Commit e3abd056 authored by Heiko Carstens's avatar Heiko Carstens
Browse files

s390/bug: Convert to inline assembly with input operands 



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.

Note: since gcc-8 does not support strings as immediate input operands,
guard the new implementation with CC_HAS_ASM_IMMEDIATE_STRINGS and fallback
to the generic non-exception based warning implementation for incompatible
compilers.

[1] 6584ff20 ("bugs/s390: Use 'cond_str' in __EMIT_BUG()")

Reviewed-by: default avatarSven Schnelle <svens@linux.ibm.com>
Signed-off-by: default avatarHeiko Carstens <hca@linux.ibm.com>
parent e5f3e67d

arch/s390/include/asm/bug.h

+31 −42
Original line number Diff line number Diff line
@@ -2,60 +2,49 @@ 
#ifndef _ASM_S390_BUG_H

#define _ASM_S390_BUG_H



#include <linux/stringify.h>

#include <linux/compiler.h>



#ifdef CONFIG_BUG

#if defined(CONFIG_BUG) && defined(CONFIG_CC_HAS_ASM_IMMEDIATE_STRINGS)



#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)				\

#define __BUG_ASM(cond_str, flags)					\

do {									\

	__BUG_FLAGS(cond_str, BUGFLAG_WARNING|(flags));		\

	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);					\

	__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



#endif /* CONFIG_BUG */

#endif /* CONFIG_BUG && CONFIG_CC_HAS_ASM_IMMEDIATE_STRINGS */



#include <asm-generic/bug.h>