linux-kernel - Re: [PATCH v4 0/3] kallsyms base relative series

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Date:	Mon, 25 Jan 2016 09:44:10 -0800
From:	Guenter Roeck <linux@...ck-us.net>
To:	Ard Biesheuvel <ard.biesheuvel@...aro.org>,
	linux-kernel@...r.kernel.org, linux-s390@...r.kernel.org,
	linuxppc-dev@...ts.ozlabs.org, x86@...nel.org,
	keescook@...omium.org, akpm@...ux-foundation.org, mingo@...nel.org,
	hpa@...or.com, heiko.carstens@...ibm.com, benh@...nel.crashing.org,
	mpe@...erman.id.au, mmarek@...e.cz, rusty@...tcorp.com.au,
	arnd@...db.de, linux-arch@...r.kernel.org
Subject: Re: [PATCH v4 0/3] kallsyms base relative series

On 01/25/2016 06:19 AM, Ard Biesheuvel wrote:
> This v4 of my kallsyms base relative implementation is now a 3 piece series,
> since it caused some problems due to the way absolute symbols are handled
> by the absolute per cpu code. As it turns out, that code was probably wrong
> in the sense that it caused non-relocated symbol addresses to be emitted
> for values that are in fact relative to the address of the kernel text.
>
> Patch #1 fixes the scripts/kallsyms invocation to only pass the x86_64
> specific --absolute-percpu option if CONFIG_SMP is also set.
>
> Patch #2 reworks the absolute percpu code to only emit those percpu symbols
> as absolute, and not symbols that have been classified as 'A' (absolute) by
> the linker, since that does not mean quite the same thing.
>
> Patch #3 is the original kallsyms base relative patch, with some
> modifications:
> - folded the s/ULLONG_MAX/-1ULL? change made by Andrew
> - ensured that the kallsyms_relative_base value itself is relocated as
>    required.
> - dropped all of the acks and other tags, as they have become outdated with
>    the recent changes to this patch.
>

I tested the series on top of mmotm (after reverting the original patches).
Qemu tests for mips, sparc, and x86 (both smp and nosmp) now pass.

Tested-by: Guenter Roeck <linux@...ck-us.net>

> Ard Biesheuvel (3):
>    x86: kallsyms: disable absolute percpu symbols on !SMP
>    kallsyms: don't overload absolute symbol type for percpu symbols
>    kallsyms: add support for relative offsets in kallsyms address table
>
>   init/Kconfig            |  16 +++
>   kernel/kallsyms.c       |  38 ++++++--
>   scripts/kallsyms.c      | 102 +++++++++++++++++---
>   scripts/link-vmlinux.sh |   6 +-
>   scripts/namespace.pl    |   2 +
>   5 files changed, 142 insertions(+), 22 deletions(-)
>