A new beginning

[nameless-os.git] / boot.s

diff --git a/boot.s b/boot.s
index 50730d0c39dd9566f3eef2e0b87582758af13444..a40b7508781e9dbc59b82587e003f2ccca6a21f8 100644 (file)
--- a/boot.s
+++ b/boot.s
@@ -1,22 +1,135 @@
-       bits 16 ; boot sectors run in real mode
-       org 7c00h ; boot sector is always loaded at 0x7c00
-
-       mov al, 1 ; update cursor after write
-       mov bh, 0 ; write to page 0
-       mov bl, 00000111b ; attribute: high nibble is foreground (light gray),
-                                         ; low nibble is background (black)
-                                         ; NOTE: in the binary, these will be inverted, so low nibble here will become high nibble in binary and vice versa!
-       mov cx, msg1end - msg1 ; size of message
-       mov dl, 0 ; column to write to
-       mov dh, 0 ; row to write to
-       push cs ; push code segment to stack
-       pop es ; pop pushed code segment to extra segment, this serves as the base to the string
-       mov bp, msg1 ; offset where the string is
-       mov ah, 13h ; write string subservice 
-       int 10h ; call BIOS interrupt 0x10
-       jmp msg1end ; jmp to endless loop
-       msg1 db "Gotta start somewhere"
-       msg1end: jmp msg1end
-
-       times 510-($-$$) db 0 ; fill with 0 until 0x1fc is reached
-       dw 0xaa55 ; BIOS MBR signature
+       bits 16
+       org 7C00h
+
+KERNEL_OFFSET equ 1000h
+
+       mov [BOOT_DRIVE], dl
+
+       mov bp, 9000h
+       mov sp, bp
+
+       mov di, 0
+
+       xor ax, ax
+       int 13h
+       jc reset_error
+
+       mov ah, 2
+       mov al, 10
+       xor ch, ch
+       mov cl, 2
+       xor dh, dh
+       xor bx, bx
+       mov es, bx
+       mov bx, KERNEL_OFFSET
+       int 13h
+       jc read_error
+       cmp al, 10
+       jl read_error
+       jmp switch_to_pm
+
+reset_error
+       mov bx, 0B800h
+       mov es, bx
+       mov byte [es:di], '1'
+       jmp halt
+
+read_error
+       mov bx, 0B800h
+       mov es, bx
+       mov byte [es:di], '2'
+       jmp halt
+
+       call switch_to_pm
+
+halt
+       jmp $
+
+switch_to_pm
+       mov bx, 0B800h
+       mov es, bx
+       mov byte [es:0], 'L'
+
+       cli
+       xor ax, ax
+       mov ds, ax
+       lgdt [gdt_desc]
+       
+       mov eax, cr0
+       or eax, 1
+       mov cr0, eax
+       jmp CODE_SEG:protected
+
+       bits 32
+protected
+       mov ax, DATA_SEG
+       mov ds, ax
+       mov ss, ax
+       mov es, ax
+       mov fs, ax
+       mov gs, ax
+       
+       mov ebp, 090000h
+       mov esp, ebp
+
+       mov ebx, pm_success
+       call pmprint
+
+       call KERNEL_OFFSET
+
+       jmp $
+
+pmprint
+       pusha
+       mov edx, video_memory
+
+.loop
+       mov al, [ebx]
+       mov ah, 0Fh
+
+       cmp al, 0
+       je .done
+
+       mov [edx], al
+       mov [edx+1], ah
+
+       inc ebx
+       add edx, 2
+
+       jmp .loop
+
+.done
+       popa
+       ret
+
+pm_success db "Now in protected mode", 0
+video_memory equ 0B8000h
+
+gdt_start
+null_seg
+       dq 0
+code_seg
+       dw 0FFFFh
+       dw 0
+       db 0
+       db 10011010b
+       db 11001111b
+       db 0
+data_seg
+       dw 0FFFFh
+       dw 0
+       db 0
+       db 10010010b
+       db 11001111b
+       db 0
+gdt_end
+gdt_desc
+       dw gdt_end - gdt_start - 1
+       dd gdt_start
+CODE_SEG equ code_seg - gdt_start
+DATA_SEG equ data_seg - gdt_start
+
+BOOT_DRIVE db 0
+
+       times 510-($-$$) db 0
+       dw 0AA55h