Changeset 120 for trunk/bootcode/regular/driveio.asm

Timestamp:

Apr 8, 2017, 12:27:19 AM (8 years ago)

Author:

Ben Rietbroek

Message:

Added function to validate BIOS disk number [v1.1.1-testing]

CAUTION:
This is a testbuild !
AirBoot uses the BIOS to access disks and a small coding error can trash
partition tables or other vital disk structures. You are advised to make
backups of TRACK0 and EBRs before using this testbuild. More info at:
​https://rousseaux.github.io/netlabs.air-boot/pdf/AirBoot-v1.1.0-manual.pdf

File:

• trunk/bootcode/regular/driveio.asm (modified) (1 diff)

trunk/bootcode/regular/driveio.asm

@@ -1870 +1870 @@
 
 
+;------------------------------------------------------------------------------
+; Check if the BIOS disk number in DL is a harddisk and in range
+;------------------------------------------------------------------------------
+; IN    : DL BIOS disk number (80h etc)
+; OUT   : CF=1 if invalid disk number or out of range
+; NOTE  : Only modifies flags
+;------------------------------------------------------------------------------
+DriveIO_IsValidHarddisk     Proc    Near    Uses dx
+        cmp     dl, 80h                 ; BIOS disk number must be at least 80h
+        jb      @F                      ; Not a harddisk, exit with CY
+        mov     dh, dl                  ; Save to do compare
+        sub     dh, 80h                 ; Now 0 based disk number
+        inc     dh                      ; Now 1 based disk number
+        cmp     [TotalHarddiscs], dh    ; Out of range, exit with CY
+    @@: ret
+DriveIO_IsValidHarddisk     EndP
+
 
 ; Values for sectors per track table corresponding to DriveIO_IsHugeDrive return value.