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/*
* Copyright (C) 2020 The Android Open Source Project
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#pragma once
#include <sys/auxv.h>
#include <sys/prctl.h>
// Note: Most PR_MTE_* constants come from the upstream kernel. This tag mask
// allows for the hardware to provision any nonzero tag. Zero tags are reserved
// for scudo to use for the chunk headers in order to prevent linear heap
// overflow/underflow.
#define PR_MTE_TAG_SET_NONZERO (0xfffeUL << PR_MTE_TAG_SHIFT)
inline bool mte_supported() {
#if defined(__aarch64__)
static bool supported = getauxval(AT_HWCAP2) & HWCAP2_MTE;
#else
static bool supported = false;
#endif
return supported;
}
#ifdef __aarch64__
class ScopedDisableMTE {
size_t prev_tco_;
public:
ScopedDisableMTE() {
if (mte_supported()) {
__asm__ __volatile__(".arch_extension mte; mrs %0, tco; msr tco, #1" : "=r"(prev_tco_));
}
}
~ScopedDisableMTE() {
if (mte_supported()) {
__asm__ __volatile__(".arch_extension mte; msr tco, %0" : : "r"(prev_tco_));
}
}
};
#else
struct ScopedDisableMTE {
// Silence unused variable warnings in non-aarch64 builds.
ScopedDisableMTE() {}
};
#endif
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