Re: [PATCH v3 0/4] s390: Enable Rust support and add required arch glue

[Miguel Ojeda]

On Wed, May 27, 2026 at 12:53 PM Gary Guo <gary@xxxxxxxxxxx> wrote:
>
> Looking at the functions and the test case I don't understand how this could
> happen. Could be a miscompilation?
>
> Perhaps it'll be useful to provide rustc and Clang/LLVM versions so it can be
> investigated.

Yeah, as we discussed, it seems due to s390 emulating 1-byte `xchg`
with a 4-byte read.

A deterministic reproducer is e.g.:

  make LLVM=1 ARCH=s390 defconfig + KASAN + no MODVERSIONS + RUST + KUNIT

  qemu-system-s390x -kernel arch/s390/boot/bzImage -nographic -m 1G

Cheers,
Miguel