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
  38 /*
  39  * LTTng DebugFS ABI structures.
  40  */
  41
  42 struct lttng_channel {
  43         int overwrite;                  /* 1: overwrite, 0: discard */
  44         u64 subbuf_size;
  45         u64 num_subbuf;
  46         unsigned int switch_timer_interval;
  47         unsigned int read_timer_interval;
  48 };
  49
  50 struct lttng_event {
  51         enum instrum_type itype;
  52         char name[];
  53 };
  54
  55 static
  56 int lttng_abi_create_session(void)
  57 {
  58         struct ltt_session *session;
  59         struct file *session_file;
  60         int session_fd;
  61
  62         session = ltt_session_create();
  63         if (!session)
  64                 return -ENOMEM;
  65         session_fd = get_unused_fd_flags(O_RDWR);
  66         if (session_fd < 0) {
  67                 ret = session_fd;
  68                 goto fd_error;
  69         }
  70         session_file = anon_inode_getfile("[lttng_session]",
  71                                           &lttng_session_fops,
  72                                           session, O_RDWR);
  73         if (IS_ERR(session_file)) {
  74                 ret = PTR_ERR(session_file);
  75                 goto file_error;
  76         }
  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 /**
  88  *      lttng_ioctl - lttng syscall through ioctl
  89  *
  90  *      @filp: the file
  91  *      @cmd: the command
  92  *      @arg: command arg
  93  *
  94  *      This ioctl implements lttng commands:
  95  *      LTTNG_SESSION
  96  *              Returns a LTTng trace session file descriptor
  97  *
  98  * The returned session will be deleted when its file descriptor is closed.
  99  */
 100 static
 101 long lttng_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 102 {
 103         switch (cmd) {
 104         case LTTNG_SESSION:
 105                 return lttng_abi_create_session();
 106         default:
 107                 return -ENOIOCTLCMD;
 108         }
 109 }
 110
 111 #ifdef CONFIG_COMPAT
 112 static
 113 long lttng_compat_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 114 {
 115         switch (cmd) {
 116         case LTTNG_SESSION:
 117                 return lttng_abi_create_session();
 118         default:
 119                 return -ENOIOCTLCMD;
 120         }
 121 }
 122 #endif
 123
 124 static const struct file_operations lttng_fops = {
 125         .unlocked_ioctl = lttng_ioctl,
 126 #ifdef CONFIG_COMPAT
 127         .compat_ioctl = lttng_compat_ioctl,
 128 #endif
 129 }
 130
 131 int lttng_abi_create_channel(struct file *session_filp,
 132                              struct lttng_channel __user *uchan_param)
 133 {
 134         struct ltt_session *session = session_filp->private_data;
 135         struct ltt_channel *chan;
 136         struct file *chan_filp;
 137         struct lttng_channel chan_param;
 138         int chan_fd;
 139         int ret = 0;
 140
 141         if (copy_from_user(&chan_param, uchan_param, sizeof(chan_param)))
 142                 return -EFAULT;
 143         chan = ltt_channel_create(session, chan_param->overwrite, NULL,
 144                                   chan_param->subbuf_size,
 145                                   chan_param->num_subbuf,
 146                                   chan_param->switch_timer_interval,
 147                                   chan_param->read_timer_interval);
 148         if (!chan) {
 149                 ret = -ENOMEM;
 150                 goto chan_error;
 151         }
 152         chan_fd = get_unused_fd_flags(O_RDWR);
 153         if (chan_fd < 0) {
 154                 ret = chan_fd;
 155                 goto fd_error;
 156         }
 157         chan_filp = anon_inode_getfile("[lttng_channel]",
 158                                        &lttng_channel_fops,
 159                                        chan, O_RDWR);
 160         if (IS_ERR(chan_filp)) {
 161                 ret = PTR_ERR(chan_filp);
 162                 goto file_error;
 163         }
 164
 165         /* The channel created holds a reference on the session */
 166         atomic_inc(&session_filp->f_count);
 167
 168         return chan_fd;
 169
 170 file_error:
 171         put_unused_fd(chan_fd);
 172 fd_error:
 173         ltt_channel_destroy(chan);
 174 chan_error:
 175         return ret;
 176 }
 177
 178 /**
 179  *      lttng_session_ioctl - lttng session fd ioctl
 180  *
 181  *      @filp: the file
 182  *      @cmd: the command
 183  *      @arg: command arg
 184  *
 185  *      This ioctl implements lttng commands:
 186  *      LTTNG_CHANNEL
 187  *              Returns a LTTng channel file descriptor
 188  *
 189  * The returned channel will be deleted when its file descriptor is closed.
 190  */
 191 static
 192 long lttng_session_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 193 {
 194         switch (cmd) {
 195         case LTTNG_CHANNEL:
 196                 return lttng_abi_create_channel(filp, (struct lttng_channel __user *)arg);
 197         default:
 198                 return -ENOIOCTLCMD;
 199         }
 200 }
 201
 202 #ifdef CONFIG_COMPAT
 203 static
 204 long lttng_session_compat_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 205 {
 206         switch (cmd) {
 207         case LTTNG_CHANNEL:
 208                 return lttng_abi_create_channel(filp, (struct lttng_channel __user *)arg);
 209         default:
 210                 return -ENOIOCTLCMD;
 211         }
 212 }
 213 #endif
 214
 215 static const struct file_operations lttng_session_fops = {
 216         .unlocked_ioctl = lttng_session_ioctl,
 217 #ifdef CONFIG_COMPAT
 218         .compat_ioctl = lttng_session_compat_ioctl,
 219 #endif
 220 }
 221
 222 static
 223 int lttng_abi_open_stream(struct file *channel_filp)
 224 {
 225         struct ltt_channel *channel = channel_filp->private_data;
 226         struct lib_ring_buffer *buf;
 227         int stream_fd, ret;
 228
 229         buf = ltt_buffer_read_open(channel->chan);
 230         if (!buf)
 231                 return -ENOENT;
 232
 233         stream_fd = get_unused_fd_flags(O_RDWR);
 234         if (stream_fd < 0) {
 235                 ret = stream_fd;
 236                 goto fd_error;
 237         }
 238         stream_filp = anon_inode_getfile("[lttng_stream]",
 239                                          &lttng_stream_fops,
 240                                          buf, O_RDWR);
 241         if (IS_ERR(stream_filp)) {
 242                 ret = PTR_ERR(stream_filp);
 243                 goto file_error;
 244         }
 245
 246         /* The stream holds a reference on the channel */
 247         atomic_inc(&channel_filp->f_count);
 248         return stream_fd;
 249
 250 file_error:
 251         put_unused_fd(stream_fd);
 252 fd_error:
 253         ltt_buffer_read_close(buf);
 254         return ret;
 255 }
 256
 257 static
 258 int lttng_abi_create_event(struct file *channel_filp,
 259                            struct lttng_event __user *uevent_param)
 260 {
 261         struct ltt_channel *channel = channel_filp->private_data;
 262         struct ltt_event *event;
 263         char *event_name;
 264         struct lttng_event event_param;
 265         int event_fd, ret;
 266
 267         if (copy_from_user(&event_param, uevent_param, sizeof(event_param)))
 268                 return -EFAULT;
 269         event_name = kmalloc(PATH_MAX, GFP_KERNEL);
 270         if (!event_name)
 271                 return -ENOMEM;
 272         if (strncpy_from_user(event_name, &uevent_param->name, PATH_MAX)) {
 273                 ret = -EFAULT;
 274                 goto name_error;
 275         }
 276         event_name[PATH_MAX - 1] = '\0';
 277         event = ltt_event_create(channel, event_param->itype, event_name, NULL);
 278         if (!event)
 279                 return -EEXIST;
 280
 281         event_fd = get_unused_fd_flags(O_RDWR);
 282         if (event_fd < 0) {
 283                 ret = event_fd;
 284                 goto fd_error;
 285         }
 286         event_filp = anon_inode_getfile("[lttng_event]",
 287                                          &lttng_event_fops,
 288                                          event, O_RDWR);
 289         if (IS_ERR(event_filp)) {
 290                 ret = PTR_ERR(event_filp);
 291                 goto file_error;
 292         }
 293
 294         /* The event holds a reference on the channel */
 295         atomic_inc(&channel_filp->f_count);
 296         return event_fd;
 297
 298 file_error:
 299         put_unused_fd(event_fd);
 300 fd_error:
 301         ltt_event_destroy(event);
 302 name_error:
 303         kfree(event_name);
 304         return ret;
 305 }
 306
 307 /**
 308  *      lttng_channel_ioctl - lttng syscall through ioctl
 309  *
 310  *      @filp: the file
 311  *      @cmd: the command
 312  *      @arg: command arg
 313  *
 314  *      This ioctl implements lttng commands:
 315  *      LTTNG_STREAM
 316  *              Returns an event stream file descriptor or failure.
 317  *              (typically, one event stream records events from one CPU)
 318  *      LTTNG_EVENT
 319  *              Returns an event file descriptor or failure.
 320  *
 321  * The returned session will be deleted when its file descriptor is closed.
 322  * Channel and event file descriptors also hold a reference on the session.
 323  */
 324 static
 325 long lttng_channel_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 326 {
 327         switch (cmd) {
 328         case LTTNG_STREAM:
 329                 return lttng_abi_open_stream(filp);
 330         case LTTNG_EVENT:
 331                 return lttng_abi_create_event(filp, (struct lttng_event __user *)arg);
 332         default:
 333                 return -ENOIOCTLCMD;
 334         }
 335 }
 336
 337 #ifdef CONFIG_COMPAT
 338 static
 339 long lttng_channel_compat_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 340 {
 341         switch (cmd) {
 342         case LTTNG_STREAM:
 343                 return lttng_abi_open_stream(filp);
 344         case LTTNG_EVENT:
 345                 return lttng_abi_create_event(filp, (struct lttng_event __user *)arg);
 346         default:
 347                 return -ENOIOCTLCMD;
 348         }
 349 }
 350 #endif
 351
 352 /**
 353  *      lttng_channel_poll - lttng stream addition/removal monitoring
 354  *
 355  *      @filp: the file
 356  *      @wait: poll table
 357  */
 358 unsigned int lttng_channel_poll(struct file *filp, poll_table *wait)
 359 {
 360         struct ltt_channel *channel = filp->private_data;
 361         unsigned int mask = 0;
 362
 363         if (filp->f_mode & FMODE_READ) {
 364                 poll_wait_set_exclusive(wait);
 365                 poll_wait(filp, &channel->notify_wait, wait);
 366
 367                 /* TODO: identify when the channel is being finalized. */
 368                 if (finalized)
 369                         return POLLHUP;
 370                 else
 371                         return POLLIN | POLLRDNORM;
 372         }
 373         return mask;
 374
 375 }
 376
 377 static const struct file_operations lttng_channel_fops = {
 378         .poll = lttng_channel_poll,
 379         .unlocked_ioctl = lttng_channel_ioctl,
 380 #ifdef CONFIG_COMPAT
 381         .compat_ioctl = lttng_channel_compat_ioctl,
 382 #endif
 383 }
 384
 385 static int __init ltt_debugfs_abi_init(void)
 386 {
 387         int ret = 0;
 388
 389         lttng_dentry = debugfs_create_file("lttng", NULL);
 390         if (IS_ERR(lttng_dentry) || !lttng_dentry)
 391                 printk(KERN_ERR "Error creating LTTng control file\n");
 392                 ret = -ENOMEM;
 393                 goto error;
 394         }
 395 error:
 396         return ret;
 397 }
 398
 399 static void __exit ltt_debugfs_abi_exit(void)
 400 {
 401         debugfs_remote(lttng_dentry);
 402 }