Hi Heiko,
On Wed, May 11, 2022 at 02:05:24PM +0200, Heiko Carstens wrote:
> A couple of patches which in result make it finally possible to build the
> kernel for s390 with llvm's integrated assembler. Several configs build
> without errors or warnings, and the kernel also works as expected.
>
> Note that patch 6 ("s390/boot: workaround llvm IAS bug") reveals a
> miscompile. This looks like a bug in the instruction definitions of the mvc
> and clc instructions(?). I'd like to ask people to look into this, since
> this silently generated broken code.
I think it should be pretty simple to file a bug report for this since
it occurs in a standalone assembly file? I agree with Nick that there
should be a bug report filed and linked to in patch 6 so that we don't
lose track of it.
> This patch series is based on linux-next, which contains two additional
> required s390 specific patches to make llvm's IAS work.
>
> Thanks,
> Heiko
>
> Heiko Carstens (8):
> s390/alternatives: provide identical sized orginal/alternative sequences
> s390/alternatives: remove padding generation code
> s390/entry: shorten OUTSIDE macro
> s390/entry: workaround llvm's IAS limitations
> s390/purgatory: workaround llvm's IAS limitations
> s390/boot: workaround llvm IAS bug
> s390/boot: do not emit debug info for assembly with llvm's IAS
> scripts/min-tool-version.sh: raise minimum clang version to 14.0.0 for s390
>
> arch/s390/Makefile | 2 +
> arch/s390/boot/head.S | 34 +++++----
> arch/s390/include/asm/alternative-asm.h | 76 +++-----------------
> arch/s390/include/asm/alternative.h | 93 ++++++-------------------
> arch/s390/include/asm/spinlock.h | 2 +-
> arch/s390/kernel/alternative.c | 61 +---------------
> arch/s390/kernel/entry.S | 39 +++++++----
> arch/s390/lib/spinlock.c | 4 +-
> arch/s390/purgatory/head.S | 29 ++++++--
> scripts/min-tool-version.sh | 3 +-
> 10 files changed, 104 insertions(+), 239 deletions(-)
I applied this series to the latest s390 for-next branch (c4fb15578802)
and built a few in-tree and distribution configurations with clang-14
and clang-15 then boot tested them in QEMU with a simple buildroot
userspace. I did not see any new warnings or errors. This is awesome, I
am excited to get this wired up in our CI!
In case it is worthwhile:
Tested-by: Nathan Chancellor <nathan@xxxxxxxxxx>
Cheers,
Nathan
