Read bytes from boot drive

[nameless-os.git] / boot.s

diff --git a/boot.s b/boot.s
index 50730d0c39dd9566f3eef2e0b87582758af13444..3a8adc70a9d275e2e17faa53e6772aee0289e36c 100644 (file)
--- a/boot.s
+++ b/boot.s
@@ -1,22 +1,33 @@
        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-($-$$) db 0 ; fill with 0 until 0x1fc is reached
-       dw 0xaa55 ; BIOS MBR signature
+       org 7c00h ; boot sector is loaded at 0x7c00
+
+_start
+       mov [boot_drive], dl ; BIOS sets dl to number of boot drive, we don't want to forget this
+
+       mov bp, 8000h ; Move the stack away
+       mov sp, bp
+
+       push cs
+       pop es
+       mov bx, 9000h ; Load at 0000:9000
+       mov dh, 2 ; Load 5 sectors
+       mov dl, [boot_drive] ; Load from boot drive
+       call read_sectors
+
+       mov dx, [9000h] ; Print value at 9000h, should be 0xDEAD
+       call print_word 
+       mov dx, [9000h + 512] ; Print value at 9200h, should be 0xBEEF
+       call print_word
+
+       jmp $ ; Endless loop
+
+%include "print.s"
+%include "disk.s"
+
+boot_drive resb 1 ; Reserve 1 byte for boot drive number
+
+times 510-($-$$) db 0 ; fill with 0 until 0x1fc is reached
+dw 0AA55h ; BIOS MBR signature
+
+times 256 dw 0DEADh ; Fill in 2nd sector with 0xDEAD
+times 256 dw 0BEEFh ; Fill in 3rd sector with 0xBEEF