memdisk: don't set CX:DX for INT 13h AH=15h for floppies

Win98SE DOS apparently hangs if INT 13h, AH=15h returns the capacity
in CX:DX for floppies... *unless* EDD is enabled.  Confused yet?

This patch also adds some more tracing framework.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>

diff --git a/memdisk/memdisk.inc b/memdisk/memdisk.inc
index c7eb9f1..f4cb0fe 100644 (file)
--- a/memdisk/memdisk.inc
+++ b/memdisk/memdisk.inc
@@ -27,11 +27,47 @@
        call debug_tracer
        db %1
 %endmacro
+%macro WRITEHEX2 0-1 al
+%ifnidni %1,al
+       push ax
+       mov al,%1
+       call writehex2
+       pop ax
+%else
+       call writehex2
+%endif
+%endmacro
+%macro WRITEHEX4 0-1 ax
+%ifnidni %1,ax
+       push ax
+       mov ax,%1
+       call writehex4
+       pop ax
+%else
+       call writehex4
+%endif
+%endmacro
+%macro WRITEHEX8 0-1 eax
+%ifnidni %1,eax
+       push eax
+       mov eax,%1
+       call writehex8
+       pop eax
+%else
+       call writehex8
+%endif
+%endmacro
 
 %else  ; DEBUG_TRACERS
 
 %macro TRACER  1
 %endmacro
+%macro WRITEHEX2 0-1
+%endmacro
+%macro WRITEHEX4 0-1
+%endmacro
+%macro WRITEHEX8 0-1
+%endmacro
 
 %endif ; DEBUG_TRACERS
 
@@ -90,7 +126,7 @@ Pointers:    dw Int13Start
 IretPtr                equ Int13Start.iret
 Int13Start:
                cmp word [cs:Recursive],0
-               jne jmp_oldint13
+               jne recursive
 
                ; Swap stack
                mov [cs:Stack],esp
@@ -113,7 +149,15 @@ Int13Start:
                jb .nomatch             ; Drive < Our drive
                dec dl                  ; Drive > Our drive, adjust drive #
 .nomatch:
+%ifdef DEBUG_TRACERS
+               TRACER '!'
+               WRITEHEX2 dl
+               TRACER ','
+               mov ax,[cs:SavedAX]
+               WRITEHEX4
+%else
                mov ax,[cs:SavedAX]
+%endif
                inc word [cs:Recursive]
                pushf
                call far [cs:OldInt13]
@@ -141,6 +185,8 @@ Int13Start:
                lss esp,[cs:Stack]
 .iret:         iret
 
+recursive:
+               TRACER '@'
 jmp_oldint13:
                jmp far [cs:OldInt13]
 
@@ -154,6 +200,7 @@ our_drive:
                pushad
                mov bp,sp               ; Point BP to the entry stack frame
                TRACER 'F'
+               WRITEHEX4
                ; Note: AX == P_AX here
                cmp ah,Int13FuncsCnt-1
                ja Invalid_jump
@@ -227,13 +274,15 @@ GetDriveType:
                test byte [DriveNo],80h
                mov bl,02h              ; Type 02h = floppy with changeline
                jz .floppy
-               ; Hard disks only...
+               ; Hard disks only!  DO NOT set CX:DX for floppies...
+               ; it apparently causes Win98SE DOS to go into an loop
+               ; resetting the drive over and over.  Sigh.
                inc bx                  ; Type = 03h
-.floppy:
                mov dx,[DiskSize]       ; Return the disk size in sectors
                mov P_DX,dx
                mov cx,[DiskSize+2]
                mov P_CX,cx
+.floppy:
                mov P_AH,bl             ; 02h floppy, 03h hard disk
                pop ax                  ; Drop return address
                xor ax,ax               ; Success...

diff --git a/memdisk/setup.c b/memdisk/setup.c
index 013f3df..caee377 100644 (file)
--- a/memdisk/setup.c
+++ b/memdisk/setup.c
@@ -90,7 +90,7 @@ struct edd_dpt {
     uint64_t devpath[2];       /* Device path (double QuadWord!) */
     uint8_t  res3;             /* Reserved */
     uint8_t  chksum;           /* DPI checksum */
-};
+} __attribute__((packed));
 
 struct patch_area {
     uint32_t diskbuf;
@@ -131,7 +131,7 @@ struct patch_area {
 
     dpt_t dpt;
     struct edd_dpt edd_dpt;
-};
+} __attribute__((packed));
 
 /* Access to high memory */