Changeset 136

Timestamp:

Apr 8, 2017, 12:27:33 AM (8 years ago)

Author:

Ben Rietbroek

Message:

Reimplemented loading of the Master LVM sector [v1.1.1-testing]

The new method now uses the disk information gathered in an earlier
stage and just loads an already found Master LVM sector. This fix gets
rid of the ugly and faulty 'sec_per_track_table' way of doing it.

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) (2 diffs)

trunk/bootcode/regular/driveio.asm

@@ -1362 +1362 @@
 
 
-; ------------------------------------------------------
-; Rousseau: # Load the master LVM-sector if one exists #
-; ------------------------------------------------------
-; Load the master LVM-sector to get the number of sectors per track as
-; OS/2 views the drive. If no master LVM-sector is found it is assumed OS/2
-; is not installed. The master LVM-sector can be located at three different
-; places depending on drive size and partitioning scheme and driver used.
-; When DANIS506.ADD is used, the OS/2 extended geometry will be 255/127 for
-; drives >502GiB but <1TiB. Then the location will be sector 127 which
-; is LBA 126 (7Eh).
-; IBM1S506.ADD will always use 255/255 for the extended OS/2 geometry.
-; DANIS506.ADD will use 255/255 for drives >1TiB.
-; Then the location of the master LVM-sector will be 255 which is LBA 254 (FEh).
-; When OS/2 is installed on a huge drive that alread had a system on it, OS/2
-; will be confined to the lower 502GiB of the drive.
-; In this case the normal geometry from Int13X will be used.
-; This is also the case when no valid master LVM-sector can be found.
-;
-; Return CF when valid master LVM sector found, NC if not.
-; Loads sector at [LVMSector] !
+
+;##############################################################################
+;# When a disk has a Master LVM sector, it means it has been prepared for use
+;# by OS/2 and contains important information about how OS/2 views its geometry
+;# and other disk related properties. This function assumes the LBA address
+;# of the Master LVM sector has already been located and simply loads the
+;# sector into [LVMSector].
+;#
+;# Note that because this is an operation similar to the regular loading of
+;# sectors, the disk I/O semantics are used here. This means CF=0 when an LVM
+;# sector is successfully loaded and CF=1 otherwise.
+;##############################################################################
+;# ACTION   : Loads the Master LVM sector if one exists
+;# ----------------------------------------------------------------------------
+;# EFFECTS  : Modifies DAP structure and [LVMSector]
+;# ----------------------------------------------------------------------------
+;# IN       : DL     - BIOS disk number (80h,81h,etc)
+;# ----------------------------------------------------------------------------
+;# OUT      : CF=0   - Valid Master LVM sector found and loaded
+;##############################################################################
 DriveIO_LoadMasterLVMSector     Proc  Near
 
@@ -1395 +1395 @@
 ENDIF
 
+        ; Save all registers
         pusha
 
-        ; Loop over the sector-translation table,
-        ; process the first three values from high (255) to low.
-        ; (bios spt, most likely 63)
-        mov     cx,3
-    DriveIO_LoadMasterLVMSector_NextTry:
-        ; Number of sectors to read
-        mov     [INT13X_DAP_NumBlocks],1
-
-        ; Setup destination address
+        ; Check if BIOS disk number is valid
+        call    DriveIO_IsValidHarddisk
+        jc      DriveIO_LoadMasterLVMSector_error
+
+        ; Calculate the entry in the DISKINFO array for this disk
+        call    DriveIO_CalcDiskInfoPointer
+
+        ; Save the entry for later recalls
+        mov     bp, bx
+
+        ; Get the LBA address of the Master LVM sector
+        mov     ax, [bx+LocDISKINFO_LVM_MasterLBA+00h]
+        mov     bx, [bx+LocDISKINFO_LVM_MasterLBA+02h]
+
+        ; LBA of Master LVM sector cannot be 0, so none was found during
+        ; the gathering of disk information.
+        mov     cx, ax
+        or      cx, bx
+        jz      DriveIO_LoadMasterLVMSector_error
+
+        ; Load it into [LVMSector]
+        mov     di, ds
         mov     si, offset [LVMSector]
-        mov     word ptr [INT13X_DAP_Transfer+0],si
-        mov     ax, ds
-        mov     word ptr [INT13X_DAP_Transfer+2],ax
-
-        ; Get the sector-number of the next possible LVM sector (255,127,63)
-        ; using the translation table and the counter as the index
-        mov     bx,offset [secs_per_track_table]
-        mov     ax,cx   ; 1-based index to sec_per_track_table
-        dec     ax      ; Adjust to 0-based
-        xlatb           ; Get the (well known) SPT
-        dec     al      ; Minus 1 for LVM-record
-
-        ;
-        ; AX now contains the LBA address of the sector
-        ; that could be an LVM sector.
-        ; This is all in track0 so the address will not exceed 64kiB sectors.
-        ;
-
-
-IFDEF   AUX_DEBUG
-        IF 0
-        DBG_TEXT_OUT_AUX    'geo'
-        PUSHRF
-            call    DEBUG_DumpRegisters
-            call    AuxIO_DumpParagraph
-            call    AuxIO_TeletypeNL
-        POPRF
-        ENDIF
-ENDIF
-
-
-        ; Setup the requested LBA sector number
-        mov     word ptr [INT13X_DAP_Absolute+0],ax    ; LBA low                   NORMAL I/O GEBRUIKEN !
-        mov     word ptr [INT13X_DAP_Absolute+2],00h   ; LBA high
-        mov     si, offset [INT13X_DAP]                ; address request packet
-        mov     ah, 42h
-        int     13h                                    ; do the i/o, CF=1->error, CF=0->success
-;!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
-IFDEF   AUX_DEBUG
-        IF 0
-        pushf
-        pusha
-            pushf
-            xor     ax, ax
-            mov     al, dl
-            call    AuxIO_TeletypeHexWord
-            mov     al, '#'
-            call    AuxIO_Teletype
-            popf
-            mov     ax,0000h
-            rcl     al, 1
-            call    AuxIO_TeletypeHexWord
-            mov     al, '#'
-            call    AuxIO_Teletype
-            mov     ax,word ptr [INT13X_DAP_Absolute+0]
-            call    AuxIO_TeletypeHexWord
-            mov     al, '#'
-            call    AuxIO_Teletype
+        call    DriveIO_ReadSectorLBA
+        jc      DriveIO_LoadMasterLVMSector_error
+
+        ; Validate the Master LVM sector
+        call    LVM_ValidateSector
+
+        ; Complement success indicator to conform to semantics of this function
+        cmc
+
+        ; Master LVM sector was valid and is now loaded in [LVMSector]
+        jnc     DriveIO_LoadMasterLVMSector_ret
+
+    DriveIO_LoadMasterLVMSector_error:
+
+        ; Clear the sector buffer for safety reasons
+        mov     si, offset [LVMSector]
+        call    ClearSectorBuffer
+
+        ; Indicate no Master LVM sector loaded
+        stc
+
+    DriveIO_LoadMasterLVMSector_ret:
+
+        ; Restore all registers
         popa
-        popf
-        ENDIF
-ENDIF
-
-        cmc     ; Complement carry so we can exit imm. on error
-        jnc     DriveIO_LoadMasterLVMSector_End  ; oops, return with NC
-
-
-        mov     si,offset [LVMSector]
-
-        ; See if this is a valid LVM-sector
-        ; CY if valid
-        call    LVM_ValidateSector
-
-
-
-IFDEF   AUX_DEBUG
-        IF 0
-        DBG_TEXT_OUT_AUX    'lvm record'
-        PUSHRF
-            call    DEBUG_DumpRegisters
-            ;~ call    AuxIO_DumpSector
-            mov     cx, 7
-        @@:
-            call    AuxIO_DumpParagraph
-            call    AuxIO_TeletypeNL
-            add     si, 16
-            loop @B
-        POPRF
-        ENDIF
-ENDIF
-
-
-        ; Yep, we found the master LVM-sector
-        jc      DriveIO_LoadMasterLVMSector_Found
-
-        ; Try next location
-        loop    DriveIO_LoadMasterLVMSector_NextTry
-
-        ; No master LVM-sector found, set CF=false
-        clc
-
-    DriveIO_LoadMasterLVMSector_Found:
-        ; Store the address for later use.
-        mov     ax, word ptr [INT13X_DAP_Absolute]
-        mov     word ptr [MasterLVMLBA], ax
-
-    DriveIO_LoadMasterLVMSector_End:
-        popa
+
         ret
 DriveIO_LoadMasterLVMSector     Endp
+