Re: [PATCH 2/2] bugs/s390: Use inline assembly without input operands

Alexander Gordeev
2025-06-20T13:15:49Z

On Tue, Jun 17, 2025 at 03:50:42PM +0200, Heiko Carstens wrote:
> The recent change which adds DEBUG_BUGVERBOSE_DETAILED support for s390
> changed the __EMIT_BUG() inline assembly so it has a string as immediate
> input operand. Some older gcc variants cannot handle strings as immediate
> input operands for inline assemblies. Doing so may result in compile
> errors:
>
> mm/mempool.c: In function 'remove_element':
> include/linux/compiler_types.h:497:20: warning: asm operand 0 probably
> doesn't match constraints
> #define asm_inline asm __inline
> ^~~
> arch/s390/include/asm/bug.h:12:2: note: in expansion of macro 'asm_inline'
> asm_inline volatile( \
> ^~~~~~~~~~
> arch/s390/include/asm/bug.h:43:2: note: in expansion of macro '__EMIT_BUG'
> __EMIT_BUG("", 0); \
> ^~~~~~~~~~
> include/asm-generic/bug.h:77:57: note: in expansion of macro 'BUG'
> #define BUG_ON(condition) do { if (unlikely(condition)) BUG(); } while (0)
> ^~~
> mm/mempool.c:149:2: note: in expansion of macro 'BUG_ON'
> BUG_ON(pool->curr_nr < 0);
> ^~~~~~
> include/linux/compiler_types.h:497:20: error: impossible constraint in 'asm'
> #define asm_inline asm __inline
> ^~~
>
> Rewrite the s390 generic bug support very similar to arm64 and loongarch,
> and get rid of all input operands to fix this.
>
> Fixes: 45c79ca947c9 ("bugs/s390: Use 'cond_str' in __EMIT_BUG()")
> Reported-by: Linux Kernel Functional Testing <lkft@linaro.org>
> Closes: https://lore.kernel.org/r/CA+G9fYuu5r34=bndUYWNxe_yLgBaPGXmK9WP3WTtoXMs_2LX-Q@mail.gmail.com
> Cc: Anders Roxell <anders.roxell@linaro.org>
> Cc: Naresh Kamboju <naresh.kamboju@linaro.org>
> Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
> ---
> arch/s390/include/asm/bug.h | 81 +++++++++++++++++++------------------
> 1 file changed, 41 insertions(+), 40 deletions(-)
...

Acked-by: Alexander Gordeev <agordeev@linux.ibm.com>