lib/fcntl.c

   1 /* Provide file descriptor control.
   2
   3    Copyright (C) 2009-2017 Free Software Foundation, Inc.
   4
   5    This program is free software: you can redistribute it and/or modify
   6    it under the terms of the GNU General Public License as published by
   7    the Free Software Foundation; either version 3 of the License, or
   8    (at your option) any later version.
   9
  10    This program is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13    GNU General Public License for more details.
  14
  15    You should have received a copy of the GNU General Public License
  16    along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
  17
  18 /* Written by Eric Blake <ebb9@byu.net>.  */
  19
  20 #include <config.h>
  21
  22 /* Specification.  */
  23 #include <fcntl.h>
  24
  25 #include <errno.h>
  26 #include <limits.h>
  27 #include <stdarg.h>
  28 #include <unistd.h>
  29
  30 #if !HAVE_FCNTL
  31 # define rpl_fcntl fcntl
  32 #endif
  33 #undef fcntl
  34
  35 #if (defined _WIN32 || defined __WIN32__) && ! defined __CYGWIN__
  36 /* Get declarations of the native Windows API functions.  */
  37 # define WIN32_LEAN_AND_MEAN
  38 # include <windows.h>
  39
  40 /* Get _get_osfhandle.  */
  41 # if GNULIB_MSVC_NOTHROW
  42 #  include "msvc-nothrow.h"
  43 # else
  44 #  include <io.h>
  45 # endif
  46
  47 /* Upper bound on getdtablesize().  See lib/getdtablesize.c.  */
  48 # define OPEN_MAX_MAX 0x10000
  49
  50 /* Duplicate OLDFD into the first available slot of at least NEWFD,
  51    which must be positive, with FLAGS determining whether the duplicate
  52    will be inheritable.  */
  53 static int
  54 dupfd (int oldfd, int newfd, int flags)
  55 {
  56   /* Mingw has no way to create an arbitrary fd.  Iterate until all
  57      file descriptors less than newfd are filled up.  */
  58   HANDLE curr_process = GetCurrentProcess ();
  59   HANDLE old_handle = (HANDLE) _get_osfhandle (oldfd);
  60   unsigned char fds_to_close[OPEN_MAX_MAX / CHAR_BIT];
  61   unsigned int fds_to_close_bound = 0;
  62   int result;
  63   BOOL inherit = flags & O_CLOEXEC ? FALSE : TRUE;
  64   int mode;
  65
  66   if (newfd < 0 || getdtablesize () <= newfd)
  67     {
  68       errno = EINVAL;
  69       return -1;
  70     }
  71   if (old_handle == INVALID_HANDLE_VALUE
  72       || (mode = setmode (oldfd, O_BINARY)) == -1)
  73     {
  74       /* oldfd is not open, or is an unassigned standard file
  75          descriptor.  */
  76       errno = EBADF;
  77       return -1;
  78     }
  79   setmode (oldfd, mode);
  80   flags |= mode;
  81
  82   for (;;)
  83     {
  84       HANDLE new_handle;
  85       int duplicated_fd;
  86       unsigned int index;
  87
  88       if (!DuplicateHandle (curr_process,           /* SourceProcessHandle */
  89                             old_handle,             /* SourceHandle */
  90                             curr_process,           /* TargetProcessHandle */
  91                             (PHANDLE) &new_handle,  /* TargetHandle */
  92                             (DWORD) 0,              /* DesiredAccess */
  93                             inherit,                /* InheritHandle */
  94                             DUPLICATE_SAME_ACCESS)) /* Options */
  95         {
  96           switch (GetLastError ())
  97             {
  98               case ERROR_TOO_MANY_OPEN_FILES:
  99                 errno = EMFILE;
 100                 break;
 101               case ERROR_INVALID_HANDLE:
 102               case ERROR_INVALID_TARGET_HANDLE:
 103               case ERROR_DIRECT_ACCESS_HANDLE:
 104                 errno = EBADF;
 105                 break;
 106               case ERROR_INVALID_PARAMETER:
 107               case ERROR_INVALID_FUNCTION:
 108               case ERROR_INVALID_ACCESS:
 109                 errno = EINVAL;
 110                 break;
 111               default:
 112                 errno = EACCES;
 113                 break;
 114             }
 115           result = -1;
 116           break;
 117         }
 118       duplicated_fd = _open_osfhandle ((intptr_t) new_handle, flags);
 119       if (duplicated_fd < 0)
 120         {
 121           CloseHandle (new_handle);
 122           result = -1;
 123           break;
 124         }
 125       if (newfd <= duplicated_fd)
 126         {
 127           result = duplicated_fd;
 128           break;
 129         }
 130
 131       /* Set the bit duplicated_fd in fds_to_close[].  */
 132       index = (unsigned int) duplicated_fd / CHAR_BIT;
 133       if (fds_to_close_bound <= index)
 134         {
 135           if (sizeof fds_to_close <= index)
 136             /* Need to increase OPEN_MAX_MAX.  */
 137             abort ();
 138           memset (fds_to_close + fds_to_close_bound, '\0',
 139                   index + 1 - fds_to_close_bound);
 140           fds_to_close_bound = index + 1;
 141         }
 142       fds_to_close[index] |= 1 << ((unsigned int) duplicated_fd % CHAR_BIT);
 143     }
 144
 145   /* Close the previous fds that turned out to be too small.  */
 146   {
 147     int saved_errno = errno;
 148     unsigned int duplicated_fd;
 149
 150     for (duplicated_fd = 0;
 151          duplicated_fd < fds_to_close_bound * CHAR_BIT;
 152          duplicated_fd++)
 153       if ((fds_to_close[duplicated_fd / CHAR_BIT]
 154            >> (duplicated_fd % CHAR_BIT))
 155           & 1)
 156         close (duplicated_fd);
 157
 158     errno = saved_errno;
 159   }
 160
 161 # if REPLACE_FCHDIR
 162   if (0 <= result)
 163     result = _gl_register_dup (oldfd, result);
 164 # endif
 165   return result;
 166 }
 167 #endif /* W32 */
 168
 169 #ifdef __KLIBC__
 170
 171 # define INCL_DOS
 172 # include <os2.h>
 173
 174 static int
 175 klibc_fcntl (int fd, int action, /* arg */...)
 176 {
 177   va_list arg_ptr;
 178   int arg;
 179   struct stat sbuf;
 180   int result = -1;
 181
 182   va_start (arg_ptr, action);
 183   arg = va_arg (arg_ptr, int);
 184   result = fcntl (fd, action, arg);
 185   /* EPERM for F_DUPFD, ENOTSUP for others */
 186   if (result == -1 && (errno == EPERM || errno == ENOTSUP)
 187       && !fstat (fd, &sbuf) && S_ISDIR (sbuf.st_mode))
 188   {
 189     ULONG ulMode;
 190
 191     switch (action)
 192       {
 193       case F_DUPFD:
 194         /* Find available fd */
 195         while (fcntl (arg, F_GETFL) != -1 || errno != EBADF)
 196           arg++;
 197
 198         result = dup2 (fd, arg);
 199         break;
 200
 201       /* Using underlying APIs is right ? */
 202       case F_GETFD:
 203         if (DosQueryFHState (fd, &ulMode))
 204           break;
 205
 206         result = (ulMode & OPEN_FLAGS_NOINHERIT) ? FD_CLOEXEC : 0;
 207         break;
 208
 209       case F_SETFD:
 210         if (arg & ~FD_CLOEXEC)
 211           break;
 212
 213         if (DosQueryFHState (fd, &ulMode))
 214           break;
 215
 216         if (arg & FD_CLOEXEC)
 217           ulMode |= OPEN_FLAGS_NOINHERIT;
 218         else
 219           ulMode &= ~OPEN_FLAGS_NOINHERIT;
 220
 221         /* Filter supported flags.  */
 222         ulMode &= (OPEN_FLAGS_WRITE_THROUGH | OPEN_FLAGS_FAIL_ON_ERROR
 223                    | OPEN_FLAGS_NO_CACHE | OPEN_FLAGS_NOINHERIT);
 224
 225         if (DosSetFHState (fd, ulMode))
 226           break;
 227
 228         result = 0;
 229         break;
 230
 231       case F_GETFL:
 232         result = 0;
 233         break;
 234
 235       case F_SETFL:
 236         if (arg != 0)
 237           break;
 238
 239         result = 0;
 240         break;
 241
 242       default :
 243         errno = EINVAL;
 244         break;
 245       }
 246   }
 247
 248   va_end (arg_ptr);
 249
 250   return result;
 251 }
 252
 253 # define fcntl klibc_fcntl
 254 #endif
 255
 256 /* Perform the specified ACTION on the file descriptor FD, possibly
 257    using the argument ARG further described below.  This replacement
 258    handles the following actions, and forwards all others on to the
 259    native fcntl.  An unrecognized ACTION returns -1 with errno set to
 260    EINVAL.
 261
 262    F_DUPFD - duplicate FD, with int ARG being the minimum target fd.
 263    If successful, return the duplicate, which will be inheritable;
 264    otherwise return -1 and set errno.
 265
 266    F_DUPFD_CLOEXEC - duplicate FD, with int ARG being the minimum
 267    target fd.  If successful, return the duplicate, which will not be
 268    inheritable; otherwise return -1 and set errno.
 269
 270    F_GETFD - ARG need not be present.  If successful, return a
 271    non-negative value containing the descriptor flags of FD (only
 272    FD_CLOEXEC is portable, but other flags may be present); otherwise
 273    return -1 and set errno.  */
 274
 275 int
 276 rpl_fcntl (int fd, int action, /* arg */...)
 277 {
 278   va_list arg;
 279   int result = -1;
 280   va_start (arg, action);
 281   switch (action)
 282     {
 283
 284 #if !HAVE_FCNTL
 285     case F_DUPFD:
 286       {
 287         int target = va_arg (arg, int);
 288         result = dupfd (fd, target, 0);
 289         break;
 290       }
 291 #elif FCNTL_DUPFD_BUGGY || REPLACE_FCHDIR
 292     case F_DUPFD:
 293       {
 294         int target = va_arg (arg, int);
 295         /* Detect invalid target; needed for cygwin 1.5.x.  */
 296         if (target < 0 || getdtablesize () <= target)
 297           errno = EINVAL;
 298         else
 299           {
 300             /* Haiku alpha 2 loses fd flags on original.  */
 301             int flags = fcntl (fd, F_GETFD);
 302             if (flags < 0)
 303               {
 304                 result = -1;
 305                 break;
 306               }
 307             result = fcntl (fd, action, target);
 308             if (0 <= result && fcntl (fd, F_SETFD, flags) == -1)
 309               {
 310                 int saved_errno = errno;
 311                 close (result);
 312                 result = -1;
 313                 errno = saved_errno;
 314               }
 315 # if REPLACE_FCHDIR
 316             if (0 <= result)
 317               result = _gl_register_dup (fd, result);
 318 # endif
 319           }
 320         break;
 321       } /* F_DUPFD */
 322 #endif /* FCNTL_DUPFD_BUGGY || REPLACE_FCHDIR */
 323
 324     case F_DUPFD_CLOEXEC:
 325       {
 326         int target = va_arg (arg, int);
 327
 328 #if !HAVE_FCNTL
 329         result = dupfd (fd, target, O_CLOEXEC);
 330         break;
 331 #else /* HAVE_FCNTL */
 332         /* Try the system call first, if the headers claim it exists
 333            (that is, if GNULIB_defined_F_DUPFD_CLOEXEC is 0), since we
 334            may be running with a glibc that has the macro but with an
 335            older kernel that does not support it.  Cache the
 336            information on whether the system call really works, but
 337            avoid caching failure if the corresponding F_DUPFD fails
 338            for any reason.  0 = unknown, 1 = yes, -1 = no.  */
 339         static int have_dupfd_cloexec = GNULIB_defined_F_DUPFD_CLOEXEC ? -1 : 0;
 340         if (0 <= have_dupfd_cloexec)
 341           {
 342             result = fcntl (fd, action, target);
 343             if (0 <= result || errno != EINVAL)
 344               {
 345                 have_dupfd_cloexec = 1;
 346 # if REPLACE_FCHDIR
 347                 if (0 <= result)
 348                   result = _gl_register_dup (fd, result);
 349 # endif
 350               }
 351             else
 352               {
 353                 result = rpl_fcntl (fd, F_DUPFD, target);
 354                 if (result < 0)
 355                   break;
 356                 have_dupfd_cloexec = -1;
 357               }
 358           }
 359         else
 360           result = rpl_fcntl (fd, F_DUPFD, target);
 361         if (0 <= result && have_dupfd_cloexec == -1)
 362           {
 363             int flags = fcntl (result, F_GETFD);
 364             if (flags < 0 || fcntl (result, F_SETFD, flags | FD_CLOEXEC) == -1)
 365               {
 366                 int saved_errno = errno;
 367                 close (result);
 368                 errno = saved_errno;
 369                 result = -1;
 370               }
 371           }
 372         break;
 373 #endif /* HAVE_FCNTL */
 374       } /* F_DUPFD_CLOEXEC */
 375
 376 #if !HAVE_FCNTL
 377     case F_GETFD:
 378       {
 379 # if (defined _WIN32 || defined __WIN32__) && ! defined __CYGWIN__
 380         HANDLE handle = (HANDLE) _get_osfhandle (fd);
 381         DWORD flags;
 382         if (handle == INVALID_HANDLE_VALUE
 383             || GetHandleInformation (handle, &flags) == 0)
 384           errno = EBADF;
 385         else
 386           result = (flags & HANDLE_FLAG_INHERIT) ? 0 : FD_CLOEXEC;
 387 # else /* !W32 */
 388         /* Use dup2 to reject invalid file descriptors.  No way to
 389            access this information, so punt.  */
 390         if (0 <= dup2 (fd, fd))
 391           result = 0;
 392 # endif /* !W32 */
 393         break;
 394       } /* F_GETFD */
 395 #endif /* !HAVE_FCNTL */
 396
 397       /* Implementing F_SETFD on mingw is not trivial - there is no
 398          API for changing the O_NOINHERIT bit on an fd, and merely
 399          changing the HANDLE_FLAG_INHERIT bit on the underlying handle
 400          can lead to odd state.  It may be possible by duplicating the
 401          handle, using _open_osfhandle with the right flags, then
 402          using dup2 to move the duplicate onto the original, but that
 403          is not supported for now.  */
 404
 405     default:
 406       {
 407 #if HAVE_FCNTL
 408         void *p = va_arg (arg, void *);
 409         result = fcntl (fd, action, p);
 410 #else
 411         errno = EINVAL;
 412 #endif
 413         break;
 414       }
 415     }
 416   va_end (arg);
 417   return result;
 418 }