Why does the stack grow after passing a label in following code example? I haven’t used any push instruction.

I need to trust the stack so I need granular control. I know my setup isn’t conventional, that’s on purpose.

If this is intended behaviour, is there a way around, so I can for example predict stack growth?

Makefile

test:
    nasm -g -F dwarf -felf64 test2.asm -o test.o
    ld -m elf_x86_64 --omagic test.o -o test

test2.asm

global _start

section .text
 
_start:
    xor     rax, rax
    xor     rbx, rbx
    mov     rsi, knitter
    mov     rdi, intermediary
test:
    mov     al, byte [rsi + rbx]
end:
    jmp     end

len_array equ 4096
intermediary: resb len_array

knitter:  db  "zend:", 10, 
              0   ; End of string

output gdb

(gdb) make -e test
make: 'test' is up to date.
(gdb) b _start
Breakpoint 2 at 0x400080: file test2.asm, line 6.
(gdb) r
The program being debugged has been started already.
Start it from the beginning? (y or n) y
Starting program: /home/nico/Dropbox/Projects/datalp/test

Breakpoint 2, _start () at test2.asm:6
6           xor     rax, rax
(gdb) n
7           xor     rbx, rbx
(gdb)
8           mov     rsi, knitter
(gdb) bt
#0  _start () at test2.asm:8
(gdb) n
9           mov     rdi, intermediary
(gdb) bt
#0  _start () at test2.asm:9
(gdb) n
test () at test2.asm:11
11          mov     al, byte [rsi + rbx]
(gdb) bt
#0  test () at test2.asm:11
#1  0x0000000000000001 in ?? ()
#2  0x00007fffffffe8ee in ?? ()
#3  0x0000000000000000 in ?? ()
(gdb)