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/debugfs.h>
  26 #include "ltt-events.h"
  27
  28 /*
  29  * This is LTTng's own personal way to create a system call as an external
  30  * module. We use ioctl() on /sys/kernel/debug/lttng.
  31  */
  32
  33 static struct dentry *lttng_dentry;
  34 static const struct file_operations lttng_fops;
  35 static const struct file_operations lttng_session_fops;
  36 static const struct file_operations lttng_channel_fops;
  37 static const struct file_operations lttng_event_fops;
  38
  39 /*
  40  * LTTng DebugFS ABI structures.
  41  */
  42
  43 struct lttng_channel {
  44         int overwrite;                  /* 1: overwrite, 0: discard */
  45         u64 subbuf_size;
  46         u64 num_subbuf;
  47         unsigned int switch_timer_interval;
  48         unsigned int read_timer_interval;
  49 };
  50
  51 struct lttng_event {
  52         enum instrum_type itype;
  53         char name[];
  54 };
  55
  56 static
  57 int lttng_abi_create_session(void)
  58 {
  59         struct ltt_session *session;
  60         struct file *session_filp;
  61         int session_fd;
  62
  63         session = ltt_session_create();
  64         if (!session)
  65                 return -ENOMEM;
  66         session_fd = get_unused_fd_flags(O_RDWR);
  67         if (session_fd < 0) {
  68                 ret = session_fd;
  69                 goto fd_error;
  70         }
  71         session_filp = anon_inode_getfile("[lttng_session]",
  72                                           &lttng_session_fops,
  73                                           session, O_RDWR);
  74         if (IS_ERR(session_filp)) {
  75                 ret = PTR_ERR(session_filp);
  76                 goto file_error;
  77         }
  78         fd_install(session_fd, session_filp);
  79         return session_fd;
  80
  81 file_error:
  82         put_unused_fd(session_fd);
  83 fd_error:
  84         ltt_session_destroy(session);
  85         return ret;
  86 }
  87
  88 /**
  89  *      lttng_ioctl - lttng syscall through ioctl
  90  *
  91  *      @filp: the file
  92  *      @cmd: the command
  93  *      @arg: command arg
  94  *
  95  *      This ioctl implements lttng commands:
  96  *      LTTNG_SESSION
  97  *              Returns a LTTng trace session file descriptor
  98  *
  99  * The returned session will be deleted when its file descriptor is closed.
 100  */
 101 static
 102 long lttng_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 103 {
 104         switch (cmd) {
 105         case LTTNG_SESSION:
 106                 return lttng_abi_create_session();
 107         default:
 108                 return -ENOIOCTLCMD;
 109         }
 110 }
 111
 112 static const struct file_operations lttng_fops = {
 113         .unlocked_ioctl = lttng_ioctl,
 114 #ifdef CONFIG_COMPAT
 115         .compat_ioctl = lttng_ioctl,
 116 #endif
 117 }
 118
 119 int lttng_abi_create_channel(struct file *session_filp,
 120                              struct lttng_channel __user *uchan_param)
 121 {
 122         struct ltt_session *session = session_filp->private_data;
 123         struct ltt_channel *chan;
 124         struct file *chan_filp;
 125         struct lttng_channel chan_param;
 126         int chan_fd;
 127         int ret = 0;
 128
 129         if (copy_from_user(&chan_param, uchan_param, sizeof(chan_param)))
 130                 return -EFAULT;
 131         chan_fd = get_unused_fd_flags(O_RDWR);
 132         if (chan_fd < 0) {
 133                 ret = chan_fd;
 134                 goto fd_error;
 135         }
 136         chan_filp = anon_inode_getfile("[lttng_channel]",
 137                                        &lttng_channel_fops,
 138                                        NULL, O_RDWR);
 139         if (IS_ERR(chan_filp)) {
 140                 ret = PTR_ERR(chan_filp);
 141                 goto file_error;
 142         }
 143         /*
 144          * We tolerate no failure path after channel creation. It will stay
 145          * invariant for the rest of the session.
 146          */
 147         chan = ltt_channel_create(session, chan_param->overwrite, NULL,
 148                                   chan_param->subbuf_size,
 149                                   chan_param->num_subbuf,
 150                                   chan_param->switch_timer_interval,
 151                                   chan_param->read_timer_interval);
 152         if (!chan) {
 153                 ret = -ENOMEM;
 154                 goto chan_error;
 155         }
 156         chan_filp->private_data = chan;
 157         fd_install(chan_fd, chan_filp);
 158         /* The channel created holds a reference on the session */
 159         atomic_inc(&session_filp->f_count);
 160
 161         return chan_fd;
 162
 163 chan_error:
 164         fput(chan_filp);
 165 file_error:
 166         put_unused_fd(chan_fd);
 167 fd_error:
 168         return ret;
 169 }
 170
 171 /**
 172  *      lttng_session_ioctl - lttng session fd ioctl
 173  *
 174  *      @filp: the file
 175  *      @cmd: the command
 176  *      @arg: command arg
 177  *
 178  *      This ioctl implements lttng commands:
 179  *      LTTNG_CHANNEL
 180  *              Returns a LTTng channel file descriptor
 181  *
 182  * The returned channel will be deleted when its file descriptor is closed.
 183  */
 184 static
 185 long lttng_session_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 186 {
 187         switch (cmd) {
 188         case LTTNG_CHANNEL:
 189                 return lttng_abi_create_channel(filp, (struct lttng_channel __user *)arg);
 190         default:
 191                 return -ENOIOCTLCMD;
 192         }
 193 }
 194
 195 /*
 196  * Called when the last file reference is dropped.
 197  *
 198  * Big fat note: channels and events are invariant for the whole session after
 199  * their creation. So this session destruction also destroys all channel and
 200  * event structures specific to this session (they are not destroyed when their
 201  * individual file is released).
 202  */
 203 static
 204 int lttng_session_release(struct inode *inode, struct file *file)
 205 {
 206         struct ltt_session *session = file->private_data;
 207         return ltt_session_destroy(session);
 208 }
 209
 210 static const struct file_operations lttng_session_fops = {
 211         .release = lttng_session_release,
 212         .unlocked_ioctl = lttng_session_ioctl,
 213 #ifdef CONFIG_COMPAT
 214         .compat_ioctl = lttng_session_ioctl,
 215 #endif
 216 }
 217
 218 static
 219 int lttng_abi_open_stream(struct file *channel_filp)
 220 {
 221         struct ltt_channel *channel = channel_filp->private_data;
 222         struct lib_ring_buffer *buf;
 223         int stream_fd, ret;
 224
 225         buf = ltt_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_filp = anon_inode_getfile("[lttng_stream]",
 235                                          &lib_ring_buffer_file_operations,
 236                                          buf, O_RDWR);
 237         if (IS_ERR(stream_filp)) {
 238                 ret = PTR_ERR(stream_filp);
 239                 goto file_error;
 240         }
 241         fd_install(stream_fd, stream_filp);
 242         /* The stream holds a reference on the channel */
 243         atomic_inc(&channel_filp->f_count);
 244         return stream_fd;
 245
 246 file_error:
 247         put_unused_fd(stream_fd);
 248 fd_error:
 249         ltt_buffer_read_close(buf);
 250         return ret;
 251 }
 252
 253 static
 254 int lttng_abi_create_event(struct file *channel_filp,
 255                            struct lttng_event __user *uevent_param)
 256 {
 257         struct ltt_channel *channel = channel_filp->private_data;
 258         struct ltt_event *event;
 259         char *event_name;
 260         struct lttng_event event_param;
 261         int event_fd, ret;
 262
 263         if (copy_from_user(&event_param, uevent_param, sizeof(event_param)))
 264                 return -EFAULT;
 265         event_name = kmalloc(PATH_MAX, GFP_KERNEL);
 266         if (!event_name)
 267                 return -ENOMEM;
 268         if (strncpy_from_user(event_name, &uevent_param->name, PATH_MAX)) {
 269                 ret = -EFAULT;
 270                 goto name_error;
 271         }
 272         event_name[PATH_MAX - 1] = '\0';
 273         event_fd = get_unused_fd_flags(O_RDWR);
 274         if (event_fd < 0) {
 275                 ret = event_fd;
 276                 goto fd_error;
 277         }
 278         event_filp = anon_inode_getfile("[lttng_event]",
 279                                         &lttng_event_fops, /* TODO: filter */
 280                                         NULL, O_RDWR);
 281         if (IS_ERR(event_filp)) {
 282                 ret = PTR_ERR(event_filp);
 283                 goto file_error;
 284         }
 285         /*
 286          * We tolerate no failure path after event creation. It will stay
 287          * invariant for the rest of the session.
 288          */
 289         event = ltt_event_create(channel, event_param->itype, event_name, NULL);
 290         if (!event) {
 291                 goto event_error;
 292                 ret = -EEXIST;
 293         }
 294         event_filp->private_data = event;
 295         fd_install(event_fd, event_filp);
 296         /* The event holds a reference on the channel */
 297         atomic_inc(&channel_filp->f_count);
 298         kfree(event_name);
 299         return event_fd;
 300
 301 event_error:
 302         fput(event_filp);
 303 file_error:
 304         put_unused_fd(event_fd);
 305 fd_error:
 306 name_error:
 307         kfree(event_name);
 308         return ret;
 309 }
 310
 311 /**
 312  *      lttng_channel_ioctl - lttng syscall through ioctl
 313  *
 314  *      @filp: the file
 315  *      @cmd: the command
 316  *      @arg: command arg
 317  *
 318  *      This ioctl implements lttng commands:
 319  *      LTTNG_STREAM
 320  *              Returns an event stream file descriptor or failure.
 321  *              (typically, one event stream records events from one CPU)
 322  *      LTTNG_EVENT
 323  *              Returns an event file descriptor or failure.
 324  *
 325  * The returned session will be deleted when its file descriptor is closed.
 326  * Channel and event file descriptors also hold a reference on the session.
 327  */
 328 static
 329 long lttng_channel_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 330 {
 331         switch (cmd) {
 332         case LTTNG_STREAM:
 333                 return lttng_abi_open_stream(filp);
 334         case LTTNG_EVENT:
 335                 return lttng_abi_create_event(filp, (struct lttng_event __user *)arg);
 336         default:
 337                 return -ENOIOCTLCMD;
 338         }
 339 }
 340
 341 /**
 342  *      lttng_channel_poll - lttng stream addition/removal monitoring
 343  *
 344  *      @filp: the file
 345  *      @wait: poll table
 346  */
 347 unsigned int lttng_channel_poll(struct file *filp, poll_table *wait)
 348 {
 349         struct ltt_channel *channel = filp->private_data;
 350         unsigned int mask = 0;
 351
 352         if (filp->f_mode & FMODE_READ) {
 353                 poll_wait_set_exclusive(wait);
 354                 poll_wait(filp, &channel->notify_wait, wait);
 355
 356                 /* TODO: identify when the channel is being finalized. */
 357                 if (finalized)
 358                         return POLLHUP;
 359                 else
 360                         return POLLIN | POLLRDNORM;
 361         }
 362         return mask;
 363
 364 }
 365
 366 static const struct file_operations lttng_channel_fops = {
 367         .release = lttng_channel_release,
 368         .poll = lttng_channel_poll,
 369         .unlocked_ioctl = lttng_channel_ioctl,
 370 #ifdef CONFIG_COMPAT
 371         .compat_ioctl = lttng_channel_ioctl,
 372 #endif
 373 }
 374
 375 static int __init ltt_debugfs_abi_init(void)
 376 {
 377         int ret = 0;
 378
 379         lttng_dentry = debugfs_create_file("lttng", NULL);
 380         if (IS_ERR(lttng_dentry) || !lttng_dentry)
 381                 printk(KERN_ERR "Error creating LTTng control file\n");
 382                 ret = -ENOMEM;
 383                 goto error;
 384         }
 385 error:
 386         return ret;
 387 }
 388
 389 static void __exit ltt_debugfs_abi_exit(void)
 390 {
 391         debugfs_remote(lttng_dentry);
 392 }