I am running a virtual box on win10 64 bit home host. On the virtual box i have installed ubuntu 18.04 64 bit.
I downloaded a sample assembly program from the site related to the book im learning from "Assembly language step-by-step".
this is the program:
; vim: ft=nasm
;
; Build using these commands (works on 32-bit Linux)
; nasm -f elf -g -F stabs eatsyscall.asm
; ld -o eatsyscall eatsyscall.o
;
; Build on 64-bit Linux: (Linux 3.13.7-1-ARCH #1 x86_64 GNU/Linux)
; nasm -f elf64 -g -F stabs eatsyscall.asm
; ld -o eatsyscall eatsyscall.o
;
; Build on OSX (although the instructions are not valid for its architecture)
; nasm -f macho eatsyscall.asm
; ld -arch i386 -macosx_version_min 10.5 -no_pie -e _start -o eatsyscall eatsyscall.o
;
section .data ; contains initialized data
EatMsg: db "Eat at Joe's!",10
EatLen equ $ - EatMsg
section .bss ; contains uninitialized data
section .text ; contains code
global _start ; entry point found by linker (default is _start)
_start:
nop ; needed to allow debugging with gdb - lldb not properly working ATM
mov eax,4 ; Specify sys_write syscall
mov ebx,1 ; specify file descriptor: stdout
mov ecx,EatMsg ; pass message offset
mov edx,EatLen ; pass message length
int 80H ; make syscall to output text to stdout
mov eax,1 ; specify exit syscall
mov ebx,0 ; return code of zero
int 80H ; make syscall to terminate program
when i try to debug it with either kdbg or directly with gdb the same 2 weird things happen (weird to me but might just be my complete inexperience):
when i try to put a break point at line 29 "mov eax, 4" - the debugger doesnt stop there. It stops only if i put 3 breakpoints one after the other starting at the above mentioned line.
when the debugger does stop, if i try to do a step-into command the debugger tells me that the program terminated with the "SIGSEGV" signal - segmentation fault. The debugging program doesnt terminate but the program i am trying to debug.
I tried searching for this online but couldnt find anything related to the problem im experiencing.
All help would be appreciated.
