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_event_fops;
  45
  46 static
  47 int lttng_abi_create_session(void)
  48 {
  49         struct ltt_session *session;
  50         struct file *session_file;
  51         int session_fd, ret;
  52
  53         session = ltt_session_create();
  54         if (!session)
  55                 return -ENOMEM;
  56         session_fd = get_unused_fd_flags(O_RDWR);
  57         if (session_fd < 0) {
  58                 ret = session_fd;
  59                 goto fd_error;
  60         }
  61         session_file = anon_inode_getfile("[lttng_session]",
  62                                           &lttng_session_fops,
  63                                           session, O_RDWR);
  64         if (IS_ERR(session_file)) {
  65                 ret = PTR_ERR(session_file);
  66                 goto file_error;
  67         }
  68         session->file = session_file;
  69         fd_install(session_fd, session_file);
  70         return session_fd;
  71
  72 file_error:
  73         put_unused_fd(session_fd);
  74 fd_error:
  75         ltt_session_destroy(session);
  76         return ret;
  77 }
  78
  79 /**
  80  *      lttng_ioctl - lttng syscall through ioctl
  81  *
  82  *      @file: the file
  83  *      @cmd: the command
  84  *      @arg: command arg
  85  *
  86  *      This ioctl implements lttng commands:
  87  *      LTTNG_SESSION
  88  *              Returns a LTTng trace session file descriptor
  89  *
  90  * The returned session will be deleted when its file descriptor is closed.
  91  */
  92 static
  93 long lttng_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
  94 {
  95         switch (cmd) {
  96         case LTTNG_SESSION:
  97                 return lttng_abi_create_session();
  98         default:
  99                 return -ENOIOCTLCMD;
 100         }
 101 }
 102
 103 static const struct file_operations lttng_fops = {
 104         .unlocked_ioctl = lttng_ioctl,
 105 #ifdef CONFIG_COMPAT
 106         .compat_ioctl = lttng_ioctl,
 107 #endif
 108 };
 109
 110 int lttng_abi_create_channel(struct file *session_file,
 111                              struct lttng_channel __user *uchan_param)
 112 {
 113         struct ltt_session *session = session_file->private_data;
 114         struct ltt_channel *chan;
 115         struct file *chan_file;
 116         struct lttng_channel chan_param;
 117         int chan_fd;
 118         int ret = 0;
 119
 120         if (copy_from_user(&chan_param, uchan_param, sizeof(chan_param)))
 121                 return -EFAULT;
 122         chan_fd = get_unused_fd_flags(O_RDWR);
 123         if (chan_fd < 0) {
 124                 ret = chan_fd;
 125                 goto fd_error;
 126         }
 127         chan_file = anon_inode_getfile("[lttng_channel]",
 128                                        &lttng_channel_fops,
 129                                        NULL, O_RDWR);
 130         if (IS_ERR(chan_file)) {
 131                 ret = PTR_ERR(chan_file);
 132                 goto file_error;
 133         }
 134         /*
 135          * We tolerate no failure path after channel creation. It will stay
 136          * invariant for the rest of the session.
 137          */
 138         chan = ltt_channel_create(session, chan_param.overwrite, NULL,
 139                                   chan_param.subbuf_size,
 140                                   chan_param.num_subbuf,
 141                                   chan_param.switch_timer_interval,
 142                                   chan_param.read_timer_interval);
 143         if (!chan) {
 144                 ret = -ENOMEM;
 145                 goto chan_error;
 146         }
 147         chan->file = chan_file;
 148         chan_file->private_data = chan;
 149         fd_install(chan_fd, chan_file);
 150         /* The channel created holds a reference on the session */
 151         atomic_inc(&session_file->f_count);
 152
 153         return chan_fd;
 154
 155 chan_error:
 156         fput(chan_file);
 157 file_error:
 158         put_unused_fd(chan_fd);
 159 fd_error:
 160         return ret;
 161 }
 162
 163 /**
 164  *      lttng_session_ioctl - lttng session fd ioctl
 165  *
 166  *      @file: the file
 167  *      @cmd: the command
 168  *      @arg: command arg
 169  *
 170  *      This ioctl implements lttng commands:
 171  *      LTTNG_CHANNEL
 172  *              Returns a LTTng channel file descriptor
 173  *
 174  * The returned channel will be deleted when its file descriptor is closed.
 175  */
 176 static
 177 long lttng_session_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 178 {
 179         struct ltt_session *session = file->private_data;
 180
 181         switch (cmd) {
 182         case LTTNG_CHANNEL:
 183                 return lttng_abi_create_channel(file, (struct lttng_channel __user *)arg);
 184         case LTTNG_SESSION_START:
 185                 return ltt_session_start(session);
 186         case LTTNG_SESSION_STOP:
 187                 return ltt_session_stop(session);
 188         default:
 189                 return -ENOIOCTLCMD;
 190         }
 191 }
 192
 193 /*
 194  * Called when the last file reference is dropped.
 195  *
 196  * Big fat note: channels and events are invariant for the whole session after
 197  * their creation. So this session destruction also destroys all channel and
 198  * event structures specific to this session (they are not destroyed when their
 199  * individual file is released).
 200  */
 201 static
 202 int lttng_session_release(struct inode *inode, struct file *file)
 203 {
 204         struct ltt_session *session = file->private_data;
 205         ltt_session_destroy(session);
 206         return 0;
 207 }
 208
 209 static const struct file_operations lttng_session_fops = {
 210         .release = lttng_session_release,
 211         .unlocked_ioctl = lttng_session_ioctl,
 212 #ifdef CONFIG_COMPAT
 213         .compat_ioctl = lttng_session_ioctl,
 214 #endif
 215 };
 216
 217 static
 218 int lttng_abi_open_stream(struct file *channel_file)
 219 {
 220         struct ltt_channel *channel = channel_file->private_data;
 221         struct lib_ring_buffer *buf;
 222         int stream_fd, ret;
 223         struct file *stream_file;
 224
 225         buf = channel->ops->buffer_read_open(channel->chan);
 226         if (!buf)
 227                 return -ENOENT;
 228
 229         stream_fd = get_unused_fd_flags(O_RDWR);
 230         if (stream_fd < 0) {
 231                 ret = stream_fd;
 232                 goto fd_error;
 233         }
 234         stream_file = anon_inode_getfile("[lttng_stream]",
 235                                          &lib_ring_buffer_file_operations,
 236                                          buf, O_RDWR);
 237         if (IS_ERR(stream_file)) {
 238                 ret = PTR_ERR(stream_file);
 239                 goto file_error;
 240         }
 241         fd_install(stream_fd, stream_file);
 242         /* The stream holds a reference on the channel */
 243         atomic_inc(&channel_file->f_count);
 244         return stream_fd;
 245
 246 file_error:
 247         put_unused_fd(stream_fd);
 248 fd_error:
 249         channel->ops->buffer_read_close(buf);
 250         return ret;
 251 }
 252
 253 static
 254 int lttng_abi_create_event(struct file *channel_file,
 255                            struct lttng_event __user *uevent_param)
 256 {
 257         struct ltt_channel *channel = channel_file->private_data;
 258         struct ltt_event *event;
 259         char *event_name;
 260         struct lttng_event event_param;
 261         int event_fd, ret;
 262         struct file *event_file;
 263
 264         if (copy_from_user(&event_param, uevent_param, sizeof(event_param)))
 265                 return -EFAULT;
 266         event_name = kmalloc(PATH_MAX, GFP_KERNEL);
 267         if (!event_name)
 268                 return -ENOMEM;
 269         if (strncpy_from_user(event_name, uevent_param->name, PATH_MAX)) {
 270                 ret = -EFAULT;
 271                 goto name_error;
 272         }
 273         event_name[PATH_MAX - 1] = '\0';
 274         event_fd = get_unused_fd_flags(O_RDWR);
 275         if (event_fd < 0) {
 276                 ret = event_fd;
 277                 goto fd_error;
 278         }
 279         event_file = anon_inode_getfile("[lttng_event]",
 280                                         &lttng_event_fops,
 281                                         NULL, O_RDWR);
 282         if (IS_ERR(event_file)) {
 283                 ret = PTR_ERR(event_file);
 284                 goto file_error;
 285         }
 286         /*
 287          * We tolerate no failure path after event creation. It will stay
 288          * invariant for the rest of the session.
 289          */
 290         event = ltt_event_create(channel, event_name, event_param.itype,
 291                                  NULL, NULL);   /* TODO non-null probe */
 292         if (!event) {
 293                 goto event_error;
 294                 ret = -EEXIST;
 295         }
 296         event_file->private_data = event;
 297         fd_install(event_fd, event_file);
 298         /* The event holds a reference on the channel */
 299         atomic_inc(&channel_file->f_count);
 300         kfree(event_name);
 301         return event_fd;
 302
 303 event_error:
 304         fput(event_file);
 305 file_error:
 306         put_unused_fd(event_fd);
 307 fd_error:
 308 name_error:
 309         kfree(event_name);
 310         return ret;
 311 }
 312
 313 /**
 314  *      lttng_channel_ioctl - lttng syscall through ioctl
 315  *
 316  *      @file: the file
 317  *      @cmd: the command
 318  *      @arg: command arg
 319  *
 320  *      This ioctl implements lttng commands:
 321  *      LTTNG_STREAM
 322  *              Returns an event stream file descriptor or failure.
 323  *              (typically, one event stream records events from one CPU)
 324  *      LTTNG_EVENT
 325  *              Returns an event file descriptor or failure.
 326  *
 327  * The returned session will be deleted when its file descriptor is closed.
 328  * Channel and event file descriptors also hold a reference on the session.
 329  */
 330 static
 331 long lttng_channel_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 332 {
 333         switch (cmd) {
 334         case LTTNG_STREAM:
 335                 return lttng_abi_open_stream(file);
 336         case LTTNG_EVENT:
 337                 return lttng_abi_create_event(file, (struct lttng_event __user *)arg);
 338         default:
 339                 return -ENOIOCTLCMD;
 340         }
 341 }
 342
 343 /* TODO: poll */
 344 #if 0
 345 /**
 346  *      lttng_channel_poll - lttng stream addition/removal monitoring
 347  *
 348  *      @file: the file
 349  *      @wait: poll table
 350  */
 351 unsigned int lttng_channel_poll(struct file *file, poll_table *wait)
 352 {
 353         struct ltt_channel *channel = file->private_data;
 354         unsigned int mask = 0;
 355
 356         if (file->f_mode & FMODE_READ) {
 357                 poll_wait_set_exclusive(wait);
 358                 poll_wait(file, &channel->notify_wait, wait);
 359
 360                 /* TODO: identify when the channel is being finalized. */
 361                 if (finalized)
 362                         return POLLHUP;
 363                 else
 364                         return POLLIN | POLLRDNORM;
 365         }
 366         return mask;
 367
 368 }
 369 #endif //0
 370
 371 static
 372 int lttng_channel_release(struct inode *inode, struct file *file)
 373 {
 374         struct ltt_channel *channel = file->private_data;
 375         fput(channel->session->file);
 376         return 0;
 377 }
 378
 379 static const struct file_operations lttng_channel_fops = {
 380         .release = lttng_channel_release,
 381 /* TODO */
 382 #if 0
 383         .poll = lttng_channel_poll,
 384 #endif //0
 385         .unlocked_ioctl = lttng_channel_ioctl,
 386 #ifdef CONFIG_COMPAT
 387         .compat_ioctl = lttng_channel_ioctl,
 388 #endif
 389 };
 390
 391 static
 392 int lttng_event_release(struct inode *inode, struct file *file)
 393 {
 394         struct ltt_event *event = file->private_data;
 395         fput(event->chan->file);
 396         return 0;
 397 }
 398
 399 /* TODO: filter control ioctl */
 400 static const struct file_operations lttng_event_fops = {
 401         .release = lttng_event_release,
 402 };
 403
 404 static int __init ltt_debugfs_abi_init(void)
 405 {
 406         int ret = 0;
 407
 408         lttng_dentry = debugfs_create_file("lttng", S_IWUSR, NULL, NULL,
 409                                            &lttng_session_fops);
 410         if (IS_ERR(lttng_dentry) || !lttng_dentry) {
 411                 printk(KERN_ERR "Error creating LTTng control file\n");
 412                 ret = -ENOMEM;
 413                 goto error;
 414         }
 415 error:
 416         return ret;
 417 }
 418
 419 module_init(ltt_debugfs_abi_init);
 420
 421 static void __exit ltt_debugfs_abi_exit(void)
 422 {
 423         debugfs_remove(lttng_dentry);
 424 }
 425
 426 module_exit(ltt_debugfs_abi_exit);
 427
 428 MODULE_LICENSE("GPL and additional rights");
 429 MODULE_AUTHOR("Mathieu Desnoyers");
 430 MODULE_DESCRIPTION("Linux Trace Toolkit Next Generation DebugFS ABI");