Provide config file via CX (len) and BX (ptr) to kernel entry

boot/fat.asm

@@ -103,30 +103,38 @@ main:
   ; clusters start after rootdir
   mov [cluster_offset], ax
 
+  ; Load kernel
   mov bx, prog
-
   mov ax, kernel_name
   call load_file
   mov bp, 0x3332
   jc error
 
-  mov si, bx
+  ; Load config file after kernel
-  sub si, prog
+  push bx
-
-  push si
-
   mov ax, config_name
   call load_file
+  pop bx
 
-  pop si
+  ; Write a null byte after config file
+  mov BYTE [bx+di], 0
 
-  int3
+  ; Setup registers for kernel
-
+  xor ax, ax
-  ; restore boot drive number
+  ; CX is size of config
+  mov cx, di
+  ; DL is drive number
+  xor dx, dx
   mov dl, [fdc.drv]
+  ; BX is offset of config
+  sub bx, prog
+  ; the pointers are 0
+  xor bp, bp
+  xor si, si
+  xor di, di
 
-  ; jump into target
+  ; jump into kernel
-  jmp 0x07C0:0x0000
+  jmp (prog>>4):0
 
 ; Load a file into memory
 ; IN	AX	pointer to 8.3 filename