Changeset 169 for trunk/bootcode/regular/driveio.asm

Timestamp:

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

Author:

Ben Rietbroek

Message:

Added a double check when writing LVM sectors [v1.1.1-testing]

Writing an LVM sector is always the result of modifications to a
previously loaded one. So we first do a load and validate to make sure
the addressed sector contains LVM information.

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) (3 diffs)

trunk/bootcode/regular/driveio.asm

@@ -616 +616 @@
 
 IFDEF   AUX_DEBUG
-        IF 0
+        IF 1
         DBG_TEXT_OUT_AUX    'DriveIO_SaveLVMSectorXBR:'
         PUSHRF
             call    DEBUG_DumpRegisters
-            ;~ call    AuxIO_DumpSector
+            call    AuxIO_DumpSector
             ;~ call    AuxIO_DumpParagraph
             ;~ call    AuxIO_TeletypeNL
@@ -653 +653 @@
         sbb     bx, 0       ; Propagate borrow to LBA hi
 
+        ; Writing an LVM sector is always the result of modifications to a
+        ; previously loaded one. So, now that we have the LBA address of the
+        ; LVM sector, the one about to be overwritten should be there.
+        ; If it's not, something is seriously wrong and we quit immetiately.
+        pusha                           ; Push our context except the flags
+        mov     si, offset [Scratch]    ; Sector buffer to load the LVM sector
+        call    ClearSectorBuffer       ; Make sure no old LVM info is present
+        mov     di, ds                  ; Segment of buffer
+        call    DriveIO_ReadSectorLBA   ; Load the old LVM sector
+        call    LVM_ValidateSector      ; CF=1 if valid
+        cmc                             ; Complement for disk i/o semantics
+        popa                            ; Restore our context except the flags
+
+        ; OOPS, There was no LVM sector there !!
+        jc      DriveIO_SaveLVMSectorXBR_no_lvm
+
         ; Save the LVM sector pointed to by SI
         mov     di, ds                          ; Segment of that buffer
-        call    DriveIO_WriteSectorLBA          ; Read the LVM sector
-
-IFDEF   AUX_DEBUG
-        IF 0
+        call    DriveIO_WriteSectorLBA          ; Write the LVM sector
+
+IFDEF   AUX_DEBUG
+        IF 1
         DBG_TEXT_OUT_AUX    'LVMSecSaved'
         PUSHRF
@@ -676 +692 @@
 
     DriveIO_SaveLVMSectorXBR_no_lvm:
-        ; Indicate no valid LVM sector was loaded
+        ; Indicate no valid LVM sector was saved
         stc