1/*
2 * Copyright (c) 2014 Apple Inc. All rights reserved.
3 *
4 * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
5 *
6 * This file contains Original Code and/or Modifications of Original Code
7 * as defined in and that are subject to the Apple Public Source License
8 * Version 2.0 (the 'License'). You may not use this file except in
9 * compliance with the License. The rights granted to you under the License
10 * may not be used to create, or enable the creation or redistribution of,
11 * unlawful or unlicensed copies of an Apple operating system, or to
12 * circumvent, violate, or enable the circumvention or violation of, any
13 * terms of an Apple operating system software license agreement.
14 *
15 * Please obtain a copy of the License at
16 * http://www.opensource.apple.com/apsl/ and read it before using this file.
17 *
18 * The Original Code and all software distributed under the License are
19 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
20 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
21 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
22 * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
23 * Please see the License for the specific language governing rights and
24 * limitations under the License.
25 *
26 * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
27 */
28
29#include <mach/vm_param.h>
30
31/*
32 * This file is compiled and linked to be the last .o of the __const section
33 * of the __DATA segment (see MakeInc.kernel, lastkernelconstructor is placed
34 * in the __LAST segment.)
35 *
36 * This blank page allows us to safely map the const section RO while the rest
37 * of __DATA is RW. This is needed since ld has no way of specifying section size
38 * alignment and no straight forward way to specify section ordering.
39 */
40
41#if defined(__arm64__)
42/* PAGE_SIZE on ARM64 is an expression derived from a non-const global variable */
43#define PAD_SIZE PAGE_MAX_SIZE
44#else
45#define PAD_SIZE PAGE_SIZE
46#endif
47
48static const uint8_t __attribute__((section("__DATA,__const"))) data_const_padding[PAD_SIZE] = {[0 ... PAD_SIZE-1] = 0xFF};
49const vm_offset_t __attribute__((section("__DATA,__data"))) _lastkerneldataconst = (vm_offset_t)&data_const_padding[0];
50const vm_size_t __attribute__((section("__DATA,__data"))) _lastkerneldataconst_padsize = sizeof(data_const_padding);
51