src/inotify.c

   1 /* Inotify support for Emacs
   2
   3 Copyright (C) 2012-2018 Free Software Foundation, Inc.
   4
   5 This file is part of GNU Emacs.
   6
   7 GNU Emacs is free software: you can redistribute it and/or modify
   8 it under the terms of the GNU General Public License as published by
   9 the Free Software Foundation, either version 3 of the License, or (at
  10 your option) any later version.
  11
  12 GNU Emacs is distributed in the hope that it will be useful,
  13 but WITHOUT ANY WARRANTY; without even the implied warranty of
  14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15 GNU General Public License for more details.
  16
  17 You should have received a copy of the GNU General Public License
  18 along with GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.  */
  19
  20 #include <config.h>
  21
  22 #ifdef HAVE_INOTIFY
  23
  24 #include "lisp.h"
  25 #include "coding.h"
  26 #include "process.h"
  27 #include "keyboard.h"
  28 #include "termhooks.h"
  29
  30 #include <errno.h>
  31 #include <sys/inotify.h>
  32 #include <sys/ioctl.h>
  33
  34 /* Ignore bits that might be undefined on old GNU/Linux systems.  */
  35 #ifndef IN_EXCL_UNLINK
  36 # define IN_EXCL_UNLINK 0
  37 #endif
  38 #ifndef IN_DONT_FOLLOW
  39 # define IN_DONT_FOLLOW 0
  40 #endif
  41 #ifndef IN_ONLYDIR
  42 # define IN_ONLYDIR 0
  43 #endif
  44
  45 /* File handle for inotify.  */
  46 static int inotifyfd = -1;
  47
  48 /* Alist of files being watched.  We want the returned descriptor to
  49    be unique for every watch, but inotify returns the same descriptor
  50    WD for multiple calls to inotify_add_watch with the same file.
  51    Supply a nonnegative integer ID, so that WD and ID together
  52    uniquely identify a watch/file combination.
  53
  54    For the same reason, we also need to store the watch's mask and we
  55    can't allow the following flags to be used.
  56
  57    IN_EXCL_UNLINK
  58    IN_MASK_ADD
  59    IN_ONESHOT
  60
  61    Each element of this list is of the form (DESCRIPTOR . WATCHES)
  62    where no two DESCRIPTOR values are the same.  DESCRIPTOR represents
  63    the inotify watch descriptor and WATCHES is a list with elements of
  64    the form (ID FILENAME CALLBACK MASK), where ID is the integer
  65    described above, FILENAME names the file being watched, CALLBACK is
  66    invoked when the event occurs, and MASK represents the aspects
  67    being watched.  The WATCHES list is sorted by ID.  Although
  68    DESCRIPTOR and MASK are ordinarily integers, they are conses when
  69    representing integers outside of fixnum range.  */
  70
  71 static Lisp_Object watch_list;
  72
  73 static Lisp_Object
  74 mask_to_aspects (uint32_t mask)
  75 {
  76   Lisp_Object aspects = Qnil;
  77   if (mask & IN_ACCESS)
  78     aspects = Fcons (Qaccess, aspects);
  79   if (mask & IN_ATTRIB)
  80     aspects = Fcons (Qattrib, aspects);
  81   if (mask & IN_CLOSE_WRITE)
  82     aspects = Fcons (Qclose_write, aspects);
  83   if (mask & IN_CLOSE_NOWRITE)
  84     aspects = Fcons (Qclose_nowrite, aspects);
  85   if (mask & IN_CREATE)
  86     aspects = Fcons (Qcreate, aspects);
  87   if (mask & IN_DELETE)
  88     aspects = Fcons (Qdelete, aspects);
  89   if (mask & IN_DELETE_SELF)
  90     aspects = Fcons (Qdelete_self, aspects);
  91   if (mask & IN_MODIFY)
  92     aspects = Fcons (Qmodify, aspects);
  93   if (mask & IN_MOVE_SELF)
  94     aspects = Fcons (Qmove_self, aspects);
  95   if (mask & IN_MOVED_FROM)
  96     aspects = Fcons (Qmoved_from, aspects);
  97   if (mask & IN_MOVED_TO)
  98     aspects = Fcons (Qmoved_to, aspects);
  99   if (mask & IN_OPEN)
 100     aspects = Fcons (Qopen,  aspects);
 101   if (mask & IN_IGNORED)
 102     aspects = Fcons (Qignored, aspects);
 103   if (mask & IN_ISDIR)
 104     aspects = Fcons (Qisdir, aspects);
 105   if (mask & IN_Q_OVERFLOW)
 106     aspects = Fcons (Qq_overflow, aspects);
 107   if (mask & IN_UNMOUNT)
 108     aspects = Fcons (Qunmount, aspects);
 109   return aspects;
 110 }
 111
 112 static uint32_t
 113 symbol_to_inotifymask (Lisp_Object symb)
 114 {
 115   if (EQ (symb, Qaccess))
 116     return IN_ACCESS;
 117   else if (EQ (symb, Qattrib))
 118     return IN_ATTRIB;
 119   else if (EQ (symb, Qclose_write))
 120     return IN_CLOSE_WRITE;
 121   else if (EQ (symb, Qclose_nowrite))
 122     return IN_CLOSE_NOWRITE;
 123   else if (EQ (symb, Qcreate))
 124     return IN_CREATE;
 125   else if (EQ (symb, Qdelete))
 126     return IN_DELETE;
 127   else if (EQ (symb, Qdelete_self))
 128     return IN_DELETE_SELF;
 129   else if (EQ (symb, Qmodify))
 130     return IN_MODIFY;
 131   else if (EQ (symb, Qmove_self))
 132     return IN_MOVE_SELF;
 133   else if (EQ (symb, Qmoved_from))
 134     return IN_MOVED_FROM;
 135   else if (EQ (symb, Qmoved_to))
 136     return IN_MOVED_TO;
 137   else if (EQ (symb, Qopen))
 138     return IN_OPEN;
 139   else if (EQ (symb, Qmove))
 140     return IN_MOVE;
 141   else if (EQ (symb, Qclose))
 142     return IN_CLOSE;
 143
 144   else if (EQ (symb, Qdont_follow))
 145     return IN_DONT_FOLLOW;
 146   else if (EQ (symb, Qonlydir))
 147     return IN_ONLYDIR;
 148
 149   else if (EQ (symb, Qt) || EQ (symb, Qall_events))
 150     return IN_ALL_EVENTS;
 151   else
 152     {
 153       errno = EINVAL;
 154       report_file_notify_error ("Unknown aspect", symb);
 155     }
 156 }
 157
 158 static uint32_t
 159 aspect_to_inotifymask (Lisp_Object aspect)
 160 {
 161   if (CONSP (aspect) || NILP (aspect))
 162     {
 163       Lisp_Object x = aspect;
 164       uint32_t mask = 0;
 165       FOR_EACH_TAIL (x)
 166         mask |= symbol_to_inotifymask (XCAR (x));
 167       CHECK_LIST_END (x, aspect);
 168       return mask;
 169     }
 170   else
 171     return symbol_to_inotifymask (aspect);
 172 }
 173
 174 static Lisp_Object
 175 inotifyevent_to_event (Lisp_Object watch, struct inotify_event const *ev)
 176 {
 177   Lisp_Object name;
 178   uint32_t mask;
 179   CONS_TO_INTEGER (Fnth (make_number (3), watch), uint32_t, mask);
 180
 181   if (! (mask & ev->mask))
 182     return Qnil;
 183
 184   if (ev->len > 0)
 185     {
 186       size_t const len = strlen (ev->name);
 187       name = make_unibyte_string (ev->name, min (len, ev->len));
 188       name = DECODE_FILE (name);
 189     }
 190   else
 191     name = XCAR (XCDR (watch));
 192
 193   return list2 (list4 (Fcons (INTEGER_TO_CONS (ev->wd), XCAR (watch)),
 194                        mask_to_aspects (ev->mask),
 195                        name,
 196                        INTEGER_TO_CONS (ev->cookie)),
 197                 Fnth (make_number (2), watch));
 198 }
 199
 200 /* Add a new watch to watch-descriptor WD watching FILENAME and using
 201    IMASK and CALLBACK.  Return a cons (DESCRIPTOR . ID) uniquely
 202    identifying the new watch.  */
 203 static Lisp_Object
 204 add_watch (int wd, Lisp_Object filename,
 205            uint32_t imask, Lisp_Object callback)
 206 {
 207   Lisp_Object descriptor = INTEGER_TO_CONS (wd);
 208   Lisp_Object tail = assoc_no_quit (descriptor, watch_list);
 209   Lisp_Object watch, watch_id;
 210   Lisp_Object mask = INTEGER_TO_CONS (imask);
 211
 212   EMACS_INT id = 0;
 213   if (NILP (tail))
 214     {
 215       tail = list1 (descriptor);
 216       watch_list = Fcons (tail, watch_list);
 217     }
 218   else
 219     {
 220       /* Assign a watch ID that is not already in use, by looking
 221          for a gap in the existing sorted list.  */
 222       for (; ! NILP (XCDR (tail)); tail = XCDR (tail), id++)
 223         if (!EQ (XCAR (XCAR (XCDR (tail))), make_number (id)))
 224           break;
 225       if (MOST_POSITIVE_FIXNUM < id)
 226         emacs_abort ();
 227     }
 228
 229   /* Insert the newly-assigned ID into the previously-discovered gap,
 230      which is possibly at the end of the list.  Inserting it there
 231      keeps the list sorted.  */
 232   watch_id = make_number (id);
 233   watch = list4 (watch_id, filename, callback, mask);
 234   XSETCDR (tail, Fcons (watch, XCDR (tail)));
 235
 236   return Fcons (descriptor, watch_id);
 237 }
 238
 239 /* Find the watch list element (if any) matching DESCRIPTOR.  Return
 240    nil if not found.  If found, return t if the first element matches
 241    DESCRIPTOR; otherwise, return the cons whose cdr matches
 242    DESCRIPTOR.  This lets the caller easily remove the element
 243    matching DESCRIPTOR without having to search for it again, and
 244    without calling Fdelete (which might quit).  */
 245
 246 static Lisp_Object
 247 find_descriptor (Lisp_Object descriptor)
 248 {
 249   Lisp_Object tail, prevtail = Qt;
 250   for (tail = watch_list; !NILP (tail); prevtail = tail, tail = XCDR (tail))
 251     if (equal_no_quit (XCAR (XCAR (tail)), descriptor))
 252       return prevtail;
 253   return Qnil;
 254 }
 255
 256 /*  Remove all watches associated with the watch list element after
 257     PREVTAIL, or after the first element if PREVTAIL is t.  If INVALID_P
 258     is true, the descriptor is already invalid, i.e., it received a
 259     IN_IGNORED event.  In this case skip calling inotify_rm_watch.  */
 260 static void
 261 remove_descriptor (Lisp_Object prevtail, bool invalid_p)
 262 {
 263   Lisp_Object tail = CONSP (prevtail) ? XCDR (prevtail) : watch_list;
 264
 265   int inotify_errno = 0;
 266   if (! invalid_p)
 267     {
 268       int wd;
 269       CONS_TO_INTEGER (XCAR (XCAR (tail)), int, wd);
 270       if (inotify_rm_watch (inotifyfd, wd) != 0)
 271         inotify_errno = errno;
 272     }
 273
 274   if (CONSP (prevtail))
 275     XSETCDR (prevtail, XCDR (tail));
 276   else
 277     {
 278       watch_list = XCDR (tail);
 279       if (NILP (watch_list))
 280         {
 281           delete_read_fd (inotifyfd);
 282           emacs_close (inotifyfd);
 283           inotifyfd = -1;
 284         }
 285     }
 286
 287   if (inotify_errno != 0)
 288     {
 289       errno = inotify_errno;
 290       report_file_notify_error ("Could not rm watch", XCAR (tail));
 291     }
 292 }
 293
 294 /*  Remove watch associated with (descriptor, id).  */
 295 static void
 296 remove_watch (Lisp_Object descriptor, Lisp_Object id)
 297 {
 298   Lisp_Object prevtail = find_descriptor (descriptor);
 299   if (NILP (prevtail))
 300     return;
 301
 302   Lisp_Object elt = XCAR (CONSP (prevtail) ? XCDR (prevtail) : watch_list);
 303   for (Lisp_Object prev = elt; !NILP (XCDR (prev)); prev = XCDR (prev))
 304     if (EQ (id, XCAR (XCAR (XCDR (prev)))))
 305       {
 306         XSETCDR (prev, XCDR (XCDR (prev)));
 307         if (NILP (XCDR (elt)))
 308           remove_descriptor (prevtail, false);
 309         break;
 310       }
 311 }
 312
 313 /* This callback is called when the FD is available for read.  The inotify
 314    events are read from FD and converted into input_events.  */
 315 static void
 316 inotify_callback (int fd, void *_)
 317 {
 318   int to_read;
 319   if (ioctl (fd, FIONREAD, &to_read) < 0)
 320     report_file_notify_error ("Error while retrieving file system events",
 321                               Qnil);
 322   USE_SAFE_ALLOCA;
 323   char *buffer = SAFE_ALLOCA (to_read);
 324   ssize_t n = read (fd, buffer, to_read);
 325   if (n < 0)
 326     report_file_notify_error ("Error while reading file system events", Qnil);
 327
 328   struct input_event event;
 329   EVENT_INIT (event);
 330   event.kind = FILE_NOTIFY_EVENT;
 331
 332   for (ssize_t i = 0; i < n; )
 333     {
 334       struct inotify_event *ev = (struct inotify_event *) &buffer[i];
 335       Lisp_Object descriptor = INTEGER_TO_CONS (ev->wd);
 336       Lisp_Object prevtail = find_descriptor (descriptor);
 337
 338       if (! NILP (prevtail))
 339         {
 340           Lisp_Object tail = CONSP (prevtail) ? XCDR (prevtail) : watch_list;
 341           for (Lisp_Object watches = XCDR (XCAR (tail)); ! NILP (watches);
 342                watches = XCDR (watches))
 343             {
 344               event.arg = inotifyevent_to_event (XCAR (watches), ev);
 345               if (!NILP (event.arg))
 346                 kbd_buffer_store_event (&event);
 347             }
 348           /* If event was removed automatically: Drop it from watch list.  */
 349           if (ev->mask & IN_IGNORED)
 350             remove_descriptor (prevtail, true);
 351         }
 352       i += sizeof (*ev) + ev->len;
 353     }
 354
 355   SAFE_FREE ();
 356 }
 357
 358 DEFUN ("inotify-add-watch", Finotify_add_watch, Sinotify_add_watch, 3, 3, 0,
 359        doc: /* Add a watch for FILE-NAME to inotify.
 360
 361 Return a watch descriptor.  The watch will look for ASPECT events and
 362 invoke CALLBACK when an event occurs.
 363
 364 ASPECT might be one of the following symbols or a list of those symbols:
 365
 366 access
 367 attrib
 368 close-write
 369 close-nowrite
 370 create
 371 delete
 372 delete-self
 373 modify
 374 move-self
 375 moved-from
 376 moved-to
 377 open
 378
 379 all-events or t
 380 move
 381 close
 382
 383 ASPECT can also contain the following symbols, which control whether
 384 the watch descriptor will be created:
 385
 386 dont-follow
 387 onlydir
 388
 389 Watching a directory is not recursive.  CALLBACK is passed a single argument
 390 EVENT which contains an event structure of the format
 391
 392 \(WATCH-DESCRIPTOR ASPECTS NAME COOKIE)
 393
 394 WATCH-DESCRIPTOR is the same object that was returned by this function.  It can
 395 be tested for equality using `equal'.  ASPECTS describes the event.  It is a
 396 list of ASPECT symbols described above and can also contain one of the following
 397 symbols
 398
 399 ignored
 400 isdir
 401 q-overflow
 402 unmount
 403
 404 If a directory is watched then NAME is the name of file that caused the event.
 405
 406 COOKIE is an object that can be compared using `equal' to identify two matching
 407 renames (moved-from and moved-to).
 408
 409 See inotify(7) and inotify_add_watch(2) for further information.  The
 410 inotify fd is managed internally and there is no corresponding
 411 inotify_init.  Use `inotify-rm-watch' to remove a watch.
 412
 413 The following inotify bit-masks cannot be used because descriptors are
 414 shared across different callers.
 415
 416 IN_EXCL_UNLINK
 417 IN_MASK_ADD
 418 IN_ONESHOT  */)
 419      (Lisp_Object filename, Lisp_Object aspect, Lisp_Object callback)
 420 {
 421   Lisp_Object encoded_file_name;
 422   int wd = -1;
 423   uint32_t imask = aspect_to_inotifymask (aspect);
 424   uint32_t mask = imask | IN_MASK_ADD | IN_EXCL_UNLINK;
 425
 426   CHECK_STRING (filename);
 427
 428   if (inotifyfd < 0)
 429     {
 430       inotifyfd = inotify_init1 (IN_NONBLOCK | IN_CLOEXEC);
 431       if (inotifyfd < 0)
 432         report_file_notify_error ("File watching is not available", Qnil);
 433       watch_list = Qnil;
 434       add_read_fd (inotifyfd, &inotify_callback, NULL);
 435     }
 436
 437   encoded_file_name = ENCODE_FILE (filename);
 438   wd = inotify_add_watch (inotifyfd, SSDATA (encoded_file_name), mask);
 439   if (wd < 0)
 440     report_file_notify_error ("Could not add watch for file", filename);
 441
 442   return add_watch (wd, filename, imask, callback);
 443 }
 444
 445 static bool
 446 valid_watch_descriptor (Lisp_Object wd)
 447 {
 448   return (CONSP (wd)
 449           && (RANGED_INTEGERP (0, XCAR (wd), INT_MAX)
 450               || (CONSP (XCAR (wd))
 451                   && RANGED_INTEGERP ((MOST_POSITIVE_FIXNUM >> 16) + 1,
 452                                       XCAR (XCAR (wd)), INT_MAX >> 16)
 453                   && RANGED_INTEGERP (0, XCDR (XCAR (wd)), (1 << 16) - 1)))
 454           && NATNUMP (XCDR (wd)));
 455 }
 456
 457 DEFUN ("inotify-rm-watch", Finotify_rm_watch, Sinotify_rm_watch, 1, 1, 0,
 458        doc: /* Remove an existing WATCH-DESCRIPTOR.
 459
 460 WATCH-DESCRIPTOR should be an object returned by `inotify-add-watch'.
 461
 462 See inotify_rm_watch(2) for more information.  */)
 463      (Lisp_Object watch_descriptor)
 464 {
 465
 466   Lisp_Object descriptor, id;
 467
 468   if (! valid_watch_descriptor (watch_descriptor))
 469     report_file_notify_error ("Invalid descriptor ", watch_descriptor);
 470
 471   descriptor = XCAR (watch_descriptor);
 472   id = XCDR (watch_descriptor);
 473   remove_watch (descriptor, id);
 474
 475   return Qt;
 476 }
 477
 478 DEFUN ("inotify-valid-p", Finotify_valid_p, Sinotify_valid_p, 1, 1, 0,
 479        doc: /* Check a watch specified by its WATCH-DESCRIPTOR.
 480
 481 WATCH-DESCRIPTOR should be an object returned by `inotify-add-watch'.
 482
 483 A watch can become invalid if the file or directory it watches is
 484 deleted, or if the watcher thread exits abnormally for any other
 485 reason.  Removing the watch by calling `inotify-rm-watch' also makes
 486 it invalid.  */)
 487      (Lisp_Object watch_descriptor)
 488 {
 489   if (! valid_watch_descriptor (watch_descriptor))
 490     return Qnil;
 491   Lisp_Object tail = assoc_no_quit (XCAR (watch_descriptor), watch_list);
 492   if (NILP (tail))
 493     return Qnil;
 494   Lisp_Object watch = assq_no_quit (XCDR (watch_descriptor), XCDR (tail));
 495   return ! NILP (watch) ? Qt : Qnil;
 496 }
 497
 498 #ifdef INOTIFY_DEBUG
 499 DEFUN ("inotify-watch-list", Finotify_watch_list, Sinotify_watch_list, 0, 0, 0,
 500        doc: /* Return a copy of the internal watch_list.  */)
 501 {
 502   return Fcopy_sequence (watch_list);
 503 }
 504
 505 DEFUN ("inotify-allocated-p", Finotify_allocated_p, Sinotify_allocated_p, 0, 0, 0,
 506        doc: /* Return non-nil, if an inotify instance is allocated.  */)
 507 {
 508   return inotifyfd < 0 ? Qnil : Qt;
 509 }
 510 #endif
 511
 512 void
 513 syms_of_inotify (void)
 514 {
 515   DEFSYM (Qaccess, "access");           /* IN_ACCESS */
 516   DEFSYM (Qattrib, "attrib");           /* IN_ATTRIB */
 517   DEFSYM (Qclose_write, "close-write"); /* IN_CLOSE_WRITE */
 518   DEFSYM (Qclose_nowrite, "close-nowrite");
 519                                         /* IN_CLOSE_NOWRITE */
 520   DEFSYM (Qcreate, "create");           /* IN_CREATE */
 521   DEFSYM (Qdelete, "delete");           /* IN_DELETE */
 522   DEFSYM (Qdelete_self, "delete-self"); /* IN_DELETE_SELF */
 523   DEFSYM (Qmodify, "modify");           /* IN_MODIFY */
 524   DEFSYM (Qmove_self, "move-self");     /* IN_MOVE_SELF */
 525   DEFSYM (Qmoved_from, "moved-from");   /* IN_MOVED_FROM */
 526   DEFSYM (Qmoved_to, "moved-to");       /* IN_MOVED_TO */
 527   DEFSYM (Qopen, "open");               /* IN_OPEN */
 528
 529   DEFSYM (Qall_events, "all-events");   /* IN_ALL_EVENTS */
 530   DEFSYM (Qmove, "move");               /* IN_MOVE */
 531   DEFSYM (Qclose, "close");             /* IN_CLOSE */
 532
 533   DEFSYM (Qdont_follow, "dont-follow"); /* IN_DONT_FOLLOW */
 534   DEFSYM (Qonlydir, "onlydir");         /* IN_ONLYDIR */
 535
 536   DEFSYM (Qignored, "ignored");         /* IN_IGNORED */
 537   DEFSYM (Qisdir, "isdir");             /* IN_ISDIR */
 538   DEFSYM (Qq_overflow, "q-overflow");   /* IN_Q_OVERFLOW */
 539   DEFSYM (Qunmount, "unmount");         /* IN_UNMOUNT */
 540
 541   defsubr (&Sinotify_add_watch);
 542   defsubr (&Sinotify_rm_watch);
 543   defsubr (&Sinotify_valid_p);
 544
 545 #ifdef INOTIFY_DEBUG
 546   defsubr (&Sinotify_watch_list);
 547   defsubr (&Sinotify_allocated_p);
 548 #endif
 549   staticpro (&watch_list);
 550
 551   Fprovide (intern_c_string ("inotify"), Qnil);
 552 }
 553
 554 #endif /* HAVE_INOTIFY */