linux-kernel - Re: [PATCH 2/2] x86 : relocate uninitialized variable in init DATA section into init BSS section

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Message-ID: <47BDC43F.4070106@zytor.com>
Date:	Thu, 21 Feb 2008 10:34:39 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Ingo Molnar <mingo@...e.hu>
CC:	"Huang, Ying" <ying.huang@...el.com>,
	Ingo Molnar <mingo@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>, Andi Kleen <ak@...e.de>,
	Ian Campbell <ijc@...lion.org.uk>,
	Matt Mackall <mpm@...enic.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] x86 : relocate uninitialized variable in init DATA
 section into init BSS section

Ingo Molnar wrote:
> 
> well, that's bad. We'd silently ignore the " = 1" and boot up with that 
> value at 0, right? At minimum we need some really prominent build-time 
> _errors_ (i.e. aborted builds) if this ever happens. But ideally, 
> shouldnt this whole thing be done at link time? Couldnt the linker sort 
> the variables that are zero initialized into the right section, and move 
> this constant maintenance pressure off the programmer's shoulder?
> 

Not the linker (unless each variable is put in its own section)... the 
compiler could (should!) do it... unfortunately gcc failed to provide a 
way to specify rodata, data and bss sections for a single data item (on 
the assumption that if you specified a section, you already knew were it 
should be going.)

What we really need is a new gcc extension:

__attribute__((sections("data", "rodata", "bss")))

... where gcc stuffs it into the appropriate section depending on where 
it belongs, just as it does with undecorated data items.

	-hpa
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