I'm trying to learn assembly and I'm using Nasm v2.10.07 on Mac OS X (Snow Leopard).
I can compile, but I need to read the Debug file, that is a .o file.
This is what I compile:
global _main
section.data
M db 5,4,3,2,1
dim equ $-M
section.text
_main:
mov edi, M
mov eax, 0
mov ebx, 1
int 80h
This is how I compile:
nasm -f elf -g -F stabs myfile.asm -o myfile.o
And this is the result:
ELF����������������������#�������4�����(�
�������������������������������������������������������������������–������������������������������������?��������������������������������0��M��������������������������������Ä��ê���������������"����������������2������������������*��� �����������P�����������������4��������������`��T����������������:��������������¿��������������������C��� �����������–��0���������������ø����∏����ª���ÕÄ�%define $�The Netwide Assembler 0.98.40 (Apple Computer, Inc. build 11)���.text�.comment�.shstrtab�.symtab�.strtab�.rel.text�.stab�.stabstr�.rel.stab��%d����������������������������Òˇ�������������Òˇ������������������������������������������������������Òˇ�������������,�������������myfile.asm�section.data�M�dim�section.text�_main��%define $_%1 ������%define������������d�����������D����������D���������D��
�������D� ��������D�
�����%define $_%�myfile.asm��%de����� �����,�����8�����D�����P�����
So, what should I do to read in the correct way the debug without those strange symbols?
To show the contents of the .stabs section, use objdump -g myfile.o or objdump -G myfile.o
To get the full source code with line numbers taken from the debug section, use objdump -S -l myfile.o
Related
The problem is that I have a filesystem in documents/assembly that goes like this:
test.s:
.global _start
.text
_start:
mov $60, %rax # exit
mov $0, %rdi # return code 0
syscall
test.o:
\* exists \*
compile.bash:
as -o test.o test.s && ld -e _start -o test.s test.o && chmod 777 test.o && (./test ; echo $?)
But when I try running compile.bash I get:
ld: dynamic executables or dylibs must link with libSystem.dylib for architecture x86_64
And when I try running test.o:
bash: ./test.o: cannot execute binary file
I'm using gnu assembler, But instead of gcc in the tutorial I say as.
I tried changing the command, But what happened was that it gave a lot of errors. I'm using macos monetary version 12.5.1 (21G83). What I expected was it to print 0 when running the command, But it didn't.
I have the following file hello.asm:
section .text
global _start ;must be declared for linker (ld)
_start: ;tells linker entry point
mov edx,len ;message length
mov ecx,msg ;message to write
mov ebx,1 ;file descriptor (stdout)
mov eax,4 ;system call number (sys_write)
int 0x80 ;call kernel
mov eax,1 ;system call number (sys_exit)
int 0x80 ;call kernel
section .data
msg db 'Hello, world!', 0xa ;our dear string
len equ $ - msg ;length of our dear string
On mac, how would i turn it into a .o file. On linux i would do
nasm -f elf64 -o hello.o hello.asm
ld -o hello hello.o
then it could be called with
./hello
I have already installed Xcode and MacPorts, Thanks
Using:
nasm -o hello.o hello.asm
should work, that is, to produce an .o file. typically on OS X you do something such as:
nasm -f macho -o hello.o hello.asm
I'm writing Hello World in NASM, and I can get it to echo Hello World to the console, but the program segfaults if I don't run it with Make.
Trace with Makefile:
$ make
nasm -f macho -o hello.o --prefix _ hello.asm
ld -o hello hello.o -arch i386 -lc -macosx_version_min 10.6 -e _start -no_pie
./hello
Hello World!
Trace with manual commands:
$ nasm -f macho -o hello.o --prefix _ hello.asm
$ ld -o hello hello.o -arch i386 -lc -macosx_version_min 10.6 -e _start -no_pie
$ ./hello
Segmentation fault: 11
hello.asm:
[bits 32]
section .data
msg: db "Hello World!", 0
section .text
global start
extern puts
extern exit
start:
push msg
call puts
add esp, 4
push 0
call exit
Makefile:
# Linux defaults
FORMAT=-f elf
MINV=
ARCH=-arch i386
LIBS=
RUN=./
EXECUTABLE=hello
PREFIX=
ENTRY=
PIE=
# Windows
ifeq (${MSYSTEM},MINGW32)
FORMAT=-f win32
EXECUTABLE=hello.exe
PREFIX=--prefix _
ENTRY=-e _start
ARCH=
LIBS=c:/strawberry/c/i686-w64-mingw32/lib/crt2.o -Lc:/strawberry/c/i686-w64-mingw32/lib -lmingw32 -lmingwex -lmsvcrt -lkernel32
ENTRY=
RUN=
endif
# Mac OS X
ifeq ($(shell uname -s),Darwin)
FORMAT=-f macho
PREFIX=--prefix _
ENTRY=-e _start
LIBS=-lc
MINV=-macosx_version_min 10.6
PIE=-no_pie
endif
all: test
test: $(EXECUTABLE)
$(RUN)$(EXECUTABLE)
$(EXECUTABLE): hello.o
ld -o $(EXECUTABLE) hello.o $(ARCH) $(LIBS) $(MINV) $(ENTRY) $(PIE)
hello.o: hello.asm
nasm $(FORMAT) -o hello.o $(PREFIX) hello.asm
clean:
-rm $(EXECUTABLE)
-rm hello.o
Specs:
ld 64-134.9
LLVM 3.1svn
NASM 0.98.40
Make 3.81
Xcode 4.5
Mac OS X 10.8.1
MacBook Pro 2009
2 things, your hello world string is not NULL terminated and as I mentioned in another post, when you use C functions, you MUST adjust esp after each call
You tore down your stack frame twice:
mov esp, ebp
pop ebp
...
leave
You only need one of those, since leave is equivalent to mov esp, ebp; pop ebp.
See http://michaux.ca/articles/assembly-hello-world-for-os-x for several example hello world programs. Note that all of them exit the program explicitly with
; 2a prepare the argument for the sys call to exit
push dword 0 ; exit status returned to the operating system
; 2b make the call to sys call to exit
mov eax, 0x1 ; system call number for exit
sub esp, 4 ; OS X (and BSD) system calls needs "extra space" on stack
int 0x80 ; make the system call
because you cannot ret from an entry point (there's nothing to return to).
Also note that if you call the function main and don't supply the e option to ld, then libc's entry point will be called. In that case, it is permissible to ret since you will return control to libc (which calls exit on your behalf).
I am on Mac Os X and I am having trouble compiling a .s ARM assembly file.
my .s file is this:
mov r0, r1
just to see if it works.
but when i do
arm-elf-as my.s
i get an
a.out file.
i do
chmod +x a.out
and
./a.out
but it says
cannot execute binary file
this has me confused, because it should be able to execute if i compiled it with arm-elf-as. How do i go about compiling this .s?
You're assembling it allright, you just can't run it on a Mac since Macs don't have ARM CPUs. If you install Xcode with iOS support, you can compile ARM code:
# the file
$ cat foo.s
mov r0, r1
# compile with llvm-gcc
$ /Developer/Platforms/iPhoneOS.platform/usr/bin/llvm-gcc-4.2 -arch armv6 -c foo.s
# resulting file is ARM object file
$ file foo.o
foo.o: Mach-O object arm
# and you can disassemble it
$ otool -v -t foo.o
foo.o:
(__TEXT,__text) section
00000000 e1a00001 mov r0, r1
You won't be able to run anything, because for that you'll need a runtime system and and ARM CPU. You can use -isysroot /Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS3.2.sdk or similar to compile for the iPhoneOS for example.
i have some problems with linking nasm program for macos:
GLOBAL _start
SEGMENT .text
_start:
mov ax, 5
mov bx, ax
mov [a], ebx
SEGMENT .data
a DW 0
t2 DW 0
fry$ nasm -f elf test.asm
fry$ ld -o test test.o -arch i386
ld: warning: in test.o, file was built for unsupported file format which is not the architecture being linked (i386)
ld: could not find entry point "start" (perhaps missing crt1.
fry$ nasm -f macho test.asm
fry$ ld -o test test.o -arch i386
ld: could not find entry point "start" (perhaps missing crt1.o)
can anyone help me?
The Mac OS X linker can't link ELF objects. It works only with the Mach-O executable format. Unless you want to figure out how to translate the object files, you'll probably be better off writing code that works with the Mac OS X assembler.
Edit: As #Fry mentions in the comment below, you can make nasm put out Mach-O objects. In that case, the problem is simple - take the _ off of _start in both places in your source file. The result links fine.
nasm -f macho test.asm
ld -e _start -o test test.o
For people who need to stick with the elf format and develop on a mac, you need a cross compiler...
http://crossgcc.rts-software.org/doku.php?id=compiling_for_linux
Then you can proceed with something similar to this...
/usr/local/gcc-4.8.1-for-linux32/bin/i586-pc-linux-ld -m elf_i386 -T link.ld -o kernel kasm.o kc.o