diskstart: fix CHS mode, reinstate cyl 1023 check

Fix loading in CHS mode; we were missing a popad.  Also reinstate the
check for exceeding cylinder 1023.

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

diff --git a/core/diskstart.inc b/core/diskstart.inc
index 40330dd..4f15ad2 100644 (file)
--- a/core/diskstart.inc
+++ b/core/diskstart.inc
@@ -159,12 +159,13 @@ floppy:
                fs rep movsw            ; Faster to move words
                mov cl,[bsSecPerTrack]  ; Patch the sector count
                mov [di-76+8],cl
-               int 13h                 ; Some BIOSes need this
 
-               push cx                 ; Partition offset == 0
-               push cx
-               push cx
-               push cx
+               push ax                 ; Partition offset == 0
+               push ax
+               push ax
+               push ax
+
+               int 13h                 ; Some BIOSes need this
                jmp short not_harddisk
 ;
 ; The drive number and possibly partition information was passed to us
@@ -326,9 +327,8 @@ getonesec_cbios:
                ; eax = track #
                div edi                 ; Convert track to head/cyl
 
-               ; We should test this, but it doesn't fit...
-               ; cmp eax,1023
-               ; ja .error
+               cmp eax,1023            ; Outside the CHS range?
+               ja kaboom
 
                ;
                ; Now we have AX = cyl, DX = head, CX = sector (0-based),
@@ -343,11 +343,11 @@ getonesec_cbios:
                mov dh,dl
                mov ax,0201h            ; Read one sector
                call xint13
+               popad
                jc .error
                ret
 
 .error:
-               popad
                loop .retry
                ; Fall through to disk_error
 
@@ -699,9 +699,8 @@ getlinsec_cbios:
                ; eax = track #
                div edi                 ; Convert track to head/cyl
 
-               ; We should test this, but it doesn't fit...
-               ; cmp eax,1023
-               ; ja .error
+               cmp eax,1023            ; Outside the CHS range?
+               ja kaboom
 
                ;
                ; Now we have AX = cyl, DX = head, CX = sector (0-based),