linux-kernel - Re: x86 setup code rewrite in C

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Message-ID: <526073.18540.qm@web26902.mail.ukl.yahoo.com>
Date:	Fri, 13 Jul 2007 16:25:16 +0200 (CEST)
From:	Etienne Lorrain <etienne_lorrain@...oo.fr>
To:	linux-kernel@...r.kernel.org
Subject: Re: x86 setup code rewrite in C - revised

On Thu, 12 Jul 2007, Linus Torvalds wrote:
> On Thu, 12 Jul 2007, Andrew Morton wrote:
> > 
> > This code has been in -mm since 11 May, as git-newsetup.patch.  It has
> > caused (for what it is) astonishingly few problems.  Maybe a couple of
> > build glitches and one runtime failure, all quickly fixed.
> > 
> > I'd say it's ready.
> 
> Ok. That makes it easy. I'll just merge it.
> 
> 		Linus

 Have fun, this code:
 - do not open the fast A20 gate before checking if the slow A20 gate is open or closed.
 - 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()
 - 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).
 - 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)
 - Has a "dn" for outl() which sliped in instead of "dN"
 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;
}

  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).

  Etienne.
http://gujin.org

I like that message in this context...
   http://marc.info/?l=linux-kernel&m=117077712515509&w=4


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