how to get the return value of a function called in x86 code example

Example: func assembly

func:
    xor eax, eax
    mov eax, 10
    add eax, 5
    ret ;// essentially identical to: pop [register] -> jmp [register]


_start:
    call func
    mov ebx, eax ;// Address of this instruction is pushed onto the stack
    ;// ebx is now 15