linux-kernel - Re: [PATCH] pop previous section in alternative.c

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Message-ID: <47FE3C0C.4090101@zytor.com>
Date:	Thu, 10 Apr 2008 09:10:52 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
CC:	Andi Kleen <andi@...stfloor.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Andy Whitcroft <apw@...dowen.org>,
	LKML <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <peterz@...radead.org>,
	akpm@...ux-foundation.org, Rusty Russell <rusty@...tcorp.com.au>,
	Glauber de Oliveira Costa <gcosta@...hat.com>,
	Jan Beulich <jbeulich@...ell.com>,
	Thomas Gleixner <tglx@...utronix.de>, pinskia@....gnu.org
Subject: Re: [PATCH] pop previous section in alternative.c

Linus Torvalds wrote:
> 
> The thing is, we'd be much better off with some sanity checking in the 
> assembler.
> 
> Which is likely not going to happen - oh well.
> 
> In particular, the assembler should see patterns like
> 
> 	.size function, .-function
> 
> and it should be _trivially_ able to check that "." and "function" are in 
> the same section, and warn if they aren't. Because I don't see how it 
> could ever be valid to have sizes that cross section boundaries (it's a 
> totally nonsensical concept).
> 
> But it doesn't. Oh, well.
> 

Wow.  That is utterly braindamaged on the part of gas.

> But maybe we can see it in the resulting object file somehow, and do the 
> check there (the same way we do the init-section analysis). I assume the 
> .size directive writes some debug info or similar, and we can create a big 
> warning when a size is unexpectedly huge and crosses section size 
> boundaries?

I just tried it, and it output the difference across the sections, 
without any consideration that the base was different.  Didn't know one 
could write an assembler that dumb.

	-hpa

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