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Date:   Wed, 2 Nov 2022 13:01:26 -0700
From:   Kees Cook <keescook@chromium.org>
To:     Heiko Carstens <hca@linux.ibm.com>,
        Sami Tolvanen <samitolvanen@google.com>
Cc:     Nathan Chancellor <nathan@kernel.org>,
        Alexandra Winter <wintera@linux.ibm.com>,
        Wenjia Zhang <wenjia@linux.ibm.com>,
        Vasily Gorbik <gor@linux.ibm.com>,
        Alexander Gordeev <agordeev@linux.ibm.com>,
        Christian Borntraeger <borntraeger@linux.ibm.com>,
        Sven Schnelle <svens@linux.ibm.com>,
        linux-s390@vger.kernel.org, netdev@vger.kernel.org,
        Nick Desaulniers <ndesaulniers@google.com>,
        Tom Rix <trix@redhat.com>, llvm@lists.linux.dev,
        linux-kernel@vger.kernel.org, patches@lists.linux.dev
Subject: Re: [PATCH 1/3] s390/ctcm: Fix return type of ctc{mp,}m_tx()
Message-ID: <202211021259.9169F5CBE@keescook>
References: <20221102163252.49175-1-nathan@kernel.org>
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On Wed, Nov 02, 2022 at 08:48:42PM +0100, Heiko Carstens wrote:
> On Wed, Nov 02, 2022 at 09:32:50AM -0700, Nathan Chancellor wrote:
> > should s390 select ARCH_SUPPORTS_CFI_CLANG in the future.
> 
> Yes, s390 should select that :)
> 
> But, is there any switch or option I need to set when compiling clang,
> so it knows about the kcfi sanitizer?
> 
> I get:
> clang-16: error: unsupported option '-fsanitize=kcfi' for target 's390x-ibm-linux'
> 
> > clang --version
> clang version 16.0.0 (https://github.com/llvm/llvm-project.git e02110e2ab4dd71b276e887483f0e6e286d243ed)

You'll need the "generic arch support": https://reviews.llvm.org/D135411
which is _almost_ landed. Testing would be welcome, for sure!

Sami, do you have any notes on what common things were needed to get
arm64 and x86_64 booting under kCFI? My only oh-so-helpful notes are
"keep CFI away from early boot code". :P

-- 
Kees Cook