linux-kernel - Re: [PATCH] kbuild: lto: fix module versionings mismatch in incremental build

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <202106150821.B4D3E02@keescook>
Date:   Tue, 15 Jun 2021 08:22:23 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Lecopzer Chen <lecopzer.chen@...iatek.com>
Cc:     clang-built-linux@...glegroups.com, linux-kbuild@...r.kernel.org,
        linux-kernel@...r.kernel.org, masahiroy@...nel.org,
        michal.lkml@...kovi.net, nathan@...nel.org,
        ndesaulniers@...gle.com, samitolvanen@...gle.com,
        yj.chiang@...iatek.com
Subject: Re: [PATCH] kbuild: lto: fix module versionings mismatch in
 incremental build

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