sysdeps/mach/hurd/mmap.c

   1 /* Copyright (C) 1994-2018 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    <http://www.gnu.org/licenses/>.  */
  17
  18 #include <sys/types.h>
  19 #include <sys/mman.h>
  20 #include <errno.h>
  21 #include <hurd.h>
  22 #include <hurd/fd.h>
  23
  24 /* Map addresses starting near ADDR and extending for LEN bytes.  from
  25    OFFSET into the file FD describes according to PROT and FLAGS.  If ADDR
  26    is nonzero, it is the desired mapping address.  If the MAP_FIXED bit is
  27    set in FLAGS, the mapping will be at ADDR exactly (which must be
  28    page-aligned); otherwise the system chooses a convenient nearby address.
  29    The return value is the actual mapping address chosen or (void *) -1
  30    for errors (in which case `errno' is set).  A successful `mmap' call
  31    deallocates any previous mapping for the affected region.  */
  32
  33 void *
  34 __mmap (void *addr, size_t len, int prot, int flags, int fd, off_t offset)
  35 {
  36   error_t err;
  37   vm_prot_t vmprot;
  38   memory_object_t memobj;
  39   vm_address_t mapaddr;
  40
  41   mapaddr = (vm_address_t) addr;
  42
  43   /* ADDR and OFFSET must be page-aligned.  */
  44   if ((mapaddr & (__vm_page_size - 1)) || (offset & (__vm_page_size - 1)))
  45     return (void *) (long int) __hurd_fail (EINVAL);
  46
  47   if ((flags & (MAP_TYPE|MAP_INHERIT)) == MAP_ANON
  48       && prot == (PROT_READ|PROT_WRITE)) /* cf VM_PROT_DEFAULT */
  49     {
  50       /* vm_allocate has (a little) less overhead in the kernel too.  */
  51       err = __vm_allocate (__mach_task_self (), &mapaddr, len, mapaddr == 0);
  52
  53       if (err == KERN_NO_SPACE)
  54         {
  55           if (flags & MAP_FIXED)
  56             {
  57               /* XXX this is not atomic as it is in unix! */
  58               /* The region is already allocated; deallocate it first.  */
  59               err = __vm_deallocate (__mach_task_self (), mapaddr, len);
  60               if (!err)
  61                 err = __vm_allocate (__mach_task_self (), &mapaddr, len, 0);
  62             }
  63           else if (mapaddr != 0)
  64             err = __vm_allocate (__mach_task_self (), &mapaddr, len, 1);
  65         }
  66
  67       return err ? (void *) (long int) __hurd_fail (err) : (void *) mapaddr;
  68     }
  69
  70   vmprot = VM_PROT_NONE;
  71   if (prot & PROT_READ)
  72     vmprot |= VM_PROT_READ;
  73   if (prot & PROT_WRITE)
  74     vmprot |= VM_PROT_WRITE;
  75   if (prot & PROT_EXEC)
  76     vmprot |= VM_PROT_EXECUTE;
  77
  78   switch (flags & MAP_TYPE)
  79     {
  80     default:
  81       return (void *) (long int) __hurd_fail (EINVAL);
  82
  83     case MAP_ANON:
  84       memobj = MACH_PORT_NULL;
  85       break;
  86
  87     case MAP_FILE:
  88     case 0:                     /* Allow, e.g., just MAP_SHARED.  */
  89       {
  90         mach_port_t robj, wobj;
  91         if (err = HURD_DPORT_USE (fd, __io_map (port, &robj, &wobj)))
  92           {
  93             if (err == MIG_BAD_ID || err == EOPNOTSUPP || err == ENOSYS)
  94               err = ENODEV;     /* File descriptor doesn't support mmap.  */
  95             return (void *) (long int) __hurd_dfail (fd, err);
  96           }
  97         switch (prot & (PROT_READ|PROT_WRITE))
  98           {
  99           /* Although it apparently doesn't make sense to map a file with
 100              protection set to PROT_NONE, it is actually sometimes done.
 101              In particular, that's how localedef reserves some space for
 102              the locale archive file, the rationale being that some
 103              implementations take into account whether the mapping is
 104              anonymous or not when selecting addresses.  */
 105           case PROT_NONE:
 106           case PROT_READ:
 107             memobj = robj;
 108             if (wobj != MACH_PORT_NULL)
 109               __mach_port_deallocate (__mach_task_self (), wobj);
 110             break;
 111           case PROT_WRITE:
 112             memobj = wobj;
 113             if (robj != MACH_PORT_NULL)
 114               __mach_port_deallocate (__mach_task_self (), robj);
 115             break;
 116           case PROT_READ|PROT_WRITE:
 117             if (robj == wobj)
 118               {
 119                 memobj = wobj;
 120                 /* Remove extra reference.  */
 121                 __mach_port_deallocate (__mach_task_self (), memobj);
 122               }
 123             else if (wobj == MACH_PORT_NULL && /* Not writable by mapping.  */
 124                      !(flags & MAP_SHARED))
 125               /* The file can only be mapped for reading.  Since we are
 126                  making a private mapping, we will never try to write the
 127                  object anyway, so we don't care.  */
 128               memobj = robj;
 129             else
 130               {
 131                 __mach_port_deallocate (__mach_task_self (), wobj);
 132                 return (void *) (long int) __hurd_fail (EACCES);
 133               }
 134             break;
 135           default:
 136             __builtin_unreachable ();
 137           }
 138         break;
 139         /* XXX handle MAP_NOEXTEND */
 140       }
 141     }
 142
 143   /* XXX handle MAP_INHERIT */
 144
 145   err = __vm_map (__mach_task_self (),
 146                   &mapaddr, (vm_size_t) len, (vm_address_t) 0,
 147                   mapaddr == 0,
 148                   memobj, (vm_offset_t) offset,
 149                   ! (flags & MAP_SHARED),
 150                   vmprot, VM_PROT_ALL,
 151                   (flags & MAP_SHARED) ? VM_INHERIT_SHARE : VM_INHERIT_COPY);
 152
 153   if (err == KERN_NO_SPACE)
 154     {
 155       if (flags & MAP_FIXED)
 156         {
 157           /* XXX this is not atomic as it is in unix! */
 158           /* The region is already allocated; deallocate it first.  */
 159           err = __vm_deallocate (__mach_task_self (), mapaddr, len);
 160           if (! err)
 161             err = __vm_map (__mach_task_self (),
 162                             &mapaddr, (vm_size_t) len, (vm_address_t) 0,
 163                             0, memobj, (vm_offset_t) offset,
 164                             ! (flags & MAP_SHARED),
 165                             vmprot, VM_PROT_ALL,
 166                             (flags & MAP_SHARED) ? VM_INHERIT_SHARE
 167                             : VM_INHERIT_COPY);
 168         }
 169       else if (mapaddr != 0)
 170         err = __vm_map (__mach_task_self (),
 171                         &mapaddr, (vm_size_t) len, (vm_address_t) 0,
 172                         1, memobj, (vm_offset_t) offset,
 173                         ! (flags & MAP_SHARED),
 174                         vmprot, VM_PROT_ALL,
 175                         (flags & MAP_SHARED) ? VM_INHERIT_SHARE
 176                         : VM_INHERIT_COPY);
 177     }
 178
 179   if (memobj != MACH_PORT_NULL)
 180     __mach_port_deallocate (__mach_task_self (), memobj);
 181
 182   if (err)
 183     return (void *) (long int) __hurd_fail (err);
 184
 185   return (void *) mapaddr;
 186 }
 187
 188 libc_hidden_def (__mmap)
 189 weak_alias (__mmap, mmap)