linux-kernel - Re: [patch 3/8] Immediate Values

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Date:	Fri, 7 Sep 2007 08:49:08 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
Cc:	akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
	Adrian Bunk <bunk@...sta.de>, Andi Kleen <andi@...stfloor.org>,
	Alexey Dobriyan <adobriyan@...il.com>,
	Christoph Hellwig <hch@...radead.org>
Subject: Re: [patch 3/8] Immediate Values - Kconfig menu in EMBEDDED

> +config IMMEDIATE
> +	default y if !DISABLE_IMMEDIATE

It's still unclear to me why DISABLE_IMMEDIATE is needed. It would
be better to make it just the default.

> +config DISABLE_IMMEDIATE
> +	default y if EMBEDDED
> +	bool "Disable immediate values" if EMBEDDED
> +	depends on X86_32 || PPC || PPC64
> +	help
> +	  Disable code patching based immediate values for embedded systems. It
> +	  consumes slightly more memory and requires to modify the instruction
> +	  stream each time a variable is updated. 

>         Should really be disabled for
> +	  embedded systems with read-only text.

There are no such on x86 at least  And for other architectures like
PPC it would be better to have a high level CONFIG_READ_ONLY_TEXT
then that does the necessary changes internally.  But I'm not sure it's even 
supporting r/o text.

-Andi
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