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Assembly Language
Basic ConceptsIA-32 Processor Architecture
Hardware
Intel386, Intel486, Pentium, or latest processors, AMD processors, or compatible processors. The same architectures, but different organizations.
Not working in MAC computers, SUN Sparc workstations.
Operating Systems
MS-DOS, Windows 95/98/ME/NT/2000/XP.
Advanced programs relating to direct hardware access and disk sector programming must be run under MS-DOS, Windows 95/98/ME.
Not working in Linux, MAC OS.
Programming Software
Editor: Microsoft Visual C++, TextPad, Notepad.
Assembler and linker: MASM 6.15. 32-but debugger: Microsoft Visual C++. Other: MASM 32.
Two Types of Programs
16-bit real-address mode: Run under MS-DOS and in the console window under MS-Windows. Written for the Intel 8086 and 8088 processors. Not discussed in this class.
32-bit protected mode: All the programs in this class.
Build Environments
Microsoft Visual C++ installed. Install MASM 6.15:
ftp://[email protected] Set tools: Build, run, and debug.
http://kipirvine.com/asm/4th/ide/vs6/index.htm
A Simple C File
#include <stdio.h>
void main() { int i;
i = 0x10000; i = i + 0x40000; i = i - 0x20000; printf("i= %d\n", i); }
Into Assembly Language 3: void main() 4: { 0040B450 push ebp 0040B451 mov ebp,esp 0040B453 sub esp,44h 0040B456 push ebx 0040B457 push esi 0040B458 push edi 0040B459 lea edi,[ebp-44h] 0040B45C mov ecx,11h 0040B461 mov eax,0CCCCCCCCh 0040B466 rep stos dword ptr [edi] 5: int i; 6: 7: i = 0x10000; 0040B468 mov dword ptr [ebp-4],10000h
8: i = i + 0x40000; 0040B46F mov eax,dword ptr [ebp-4] 0040B472 add eax,40000h 0040B477 mov dword ptr [ebp-4],eax 9: i = i - 0x20000; 0040B47A mov ecx,dword ptr [ebp-4] 0040B47D sub ecx,20000h 0040B483 mov dword ptr [ebp-4],ecx 10: printf("i= %d\n", i); 0040B486 mov edx,dword ptr [ebp-4] 0040B489 push edx 0040B48A push offset string "i= %d\n" (0041fe50) 0040B48F call printf (0040b710) 0040B494 add esp,8 11: }
A Simple MASM File
TITLE Add and Subtract (AddSub.asm)
; This program adds and subtracts 32-bit integers. ; Last update: 2/1/02
INCLUDE Irvine32.inc
.code main PROC
mov eax,10000h ; EAX = 10000h add eax,40000h ; EAX = 50000h sub eax,20000h ; EAX = 30000h call DumpRegs
exit main ENDP END main
Portability
Assembly language is not portable. Well-known processor families are Mot
orola 68x00, Intel IA-32, SUN Sparc, DEC Vax, and IBM-370.
Applications
Small embedded programs. Real-time applications. Computer game consoles. Help understand computer
hardware and operating systems. Subroutines hand optimized for
speed. Device drivers.
Irvine, Kip R. Assembly Language for Intel-Based Computers 5/e, 2007. Web site Examples
Virtual MachinesVirtual Machines
• Tanenbaum: Virtual machine concept• Programming Language analogy:
• Each computer has a native machine language (language L0) that runs directly on its hardware
• A more human-friendly language is usually constructed above machine language, called Language L1
• Programs written in L1 can run two different ways:• Interpretation – L0 program interprets and executes L1
instructions one by one• Translation – L1 program is completely translated into an L0
program, which then runs on the computer hardware
Irvine, Kip R. Assembly Language for Intel-Based Computers 5/e, 2007. Web site Examples
Translating LanguagesTranslating Languages
English: Display the sum of A times B plus C.
C++: cout << (A * B + C);
Assembly Language:
mov eax,Amul Badd eax,Ccall WriteInt
Intel Machine Language:
A1 00000000
F7 25 00000004
03 05 00000008
E8 00500000
Irvine, Kip R. Assembly Language for Intel-Based Computers 5/e, 2007. Web site Examples
Specific Machine LevelsSpecific Machine Levels
(descriptions of individual levels follow . . . )
Irvine, Kip R. Assembly Language for Intel-Based Computers 5/e, 2007. Web site Examples
Modes of OperationModes of Operation
• Protected mode• native mode (Windows, Linux)
• Real-address mode• native MS-DOS
• System management mode• power management, system security, diagnostics
• Virtual-8086 mode• hybrid of Protected
• each program has its own 8086 computer
Irvine, Kip R. Assembly Language for Intel-Based Computers 5/e, 2007. Web site Examples
Basic Execution EnvironmentBasic Execution Environment
• Addressable memory• General-purpose registers• Index and base registers• Specialized register uses• Status flags• Floating-point, MMX, XMM registers
Irvine, Kip R. Assembly Language for Intel-Based Computers 5/e, 2007. Web site Examples
Addressable MemoryAddressable Memory
• Protected mode• 4 GB
• 32-bit address
• Real-address and Virtual-8086 modes• 1 MB space
• 20-bit address
Web site Examples
Microsoft Visual C++
Web site Examples
Flags
Book OF D I x SF ZF x AC x P x CF
Visual C
OV UP EI x PL ZR x AC x PE x CY
Irvine, Kip R. Assembly Language for Intel-Based Computers 5/e, 2007. Web site Examples
General-Purpose RegistersGeneral-Purpose Registers
CS
SS
DS
ES
EIP
EFLAGS
16-bit Segment Registers
EAX
EBX
ECX
EDX
32-bit General-Purpose Registers
FS
GS
EBP
ESP
ESI
EDI
Named storage locations inside the CPU, optimized for speed.
Irvine, Kip R. Assembly Language for Intel-Based Computers 5/e, 2007. Web site Examples
Accessing Parts of RegistersAccessing Parts of Registers
• Use 8-bit name, 16-bit name, or 32-bit name• Applies to EAX, EBX, ECX, and EDX
Irvine, Kip R. Assembly Language for Intel-Based Computers 5/e, 2007. Web site Examples
Index and Base RegistersIndex and Base Registers
• Some registers have only a 16-bit name for their lower half:
Irvine, Kip R. Assembly Language for Intel-Based Computers 5/e, 2007. Web site Examples
Some Specialized Register Uses Some Specialized Register Uses (1 of 2)(1 of 2)
• General-Purpose• EAX – accumulator• ECX – loop counter• ESP – stack pointer• ESI, EDI – index registers• EBP – extended frame pointer (stack)
• Segment• CS – code segment• DS – data segment• SS – stack segment• ES, FS, GS - additional segments
Irvine, Kip R. Assembly Language for Intel-Based Computers 5/e, 2007. Web site Examples
Some Specialized Register Uses Some Specialized Register Uses (2 of 2)(2 of 2)
• EIP – instruction pointer• EFLAGS
• status and control flags
• each flag is a single binary bit
Irvine, Kip R. Assembly Language for Intel-Based Computers 5/e, 2007. Web site Examples
Status FlagsStatus Flags• Carry
• unsigned arithmetic out of range• Overflow
• signed arithmetic out of range• Sign
• result is negative• Zero
• result is zero• Auxiliary Carry
• carry from bit 3 to bit 4• Parity
• sum of 1 bits is an even number
Irvine, Kip R. Assembly Language for Intel-Based Computers 5/e, 2007. Web site Examples
Floating-Point, MMX, XMM RegistersFloating-Point, MMX, XMM Registers
• Eight 80-bit floating-point data registers
• ST(0), ST(1), . . . , ST(7)
• arranged in a stack
• used for all floating-point arithmetic
• Eight 64-bit MMX registers
• Eight 128-bit XMM registers for single-instruction multiple-data (SIMD) operations
Irvine, Kip R. Assembly Language for Intel-Based Computers 5/e, 2007. Web site Examples
IA-32 Memory ManagementIA-32 Memory Management
• Real-address mode• Calculating linear addresses• Protected mode• Multi-segment model• Paging
Irvine, Kip R. Assembly Language for Intel-Based Computers 5/e, 2007. Web site Examples
Real-Address modeReal-Address mode
• 1 MB RAM maximum addressable• Application programs can access any area
of memory• Single tasking• Supported by MS-DOS operating system
Irvine, Kip R. Assembly Language for Intel-Based Computers 5/e, 2007. Web site Examples
Segmented MemorySegmented Memory
Segmented memory addressing: absolute (linear) address is a combination of a 16-bit segment value added to a 16-bit offset
li ne
ar a
ddr e
sse
s
one segment
Irvine, Kip R. Assembly Language for Intel-Based Computers 5/e, 2007. Web site Examples
Calculating Linear AddressesCalculating Linear Addresses
• Given a segment address, multiply it by 16 (add a hexadecimal zero), and add it to the offset
• Example: convert 08F1:0100 to a linear address
Adjusted Segment value: 0 8 F 1 0
Add the offset: 0 1 0 0
Linear address: 0 9 0 1 0
Irvine, Kip R. Assembly Language for Intel-Based Computers 5/e, 2007. Web site Examples
Protected ModeProtected Mode (1 of 2) (1 of 2)
• 4 GB addressable RAM• (00000000 to FFFFFFFFh)
• Each program assigned a memory partition which is protected from other programs
• Designed for multitasking• Supported by Linux & MS-Windows
Irvine, Kip R. Assembly Language for Intel-Based Computers 5/e, 2007. Web site Examples
Protected modeProtected mode (2 of 2) (2 of 2)
• Segment descriptor tables• Program structure
• code, data, and stack areas
• CS, DS, SS segment descriptors
• global descriptor table (GDT)
• MASM Programs use the Microsoft flat memory model
Irvine, Kip R. Assembly Language for Intel-Based Computers 5/e, 2007. Web site Examples
Flat Segment ModelFlat Segment Model
• Single global descriptor table (GDT).• All segments mapped to entire 32-bit address space
Irvine, Kip R. Assembly Language for Intel-Based Computers 5/e, 2007. Web site Examples
Multi-Segment ModelMulti-Segment Model
• Each program has a local descriptor table (LDT)• holds descriptor for each segment used by the program
Irvine, Kip R. Assembly Language for Intel-Based Computers 5/e, 2007. Web site Examples
PagingPaging
• Supported directly by the CPU• Divides each segment into 4096-byte blocks called
pages• Sum of all programs can be larger than physical
memory• Part of running program is in memory, part is on disk• Virtual memory manager (VMM) – OS utility that
manages the loading and unloading of pages• Page fault – issued by CPU when a page must be
loaded from disk
Irvine, Kip R. Assembly Language for Intel-Based Computers 5/e, 2007. Web site Examples
Levels of Input-OutputLevels of Input-Output
• Level 3: Call a library function (C++, Java)• easy to do; abstracted from hardware; details hidden• slowest performance
• Level 2: Call an operating system function• specific to one OS; device-independent• medium performance
• Level 1: Call a BIOS (basic input-output system) function• may produce different results on different systems• knowledge of hardware required• usually good performance
• Level 0: Communicate directly with the hardware• May not be allowed by some operating systems
Irvine, Kip R. Assembly Language for Intel-Based Computers 5/e, 2007. Web site Examples
Displaying a String of CharactersDisplaying a String of Characters
When a HLL program displays a string of characters, the following steps take place:
Irvine, Kip R. Assembly Language for Intel-Based Computers 5/e, 2007. Web site Examples
ASM Programming levelsASM Programming levels
ASM programs can perform input-output at each of the following levels:
Library Level 3