Unable to disasembly my app -- no debugging information found

Question

I'm trying to disassembly app written in assembly. I'm on Linux, x64:

$ objdump -d my_app 

my_app:     file format elf64-x86-64

That's it. What's wrong with it? It's not a simple hello world of a few lines, it's around 200 lines of code.

The same with gbd:

$ gdb -q my_app 
Reading symbols from my_app...(no debugging symbols found)...done.
(gdb) 

And

$ radare2 my_app 
Warning: Cannot initialize section headers
Warning: Cannot initialize strings table
Warning: Cannot initialize dynamic strings
Warning: Cannot initialize dynamic section
 -- Calculate checksums for the current block with the commands starting with '#' (#md5, #crc32, #all, ..)

update:

$ objdump -D my_app 

my_app:     file format elf64-x86-64

compiling:

   $ fasm my_app.asm 
   # => my_app 

update2:

; simplified

format ELF64 executable 3

include "import64.inc"
interpreter "/lib64/ld-linux-x86-64.so.2"
needed "libc.so.6"
import printf, close

segment readable
    A equ 123
    B equ 222
    C equ 333

segment readable writeable
    struc s1 a, b, c {
      .a1 dw a
      .b1 dw b
      .c dd c
    }

    msg:
        .m1 db "aaa", 0
        .m2 db "bbb", 0
        .m3 db "ccc", 0

segment readable executable
entry $
    mov rax, 2
    mov rdi, "something.txt"
    mov rsi, 0
    syscall

    ; .............
    ; omitted

Answer 1

Asking fasm to directly produce an ELF binary without the use of a linker will only create segments but no sections in the output. This confuses some tools. In particular objdump -d is specifically documented to operate on sections. Note that gdb can still debug and disassemble it, if you give it some addresses, e.g. the entry point.