From: Kees Cook <keescook@chromium.org>
To: Lecopzer Chen <lecopzer.chen@mediatek.com>
Cc: clang-built-linux@googlegroups.com, linux-kbuild@vger.kernel.org,
linux-kernel@vger.kernel.org, masahiroy@kernel.org,
michal.lkml@markovi.net, nathan@kernel.org,
ndesaulniers@google.com, samitolvanen@google.com,
yj.chiang@mediatek.com
Subject: Re: [PATCH] kbuild: lto: fix module versionings mismatch in incremental build
Date: Tue, 15 Jun 2021 08:22:23 -0700 [thread overview]
Message-ID: <202106150821.B4D3E02@keescook> (raw)
In-Reply-To: <20210615062658.21633-1-lecopzer.chen@mediatek.com>
On Tue, Jun 15, 2021 at 02:26:58PM +0800, Lecopzer Chen wrote:
> > On Mon, Jun 14, 2021 at 01:51:09PM +0800, Lecopzer Chen wrote:
> > > When building modules(CONFIG_...=m), I found some of module versions
> > > are incorrect and set to 0.
> > > This can be found in build log for first clean build which shows
> > >
> > > WARNING: EXPORT symbol "XXXX" [drivers/XXX/XXX.ko] version generation failed, symbol will not be versioned.
> >
> > I'm doing this, and I don't see the problem:
> >
> > $ make LLVM=1 LLVM_IAS=1 distclean
> > $ make LLVM=1 LLVM_IAS=1 menuconfig
> > *enable LTO*
> > *enable a module*
> > $ make LLVM=1 LLVM_IAS=1 -j...
> >
> > What series of commands (and .config) shows this for you?
>
> Hi Kees,
>
> Thanks for you checking.
>
> After double checking in clean android kernel build, this causes by
> make version.
> (I have build failed in Linux LTO,
> seems it's not well support in contract to android?)
>
> I knew Google has LTO first in Android and upstream later, and most code
> are same as upstream, so the env here I use Android common kernel for
> easily testing.
>
>
> Test env is android common kernel: android12-5.4 [1] with its latest code
> and it builds from build.sh[2]
>
> $ BUILD_CONFIG=common/build.config.gki.aarch64 build/build.sh
> + make O=.... LLVM=1 LLVM_IAS=1 DEPMOD=depmod -j12 Image modules Image.lz4
>
> With make set to v3.81, this can be reproduced with CONFIG_TEE=m.
> With version >= 4.2 this is not reproducible.
Ah, very interesting. While there are tests in Makefile for
MAKE_VERSION, if we want to do this, it should likely be extended to
Kconfig, as that's where the initial version tests for things happen. We
could require MAKE_VERSION >= 4.2 for LTO?
-Kees
>
>
> Our build env default set make to v3.81, although Android uses hermetic build
> and v4.3 now, but Linux doesn't have such things.
>
> Maybe we can add build time checking or comment before CFI module versioning
> build rules to avoid anyone struggling with this again:).
>
> [1] https://android.googlesource.com/kernel/common/+/refs/heads/android12-5.4
> [2] https://android.googlesource.com/kernel/build/+/refs/heads/master
>
> thanks,
> Lecopzer
>
>
--
Kees Cook
next prev parent reply other threads:[~2021-06-15 15:22 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-14 5:51 [PATCH] kbuild: lto: fix module versionings mismatch in incremental build Lecopzer Chen
2021-06-14 9:49 ` Lecopzer Chen
2021-06-14 23:09 ` Kees Cook
2021-06-15 6:26 ` Lecopzer Chen
2021-06-15 15:22 ` Kees Cook [this message]
2021-06-16 8:02 ` Lecopzer Chen
2021-06-16 16:43 ` Kees Cook
2021-06-17 1:58 ` Lecopzer Chen
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