Detect muliple active partitions

slrboot.nasm

@@ -32,18 +32,86 @@ relocated:
 mov si, message ; Put address of the null-terminated string to output into 'si'
 call print      ; Call our string-printing routine
 
-mov bx, [partition_1.start_LBA]
+; Check for more than one active partition that we can start from. 
+xor bx, bx
+xor cx, cx
+mov ax, [partition_1.active_partition]
+call dumpax
+cli
+hlt
+cmp ax, 0x80
+jne check_p_2
+mov bx, 0x01 ; Partion 1 active
+inc cx
+
+check_p_2:
+mov ax, [partition_2.active_partition]
+cmp ax, 0x80
+jne check_p_3
+inc cx
+mov bx, 0x02 ; Partion 2 active
+
+check_p_3:
+mov ax, [partition_3.active_partition]
+cmp ax, 0x80
+jne check_p_4
+inc cx
+mov bx, 0x03 ; Partion 3 active
+
+check_p_4:
+mov ax, [partition_4.active_partition]
+cmp ax, 0x80
+jne eval_active_partion_number
+inc cx
+mov bx, 0x04 ; Partion 4 active
+
+eval_active_partion_number: 
+cmp cx, 1
+je boot_partition:
+; here goes wait call, for the user to enter debug mode. 
+; Wating for 2 seconds: 
+mov ah, 0x86   ; code for waiting interupt call
+mov cx, 0x001e ; high count of microseconds
+mov dx, 0x8480 ; low count
+int 0x15
+.busy_wait_for_key:
+xor ax, ax 
+mov ah, 0x01 ; BIOS call to wait for key
+int 0x16
+
+mov bx, 1
+
+boot_partition:
+; IMPORTANT bx, has to hold the value 1-4 for the partiotion that wanted to be booted.  
+
+
+mov ax, partition_1
+.loop:
+    cmp bx, 1 
+    je break
+    add ax, 0x10
+    dec bx
+    jmp .loop
+break:
+
+add ax, 7 ; This is the offset to fetch the LBA start adress of the partition record
+
+mov bx, [ax] ; first part of LBA
 mov WORD [DAPACK.lba_addr_dw_low], bx
-mov bx, [partition_1.start_LBA + 1]
+inc ax ; next part
+mov bx, [ax]
 mov WORD [DAPACK.lba_addr_dw_low + 1], bx
-mov bx, [partition_1.start_LBA + 2]
+inc ax ; next part
+mov bx, [ax]
 mov WORD [DAPACK.lba_addr_dw_low + 2], bx
-mov bx, [partition_1.start_LBA + 3]
+inc ax ; next part
+mov bx, [ax]
 mov WORD [DAPACK.lba_addr_dw_low + 3], bx
 mov WORD [DAPACK.blkcnt],          0x01  
 mov WORD [DAPACK.db_addr_segment], 0x0000
 mov WORD [DAPACK.db_addr_offset],  0x7c00
-mov si, DAPACK                          ; address of "disk address packet"
+mov si, DAPACK  ; address of "disk address packet"
+xor ax, ax                          
 mov ah, 0x42                            ; READ
 mov dl, [disk_identifier] 
 int 0x13
@@ -194,8 +262,10 @@ message db 'SLRboot for SingOS! v0.2.0.3-exp',13,10,0
 ;boot_system db 'Read SingOS from disk', 13, 10, 0
 ;error_str db 'Error', 0
 ;success_str db 'Success', 0
+boot_this_partition: dw 0
 disk_identifier db 0
 
+
 DAPACK:
   .dap_Size:         db  0x10   ; This is always 16 bytes (0x10)
   .rev_byte:         db  0x0    ; reserved byte, should always be zero
@@ -217,7 +287,7 @@ partition_1:
 .size db 0x00, 0xC8, 0x03, 0x00  
 
 partition_2:
-.active_partition db 0x00 
+.active_partition db 0x80 
 .start_CHS db 0x8C, 0x3E, 0x0F 
 .disk_type db 0x83 
 .end_CHS db 0xFF, 0xFF, 0xFF