X-Git-Url: http://git.dujemihanovic.xyz/projects?a=blobdiff_plain;f=boot%2Fx86%2Fboot.s;h=a7fe3c31ff1fb0f6cedf9a5fdd39f2718643dcac;hb=0b02cbac466992423caa450f9659b18d251a4158;hp=be6c6531d0a581d9c7b49fa91bbd977e6d52f183;hpb=63853960825f007827a79f704d291c372c807096;p=nameless-os.git

diff --git a/boot/x86/boot.s b/boot/x86/boot.s
index be6c653..a7fe3c3 100644
--- a/boot/x86/boot.s
+++ b/boot/x86/boot.s
@@ -15,7 +15,7 @@ KERNEL_OFFSET equ 1000h ; where we will load our kernel
 	jc reset_error ; halt if controller reset fails
 
 	mov ah, 2 ; instruct BIOS's interrupt 13h to read sectors
-	mov al, 10 ; load 10 sectors, might be excessive (for now) but it's still good to do so
+	mov al, 30 ; load 30 sectors, might be excessive (for now) but it's still good to do so
 	xor ch, ch ; read from 1st cylinder
 	mov cl, 2 ; start reading from 2nd sector, right after the boot sector
 	xor dh, dh ; read from 1st head
@@ -27,27 +27,34 @@ KERNEL_OFFSET equ 1000h ; where we will load our kernel
 	jc read_error ; halt if read fails
 	cmp al, 10 ; make sure we actually read 10 sectors
 	jl read_error ; halt if we didn't
-	jmp switch_to_pm ; if all is good, begin the switch to 32-bit protected mode
+
+	call check_a20
+	cmp ax, 1
+	jne a20_is_off
+
+a20_is_on
+	jmp switch_to_pm
+a20_is_off
+	call enable_a20
+	jmp switch_to_pm
 
 reset_error
 	mov bx, 0B800h
 	mov es, bx
 	mov byte [es:di], '1'
-	jmp halt
+	jmp $
 
 read_error
 	mov bx, 0B800h
 	mov es, bx
 	mov byte [es:di], '2'
-	jmp halt
-
-halt
 	jmp $
 
 %include "a20.s"
+%include "print.s"
 %include "protected.s"
 
-BOOT_DRIVE db 0 ; reserve a spot in RAM for our boot drive variable
+BOOT_DRIVE resb 1
 
 	times 510-($-$$) db 0
 	dw 0AA55h ; MBR signature