hurd/alloc-fd.c

   1 /* Copyright (C) 1994-2024 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3
   4    The GNU C Library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU Lesser General Public
   6    License as published by the Free Software Foundation; either
   7    version 2.1 of the License, or (at your option) any later version.
   8
   9    The GNU C Library is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12    Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public
  15    License along with the GNU C Library; if not, see
  16    <https://www.gnu.org/licenses/>.  */
  17
  18 #include <hurd.h>
  19 #include <hurd/fd.h>
  20 #include <hurd/resource.h>
  21 #include <stdlib.h>
  22 #include "hurdmalloc.h"         /* XXX */
  23
  24 /* Allocate a new file descriptor and return it, locked.  The new
  25    descriptor number will be no less than FIRST_FD.  If the table is full,
  26    set errno to EMFILE and return NULL.  If FIRST_FD is negative or bigger
  27    than the size of the table, set errno to EINVAL and return NULL.  */
  28
  29 struct hurd_fd *
  30 _hurd_alloc_fd (int *fd, int first_fd)
  31 {
  32   int i;
  33   void *crit;
  34   long int rlimit;
  35
  36   if (first_fd < 0)
  37     return __hurd_fail (EINVAL), NULL;
  38
  39   crit = _hurd_critical_section_lock ();
  40
  41   __mutex_lock (&_hurd_dtable_lock);
  42
  43  search:
  44   for (i = first_fd; i < _hurd_dtablesize; ++i)
  45     {
  46       struct hurd_fd *d = _hurd_dtable[i];
  47       if (d == NULL)
  48         {
  49           /* Allocate a new descriptor structure for this slot,
  50              initializing its port cells to nil.  The test below will catch
  51              and return this descriptor cell after locking it.  */
  52           d = _hurd_new_fd (MACH_PORT_NULL, MACH_PORT_NULL);
  53           if (d == NULL)
  54             {
  55               __mutex_unlock (&_hurd_dtable_lock);
  56               _hurd_critical_section_unlock (crit);
  57               return NULL;
  58             }
  59           _hurd_dtable[i] = d;
  60         }
  61
  62       __spin_lock (&d->port.lock);
  63       if (d->port.port == MACH_PORT_NULL)
  64         {
  65           __mutex_unlock (&_hurd_dtable_lock);
  66           _hurd_critical_section_unlock (crit);
  67           if (fd != NULL)
  68             *fd = i;
  69           return d;
  70         }
  71       else
  72         __spin_unlock (&d->port.lock);
  73     }
  74
  75   __mutex_lock (&_hurd_rlimit_lock);
  76   rlimit = _hurd_rlimits[RLIMIT_OFILE].rlim_cur;
  77   __mutex_unlock (&_hurd_rlimit_lock);
  78
  79   if (first_fd < rlimit)
  80     {
  81       /* The descriptor table is full.  Check if we have reached the
  82          resource limit, or only the allocated size.  */
  83       if (_hurd_dtablesize < rlimit)
  84         {
  85           /* Enlarge the table.  */
  86           int save = errno;
  87           struct hurd_fd **new;
  88           /* Try to double the table size, but don't exceed the limit,
  89              and make sure it exceeds FIRST_FD.  */
  90           int size = _hurd_dtablesize * 2;
  91           if (size > rlimit)
  92             size = rlimit;
  93           else if (size <= first_fd)
  94             size = first_fd + 1;
  95
  96           if (size * sizeof (*_hurd_dtable) < size)
  97             {
  98               /* Integer overflow! */
  99               __hurd_fail (ENOMEM);
 100               goto out;
 101             }
 102
 103           /* If we fail to allocate that, decrement the desired size
 104              until we succeed in allocating it.  */
 105           do
 106             new = realloc (_hurd_dtable, size * sizeof (*_hurd_dtable));
 107           while (new == NULL && size-- > first_fd);
 108
 109           if (new != NULL)
 110             {
 111               /* We managed to allocate a new table.  Now install it.  */
 112               errno = save;
 113               if (first_fd < _hurd_dtablesize)
 114                 first_fd = _hurd_dtablesize;
 115               /* Initialize the new slots.  */
 116               for (i = _hurd_dtablesize; i < size; ++i)
 117                 new[i] = NULL;
 118               _hurd_dtablesize = size;
 119               _hurd_dtable = new;
 120               /* Go back to the loop to initialize the first new slot.  */
 121               goto search;
 122             }
 123           else
 124             __hurd_fail (ENOMEM);
 125         }
 126       else
 127         __hurd_fail (EMFILE);
 128     }
 129   else
 130     __hurd_fail (EINVAL);       /* Bogus FIRST_FD value.  */
 131
 132  out:
 133   __mutex_unlock (&_hurd_dtable_lock);
 134   _hurd_critical_section_unlock (crit);
 135
 136   return NULL;
 137 }