
 307 int lttng_abi_open_stream(struct file *channel_file)
 308 {
 309         struct ltt_channel *channel = channel_file->private_data;
 310         struct lib_ring_buffer *buf;
 311         int stream_fd, ret;
 312         struct file *stream_file;
 313
 314         buf = channel->ops->buffer_read_open(channel->chan);
 315         if (!buf)
 316                 return -ENOENT;
 317
 318         stream_fd = get_unused_fd();
 319         if (stream_fd < 0) {
 320                 ret = stream_fd;
 321                 goto fd_error;
 322         }
 323         stream_file = anon_inode_getfile("[lttng_stream]",
 324                                          &lib_ring_buffer_file_operations,
 325                                          buf, O_RDWR);
 326         if (IS_ERR(stream_file)) {
 327                 ret = PTR_ERR(stream_file);
 328                 goto file_error;
 329         }
 330         /*
 331          * OPEN_FMODE, called within anon_inode_getfile/alloc_file, don't honor
 332          * FMODE_LSEEK, FMODE_PREAD nor FMODE_PWRITE. We need to read from this
 333          * file descriptor, so we set FMODE_PREAD here.
 334          */
 335         stream_file->f_mode |= FMODE_PREAD;
 336         fd_install(stream_fd, stream_file);
 337         /*
 338          * The stream holds a reference to the channel within the generic ring
 339          * buffer library, so no need to hold a refcount on the channel and
 340          * session files here.
 341          */
 342         return stream_fd;
 343
 344 file_error:
 345         put_unused_fd(stream_fd);
 346 fd_error:
 347         channel->ops->buffer_read_close(buf);
 348         return ret;
 349 }
 350
 351 static
 352 int lttng_abi_create_event(struct file *channel_file,
 353                            struct lttng_kernel_event __user *uevent_param)
 354 {
 355         struct ltt_channel *channel = channel_file->private_data;
 356         struct ltt_event *event;
 357         struct lttng_kernel_event event_param;
 358         int event_fd, ret;
 359         struct file *event_file;
 360
 361         if (copy_from_user(&event_param, uevent_param, sizeof(event_param)))
 362                 return -EFAULT;
 363         event_param.name[LTTNG_SYM_NAME_LEN - 1] = '\0';
 364         switch (event_param.instrumentation) {
 365         case LTTNG_KERNEL_KPROBES:
 366                 event_param.u.kprobe.symbol_name[LTTNG_SYM_NAME_LEN - 1] = '\0';
 367                 break;
 368         case LTTNG_KERNEL_FUNCTION_TRACER:
 369                 event_param.u.ftrace.symbol_name[LTTNG_SYM_NAME_LEN - 1] = '\0';
 370                 break;
 371         default:
 372                 break;
 373         }
 374         event_fd = get_unused_fd();
 375         if (event_fd < 0) {
 376                 ret = event_fd;
 377                 goto fd_error;
 378         }
 379         event_file = anon_inode_getfile("[lttng_event]",
 380                                         &lttng_event_fops,
 381                                         NULL, O_RDWR);
 382         if (IS_ERR(event_file)) {
 383                 ret = PTR_ERR(event_file);
 384                 goto file_error;
 385         }
 386         /*
 387          * We tolerate no failure path after event creation. It will stay
 388          * invariant for the rest of the session.
 389          */
 390         event = ltt_event_create(channel, &event_param, NULL);
 391         if (!event) {
 392                 ret = -EEXIST;
 393                 goto event_error;
 394         }
 395         event_file->private_data = event;
 396         fd_install(event_fd, event_file);
 397         /* The event holds a reference on the channel */
 398         atomic_long_inc(&channel_file->f_count);
 399         return event_fd;
 400
 401 event_error:
 402         fput(event_file);
 403 file_error:
 404         put_unused_fd(event_fd);
 405 fd_error:
 406         return ret;
 407 }
 408
 409 /**
 410  *      lttng_channel_ioctl - lttng syscall through ioctl
 411  *
 412  *      @file: the file
 413  *      @cmd: the command
 414  *      @arg: command arg
 415  *
 416  *      This ioctl implements lttng commands:
 417  *      LTTNG_KERNEL_STREAM
 418  *              Returns an event stream file descriptor or failure.
 419  *              (typically, one event stream records events from one CPU)
 420  *      LTTNG_KERNEL_EVENT
 421  *              Returns an event file descriptor or failure.
 422  *
 423  * Channel and event file descriptors also hold a reference on the session.
 424  */
 425 static
 426 long lttng_channel_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 427 {
 428         switch (cmd) {
 429         case LTTNG_KERNEL_STREAM:
 430                 return lttng_abi_open_stream(file);
 431         case LTTNG_KERNEL_EVENT:
 432                 return lttng_abi_create_event(file, (struct lttng_kernel_event __user *) arg);
 433         default:
 434                 return -ENOIOCTLCMD;
 435         }
 436 }
 437
 438 /**
 439  *      lttng_metadata_ioctl - lttng syscall through ioctl
 440  *
 441  *      @file: the file
 442  *      @cmd: the command
 443  *      @arg: command arg
 444  *
 445  *      This ioctl implements lttng commands:
 446  *      LTTNG_KERNEL_STREAM
 447  *              Returns an event stream file descriptor or failure.
 448  *
 449  * Channel and event file descriptors also hold a reference on the session.
 450  */
 451 static
 452 long lttng_metadata_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 453 {
 454         switch (cmd) {
 455         case LTTNG_KERNEL_STREAM:
 456                 return lttng_abi_open_stream(file);
 457         default:
 458                 return -ENOIOCTLCMD;
 459         }
 460 }
 461
 462 /* TODO: poll */
 463 #if 0
 464 /**
 465  *      lttng_channel_poll - lttng stream addition/removal monitoring
 466  *
 467  *      @file: the file
 468  *      @wait: poll table
 469  */
 470 unsigned int lttng_channel_poll(struct file *file, poll_table *wait)
 471 {
 472         struct ltt_channel *channel = file->private_data;
 473         unsigned int mask = 0;
 474
 475         if (file->f_mode & FMODE_READ) {
 476                 poll_wait_set_exclusive(wait);
 477                 poll_wait(file, &channel->notify_wait, wait);
 478
 479                 /* TODO: identify when the channel is being finalized. */
 480                 if (finalized)
 481                         return POLLHUP;
 482                 else
 483                         return POLLIN | POLLRDNORM;
 484         }
 485         return mask;
 486
 487 }
 488 #endif //0
 489
 490 static
 491 int lttng_channel_release(struct inode *inode, struct file *file)
 492 {
 493         struct ltt_channel *channel = file->private_data;
 494
 495         if (channel)
 496                 fput(channel->session->file);
 497         return 0;
 498 }
 499
 500 static const struct file_operations lttng_channel_fops = {
 501         .release = lttng_channel_release,
 502 /* TODO */
 503 #if 0
 504         .poll = lttng_channel_poll,
 505 #endif //0
 506         .unlocked_ioctl = lttng_channel_ioctl,
 507 #ifdef CONFIG_COMPAT
 508         .compat_ioctl = lttng_channel_ioctl,
 509 #endif
 510 };
 511
 512 static const struct file_operations lttng_metadata_fops = {
 513         .release = lttng_channel_release,
 514         .unlocked_ioctl = lttng_metadata_ioctl,
 515 #ifdef CONFIG_COMPAT
 516         .compat_ioctl = lttng_metadata_ioctl,
 517 #endif
 518 };
 519
 520 static
 521 int lttng_event_release(struct inode *inode, struct file *file)
 522 {
 523         struct ltt_event *event = file->private_data;
 524
 525         if (event)
 526                 fput(event->chan->file);
 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 }