DOS/boot.s at main · PythonCoders45/DOS · GitHub

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; Declare Multiboot Header constants
MBALIGN equ 1 << 0 ; Align loaded modules on page boundaries
MEMINFO equ 1 << 1 ; Provide memory map
FLAGS equ MBALIGN | MEMINFO ; Multiboot 'flag' field
MAGIC equ 0x1BADB002 ; Magic number letting bootloader find header
CHECKSUM equ -(MAGIC +FLAGS) ; Checksum required by Multiboot standard

; Multiboot Header
section .multiboot
align4
dd MAGIC
ddFLAGS
dd CHECKSUM

; Allocate 16 KB stack for C code
section .bss
align16
stack_bottom:
resb16384 ; 16 KB
stack_top:

; Kernel Entry Point
section .text
global_start
externkernel_main

_start:
 ; Set up the stack pointer register (ESP)
movesp, stack_top

 ; Call our main kernel function in C!
call kernel_main

 ; If kernel_main unexpectedly returns, halt CPU in an infinite loop
.halt:
cli
hlt
jmp .halt