ST486DX datasheet(26/34 Pages) STMICROELECTRONICS

26 / 34 page

ST486DX - SMM SOFTWARE CONSIDERATIONS

mov

al,cl

al,08h

;set MMAC bit in CCR1

mov

al,0c1h

out

23h,al

mov

eax,CR3

;get Page Directory Base Reg

and

eax,0fffff000h

mov

ebx,edx

;linear address

shr

ebx,22

;get 10 byte Directory Entry

;read Directory Table

mov

eax,dword ptr fs:[eax+ebx*4]

and

eax,0fffff000h

mov

ebx,edx

;linear address

shr

ebx,12

and

ebx,03ffh

;get 10 byte Page Table Entry

mov

eax,dword ptr fs:[eax+ebx*4]

and

eax,0fffff000h

mov

ebx,edx

;linear address

and

ebx,0fffh

;get 12 byte offset into page

;Get the physical address of the instruction before the

;Current IP.

Save in BL.

mov

bl,byte ptr fs:[eax+ebx]

mov

al,0c1h

;set MMAC back to normal

out

22h,al

mov

al,cl

out

23h,al

;MMAC = 0

jmp

got_inst

;If paging is not enabled then checking for the HLT

;instruction is easy since the linear address equals

;the physical address.

no_paging:

mov

al,0c1h

;set MMAC

out

22h,al

al,23h

mov

ah,al

mov

al,0c1h

out

22h,al

mov

al,ah

al,08h

out

23h,al

;get instruction interrupted by SMI

mov

bl,byte ptr fs:[edx]

mov

al,0c1h

;store it in BL

out

22h,al

ST486DX 数据表(PDF) 26 Page - STMicroelectronics

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ST486DX 数据表(PDF) 26 Page - STMicroelectronics

ST486DX 数据表(HTML) 26 Page - STMicroelectronics

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