emm386.asm

DOS 源代码 系列之 command 源码

;/*
; *                      Microsoft Confidential
; *                      Copyright (C) Microsoft Corporation 1988 - 1991
; *                      All Rights Reserved.
; */
;
;  EMM386.ASM
;
;     fIsPooled() - Returns version if pooling is in effect, else 0
;

.MODEL	SMALL

include rombios.inc

;
;emm defines
;
EMM_INT_VECT		EQU 	67h
DEVICE_OFFSET		EQU	10

EMM_POOLED_VER		EQU	42Dh   ; emm386 pooled version is 4.45

EMM_READ_FUNC		EQU	1
EMM_GET_VER		EQU	2
EMM_DEV_NAME    	EQU     "EMMXXXX0",0 ; Name for EMM driver IOCTL open.
EMM_DEV_NOEMS           EQU     '$'          ; M000: Replacement for first
                                             ;   char. of EMM_DEV_NAME when
                                             ;   "device=EMM386 NOEMS".

EMM_DEV_VCPI            EQU     "EMMQXXX0",0 ; M002: Name for EMM driver when
                                             ;   VCPI but not EMS support.

EMM386_SIG           	EQU     "MICROSOFT"  ; M001: EMM386 Signature.
                                             ; M001: Offset from device base.
EMM386_SIG_OFFSET       EQU     (0ah + EMM_DEV_NAME_LEN - 1 + 2)


; Structure of the data returned on the IOCTL call to the EMM driver

EMM_STRUC	struc

    EMM_Version_Maj	db	?   ; Internal revision number
    EMM_Version_Min	db	?

EMM_STRUC	ends

Version		EQU (-((SIZE EMM_STRUC) - EMM_Version_Maj))
Function	EQU (-(SIZE EMM_STRUC))

.DATA

DevName db 'EMMXXXX0'

DeviceName	db	EMM_DEV_NAME	; Name for EMM IOCTL opens.
EMM_DEV_NAME_LEN EQU    ($-DeviceName)  ; M001: Length of DeviceName string.

EMM386Sig    	db      EMM386_SIG	; M001: Signature for EMM386 device.
EMM386_SIG_LEN  EQU     ($-EMM386Sig) 	; M001: Signature length.

;M002
VCPIDevName	db	EMM_DEV_VCPI	; Name for EMM VCPI IOCTL opens.

_MaxMin  dw 2 dup (0)
public _MaxMin

.CODE

public _fIsPooled

_fIsPooled	proc	near
	push	ES
	push	SI
	push	DI
	pushf				; M001: Save flags due to CLD below.
	push	BP
	mov	BP,SP
	sub	SP,SIZE EMM_STRUC

;M000
        xor     ax, ax
	mov	[_MaxMin],   ax
	mov	[_MaxMin+2], ax      ; First, we initialize the buffer.

	mov	DX,OFFSET DeviceName	; DS:DX pointer to emm name
	mov	AX,3d02h		; Try to open the device
	int	21h
        jnc     GEV40                   ; Jump if device opens.

	mov	DeviceName,EMM_DEV_NOEMS ; DS:DX -> NOEMS emm name
	mov	AX,3d02h		; Try to open the device
	int	21h
        jnc     GEV40                   ; Jump if device opens.

;M002
	mov	DX,OFFSET VCPIDevName	; DS:DX pointer to VCPI emm name
	mov	AX,3d02h		; Try to open the device
	int	21h
        jc      GEV60                   ; Jump if device not found.

; M001: Validate "MICROSOFT" signature.

GEV40:  push    AX                      ; Save EMM device handle.
        mov     AX,(35h SHL 8) OR EMM_INT_VECT
        int     21h                     ; ES:BX -> EMM device handler.
                                        ; ES:0000 -> EMM device base.
        mov     DI,EMM386_SIG_OFFSET    ; ES:DI -> EMM Signature.
        mov     SI,OFFSET EMM386Sig	; DS:SI -> EMM386 Signature.
        mov     CX,EMM386_SIG_LEN       ; CX = Signature length.
        cld
        repz    cmpsb                   ; Signature match?
        jz      GEV80                  	;   Yes, jump.
                                        ;   No, fall thru and exit.

GEV60:	xor	AX,AX			; return code = 0.
	jmp	SHORT FunctExit         ; Go fix stack and exit.

GEV80:	pop	BX			; BX = device handle.
;M000

	mov	AX,4400h		; IOCTL get device information.
	int	21h
	jc	SHORT ErrorClose	; Carry indicates call unsuccesful

	test	DX,0080h		; Test if clock device.
	jz	SHORT ErrorClose	; if not, we can't steal memory.

	test	DX,4000h		; Are IOCTL's 02h and 03h supported
	jz	SHORT ErrorClose	; if not we cannot steal memory.

	push	DS
	mov	AX,SS
	mov	DS,AX
	mov	DX,BP			; DS:DX == SS:BP
	mov	CX,SIZE EMM_STRUC	; CX == size of the ctrl string
	sub	DX,CX			; DS:DX --> Start of data struct

	mov	BYTE PTR [BP].Function,EMM_GET_VER

	mov	AX,4402h		; Read control device string function
	int	21h
	pop	DS
	jc	SHORT ErrorClose	; Carry indicates call unsuccesful

	cmp	AX,CX			; If ax != cx we did not get the
	jne	SHORT ErrorClose	; number of bytes we requested !
	mov	AX,WORD PTR [BP].Version ; Have good version #
	xchg	AH,AL			; Put major ver. in AH & minor in AL

	cmp	AX,EMM_POOLED_VER	; if emm386 ver 4.45 continue
	jl	SHORT ErrorClose	; else return 0

        mov     cx, 4
	mov	dx, offset _MaxMin     ; offset of emm386 max allocated and min allocated buffer
	mov	byte ptr [_MaxMin], 3  ; set function code for IOCTL
        mov     ax, 4402h              ; read control data from char device
	int	21h		       ; get max-min allocated for emm386

	jmp	SHORT CloseHandle

ErrorClose:
	xor	AX,AX			; Invalid EMM386 version #

CloseHandle:
	push	AX
	mov	AX,3E00h		; Close device, handle in BX.
	int	21h			; Call DOS
	pop	AX

FunctExit:
	mov	SP,BP
	pop	BP
        popf                            ; M001
	pop	DI
	pop	SI
	pop	ES
	ret				; return to caller.

_fIsPooled	endp

end