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

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Message-ID: <20250617135042.1878068-3-hca@linux.ibm.com>
Date: Tue, 17 Jun 2025 15:50:42 +0200
From: Heiko Carstens <hca@...ux.ibm.com>
To: Ingo Molnar <mingo@...hat.com>, Naresh Kamboju <naresh.kamboju@...aro.org>,
        Anders Roxell <anders.roxell@...aro.org>
Cc: Alexander Gordeev <agordeev@...ux.ibm.com>,
        Sven Schnelle <svens@...ux.ibm.com>, Vasily Gorbik <gor@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        linux-kernel@...r.kernel.org, linux-s390@...r.kernel.org
Subject: [PATCH 2/2] bugs/s390: Use inline assembly without input operands

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@...aro.org>
Closes: https://lore.kernel.org/r/CA+G9fYuu5r34=bndUYWNxe_yLgBaPGXmK9WP3WTtoXMs_2LX-Q@mail.gmail.com
Cc: Anders Roxell <anders.roxell@...aro.org>
Cc: Naresh Kamboju <naresh.kamboju@...aro.org>
Signed-off-by: Heiko Carstens <hca@...ux.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