[PATCH 2/9] s390/bug: Convert to inline assembly with input operands

[Heiko Carstens <hca@linux.ibm.com>]

Rewrite the bug inline assembly so it uses input operands again instead of
pure macro replacements. This more or less reverts the conversion done when
'cond_str' support was added [1].

Reason for this is that the upcoming __WARN_printf() implementation
requires an inline assembly with an output operand. At the same time input
strings (format specifier and condition string) may contain the special '%'
character. As soon as an inline assembly is specified to have input/output
operands the '%' has a special meaning: e.g. converting the existing

 #define __BUG_FLAGS(cond_str, flags) \
   asm_inline volatile(__stringify(ASM_BUG_FLAGS(cond_str, flags)));

to

 #define __BUG_FLAGS(cond_str, flags) \
   asm_inline volatile(__stringify(ASM_BUG_FLAGS(cond_str, flags))::);

will result in a compile error as soon as 'cond_str' contains a '%'
character:

net/core/neighbour.c: In function ‘neigh_table_init’:
././include/linux/compiler_types.h:546:20: error: invalid 'asm': invalid %-code
...
net/core/neighbour.c:1838:17: note: in expansion of macro ‘WARN_ON’
 1838 |                 WARN_ON(tbl->entry_size % NEIGH_PRIV_ALIGN);
      |                 ^~~~~~~

Convert the code, use immediate operands, and also add comments similar to
x86 which are emitted to the generated assembly file, which makes debugging
much easier.

[1] 6584ff203aec ("bugs/s390: Use 'cond_str' in __EMIT_BUG()")

Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
---
 arch/s390/include/asm/bug.h | 71 ++++++++++++++++---------------------
 1 file changed, 30 insertions(+), 41 deletions(-)

diff --git a/arch/s390/include/asm/bug.h b/arch/s390/include/asm/bug.h
index ee9221bb5d18..61496143a382 100644
--- a/arch/s390/include/asm/bug.h
+++ b/arch/s390/include/asm/bug.h
@@ -2,55 +2,44 @@
 #ifndef _ASM_S390_BUG_H
 #define _ASM_S390_BUG_H
 
-#include <linux/stringify.h>
+#include <linux/compiler.h>
 
 #ifdef CONFIG_BUG
 
-#ifndef CONFIG_DEBUG_BUGVERBOSE
-#define _BUGVERBOSE_LOCATION(file, line)
+#ifdef CONFIG_DEBUG_BUGVERBOSE
+#define __BUG_ENTRY_VERBOSE(file, line)					\
+	"	.long	" file " - .	# bug_entry::file\n"		\
+	"	.short	" line "	# bug_entry::line\n"
 #else
-#define __BUGVERBOSE_LOCATION(file, line)			\
-		.pushsection .rodata.str, "aMS", @progbits, 1;	\
-		.align 2;					\
-	10002:	.ascii file "\0";				\
-		.popsection;					\
-								\
-		.long 10002b - .;				\
-		.short line;
-#define _BUGVERBOSE_LOCATION(file, line) __BUGVERBOSE_LOCATION(file, line)
+#define __BUG_ENTRY_VERBOSE(file, line)
 #endif
 
-#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 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));		\
+#define __BUG_ASM(cond_str, flags)					\
+do {									\
+	asm_inline volatile("\n"					\
+		"0:	mc	0,0\n"					\
+		"	.section __bug_table,\"aw\"\n"			\
+		"1:	.long	0b - .	# bug_entry::bug_addr\n"	\
+		__BUG_ENTRY_VERBOSE("%[file]", "%[line]")		\
+		"	.short	%[flgs]	# bug_entry::flags\n"		\
+		"	.org	1b+%[size]\n"				\
+		"	.previous"					\
+		:							\
+		: [file] "i" (WARN_CONDITION_STR(cond_str) __FILE__),	\
+		  [line] "i" (__LINE__),				\
+		  [flgs] "i" (flags),					\
+		  [size] "i" (sizeof(struct bug_entry)));		\
 } while (0)
 
-#define BUG()							\
-do {								\
-	__BUG_FLAGS("", 0);					\
-	unreachable();						\
+#define BUG()								\
+do {									\
+	__BUG_ASM("", 0);						\
+	unreachable();							\
+} while (0)
+
+#define __WARN_FLAGS(cond_str, flags)					\
+do {									\
+	__BUG_ASM(cond_str, BUGFLAG_WARNING | (flags));			\
 } while (0)
 
 #define HAVE_ARCH_BUG
-- 
2.51.0