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         char *event_name = "lttng_metadata";
 150         struct ltt_event *event;
 151         int ret;
 152
 153         /*
 154          * We tolerate no failure path after event creation. It will stay
 155          * invariant for the rest of the session.
 156          */
 157         event = ltt_event_create(channel, event_name, &metadata_params, NULL);
 158         if (!event) {
 159                 goto create_error;
 160                 ret = -EEXIST;
 161         }
 162         return;
 163
 164 create_error:
 165         WARN_ON(1);
 166         return;         /* not allowed to return error */
 167 }
 168
 169 static
 170 int lttng_abi_create_channel(struct file *session_file,
 171                              struct lttng_kernel_channel __user *uchan_param,
 172                              enum channel_type channel_type)
 173 {
 174         struct ltt_session *session = session_file->private_data;
 175         const struct file_operations *fops;
 176         const char *transport_name;
 177         struct ltt_channel *chan;
 178         struct file *chan_file;
 179         struct lttng_kernel_channel chan_param;
 180         int chan_fd;
 181         int ret = 0;
 182
 183         if (copy_from_user(&chan_param, uchan_param, sizeof(chan_param)))
 184                 return -EFAULT;
 185         chan_fd = get_unused_fd();
 186         if (chan_fd < 0) {
 187                 ret = chan_fd;
 188                 goto fd_error;
 189         }
 190         chan_file = anon_inode_getfile("[lttng_channel]",
 191                                        &lttng_channel_fops,
 192                                        NULL, O_RDWR);
 193         if (IS_ERR(chan_file)) {
 194                 ret = PTR_ERR(chan_file);
 195                 goto file_error;
 196         }
 197         switch (channel_type) {
 198         case PER_CPU_CHANNEL:
 199                 transport_name = chan_param.overwrite ?
 200                         "relay-overwrite" : "relay-discard";
 201                 fops = &lttng_channel_fops;
 202                 break;
 203         case METADATA_CHANNEL:
 204                 transport_name = "relay-metadata";
 205                 fops = &lttng_metadata_fops;
 206                 break;
 207         default:
 208                 transport_name = "<unknown>";
 209                 break;
 210         }
 211         /*
 212          * We tolerate no failure path after channel creation. It will stay
 213          * invariant for the rest of the session.
 214          */
 215         chan = ltt_channel_create(session, transport_name, NULL,
 216                                   chan_param.subbuf_size,
 217                                   chan_param.num_subbuf,
 218                                   chan_param.switch_timer_interval,
 219                                   chan_param.read_timer_interval);
 220         if (!chan) {
 221                 ret = -EINVAL;
 222                 goto chan_error;
 223         }
 224         chan->file = chan_file;
 225         chan_file->private_data = chan;
 226         fd_install(chan_fd, chan_file);
 227         if (channel_type == METADATA_CHANNEL) {
 228                 session->metadata = chan;
 229                 lttng_metadata_create_events(chan_file);
 230         }
 231
 232         /* The channel created holds a reference on the session */
 233         atomic_long_inc(&session_file->f_count);
 234
 235         return chan_fd;
 236
 237 chan_error:
 238         fput(chan_file);
 239 file_error:
 240         put_unused_fd(chan_fd);
 241 fd_error:
 242         return ret;
 243 }
 244
 245 /**
 246  *      lttng_session_ioctl - lttng session fd ioctl
 247  *
 248  *      @file: the file
 249  *      @cmd: the command
 250  *      @arg: command arg
 251  *
 252  *      This ioctl implements lttng commands:
 253  *      LTTNG_KERNEL_CHANNEL
 254  *              Returns a LTTng channel file descriptor
 255  *
 256  * The returned channel will be deleted when its file descriptor is closed.
 257  */
 258 static
 259 long lttng_session_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 260 {
 261         struct ltt_session *session = file->private_data;
 262
 263         switch (cmd) {
 264         case LTTNG_KERNEL_CHANNEL:
 265                 return lttng_abi_create_channel(file,
 266                                 (struct lttng_kernel_channel __user *) arg,
 267                                 PER_CPU_CHANNEL);
 268         case LTTNG_KERNEL_SESSION_START:
 269                 return ltt_session_start(session);
 270         case LTTNG_KERNEL_SESSION_STOP:
 271                 return ltt_session_stop(session);
 272         case LTTNG_KERNEL_METADATA:
 273                 return lttng_abi_create_channel(file,
 274                                 (struct lttng_kernel_channel __user *) arg,
 275                                 METADATA_CHANNEL);
 276         default:
 277                 return -ENOIOCTLCMD;
 278         }
 279 }
 280
 281 /*
 282  * Called when the last file reference is dropped.
 283  *
 284  * Big fat note: channels and events are invariant for the whole session after
 285  * their creation. So this session destruction also destroys all channel and
 286  * event structures specific to this session (they are not destroyed when their
 287  * individual file is released).
 288  */
 289 static
 290 int lttng_session_release(struct inode *inode, struct file *file)
 291 {
 292         struct ltt_session *session = file->private_data;
 293
 294         if (session)
 295                 ltt_session_destroy(session);
 296         return 0;
 297 }
 298
 299 static const struct file_operations lttng_session_fops = {
 300         .release = lttng_session_release,
 301         .unlocked_ioctl = lttng_session_ioctl,
 302 #ifdef CONFIG_COMPAT
 303         .compat_ioctl = lttng_session_ioctl,
 304 #endif
 305 };
 306
 307 static
 308 int lttng_abi_open_stream(struct file *channel_file)
 309 {
 310         struct ltt_channel *channel = channel_file->private_data;
 311         struct lib_ring_buffer *buf;
 312         int stream_fd, ret;
 313         struct file *stream_file;
 314
 315         buf = channel->ops->buffer_read_open(channel->chan);
 316         if (!buf)
 317                 return -ENOENT;
 318
 319         stream_fd = get_unused_fd();
 320         if (stream_fd < 0) {
 321                 ret = stream_fd;
 322                 goto fd_error;
 323         }
 324         stream_file = anon_inode_getfile("[lttng_stream]",
 325                                          &lib_ring_buffer_file_operations,
 326                                          buf, O_RDWR);
 327         if (IS_ERR(stream_file)) {
 328                 ret = PTR_ERR(stream_file);
 329                 goto file_error;
 330         }
 331         /*
 332          * OPEN_FMODE, called within anon_inode_getfile/alloc_file, don't honor
 333          * FMODE_LSEEK, FMODE_PREAD nor FMODE_PWRITE. We need to read from this
 334          * file descriptor, so we set FMODE_PREAD here.
 335          */
 336         stream_file->f_mode |= FMODE_PREAD;
 337         fd_install(stream_fd, stream_file);
 338         /*
 339          * The stream holds a reference to the channel within the generic ring
 340          * buffer library, so no need to hold a refcount on the channel and
 341          * session files here.
 342          */
 343         return stream_fd;
 344
 345 file_error:
 346         put_unused_fd(stream_fd);
 347 fd_error:
 348         channel->ops->buffer_read_close(buf);
 349         return ret;
 350 }
 351
 352 static
 353 int lttng_abi_create_event(struct file *channel_file,
 354                            struct lttng_kernel_event __user *uevent_param)
 355 {
 356         struct ltt_channel *channel = channel_file->private_data;
 357         struct ltt_event *event;
 358         char *event_name;
 359         struct lttng_kernel_event event_param;
 360         int event_fd, ret;
 361         struct file *event_file;
 362
 363         if (copy_from_user(&event_param, uevent_param, sizeof(event_param)))
 364                 return -EFAULT;
 365         event_name = kmalloc(PATH_MAX, GFP_KERNEL);
 366         if (!event_name)
 367                 return -ENOMEM;
 368         if (strncpy_from_user(event_name, uevent_param->name, PATH_MAX) < 0) {
 369                 ret = -EFAULT;
 370                 goto name_error;
 371         }
 372         event_name[PATH_MAX - 1] = '\0';
 373         switch (event_param.instrumentation) {
 374         case LTTNG_KERNEL_KPROBES:
 375                 event_param.u.kprobe.symbol_name[LTTNG_SYM_NAME_LEN - 1] = '\0';
 376                 break;
 377         case LTTNG_KERNEL_FUNCTION_TRACER:
 378                 event_param.u.ftrace.symbol_name[LTTNG_SYM_NAME_LEN - 1] = '\0';
 379                 break;
 380         default:
 381                 break;
 382         }
 383         event_fd = get_unused_fd();
 384         if (event_fd < 0) {
 385                 ret = event_fd;
 386                 goto fd_error;
 387         }
 388         event_file = anon_inode_getfile("[lttng_event]",
 389                                         &lttng_event_fops,
 390                                         NULL, O_RDWR);
 391         if (IS_ERR(event_file)) {
 392                 ret = PTR_ERR(event_file);
 393                 goto file_error;
 394         }
 395         /*
 396          * We tolerate no failure path after event creation. It will stay
 397          * invariant for the rest of the session.
 398          */
 399         event = ltt_event_create(channel, event_name, &event_param, NULL);
 400         if (!event) {
 401                 ret = -EEXIST;
 402                 goto event_error;
 403         }
 404         event_file->private_data = event;
 405         fd_install(event_fd, event_file);
 406         /* The event holds a reference on the channel */
 407         atomic_long_inc(&channel_file->f_count);
 408         kfree(event_name);
 409         return event_fd;
 410
 411 event_error:
 412         fput(event_file);
 413 file_error:
 414         put_unused_fd(event_fd);
 415 fd_error:
 416 name_error:
 417         kfree(event_name);
 418         return ret;
 419 }
 420
 421 /**
 422  *      lttng_channel_ioctl - lttng syscall through ioctl
 423  *
 424  *      @file: the file
 425  *      @cmd: the command
 426  *      @arg: command arg
 427  *
 428  *      This ioctl implements lttng commands:
 429  *      LTTNG_KERNEL_STREAM
 430  *              Returns an event stream file descriptor or failure.
 431  *              (typically, one event stream records events from one CPU)
 432  *      LTTNG_KERNEL_EVENT
 433  *              Returns an event file descriptor or failure.
 434  *
 435  * Channel and event file descriptors also hold a reference on the session.
 436  */
 437 static
 438 long lttng_channel_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 439 {
 440         switch (cmd) {
 441         case LTTNG_KERNEL_STREAM:
 442                 return lttng_abi_open_stream(file);
 443         case LTTNG_KERNEL_EVENT:
 444                 return lttng_abi_create_event(file, (struct lttng_kernel_event __user *) arg);
 445         default:
 446                 return -ENOIOCTLCMD;
 447         }
 448 }
 449
 450 /**
 451  *      lttng_metadata_ioctl - lttng syscall through ioctl
 452  *
 453  *      @file: the file
 454  *      @cmd: the command
 455  *      @arg: command arg
 456  *
 457  *      This ioctl implements lttng commands:
 458  *      LTTNG_KERNEL_STREAM
 459  *              Returns an event stream file descriptor or failure.
 460  *
 461  * Channel and event file descriptors also hold a reference on the session.
 462  */
 463 static
 464 long lttng_metadata_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 465 {
 466         switch (cmd) {
 467         case LTTNG_KERNEL_STREAM:
 468                 return lttng_abi_open_stream(file);
 469         default:
 470                 return -ENOIOCTLCMD;
 471         }
 472 }
 473
 474 /* TODO: poll */
 475 #if 0
 476 /**
 477  *      lttng_channel_poll - lttng stream addition/removal monitoring
 478  *
 479  *      @file: the file
 480  *      @wait: poll table
 481  */
 482 unsigned int lttng_channel_poll(struct file *file, poll_table *wait)
 483 {
 484         struct ltt_channel *channel = file->private_data;
 485         unsigned int mask = 0;
 486
 487         if (file->f_mode & FMODE_READ) {
 488                 poll_wait_set_exclusive(wait);
 489                 poll_wait(file, &channel->notify_wait, wait);
 490
 491                 /* TODO: identify when the channel is being finalized. */
 492                 if (finalized)
 493                         return POLLHUP;
 494                 else
 495                         return POLLIN | POLLRDNORM;
 496         }
 497         return mask;
 498
 499 }
 500 #endif //0
 501
 502 static
 503 int lttng_channel_release(struct inode *inode, struct file *file)
 504 {
 505         struct ltt_channel *channel = file->private_data;
 506
 507         if (channel)
 508                 fput(channel->session->file);
 509         return 0;
 510 }
 511
 512 static const struct file_operations lttng_channel_fops = {
 513         .release = lttng_channel_release,
 514 /* TODO */
 515 #if 0
 516         .poll = lttng_channel_poll,
 517 #endif //0
 518         .unlocked_ioctl = lttng_channel_ioctl,
 519 #ifdef CONFIG_COMPAT
 520         .compat_ioctl = lttng_channel_ioctl,
 521 #endif
 522 };
 523
 524 static const struct file_operations lttng_metadata_fops = {
 525         .release = lttng_channel_release,
 526         .unlocked_ioctl = lttng_metadata_ioctl,
 527 #ifdef CONFIG_COMPAT
 528         .compat_ioctl = lttng_metadata_ioctl,
 529 #endif
 530 };
 531
 532 static
 533 int lttng_event_release(struct inode *inode, struct file *file)
 534 {
 535         struct ltt_event *event = file->private_data;
 536
 537         if (event) {
 538                 ltt_event_unregister(event);
 539                 fput(event->chan->file);
 540         }
 541         return 0;
 542 }
 543
 544 /* TODO: filter control ioctl */
 545 static const struct file_operations lttng_event_fops = {
 546         .release = lttng_event_release,
 547 };
 548
 549 int __init ltt_debugfs_abi_init(void)
 550 {
 551         int ret = 0;
 552
 553         wrapper_vmalloc_sync_all();
 554         lttng_dentry = debugfs_create_file("lttng", S_IWUSR, NULL, NULL,
 555                                            &lttng_fops);
 556         if (IS_ERR(lttng_dentry) || !lttng_dentry) {
 557                 printk(KERN_ERR "Error creating LTTng control file\n");
 558                 ret = -ENOMEM;
 559                 goto error;
 560         }
 561 error:
 562         return ret;
 563 }
 564
 565 void __exit ltt_debugfs_abi_exit(void)
 566 {
 567         debugfs_remove(lttng_dentry);
 568 }