Re: [PATCH v2] kernel/module.c: heuristic enhancement when INSTALL_MOD_STRIP= "--strip-unneeded" is used

From: Vimal Agrawal <avimalin@gmail.com>
To: Luis Chamberlain <mcgrof@kernel.org>
Cc: Christoph Hellwig <hch@infradead.org>,
	Vimal Agrawal <vimal.Agrawal@sophos.com>,
	Masahiro Yamada <masahiroy@kernel.org>,
	Michal Marek <michal.lkml@markovi.net>,
	Nick Desaulniers <ndesaulniers@google.com>,
	Jan Beulich <JBeulich@suse.com>, Jeff Mahoney <jeffm@suse.com>,
	Sam Ravnborg <sam@ravnborg.org>,
	linux-kbuild@vger.kernel.org, jeyu@kernel.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2] kernel/module.c: heuristic enhancement when INSTALL_MOD_STRIP= "--strip-unneeded" is used
Date: Wed, 12 Jan 2022 14:06:48 +0530	[thread overview]
Message-ID: <CALkUMdSc8eNbqptTihwzqhpL9qhGS0xUFr=AFXs3COvpyBoQiw@mail.gmail.com> (raw)
In-Reply-To: <Yd2nJZRtc3OjPb0w@bombadil.infradead.org>

On Tue, Jan 11, 2022 at 9:19 PM Luis Chamberlain <mcgrof@kernel.org> wrote:
> Yes but the point here is the heuristic you are adding for
> when "--strip-unneeded" is used is now *always* being used and
> we have no way of knowing this. So I'd agree with Christoph that
> if we want to support this it might make sense to make a kconfig
> option for enabling "--strip-unneeded" and then another for this
> heuristic.

This heuristic is applicable to any case when an address inside a
module can not be decoded to any known symbol. e.g. anyone can still
build with ----strip-all though module load fails with this option.
but one can add or remove symbols manually or use objcopy or some
other utility to play with symbols. It does not matter for
functionality much if symbols are available or not and it is just that
symbol decodes in traces are not providing help as it displays
absolute address in such cases.

There are several options in strip command and we can't have kconfig
for each such option. All options are supported currently unless the
module is so broken that it can even be loaded ( e.g. --strip-all
option).

Vimal