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s390/bug: Convert to inline assembly with input operands

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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] 6584ff203a ("bugs/s390: Use 'cond_str' in __EMIT_BUG()")

Reviewed-by: Sven Schnelle <svens@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
This commit is contained in:
Heiko Carstens 2026-01-09 16:31:37 +01:00
parent e5f3e67de5
commit e3abd056ff
1 changed files with 32 additions and 43 deletions
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75
arch/s390/include/asm/bug.h
View File

@ -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) \
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
#endif /* CONFIG_BUG */
#endif /* CONFIG_BUG && CONFIG_CC_HAS_ASM_IMMEDIATE_STRINGS */
#include <asm-generic/bug.h>