mirror of
https://github.com/Atmosphere-NX/Atmosphere.git
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58 lines
2 KiB
C++
58 lines
2 KiB
C++
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/*
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* Copyright (c) 2018-2020 Atmosphère-NX
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms and conditions of the GNU General Public License,
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* version 2, as published by the Free Software Foundation.
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*
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* This program is distributed in the hope it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
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* more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include <vapours.hpp>
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namespace ams::crypto {
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bool IsSameBytes(const void *lhs, const void *rhs, size_t size) {
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bool result;
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u8 xor_acc, ltmp, rtmp;
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size_t index;
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__asm__ __volatile__(
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/* Clear registers and prepare for comparison. */
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" movs %[xor_acc], #0\n"
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" movs %[index], #0\n"
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" b 1f\n"
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/* Compare one byte in constant time. */
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"0:\n"
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" ldrb %[ltmp], [%[lhs]]\n"
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" ldrb %[rtmp], [%[rhs]]\n"
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" adds %[lhs], #1\n"
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" adds %[rhs], #1\n"
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" eors %[ltmp], %[ltmp], %[rtmp]\n"
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" orrs %[xor_acc], %[xor_acc], %[ltmp]\n"
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" adds %[index], #1\n"
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/* Check if there is still data to compare. */
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"1:\n"
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" cmp %[index], %[size]\n"
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" bcc 0b\n"
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/* We're done, set result. */
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" cmp %[xor_acc], #0\n"
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" moveq %[result], #1\n"
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" movne %[result], #0\n"
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: [result]"=r"(result), [lhs]"+r"(lhs), [rhs]"+r"(rhs), [xor_acc]"=&r"(xor_acc), [index]"=&r"(index), [ltmp]"=&r"(ltmp), [rtmp]"=&r"(rtmp)
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: [size]"r"(size)
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: "cc"
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);
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return result;
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}
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}
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