Debug symbols in NASM (once more)

Question

This question has been asked several times on StackOverflow but I tried all the answers and I still cannot get NASM to include DWARF debugging symbols.

I am using NASM 2.13.02 under Ubuntu 18.04 64-bit. I am not sure if I am still missing something?

In case it matters, I would actually like to use both LLDB and GDB.

Thanks.

Here is my code:

section .bss
section .text

global _start

_start:
    mov ebx, 0
    mov eax, 1
    int 80h

Here is how I build and link it:

nasm -g -F dwarf -f elf64 hello.asm
ld -s -o hello hello.o

The resulting file is:

$ ls -la hello
-rwxr-xr-x 1 terry terry 352 Sep  4 18:21 hello
$

Trying to check if DWARF data is included:

$ dwarfdump hello
No DWARF information present in hello
$

Running it under gdb:

$ gdb ./hello 
GNU gdb (Ubuntu 8.1-0ubuntu3.2) 8.1.0.20180409-git
[... snip copyright ...]
Reading symbols from ./hello...(no debugging symbols found)...done.
(gdb)

Because you specified `-s` with `ld` which is strip all so it removed the debug info in the final executable as well. — Michael Petch, Sep 04 '20 at 16:32
Ouch, @MichaelPetch, thanks a lot, that was some mistake from a newcomer. Thanks a lot! — , Sep 04 '20 at 16:36
@MichaelPetch Please feel free to move your comment to an answer and I will be happy to accept it. — , Sep 04 '20 at 16:38

score 6 · Accepted Answer · 2020-09-04T20:13:24.197

6

I am self-answering my own question based on a suggestion from @Michael Petch who was the person that actually found the root cause.

The issue was that I was using ld with -s which means "strip all", including debug symbols, i.e. I was undermining my own effort.

The correct commands should be:

nasm -g -F dwarf -f elf64 hello.asm
ld -o hello hello.o

Now, with gdb:

$ gdb ./hello 
GNU gdb (Ubuntu 8.1-0ubuntu3.2) 8.1.0.20180409-git
[.. snip copyright ..]
Reading symbols from ./hello...done.

(gdb) b _start
Breakpoint 1 at 0x400080: file hello.asm, line 7.

(gdb) run
Starting program: /home/terry/hello 

Breakpoint 1, _start () at hello.asm:7
7       xor ebx, 0
(gdb) 
$

edited Sep 04 '20 at 20:13

answered Sep 04 '20 at 18:19

3

In a couple days don't forget to come back and accept your own answer. Have a great weekend! – Michael Petch Sep 04 '20 at 19:53
1

Thanks, will do for sure! – Sep 04 '20 at 20:13

Debug symbols in NASM (once more)

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