summaryrefslogtreecommitdiff
path: root/lib/fcntl.c
blob: 735fa66f4d76484b2a3177c9f7f56ff61d95542d (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
/* Provide file descriptor control.

   Copyright (C) 2009-2013 Free Software Foundation, Inc.

   This program is free software: you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 3 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */

/* Written by Eric Blake <ebb9@byu.net>.  */

#include <config.h>

/* Specification.  */
#include <fcntl.h>

#include <errno.h>
#include <limits.h>
#include <stdarg.h>
#include <unistd.h>

#if !HAVE_FCNTL
# define rpl_fcntl fcntl
#endif
#undef fcntl

#if (defined _WIN32 || defined __WIN32__) && ! defined __CYGWIN__
/* Get declarations of the native Windows API functions.  */
# define WIN32_LEAN_AND_MEAN
# include <windows.h>

/* Get _get_osfhandle.  */
# include "msvc-nothrow.h"

/* Upper bound on getdtablesize().  See lib/getdtablesize.c.  */
# define OPEN_MAX_MAX 0x10000

/* Duplicate OLDFD into the first available slot of at least NEWFD,
   which must be positive, with FLAGS determining whether the duplicate
   will be inheritable.  */
static int
dupfd (int oldfd, int newfd, int flags)
{
  /* Mingw has no way to create an arbitrary fd.  Iterate until all
     file descriptors less than newfd are filled up.  */
  HANDLE curr_process = GetCurrentProcess ();
  HANDLE old_handle = (HANDLE) _get_osfhandle (oldfd);
  unsigned char fds_to_close[OPEN_MAX_MAX / CHAR_BIT];
  unsigned int fds_to_close_bound = 0;
  int result;
  BOOL inherit = flags & O_CLOEXEC ? FALSE : TRUE;
  int mode;

  if (newfd < 0 || getdtablesize () <= newfd)
    {
      errno = EINVAL;
      return -1;
    }
  if (old_handle == INVALID_HANDLE_VALUE
      || (mode = setmode (oldfd, O_BINARY)) == -1)
    {
      /* oldfd is not open, or is an unassigned standard file
         descriptor.  */
      errno = EBADF;
      return -1;
    }
  setmode (oldfd, mode);
  flags |= mode;

  for (;;)
    {
      HANDLE new_handle;
      int duplicated_fd;
      unsigned int index;

      if (!DuplicateHandle (curr_process,           /* SourceProcessHandle */
                            old_handle,             /* SourceHandle */
                            curr_process,           /* TargetProcessHandle */
                            (PHANDLE) &new_handle,  /* TargetHandle */
                            (DWORD) 0,              /* DesiredAccess */
                            inherit,                /* InheritHandle */
                            DUPLICATE_SAME_ACCESS)) /* Options */
        {
          /* TODO: Translate GetLastError () into errno.  */
          errno = EMFILE;
          result = -1;
          break;
        }
      duplicated_fd = _open_osfhandle ((intptr_t) new_handle, flags);
      if (duplicated_fd < 0)
        {
          CloseHandle (new_handle);
          errno = EMFILE;
          result = -1;
          break;
        }
      if (newfd <= duplicated_fd)
        {
          result = duplicated_fd;
          break;
        }

      /* Set the bit duplicated_fd in fds_to_close[].  */
      index = (unsigned int) duplicated_fd / CHAR_BIT;
      if (fds_to_close_bound <= index)
        {
          if (sizeof fds_to_close <= index)
            /* Need to increase OPEN_MAX_MAX.  */
            abort ();
          memset (fds_to_close + fds_to_close_bound, '\0',
                  index + 1 - fds_to_close_bound);
          fds_to_close_bound = index + 1;
        }
      fds_to_close[index] |= 1 << ((unsigned int) duplicated_fd % CHAR_BIT);
    }

  /* Close the previous fds that turned out to be too small.  */
  {
    int saved_errno = errno;
    unsigned int duplicated_fd;

    for (duplicated_fd = 0;
         duplicated_fd < fds_to_close_bound * CHAR_BIT;
         duplicated_fd++)
      if ((fds_to_close[duplicated_fd / CHAR_BIT]
           >> (duplicated_fd % CHAR_BIT))
          & 1)
        close (duplicated_fd);

    errno = saved_errno;
  }

# if REPLACE_FCHDIR
  if (0 <= result)
    result = _gl_register_dup (oldfd, result);
# endif
  return result;
}
#endif /* W32 */

/* Perform the specified ACTION on the file descriptor FD, possibly
   using the argument ARG further described below.  This replacement
   handles the following actions, and forwards all others on to the
   native fcntl.  An unrecognized ACTION returns -1 with errno set to
   EINVAL.

   F_DUPFD - duplicate FD, with int ARG being the minimum target fd.
   If successful, return the duplicate, which will be inheritable;
   otherwise return -1 and set errno.

   F_DUPFD_CLOEXEC - duplicate FD, with int ARG being the minimum
   target fd.  If successful, return the duplicate, which will not be
   inheritable; otherwise return -1 and set errno.

   F_GETFD - ARG need not be present.  If successful, return a
   non-negative value containing the descriptor flags of FD (only
   FD_CLOEXEC is portable, but other flags may be present); otherwise
   return -1 and set errno.  */

int
rpl_fcntl (int fd, int action, /* arg */...)
{
  va_list arg;
  int result = -1;
  va_start (arg, action);
  switch (action)
    {

#if !HAVE_FCNTL
    case F_DUPFD:
      {
        int target = va_arg (arg, int);
        result = dupfd (fd, target, 0);
        break;
      }
#elif FCNTL_DUPFD_BUGGY || REPLACE_FCHDIR
    case F_DUPFD:
      {
        int target = va_arg (arg, int);
        /* Detect invalid target; needed for cygwin 1.5.x.  */
        if (target < 0 || getdtablesize () <= target)
          errno = EINVAL;
        else
          {
            /* Haiku alpha 2 loses fd flags on original.  */
            int flags = fcntl (fd, F_GETFD);
            if (flags < 0)
              {
                result = -1;
                break;
              }
            result = fcntl (fd, action, target);
            if (0 <= result && fcntl (fd, F_SETFD, flags) == -1)
              {
                int saved_errno = errno;
                close (result);
                result = -1;
                errno = saved_errno;
              }
# if REPLACE_FCHDIR
            if (0 <= result)
              result = _gl_register_dup (fd, result);
# endif
          }
        break;
      } /* F_DUPFD */
#endif /* FCNTL_DUPFD_BUGGY || REPLACE_FCHDIR */

    case F_DUPFD_CLOEXEC:
      {
        int target = va_arg (arg, int);

#if !HAVE_FCNTL
        result = dupfd (fd, target, O_CLOEXEC);
        break;
#else /* HAVE_FCNTL */
        /* Try the system call first, if the headers claim it exists
           (that is, if GNULIB_defined_F_DUPFD_CLOEXEC is 0), since we
           may be running with a glibc that has the macro but with an
           older kernel that does not support it.  Cache the
           information on whether the system call really works, but
           avoid caching failure if the corresponding F_DUPFD fails
           for any reason.  0 = unknown, 1 = yes, -1 = no.  */
        static int have_dupfd_cloexec = GNULIB_defined_F_DUPFD_CLOEXEC ? -1 : 0;
        if (0 <= have_dupfd_cloexec)
          {
            result = fcntl (fd, action, target);
            if (0 <= result || errno != EINVAL)
              {
                have_dupfd_cloexec = 1;
# if REPLACE_FCHDIR
                if (0 <= result)
                  result = _gl_register_dup (fd, result);
# endif
              }
            else
              {
                result = rpl_fcntl (fd, F_DUPFD, target);
                if (result < 0)
                  break;
                have_dupfd_cloexec = -1;
              }
          }
        else
          result = rpl_fcntl (fd, F_DUPFD, target);
        if (0 <= result && have_dupfd_cloexec == -1)
          {
            int flags = fcntl (result, F_GETFD);
            if (flags < 0 || fcntl (result, F_SETFD, flags | FD_CLOEXEC) == -1)
              {
                int saved_errno = errno;
                close (result);
                errno = saved_errno;
                result = -1;
              }
          }
        break;
#endif /* HAVE_FCNTL */
      } /* F_DUPFD_CLOEXEC */

#if !HAVE_FCNTL
    case F_GETFD:
      {
# if (defined _WIN32 || defined __WIN32__) && ! defined __CYGWIN__
        HANDLE handle = (HANDLE) _get_osfhandle (fd);
        DWORD flags;
        if (handle == INVALID_HANDLE_VALUE
            || GetHandleInformation (handle, &flags) == 0)
          errno = EBADF;
        else
          result = (flags & HANDLE_FLAG_INHERIT) ? 0 : FD_CLOEXEC;
# else /* !W32 */
        /* Use dup2 to reject invalid file descriptors.  No way to
           access this information, so punt.  */
        if (0 <= dup2 (fd, fd))
          result = 0;
# endif /* !W32 */
        break;
      } /* F_GETFD */
#endif /* !HAVE_FCNTL */

      /* Implementing F_SETFD on mingw is not trivial - there is no
         API for changing the O_NOINHERIT bit on an fd, and merely
         changing the HANDLE_FLAG_INHERIT bit on the underlying handle
         can lead to odd state.  It may be possible by duplicating the
         handle, using _open_osfhandle with the right flags, then
         using dup2 to move the duplicate onto the original, but that
         is not supported for now.  */

    default:
      {
#if HAVE_FCNTL
        void *p = va_arg (arg, void *);
        result = fcntl (fd, action, p);
#else
        errno = EINVAL;
#endif
        break;
      }
    }
  va_end (arg);
  return result;
}