myos/boot.s at master · Tchou/myos · GitHub

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# Declare constants for the multiboot header.
.set ALIGN,    1<<0             # align loaded modules on page boundaries
.set MEMINFO,  1<<1             # provide memory map
.set FLAGS,    ALIGN | MEMINFO  # this is the Multiboot 'flag' field
.set MAGIC,    0x1BADB002       # 'magic number' lets bootloader find the header
.set CHECKSUM, -(MAGIC + FLAGS) # checksum of above, to prove we are multiboot

.section .multiboot
.align 4
.long MAGIC
.long FLAGS
.long CHECKSUM

# Reserve some space for the stack
.section .bss
.align 16
stack_bottom:
.skip 16384 # 16 KiB
stack_top:

# Entry point (see linker.ld)
.section .text
.global _start
.type _start, @function
_start:

        # Setup the stack pointer
	mov $stack_top, %esp

        # Initialize stuff if needed

        # Main entry point of kernel.c
	call kernel_main


        # Busy loop if we arrive here.
	cli
1:	hlt
	jmp 1b