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