hurd/alloc-fd.c

   1 /* Copyright (C) 1994-2022 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     {
  38       errno = EINVAL;
  39       return NULL;
  40     }
  41
  42   crit = _hurd_critical_section_lock ();
  43
  44   __mutex_lock (&_hurd_dtable_lock);
  45
  46  search:
  47   for (i = first_fd; i < _hurd_dtablesize; ++i)
  48     {
  49       struct hurd_fd *d = _hurd_dtable[i];
  50       if (d == NULL)
  51         {
  52           /* Allocate a new descriptor structure for this slot,
  53              initializing its port cells to nil.  The test below will catch
  54              and return this descriptor cell after locking it.  */
  55           d = _hurd_new_fd (MACH_PORT_NULL, MACH_PORT_NULL);
  56           if (d == NULL)
  57             {
  58               __mutex_unlock (&_hurd_dtable_lock);
  59               _hurd_critical_section_unlock (crit);
  60               return NULL;
  61             }
  62           _hurd_dtable[i] = d;
  63         }
  64
  65       __spin_lock (&d->port.lock);
  66       if (d->port.port == MACH_PORT_NULL)
  67         {
  68           __mutex_unlock (&_hurd_dtable_lock);
  69           _hurd_critical_section_unlock (crit);
  70           if (fd != NULL)
  71             *fd = i;
  72           return d;
  73         }
  74       else
  75         __spin_unlock (&d->port.lock);
  76     }
  77
  78   __mutex_lock (&_hurd_rlimit_lock);
  79   rlimit = _hurd_rlimits[RLIMIT_OFILE].rlim_cur;
  80   __mutex_unlock (&_hurd_rlimit_lock);
  81
  82   if (first_fd < rlimit)
  83     {
  84       /* The descriptor table is full.  Check if we have reached the
  85          resource limit, or only the allocated size.  */
  86       if (_hurd_dtablesize < rlimit)
  87         {
  88           /* Enlarge the table.  */
  89           int save = errno;
  90           struct hurd_fd **new;
  91           /* Try to double the table size, but don't exceed the limit,
  92              and make sure it exceeds FIRST_FD.  */
  93           int size = _hurd_dtablesize * 2;
  94           if (size > rlimit)
  95             size = rlimit;
  96           else if (size <= first_fd)
  97             size = first_fd + 1;
  98
  99           if (size * sizeof (*_hurd_dtable) < size)
 100             {
 101               /* Integer overflow! */
 102               errno = ENOMEM;
 103               goto out;
 104             }
 105
 106           /* If we fail to allocate that, decrement the desired size
 107              until we succeed in allocating it.  */
 108           do
 109             new = realloc (_hurd_dtable, size * sizeof (*_hurd_dtable));
 110           while (new == NULL && size-- > first_fd);
 111
 112           if (new != NULL)
 113             {
 114               /* We managed to allocate a new table.  Now install it.  */
 115               errno = save;
 116               if (first_fd < _hurd_dtablesize)
 117                 first_fd = _hurd_dtablesize;
 118               /* Initialize the new slots.  */
 119               for (i = _hurd_dtablesize; i < size; ++i)
 120                 new[i] = NULL;
 121               _hurd_dtablesize = size;
 122               _hurd_dtable = new;
 123               /* Go back to the loop to initialize the first new slot.  */
 124               goto search;
 125             }
 126           else
 127             errno = ENOMEM;
 128         }
 129       else
 130         errno = EMFILE;
 131     }
 132   else
 133     errno = EINVAL;             /* Bogus FIRST_FD value.  */
 134
 135  out:
 136   __mutex_unlock (&_hurd_dtable_lock);
 137   _hurd_critical_section_unlock (crit);
 138
 139   return NULL;
 140 }