Hello assambler

scvalex (Alexandru Scvortov) — Wed, 02 May 2007 18:40:17 GMT

The canonical Hello World program in assambler.

Compile it with:
nasm -f elf hello.s
ld -s -o hello hello.o

Helloworld is a function. It uses the write system call to print to stdout (file descriptor 1).

This is written in NASM (Intel) syntax, hence it will not work with gas, tasm or masm. It was written for Linux. The details may vary on other platforms.

Download NASM for free at http://nasm.sourceforge.net/



section .data

  hello: db "Hello world!",10

  hellolen: equ $ - hello



section .text

  global _start



_start:

  call helloworld



  mov eax,1 ; start exit procedure

  mov ebx,0



  int 80h



helloworld:

  mov eax,4 ; 4 is the code for the write system call

  mov ebx,1 ; 1 is the fd for stdout

  mov ecx,hello ; the address of the string

  mov edx,hellolen ; the length of the string



  int 80h ; trigger an interrupt; this should be 21h for DOS



  ret

Automated GNU Makefile

scvalex (Alexandru Scvortov) — Wed, 02 May 2007 17:43:36 GMT

A simple automated GNU Makefile to build and link c/c++/asm projects. All the variables that need to be tweaked are located at the begining:
PROGNAME: the name of the executable to be built
CC: the C compiler
CPP: the C++ compiler
ASM: the assambler
LD: the linker

This searches for all *.c, *.cpp and *.s files and compiles them into objects. It then links all the files into a single executable.

The strip rule is used to strip all unwanted symbols from the resulting executable. This usually results in a significant (think 40%) size optimisation.



$(VERBOSE).SILENT:



PROGNAME = prog



CC = gcc

CC += -c

CPP = g++

CPP += -c

ASM = nasm

ASM += -f elf -d ELF_TYPE

LD = g++



OBJFILES = $(patsubst %.c,%.o,$(wildcard *.c))

OBJFILES += $(patsubst %.s,%.o,$(wildcard *.s))

OBJFILES += $(patsubst %.cpp,%.o,$(wildcard *.cpp))



all: $(PROGNAME)



clean:

	@echo "Cleaning object files"

	@echo "    rm -f     *.o"

	rm -f *.o

	@echo "Cleaning backups"

	@echo "    rm -f     *~"

	rm -f *~

	@echo "Removing programme"

	@echo "    rm -f     "$(PROGNAME)

	rm -f $(PROGNAME)



%.o: %.s

	@echo "Assambling "$@

	@echo "    ASM       "$<

	$(ASM) $<



%.o: %.c

	@echo "Compiling "$@

	@echo "    CC        "$<

	$(CC) $<



%.o: %.cpp

	@echo "Compiling "$@

	@echo "    CPP       "$<

	$(CPP) $<



$(PROGNAME): $(OBJFILES)

	@echo "Linking "$@

	@echo "    LD        -o "$(PROGNAME)"        "$(OBJFILES)

	$(LD) -o $(PROGNAME) $(OBJFILES)



strip: $(PROGNAME)

	@echo "Stripping "$(PROGNAME)

	echo -n "Size of "$(PROGNAME)" before strip is "

	ls -sh $(PROGNAME) | cut -d' ' -f1

	@echo "    strip     "$(PROGNAME)

	strip $(PROGNAME)

	echo -n "Size of "$(PROGNAME)" after strip is "

	ls -sh $(PROGNAME) | cut -d' ' -f1



nothing:

	@echo "Nothing to do; quitting  :("

	@echo "HINT: Try make all"

DZone Snippets: assambler code

Hello assambler

Automated GNU Makefile