From: Masahiro Yamada <masahiroy@kernel.org>
To: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Michal Marek <michal.lkml@markovi.net>,
linux-hardening@vger.kernel.org,
Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Justin Forbes <jforbes@redhat.com>,
Ondrej Mosnacek <omosnace@redhat.com>,
Frank Eigler <fche@redhat.com>, Kees Cook <keescook@chromium.org>
Subject: Re: [PATCH RFC] gcc-plugins: Handle GCC version mismatch for OOT modules
Date: Fri, 5 Mar 2021 00:35:44 +0900 [thread overview]
Message-ID: <CAK7LNAR0kNJ=DLuvRzRG+-rgMfcrSOZu8Mn6JBJ5do7TzJWLcA@mail.gmail.com> (raw)
In-Reply-To: <20210304150812.rzya7ewmerwhe4m4@treble>
On Fri, Mar 5, 2021 at 12:08 AM Josh Poimboeuf <jpoimboe@redhat.com> wrote:
>
> On Thu, Mar 04, 2021 at 09:27:28PM +0900, Masahiro Yamada wrote:
> > I agree with rebuilding GCC plugins when the compiler is upgraded
> > for *in-tree* building.
> > Linus had reported it a couple of months before,
> > and I just submitted a very easy fix.
>
> Hm? So does that mean that a GCC version change won't trigger a
> tree-wide rebuild? So you're asserting that a GCC mismatch is ok for
> in-tree code, but not for external modules??? That seems backwards.
>
> For in-tree, why not just rebuild the entire tree? Some kernel features
> are dependent on compiler version or capability, so not rebuilding the
> tree could introduce silent breakage.
All the kernel-space objects are rebuilt
when the compiler is upgraded.
(See commit 8b59cd81dc5e724eaea283fa6006985891c7bff4)
Linus complaint about GCC plugins not being rebuilt.
^^^^^^^^^^^
https://lore.kernel.org/lkml/CAHk-=wieoN5ttOy7SnsGwZv+Fni3R6m-Ut=oxih6bbZ28G+4dw@mail.gmail.com/
That is easy to fix. I submitted a patch:
https://patchwork.kernel.org/project/linux-kbuild/patch/20210304113708.215121-1-masahiroy@kernel.org/
> For external modules, a tree-wide rebuild isn't an option so the risk is
> assumed by the user. I posted a patch earlier [1] which prints a
> warning if the compiler major/minor version changes with an external
> module build.
>
> [1] https://lkml.kernel.org/r/20210201211322.t2rxmvnrystc2ky7@treble
>
> > Rebuilding plugins for external modules is not easy;
> > plugins are placed in the read-only directory,
> > /usr/src/linux-headers-$(uname -r)/scripts/gcc-plugins/.
> >
> > The external modules must not (cannot) update in-tree
> > build artifacts. "Rebuild" means creating copies in a different
> > writable directory.
> > Doing that requires a lot of design changes.
>
> Ok. So it sounds like the best/easiest option is the original patch in
> this thread: when building an external module with a GCC mismatch, just
> disable the GCC plugin, with a warning (or an error for randstruct).
It was rejected.
If a distribution wants to enable CONFIG_GCC_PLUGINS,
it must provide GCC whose version is the same as
used for building the kernel.
If a distribution cannot manage release in that way,
do not enable CONFIG_GCC_PLUGINS in the first place.
--
Best Regards
Masahiro Yamada
next prev parent reply other threads:[~2021-03-04 15:38 UTC|newest]
Thread overview: 57+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-25 20:42 [PATCH RFC] gcc-plugins: Handle GCC version mismatch for OOT modules Josh Poimboeuf
2021-01-25 21:16 ` Masahiro Yamada
2021-01-25 21:27 ` Josh Poimboeuf
2021-01-25 21:44 ` Masahiro Yamada
2021-01-25 22:07 ` Josh Poimboeuf
2021-01-26 8:13 ` Greg KH
2021-01-26 12:44 ` Justin Forbes
2021-01-26 13:51 ` Greg KH
2021-01-26 14:51 ` Josh Poimboeuf
2021-01-26 15:00 ` Greg KH
2021-01-26 15:15 ` Peter Zijlstra
2021-01-26 15:46 ` Josh Poimboeuf
2021-01-26 16:05 ` Peter Zijlstra
2021-01-26 16:15 ` Justin Forbes
2021-01-26 16:19 ` Josh Poimboeuf
2021-01-26 17:06 ` Greg KH
2021-01-26 17:47 ` Justin Forbes
2021-01-26 16:22 ` David Laight
2021-01-27 18:03 ` Christoph Hellwig
2021-01-26 8:12 ` Greg KH
2021-01-25 22:03 ` Kees Cook
2021-01-25 22:19 ` Josh Poimboeuf
2021-01-26 17:56 ` Kees Cook
2021-01-26 18:43 ` Josh Poimboeuf
2021-01-26 22:59 ` Kees Cook
2021-01-26 23:32 ` Josh Poimboeuf
2021-01-26 1:53 ` Masahiro Yamada
2021-01-26 12:16 ` David Laight
2021-01-27 18:02 ` Christoph Hellwig
2021-01-27 18:38 ` Josh Poimboeuf
2021-01-27 18:43 ` Christoph Hellwig
2021-01-27 18:51 ` Josh Poimboeuf
2021-01-27 22:09 ` David Laight
2021-01-28 14:29 ` Christoph Hellwig
2021-01-28 15:45 ` Josh Poimboeuf
2021-03-02 23:26 ` Josh Poimboeuf
2021-03-03 18:49 ` Masahiro Yamada
2021-03-03 19:15 ` Josh Poimboeuf
2021-03-03 19:25 ` Linus Torvalds
2021-03-03 19:38 ` Josh Poimboeuf
2021-03-03 19:57 ` Linus Torvalds
2021-03-03 20:24 ` Josh Poimboeuf
2021-03-03 20:31 ` Josh Poimboeuf
2021-03-03 20:56 ` Linus Torvalds
2021-03-03 21:45 ` Josh Poimboeuf
2021-03-04 12:27 ` Masahiro Yamada
2021-03-04 15:08 ` Josh Poimboeuf
2021-03-04 15:35 ` Masahiro Yamada [this message]
2021-03-04 19:12 ` Linus Torvalds
2021-03-05 2:41 ` Josh Poimboeuf
2021-03-05 2:49 ` Linus Torvalds
2021-03-05 16:03 ` Masahiro Yamada
2021-03-05 19:18 ` Josh Poimboeuf
2021-03-08 9:39 ` David Laight
2021-03-05 15:31 ` Masahiro Yamada
2021-03-03 21:52 ` Kees Cook
2021-03-04 12:26 ` Masahiro Yamada
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