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         char *event_name = "lttng_metadata";
 146         struct ltt_event *event;
 147         int ret;
 148
 149         /*
 150          * We tolerate no failure path after event creation. It will stay
 151          * invariant for the rest of the session.
 152          */
 153         event = ltt_event_create(channel, event_name, LTTNG_KERNEL_TRACEPOINTS,
 154                                  NULL);
 155         if (!event) {
 156                 goto create_error;
 157                 ret = -EEXIST;
 158         }
 159         return;
 160
 161 create_error:
 162         WARN_ON(1);
 163         return;         /* not allowed to return error */
 164 }
 165
 166 static
 167 int lttng_abi_create_channel(struct file *session_file,
 168                              struct lttng_kernel_channel __user *uchan_param,
 169                              enum channel_type channel_type)
 170 {
 171         struct ltt_session *session = session_file->private_data;
 172         const struct file_operations *fops;
 173         const char *transport_name;
 174         struct ltt_channel *chan;
 175         struct file *chan_file;
 176         struct lttng_kernel_channel chan_param;
 177         int chan_fd;
 178         int ret = 0;
 179
 180         if (copy_from_user(&chan_param, uchan_param, sizeof(chan_param)))
 181                 return -EFAULT;
 182         chan_fd = get_unused_fd();
 183         if (chan_fd < 0) {
 184                 ret = chan_fd;
 185                 goto fd_error;
 186         }
 187         chan_file = anon_inode_getfile("[lttng_channel]",
 188                                        &lttng_channel_fops,
 189                                        NULL, O_RDWR);
 190         if (IS_ERR(chan_file)) {
 191                 ret = PTR_ERR(chan_file);
 192                 goto file_error;
 193         }
 194         switch (channel_type) {
 195         case PER_CPU_CHANNEL:
 196                 transport_name = chan_param.overwrite ?
 197                         "relay-overwrite" : "relay-discard";
 198                 fops = &lttng_channel_fops;
 199                 break;
 200         case METADATA_CHANNEL:
 201                 transport_name = "relay-metadata";
 202                 fops = &lttng_metadata_fops;
 203                 break;
 204         default:
 205                 transport_name = "<unknown>";
 206                 break;
 207         }
 208         /*
 209          * We tolerate no failure path after channel creation. It will stay
 210          * invariant for the rest of the session.
 211          */
 212         chan = ltt_channel_create(session, transport_name, NULL,
 213                                   chan_param.subbuf_size,
 214                                   chan_param.num_subbuf,
 215                                   chan_param.switch_timer_interval,
 216                                   chan_param.read_timer_interval);
 217         if (!chan) {
 218                 ret = -EINVAL;
 219                 goto chan_error;
 220         }
 221         chan->file = chan_file;
 222         chan_file->private_data = chan;
 223         fd_install(chan_fd, chan_file);
 224         if (channel_type == METADATA_CHANNEL) {
 225                 lttng_metadata_create_events(chan_file);
 226                 session->metadata = chan;
 227         }
 228
 229         /* The channel created holds a reference on the session */
 230         atomic_long_inc(&session_file->f_count);
 231
 232         return chan_fd;
 233
 234 chan_error:
 235         fput(chan_file);
 236 file_error:
 237         put_unused_fd(chan_fd);
 238 fd_error:
 239         return ret;
 240 }
 241
 242 /**
 243  *      lttng_session_ioctl - lttng session fd ioctl
 244  *
 245  *      @file: the file
 246  *      @cmd: the command
 247  *      @arg: command arg
 248  *
 249  *      This ioctl implements lttng commands:
 250  *      LTTNG_KERNEL_CHANNEL
 251  *              Returns a LTTng channel file descriptor
 252  *
 253  * The returned channel will be deleted when its file descriptor is closed.
 254  */
 255 static
 256 long lttng_session_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 257 {
 258         struct ltt_session *session = file->private_data;
 259
 260         switch (cmd) {
 261         case LTTNG_KERNEL_CHANNEL:
 262                 return lttng_abi_create_channel(file,
 263                                 (struct lttng_kernel_channel __user *) arg,
 264                                 PER_CPU_CHANNEL);
 265         case LTTNG_KERNEL_SESSION_START:
 266                 return ltt_session_start(session);
 267         case LTTNG_KERNEL_SESSION_STOP:
 268                 return ltt_session_stop(session);
 269         case LTTNG_KERNEL_METADATA:
 270                 return lttng_abi_create_channel(file,
 271                                 (struct lttng_kernel_channel __user *) arg,
 272                                 METADATA_CHANNEL);
 273         default:
 274                 return -ENOIOCTLCMD;
 275         }
 276 }
 277
 278 /*
 279  * Called when the last file reference is dropped.
 280  *
 281  * Big fat note: channels and events are invariant for the whole session after
 282  * their creation. So this session destruction also destroys all channel and
 283  * event structures specific to this session (they are not destroyed when their
 284  * individual file is released).
 285  */
 286 static
 287 int lttng_session_release(struct inode *inode, struct file *file)
 288 {
 289         struct ltt_session *session = file->private_data;
 290
 291         if (session)
 292                 ltt_session_destroy(session);
 293         return 0;
 294 }
 295
 296 static const struct file_operations lttng_session_fops = {
 297         .release = lttng_session_release,
 298         .unlocked_ioctl = lttng_session_ioctl,
 299 #ifdef CONFIG_COMPAT
 300         .compat_ioctl = lttng_session_ioctl,
 301 #endif
 302 };
 303
 304 static
 305 int lttng_abi_open_stream(struct file *channel_file)
 306 {
 307         struct ltt_channel *channel = channel_file->private_data;
 308         struct lib_ring_buffer *buf;
 309         int stream_fd, ret;
 310         struct file *stream_file;
 311
 312         buf = channel->ops->buffer_read_open(channel->chan);
 313         if (!buf)
 314                 return -ENOENT;
 315
 316         stream_fd = get_unused_fd();
 317         if (stream_fd < 0) {
 318                 ret = stream_fd;
 319                 goto fd_error;
 320         }
 321         stream_file = anon_inode_getfile("[lttng_stream]",
 322                                          &lib_ring_buffer_file_operations,
 323                                          buf, O_RDWR);
 324         if (IS_ERR(stream_file)) {
 325                 ret = PTR_ERR(stream_file);
 326                 goto file_error;
 327         }
 328         /*
 329          * OPEN_FMODE, called within anon_inode_getfile/alloc_file, don't honor
 330          * FMODE_LSEEK, FMODE_PREAD nor FMODE_PWRITE. We need to read from this
 331          * file descriptor, so we set FMODE_PREAD here.
 332          */
 333         stream_file->f_mode |= FMODE_PREAD;
 334         fd_install(stream_fd, stream_file);
 335         /*
 336          * The stream holds a reference to the channel within the generic ring
 337          * buffer library, so no need to hold a refcount on the channel and
 338          * session files here.
 339          */
 340         return stream_fd;
 341
 342 file_error:
 343         put_unused_fd(stream_fd);
 344 fd_error:
 345         channel->ops->buffer_read_close(buf);
 346         return ret;
 347 }
 348
 349 static
 350 int lttng_abi_create_event(struct file *channel_file,
 351                            struct lttng_kernel_event __user *uevent_param)
 352 {
 353         struct ltt_channel *channel = channel_file->private_data;
 354         struct ltt_event *event;
 355         char *event_name;
 356         struct lttng_kernel_event event_param;
 357         int event_fd, ret;
 358         struct file *event_file;
 359
 360         if (copy_from_user(&event_param, uevent_param, sizeof(event_param)))
 361                 return -EFAULT;
 362         event_name = kmalloc(PATH_MAX, GFP_KERNEL);
 363         if (!event_name)
 364                 return -ENOMEM;
 365         if (strncpy_from_user(event_name, uevent_param->name, PATH_MAX) < 0) {
 366                 ret = -EFAULT;
 367                 goto name_error;
 368         }
 369         event_name[PATH_MAX - 1] = '\0';
 370         event_param.u.kprobe.symbol_name[LTTNG_KPROBE_SYM_NAME_LEN - 1] = '\0';
 371
 372         event_fd = get_unused_fd();
 373         if (event_fd < 0) {
 374                 ret = event_fd;
 375                 goto fd_error;
 376         }
 377         event_file = anon_inode_getfile("[lttng_event]",
 378                                         &lttng_event_fops,
 379                                         NULL, O_RDWR);
 380         if (IS_ERR(event_file)) {
 381                 ret = PTR_ERR(event_file);
 382                 goto file_error;
 383         }
 384         /*
 385          * We tolerate no failure path after event creation. It will stay
 386          * invariant for the rest of the session.
 387          */
 388         event = ltt_event_create(channel, event_name, &event_param, NULL);
 389         if (!event) {
 390                 ret = -EEXIST;
 391                 goto event_error;
 392         }
 393         event_file->private_data = event;
 394         fd_install(event_fd, event_file);
 395         /* The event holds a reference on the channel */
 396         atomic_long_inc(&channel_file->f_count);
 397         kfree(event_name);
 398         return event_fd;
 399
 400 event_error:
 401         fput(event_file);
 402 file_error:
 403         put_unused_fd(event_fd);
 404 fd_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_KERNEL_STREAM
 419  *              Returns an event stream file descriptor or failure.
 420  *              (typically, one event stream records events from one CPU)
 421  *      LTTNG_KERNEL_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_KERNEL_STREAM:
 431                 return lttng_abi_open_stream(file);
 432         case LTTNG_KERNEL_EVENT:
 433                 return lttng_abi_create_event(file, (struct lttng_kernel_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_KERNEL_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_KERNEL_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                 ltt_event_unregister(event);
 528                 fput(event->chan->file);
 529         }
 530         return 0;
 531 }
 532
 533 /* TODO: filter control ioctl */
 534 static const struct file_operations lttng_event_fops = {
 535         .release = lttng_event_release,
 536 };
 537
 538 int __init ltt_debugfs_abi_init(void)
 539 {
 540         int ret = 0;
 541
 542         wrapper_vmalloc_sync_all();
 543         lttng_dentry = debugfs_create_file("lttng", S_IWUSR, NULL, NULL,
 544                                            &lttng_fops);
 545         if (IS_ERR(lttng_dentry) || !lttng_dentry) {
 546                 printk(KERN_ERR "Error creating LTTng control file\n");
 547                 ret = -ENOMEM;
 548                 goto error;
 549         }
 550 error:
 551         return ret;
 552 }
 553
 554 void __exit ltt_debugfs_abi_exit(void)
 555 {
 556         debugfs_remove(lttng_dentry);
 557 }