Changeset 184 for trunk/bootcode/airboot.asm

Timestamp:

Nov 7, 2017, 7:12:49 AM (8 years ago)

Author:

Ben Rietbroek

Message:

Added 'CRC_IGNORE' option for debug building [v1.1.1-testing]

The CRC is calculated and inserted in the loader image when AiR-BOOT is
installed. Ignoring the CRC enables manually merging the loader without
using the installer. This is used for debugging in virtual machines,
where it is easy to merge the loader to the disk image of the VM.

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/airboot.asm (modified) (1 diff)

trunk/bootcode/airboot.asm

@@ -827 +827 @@
                 loop    MBR_RealStart_CheckCodeLoop
 
-                ; Verify checksum
+                ; Verify checksum -- EQUAL if OK
                 cmp     MBR_CheckCode, bx
-                ;~ je      MBR_RealStart_CheckSuccess      ; CRC verified
-                jmp      MBR_RealStart_CheckSuccess     ; Ignore CRC
-
+
+                ;
+                ; The CRC is calculated and inserted in the loader image when
+                ; AiR-BOOT is installed. Ignoring the CRC enables manually
+                ; merging the loader without using the installer. This is used
+                ; for debugging in virtual machines, where it is easy to
+                ; merge the loader to the disk image of the VM.
+                ;
+            IFDEF   CRC_IGNORE
+                jmp     MBR_RealStart_CheckSuccess      ; Ignore CRC
+            ELSE
+                je      MBR_RealStart_CheckSuccess      ; Honor CRC -- EQ is OK
+            ENDIF
+
+                ;
                 ; Oops, checksum mismatch -- halt the system
+                ;
                 mov     si, offset TXT_ERROR_Attention
                 call    MBR_Teletype