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();
  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();
 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_long_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
 206         if (session)
 207                 ltt_session_destroy(session);
 208         return 0;
 209 }
 210
 211 static const struct file_operations lttng_session_fops = {
 212         .release = lttng_session_release,
 213         .unlocked_ioctl = lttng_session_ioctl,
 214 #ifdef CONFIG_COMPAT
 215         .compat_ioctl = lttng_session_ioctl,
 216 #endif
 217 };
 218
 219 static
 220 int lttng_abi_open_stream(struct file *channel_file)
 221 {
 222         struct ltt_channel *channel = channel_file->private_data;
 223         struct lib_ring_buffer *buf;
 224         int stream_fd, ret;
 225         struct file *stream_file;
 226
 227         buf = channel->ops->buffer_read_open(channel->chan);
 228         if (!buf)
 229                 return -ENOENT;
 230
 231         stream_fd = get_unused_fd();
 232         if (stream_fd < 0) {
 233                 ret = stream_fd;
 234                 goto fd_error;
 235         }
 236         stream_file = anon_inode_getfile("[lttng_stream]",
 237                                          &lib_ring_buffer_file_operations,
 238                                          buf, O_RDWR);
 239         if (IS_ERR(stream_file)) {
 240                 ret = PTR_ERR(stream_file);
 241                 goto file_error;
 242         }
 243         fd_install(stream_fd, stream_file);
 244         /* The stream holds a reference on the channel */
 245         atomic_long_inc(&channel_file->f_count);
 246         return stream_fd;
 247
 248 file_error:
 249         put_unused_fd(stream_fd);
 250 fd_error:
 251         channel->ops->buffer_read_close(buf);
 252         return ret;
 253 }
 254
 255 static
 256 int lttng_abi_create_event(struct file *channel_file,
 257                            struct lttng_event __user *uevent_param)
 258 {
 259         struct ltt_channel *channel = channel_file->private_data;
 260         struct ltt_event *event;
 261         char *event_name;
 262         struct lttng_event event_param;
 263         int event_fd, ret;
 264         struct file *event_file;
 265
 266         if (copy_from_user(&event_param, uevent_param, sizeof(event_param)))
 267                 return -EFAULT;
 268         event_name = kmalloc(PATH_MAX, GFP_KERNEL);
 269         if (!event_name)
 270                 return -ENOMEM;
 271         if (strncpy_from_user(event_name, uevent_param->name, PATH_MAX)) {
 272                 ret = -EFAULT;
 273                 goto name_error;
 274         }
 275         event_name[PATH_MAX - 1] = '\0';
 276         event_fd = get_unused_fd();
 277         if (event_fd < 0) {
 278                 ret = event_fd;
 279                 goto fd_error;
 280         }
 281         event_file = anon_inode_getfile("[lttng_event]",
 282                                         &lttng_event_fops,
 283                                         NULL, O_RDWR);
 284         if (IS_ERR(event_file)) {
 285                 ret = PTR_ERR(event_file);
 286                 goto file_error;
 287         }
 288         /*
 289          * We tolerate no failure path after event creation. It will stay
 290          * invariant for the rest of the session.
 291          */
 292         event = ltt_event_create(channel, event_name, event_param.itype,
 293                                  NULL, NULL);   /* TODO non-null probe */
 294         if (!event) {
 295                 goto event_error;
 296                 ret = -EEXIST;
 297         }
 298         event_file->private_data = event;
 299         fd_install(event_fd, event_file);
 300         /* The event holds a reference on the channel */
 301         atomic_long_inc(&channel_file->f_count);
 302         kfree(event_name);
 303         return event_fd;
 304
 305 event_error:
 306         fput(event_file);
 307 file_error:
 308         put_unused_fd(event_fd);
 309 fd_error:
 310 name_error:
 311         kfree(event_name);
 312         return ret;
 313 }
 314
 315 /**
 316  *      lttng_channel_ioctl - lttng syscall through ioctl
 317  *
 318  *      @file: the file
 319  *      @cmd: the command
 320  *      @arg: command arg
 321  *
 322  *      This ioctl implements lttng commands:
 323  *      LTTNG_STREAM
 324  *              Returns an event stream file descriptor or failure.
 325  *              (typically, one event stream records events from one CPU)
 326  *      LTTNG_EVENT
 327  *              Returns an event file descriptor or failure.
 328  *
 329  * The returned session will be deleted when its file descriptor is closed.
 330  * Channel and event file descriptors also hold a reference on the session.
 331  */
 332 static
 333 long lttng_channel_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 334 {
 335         switch (cmd) {
 336         case LTTNG_STREAM:
 337                 return lttng_abi_open_stream(file);
 338         case LTTNG_EVENT:
 339                 return lttng_abi_create_event(file, (struct lttng_event __user *)arg);
 340         default:
 341                 return -ENOIOCTLCMD;
 342         }
 343 }
 344
 345 /* TODO: poll */
 346 #if 0
 347 /**
 348  *      lttng_channel_poll - lttng stream addition/removal monitoring
 349  *
 350  *      @file: the file
 351  *      @wait: poll table
 352  */
 353 unsigned int lttng_channel_poll(struct file *file, poll_table *wait)
 354 {
 355         struct ltt_channel *channel = file->private_data;
 356         unsigned int mask = 0;
 357
 358         if (file->f_mode & FMODE_READ) {
 359                 poll_wait_set_exclusive(wait);
 360                 poll_wait(file, &channel->notify_wait, wait);
 361
 362                 /* TODO: identify when the channel is being finalized. */
 363                 if (finalized)
 364                         return POLLHUP;
 365                 else
 366                         return POLLIN | POLLRDNORM;
 367         }
 368         return mask;
 369
 370 }
 371 #endif //0
 372
 373 static
 374 int lttng_channel_release(struct inode *inode, struct file *file)
 375 {
 376         struct ltt_channel *channel = file->private_data;
 377
 378         if (channel)
 379                 fput(channel->session->file);
 380         return 0;
 381 }
 382
 383 static const struct file_operations lttng_channel_fops = {
 384         .release = lttng_channel_release,
 385 /* TODO */
 386 #if 0
 387         .poll = lttng_channel_poll,
 388 #endif //0
 389         .unlocked_ioctl = lttng_channel_ioctl,
 390 #ifdef CONFIG_COMPAT
 391         .compat_ioctl = lttng_channel_ioctl,
 392 #endif
 393 };
 394
 395 static
 396 int lttng_event_release(struct inode *inode, struct file *file)
 397 {
 398         struct ltt_event *event = file->private_data;
 399
 400         if (event)
 401                 fput(event->chan->file);
 402         return 0;
 403 }
 404
 405 /* TODO: filter control ioctl */
 406 static const struct file_operations lttng_event_fops = {
 407         .release = lttng_event_release,
 408 };
 409
 410 int __init ltt_debugfs_abi_init(void)
 411 {
 412         int ret = 0;
 413
 414         lttng_dentry = debugfs_create_file("lttng", S_IWUSR, NULL, NULL,
 415                                            &lttng_session_fops);
 416         if (IS_ERR(lttng_dentry) || !lttng_dentry) {
 417                 printk(KERN_ERR "Error creating LTTng control file\n");
 418                 ret = -ENOMEM;
 419                 goto error;
 420         }
 421 error:
 422         return ret;
 423 }
 424
 425 void __exit ltt_debugfs_abi_exit(void)
 426 {
 427         debugfs_remove(lttng_dentry);
 428 }