linux-kernel - Re: [PATCH v3 0/9] klp-convert livepatch build tooling

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Message-ID: <452e0cc5-ea9b-1638-3557-17e12671e21e@redhat.com>
Date:   Tue, 16 Apr 2019 09:55:00 -0400
From:   Joe Lawrence <joe.lawrence@...hat.com>
To:     linux-kernel@...r.kernel.org, live-patching@...r.kernel.org,
        linux-kbuild@...r.kernel.org
Cc:     Jessica Yu <jeyu@...nel.org>, Jiri Kosina <jikos@...nel.org>,
        Joao Moreira <jmoreira@...e.de>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Konstantin Khlebnikov <khlebnikov@...dex-team.ru>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Michael Matz <matz@...e.de>, Miroslav Benes <mbenes@...e.cz>,
        Nicolai Stange <nstange@...e.de>,
        Petr Mladek <pmladek@...e.com>
Subject: Re: [PATCH v3 0/9] klp-convert livepatch build tooling

On 4/10/19 11:50 AM, Joe Lawrence wrote:
> Hi folks,
> 
> This is the third installment of the klp-convert tool for generating and
> processing livepatch symbols for livepatch module builds.  For those
> following along at home, archive links to previous versions:
> 
> RFC:
>    https://lore.kernel.org/lkml/cover.1477578530.git.jpoimboe@redhat.com/
> v2:
>    https://lore.kernel.org/lkml/f52d29f7-7d1b-ad3d-050b-a9fa8878faf2@redhat.com/
> 
> (Note that I don't see v2 archived at lore, but that is a link to the
> most recent subthread that lore did catch.)
> 
> 
> Livepatches may use symbols which are not contained in its own scope,
> and, because of that, may end up compiled with relocations that will
> only be resolved during module load. Yet, when the referenced symbols are
> not exported, solving this relocation requires information on the object
> that holds the symbol (either vmlinux or modules) and its position inside
> the object, as an object may contain multiple symbols with the same name.
> Providing such information must be done accordingly to what is specified
> in Documentation/livepatch/module-elf-format.txt.

Hi Miroslav,

I noticed that some binutils programs like gdb, objdump, etc. don't like 
the .ko kernel objects that we're generating from this patchset, 
specifically those with the additional '.klp.rela.<obj>..text' livepatch 
symbol relocation sections.

For reference, I opened a new bugzilla with more details here:
https://sourceware.org/bugzilla/show_bug.cgi?id=24456

And was about to ping the binutils mailing list about the assertion that 
is tripping in bfd/elf.c.  The thought occurred to me that you guys 
might already be carrying a patch to workaround this issue?

-- Joe