sysdeps/mach/hurd/mmap.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 <sys/types.h>
  19 #include <sys/mman.h>
  20 #include <errno.h>
  21 #include <ldsodefs.h>
  22 #include <hurd.h>
  23 #include <hurd/fd.h>
  24
  25 /* Map addresses starting near ADDR and extending for LEN bytes.  from
  26    OFFSET into the file FD describes according to PROT and FLAGS.  If ADDR
  27    is nonzero, it is the desired mapping address.  If the MAP_FIXED bit is
  28    set in FLAGS, the mapping will be at ADDR exactly (which must be
  29    page-aligned); otherwise the system chooses a convenient nearby address.
  30    The return value is the actual mapping address chosen or (void *) -1
  31    for errors (in which case `errno' is set).  A successful `mmap' call
  32    deallocates any previous mapping for the affected region.  */
  33
  34 void *
  35 __mmap (void *addr, size_t len, int prot, int flags, int fd, off_t offset)
  36 {
  37   error_t err;
  38   vm_prot_t vmprot, max_vmprot;
  39   memory_object_t memobj;
  40   vm_address_t mapaddr, mask;
  41   boolean_t copy, anywhere;
  42
  43   mapaddr = (vm_address_t) addr;
  44
  45   /* ADDR and OFFSET must be page-aligned.  */
  46   if ((mapaddr & (__vm_page_size - 1)) || (offset & (__vm_page_size - 1)))
  47     return (void *) (long int) __hurd_fail (EINVAL);
  48
  49   if ((flags & MAP_EXCL) && ! (flags & MAP_FIXED))
  50     return (void *) (long int) __hurd_fail (EINVAL);
  51
  52   vmprot = VM_PROT_NONE;
  53   if (prot & PROT_READ)
  54     vmprot |= VM_PROT_READ;
  55   if (prot & PROT_WRITE)
  56     vmprot |= VM_PROT_WRITE;
  57   if (prot & PROT_EXEC)
  58     vmprot |= VM_PROT_EXECUTE;
  59
  60   copy = ! (flags & MAP_SHARED);
  61   anywhere = ! (flags & MAP_FIXED);
  62
  63 #ifdef __x86_64__
  64   if ((addr == NULL) && (prot & PROT_EXEC)
  65       && HAS_ARCH_FEATURE (Prefer_MAP_32BIT_EXEC))
  66     flags |= MAP_32BIT;
  67 #endif
  68   mask = (flags & MAP_32BIT) ? ~(vm_address_t) 0x7FFFFFFF : 0;
  69
  70   switch (flags & MAP_TYPE)
  71     {
  72     default:
  73       return (void *) (long int) __hurd_fail (EINVAL);
  74
  75     case MAP_ANON:
  76       memobj = MACH_PORT_NULL;
  77       max_vmprot = VM_PROT_ALL;
  78       break;
  79
  80     case MAP_FILE:
  81     case 0:                     /* Allow, e.g., just MAP_SHARED.  */
  82       {
  83         mach_port_t robj, wobj;
  84         if (err = HURD_DPORT_USE (fd, __io_map (port, &robj, &wobj)))
  85           {
  86             if (err == MIG_BAD_ID || err == EOPNOTSUPP || err == ENOSYS)
  87               err = ENODEV;     /* File descriptor doesn't support mmap.  */
  88             return (void *) (long int) __hurd_dfail (fd, err);
  89           }
  90         switch (prot & (PROT_READ|PROT_WRITE))
  91           {
  92           /* Although it apparently doesn't make sense to map a file with
  93              protection set to PROT_NONE, it is actually sometimes done.
  94              In particular, that's how localedef reserves some space for
  95              the locale archive file, the rationale being that some
  96              implementations take into account whether the mapping is
  97              anonymous or not when selecting addresses.  */
  98           case PROT_NONE:
  99           case PROT_READ:
 100             max_vmprot = VM_PROT_READ|VM_PROT_EXECUTE;
 101             if (wobj == robj)
 102               max_vmprot |= VM_PROT_WRITE;
 103             memobj = robj;
 104             if (MACH_PORT_VALID (wobj))
 105               __mach_port_deallocate (__mach_task_self (), wobj);
 106             break;
 107           case PROT_WRITE:
 108             max_vmprot = VM_PROT_WRITE;
 109             if (robj == wobj)
 110               max_vmprot |= VM_PROT_READ|VM_PROT_EXECUTE;
 111             memobj = wobj;
 112             if (MACH_PORT_VALID (robj))
 113               __mach_port_deallocate (__mach_task_self (), robj);
 114             break;
 115           case PROT_READ|PROT_WRITE:
 116             max_vmprot = VM_PROT_ALL;
 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                      && copy)
 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   if (copy)
 146     max_vmprot = VM_PROT_ALL;
 147
 148   /* When ANYWHERE is true but the caller has provided a preferred address,
 149      try mapping at that address with anywhere = 0 first.  If this fails,
 150      we'll retry with anywhere = 1 below.  */
 151   err = __vm_map (__mach_task_self (),
 152                   &mapaddr, (vm_size_t) len, mask,
 153                   anywhere && (mapaddr == 0),
 154                   memobj, (vm_offset_t) offset,
 155                   copy, vmprot, max_vmprot,
 156                   copy ? VM_INHERIT_COPY : VM_INHERIT_SHARE);
 157
 158   if (flags & MAP_FIXED)
 159     {
 160       if (err == KERN_NO_SPACE)
 161         {
 162           if (flags & MAP_EXCL)
 163             err = EEXIST;
 164           else
 165             {
 166               /* The region is already allocated; deallocate it first.  */
 167               /* XXX this is not atomic as it is in unix! */
 168               err = __vm_deallocate (__mach_task_self (), mapaddr, len);
 169               if (! err)
 170                 err = __vm_map (__mach_task_self (),
 171                                 &mapaddr, (vm_size_t) len, mask,
 172                                 0, memobj, (vm_offset_t) offset,
 173                                 copy, vmprot, max_vmprot,
 174                                 copy ? VM_INHERIT_COPY : VM_INHERIT_SHARE);
 175             }
 176         }
 177     }
 178   else
 179     {
 180       /* This mmap call is allowed to allocate anywhere,  */
 181       if (mapaddr != 0 && (err == KERN_NO_SPACE || err == KERN_INVALID_ADDRESS))
 182         /* ...but above, we tried allocating at the specific address,
 183            and failed to.  Now try again, with anywhere = 1 this time.  */
 184         err = __vm_map (__mach_task_self (),
 185                         &mapaddr, (vm_size_t) len, mask,
 186                         1, memobj, (vm_offset_t) offset,
 187                         copy, vmprot, max_vmprot,
 188                         copy ? VM_INHERIT_COPY : VM_INHERIT_SHARE);
 189     }
 190
 191   if (MACH_PORT_VALID (memobj))
 192     __mach_port_deallocate (__mach_task_self (), memobj);
 193
 194   if (err == KERN_PROTECTION_FAILURE)
 195     err = EACCES;
 196
 197   if (err)
 198     return (void *) (long int) __hurd_fail (err);
 199
 200   return (void *) mapaddr;
 201 }
 202
 203 libc_hidden_def (__mmap)
 204 weak_alias (__mmap, mmap)