I use a fresh install of Ubuntu 22.04, nasm 2.15.05 and gdb 12.1.

Is there anything that has to be done different to be able see the source when debugging x64-Assembly?
The same steps that worked for x86-Assembly do not work for x64-Assembly.

Here is a short breakdown:

x86/helloWorld.asm

section .data
msg:     db     'Hello, World!',0       ; define string as label

section .text
global start                            ; must be declared for linker

start:                                  ; entry point
        mov     eax, 4                  ; system call number (sys_write)
        mov     ebx, 1                  ; file descriptor (stdout)
        mov     ecx, msg                ; message
        mov     edx, 13                 ; message length
        int     0x80                    ; call kernel

        mov     eax, 1                  ; system call number (sys_exit)
        int     0x80                    ; call kernel

I assemble and link that using following commands:

nasm -f elf32 -g -F dwarf helloWorld.asm

ld -m elf_i386 -e start -o helloWorld helloWorld.o

I start gdb: gdb helloWorld

In gdb I set a breakpoint:

(gdb) break helloWorld.asm:9

Breakpoint 1 at 0x8049000: file helloWorld.asm, line 9.

I use lay n to get to the layout that is a split of regs/src on top and cmd at bottom.
As expected, regs is unavailable and in src is the content of helloWorld.asm.
Nice.

x64/helloWorld.asm

section .data
msg:     db     'Hello, World!',0       ; define string as label

section .bss

section .text
global start                            ; must be declared for linker

start:                                  ; entry point
        mov     rax, 1                  ; system call number (sys_write)
        mov     rdi, 1                  ; file descriptor (stdout)
        mov     rsi, msg                ; message
        mov     rdx, 13                 ; message length
        syscall                         ; call kernel

        mov     rax, 60                 ; system call number (sys_exit)
        mov     rdi, 0                  ; 0 = success exit code
        syscall                         ; call kernel

I assemble and link that using following commands:

nasm -f elf64 -g -F dwarf helloWorld.asm

ld -m elf_x86_64 -e start -o helloWorld helloWorld.o

I start gdb: gdb helloWorld

In gdb I set a breakpoint:

(gdb) break helloWorld.asm:9

No line 9 in file "helloWorld.asm".

Make breakpoint pending on future shared library load? (y or [n])

I use lay n to get to the layout that is a split of regs/src on top and cmd at bottom.
Regs is unavailable and [ No Source Available ].

When I enter (gdb) list, the source becomes available until the next step I do in the program.

Architecture seems to be fine as well:

(gdb) show architecture

The target architecture is set to "auto" (currently "i386:x86-64").

So why does gdb tell me that my source file is a future shared library and why does the source view not work properly?
What can I do to fix that?

I already tried:

• Using a fresh install of gdb and Linux
• Checked if sources are available to gdb when debugging x64 (they are; helloWorld and helloWorld.asm)
• Set the file manually (changed nothing)

I expected:

• To be able to debug without any inconveniences