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>

diff --git a/core/adv.inc b/core/adv.inc
index c5e8270..1fe5aca 100644 (file)
--- 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