Question

I’m tring to assemble the following code using Nasm:

section .stage1_main 
extern stage1_get_stage2_addr
global stage1_main

stage1_main:
    sub rsp, 0x8
    call stage1_get_stage2_addr 
    cmp rax, -1 
    jz error
    add rsp, 0x8
    push stage1_main
    jmp rax 

error:
     ret

.stage1_main is a new section that I defined. the probelm is that Nasm define it as a DATA section

objdump -h main.o

main.o: file format elf64-x86-64

Sections:

Idx Name Size VMA LMA File off Algn
0 .stage1_main 0000001b 0000000000000000 0000000000000000 000001c0 2**0
CONTENTS, ALLOC, LOAD, RELOC, READONLY, DATA

I need a code section…
is there a way to define my section as a CODE section (like .text)

Answer 1

You can make your section directive state explicitly that the section’s contents are executable:

section .stage1_main exec

and you might also want to insist on 16-byte alignment (which nasm will do automatically for the .text section):

section .stage1_main exec align=16