15 213 The course that gives CMU its Zip Machine Level Programming I Introduction Sept 04 2008 Topics Assembly Programmer s Execution Model Accessing Information z Registers z Memory class04 ppt Arithmetic operations 15 213 F 08 IA32 Processors Totally Dominate Computer Market Evolutionary Design Starting in 1978 with 8086 Added more features as time goes on Still support old features although obsolete Complex Instruction Set Computer CISC Many different instructions with many different formats z But only small subset encountered with Linux programs 2 Hard to match performance of Reduced Instruction Set Computers RISC But Intel has done just that 15 213 F 08 x86 Evolution Programmer s View Abbreviated Name 8086 Transistors 1978 29K 16 bit processor Basis for IBM PC DOS Limited to 1MB address space DOS only gives you 640K 386 3 Date 1985 275K Extended to 32 bits Added flat addressing Capable of running Unix Referred to as IA32 32 bit Linux gcc uses no instructions introduced in later models 15 213 F 08 x86 Evolution Programmer s View Machine Evolution 486 1989 1 9M Pentium 1993 3 1M Pentium MMX 1997 4 5M PentiumPro 1995 6 5M Pentium III 1999 8 2M Pentium 4 2001 42M Core Duo 2006 291M Added Features Instructions to support multimedia operations z Parallel operations on 1 2 and 4 byte data both integer FP Instructions to enable more efficient conditional operations Linux GCC Evolution 4 None 15 213 F 08 New Species IA64 Name Date Transistors Itanium 2001 10M Extends to IA64 a 64 bit architecture Radically new instruction set designed for high performance Can run existing IA32 programs z On board x86 engine Joint project with Hewlett Packard Itanium 2 2002 221M Big performance boost Itanium 2 Dual Core 2006 1 7B Itanium has not taken off in marketplace 5 Lack of backward compatibility 15 213 F 08 X86 Evolution Clones Advanced Micro Devices AMD Historically z AMD has followed just behind Intel z A little bit slower a lot cheaper Recently z Recruited top circuit designers from Digital Equipment Corp and other downward trending companies z Exploited fact that Intel distracted by IA64 z Now are close competitors to Intel Developed x86 64 its own extension to 64 bits z Started eating into Intel s high end server market 6 15 213 F 08 Intel s 64 Bit Dilemma Intel Attempted Radical Shift from IA32 to IA64 Totally different architecture Executes IA32 code only as legacy Performance disappointing AMD Stepped in with Evolutionary Solution x86 64 now called AMD64 Intel Felt Obligated to Focus on IA64 Hard to admit mistake or that AMD is better 2004 Intel Announces EM64T extension to IA32 7 Extended Memory 64 bit Technology Almost identical to x86 64 Our Saltwater fish machines 15 213 F 08 Our Coverage IA32 The traditional x86 x86 64 The emerging standard Presentation Book has IA32 Handout has x86 64 Lecture will cover both Labs 8 Lab 2 x86 64 Lab 3 IA32 15 213 F 08 Assembly Programmer s View CPU Memory Addresses Registers P C Object Code Program Data OS Data Data Condition Codes Instructions Programmer Visible State PC Stack Program Counter z Address of next instruction z Called EIP IA32 or RIP x86 64 Register File z Heavily used program data Condition Codes z Store status information about most recent arithmetic operation z Used for conditional branching 9 Memory z Byte addressable array z Code user data some OS data z Includes stack used to support procedures 15 213 F 08 Turning C into Object Code Code in files p1 c p2 c Compile with command gcc O p1 c p2 c o p z Use optimizations O z Put resulting binary in file p text C program p1 c p2 c Compiler gcc S text Asm program p1 s p2 s Assembler gcc or as binary Object program p1 o p2 o Static libraries a Linker gcc or ld binary 10 Executable program p 15 213 F 08 Compiling Into Assembly C Code int sum int x int y int t x y return t Generated IA32 Assembly sum pushl ebp movl esp ebp movl 12 ebp eax addl 8 ebp eax movl ebp esp popl ebp ret Obtain with command gcc O S code c Produces file code s 11 15 213 F 08 Assembly Characteristics Minimal Data Types Integer data of 1 2 or 4 bytes z Data values z Addresses untyped pointers Floating point data of 4 8 or 10 bytes No aggregate types such as arrays or structures z Just contiguously allocated bytes in memory Primitive Operations Perform arithmetic function on register or memory data Transfer data between memory and register z Load data from memory into register z Store register data into memory Transfer control z Unconditional jumps to from procedures z Conditional branches 12 15 213 F 08 Object Code Code for sum Assembler Translates s into o 0x401040 sum Binary encoding of each instruction 0x55 Total of 13 0x89 Nearly complete image of executable bytes 0xe5 code Each 0x8b instruction 1 Missing linkages between code in 0x45 2 or 3 bytes different files 0x0c Starts at 0x03 address Linker 0x45 0x401040 0x08 Resolves references between files 0x89 Combines with static run time libraries 0xec z E g code for malloc printf 0x5d 0xc3 Some libraries are dynamically linked z Linking occurs when program begins execution 13 15 213 F 08 Machine Instruction Example C Code int t x y Add two signed integers Assembly addl 8 ebp eax Add 2 4 byte integers z Long words in GCC parlance Similar to expression z Same instruction whether signed or unsigned x y Or x y t int eax int ebp eax ebp 2 0x401046 03 45 08 Register eax Memory M ebp 8 Register eax Return function value in eax Object Code 14 Operands 3 byte instruction Stored at address 0x401046 15 213 F 08 Disassembling Object Code Disassembled 00401040 sum 0 55 1 89 e5 3 8b 45 0c 6 03 45 08 9 89 ec b 5d c c3 d 8d 76 00 push mov mov add mov pop ret lea ebp esp ebp 0xc ebp eax 0x8 ebp eax ebp esp ebp 0x0 esi esi Disassembler objdump d p Useful tool for examining object code Analyzes bit pattern of series of instructions Produces approximate rendition of assembly code Can be run on either a out complete executable or o file 15 15 213 F 08 Alternate Disassembly Disassembled Object 0x401040 0x55 0x89 0xe5 0x8b 0x45 0x0c 0x03 0x45 0x08 0x89 0xec 0x5d 0xc3 0x401040 0x401041 0x401043 0x401046 0x401049 0x40104b 0x40104c 0x40104d sum sum 1 sum 3 sum 6 sum 9 sum 11 sum 12 sum 13 push mov mov add mov pop ret lea ebp esp ebp 0xc ebp eax 0x8 ebp eax ebp esp ebp 0x0 esi esi Within gdb Debugger gdb p disassemble sum Disassemble procedure x 13b sum 16 Examine the 13 bytes starting at sum 15 213 F 08 What Can be Disassembled objdump d WINWORD EXE WINWORD EXE file format pei i386 No
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