From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1762971AbXGMRe0 (ORCPT ); Fri, 13 Jul 2007 13:34:26 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756520AbXGMReT (ORCPT ); Fri, 13 Jul 2007 13:34:19 -0400 Received: from terminus.zytor.com ([198.137.202.10]:44297 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752327AbXGMReS (ORCPT ); Fri, 13 Jul 2007 13:34:18 -0400 X-Greylist: delayed 2508 seconds by postgrey-1.27 at vger.kernel.org; Fri, 13 Jul 2007 13:34:18 EDT Message-ID: <4697ADAC.4070009@zytor.com> Date: Fri, 13 Jul 2007 09:51:56 -0700 From: "H. Peter Anvin" User-Agent: Thunderbird 2.0.0.0 (X11/20070419) MIME-Version: 1.0 To: Chuck Ebbert CC: Etienne Lorrain , linux-kernel@vger.kernel.org, Linus Torvalds Subject: Re: x86 setup code rewrite in C - revised References: <526073.18540.qm@web26902.mail.ukl.yahoo.com> <4697A9E9.3090502@redhat.com> In-Reply-To: <4697A9E9.3090502@redhat.com> X-Enigmail-Version: 0.95.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Chuck Ebbert wrote: >> Have fun, this code: >> - do not open the fast A20 gate before checking if the slow A20 gate is open or closed. As does the current code; this is highly intentional behaviour since there are machines (in particular a whole series of machines made by Olivetti) which lock up if you do it differently. >> - uses in asm("") inputs which may or may not be set by the compiler in the stack, >> after modifying the stack pointer in the asm block: at least has_eflag() Point. "g" should be "ri". I will send a patch. >> - The VGA recalc has the same bug as the assembly version where a VGA write protected >> register is written (Overflow register) without setting the enable bit (see VGA docs). OK, that would be a bug ported directly from the assembly version. The fact that the bug can be seen now is part of why I did this work. Please feel free to submit a patch. >> - Does not save and restore %ds when printing a char on the screen (%ds is destroyed >> only when the content of the screen scroll - only for some video cards) %ds? Aren't you confusing it with the old bug which would destroy %bp? If you have any references to %ds being destroyed I would be very surprised. I can guarantee that very little if any assembly code I've ever seen that deals with INT 10h -- and I've seen a lot of it -- guards against %ds being randomly trashed. However, the trashing of %bp is a well-known bug (although only for machines older than the ones that can run Linux) -- the Interrupt List has: BUGS: some implementations (including the original IBM PC) have a bug which destroys BP >> - Has a "dn" for outl() which sliped in instead of "dN" That's a bug, although currently nonmanifest -- there are no users of outl() at the present. I will send a patch. >> and probably few other problems - just seen those by reading the patches (the asm("") >> are inlined in the C code - I find it more difficult to check). >> >> Also, I do not know if "m" is right in here: >> static inline u8 rdfs8(addr_t addr) >> { >> u8 v; >> asm("movb %%fs:%1,%0" : "=r" (v) : "m" (*(u8 *)addr)); >> return v; >> } The "m" is correct right there. >> I may repeat me, but to find these kind of problems, it is very nice to have an ELF >> file to do a readelf/objdump -D -m i8086 (even after final link). There is such a file (arch/i386/boot/setup.elf) which is retained, for exactly this reason. -hpa