linux-kernel - Re: [PATCH 2/2] kallsyms: handle special absolute symbols

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Message-ID: <8761nqzo4z.fsf@rustcorp.com.au>
Date:	Fri, 07 Mar 2014 13:55:00 +1030
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	Kees Cook <keescook@...omium.org>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Andrew Honig <ahonig@...gle.com>,
	Michal Marek <mmarek@...e.cz>,
	"x86\@kernel.org" <x86@...nel.org>, Tejun Heo <tj@...nel.org>,
	Tony Luck <tony.luck@...el.com>,
	Fenghua Yu <fenghua.yu@...el.com>, linux-ia64@...r.kernel.org,
	keescook@...omium.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] kallsyms: handle special absolute symbols

Kees Cook <keescook@...omium.org> writes:
> This forces the entire per_cpu range to be reported as absolute without
> losing their linker symbol types. Without this, the variables are
> incorrectly shown as relocated under kASLR.

I like these patches, thanks!

This one's a bit broken, since the zero-based __per_cpu_start/end thing
is an x86-64-ism.  You really do want them relocated on other
platforms, so I think you'll need do make this conditional via
a --per-cpu-absolute flag to kallsyms (which x86-64 would set).

Dumb Q: why don't we actually present these symbols as absolute in
/proc/kallsyms?  Seems like it would be clearer...

Thanks,
Rusty.
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