[patch] arch/i386/setup.S bug

[Tigran Aivazian]

Hi Linus and the world,

Please glance over this piece in the current setup.S

bad_sig:
        movw    %cs, %ax                        # SETUPSEG
        subw    $DELTA_INITSEG, %ax             # INITSEG
        movw    %ax, %ds
        xorb    %bh, %bh
        movb    (497), %bl                      # get setup sect from
bootsect
        subw    $4, %bx                         # LILO loads 4 sectors of
setup
        shlw    $7, %bx                         # convert to dwords
(1sect=2^7 dwords)
        movw    %bx, %cx
        shrw    $2, %bx                         # convert to segment
        addw    $SYSSEG, %bx
        movw    %bx, %cs:start_sys_seg
# Move rest of setup code/data to here
        movw    $2048, %di                      # four sectors loaded by
LILO
        subw    %si, %si
        movw    %cs, %ax                        # aka SETUPSEG
        movw    %ax, %es
        movw    $SYSSEG, %ax
        movw    %ax, %ds
        rep
        movsw

a long time ago (when it was still written in as86) I converted all movsw
to movsd and (the part, relevant to the above, of ) my patch looked like
this:

@@ -188,9 +188,9 @@
        xor     bh,bh
        mov     bl,[497]        ! get setup sects from boot sector
        sub     bx,#4           ! LILO loads 4 sectors of setup
-       shl     bx,#8           ! convert to words
+       shl     bx,#7           ! convert to dwords (1sect=2^7 dwords)
        mov     cx,bx
-       shr     bx,#3           ! convert to segment
+       shr     bx,#2           ! convert to segment
        add     bx,#SYSSEG
        seg cs
        mov     start_sys_seg,bx
@@ -203,7 +203,7 @@
        mov     ax,#SYSSEG
        mov     ds,ax
        rep
-       movsw
+       movsd

        mov     ax,cs           ! aka #SETUPSEG
        mov     ds,ax

see that 8 becoming 7 and 3 becoming 2 above? Now, the current version
uses movsw and yet we still have 7 and 2 instead of 8 and 3. This is just
a "surface look" which makes me think it is obviously incorrect. 

Anyway, I think it is wrong and here is the patch to fix it:

http://www.ocston.org/~tigran/patches/setup-2.3.36-p6.patch

Thanks,
------
Tigran A. Aivazian           | http://www.sco.com
Escalations Research Group   | tel: [phone]
Santa Cruz Operation Ltd     | http://www.ocston.org/~tigran