linux-kernel - Re: [PATCH v2] kernel/module.c: heuristic enhancement when INSTALL_MOD

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Date:   Sat, 25 Dec 2021 06:38:02 +0530
From:   Vimal Agrawal <avimalin@...il.com>
To:     Christoph Hellwig <hch@...radead.org>
Cc:     Luis Chamberlain <mcgrof@...nel.org>,
        Vimal Agrawal <vimal.Agrawal@...hos.com>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Michal Marek <michal.lkml@...kovi.net>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Jan Beulich <JBeulich@...e.com>, Jeff Mahoney <jeffm@...e.com>,
        Sam Ravnborg <sam@...nborg.org>, linux-kbuild@...r.kernel.org,
        jeyu@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] kernel/module.c: heuristic enhancement when
 INSTALL_MOD_STRIP= "--strip-unneeded" is used

On Fri, Dec 24, 2021 at 12:17 PM Christoph Hellwig <hch@...radead.org> wrote:
>
> I don't think we can support passing arbitrary linker options and
> expects things to work.  If we want to support --strip-unneeded
> it needs a good rationale and be added as a direct config option.
INSTALL_MOD_STRIP was provided to give flexibility for providing
strippping options. It will be a separate discussion if we want to
continue allowing this flexibility or not but it is available now. I
see that it works but just that it is behaving erratically during
symbol decodes. I tried few other stripping options. --strip-all does
not work and insmod fails as it needs some symbols which is fine as it
is hinting the user there is a problem with stripping option. This is
not the case with --strip-unneeded option as it builds and loads/works
fine but fails to decode symbols properly sometimes.

One of the rationale for --strip-unneeded option is that it
significantly reduces the size of .ko without affecting its
functionality ( though debuggability takes a hit). I guess many
platforms/products that need limited memory footprint might be using
this option.

I am fine if we decide to say that --strip-unneeded option is not
supported by kbuild/INSTALL_MOD_STRIP which is not the case now. In
that case, I agree that this patch will not even be required.

Vimal