1 /*
2 * Copyright (C) 2020 The Android Open Source Project
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * * Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * * Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in
12 * the documentation and/or other materials provided with the
13 * distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
16 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
17 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
18 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
19 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
21 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
22 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
23 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
24 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
25 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26 * SUCH DAMAGE.
27 */
28
29 #pragma once
30
31 #include <sys/auxv.h>
32 #include <sys/prctl.h>
33
34 // Note: Most PR_MTE_* constants come from the upstream kernel. This tag mask
35 // allows for the hardware to provision any nonzero tag. Zero tags are reserved
36 // for scudo to use for the chunk headers in order to prevent linear heap
37 // overflow/underflow.
38 #define PR_MTE_TAG_SET_NONZERO (0xfffeUL << PR_MTE_TAG_SHIFT)
39
mte_supported()40 inline bool mte_supported() {
41 #if defined(__aarch64__)
42 static bool supported = getauxval(AT_HWCAP2) & HWCAP2_MTE;
43 #else
44 static bool supported = false;
45 #endif
46 return supported;
47 }
48
49 #ifdef __aarch64__
50 class ScopedDisableMTE {
51 size_t prev_tco_;
52
53 public:
ScopedDisableMTE()54 ScopedDisableMTE() {
55 if (mte_supported()) {
56 __asm__ __volatile__(".arch_extension mte; mrs %0, tco; msr tco, #1" : "=r"(prev_tco_));
57 }
58 }
59
~ScopedDisableMTE()60 ~ScopedDisableMTE() {
61 if (mte_supported()) {
62 __asm__ __volatile__(".arch_extension mte; msr tco, %0" : : "r"(prev_tco_));
63 }
64 }
65 };
66 #else
67 struct ScopedDisableMTE {
68 // Silence unused variable warnings in non-aarch64 builds.
ScopedDisableMTEScopedDisableMTE69 ScopedDisableMTE() {}
70 };
71 #endif
72