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- ; Identical to lesson 13's boot sector, but the %included files have new paths
- [org 0x7c00]
- KERNEL_OFFSET equ 0x1000 ; The same one we used when linking the kernel
- mov [BOOT_DRIVE], dl ; Remember that the BIOS sets us the boot drive in 'dl' on boot
- mov bp, 0x9000
- mov sp, bp
- mov bx, MSG_REAL_MODE
- call print
- call print_nl
- call load_kernel ; read the kernel from disk
- call switch_to_pm ; disable interrupts, load GDT, etc. Finally jumps to 'BEGIN_PM'
- jmp $ ; Never executed
- %include "boot/print.asm"
- %include "boot/print_hex.asm"
- %include "boot/disk.asm"
- %include "boot/gdt.asm"
- %include "boot/32bit_print.asm"
- %include "boot/switch_pm.asm"
- [bits 16]
- load_kernel:
- mov bx, MSG_LOAD_KERNEL
- call print
- call print_nl
- mov bx, KERNEL_OFFSET ; Read from disk and store in 0x1000
- mov dh, 16 ; Our future kernel will be larger, make this big
- mov dl, [BOOT_DRIVE]
- call disk_load
- ret
- [bits 32]
- BEGIN_PM:
- mov ebx, MSG_PROT_MODE
- call print_string_pm
- call KERNEL_OFFSET ; Give control to the kernel
- jmp $ ; Stay here when the kernel returns control to us (if ever)
- BOOT_DRIVE db 0 ; It is a good idea to store it in memory because 'dl' may get overwritten
- MSG_REAL_MODE db "Started in 16-bit Real Mode", 0
- MSG_PROT_MODE db "Landed in 32-bit Protected Mode", 0
- MSG_LOAD_KERNEL db "Loading kernel into memory", 0
- ; padding
- times 510 - ($-$$) db 0
- dw 0xaa55
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