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flat assembler > OS Construction > 2MB pages in long mode and 0xB8000 address

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CandyMan



Joined: 04 Sep 2009
Posts: 226
Location: film "CandyMan" directed through Bernard Rose
2MB pages in long mode and 0xB8000 address
How to map 0xB8000..0xBFFFF at 68GB+16MB=(0x1101000000) ?
My code is:

Code:

MaxMem          dd      64              ;64GB
MemoryStart     dd      1024*1024       ;1M

        push    0
        pop     fs

        mov     eax,[MaxMem]
        shl     eax,12
        lea     ebx,[eax+512*8*(2+1)]

        mov     ebp,ebx
        push    ebx

        mov     eax,[MemoryStart]
        mov     ebx,eax

        lea     eax,[ebx+4*1024-1]      ;\ Align to 4*1024
        and     ax,not (4*1024-1)       ;/
        mov     [PML4],eax
        add     eax,4*1024
        mov     [PDP],eax
        add     eax,4*1024
        mov     [PDT],eax

        pxor    mm0,mm0
        pop     ecx
        shr     ecx,3
      @@:
        dec     ecx
        movq    [fs:ebx+ecx*8],mm0
        jnz     @B

        mov     eax,[PML4]
        mov     ebx,[PDP]
        mov     ecx,[PDT]
        or      bl,7
        or      cl,7
        mov     [fs:eax+8*000],ebx

        ;Fill page tables
        mov     eax,[PDP]
        xor     edx,edx
      .1:
        mov     [fs:eax+8*edx],ecx
        add     ecx,4*1024
        inc     edx
        cmp     edx,[MaxMem]
        jb      .1

        mov     eax,2*1024*1024
        movd    mm1,eax
        mov     eax,PT_AVL+PT_PS+PT_U+PT_W+PT_P ;Start from 1st 0..2MB-1
        movd    mm0,eax

        mov     ecx,[MaxMem]
        shl     ecx,9
        mov     eax,[PDT]
      .0:
        movq    [fs:eax],mm0
        paddq   mm0,mm1
        add     eax,8
        loop    .0

        mov     eax,[AddrLFB]
        or      eax,eax
        jz      @F
        or      eax,PT_AVL+PT_PS+PT_U+PT_W+PT_P
        movd    mm0,eax

        mov     edx,[PDT]
        add     edx,(68 shl 9)*8
        mov     ecx,8
      .2:
        movq    [fs:edx],mm0
        paddq   mm0,mm1
        add     edx,8
        loop    .2

        mov     eax,0xB8000+PT_AVL+PT_U+PT_W+PT_P
        movd    mm0,eax
        movq    [fs:edx],mm0
      @@:


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Post 02 Aug 2016, 10:39
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