I'm running on Ubuntu 12.10 64-bit.
I am trying to debug a simple assembly program in GDB. However, GDB's GUI mode (-tui) appears to be unable to locate the source code of my assembly file. I've rebuilt the project in the current directory and searched Google to no avail.
My commands:
nasm -f elf64 -g -F dwarf hello.asm
gcc -g hello.o -o hello
gdb -tui hello
Debug information appears to be loaded; I can set a breakpoint at main(), but the top half of the screen still displays '[ No Source Available ]'.
Here is hello.asm if you're interested:
; hello.asm a first program for nasm for Linux, Intel, gcc
;
; assemble: nasm -f elf -l hello.lst hello.asm
; link: gcc -o hello hello.o
; run: hello
; output is: Hello World
SECTION .data ; data section
msg: db "Hello World",10 ; the string to print, 10=cr
len: equ $-msg ; "$" means "here"
; len is a value, not an address
SECTION .text ; code section
global main ; make label available to linker
main: ; standard gcc entry point
mov edx,len ; arg3, length of string to print
mov ecx,msg ; arg2, pointer to string
mov ebx,1 ; arg1, where to write, screen
mov eax,4 ; write command to int 80 hex
int 0x80 ; interrupt 80 hex, call kernel
mov ebx,0 ; exit code, 0=normal
mov eax,1 ; exit command to kernel
int 0x80 ; interrupt 80 hex, call kernel
The problem in this case is that the assembler isn't producing line-number information for the debugger. So although the source is there (if you do "list" in gdb, it shows a listing of the source file - at least when I follow your steps, it does), but the debugger needs line-number information from the file to know what line corresponds to what address. It can't do that with the information given.
As far as I can find, there isn't a way to get NASM to issue the .loc directive that is used by as
when using gcc
for example. But as
isn't able to take your source file without generating a gazillion errors [even with -msyntax=intel -mmnemonic=intel -- you would think that should work].
So unless someone more clever can come up with a way to generate the .loc entries which gives the debugger line number information, I'm not entirely sure how we can answer your question in a way that you'll be happy with.