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/* mprotect.c - mprotect implementation.
Copyright (C) 2008 Free Software Foundation, Inc.
Written by Neal H. Walfield <neal@gnu.org>.
This file is part of the GNU Hurd.
GNU Hurd is free software: you can redistribute it and/or modify it
under the terms of the GNU Lesser General Public License as
published by the Free Software Foundation, either version 3 of the
License, or (at your option) any later version.
GNU Hurd 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
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with GNU Hurd. If not, see
<http://www.gnu.org/licenses/>. */
#include <hurd/stddef.h>
#include <viengoos/addr.h>
#include <hurd/as.h>
#include <hurd/storage.h>
#include <hurd/anonymous.h>
#include <hurd/map.h>
#include <sys/mman.h>
#include <stdint.h>
int
mprotect (void *addr, size_t length, int prot)
{
uintptr_t start = (uintptr_t) addr;
uintptr_t end = start + length - 1;
debug (5, "(%p, %x (%p),%s%s)", addr, length, (void *) end,
prot == 0 ? " PROT_NONE" : (prot & PROT_READ ? " PROT_READ" : ""),
prot & PROT_WRITE ? " PROT_WRITE" : "");
struct region region = { (uintptr_t) addr, length };
enum map_access access = 0;
if ((prot & PROT_READ))
access = MAP_ACCESS_READ;
if ((prot & PROT_WRITE))
access |= MAP_ACCESS_WRITE;
maps_lock_lock ();
/* Find any pager that overlaps within the designated region. */
struct map *map = map_find (region);
if (! map)
/* There are none. We're done. */
{
maps_lock_unlock ();
return 0;
}
/* There may be pagers that come lexically before as well as after
PAGER. We start with PAGER and scan forward and then do the same
but scan backwards. */
struct map *prev = hurd_btree_map_prev (map);
int dir;
for (dir = 0; dir < 2; dir ++, map = prev)
for (;
map;
map = (dir == 0 ? hurd_btree_map_next (map)
: hurd_btree_map_prev (map)))
{
uintptr_t map_start = map->region.start;
uintptr_t map_end = map_start + map->region.length - 1;
debug (5, "(%x-%x): considering %x-%x",
start, end, map_start, map_end);
if (map_start > end || map_end < start)
break;
if (map->access == access)
/* The access is already correct. Nothing to do. */
continue;
if (map_start < start)
/* We need to split. */
{
debug (5, "(%x-%x): splitting %x-%x at offset %x",
start, end, map_start, map_end, start - map_start);
struct map *second = map_split (map, start - map_start);
if (second)
map = second;
else
{
panic ("munmap (%x-%x) but cannot split map at %x-%x",
start, end, map_start, map_end);
}
map_start = start;
}
if (map_end > end)
/* We need to split. */
{
debug (5, "(%x-%x): splitting %x-%x at offset %x",
start, end, map_start, map_end, end - map_start + 1);
struct map *second = map_split (map, end - map_start + 1);
if (! second)
{
panic ("munmap (%x-%x) but cannot split map at %x-%x",
start, end, map_start, map_end);
}
map_end = end;
}
if (((map->access & MAP_ACCESS_WRITE) && ! (access & PROT_WRITE))
|| ((map->access & MAP_ACCESS_READ) && ! (access & PROT_READ)))
/* We need to reduce the permission on all capabilities in
the area. We don't have to do this if we are increasing
access: faulting will handle that. */
{
map->access = access;
vg_addr_t addr;
for (addr = VG_ADDR (map_start, VG_ADDR_BITS - PAGESIZE_LOG2);
vg_addr_prefix (addr) < map_end;
addr = vg_addr_add (addr, 1))
{
/* This may fail if the page has not yet been faulted
in. That's okay: it will get the right
permissions. */
as_slot_lookup_use
(addr,
({
if (map->access == 0)
{
error_t err;
err = vg_cap_rubout (meta_data_activity,
VG_ADDR_VOID, addr);
assert (! err);
slot->type = vg_cap_void;
}
else
{
bool ret;
ret = vg_cap_copy_x (meta_data_activity,
VG_ADDR_VOID, slot, addr,
VG_ADDR_VOID, *slot, addr,
VG_CAP_COPY_WEAKEN,
VG_CAP_PROPERTIES_VOID);
assert (ret);
}
}));
}
}
else
map->access = access;
}
maps_lock_unlock ();
return 0;
}
|
