Changeset 124 for trunk/bootcode/regular/driveio.asm

Timestamp:

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

Author:

Ben Rietbroek

Message:

Use SI instead of BX for actions on sector buffers [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) (4 diffs)

trunk/bootcode/regular/driveio.asm

@@ -878 +878 @@
 ;# ACTION   : Locates the Master LVM sector on the specified disk
 ;# ----------------------------------------------------------------------------
-;# EFFECTS  : None
+;# EFFECTS  : Leaves [Scratch] with last sector read or cleared
 ;# ----------------------------------------------------------------------------
 ;# IN       : DL    - BIOS disk number of drive to search
@@ -909 +909 @@
         ; This is of course no problem since it is the MBR.
     DriveIO_LocateMasterLVMSector_next:
+        mov     si, offset [Scratch]    ; Use scratch area to load sectors
+        call    ClearSectorBuffer       ; Clear the scratch area
         clc                             ; Indicate Master LVM sector not found
         jcxz    DriveIO_LocateMasterLVMSector_done
 
-        ; Clear the sector buffer
-        mov     bx, cx                  ; Save our precious sector LBA
-        mov     cx, 100h                ; Clear 256 words is 512 bytes
-        mov     di, offset [TmpSector]  ; Offset of buffer
-        xor     ax, ax                  ; Value to sture
-        cld                             ; Increment DI each time
-        rep     stosw                   ; Store the value
-        mov     cx, bx                  ; Restore our precious sector LBA
-
-        ; Now read the LBA sector specified in CX
+        ; Read the LBA sector specified in CX
         mov     ax, cx                  ; LBA low
         xor     bx, bx                  ; LBA high
-        mov     di, ds                  ; Segment of temp buffer
-        mov     si, offset [TmpSector]  ; Offset of temp buffer
+        mov     di, ds                  ; Segment of scratch buffer
+        mov     si, offset [Scratch]    ; Offset of scratch buffer
         call    DriveIO_ReadSectorLBA   ; Read the sector
         lahf                            ; Save CF
@@ -944 +937 @@
         ; of the SPT value its OS/2 geometery specifies, which, in LBA terms
         ; is LVM SPT-1 -- let's check that...
-        mov     bx, offset [TmpSector]          ; Offset of the loaded LVM sector
+        mov     bx, offset [Scratch]            ; Offset of the loaded LVM sector
         mov     al, [bx+LocLVM_Secs]            ; Get the LVM SPT value (<=255)
         dec     al                              ; Adjust to LVM LBA
@@ -950 +943 @@
         inc     ah                              ; This one was found here
         cmp     al, ah                          ; If same, LVM LBA location OK
-        call    DEBUG_DumpRegisters
         jne     DriveIO_LocateMasterLVMSector_next