Date: Thu, 6 Jan 2005 16:00:59 -0500 From: John Baldwin <jhb@FreeBSD.org> To: freebsd-current@FreeBSD.org, peadar@FreeBSD.org Cc: current@FreeBSD.org Subject: Re: Is there a boot sector guru in the house? Message-ID: <200501061600.59601.jhb@FreeBSD.org> In-Reply-To: <34cb7c840501041736570afdfa@mail.gmail.com> References: <41DA2AE0.3020108@elischer.org> <41DAF53A.5000300@elischer.org> <34cb7c840501041736570afdfa@mail.gmail.com>
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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@FreeBSD.org> <>< http://www.FreeBSD.org/~jhb/ "Power Users Use the Power to Serve" = http://www.FreeBSD.org
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