s390: Exception based WARN() / WARN_ONCE()

[PATCH 0/9] s390: Exception based WARN() / WARN_ONCE()

Posted by Heiko Carstens 1 week, 2 days ago

Use the generic infrastructure introduced by Peter Zijlstra [1] to implement
an exception based WARN() and WARN_ONCE() similar to x86.

Due to some compiler oddities on s390 this requires to raise the minimum gcc
version to 9. Maybe there are ways to avoid this, but I failed to find a
working solution. Details are in the patch descriptions.

Just posting this now to also get some compile bot testing, since I'm afraid
there might be some compiler version / config option around where even this
new approach breaks.

Peter, since you were wondering: your generic infrastructure pieces work very
nice. Looking at the x86 and s390 implementation: it might be possible to make
things even more generic since both __WARN_printf(), and WARN_ONCE() are
identical; it looks like only __WARN_print_arg() needs to be provided.

Arnd, just adding you so you know that there may be an architecture
which requires gcc-9 instead of gcc-8 in the near future.

Series is based on
git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux.git features

...and not yet meant to be included anywhere.

Thanks,
Heiko

[1] https://lore.kernel.org/all/20251110114633.202485143@infradead.org/

Heiko Carstens (9):
  kbuild: Require gcc-9 for s390
  s390/bug: Convert to inline assembly with input operands
  s390/bug: Use BUG_FORMAT for DEBUG_BUGVERBOSE_DETAILED
  s390/bug: Introduce and use monitor code macro
  s390/traps: Copy monitor code to pt_regs
  s390/bug: Implement __WARN_printf()
  s390/bug: Implement WARN_ONCE()
  s390/bug: Skip __WARN_trap() in call traces
  s390/bug: Prevent tail-call optimization

 arch/s390/include/asm/bug.h    | 141 ++++++++++++++++++++++++---------
 arch/s390/include/asm/ptrace.h |   5 +-
 arch/s390/kernel/entry.S       |   7 ++
 arch/s390/kernel/traps.c       |  42 +++++++++-
 scripts/min-tool-version.sh    |   2 +
 5 files changed, 156 insertions(+), 41 deletions(-)

base-commit: 70075e3d0ca0b72cc983d03f7cd9796e43492980
-- 
2.51.0

Re: [PATCH 0/9] s390: Exception based WARN() / WARN_ONCE()

Posted by Peter Zijlstra 1 week, 2 days ago

On Tue, Dec 09, 2025 at 01:16:52PM +0100, Heiko Carstens wrote:
> Use the generic infrastructure introduced by Peter Zijlstra [1] to implement
> an exception based WARN() and WARN_ONCE() similar to x86.
> 
> Due to some compiler oddities on s390 this requires to raise the minimum gcc
> version to 9. Maybe there are ways to avoid this, but I failed to find a
> working solution. Details are in the patch descriptions.
> 
> Just posting this now to also get some compile bot testing, since I'm afraid
> there might be some compiler version / config option around where even this
> new approach breaks.
> 
> Peter, since you were wondering: your generic infrastructure pieces work very
> nice. Looking at the x86 and s390 implementation: it might be possible to make
> things even more generic since both __WARN_printf(), and WARN_ONCE() are
> identical; it looks like only __WARN_print_arg() needs to be provided.

Nice! and yeah, perhaps we can unify that later.