2019-03-06 20:05:18 +01:00
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;=----------------------------------------------------------------------------=;
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; GNU GPL OS/K ;
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; ;
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; Desc: Basic realmode CPU Detection ;
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; (x86_64 architecture only) ;
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; ;
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; ;
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; Copyright © 2018-2019 The OS/K Team ;
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; ;
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; This file is part of OS/K. ;
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; ;
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; OS/K is free software: you can redistribute it and/or modify ;
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; it under the terms of the GNU General Public License as published by ;
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; the Free Software Foundation, either version 3 of the License, or ;
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; (at your option) any later version. ;
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; ;
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; OS/K is distributed in the hope that it will be useful, ;
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; but WITHOUT ANY WARRANTY; without even the implied warranty of ;
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; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the ;
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; GNU General Public License for 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 OS/K. If not, see <https://www.gnu.org/licenses/>. ;
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;=----------------------------------------------------------------------------=;
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[BITS 32]
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; ---------------------------------------------------------------------------- ;
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; Checks if the CPU is compatible with 64-bits operating systems ;
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; If the 21th bit of the eax register is set, then CPUID is supported ;
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; We then test CPUID's result to see if long mode is supported ;
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; ---------------------------------------------------------------------------- ;
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Is64Bits:
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;; test if extended processor info in available
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mov eax, 0x80000000 ; implicit argument for cpuid
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cpuid ; get highest supported argument
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cmp eax, 0x80000001 ; it needs to be at least 0x80000001
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jb .no_64 ; if it's less, the CPU is too old for long mode
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;; use extended info to test if long mode is available
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mov eax, 0x80000001 ; argument for extended processor info
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cpuid ; returns various feature bits in ecx and edx
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test edx, 1 << 29 ; test if the LM-bit is set in the D-register
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jz .no_64 ; If it's not set, there is no long mode
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ret
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.no_64:
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2019-03-06 20:05:18 +01:00
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mov ax, "01" ; ERROR 01 : 64bits unsupported
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2019-03-06 20:05:18 +01:00
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jmp Error
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; ---------------------------------------------------------------------------- ;
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; Check if CPUID is supported by flip the bit 21 (ID bit) in the FLAGS ;
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; register. If we can flip, CPUID is available. ;
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; ---------------------------------------------------------------------------- ;
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Check_cpuid:
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pushfd ; Copy FLAGS in to EAX via stack
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pop eax
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mov ecx, eax ; Copy to ECX as well for comparing later on
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xor eax, 1 << 21 ; Flip the ID bit
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push eax ; Copy EAX to FLAGS via the stack
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popfd
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pushfd ; Copy FLAGS back to EAX (with the flipped bit if CPUID is supported)
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pop eax
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push ecx ; flipping the flipped ID bit back if it was ever flipped like flipper
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popfd
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cmp eax, ecx ; VERITY MOMENT
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je .no_cpuid
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ret
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.no_cpuid:
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2019-03-06 20:05:18 +01:00
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mov ax, "02" ; ERROR 02 : CPUID UNSUPPORTED
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2019-03-06 20:05:18 +01:00
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jmp Error
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