linux-ext4 - Re: [PATCH 1/1] x86: fix text

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Message-Id: <20080425.140207.55069805.davem@davemloft.net>
Date:	Fri, 25 Apr 2008 14:02:07 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	hpa@...or.com
Cc:	mathieu.desnoyers@...ymtl.ca, andi@...stfloor.org,
	torvalds@...ux-foundation.org, mingo@...e.hu, jirislaby@...il.com,
	zdenek.kabelac@...il.com, rjw@...k.pl, paulmck@...ux.vnet.ibm.com,
	akpm@...ux-foundation.org, linux-ext4@...r.kernel.org,
	herbert@...dor.apana.org.au, penberg@...helsinki.fi,
	clameter@....com, linux-kernel@...r.kernel.org,
	pageexec@...email.hu, jeremy@...p.org
Subject: Re: [PATCH 1/1] x86: fix text_poke

From: "H. Peter Anvin" <hpa@...or.com>
Date: Fri, 25 Apr 2008 13:41:00 -0700

> Yes, that should work.  It's still ugly, and I have to say I find the 
> complexity rather distasteful.  I am willing to be convinced it's worth 
> it, but I would really like to see hard numbers.

This stuff would have been a lot easier if it just worked with
normal relocations generated by the assembler, and that would
work in such a straightforward way on EVERY architecture.

The immediate instance generators could just use macros that
architectures define, which are given a range of legal values for the
immediate, and the macro emits the inline asm sequence that can
support an immediate value of that range.

Then we do a half-link of the kernel, collect the unresolved
relocations from generated by the immediate macros into a table which
gets linked into the kernel, then resolve them in the final link all
to zero or some defined initial value.

Then it's just a matter of running through the relocation handling
we already have for module loading when changing an immediate
value.

None of this crazy instruction parsing and branch following crap.
I can't believe we're seriously considering this crud. :-/
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