Changeset 150

Timestamp:

Apr 8, 2017, 12:27:53 AM (8 years ago)

Author:

Ben Rietbroek

Message:

Reimplemented the saving of LVM sectors [v1.1.1-testing]

This new method does away with ugly and faulty adjustments which
assumed LVM sectors were located below actual partition starts,
which is true most of the time, but not always, especially not for
the first primary partition which could be offset more than SPT.

Because MBR and EBR locations are now used, the need to distinguish
between primary and logical partitions is also not needed anymore.

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

@@ -538 +538 @@
 
 
-; Keeps DS:SI for caller, saves at anytime w/o checks (!)
-DriveIO_SaveLVMSector   Proc Near  Uses ax bx cx dx
-
-IFDEF   AUX_DEBUG
-        IF 0
+;##############################################################################
+;# The location of LVM sectors depends on the OS/2 geometry used when the disk
+;# was prepared. This geometry is present in the Master LVM sector, which has
+;# already been located if it exists. All partitions, whether primary or
+;# logical, have an entry in a partition table. For primary partitions this
+;# table is located in the MBR, while for logical partitions this table is
+;# located in the EBR for that logical partition. An LVM record is located
+;# LVM_SPT-1 sectors above an MBR or EBR. The Master LVM record contains the
+;# information for all primary partitions. For logical partitions, the LVM
+;# sector only has one entry, because EBRs are chained. The global LVM info,
+;# like disk-name, sectors per track, etc. is replicated between the Master
+;# LVM sector and LVM sectors corresponding to logical partitions. This info
+;# is kept in sync by the OS/2 LVM Engine.
+;##############################################################################
+;# ACTION   : Attempts to save the corresponding LVM sector for a partition
+;# ----------------------------------------------------------------------------
+;# EFFECTS  : Modifies DAP structure and writes LVM sector to disk
+;# ----------------------------------------------------------------------------
+;# IN       : MEM   - Location info is in [CurPartition_Location]
+;#          : SI    - Pointer to sector buffer
+;# ----------------------------------------------------------------------------
+;# OUT      : CF=1  - failure, no valid LVM sector was saved
+;##############################################################################
+DriveIO_SaveLVMSector   Proc Near  Uses ax bx cx dx di
+
+IFDEF   AUX_DEBUG
+        IF 1
         DBG_TEXT_OUT_AUX    'DriveIO_SaveLVMSector:'
         PUSHRF
-            ;~ call    DEBUG_DumpRegisters
+            call    DEBUG_DumpRegisters
             ;~ call    AuxIO_DumpParagraph
             ;~ call    AuxIO_TeletypeNL
@@ -552 +574 @@
 ENDIF
 
-        test    byte ptr [CFG_IgnoreLVM], 1            ; We are supposed to ignore LVM, so
-        jnz     DIOSLVMS_SevereError          ;  don't save at anytime (security!)
-        mov     ax, wptr cs:[CurPartition_Location+0]
-        mov     bx, wptr cs:[CurPartition_Location+2]
-        mov     dx, wptr cs:[CurPartition_Location+4]
-        mov     cx, wptr cs:[CurPartition_Location+6] ; Gets cur. partition location
-        call    LVM_CheckSectorSignature
-        jnc     DIOSLVMS_SevereError                  ; LVM Signature must be there
-
-IFDEF   AUX_DEBUG
-        IF 0
-        pushf
-        pusha
-            ;~ dioatlvm    db 'DriveIO_LVMAdjustToInfoSector',10,0
-            ;~ pushf
-            ;~ pusha
-            ;~ mov     si,offset dioatlvm
-            ;~ call    AuxIO_Print
-            ;~ popa
-            ;~ popf
+        ; Quit with CY if LVM is ignored in SETUP
+        test    byte ptr [CFG_IgnoreLVM], 1     ; ZF=0 means ignore LVM
+        jnz     DIOSLVMS_SevereError            ; Quit if so
+
+        ; Check the validity of the LVM sector, quit with CY if invalid
+        call    LVM_ValidateSector              ; Check signature and CRC
+        jnc     DIOSLVMS_SevereError            ; Quit if not valid
+
+        ; Load the location of the current partition being acted upon.
+        ; Note that this is not the actual LBA of the partition, but the
+        ; sector that has the partition table that contains the entry
+        ; for the partition. In other words, for primary partitions the LBA
+        ; address points to the MBR while for extended partitions it points
+        ; to an EBR. In both cases the LVM sector is located LVM_SPT-1 above.
+        ; Also note that the BIOS CHS values (DH and CX) below are not used,
+        ; because we explicitly use LBA sector loading.
+        mov     ax, wptr cs:[CurPartition_Location+0]   ; LBA lo of MBR/EBR
+        mov     bx, wptr cs:[CurPartition_Location+2]   ; LBA hi of MBR/EBR
+        mov     dx, wptr cs:[CurPartition_Location+4]   ; BIOS disk num & head
+        mov     cx, wptr cs:[CurPartition_Location+6]   ; BIOS cyl & sec
+
+        ; Calculate the entry in the DISKINFO array for this disk,
+        ; and put the LVM_SPT in DI
+        push    bx
+        call    DriveIO_CalcDiskInfoPointer
+        mov     di, [bx+LocDISKINFO_LVM_Secs]
+        pop     bx
+
+        ; If the LVM_SPT is ZERO, no LVM info is present and we quit with CY
+        test    di, di                          ; See if it is 0
+        jz      DIOSLVMS_SevereError            ; Quit if so
+
+        ; Adjust the location to point to the LVM sector
+        add     ax, di      ; Add the LVM sectors-per-track
+        adc     bx, 0       ; Propagate LBA lo overflow to LBA hi
+        sub     ax, 1       ; LVM sector is located one sector below
+        sbb     bx, 0       ; Propagate borrow to LBA hi
+
+IFDEF   AUX_DEBUG
+        IF 1
+        DBG_TEXT_OUT_AUX    'LVMSecSaved'
+        PUSHRF
             call    DEBUG_DumpRegisters
-            call    DEBUG_DumpCHS
-        popa
-        popf
-        ENDIF
-ENDIF
-
-        call    DriveIO_LVMAdjustToInfoSector
-
-IFDEF   AUX_DEBUG
-        IF 0
-        pushf
-        pusha
-            call    DEBUG_DumpRegisters
-            call    DEBUG_DumpCHS
-        popa
-        popf
-        ENDIF
-ENDIF
-
-        mov     si, offset LVMSector
-        call    DriveIO_SaveSector
+            call    AuxIO_DumpSector
+            ;~ call    AuxIO_DumpParagraph
+            ;~ call    AuxIO_TeletypeNL
+        POPRF
+        ENDIF
+ENDIF
+
+        ; Save the LVM sector pointed to by SI
+        mov     di, ds                          ; Segment of that buffer
+        call    DriveIO_WriteSectorLBA          ; Read the LVM sector
+        clc
+        jc      DIOSLVMS_SevereError            ; Quit on error
+
+        ; We're done, indicate success and return
+        clc
+        jmp     DIOSLVMS_Done
+
     DIOSLVMS_SevereError:
+        ; Indicate no valid LVM sector was saved
+        stc
+
+    DIOSLVMS_Done:
         ret
 DriveIO_SaveLVMSector   EndP