Subject: Re: [PATCH 1/3] s390/ctcm: Fix return type of ctc{mp,}m_tx()

From: Kees Cook <[email-masked]>
Date: Wed, 2 Nov 2022 13:01:26 -0700

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