[PATCH 0/2] bugs/s390: Fix compile error with old gcc versions

[PATCH 0/2] bugs/s390: Fix compile error with old gcc versions

[Heiko Carstens]

As reported by Naresh and Anders old gcc variants cannot handle
strings as input operands for inline assemblies. Rewrite the s390
generic bug support very similar to arm64 and loongarch to fix this.

Also use the opportunity to drop the rather pointless s390 specific
WARN_ON() implementation.

Ingo, I think the two patches should also go via the core/bugs branch
of the tip repository.

Thanks,
Heiko

Heiko Carstens (2):
  bugs/s390: Remove private WARN_ON() implementation
  bugs/s390: Use inline assembly without input operands

 arch/s390/include/asm/bug.h | 94 ++++++++++++++++---------------------
 1 file changed, 41 insertions(+), 53 deletions(-)

-- 
2.48.1

[PATCH 1/2] bugs/s390: Remove private WARN_ON() implementation

[Heiko Carstens]

Besides an odd __builtin_constant_p() optimization the s390 specific
WARN_ON() implementation is identical to the generic variant.
Drop the s390 variant in favor of the generic variant.

Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
---
 arch/s390/include/asm/bug.h | 13 -------------
 1 file changed, 13 deletions(-)

diff --git a/arch/s390/include/asm/bug.h b/arch/s390/include/asm/bug.h
index 837bfbde0c51..58ab4efd9dd5 100644
--- a/arch/s390/include/asm/bug.h
+++ b/arch/s390/include/asm/bug.h
@@ -48,20 +48,7 @@
 	__EMIT_BUG(cond_str, BUGFLAG_WARNING|(flags));	\
 } while (0)
 
-#define WARN_ON(x) ({					\
-	int __ret_warn_on = !!(x);			\
-	if (__builtin_constant_p(__ret_warn_on)) {	\
-		if (__ret_warn_on)			\
-			__WARN();			\
-	} else {					\
-		if (unlikely(__ret_warn_on))		\
-			__WARN();			\
-	}						\
-	unlikely(__ret_warn_on);			\
-})
-
 #define HAVE_ARCH_BUG
-#define HAVE_ARCH_WARN_ON
 #endif /* CONFIG_BUG */
 
 #include <asm-generic/bug.h>
-- 
2.48.1

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

[Heiko Carstens]

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(-)

diff --git a/arch/s390/include/asm/bug.h b/arch/s390/include/asm/bug.h
index 58ab4efd9dd5..a185855ab158 100644
--- a/arch/s390/include/asm/bug.h
+++ b/arch/s390/include/asm/bug.h
@@ -2,54 +2,55 @@
 #ifndef _ASM_S390_BUG_H
 #define _ASM_S390_BUG_H
 
-#include <linux/compiler.h>
+#include <linux/stringify.h>
 
-#ifdef CONFIG_BUG
+#ifndef CONFIG_DEBUG_BUGVERBOSE
+#define _BUGVERBOSE_LOCATION(file, line)
+#else
+#define __BUGVERBOSE_LOCATION(file, line)			\
+		.pushsection .rodata.str, "aMS", @progbits, 1;	\
+	10002:	.string file;					\
+		.popsection;					\
+								\
+		.long 10002b - .;				\
+		.short line;
+#define _BUGVERBOSE_LOCATION(file, line) __BUGVERBOSE_LOCATION(file, line)
+#endif
 
-#ifdef CONFIG_DEBUG_BUGVERBOSE
+#ifndef CONFIG_GENERIC_BUG
+#define __BUG_ENTRY(cond_str, flags)
+#else
+#define __BUG_ENTRY(cond_str, flags)				\
+		.pushsection __bug_table, "aw";			\
+		.align 4;					\
+	10000:	.long 10001f - .;				\
+		_BUGVERBOSE_LOCATION(WARN_CONDITION_STR(cond_str) __FILE__, __LINE__) \
+		.short flags;					\
+		.popsection;					\
+	10001:
+#endif
 
-#define __EMIT_BUG(cond_str, x) do {				\
-	asm_inline volatile(					\
-		"0:	mc	0,0\n"				\
-		".section __bug_table,\"aw\"\n"			\
-		"1:	.long	0b-.\n"				\
-		"	.long	%0-.\n"				\
-		"	.short	%1,%2\n"			\
-		"	.org	1b+%3\n"			\
-		".previous\n"					\
-		: : "i" (WARN_CONDITION_STR(cond_str) __FILE__),\
-		    "i" (__LINE__),				\
-		    "i" (x),					\
-		    "i" (sizeof(struct bug_entry)));		\
+#define ASM_BUG_FLAGS(cond_str, flags)				\
+	__BUG_ENTRY(cond_str, flags)				\
+	mc		0,0
+
+#define ASM_BUG()	ASM_BUG_FLAGS("", 0)
+
+#define __BUG_FLAGS(cond_str, flags)				\
+	asm_inline volatile(__stringify(ASM_BUG_FLAGS(cond_str, flags)));
+
+#define __WARN_FLAGS(cond_str, flags)				\
+do {								\
+	__BUG_FLAGS(cond_str, BUGFLAG_WARNING|(flags));		\
 } while (0)
 
-#else /* CONFIG_DEBUG_BUGVERBOSE */
-
-#define __EMIT_BUG(cond_str, x) do {				\
-	asm_inline volatile(					\
-		"0:	mc	0,0\n"				\
-		".section __bug_table,\"aw\"\n"			\
-		"1:	.long	0b-.\n"				\
-		"	.short	%0\n"				\
-		"	.org	1b+%1\n"			\
-		".previous\n"					\
-		: : "i" (x),					\
-		    "i" (sizeof(struct bug_entry)));		\
-} while (0)
-
-#endif /* CONFIG_DEBUG_BUGVERBOSE */
-
-#define BUG() do {					\
-	__EMIT_BUG("", 0);				\
-	unreachable();					\
-} while (0)
-
-#define __WARN_FLAGS(cond_str, flags) do {		\
-	__EMIT_BUG(cond_str, BUGFLAG_WARNING|(flags));	\
+#define BUG()							\
+do {								\
+	__BUG_FLAGS("", 0);					\
+	unreachable();						\
 } while (0)
 
 #define HAVE_ARCH_BUG
-#endif /* CONFIG_BUG */
 
 #include <asm-generic/bug.h>
 
-- 
2.48.1

Re: [PATCH 1/2] bugs/s390: Remove private WARN_ON() implementation

[Alexander Gordeev]

On Tue, Jun 17, 2025 at 03:50:41PM +0200, Heiko Carstens wrote:
> Besides an odd __builtin_constant_p() optimization the s390 specific
> WARN_ON() implementation is identical to the generic variant.
> Drop the s390 variant in favor of the generic variant.
> 
> Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
> ---
>  arch/s390/include/asm/bug.h | 13 -------------
>  1 file changed, 13 deletions(-)
...

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

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

[Alexander Gordeev]

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>

Re: [PATCH 0/2] bugs/s390: Fix compile error with old gcc versions

[Heiko Carstens]

Hi Ingo,

> As reported by Naresh and Anders old gcc variants cannot handle
> strings as input operands for inline assemblies. Rewrite the s390
> generic bug support very similar to arm64 and loongarch to fix this.
> 
> Also use the opportunity to drop the rather pointless s390 specific
> WARN_ON() implementation.
> 
> Ingo, I think the two patches should also go via the core/bugs branch
> of the tip repository.

You might have missed this, but this was directed to you :)