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os-k/boot/loader/cpu/cpuid.asm

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;=----------------------------------------------------------------------------=;
; GNU GPL OS/K ;
; ;
; Desc: Basic realmode CPU Detection ;
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; (x86_64 architecture only) ;
; ;
; ;
; Copyright © 2018-2019 The OS/K Team ;
; ;
; This file is part of OS/K. ;
; ;
; OS/K is free software: you can redistribute it and/or modify ;
; it under the terms of the GNU General Public License as published by ;
; the Free Software Foundation, either version 3 of the License, or ;
; (at your option) any later version. ;
; ;
; OS/K is distributed in the hope that 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 OS/K. If not, see <https://www.gnu.org/licenses/>. ;
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;=----------------------------------------------------------------------------=;
[BITS 16]
;; GLOBAL DATA
NoLongMode db 0x0A, 0x0D, "ERROR : Your computer is not designed for x64 OS", 0
;; TEXT
Is64bits:
;-----------------------------------------------------------------------;
; Checks if the CPU is compatible with 64-bits operating systems ;
; If the 21th bit of the eax register is set, then CPUID is supported ;
; We then test CPUID's result to see if long mode is supported ;
;-----------------------------------------------------------------------;
pushfd ; recovering the flags in eax
pop eax
mov ecx, eax
xor eax, 0x200000
push eax
popfd
pushfd
pop eax
xor eax, ecx
shr eax, 21
and eax, 1 ; magical spell of murta
push ecx
popfd
test eax, eax
jz .NonCompat ; if (CPUID non supporté) goto NonCompat
mov eax, 0x80000000
cpuid
cmp eax, 0x80000001
jb .NonCompat ; if (eax <= 0x80000001) goto NonCompat
mov eax, 0x80000001
cpuid
test edx, 1 << 29
jz .NonCompat ; if (edx != 1 << 29) goto NonCompat
ret ; back to mbr.s
.NonCompat:
stc
ret