Changeset 154

Timestamp:

Apr 8, 2017, 12:27:56 AM (8 years ago)

Author:

Ben Rietbroek

Message:

Reimplemented 'LVM_GetDriveLetter' [v1.1.1-testing]

The new method uses SI which points to the IPT entry for the partition.
The IPT entry contains all info needed to load the corresponding LVM
sector. This does away with distinguishing between primary and logical
partitions and also removes ugly and possibly faulty LBA adjustments.

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 @@
 
 
-
-LVM_GetDriveLetter      Proc Near   Uses bx cx dx si di ds es
-        xor     al, al
+;------------------------------------------------------------------------------
+; Get the LVM drive-letter for a partition (if available)
+;------------------------------------------------------------------------------
+; IN    : SI    - Pointer to IPT entry for partition
+; OUT   : AL    - LVM drive-letter
+;       : SI    - Pointer to LVM entry in loaded LVM record
+;       : CF=1  - No valid LVM sector found, AL not valid
+; NOTE  : Besides the drive-letter, AL can be 0 (LVM hidden) or '*' (LVM auto)
+;------------------------------------------------------------------------------
+LVM_GetDriveLetter      Proc Near   Uses bx cx dx di
+
+IFDEF   AUX_DEBUG
+        IF 0
+        DBG_TEXT_OUT_AUX    'LVM_GetDriveLetter:'
+        PUSHRF
+            call    DEBUG_DumpRegisters
+            ;~ call    AuxIO_DumpParagraph
+            ;~ call    AuxIO_TeletypeNL
+        POPRF
+        ENDIF
+ENDIF
+
+        ; Save IPT pointer
+        mov     di, si
+
+        ; Get the LBA addresses of the MBR or EBR from the IPT entry
+        mov     dl, [si+LocIPT_Drive]                   ; BIOS disk number
+        mov     ax, [si+LocIPT_AbsolutePartTable+00h]   ; LBA lo MBR/EBR
+        mov     bx, [si+LocIPT_AbsolutePartTable+02h]   ; LBA hi MBR/EBR
+
+        ; Try to load the corresponding LVM sector
+        mov     si, offset [LVMSector]                  ; Pointer to buffer
+        call    DriveIO_LoadLVMSectorXBR                ; Try to load LVM sector
+        jc      LVM_GetDriveLetter_no_lvm               ; No success
+
+        ; Recall IPT pointer
+        mov     si, di
+
+        ; Locate the LVM entry for the partition
+        mov     ax, [si+LocIPT_AbsoluteBegin+00h]       ; LBA lo of partition
+        mov     dx, [si+LocIPT_AbsoluteBegin+02h]       ; LBA hi of partition
+        mov     si, offset [LVMSector]                  ; Loaded LVM sector
+        call    LVM_SearchForPartition                  ; Locate entry
+        jnc     LVM_GetDriveLetter_no_lvm               ; Entry not found
+
+        ; Get the LVM drive-letter
+        mov     al, [si+LocLVM_VolumeLetter]            ; Can be 0,'*',letter
+
+        ; We're done, indicate success and return
         clc
+        jmp     LVM_GetDriveLetter_done
+
+    LVM_GetDriveLetter_no_lvm:
+        ; Indicate no LVM drive-letter found
+        xor     ax, ax
+        mov     si, ax
+        stc
+
+    LVM_GetDriveLetter_done:
+
+IFDEF   AUX_DEBUG
+        IF 0
+        DBG_TEXT_OUT_AUX    'lgdl_lvmsec'
+        PUSHRF
+            call    DEBUG_DumpRegisters
+            mov     si, offset [LVMSector]
+            call    AuxIO_DumpSector
+            ;~ call    AuxIO_DumpParagraph
+            ;~ call    AuxIO_TeletypeNL
+        POPRF
+        ENDIF
+ENDIF
+
         ret
 LVM_GetDriveLetter      EndP