63 lines
1.2 KiB
NASM
63 lines
1.2 KiB
NASM
# OwOS
|
|
# Copyright Benjamin Kyd (c) 2019
|
|
|
|
# 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
|
|
|
|
.section .bss
|
|
.align 16
|
|
stack_bottom:
|
|
.skip 16384 # 16 KiB
|
|
stack_top:
|
|
|
|
.section .text
|
|
.global _start
|
|
.type _start, @function
|
|
|
|
_start:
|
|
# Settup stack
|
|
mov $stack_top, %esp
|
|
push %ebx
|
|
push %eax
|
|
|
|
call kernel_main
|
|
|
|
cli
|
|
1: hlt
|
|
jmp 1b
|
|
|
|
|
|
.global INIT_FPU
|
|
.type INIT_FPU, @function
|
|
|
|
INIT_FPU:
|
|
# FPU Config
|
|
VAL_037F:
|
|
.hword 0x037F
|
|
VAL_037E:
|
|
.hword 0x037E
|
|
VAL_037A:
|
|
.hword 0x037A
|
|
# Configure FPU
|
|
cli
|
|
mov %cr0, %ecx
|
|
or $0b00110010, %ecx
|
|
and $0xFFFFFFFB, %ecx
|
|
mov %ecx, %cr0
|
|
fldcw VAL_037F
|
|
fldcw VAL_037E
|
|
fldcw VAL_037A
|
|
fninit
|
|
|
|
.size _start, . - _start
|