Is there a boot sector guru in the house?
John Baldwin
jhb at FreeBSD.org
Thu Jan 6 13:21:21 PST 2005
On Tuesday 04 January 2005 08:36 pm, Peter Edwards wrote:
> I don't have a box I can test this on, but this looks like a definite
> candidate to get
> 3 more bytes:
>
> --- boot0.S 24 Nov 2004 15:39:04 -0000 1.12
> +++ boot0.S 5 Jan 2005 01:27:31 -0000
> @@ -314,8 +314,7 @@
> cmpw $MAGIC,0x1fe(%bx) # Bootable?
> jne main.10 # No
> pushw %si # Save
> - movw $crlf,%si # Leave some
> - callw puts # space
> + callw putn # Leave space
> popw %si # Restore
> jmp *%bx # Invoke bootstrap
>
> If my arithmetic is correct, that leaves us wanting one more byte.
> I don't get the save/restore of %si at the end, and judging by the
> comment, someone else didn't either. It could be of some use to the
> chained loader, but our boot1.S doesn't do anything with it.
This actually changes behavior I think (the earlier code outputs two blank
lines, the second only one). However, the push and pop of %si probably can
go. I think the save/restore there is just pedantic save/restore around
puts.
--
John Baldwin <jhb at FreeBSD.org> <>< http://www.FreeBSD.org/~jhb/
"Power Users Use the Power to Serve" = http://www.FreeBSD.org
More information about the freebsd-current
mailing list