lib/fcntl.c

   1 /* Provide file descriptor control.
   2
   3    Copyright (C) 2009-2015 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           /* TODO: Translate GetLastError () into errno.  */
  93           errno = EMFILE;
  94           result = -1;
  95           break;
  96         }
  97       duplicated_fd = _open_osfhandle ((intptr_t) new_handle, flags);
  98       if (duplicated_fd < 0)
  99         {
 100           CloseHandle (new_handle);
 101           errno = EMFILE;
 102           result = -1;
 103           break;
 104         }
 105       if (newfd <= duplicated_fd)
 106         {
 107           result = duplicated_fd;
 108           break;
 109         }
 110
 111       /* Set the bit duplicated_fd in fds_to_close[].  */
 112       index = (unsigned int) duplicated_fd / CHAR_BIT;
 113       if (fds_to_close_bound <= index)
 114         {
 115           if (sizeof fds_to_close <= index)
 116             /* Need to increase OPEN_MAX_MAX.  */
 117             abort ();
 118           memset (fds_to_close + fds_to_close_bound, '\0',
 119                   index + 1 - fds_to_close_bound);
 120           fds_to_close_bound = index + 1;
 121         }
 122       fds_to_close[index] |= 1 << ((unsigned int) duplicated_fd % CHAR_BIT);
 123     }
 124
 125   /* Close the previous fds that turned out to be too small.  */
 126   {
 127     int saved_errno = errno;
 128     unsigned int duplicated_fd;
 129
 130     for (duplicated_fd = 0;
 131          duplicated_fd < fds_to_close_bound * CHAR_BIT;
 132          duplicated_fd++)
 133       if ((fds_to_close[duplicated_fd / CHAR_BIT]
 134            >> (duplicated_fd % CHAR_BIT))
 135           & 1)
 136         close (duplicated_fd);
 137
 138     errno = saved_errno;
 139   }
 140
 141 # if REPLACE_FCHDIR
 142   if (0 <= result)
 143     result = _gl_register_dup (oldfd, result);
 144 # endif
 145   return result;
 146 }
 147 #endif /* W32 */
 148
 149 /* Perform the specified ACTION on the file descriptor FD, possibly
 150    using the argument ARG further described below.  This replacement
 151    handles the following actions, and forwards all others on to the
 152    native fcntl.  An unrecognized ACTION returns -1 with errno set to
 153    EINVAL.
 154
 155    F_DUPFD - duplicate FD, with int ARG being the minimum target fd.
 156    If successful, return the duplicate, which will be inheritable;
 157    otherwise return -1 and set errno.
 158
 159    F_DUPFD_CLOEXEC - duplicate FD, with int ARG being the minimum
 160    target fd.  If successful, return the duplicate, which will not be
 161    inheritable; otherwise return -1 and set errno.
 162
 163    F_GETFD - ARG need not be present.  If successful, return a
 164    non-negative value containing the descriptor flags of FD (only
 165    FD_CLOEXEC is portable, but other flags may be present); otherwise
 166    return -1 and set errno.  */
 167
 168 int
 169 rpl_fcntl (int fd, int action, /* arg */...)
 170 {
 171   va_list arg;
 172   int result = -1;
 173   va_start (arg, action);
 174   switch (action)
 175     {
 176
 177 #if !HAVE_FCNTL
 178     case F_DUPFD:
 179       {
 180         int target = va_arg (arg, int);
 181         result = dupfd (fd, target, 0);
 182         break;
 183       }
 184 #elif FCNTL_DUPFD_BUGGY || REPLACE_FCHDIR
 185     case F_DUPFD:
 186       {
 187         int target = va_arg (arg, int);
 188         /* Detect invalid target; needed for cygwin 1.5.x.  */
 189         if (target < 0 || getdtablesize () <= target)
 190           errno = EINVAL;
 191         else
 192           {
 193             /* Haiku alpha 2 loses fd flags on original.  */
 194             int flags = fcntl (fd, F_GETFD);
 195             if (flags < 0)
 196               {
 197                 result = -1;
 198                 break;
 199               }
 200             result = fcntl (fd, action, target);
 201             if (0 <= result && fcntl (fd, F_SETFD, flags) == -1)
 202               {
 203                 int saved_errno = errno;
 204                 close (result);
 205                 result = -1;
 206                 errno = saved_errno;
 207               }
 208 # if REPLACE_FCHDIR
 209             if (0 <= result)
 210               result = _gl_register_dup (fd, result);
 211 # endif
 212           }
 213         break;
 214       } /* F_DUPFD */
 215 #endif /* FCNTL_DUPFD_BUGGY || REPLACE_FCHDIR */
 216
 217     case F_DUPFD_CLOEXEC:
 218       {
 219         int target = va_arg (arg, int);
 220
 221 #if !HAVE_FCNTL
 222         result = dupfd (fd, target, O_CLOEXEC);
 223         break;
 224 #else /* HAVE_FCNTL */
 225         /* Try the system call first, if the headers claim it exists
 226            (that is, if GNULIB_defined_F_DUPFD_CLOEXEC is 0), since we
 227            may be running with a glibc that has the macro but with an
 228            older kernel that does not support it.  Cache the
 229            information on whether the system call really works, but
 230            avoid caching failure if the corresponding F_DUPFD fails
 231            for any reason.  0 = unknown, 1 = yes, -1 = no.  */
 232         static int have_dupfd_cloexec = GNULIB_defined_F_DUPFD_CLOEXEC ? -1 : 0;
 233         if (0 <= have_dupfd_cloexec)
 234           {
 235             result = fcntl (fd, action, target);
 236             if (0 <= result || errno != EINVAL)
 237               {
 238                 have_dupfd_cloexec = 1;
 239 # if REPLACE_FCHDIR
 240                 if (0 <= result)
 241                   result = _gl_register_dup (fd, result);
 242 # endif
 243               }
 244             else
 245               {
 246                 result = rpl_fcntl (fd, F_DUPFD, target);
 247                 if (result < 0)
 248                   break;
 249                 have_dupfd_cloexec = -1;
 250               }
 251           }
 252         else
 253           result = rpl_fcntl (fd, F_DUPFD, target);
 254         if (0 <= result && have_dupfd_cloexec == -1)
 255           {
 256             int flags = fcntl (result, F_GETFD);
 257             if (flags < 0 || fcntl (result, F_SETFD, flags | FD_CLOEXEC) == -1)
 258               {
 259                 int saved_errno = errno;
 260                 close (result);
 261                 errno = saved_errno;
 262                 result = -1;
 263               }
 264           }
 265         break;
 266 #endif /* HAVE_FCNTL */
 267       } /* F_DUPFD_CLOEXEC */
 268
 269 #if !HAVE_FCNTL
 270     case F_GETFD:
 271       {
 272 # if (defined _WIN32 || defined __WIN32__) && ! defined __CYGWIN__
 273         HANDLE handle = (HANDLE) _get_osfhandle (fd);
 274         DWORD flags;
 275         if (handle == INVALID_HANDLE_VALUE
 276             || GetHandleInformation (handle, &flags) == 0)
 277           errno = EBADF;
 278         else
 279           result = (flags & HANDLE_FLAG_INHERIT) ? 0 : FD_CLOEXEC;
 280 # else /* !W32 */
 281         /* Use dup2 to reject invalid file descriptors.  No way to
 282            access this information, so punt.  */
 283         if (0 <= dup2 (fd, fd))
 284           result = 0;
 285 # endif /* !W32 */
 286         break;
 287       } /* F_GETFD */
 288 #endif /* !HAVE_FCNTL */
 289
 290       /* Implementing F_SETFD on mingw is not trivial - there is no
 291          API for changing the O_NOINHERIT bit on an fd, and merely
 292          changing the HANDLE_FLAG_INHERIT bit on the underlying handle
 293          can lead to odd state.  It may be possible by duplicating the
 294          handle, using _open_osfhandle with the right flags, then
 295          using dup2 to move the duplicate onto the original, but that
 296          is not supported for now.  */
 297
 298     default:
 299       {
 300 #if HAVE_FCNTL
 301         void *p = va_arg (arg, void *);
 302         result = fcntl (fd, action, p);
 303 #else
 304         errno = EINVAL;
 305 #endif
 306         break;
 307       }
 308     }
 309   va_end (arg);
 310   return result;
 311 }