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

51 lines
2.0 KiB
NASM

;=----------------------------------------------------------------------------=;
; GNU GPL OS/K ;
; ;
; Authors: spectral` ;
; NeoX ;
; ;
; Desc: Basic realmode CPU Detection ;
; (x86_64 architecture only) ;
;=----------------------------------------------------------------------------=;
[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