mirror of
https://github.com/RetroDECK/Duckstation.git
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198 lines
7.8 KiB
C++
198 lines
7.8 KiB
C++
// Copyright 2018, VIXL authors
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// All rights reserved.
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//
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// Redistribution and use in source and binary forms, with or without
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// modification, are permitted provided that the following conditions are met:
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//
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// * Redistributions of source code must retain the above copyright notice,
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// this list of conditions and the following disclaimer.
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// * Redistributions in binary form must reproduce the above copyright notice,
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// this list of conditions and the following disclaimer in the documentation
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// and/or other materials provided with the distribution.
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// * Neither the name of ARM Limited nor the names of its contributors may be
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// used to endorse or promote products derived from this software without
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// specific prior written permission.
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//
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// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS CONTRIBUTORS "AS IS" AND
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// ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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// WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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// DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE
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// FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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// DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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// SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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// CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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// OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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#ifdef VIXL_INCLUDE_SIMULATOR_AARCH64
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#include "simulator-aarch64.h"
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#include "utils-vixl.h"
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namespace vixl {
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namespace aarch64 {
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// Randomly generated example keys for simulating only.
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const Simulator::PACKey Simulator::kPACKeyIA = {0xc31718727de20f71,
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0xab9fd4e14b2fec51,
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0};
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const Simulator::PACKey Simulator::kPACKeyIB = {0xeebb163b474e04c8,
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0x5267ac6fc280fb7c,
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1};
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const Simulator::PACKey Simulator::kPACKeyDA = {0x5caef808deb8b1e2,
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0xd347cbc06b7b0f77,
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0};
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const Simulator::PACKey Simulator::kPACKeyDB = {0xe06aa1a949ba8cc7,
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0xcfde69e3db6d0432,
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1};
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// The general PAC key isn't intended to be used with AuthPAC so we ensure the
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// key number is invalid and asserts if used incorrectly.
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const Simulator::PACKey Simulator::kPACKeyGA = {0xfcd98a44d564b3d5,
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0x6c56df1904bf0ddc,
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-1};
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static uint64_t GetNibble(uint64_t in_data, int position) {
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return (in_data >> position) & 0xf;
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}
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static uint64_t ShuffleNibbles(uint64_t in_data) {
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static int in_positions[16] =
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{4, 36, 52, 40, 44, 0, 24, 12, 56, 60, 8, 32, 16, 28, 20, 48};
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uint64_t out_data = 0;
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for (int i = 0; i < 16; i++) {
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out_data |= GetNibble(in_data, in_positions[i]) << (4 * i);
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}
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return out_data;
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}
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static uint64_t SubstituteNibbles(uint64_t in_data) {
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// Randomly chosen substitutes.
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static uint64_t subs[16] =
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{4, 7, 3, 9, 10, 14, 0, 1, 15, 2, 8, 6, 12, 5, 11, 13};
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uint64_t out_data = 0;
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for (int i = 0; i < 16; i++) {
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int index = (in_data >> (4 * i)) & 0xf;
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out_data |= subs[index] << (4 * i);
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}
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return out_data;
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}
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// Rotate nibble to the left by the amount specified.
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static uint64_t RotNibble(uint64_t in_cell, int amount) {
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VIXL_ASSERT((amount >= 0) && (amount <= 3));
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in_cell &= 0xf;
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uint64_t temp = (in_cell << 4) | in_cell;
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return (temp >> (4 - amount)) & 0xf;
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}
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static uint64_t BigShuffle(uint64_t in_data) {
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uint64_t out_data = 0;
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for (int i = 0; i < 4; i++) {
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uint64_t n12 = GetNibble(in_data, 4 * (i + 12));
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uint64_t n8 = GetNibble(in_data, 4 * (i + 8));
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uint64_t n4 = GetNibble(in_data, 4 * (i + 4));
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uint64_t n0 = GetNibble(in_data, 4 * (i + 0));
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uint64_t t0 = RotNibble(n8, 2) ^ RotNibble(n4, 1) ^ RotNibble(n0, 1);
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uint64_t t1 = RotNibble(n12, 1) ^ RotNibble(n4, 2) ^ RotNibble(n0, 1);
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uint64_t t2 = RotNibble(n12, 2) ^ RotNibble(n8, 1) ^ RotNibble(n0, 1);
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uint64_t t3 = RotNibble(n12, 1) ^ RotNibble(n8, 1) ^ RotNibble(n4, 2);
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out_data |= t3 << (4 * (i + 0));
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out_data |= t2 << (4 * (i + 4));
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out_data |= t1 << (4 * (i + 8));
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out_data |= t0 << (4 * (i + 12));
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}
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return out_data;
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}
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// A simple, non-standard hash function invented for simulating. It mixes
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// reasonably well, however it is unlikely to be cryptographically secure and
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// may have a higher collision chance than other hashing algorithms.
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uint64_t Simulator::ComputePAC(uint64_t data, uint64_t context, PACKey key) {
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uint64_t working_value = data ^ key.high;
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working_value = BigShuffle(working_value);
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working_value = ShuffleNibbles(working_value);
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working_value ^= key.low;
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working_value = ShuffleNibbles(working_value);
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working_value = BigShuffle(working_value);
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working_value ^= context;
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working_value = SubstituteNibbles(working_value);
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working_value = BigShuffle(working_value);
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working_value = SubstituteNibbles(working_value);
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return working_value;
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}
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// The TTBR is selected by bit 63 or 55 depending on TBI for pointers without
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// codes, but is always 55 once a PAC code is added to a pointer. For this
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// reason, it must be calculated at the call site.
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uint64_t Simulator::CalculatePACMask(uint64_t ptr, PointerType type, int ttbr) {
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int bottom_pac_bit = GetBottomPACBit(ptr, ttbr);
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int top_pac_bit = GetTopPACBit(ptr, type);
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return ExtractUnsignedBitfield64(top_pac_bit,
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bottom_pac_bit,
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0xffffffffffffffff & ~kTTBRMask)
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<< bottom_pac_bit;
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}
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uint64_t Simulator::AuthPAC(uint64_t ptr,
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uint64_t context,
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PACKey key,
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PointerType type) {
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VIXL_ASSERT((key.number == 0) || (key.number == 1));
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uint64_t pac_mask = CalculatePACMask(ptr, type, (ptr >> 55) & 1);
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uint64_t original_ptr =
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((ptr & kTTBRMask) == 0) ? (ptr & ~pac_mask) : (ptr | pac_mask);
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uint64_t pac = ComputePAC(original_ptr, context, key);
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uint64_t error_code = 1 << key.number;
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if ((pac & pac_mask) == (ptr & pac_mask)) {
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return original_ptr;
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} else {
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int error_lsb = GetTopPACBit(ptr, type) - 2;
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uint64_t error_mask = UINT64_C(0x3) << error_lsb;
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return (original_ptr & ~error_mask) | (error_code << error_lsb);
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}
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}
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uint64_t Simulator::AddPAC(uint64_t ptr,
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uint64_t context,
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PACKey key,
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PointerType type) {
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int top_pac_bit = GetTopPACBit(ptr, type);
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// TODO: Properly handle the case where extension bits are bad and TBI is
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// turned off, and also test me.
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VIXL_ASSERT(HasTBI(ptr, type));
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int ttbr = (ptr >> 55) & 1;
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uint64_t pac_mask = CalculatePACMask(ptr, type, ttbr);
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uint64_t ext_ptr = (ttbr == 0) ? (ptr & ~pac_mask) : (ptr | pac_mask);
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uint64_t pac = ComputePAC(ext_ptr, context, key);
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// If the pointer isn't all zeroes or all ones in the PAC bitfield, corrupt
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// the resulting code.
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if (((ptr & (pac_mask | kTTBRMask)) != 0x0) &&
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((~ptr & (pac_mask | kTTBRMask)) != 0x0)) {
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pac ^= UINT64_C(1) << (top_pac_bit - 1);
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}
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uint64_t ttbr_shifted = static_cast<uint64_t>(ttbr) << 55;
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return (pac & pac_mask) | ttbr_shifted | (ptr & ~pac_mask);
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}
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uint64_t Simulator::StripPAC(uint64_t ptr, PointerType type) {
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uint64_t pac_mask = CalculatePACMask(ptr, type, (ptr >> 55) & 1);
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return ((ptr & kTTBRMask) == 0) ? (ptr & ~pac_mask) : (ptr | pac_mask);
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}
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} // namespace aarch64
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} // namespace vixl
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#endif // VIXL_INCLUDE_SIMULATOR_AARCH64
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