adv: fix the handling of the ADV with CBIOS

Fix numerous problems in the way we handled the ADV with CBIOS.  The
EBIOS code was largely correct, but the CBIOS code was just busted.

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

1 files changed, 39 insertions, 25 deletions

diff --git a/core/adv.inc b/core/adv.inc
index c5e8270c..1fe5aca2 100644
--- a/core/adv.inc
+++ b/core/adv.inc
@@ -341,25 +341,6 @@ adv_read_write:
 		mov [ADVOp],ah
 		pushad
 
-		mov dl,[ADVDrive]
-		and dl,dl
-		; Floppies: can't trust INT 13h 08h, we better know
-		; the geometry a priori, which means it better be our
-		; boot device.  Handle that later.
-		; jns .floppy			; Floppy drive... urk
-
-		mov ah,08h			; Get disk parameters
-		int 13h
-		jc .noparm
-		and ah,ah
-		jnz .noparm
-		shr dx,8
-		inc dx
-		mov [ADVHeads],dx
-		and cx,3fh
-		mov [ADVSecPerTrack],cx
-
-.noparm:
 		; Check for EDD
 		mov bx,55AAh
 		mov ah,41h			; EDD existence query
@@ -367,6 +348,10 @@ adv_read_write:
 		int 13h
 		mov si,.cbios
 		jc .noedd
+		cmp bx,0AA55h
+		jne .noedd
+		test cl,1
+		jz .noedd
 		mov si,.ebios
 .noedd:
 
@@ -422,8 +407,38 @@ adv_read_write:
 		push eax
 		push bp
 
-		movzx esi,word [ADVSecPerTrack]
-		movzx edi,word [ADVHeads]
+		mov dl,[ADVDrive]
+		and dl,dl
+		; Floppies: can't trust INT 13h 08h, we better know
+		; the geometry a priori, which means it better be our
+		; boot device...
+		jns .noparm			; Floppy drive... urk
+
+		mov ah,08h			; Get disk parameters
+		int 13h
+		jc .noparm
+		and ah,ah
+		jnz .noparm
+		shr dx,8
+		inc dx
+		movzx edi,dx			; EDI = heads
+		and cx,3fh
+		movzx esi,cx			; ESI = sectors/track
+		jmp .parmok
+
+.noparm:
+		; No CHS info... this better be our boot drive, then
+%if IS_SYSLINUX || IS_EXTLINUX
+		cmp dl,[DriveNumber]
+		jne .cb_overflow		; Fatal error!
+		movzx esi,word [bsSecPerTrack]
+		movzx edi,word [bsHeads]
+%else
+		; Not a disk-based derivative... there is no hope
+		jmp .cb_overflow
+%endif
+
+.parmok:
                 ;
                 ; Dividing by sectors to get (track,sector): we may have
                 ; up to 2^18 tracks, so we need to use 32-bit arithmetric.
@@ -453,7 +468,7 @@ adv_read_write:
                 mov ch,al
                 mov dh,dl
                 mov dl,[ADVDrive]
-                xchg ax,bp              ; Sector to transfer count
+		mov al,01h		; Transfer one sector
                 mov ah,[ADVOp]		; Operation
 
 		mov bp,adv_retries
@@ -467,6 +482,7 @@ adv_read_write:
                 pop bp
                 pop eax
                 pop edx
+		pop si
                 ret
 
 .cb_error:
@@ -481,9 +497,7 @@ adv_read_write:
 ADVSec0		dd 0			; Not specified
 ADVSec1		dd 0			; Not specified
 ADVDrive	db -1			; No ADV defined
+ADVCHSInfo	db -1			; We have CHS info for this drive
 
 		section .bss
-		alignb 4
-ADVSecPerTrack	resw 1
-ADVHeads	resw 1
 ADVOp		resb 1