Changeset 153

Timestamp:

Apr 8, 2017, 12:27:55 AM (8 years ago)

Author:

Ben Rietbroek

Message:

Prepared 'LVM_GetDriveLetter' for reimplementation [v1.1.1-testing]

This is one ugly mthrfscker of which we won't even record the diff with
its reimplementation.

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/special/lvm.asm (modified) (1 diff)

trunk/bootcode/special/lvm.asm

@@ -220 +220 @@
 
 
-; Gets a drive-letter from the LVM-info of a partition. (if it exists)
-;        In: BX:CX - LBA starting sector of partition to be searched
-;            DL = Physical Disk in BIOS notation. (80h+)
-;       Out: CY=1 if LVM-info found, 0 if no LVM-info.
-;            AL - drive-letter from LVM-info or zero if no drive-letter
-;            assigned or no LVM-info.
+
 LVM_GetDriveLetter      Proc Near   Uses bx cx dx si di ds es
-
-IFDEF   AUX_DEBUG
-        IF 0
-        DBG_TEXT_OUT_AUX    'LVM_GetDriveLetter:'
-        PUSHRF
-            ;~ call    DEBUG_DumpRegisters
-            ;~ call    AuxIO_DumpParagraph
-            ;~ call    AuxIO_TeletypeNL
-        POPRF
-        ENDIF
-ENDIF
-
-
-
-        ; For primary partitions this information is stored in the last
-        ; sector of track0; for all four partition entries in case they
-        ; they are all primary ones.
-        ;
-        ; LVM DLAT info for logical partitions is stored in the sector
-        ; preceding the start of the partition.
-        ;
-        ; Because the LVM info of a logical partition is the easiest to find,
-        ; we do that first. The LVM info for primary partitions is located
-        ; dependent on the geometry in use, so we use a special locater
-        ; call for that. Also, since the LVM info for primaries contains
-        ; info on all 4 entries, we need the partition index to obtain the
-        ; correct drive-letter.
-        ;
-
-        ; See if this is a primary partition
-        ; CY will be set if it is and AL will contain the 0-based
-        ; index in the P-table.
-        ; If it's a logical partition, CY will be clear and AL
-        ; will be set to 0ffh indicating an invalid index.
-        call    PART_IsPrimaryPartition
-IF 0
-                pushf
-                pusha
-                call    VideoIO_PrintHexWord
-                popa
-                popf
-ENDIF
-        mov     al,0
-        rcl     al,1        ; CY if primary
-        mov     dh,al       ; Save PRI or LOG
-
-        ; Save PRI/LOG indicator for later use
-        push    dx
-
-        ; Load *possible* LVM sector
-        ; This load is only valid if the partition is logical, in which case
-        ; the LVM sector is below the start of the partition.
-        ; If primary, the LVM sector is at a location that
-        ; DriveIO_LoadMasterLVMSector will find out.
-
-        ; Push LBA address
-        push    bx
-        push    cx
-
-        ; Adjust for logical LVM-sector
-        sub     cx,1
-        sbb     bx,0
-
-        ; Load the LVM sector
-        push    si
-        push    di
-        mov     si,offset [LVMSector]
-        mov     di,ds
-        mov     ax, cx                      ; LBA low is now in AX
-        call    DriveIO_ReadSectorLBA
-        pop     di
-        pop     si
-
-        ; Restore LBA address
-        pop     cx
-        pop     bx
-
-        ; Restore PRI/LOG partition indicator in DH
-        pop     dx
-
-        ; Test PRI or not
-        test    dh,dh
-        ; It's not a PRI so we can use the previously loaded LVM sector
-        jz      LVM_GetDriveLetter_is_not_pri
-
-        ;
-        ; It's a PRI so we use the special locator function.
-        ; This locator takes care of extended OS/2 geometry should that be used
-        ;
-IF 0
-                ; DH=0 or 1, DL=disk (8?h)
-                pushf
-                pusha
-                mov     ax, dx
-                call    VideoIO_PrintHexWord
-                mov     al,'-'
-                call    VideoIO_PrintSingleChar
-                popa
-                popf
-ENDIF
-        ; THIS ONE FAULTERS WHEN DISKS > 1
-        call    DriveIO_LoadMasterLVMSector
-
-IF 0
-                ; INVALID LVM SECTOR !!
-                pushf
-                pusha
-                mov     ax,0000h
-                rcl     al,1
-                call    VideoIO_PrintHexWord        ; LVMSector
-                mov     al,'-'
-                call    VideoIO_PrintSingleChar
-                mov     si, offset [LVMSector]
-                mov     ax, si
-                call    VideoIO_PrintHexWord        ; LVMSector
-                lodsw
-                call    VideoIO_PrintHexWord        ; sig
-                lodsw
-                call    VideoIO_PrintHexWord        ; sig
-                mov     al,'-'
-                call    VideoIO_PrintSingleChar
-                popa
-                popf
-ENDIF
-
-    LVM_GetDriveLetter_is_not_pri:
-
-
-        ;
-        ; At this stage the LVM-info sector has been loaded at [LVMSector].
-        ; From here we look for an LVM entry for the partition.
-        ; If one is found, based on it's LBA-start, it's driveletter is used
-        ; in case byte 25h in the BPB is zero.
-        ;
-
-
-        ; Search for the partition in the LVM info.
-        ; If found, CY is set and SI points to LVM entry.
-        push    si
-        mov     ax,cx
-        mov     dx,bx                   ; DL DESTROYED
-        mov     si,offset [LVMSector]
-        call    LVM_SearchForPartition
-
-IF 0
-                pushf
-                pusha
-                mov     ax, 0000h
-                rcl     al, 1
-                call    VideoIO_PrintHexWord
-                mov     ax, si
-                call    VideoIO_PrintHexWord
-                popa
-                popf
-ENDIF
-
-IFDEF   AUX_DEBUG
-        IF 0
-        DBG_TEXT_OUT_AUX    'LVM_GetDriveLetter:'
-        PUSHRF
-            call    DEBUG_DumpRegisters
-            call    AuxIO_DumpParagraph
-            call    AuxIO_TeletypeNL
-        POPRF
-        ENDIF
-ENDIF
-
-        mov     bx,si   ; BX now points to LVM entry
-        mov     dx,0
-        pop     si
-
-        mov     al,0    ; Setup null driveletter
-        ; Oops, no valid LVM record was used so we have a null driveletter.
-        jnc     LVM_GetDriveLetter_null_lvm_dl
-
-        ;
-        ; At this point BX points to the LVM-entry related to the
-        ; partition, whether it was a logical or a primary one.
-        ;
-        mov     al,[bx+LocLVM_VolumeLetter]
-        ; Test for zero dtive-letter.
-        test    al,al
-        ; Preset CY in case drive-letter is zero.
+        xor     al, al
         clc
-        jz      LVM_GetDriveLetter_null_lvm_dl
-
-        ; We have a non-zero drive-letter, so set CY.
-        stc
-
-    LVM_GetDriveLetter_null_lvm_dl:
         ret
 LVM_GetDriveLetter      EndP