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 = -EINVAL;
 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         /*
 244          * OPEN_FMODE, called within anon_inode_getfile/alloc_file, don't honor
 245          * FMODE_LSEEK, FMODE_PREAD nor FMODE_PWRITE. We need to read from this
 246          * file descriptor, so we set FMODE_PREAD here.
 247          */
 248         stream_file->f_mode |= FMODE_PREAD;
 249         fd_install(stream_fd, stream_file);
 250         /*
 251          * The stream holds a reference to the channel within the generic ring
 252          * buffer library, so no need to hold a refcount on the channel and
 253          * session files here.
 254          */
 255         return stream_fd;
 256
 257 file_error:
 258         put_unused_fd(stream_fd);
 259 fd_error:
 260         channel->ops->buffer_read_close(buf);
 261         return ret;
 262 }
 263
 264 static
 265 int lttng_abi_create_event(struct file *channel_file,
 266                            struct lttng_event __user *uevent_param)
 267 {
 268         struct ltt_channel *channel = channel_file->private_data;
 269         struct ltt_event *event;
 270         char *event_name;
 271         struct lttng_event event_param;
 272         int event_fd, ret;
 273         struct file *event_file;
 274         void *probe;
 275
 276         if (copy_from_user(&event_param, uevent_param, sizeof(event_param)))
 277                 return -EFAULT;
 278         event_name = kmalloc(PATH_MAX, GFP_KERNEL);
 279         if (!event_name)
 280                 return -ENOMEM;
 281         if (strncpy_from_user(event_name, uevent_param->name, PATH_MAX) < 0) {
 282                 ret = -EFAULT;
 283                 goto name_error;
 284         }
 285         event_name[PATH_MAX - 1] = '\0';
 286
 287         probe = ltt_probe_get(event_name);
 288         if (!probe) {
 289                 ret = -ENOENT;
 290                 goto probe_error;
 291         }
 292         event_fd = get_unused_fd();
 293         if (event_fd < 0) {
 294                 ret = event_fd;
 295                 goto fd_error;
 296         }
 297         event_file = anon_inode_getfile("[lttng_event]",
 298                                         &lttng_event_fops,
 299                                         NULL, O_RDWR);
 300         if (IS_ERR(event_file)) {
 301                 ret = PTR_ERR(event_file);
 302                 goto file_error;
 303         }
 304         /*
 305          * We tolerate no failure path after event creation. It will stay
 306          * invariant for the rest of the session.
 307          */
 308         event = ltt_event_create(channel, event_name, event_param.itype,
 309                                  probe, NULL);
 310         if (!event) {
 311                 goto event_error;
 312                 ret = -EEXIST;
 313         }
 314         event_file->private_data = event;
 315         fd_install(event_fd, event_file);
 316         /* The event holds a reference on the channel */
 317         atomic_long_inc(&channel_file->f_count);
 318         kfree(event_name);
 319         return event_fd;
 320
 321 event_error:
 322         fput(event_file);
 323 file_error:
 324         put_unused_fd(event_fd);
 325 fd_error:
 326         ltt_probe_put(probe);
 327 probe_error:
 328 name_error:
 329         kfree(event_name);
 330         return ret;
 331 }
 332
 333 /**
 334  *      lttng_channel_ioctl - lttng syscall through ioctl
 335  *
 336  *      @file: the file
 337  *      @cmd: the command
 338  *      @arg: command arg
 339  *
 340  *      This ioctl implements lttng commands:
 341  *      LTTNG_STREAM
 342  *              Returns an event stream file descriptor or failure.
 343  *              (typically, one event stream records events from one CPU)
 344  *      LTTNG_EVENT
 345  *              Returns an event file descriptor or failure.
 346  *
 347  * The returned session will be deleted when its file descriptor is closed.
 348  * Channel and event file descriptors also hold a reference on the session.
 349  */
 350 static
 351 long lttng_channel_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 352 {
 353         switch (cmd) {
 354         case LTTNG_STREAM:
 355                 return lttng_abi_open_stream(file);
 356         case LTTNG_EVENT:
 357                 return lttng_abi_create_event(file, (struct lttng_event __user *)arg);
 358         default:
 359                 return -ENOIOCTLCMD;
 360         }
 361 }
 362
 363 /* TODO: poll */
 364 #if 0
 365 /**
 366  *      lttng_channel_poll - lttng stream addition/removal monitoring
 367  *
 368  *      @file: the file
 369  *      @wait: poll table
 370  */
 371 unsigned int lttng_channel_poll(struct file *file, poll_table *wait)
 372 {
 373         struct ltt_channel *channel = file->private_data;
 374         unsigned int mask = 0;
 375
 376         if (file->f_mode & FMODE_READ) {
 377                 poll_wait_set_exclusive(wait);
 378                 poll_wait(file, &channel->notify_wait, wait);
 379
 380                 /* TODO: identify when the channel is being finalized. */
 381                 if (finalized)
 382                         return POLLHUP;
 383                 else
 384                         return POLLIN | POLLRDNORM;
 385         }
 386         return mask;
 387
 388 }
 389 #endif //0
 390
 391 static
 392 int lttng_channel_release(struct inode *inode, struct file *file)
 393 {
 394         struct ltt_channel *channel = file->private_data;
 395
 396         if (channel)
 397                 fput(channel->session->file);
 398         return 0;
 399 }
 400
 401 static const struct file_operations lttng_channel_fops = {
 402         .release = lttng_channel_release,
 403 /* TODO */
 404 #if 0
 405         .poll = lttng_channel_poll,
 406 #endif //0
 407         .unlocked_ioctl = lttng_channel_ioctl,
 408 #ifdef CONFIG_COMPAT
 409         .compat_ioctl = lttng_channel_ioctl,
 410 #endif
 411 };
 412
 413 static
 414 int lttng_event_release(struct inode *inode, struct file *file)
 415 {
 416         struct ltt_event *event = file->private_data;
 417
 418         if (event)
 419                 fput(event->chan->file);
 420         return 0;
 421 }
 422
 423 /* TODO: filter control ioctl */
 424 static const struct file_operations lttng_event_fops = {
 425         .release = lttng_event_release,
 426 };
 427
 428 int __init ltt_debugfs_abi_init(void)
 429 {
 430         int ret = 0;
 431
 432         lttng_dentry = debugfs_create_file("lttng", S_IWUSR, NULL, NULL,
 433                                            &lttng_fops);
 434         if (IS_ERR(lttng_dentry) || !lttng_dentry) {
 435                 printk(KERN_ERR "Error creating LTTng control file\n");
 436                 ret = -ENOMEM;
 437                 goto error;
 438         }
 439 error:
 440         return ret;
 441 }
 442
 443 void __exit ltt_debugfs_abi_exit(void)
 444 {
 445         debugfs_remove(lttng_dentry);
 446 }