Allow also loading EttinOS with the bootloader

boot.asm

@@ -134,19 +134,34 @@ search_root:
 		jmp .entry
 
 	.isfile:
-		mov cx, 11
+		.nor86:
-		mov bx, kernel_name
+			cmp word [si + 8], 'KR'
+			jne .ettinos
+			cmp byte [si + 10], 'N'
+			jne .ettinos
 
-		.compare:
+			mov ax, [si + 26] ; First cluster
-			lodsb
+			mov [kernel_cluster], ax
-			cmp al, [bx]
-			jne .nomatch
-			inc bx
-			loop .compare
 
-		jmp found
+			jmp .skipentry
 
-	.nomatch:
+		.ettinos:
+			mov cx, 11
+			mov bx, ettinos_kernel_name
+
+			.compare:
+				lodsb
+				cmp al, [bx]
+				jne .nextentry
+				inc bx
+				loop .compare
+
+			; SI points to 11 bytes after the start of the
+			; entry, so adjust offset
+			mov ax, [si - 11 + 26] ; First cluster
+			mov [ettinos_kernel_cluster], ax
+
+	.nextentry:
 		; Each entry is 32 bytes long
 		; During each iteration of the compare loop, si is
 		; incremented and cx is decremented
@@ -160,14 +175,47 @@ search_root:
 
 	.end:
 
+which_found:
+	mov bx, [kernel_cluster]
+	mov cx, [ettinos_kernel_cluster]
+
+	test bx, bx
+	jz .no_nor86
+	test cx, cx
+	jz found
+
+	mov si, choose_msg
+	.loop:
+		lodsb
+		test al, al
+		jz .end
+
+		mov ah, 0xe
+		int 0x10
+		jmp .loop
+
+		.end:
+
+	xor ax, ax
+	int 0x16
+
+	cmp ah, 0x12 ; E-key
+	je found_cx
+	jmp found
+
+	.no_nor86:
+		test cx, cx
+		jnz found_cx
+
 notfound:
 	mov si, notfound_msg
 	jmp fatal_error
 
+found_cx:
+	mov bx, cx
+
 found:
-	; SI points to 11 bytes after the start of the entry, so adjust all
+	mov ax, bx
-	; offsets
-	mov ax, [si - 11 + 26] ; First cluster
 	push ax
 
 	; Load OS at the start of the memory
@@ -178,7 +226,8 @@ found:
 	.tosector:
 		; Adjust the cluster number to account for first two
 		; "clusters" in the FAT being used for metadata
-		sub ax, 2
+		dec ax
+		dec ax
 
 		; Scale by number of sectors per cluster
 		xor bx, bx
@@ -217,11 +266,7 @@ found:
 		;    ^ where we start reading on odd cluster numbers
 		;    ^^^^^ loading word: 0xXYZA
 		test ax, 1
-		jnz .odd
+		jz .even
-
-		.even:
-			and dx, 0x0fff
-			jmp .check_cluster
 
 		.odd:
 			shr dx, 1
@@ -229,6 +274,9 @@ found:
 			shr dx, 1
 			shr dx, 1
 
+		.even:
+			and dx, 0x0fff
+
 	.check_cluster:
 		mov ax, dx
 
@@ -245,14 +293,12 @@ execute_kernel:
 	jmp 0:0x500
 
 ; Note: bx will point to after the read data
+; Note: ax, cx, and di will be clobbered
 loadsectors:
-	push ax
-	push cx
 	push dx
-	push di
 
 	.loop:
-		mov di, 3 ; Retry thrice
+		mov di, 3 + 1 ; Retry thrice, + 1 is since we dec first
 
 		.retry:
 
@@ -283,17 +329,15 @@ loadsectors:
 
 			; cylinder (track)
 			mov ch, al
-			shr ax, 1
+			;shr ax, 1
-			shr ax, 1
+			;shr ax, 1
-			and al, 0xC0
+			;and al, 0xC0
-			or cl, al
+			;or cl, al
 
-		mov ah, 2
+		mov ax, 0x0201
-		mov al, 1
 		mov dl, [drivenumber]
 		int 0x13
 
-		; TODO: Handle reset & retry
 		jc .error
 
 		pop cx
@@ -304,18 +348,14 @@ loadsectors:
 
 		loop .loop
 
-	pop di
 	pop dx
-	pop cx
-	pop ax
 	ret
 
 	.error:
 		; Do we still have retries remaining?
 		mov si, diskerror_msg
-		test di, di
-		jz fatal_error ; No, fail
 		dec di
+		jz fatal_error ; No, fail
 
 		; Yes, reset disk
 		xor ah, ah
@@ -339,10 +379,14 @@ hang:
 	jmp hang
 
 
-kernel_name: db "NOR86   KRN"
+kernel_cluster dw 0
+ettinos_kernel_cluster dw 0
 
-notfound_msg: db "Kernel not found", 0
+ettinos_kernel_name db "SYSTEM  BIN"
-diskerror_msg: db "Disk error", 0
+
+notfound_msg db "No kernel", 0
+diskerror_msg db "Disk error", 0
+choose_msg db "(E)ttinOS/Nor86?", 0
 
 times 510-($-$$) db 0
 db 0x55, 0xaa