mith College Computer Science CSC231-Assembly Fall 2017 Week #2 Dominique Thiébaut

Transcription

1 mith College Computer Science CSC231-Assembly Fall 2017 Week #2 Dominique Thiébaut

2 Outline Labs: emacs, assembly Assembly + Linking Process Object files DB directive: Everything is a byte! HexDump: we need to learn hexadecimal! Ascii Table

3 Emacs

4 Lab #1: Emacs ssh to aurora ssh -Y Emacs demo Basic commands ^X^C ^G ^D ^K ^Y cursor keys

5 Shell

6 Shell

7 Setup Shell aurora:~> setup231.sh You must logout and log back in to get bash as your default shell aurora:~> logout Good Bye! Connection to aurora.smith.edu closed. IMPORTANT

8 Setup Shell aurora:~> setup231.sh You must logout and log back in to get bash as your default shell aurora:~> logout Good Bye! Connection to aurora.smith.edu closed. ssh -Y password: Welcome to Linux Mint 17 Qiana (GNU/Linux generic x86_64) Welcome to Linux Mint * Documentation: Last login: Mon Sep 11 10:09: from cs231a-by@aurora ~ $

9 Setup Shell ssh -Y aurora:~> setup231.sh You must logout and log back in to get bash as your default shell aurora:~> logout Good Bye! Connection to aurora.smith.edu closed. ssh -Y password: Welcome to Linux Mint 17 Qiana (GNU/Linux generic x86_64) Welcome to Linux Mint * Documentation: Last login: Mon Sep 11 10:09: from cs231a-by@aurora ~ $

10 3 Useful Linux Commands ls (ell ess) list all files in a folder/directory cp copy file cd change directory

11 Linux Commands command -switches file-name(s)

12 Linux Commands command -switches file-name(s) ls -1 ls *.asm ls *.o s hello* ls -l man ls

13 Skeleton

14 Hello World!

15 Assembly+Linking nasm ld xxx.asm xxx.o xxx

16 Assembly+Linking nasm nasm ld xxx xxx.asm yyy.asm xxx.o yyy.o

17 DB: byte storage A byte is DB: "Define Byte of storage" stores information in a byte format (could be more than 1 byte) The X86 memory is a memory of bytes

18 ASCII Table

19 Data Section vs Memory message db "hello",10

20 Data Section vs Memory db "hello" db 10

21 Data Section vs Memory db "hel" db "lo" db 10

22 Data Section vs Memory db 104,"el" db "lo" db 10

23 We stopped here last time

24 Assembly Python section.data message db 10, "hello world!" db 10, "************", 10, 10 msglen equ $-message message = "\nhello world!\n************\n\n" section.text global _start _start: mov eax, 4 ; print mov ebx, 1 ; to stdout mov ecx, message ; string mov edx, msglen ; # of chars def main(): print( message ) int 0x80 ; ask Linux to print main() ;;; exit() mov mov int eax,1 ebx,0 0x80 ; final system call

25 section.data db "lo " db "hel" "world!", 10 equ$-msg3 Exercise _start: mov eax, 4 ; print mov ebx, 1 ; to stdout mov ecx, msg2 ; string mov edx, 3 int 0x80 mov eax, 4 ; print mov ebx, 1 ; to stdout mov ecx, msg1 ; string mov edx, 3 ; # of chars int 0x80 mov eax, 4 ; print mov ebx, 1 ; to stdout mov ecx, msg3 ; string mov edx, msglen; # of chars int 0x80 ; ask Linux to print What gets printed?

26 EMACS LAB TIME! LAB TIME! DO LAB1! Lab 1 Link

27 We stopped here last time

28 Plan for Today Review Last Lab Hexdump Lab1b Bash

29 Explore Solution Programs for Lab #1 Lab 1 Link

30 Hexdump hexdump -v -C helloworld f 45 4c ELF dc ( a a a a a e e b bb ba 0e b a cd 80 b bb a0 cd c 6c 6f 2c f 72 6c 64...Hello, World b0 21 0a 00 2e d e !...symtab..strt c e e ab..shstrtab..te d e xt..data e f b " ! a a e b ' cc b a b c c < c d e f0 a f1 ff a e f1 ff f1 ff 1d $ b b b c...hel c 6f 57 6f 72 6c e d 00 6d loworld2.asm.mes d c 45 4e 00 5f g.msglen._start a0 5f 5f f f bss_start._eda b f 65 6e ta._end b8 See link in Weekly Schedule page

31 Do Lab1b!