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