Liren Large Software Subsidy 7

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Assembly Source File | 1992-06-10 | 15.4 KB | 493 lines

;[]-----------------------------------------------------------------[] ;| EXEC.ASM -- Execute a program with Overlay | ;[]-----------------------------------------------------------------[] ; ; C/C++ Run Time Library - Version 5.0 ; ; Copyright (c) 1987, 1992 by Borland International ; All Rights Reserved. ; INCLUDE RULES.ASI ; Segments Definitions Header@ ; External References extrn __cexit:DIST extrn __IOERROR:near extrn __envseg:word ExtSym@ DGROUP@, WORD, __PASCAL__ ExtSym@ _psp, WORD, __CDECL__ ExtSym@ _version, WORD, __CDECL__ ;* Miscellaneous equates */ ExeSignature equ 05A4Dh ;/* Data for the Loader */ LdDesc STRUC LdErrorMsg db 'Exec failure.',00Dh,00Ah LdStack db 80H dup(?) ;Loader stack LdPSP dw ? ;PSP address LdPathName db 80 dup(?) ;File to be loaded LdAX dw ? ;Parse file name results LdExeSignature dw ? ;EXE header buffer LdLength dw ? LdNbPages dw ? LdNbItems dw ? LdHdrSize dw ? LdMin dw ? LdMax dw ? LdSS dw ? LdSP dw ? LdCheckSum dw ? LdIP dw ? LdCS dw ? LdLoadAddr dw ? ;Load Overlay interface block LdRelocFactor dw ? ;Relocation factor to be used LdDesc ENDS SUBTTL Loader program PAGE ;/* */ ;/*------------------------------------------------------*/ ;/* */ ;/* Loader Program */ ;/* -------------- */ ;/* */ ;/*------------------------------------------------------*/ ;/* */ CSeg@ LoaderDatas db size LdDesc dup (0) _Loader PROC NEAR ;CX = EnvSeg, DX = End of Memory ;/* Setup segment registers */ xor di, di mov ax, cs mov ds, ax mov es, ax cli mov ss, ax lea sp, [di+LdPSP] sti ;/* Load The Program */ push cx push dx mov ax, 4B03h lea bx, [di+LdLoadAddr] lea dx, [di+LdPathName] int 21h pop dx pop cx jb LoadError xor di, di cli mov ss, [di+LdSS] mov sp, [di+LdSP] sti mov bp, sp xor ax, ax push ax ;Return to MSDOS for .COM mov ax, [di+LdPSP] mov ds, ax mov es, ax mov es:[2h], dx ;Set End of Program into PSP mov es:[2ch], cx ;Set EnvSeg into PSP mov ax, cs:[di+LdAX] ;AX = validity of FCBs jmp dword ptr cs:[LdIP] ;/* Fatal Error if unable to load the program */ LoadError label near mov ah, 040h mov bx, 2 mov cx, LdStack - LdErrorMsg xor dx, dx int 21h ;Error message on stderr mov ax, 4C02h int 21h ;exit(2) _Loader ENDP LoaderSize equ ($ - LoaderDatas + 15) / 16 wLoaderSize equ LoaderSize * 8 LoaderVector dd _Loader - LoaderDatas SUBTTL Loader program PAGE ;/* */ ;/*------------------------------------------------------*/ ;/* */ ;/* int _exec(pathP, cmdP, envP); */ ;/* char *pathP; */ ;/* char *cmdP; */ ;/* char *envP; */ ;/* */ ;/*------------------------------------------------------*/ ;/* */ pathP equ 4 IF LDATA cmdP equ pathP + 4 envP equ cmdP + 4 ELSE cmdP equ pathP + 2 envP equ cmdP + 2 ENDIF FileHandle equ 2 MemSize equ FileHandle + 2 EnvSize equ MemSize + 2 EnvAddr equ EnvSize + 4 OldEnv equ EnvAddr + 2 OldEnvSave dw ? UseOldEnv db 1 ;flag, defaults to true public __exec __exec proc near push bp mov bp, sp sub sp, OldEnv cld push si push ds push di push es IFDEF __HUGE__ mov ds, cs:DGROUP@@ ; Get DS if we're huge ENDIF mov ax,__envseg ;save old environment mov cs:OldEnvSave,ax ;/* Open the file to be loaded */ mov ax, 3d00h pushDS_ LDS_ dx, [bp+pathP] int 21h popDS_ mov [bp-FileHandle], ax jnb CopyCmdLine jmp ExecExit ;/* Copy the command line into the PSP */ CopyCmdLine label near IFDEF __HUGE__ mov ax, seg _psp@ mov ds, ax ENDIF mov es, _psp@ mov LoaderDatas.LdPSP, es mov ax, es:[2ch] mov [bp-OldEnv], ax mov di, 080h pushDS_ LDS_ si, [bp+cmdP] lodsb mov dx, si ;Save cmdP for parse stosb xor cx, cx mov cl, al inc cx rep movsb ;/* Parse the command line for FCBs */ mov ax, 2901h mov si, dx mov di, 05ch int 21h ;Build FCB 1 in PSP mov byte ptr LoaderDatas.LdAX, al FindWhite label near mov al,[si] cmp al,20h ; Space je NextFCB cmp al,09h ; Tab je NextFCB cmp al,0dh ; Carriage Return je NextFCB inc si jmp FindWhite NextFCB label near mov ax, 2901h mov di, 06ch int 21h ;Build FCB 2 in PSP mov byte ptr LoaderDatas.LdAX+1, al popDS_ ;/* Get the maximum memory block size */ mov ah, 4Ah mov bx, -1 int 21h cmp byte ptr _version@, 3 jnb GetMaxMem sub bx, 280h GetMaxMem label near mov [bp-MemSize], bx ;/* Compute environment size */ IF LDATA mov ax, [bp+envP] mov dx, [bp+envP+2] ELSE mov ax, [bp+envP] or ax, ax mov dx, ds jnz DoWeHaveAnEnv cwd ENDIF DoWeHaveAnEnv label near mov bx, ax or bx, dx jnz WeHaveAnEnv xor ax, ax mov di, ax jmp short SetEnvSize WeHaveAnEnv label near mov es, dx mov di, ax push di mov cx, -1 xor ax, ax GetEnvSize label near repnz scasb cmp es:[di], al jne GetEnvSize dec cx add di, 3 repnz scasb ;/* EnvSize += PathSize */ dec cx mov ax, cx neg ax pop di SetEnvSize label near mov [bp-EnvAddr], di mov [bp-EnvAddr+2], es add ax, 15 mov cx, 4 shr ax, cl mov [bp-EnvSize], ax mov si,__envseg ;get the arena header for the environ dec si mov es,si cmp ax,word ptr es:[03] ;can we use the orig environ? jbe SavePath dec cs:UseOldEnv ;set to false inc ax sub [bp-MemSize], ax ;Reserve space for Env ;/* Save the pathname of the file to be loaded */ SavePath label near LDS_ si, [bp+pathP] push cs pop es lea di, LoaderDatas.LdPathName CopyPathName label near lodsb stosb or al, al jnz CopyPathName ;/* Process the file according to its type */ mov bx, [bp-FileHandle] mov ax, [si-5] or ah, ' ' push cs pop ds mov di, offset LoaderDatas cmp ax, 'c.' jne EXEFile jmp COMFile ;/* Here comes all Exec Error */ ExecError label near push ax mov ah, 3eh mov bx, [bp-FileHandle] int 21h pop ax jmp ExecExit ;/* This file must be an .EXE file */ EXEFile label near mov ah, 3fh mov cx, LdLoadAddr - LdExeSignature lea dx, [di+LdExeSignature] int 21h jb ExecError cmp [di+LdExeSignature], ExeSignature mov ax, 11 jne ExecError mov ax, [di+LdNbPages] xor dx, dx mov dl, ah mov ah, al xor al, al shl ax, 1 rcl dx, 1 ;DX:AX = NbPages * 512 add ax, [di+LdLength] adc dx, 0 mov cx, 4 EXECompute label near shr dx, 1 rcr ax, 1 loop EXECompute inc ax sub ax, [di+LdHdrSize] add ax, [di+LdMin] xchg bx, ax mov ax, [di+LdPSP] add ax, 16 add [di+LdCS], ax add [di+LdSS], ax xchg ax, bx jmp short IsItEnough ;/* The file to be loaded is .COM file */ COMFile label near mov ax, 4202h xor cx, cx xor dx, dx int 21h mov cx, 4 COMCompute label near shr dx, 1 rcr ax, 1 loop COMCompute inc ax xchg bx, ax mov ax, [di+LdPSP] mov [di+LdCS], ax mov [di+LdIP], 0100h mov [di+LdSS], ax add ax, 16 xchg ax, bx IsItEnough label near ;AX = Pgm requirements, BX = Pgm Load Addr mov [di+LdLoadAddr], bx mov [di+LdRelocFactor], bx add ax, LoaderSize cmp ax, [bp-MemSize] mov ax, 8 jna $+5 jmp ExecError ;/* Close the file before load it */ mov ah, 3eh mov bx, [bp-FileHandle] int 21h ;/* Takes all the memory above the current program */ mov es, [di+LdPSP] mov ah, 4ah mov bx, [bp-MemSize] int 21h jnb $+5 jmp ExecError ;/* Move the Loader before loading the overlay */ add bx, [di+LdPSP] mov dx, bx ;Save end of memory sub bx, LoaderSize+1 mov word ptr LoaderVector+2, bx mov es, bx mov cx, wLoaderSize mov si, offset LoaderDatas xor di, di rep movsw ;/* Copy the environment */ mov es, [bp-OldEnv] mov cx, [bp-EnvSize] cmp cs:UseOldEnv,0 jne ReUseEnv mov ah, 48h mov bx, cx int 21h jb ExecExit jmp short CopyEnv ReUseEnv: mov ax, cs:OldEnvSave CopyEnv: mov es, ax xor di, di lds si, [bp-EnvAddr] add cx, cx add cx, cx add cx, cx rep movsw push es ;/* Call exit procedures. Note: do not close file handles */ ;/* Once we do this we can't go back! */ push dx push ds mov ds, cs:DGROUP@@ ; Get DS call __cexit pop ds pop dx ;/* Free the old environment space */ cmp cs:UseOldEnv,0 jne ReadyToOverlay mov es, cs:OldEnvSave mov ah, 49h int 21h ;/* Jump to Loader and overlay the current program */ ReadyToOverlay label near pop cx jmp LoaderVector ;/* All error conditions set _doserrno and errno */ ExecExit label near pop es pop di pop ds pop si push ax call __IOERROR mov sp, bp pop bp ret endp CSegEnd@ END