1 /* Copyright (c) (2021,2022) Apple Inc. All rights reserved.
2 *
3 * corecrypto is licensed under Apple Inc.’s Internal Use License Agreement (which
4 * is contained in the License.txt file distributed with corecrypto) and only to
5 * people who accept that license. IMPORTANT: Any license rights granted to you by
6 * Apple Inc. (if any) are limited to internal use within your organization only on
7 * devices and computers you own or control, for the sole purpose of verifying the
8 * security characteristics and correct functioning of the Apple Software. You may
9 * not, directly or indirectly, redistribute the Apple Software or any portions thereof.
10 *
11 * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
12 *
13 * This file contains Original Code and/or Modifications of Original Code
14 * as defined in and that are subject to the Apple Public Source License
15 * Version 2.0 (the 'License'). You may not use this file except in
16 * compliance with the License. The rights granted to you under the License
17 * may not be used to create, or enable the creation or redistribution of,
18 * unlawful or unlicensed copies of an Apple operating system, or to
19 * circumvent, violate, or enable the circumvention or violation of, any
20 * terms of an Apple operating system software license agreement.
21 *
22 * Please obtain a copy of the License at
23 * http://www.opensource.apple.com/apsl/ and read it before using this file.
24 *
25 * The Original Code and all software distributed under the License are
26 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
27 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
28 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
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30 * Please see the License for the specific language governing rights and
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34 */
35
36 #include "cc_internal.h"
37
38 #if CC_DIT_MAYBE_SUPPORTED
39
40 // Ignore "unreachable code" warnings when compiling against SDKs
41 // that don't support checking for DIT support at runtime.
42 #pragma clang diagnostic push
43 #pragma clang diagnostic ignored "-Wunreachable-code"
44
45 void
cc_disable_dit(volatile bool * dit_was_enabled)46 cc_disable_dit(volatile bool *dit_was_enabled)
47 {
48 if (!CC_HAS_DIT()) {
49 return;
50 }
51
52 #if CC_BUILT_FOR_TESTING
53 // DIT should be enabled.
54 cc_try_abort_if(!cc_is_dit_enabled(), "DIT not enabled");
55 #endif
56
57 // Disable DIT, if this was the frame that enabled it.
58 if (*dit_was_enabled) {
59 // Encoding of <msr dit, #0>.
60 __asm__ __volatile__ (".long 0xd503405f");
61 cc_assert(!cc_is_dit_enabled());
62 }
63 }
64
65 #pragma clang diagnostic pop
66
67 #endif // CC_DIT_MAYBE_SUPPORTED
68