From 66289aa8ecfa07b20bad424eb9860b196641ef52 Mon Sep 17 00:00:00 2001
From: Brett Weiland <brett_weiland@bpcspace.com>
Date: Fri, 19 Mar 2021 10:54:25 -0500
Subject: first commit

---
 src/bootloader/bootloader.asm | 145 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 145 insertions(+)
 create mode 100644 src/bootloader/bootloader.asm

(limited to 'src/bootloader/bootloader.asm')

diff --git a/src/bootloader/bootloader.asm b/src/bootloader/bootloader.asm
new file mode 100644
index 0000000..14116db
--- /dev/null
+++ b/src/bootloader/bootloader.asm
@@ -0,0 +1,145 @@
+[bits 16]
+[extern _kernel_size]
+[extern _bootloader_stage1_size]
+[extern _kernel_loc]
+
+;TODO clean up unreal mode
+jmp stage0 
+times 3-($-$$) db 0x90 ; a temporary dirty fix to emulate a floppy disk insted of a hard risk 
+times 59 db 0          ; (TODO support hard disks) 
+
+stage0:
+
+jmp 0:.entry
+.entry:
+
+mov ax, 0
+mov ds, ax
+mov bp, ax 
+
+mov ds, ax
+mov es, ax
+
+mov ax, 0x8fc0
+mov ss, ax
+mov ax, 0xfffe 
+mov sp, ax
+
+mov al, 0x92
+or al, 2
+out 0x92, al
+
+mov [.boot_device], dl
+
+mov bx, .loadstage2_msg
+mov cx, 0 
+call bios_print
+
+; TODO put in an error message and a maximum fail count
+.load_stage1:
+mov al, _bootloader_stage1_size
+mov cl, 0x2       ; read sector 2 
+mov dx, 0x0       ; dest segment 0
+mov bx, 0x7e00    ; dest offst 0 
+call bios_disk.load_sectors 
+
+
+jmp mbr_end.entry
+
+.boot_device: db 0
+
+.loadstage2_msg: db "Loading (stage 2) bootloader...", 0
+
+%include "bootloader/bios_functions/bios_disk.asm"
+%include "bootloader/bios_functions/print.asm"
+
+times 510 - ($-$$) db 0  
+dw 0xaa55
+
+%include "bootloader/gdt.asm"
+
+boot_msg:
+.debugmsg: db "debugeroni", 0
+.kernel_loaded: db `Kernel loaded!\r\nBooting to protected, then long mode...`, 0
+.stage2_loaded: db `Done loading bootloader!\r\nLoading kernel...`, 0
+
+
+
+
+mbr_end:
+.entry:
+; entering unreal mode
+mov bx, boot_msg.stage2_loaded
+mov cx, 0
+call bios_print
+
+
+cli
+push ds
+
+lgdt [protected_gdt.descriptor]
+
+mov eax, cr0
+or al, 1
+mov cr0, eax
+
+jmp $+2
+
+mov bx, 0x10 ; descriptor 2, the data descriptor
+mov ds, bx   ; put it into the segment register
+mov es, bx   ; 
+
+and al, 0xfe
+mov cr0, eax
+
+pop ds
+sti
+;we are now in unreal mode
+
+mov cl, 5   ; starting sector TODO automate this
+mov edi, _kernel_loc
+.loop:
+mov al, 0x1   ; sector count
+mov dx, 0x0   ; dest addr segment
+mov bx, 0x500 ; dest addr offset
+call bios_disk.load_sectors
+
+
+inc cl
+
+push cx
+
+mov esi, 0x500
+mov ecx, 512
+a32 rep movsb
+nop
+
+mov bx, boot_msg.debugmsg
+mov cx, 0
+call bios_print
+
+pop cx
+
+cmp cl, _kernel_size
+je .loop_end
+
+jmp .loop
+
+.loop_end:
+
+mov bx, boot_msg.kernel_loaded
+mov cx, 0
+call bios_print
+
+
+call detect_arch
+call vbe_init
+done:
+
+call enter_longmode
+jmp $
+
+%include "bootloader/cpu_check.asm"
+%include "bootloader/video.asm"
+%include "bootloader/enter_kernel.asm"
+times 2048 - ($ - $$) db 0
-- 
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