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51 lines
2.0 KiB
NASM
51 lines
2.0 KiB
NASM
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;=----------------------------------------------------------------------------=;
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; GNU GPL OS/K ;
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; ;
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; Authors: spectral` ;
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; NeoX ;
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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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[BITS 16]
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;; GLOBAL DATA
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NoLongMode db 0x0A, 0x0D, "ERROR : Your computer is not designed for x64 OS", 0
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;; TEXT
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Is64bits:
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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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pushfd ; recovering the flags in eax
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pop eax
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mov ecx, eax
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xor eax, 0x200000
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push eax
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popfd
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pushfd
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pop eax
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xor eax, ecx
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shr eax, 21
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and eax, 1 ; magical spell of murta
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push ecx
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popfd
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test eax, eax
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jz .NonCompat ; if (CPUID non supporté) goto NonCompat
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mov eax, 0x80000000
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cpuid
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cmp eax, 0x80000001
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jb .NonCompat ; if (eax <= 0x80000001) goto NonCompat
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mov eax, 0x80000001
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cpuid
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test edx, 1 << 29
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jz .NonCompat ; if (edx != 1 << 29) goto NonCompat
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ret ; back to mbr.s
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.NonCompat:
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stc
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ret
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