Changeset 560 in xtideuniversalbios for trunk/XTIDE_Universal_BIOS/Src/Handlers/Int13hBiosInit.asm

Timestamp:

Jul 3, 2013, 6:56:05 PM (11 years ago)

Author:

aitotat@…

google:author:

aitotat@gmail.com

Message:

Changes to XTIDE Universal BIOS:

• Very late init handler is now in MODULE_VERY_LATE_INITIALIZATION

File:

• trunk/XTIDE_Universal_BIOS/Src/Handlers/Int13hBiosInit.asm (modified) (1 diff)

trunk/XTIDE_Universal_BIOS/Src/Handlers/Int13hBiosInit.asm

@@ -22 +22 @@
 SECTION .text
 
-TEMPORARY_VECTOR_FOR_SYSTEM_INT13h      EQU     21h ; MS-DOS
+TEMPORARY_VECTOR_FOR_SYSTEM_INT13h      EQU     20h ; MS-DOS so BIOSes most likely do not use this
 
 
+;--------------------------------------------------------------------
+; Int 13h software interrupt handler.
+; This handler captures boot sector read from foreign drive when our
+; INT 19h is not called. This way we can for XTIDE Universal BIOS
+; initialization even without INT 19h being called.
+;
+; Int13hBiosInit_Handler
+;   Parameters:
+;       AH:     Bios function
+;               READ_SECTORS_INTO_MEMORY will initialize XTIDE Universal BIOS
+;--------------------------------------------------------------------
 Int13hBiosInit_Handler:
+    ; Initialize XTIDE Universal BIOS only if Int13hBiosInit_Handler is still at
+    ; vector 13h. Otherwise some other BIOS has hooked us and our very late
+    ; initialization is not possible.
+    push    ds
+    push    ax
+    LOAD_BDA_SEGMENT_TO ds, ax
+    pop     ax
+    cmp     WORD [BIOS_DISK_INTERRUPT_13h*4], Int13hBiosInit_Handler
+    pop     ds
+    jne     SHORT .VeryLateInitFailed   ; XTIDE Universal BIOS does not work
+
     ; Ignore all but read command (assumed to read boot sector)
     cmp     ah, READ_SECTORS_INTO_MEMORY
-    jne     SHORT .MainBiosStillInInitializationMode
+    je      SHORT Int19h_BootLoaderHandler
 
-    LOAD_BDA_SEGMENT_TO ds, ax
-
-    ; Now install our handler and call 19h since non-standard motherboard BIOS did not
-    ; do that or our INT 19h hander was replaced by other BIOS.
-    mov     WORD [BIOS_BOOT_LOADER_INTERRUPT_19h*4], Int19h_BootLoaderHandler
-    mov     [BIOS_BOOT_LOADER_INTERRUPT_19h*4+2], cs
-    int     BIOS_BOOT_LOADER_INTERRUPT_19h  ; Does not return
-
-    ; Main BIOS might reset floppy drives etc. so let's wait longer
-    ; before installing our INT 19h handler.
-.MainBiosStillInInitializationMode:
+    ; Call system INT 13h since not trying to read boot sector
     int     TEMPORARY_VECTOR_FOR_SYSTEM_INT13h
     retf    2
 
-
-;--------------------------------------------------------------------
-; Int13hBiosInit_RestoreSystemHandler
-;   Parameters:
-;       Nothing
-;   Returns:
-;       Nothing
-;   Corrupts registers:
-;       AX, DS, ES
-;--------------------------------------------------------------------
-Int13hBiosInit_RestoreSystemHandler:
-    LOAD_BDA_SEGMENT_TO ds, ax
-
-    ; Is our very late init handler in place
-    cmp     WORD [BIOS_DISK_INTERRUPT_13h*4], Int13hBiosInit_Handler
-    jne     SHORT .SystemHandlerAlreadyInPlace
-
-    les     ax, [TEMPORARY_VECTOR_FOR_SYSTEM_INT13h*4]
-    mov     [BIOS_DISK_INTERRUPT_13h*4], ax
-    mov     [BIOS_DISK_INTERRUPT_13h*4+2], es
-.SystemHandlerAlreadyInPlace:
-    ret
+.VeryLateInitFailed:
+    mov     ah, RET_HD_INVALID
+    stc
+    retf    2