Changeset 168 for trunk/bootcode/regular/driveio.asm

Timestamp:

Apr 8, 2017, 12:28:07 AM (8 years ago)

Author:

Ben Rietbroek

Message:

Fake write succes on removable disks [v1.1.1-testing]

Accessing, and thus writing, removable disks is highly dependent on
the BIOS USB mass-storage emulation. Also, some removable disks have
a small switch to set it to read-only. We don't want such stuff to halt
AiR-BOOT with a 'SAVE ERROR', so we fake success in such cases.

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

@@ -1050 +1050 @@
 
     DriveIO_WriteSectorLBA_exit:
+
+        ; Skip the removable drive check on success
+        jnc     @F
+
+        ; Here, CF=1 because of a failure.
+        ; This could be from a removable drive that is set to read-only,
+        ; in which case we want to fake success. What this boils down to
+        ; is that CY must be set to !IsRemovable.
+        call    DriveIO_CalcDiskInfoPointer         ; Get DISKINFO pointer
+        mov     dx, [bx+LocDISKINFO_I13X_Flags]     ; Get INT13X flags
+        xor     dl, 04h                             ; Invert 'removable' bit
+        and     dl, 04h                             ; Mask it out
+        rcr     dl, 3                               ; Move it to CY
+
+    @@:
 
         ; Pop all registers