_vflat.asm

BIOS emulator and interface to Realmode X86 Emulator Library Can emulate a PCI Graphic Controller V

cprocstart	InstallBankFunc

		ARG		codeLen:UINT, bankFunc:DPTR

		enter_c

		mov		esi,[bankFunc]		; Copy the code into buffer
		mov		edi,offset BankFuncBuf
		mov		ecx,[codeLen]
	rep movsb
		mov		[BYTE edi],0C3h		; Terminate the function with a near ret

		leave_c
		ret

cprocend

;----------------------------------------------------------------------------
; int InitPaging(void)
;----------------------------------------------------------------------------
; Initializes paging system. If paging is not enabled, builds a page table
; directory and page tables for physical memory
;
;	Exit:		0	- Successful
;				-1	- Couldn't initialize paging mechanism
;----------------------------------------------------------------------------
cprocstart	InitPaging

		push    ebx
		push	ecx
		push	edx
		push	esi
		push	edi

; Are we running under CauseWay?

		mov 	ax,0FFF9h
		int 	31h
		jc 		@@NotCauseway
		cmp 	ecx,"CAUS"
		jnz 	@@NotCauseway
		cmp 	edx,"EWAY"
		jnz 	@@NotCauseway

		mov 	[BOOL VF_haveCauseWay],1
		mov 	[CauseWayDIRLinear],esi
		mov 	[CauseWay1stLinear],edi

; Check for DPMI

		mov 	ax,0ff00h
		push 	es
		int 	31h
		pop 	es
		shr 	edi,2
		and 	edi,3
		cmp 	edi,2
		jz 		@@ErrExit				; Not supported under DPMI

		mov 	eax,[CauseWayDIRLinear]
		jmp 	@@CopyCR3

@@NotCauseway:
		mov     ax,cs
		test    ax,3                    ; Which ring are we running
		jnz     @@ErrExit               ; Needs zero ring to access
										; page tables (CR3)
		mov     eax,cr0                 ; Load CR0
		test    eax,80000000h           ; Is paging enabled?
		jz    	@@ErrExit				; No, we must have paging!

		mov     eax,cr3                 ; Load directory address
		and     eax,0FFFFF000h

@@CopyCR3:
		mov     [PDBR],eax              ; Save it
		mov     esi,eax
        mov     edi,offset pageDirectory
        mov     ecx,1024
        cld
		rep     movsd                   ; Copy the original page table directory
		cmp		[DWORD accessPageAddr],0; Check if we have allocated page
		jne		@@HaveRealMem			; table already (we cant free it)

		mov     eax,0100h               ; DPMI DOS allocate
		mov     ebx,8192/16
		int     31h                     ; Allocate 8192 bytes
		and     eax,0FFFFh
		shl     eax,4                   ; EAX points to newly allocated memory
		add     eax,4095
		and     eax,0FFFFF000h          ; Page align
		mov     [accessPageAddr],eax

@@HaveRealMem:
		mov		eax,[accessPageAddr]	; EAX -> page table in 1st Mb
		shr     eax,12
        and     eax,3FFh                ; Page table offset
        shl     eax,2
		cmp 	[BOOL VF_haveCauseWay],0
		jz 		@@NotCW0
		mov 	ebx,[CauseWay1stLinear]
		jmp 	@@Put1st

@@NotCW0:
		mov     ebx,[PDBR]
        mov     ebx,[ebx]
		and     ebx,0FFFFF000h          ; Page table for 1st megabyte

@@Put1st:
		add     eax,ebx
		mov     [accessPageTable],eax
		sub     eax,eax                 ; No error
		jmp     @@Exit

@@ErrExit:
		mov     eax,-1

@@Exit:	pop     edi
		pop     esi
		pop     edx
		pop     ecx
		pop     ebx
		ret

cprocend

;----------------------------------------------------------------------------
; void ClosePaging(void)
;----------------------------------------------------------------------------
; Closes the paging system
;----------------------------------------------------------------------------
cprocstart	ClosePaging

		push    eax
		push	ecx
		push	edx
		push	esi
		push	edi

		mov     eax,[accessPageAddr]
		call    AccessPage              ; Restore AccessPage mapping
		mov     edi,[PDBR]
		mov     esi,offset pageDirectory
		mov     ecx,1024
		cld
		rep     movsd                   ; Restore the original page table directory

@@Exit:	pop     edi
		pop     esi
		pop     edx
		pop     ecx
		pop     eax
		ret

cprocend

;----------------------------------------------------------------------------
; long AccessPage(long phys)
;----------------------------------------------------------------------------
; Maps a known page to given physical memory
;	Entry:		EAX	- Physical memory
;	Exit:		EAX	- Linear memory address of mapped phys mem
;----------------------------------------------------------------------------
cprocstatic		AccessPage

		push    edx
		mov     edx,[accessPageTable]
		or      eax,7
		mov     [edx],eax
		mov     eax,cr3
		mov     cr3,eax                 ; Update page table cache
		mov     eax,[accessPageAddr]
		pop     edx
		ret

cprocend

;----------------------------------------------------------------------------
; long GetPhysicalAddress(long linear)
;----------------------------------------------------------------------------
; Returns the physical address of linear address
;	Entry:		EAX	- Linear address to convert
;	Exit:		EAX	- Physical address
;----------------------------------------------------------------------------
cprocstatic		GetPhysicalAddress

		push    ebx
		push    edx
		mov     edx,eax
		shr     edx,22                  ; EDX is the directory offset
		mov     ebx,[PDBR]
		mov     edx,[edx*4+ebx]         ; Load page table address
		push    eax
		mov     eax,edx
		call    AccessPage              ; Access the page table
		mov     edx,eax
		pop     eax
		shr     eax,12
		and     eax,03FFh               ; EAX offset into page table
		mov     eax,[edx+eax*4]         ; Load physical address
		and     eax,0FFFFF000h
		pop     edx
		pop     ebx
		ret

cprocend

;----------------------------------------------------------------------------
; void CreatePageTable(long pageDEntry)
;----------------------------------------------------------------------------
; Creates a page table for specific address (4MB)
;		Entry:	EAX	- Page directory entry (top 10-bits of address)
;----------------------------------------------------------------------------
cprocstatic		CreatePageTable

		push    ebx
		push    ecx
		push    edx
		push    edi
		mov     ebx,eax                 ; Save address
        mov     eax,8192
		push	eax
		call    VF_malloc              ; Allocate page table directory
		add		esp,4
		add     eax,0FFFh
		and     eax,0FFFFF000h          ; Page align (4KB)
		mov     edi,eax                 ; Save page table linear address
		sub     eax,eax                 ; Fill with zero
		mov     ecx,1024
		cld
		rep     stosd                   ; Clear page table
		sub     edi,4096
		mov     eax,edi
		call    GetPhysicalAddress
		mov     edx,[PDBR]
		or      eax,7                   ; Present/write/user bit
		mov     [edx+ebx*4],eax         ; Save physical address into page directory
		mov     eax,cr3
		mov     cr3,eax                 ; Update page table cache
		pop     edi
		pop     edx
		pop     ecx
		pop     ebx
		ret

cprocend

;----------------------------------------------------------------------------
; void MapPhysical2Linear(ulong pAddr, ulong lAddr, int pages, int flags);
;----------------------------------------------------------------------------
; Maps physical memory into linear memory
;	Entry:		pAddr	- Physical address
;				lAddr	- Linear address
;				pages	- Number of 4K pages to map
;				flags	- Page flags
;							bit 0   =       present
;							bit 1   =       Read(0)/Write(1)
;----------------------------------------------------------------------------
cprocstart	MapPhysical2Linear

		ARG		pAddr:ULONG, lAddr:ULONG, pages:UINT, pflags:UINT

		enter_c

		and     [ULONG pAddr],0FFFFF000h; Page boundary
		and     [ULONG lAddr],0FFFFF000h; Page boundary
		mov		ecx,[pflags]
		and     ecx,11b                 ; Just two bits
        or      ecx,100b                ; Supervisor bit
		mov     [pflags],ecx

		mov		edx,[lAddr]
		shr     edx,22                  ; EDX = Directory
        mov     esi,[PDBR]
		mov     edi,[pages]             ; EDI page count
		mov     ebx,[lAddr]

@@CreateLoop:
		mov     ecx,[esi+edx*4]         ; Load page table address
		test    ecx,1                   ; Is it present?
		jnz     @@TableOK
		mov     eax,edx
		call    CreatePageTable         ; Create a page table
@@TableOK:
		mov     eax,ebx
		shr     eax,12
		and     eax,3FFh
		sub     eax,1024
		neg     eax                     ; EAX = page count in this table
		inc     edx                     ; Next table
		mov     ebx,0                   ; Next time we'll map 1K pages
		sub     edi,eax                 ; Subtract mapped pages from page count
		jns     @@CreateLoop            ; Create more tables if necessary

		mov     ecx,[pages]             ; ECX = Page count
		mov     esi,[lAddr]
		shr     esi,12                  ; Offset part isn't needed
		mov     edi,[pAddr]
@@MappingLoop:
        mov     eax,esi
        shr     eax,10                  ; EAX = offset to page directory
        mov     ebx,[PDBR]
		mov     eax,[eax*4+ebx]         ; EAX = page table address
		call    AccessPage
		mov     ebx,esi
		and     ebx,3FFh                ; EBX = offset to page table
		mov     edx,edi
		add     edi,4096                ; Next physical address
		inc     esi                     ; Next linear page
		or      edx,[pflags]            ; Update flags...
		mov     [eax+ebx*4],edx         ; Store page table entry
		loop    @@MappingLoop
		mov     eax,cr3
		mov     cr3,eax                 ; Update page table cache

		leave_c
		ret

cprocend

endcodeseg  _vflat

endif

		END                     ; End of module