Changeset 125 for trunk/bootcode/regular

Timestamp:

Apr 8, 2017, 12:27:24 AM (9 years ago)

Author:

Ben Rietbroek

Message:

Corrected using BIOS disk number as index [v1.1.1-testing]

Bit 7 of the BIOS disk number is not a flag indicating a harddisk,
but rather 80h is the disk number offset for the first harddisk.

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/partscan.asm (modified) (2 diffs)

trunk/bootcode/regular/partscan.asm

@@ -66 +66 @@
         xor     bh, bh                          ; Zero upper part of index
         mov     bl, dl                          ; Get BIOS drive-number
-        and     bl, 7fh                         ; Strip bit 7
+        sub     bl, 80h                         ; Now 0-based index
         shl     bx, 3                           ; Mult by 4 for DWORD
         add     bx, offset [LVM_MasterSecs]     ; Add the base offset
@@ -83 +83 @@
             xor     bh, bh
             mov     bl, dl
-            and     bl, 7fh
+            sub     bl, 80h
             shl     bx, 3
             add     bx, offset [LVM_MasterSecs]