linux-kernel - Re: [PATCH 1/6] x86/efi: PFN_ALIGN() _text and

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Message-ID: <20151124105556.GA2460@codeblueprint.co.uk>
Date:	Tue, 24 Nov 2015 10:55:56 +0000
From:	Matt Fleming <matt@...eblueprint.co.uk>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	"H . Peter Anvin" <hpa@...or.com>, Toshi Kani <toshi.kani@...com>,
	linux-kernel@...r.kernel.org, linux-efi@...r.kernel.org,
	Borislav Petkov <bp@...en8.de>,
	Sai Praneeth Prakhya <sai.praneeth.prakhya@...el.com>,
	stable@...r.kernel.org, Dave Hansen <dave.hansen@...el.com>
Subject: Re: [PATCH 1/6] x86/efi: PFN_ALIGN() _text and _end when calculating
 number of pages

On Tue, 24 Nov, at 09:23:23AM, Ingo Molnar wrote:
> 
> Didn't we want to do the _end alignment linker script fix instead?

I think we should do both. This patch is tagged for stable because it
fixes a bug in the existing code. It's obvious and it's explicit and
it's much easier to know when someone might want to backport it.

Changing the linker script which indirectly fixes the above bug is a
much more subtle solution, with much larger potential for fallout
because it affects multiple chunks of kernel code.

> Alignment assumptions are easy to make when symbols are well aligned typically (as 
> in this case), so we should guarantee the alignment property instead of 
> complicating the code.

I don't agree that sprinkling PFN_ALIGN() complicates the code, it's a
minimal change with a well known kernel idiom. But yes, aligning these
symbols in the linker script is generally a good idea.

The two patches are worthwhile, for different reasons; let's do both.
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