linux-kernel - Re: [PATCH 02/10] x86: add support for relative CALL and JMP in alternatives

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Message-ID: <ff13bc9a1002181538q7ccc1381x32a2f25bfb6d56cc@mail.gmail.com>
Date:	Fri, 19 Feb 2010 00:38:48 +0100
From:	Luca Barbieri <luca@...a-barbieri.com>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	mingo@...e.hu, a.p.zijlstra@...llo.nl, akpm@...ux-foundation.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 02/10] x86: add support for relative CALL and JMP in 
	alternatives

> The existing instruction parser is only present if KPROBES is configured
> in... this patch would make it obligatory.  Your patch doesn't reflect
> that.  Furthermore, it is ~16K of code and data which probably will make
> embedded people unhappy... although perhaps isn't out of line.
Didn't notice that.

> A good question, though, is if we actually need support for JMP or CALL
> as anything but the first instruction (usually the *only* instruction),
> which would make it a lot easier...

Probably not.
I think an even better option is to create a CALL if replacementlen is 0xff.
This would save some space for each callsite and make it clear we only
support this usage.
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