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 int lttng_abi_tracepoint_list(void)
  89 {
  90         struct file *tracepoint_list_file;
  91         int file_fd, ret;
  92
  93         file_fd = get_unused_fd();
  94         if (file_fd < 0) {
  95                 ret = file_fd;
  96                 goto fd_error;
  97         }
  98         tracepoint_list_file = anon_inode_getfile("[lttng_session]",
  99                                           &lttng_tracepoint_list_fops,
 100                                           NULL, O_RDWR);
 101         if (IS_ERR(tracepoint_list_file)) {
 102                 ret = PTR_ERR(tracepoint_list_file);
 103                 goto file_error;
 104         }
 105         fd_install(file_fd, tracepoint_list_file);
 106         return file_fd;
 107
 108 file_error:
 109         put_unused_fd(file_fd);
 110 fd_error:
 111         return ret;
 112 }
 113
 114 static
 115 long lttng_abi_tracer_version(struct file *file,
 116         struct lttng_kernel_tracer_version __user *uversion_param)
 117 {
 118         struct lttng_kernel_tracer_version v;
 119
 120         v.version = LTTNG_VERSION;
 121         v.patchlevel = LTTNG_PATCHLEVEL;
 122         v.sublevel = LTTNG_SUBLEVEL;
 123
 124         if (copy_to_user(uversion_param, &v, sizeof(v)))
 125                 return -EFAULT;
 126         return 0;
 127 }
 128
 129 /**
 130  *      lttng_ioctl - lttng syscall through ioctl
 131  *
 132  *      @file: the file
 133  *      @cmd: the command
 134  *      @arg: command arg
 135  *
 136  *      This ioctl implements lttng commands:
 137  *      LTTNG_KERNEL_SESSION
 138  *              Returns a LTTng trace session file descriptor
 139  *      LTTNG_KERNEL_TRACER_VERSION
 140  *              Returns the LTTng kernel tracer version
 141  *      LTTNG_KERNEL_TRACEPOINT_LIST
 142  *              Returns a file descriptor listing available tracepoints
 143  *
 144  * The returned session will be deleted when its file descriptor is closed.
 145  */
 146 static
 147 long lttng_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 148 {
 149         switch (cmd) {
 150         case LTTNG_KERNEL_SESSION:
 151                 return lttng_abi_create_session();
 152         case LTTNG_KERNEL_TRACER_VERSION:
 153                 return lttng_abi_tracer_version(file,
 154                                 (struct lttng_kernel_tracer_version __user *) arg);
 155         case LTTNG_KERNEL_TRACEPOINT_LIST:
 156                 return lttng_abi_tracepoint_list();
 157         default:
 158                 return -ENOIOCTLCMD;
 159         }
 160 }
 161
 162 static const struct file_operations lttng_fops = {
 163         .unlocked_ioctl = lttng_ioctl,
 164 #ifdef CONFIG_COMPAT
 165         .compat_ioctl = lttng_ioctl,
 166 #endif
 167 };
 168
 169 /*
 170  * We tolerate no failure in this function (if one happens, we print a dmesg
 171  * error, but cannot return any error, because the channel information is
 172  * invariant.
 173  */
 174 static
 175 void lttng_metadata_create_events(struct file *channel_file)
 176 {
 177         struct ltt_channel *channel = channel_file->private_data;
 178         static struct lttng_kernel_event metadata_params = {
 179                 .instrumentation = LTTNG_KERNEL_TRACEPOINT,
 180                 .name = "lttng_metadata",
 181         };
 182         struct ltt_event *event;
 183         int ret;
 184
 185         /*
 186          * We tolerate no failure path after event creation. It will stay
 187          * invariant for the rest of the session.
 188          */
 189         event = ltt_event_create(channel, &metadata_params, NULL);
 190         if (!event) {
 191                 ret = -EINVAL;
 192                 goto create_error;
 193         }
 194         return;
 195
 196 create_error:
 197         WARN_ON(1);
 198         return;         /* not allowed to return error */
 199 }
 200
 201 static
 202 int lttng_abi_create_channel(struct file *session_file,
 203                              struct lttng_kernel_channel __user *uchan_param,
 204                              enum channel_type channel_type)
 205 {
 206         struct ltt_session *session = session_file->private_data;
 207         const struct file_operations *fops;
 208         const char *transport_name;
 209         struct ltt_channel *chan;
 210         struct file *chan_file;
 211         struct lttng_kernel_channel chan_param;
 212         int chan_fd;
 213         int ret = 0;
 214
 215         if (copy_from_user(&chan_param, uchan_param, sizeof(chan_param)))
 216                 return -EFAULT;
 217         chan_fd = get_unused_fd();
 218         if (chan_fd < 0) {
 219                 ret = chan_fd;
 220                 goto fd_error;
 221         }
 222         chan_file = anon_inode_getfile("[lttng_channel]",
 223                                        &lttng_channel_fops,
 224                                        NULL, O_RDWR);
 225         if (IS_ERR(chan_file)) {
 226                 ret = PTR_ERR(chan_file);
 227                 goto file_error;
 228         }
 229         switch (channel_type) {
 230         case PER_CPU_CHANNEL:
 231                 transport_name = chan_param.overwrite ?
 232                         "relay-overwrite" : "relay-discard";
 233                 fops = &lttng_channel_fops;
 234                 break;
 235         case METADATA_CHANNEL:
 236                 transport_name = "relay-metadata";
 237                 fops = &lttng_metadata_fops;
 238                 break;
 239         default:
 240                 transport_name = "<unknown>";
 241                 break;
 242         }
 243         /*
 244          * We tolerate no failure path after channel creation. It will stay
 245          * invariant for the rest of the session.
 246          */
 247         chan = ltt_channel_create(session, transport_name, NULL,
 248                                   chan_param.subbuf_size,
 249                                   chan_param.num_subbuf,
 250                                   chan_param.switch_timer_interval,
 251                                   chan_param.read_timer_interval);
 252         if (!chan) {
 253                 ret = -EINVAL;
 254                 goto chan_error;
 255         }
 256         chan->file = chan_file;
 257         chan_file->private_data = chan;
 258         fd_install(chan_fd, chan_file);
 259         if (channel_type == METADATA_CHANNEL) {
 260                 session->metadata = chan;
 261                 lttng_metadata_create_events(chan_file);
 262         }
 263
 264         /* The channel created holds a reference on the session */
 265         atomic_long_inc(&session_file->f_count);
 266
 267         return chan_fd;
 268
 269 chan_error:
 270         fput(chan_file);
 271 file_error:
 272         put_unused_fd(chan_fd);
 273 fd_error:
 274         return ret;
 275 }
 276
 277 /**
 278  *      lttng_session_ioctl - lttng session fd ioctl
 279  *
 280  *      @file: the file
 281  *      @cmd: the command
 282  *      @arg: command arg
 283  *
 284  *      This ioctl implements lttng commands:
 285  *      LTTNG_KERNEL_CHANNEL
 286  *              Returns a LTTng channel file descriptor
 287  *
 288  * The returned channel will be deleted when its file descriptor is closed.
 289  */
 290 static
 291 long lttng_session_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 292 {
 293         struct ltt_session *session = file->private_data;
 294
 295         switch (cmd) {
 296         case LTTNG_KERNEL_CHANNEL:
 297                 return lttng_abi_create_channel(file,
 298                                 (struct lttng_kernel_channel __user *) arg,
 299                                 PER_CPU_CHANNEL);
 300         case LTTNG_KERNEL_SESSION_START:
 301                 return ltt_session_start(session);
 302         case LTTNG_KERNEL_SESSION_STOP:
 303                 return ltt_session_stop(session);
 304         case LTTNG_KERNEL_METADATA:
 305                 return lttng_abi_create_channel(file,
 306                                 (struct lttng_kernel_channel __user *) arg,
 307                                 METADATA_CHANNEL);
 308         default:
 309                 return -ENOIOCTLCMD;
 310         }
 311 }
 312
 313 /*
 314  * Called when the last file reference is dropped.
 315  *
 316  * Big fat note: channels and events are invariant for the whole session after
 317  * their creation. So this session destruction also destroys all channel and
 318  * event structures specific to this session (they are not destroyed when their
 319  * individual file is released).
 320  */
 321 static
 322 int lttng_session_release(struct inode *inode, struct file *file)
 323 {
 324         struct ltt_session *session = file->private_data;
 325
 326         if (session)
 327                 ltt_session_destroy(session);
 328         return 0;
 329 }
 330
 331 static const struct file_operations lttng_session_fops = {
 332         .release = lttng_session_release,
 333         .unlocked_ioctl = lttng_session_ioctl,
 334 #ifdef CONFIG_COMPAT
 335         .compat_ioctl = lttng_session_ioctl,
 336 #endif
 337 };
 338
 339 static
 340 int lttng_abi_open_stream(struct file *channel_file)
 341 {
 342         struct ltt_channel *channel = channel_file->private_data;
 343         struct lib_ring_buffer *buf;
 344         int stream_fd, ret;
 345         struct file *stream_file;
 346
 347         buf = channel->ops->buffer_read_open(channel->chan);
 348         if (!buf)
 349                 return -ENOENT;
 350
 351         stream_fd = get_unused_fd();
 352         if (stream_fd < 0) {
 353                 ret = stream_fd;
 354                 goto fd_error;
 355         }
 356         stream_file = anon_inode_getfile("[lttng_stream]",
 357                                          &lib_ring_buffer_file_operations,
 358                                          buf, O_RDWR);
 359         if (IS_ERR(stream_file)) {
 360                 ret = PTR_ERR(stream_file);
 361                 goto file_error;
 362         }
 363         /*
 364          * OPEN_FMODE, called within anon_inode_getfile/alloc_file, don't honor
 365          * FMODE_LSEEK, FMODE_PREAD nor FMODE_PWRITE. We need to read from this
 366          * file descriptor, so we set FMODE_PREAD here.
 367          */
 368         stream_file->f_mode |= FMODE_PREAD;
 369         fd_install(stream_fd, stream_file);
 370         /*
 371          * The stream holds a reference to the channel within the generic ring
 372          * buffer library, so no need to hold a refcount on the channel and
 373          * session files here.
 374          */
 375         return stream_fd;
 376
 377 file_error:
 378         put_unused_fd(stream_fd);
 379 fd_error:
 380         channel->ops->buffer_read_close(buf);
 381         return ret;
 382 }
 383
 384 static
 385 int lttng_abi_create_event(struct file *channel_file,
 386                            struct lttng_kernel_event __user *uevent_param)
 387 {
 388         struct ltt_channel *channel = channel_file->private_data;
 389         struct ltt_event *event;
 390         struct lttng_kernel_event event_param;
 391         int event_fd, ret;
 392         struct file *event_file;
 393
 394         if (copy_from_user(&event_param, uevent_param, sizeof(event_param)))
 395                 return -EFAULT;
 396         event_param.name[LTTNG_SYM_NAME_LEN - 1] = '\0';
 397         switch (event_param.instrumentation) {
 398         case LTTNG_KERNEL_KPROBE:
 399                 event_param.u.kprobe.symbol_name[LTTNG_SYM_NAME_LEN - 1] = '\0';
 400                 break;
 401         case LTTNG_KERNEL_FUNCTION:
 402                 event_param.u.ftrace.symbol_name[LTTNG_SYM_NAME_LEN - 1] = '\0';
 403                 break;
 404         default:
 405                 break;
 406         }
 407         event_fd = get_unused_fd();
 408         if (event_fd < 0) {
 409                 ret = event_fd;
 410                 goto fd_error;
 411         }
 412         event_file = anon_inode_getfile("[lttng_event]",
 413                                         &lttng_event_fops,
 414                                         NULL, O_RDWR);
 415         if (IS_ERR(event_file)) {
 416                 ret = PTR_ERR(event_file);
 417                 goto file_error;
 418         }
 419         /*
 420          * We tolerate no failure path after event creation. It will stay
 421          * invariant for the rest of the session.
 422          */
 423         event = ltt_event_create(channel, &event_param, NULL);
 424         if (!event) {
 425                 ret = -EINVAL;
 426                 goto event_error;
 427         }
 428         event_file->private_data = event;
 429         fd_install(event_fd, event_file);
 430         /* The event holds a reference on the channel */
 431         atomic_long_inc(&channel_file->f_count);
 432         return event_fd;
 433
 434 event_error:
 435         fput(event_file);
 436 file_error:
 437         put_unused_fd(event_fd);
 438 fd_error:
 439         return ret;
 440 }
 441
 442 /**
 443  *      lttng_channel_ioctl - lttng syscall through ioctl
 444  *
 445  *      @file: the file
 446  *      @cmd: the command
 447  *      @arg: command arg
 448  *
 449  *      This ioctl implements lttng commands:
 450  *      LTTNG_KERNEL_STREAM
 451  *              Returns an event stream file descriptor or failure.
 452  *              (typically, one event stream records events from one CPU)
 453  *      LTTNG_KERNEL_EVENT
 454  *              Returns an event file descriptor or failure.
 455  *
 456  * Channel and event file descriptors also hold a reference on the session.
 457  */
 458 static
 459 long lttng_channel_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 460 {
 461         switch (cmd) {
 462         case LTTNG_KERNEL_STREAM:
 463                 return lttng_abi_open_stream(file);
 464         case LTTNG_KERNEL_EVENT:
 465                 return lttng_abi_create_event(file, (struct lttng_kernel_event __user *) arg);
 466         default:
 467                 return -ENOIOCTLCMD;
 468         }
 469 }
 470
 471 /**
 472  *      lttng_metadata_ioctl - lttng syscall through ioctl
 473  *
 474  *      @file: the file
 475  *      @cmd: the command
 476  *      @arg: command arg
 477  *
 478  *      This ioctl implements lttng commands:
 479  *      LTTNG_KERNEL_STREAM
 480  *              Returns an event stream file descriptor or failure.
 481  *
 482  * Channel and event file descriptors also hold a reference on the session.
 483  */
 484 static
 485 long lttng_metadata_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 486 {
 487         switch (cmd) {
 488         case LTTNG_KERNEL_STREAM:
 489                 return lttng_abi_open_stream(file);
 490         default:
 491                 return -ENOIOCTLCMD;
 492         }
 493 }
 494
 495 /* TODO: poll */
 496 #if 0
 497 /**
 498  *      lttng_channel_poll - lttng stream addition/removal monitoring
 499  *
 500  *      @file: the file
 501  *      @wait: poll table
 502  */
 503 unsigned int lttng_channel_poll(struct file *file, poll_table *wait)
 504 {
 505         struct ltt_channel *channel = file->private_data;
 506         unsigned int mask = 0;
 507
 508         if (file->f_mode & FMODE_READ) {
 509                 poll_wait_set_exclusive(wait);
 510                 poll_wait(file, &channel->notify_wait, wait);
 511
 512                 /* TODO: identify when the channel is being finalized. */
 513                 if (finalized)
 514                         return POLLHUP;
 515                 else
 516                         return POLLIN | POLLRDNORM;
 517         }
 518         return mask;
 519
 520 }
 521 #endif //0
 522
 523 static
 524 int lttng_channel_release(struct inode *inode, struct file *file)
 525 {
 526         struct ltt_channel *channel = file->private_data;
 527
 528         if (channel)
 529                 fput(channel->session->file);
 530         return 0;
 531 }
 532
 533 static const struct file_operations lttng_channel_fops = {
 534         .release = lttng_channel_release,
 535 /* TODO */
 536 #if 0
 537         .poll = lttng_channel_poll,
 538 #endif //0
 539         .unlocked_ioctl = lttng_channel_ioctl,
 540 #ifdef CONFIG_COMPAT
 541         .compat_ioctl = lttng_channel_ioctl,
 542 #endif
 543 };
 544
 545 static const struct file_operations lttng_metadata_fops = {
 546         .release = lttng_channel_release,
 547         .unlocked_ioctl = lttng_metadata_ioctl,
 548 #ifdef CONFIG_COMPAT
 549         .compat_ioctl = lttng_metadata_ioctl,
 550 #endif
 551 };
 552
 553 static
 554 int lttng_event_release(struct inode *inode, struct file *file)
 555 {
 556         struct ltt_event *event = file->private_data;
 557
 558         if (event)
 559                 fput(event->chan->file);
 560         return 0;
 561 }
 562
 563 /* TODO: filter control ioctl */
 564 static const struct file_operations lttng_event_fops = {
 565         .release = lttng_event_release,
 566 };
 567
 568 int __init ltt_debugfs_abi_init(void)
 569 {
 570         int ret = 0;
 571
 572         wrapper_vmalloc_sync_all();
 573         lttng_dentry = debugfs_create_file("lttng", S_IWUSR, NULL, NULL,
 574                                            &lttng_fops);
 575         if (IS_ERR(lttng_dentry) || !lttng_dentry) {
 576                 printk(KERN_ERR "Error creating LTTng control file\n");
 577                 ret = -ENOMEM;
 578                 goto error;
 579         }
 580 error:
 581         return ret;
 582 }
 583
 584 void __exit ltt_debugfs_abi_exit(void)
 585 {
 586         debugfs_remove(lttng_dentry);
 587 }