Lecture (06) x86 programming 5

Transcription

1 Lecture (06) x86 programming 5 By: Dr. Ahmed ElShafee 1 TOC Format of DOS programs Format of the.com programs Addressing Modes 1> Immediate Addressing Mode 2> Register Addressing Mode 3> Direct Addressing Mode 4> Register Indirect Addressing Mode 2

2 Format of DOS programs All programs must have a code and a stack. Code is the part of the program that contains the instructions of the program. Stack is an area in the RAM used by the system to store return addresses, and by the programmer to store temporarily data. It is a Last In First Out (LIFO) buffer. Programs can also have a data area, where all data (variables) is stored. There are two basic types of programs: Commands (.COM). The data and the stack of the program are part of the Code segment. The stack is always located at the end of the segment. The first 256 bytes of the segment are reserved. 3 Executable (.EXE). The code and stack and data of the program are located in different segments. Format of the.com programs.model SMALL CSEG SEGMENT PARA 'CODE ;Start a Code segment ASSUME CS:CSEG, DS:CSEG, SS:CSEG ORG 100H ;Reserve first 256 locations START: JMP MAIN ;Skip data area {Place the data of the program here} MAIN PROC NEAR ;Beginning of main procedure {Place the code of the program here} RET ;Get return DOS address MAIN ENDP ;End of main procedure CSEG ENDS ;End of the segment END START ;End of the program 4

3 Format of the.com programs.model SMALL.CODE ORG 100H ;Reserve first 256 locations START: JMP MAIN ;Skip data area {Place the data of the program here} MAIN PROC NEAR ;Beginning of main procedure {Place the code of the program here} RET ;Get return DOS address MAIN ENDP ;End of main procedure END START ;End of the program 5 Example 01.01; hello world; masm CSEG SEGMENT PARA CODE ;Start a Code segment ASSUME CS:CSEG, DS:CSEG, SS:CSEG ORG 100H ;Reserve first 256 locations START: JMP MAIN ;Skip data area MSG DB "Hello World 01",'$ MAIN PROC NEAR ;Beginning of main procedure LEA DX,MSG MOV AH,9 INT 21H INT 20H RET MAIN ENDP ;End of main procedure CSEG ENDS ;End of the segment END START ;End of the program 6

4 Example 01; hello world; masm.model SMALL.CODE ORG 100H ;Reserve first 256 locations START: JMP MAIN ;Skip data area MSG DB "Hello World 01",'$ MAIN PROC NEAR ;Beginning of main procedure LEA DX,MSG MOV AH,9 INT 21H INT 20H RET MAIN ENDP ;End of main procedure END START ;End of the program 7 8

5 Compiling and linking Masm 01.asm ML AT 01.obj 01.com 9 10

6 Addressing Modes Addressing mode refers to the way the data needed by an instruction is specified. 11 1> Immediate Addressing Mode The data needed is specified as a number in the machine code of a program. The data is specified by the programmer: as a numeric operand in the instruction, e.g. MOV AL,87H ;AL 87H MOV CX,34A6H ;CX 34A6H MOV BL,8C2H ;Invalid (Data Mismatch) or as a label. The actual value is determined by the assembler. e.g. MOV BX,OFFSET VAL3 ;BX Address of VAL3 MOV AH,CON1 ;AH CON1 12

7 Example 02 org 100h jmp start VAL1 EQU 39H VAL2 DB 37 start: nop MOV BX,OFFSET VAL2 MOV AH,VAL1 END start 13 14

8 Example 03 ORG 100H STRT: JMP MAIN CON1 EQU 6CH CON2 EQU 245AH DAT1 DB 2FH,48H DAT2 DB 4 DUP (0) DAT3 DW 37AH MAIN PROC NEAR MOV SI,2310H MOV BX,OFFSET DAT1 MOV AL,CON1 MOV CX,CON2 MOV AX,283CH MOV AX,OFFSET DAT3 ENDP MAIN 15 END start ORG 100H Label Address Data STRT: JMP MAIN CON1 EQU 6CH CON2 EQU 245AH DAT1 DB 2FH,48H DAT2 DB 4 DUP (0) DAT3 DW 37AH MAIN PROC NEAR MOV SI,2310H MOV BX,OFFSET DAT1 MOV AL,CON1 MOV CX,CON2 MOV AX,283CH MOV AX,OFFSET DAT3 ENDP MAIN 16 END start AX BX CX AH AL BH BL CH CL SI

9 ORG 100H Label Address Data STRT: JMP MAIN start CODE CON1 EQU 6CH DAT F48 CON2 EQU 245AH DAT DAT1 DB 2FH,48H DAT A03 DAT2 DB 4 DUP (0) DAT3 DW 37AH AX BX CX MAIN PROC NEAR AH AL BH BL CH CL SI MOV SI,2310H NC NC NC NC NC NC 2310 MOV BX,OFFSET DAT1 NC NC NC NC NC MOV AL,CON1 6C MOV CX,CON2 24 5A MOV AX,283CH 28 3C MOV AX,OFFSET DAT ENDP MAIN 17 END start 18

10 2> Register Addressing Mode Both of the operands are the contents of registers. e.g. MOV AL,BH ;AL BH MOV BX,CX ;BX CX MOV AX,DL ;Invalid (Data Mismatch) 19 Example 04 ORG 100H STRT: JMP MAIN DATA1 DW 3620H DATA2 DW 0EEA5H DATA3 DW 9089H DATA4 DW 73F6H DATA5 DW 2006H MAIN PROC NEAR MOV AX,DATA1 MOV BX,DATA2 MOV CX,DATA3 MOV DX,DATA4 MOV SI,DATA5 MOV BX,CX MOV AL,DH MOV CX,AX MOV AH,AL MOV SI,DX ENDP MAIN END start 20

11 AX BX CX DX AH AL BH BL CH CL DH DL SI MAIN PROC NEAR EE A F MOV BX,CX MOV AL,DH MOV CX,AX MOV AH,AL MOV SI,DX 21 DATA1 DW 3620H DATA2 DW 0EEA5H DATA3 DW 9089H DATA4 DW 73F6H DATA5 DW 2006H AX BX CX DX AH AL BH BL CH CL DH DL SI MAIN PROC NEAR EE A F MOV BX,CX MOV AL,DH MOV CX,AX MOV AH,AL 73 MOV SI,DX 73F6 22

12 23 3> Direct Addressing Mode One of the operands is the contents of the memory location that is specified directly in the instruction. e.g. MOV AL,[1008H] ;AL [1008H] MOV BX,VALUE ;BX [VALUE] 24

13 Example 05 ORG 100H STRT: JMP MAIN DB? FRST DB 0C1H VAL1 DW 8756H ARR1 DB 9FH,0A6H,75H,8CH MAIN PROC NEAR MOV AL,[0104H] MOV BX,[0108H] MOV CH,FRST MOV DX,VAL1 MOV AH,ARR1 MOV CL,ARR1+3 ENDP MAIN END start 25 ORG 100H Label Address Data STRT: JMP MAIN FRST 0103 DB? VAL FRST DB 0C1H 0105 VAL1 DW 8756H ARR ARR1 DB 9FH,0A6H,75H,8CH

14 ORG 100H Label Address Data STRT: JMP MAIN FRST 0103 C1 DB? VAL FRST DB 0C1H VAL1 DW 8756H ARR F ARR1 DB 9FH,0A6H,75H,8CH 0107 A C 27 Label Address Data FRST 0103 C1 VAL ARR F 0107 A C AX BX CX DX MAIN PROC NEAR AH AL BH BL CH CL CH CL MOV AL,[0104H] MOV BX,[0108H] MOV CH,FRST MOV DX,VAL1 MOV AH,ARR1 MOV CL,ARR SI

15 Label Address Data FRST 0103 C1 VAL ARR F 0107 A C AX BX CX DX MAIN PROC NEAR AH AL BH BL CH CL CH CL MOV AL,[0104H] 56 MOV BX,[0108H] 8C 75 MOV CH,FRST C1 MOV DX,VAL MOV AH,ARR1 9F MOV CL,ARR1+3 8C 29 SI 30

16 4> Register Indirect Addressing Mode One of the operands is the contents of the memory location that is specified by a register, or a combination of registers and an offset, in the instruction. Index: Use of SI or DI to specify a memory location. e.g. MOV AL,[SI] ;AL [SI] - Base: Use of BX or BP to specify a memory location. e.g. MOV AH,[BP] ;AL [BP] - Base Relative: Use of BX or BP in combination with an offset to specify a memory location. e.g. MOV AL,[BX+ 2] ;AL [BX + 2] - Base Relative plus Index: Use of BX or BP in combination with an index register (SI or DI) and an offset to specify a memory location. e.g. MOV AL,[BX+SI+8] ;AL [BX+SI+8] MOV BX,ARR[BX+DI] ;BX ARR[BX+DI] 31 Example 06 ORG 100H STRT: JMP MAIN DAT1 DB 2FH,48H DAT2 DB 12H,10H,18H DAT3 DW 7A5H DAT4 DW 37H DAT5 DB 10H MAIN PROC NEAR MOV AX,7745H MOV BX,0104H MOV DI,0001 MOV SI,0002 MOV AL,[BX] MOV AH,DAT2[SI] MOV AL,DAT1[DI] MOV AL,[BX+SI] MOV AH,[BX+DI+3] ENDP MAIN END start 32

17 ORG 100H Label Address Data STRT: JMP MAIN 0100 DAT1 DB 2FH,48H 0101 DAT2 DB 12H,10H,18H 0102 DAT3 DW 7A5H 0103 DAT4 DW 37H 0104 DAT5 DB 10H A 010B 33 ORG 100H Label Address Data STRT: JMP MAIN START 0100 DAT1 DB 2FH,48H 0101 DAT2 DB 12H,10H,18H DAT FH DAT3 DW 7A5H H DAT4 DW 37H DAT H DAT5 DB 10H H H DAT A5H H DAT H 010A 00H DAT5 010B 10H 34

18 Address Data DAT FH H DAT H H H DAT A5H H DAT H 010A 00H DAT5 010B 10H AX BX CX DX MAIN PROC NEAR AH AL BH BL CH CL DH DL MOV AX,7745H MOV BX,0104H MOV DI,0001 MOV SI,0002 MOV AL,[BX] MOV AH,DAT2[SI] MOV AL,DAT1[DI] MOV AL,[BX+SI] 35 MOV AH,[BX+DI+3] SI di Address Data DAT FH H DAT H H H DAT A5H H DAT H 010A 00H DAT5 010B 10H AX BX CX DX MAIN PROC NEAR AH AL BH BL CH CL DH DL SI di MOV AX,7745H MOV BX,0104H MOV DI, MOV SI, MOV AL,[BX] 12 MOV AH,DAT2[SI] 18 MOV AL,DAT1[DI] 48 MOV AL,[BX+SI] MOV AH,[BX+DI+3] 07H

19 37 Example 07 ORG 100H STRT: JMP MAIN blank db 3 DUP (?) Data1 db 4FH Data2 db 8CH,5AH,0ACH,93H Data3 dw 4F59H,7EA3H Data4 db 0F4H,09H,8AH,5CH,6AH MAIN PROC NEAR MOV AX,2F8AH MOV BX,OFFSET Data4 MOV SI,3 MOV AL,Data1 MOV AH,BL MOV AL,Data2+3 MOV AX,Data3 MOV AL,Data2[SI] MOV AL,[BX+1] MOV AL,[SI+102H] MOV AL,[BX+SI 1] MOV AL,Data4[SI+2] MOV AL,Data2[SI+5] MOV AX,Data3+1 ENDP MAIN END start 38

20 ORG 100H Label Address Data STRT: JMP MAIN 0100 blank db 3 DUP (?) 0101 Data1 db 4FH 0102 Data2 db 8CH,5AH,0ACH,93H 0103 Data3 dw 4F59H,7EA3H 0104 Data4 db 0F4H,09H,8AH,5CH,6AH A 010B 010C 010D 010E 010F ORG 100H Label Address Data STRT: JMP MAIN blank 0100 blank db 3 DUP (?) 0101 Data1 db 4FH 0102 Data2 db 8CH,5AH,0ACH,93H 0103 Data3 dw 4F59H,7EA3H 0104 Data4 db 0F4H,09H,8AH,5CH,6AH Data F Data C A 0108 AC Data3 010A B 4F 010C A3 010D 7E Data4 010E F4 010F A C A

21 AX BX MAIN PROC NEAR AH AL BH BL MOV AX,2F8AH MOV BX,OFFSET Data4 MOV SI,3 MOV AL,Data1 MOV AH,BL MOV AL,Data2+3 MOV AX,Data3 MOV AL,Data2[SI] MOV AL,[BX+1] MOV AL,[SI+102H] MOV AL,[BX+SI 1] MOV AL,Data4[SI+2] MOV AL,Data2[SI+5] MOV AX,Data SI Addr ess Mode Label Addres Dat s a blank Data F Data C A 0108 AC Data3 010A B 4F 010C A3 010D 7E Data4 010E F4 010F A C A AX BX SI MAIN PROC NEAR AH AL BH BL MOV AX,2F8AH 2F 8A immediate MOV BX,OFFSET Data4 01 0E immediate MOV SI, immediate MOV AL,Data1 4F Direct MOV AH,BL 0E Reg. MOV AL,Data Direct MOV AX,Data3 4F 59 Direct MOV AL,Data2[SI] 93 Reg. Ind. MOV AL,[BX+1] 09 Reg. Ind. MOV AL,[SI+102H] 4F Reg. Ind. MOV AL,[BX+SI 1] 8A Reg. Ind. MOV AL,Data4[SI+2] B8 Reg. Ind. MOV AL,Data2[SI+5] F4 Reg. Ind. MOV AX,Data3+1 A3 4F Direct 42 Address Mode Label Addres Dat s a blank Data F Data C A 0108 AC Data3 010A B 4F 010C A3 010D 7E Data4 010E F4 010F A C A

22 43 Thanks,.. 44