[RFC 1/8] x86: Provide assembly __bug_table helpers

Peter Zijlstra
2025-06-02T14:50:43Z

Rework the __bug_table helpers such that usage from assembly becomes
possible.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
arch/x86/include/asm/bug.h | 54 ++++++++++++++++++++-------------------------
1 file changed, 24 insertions(+), 30 deletions(-)

--- a/arch/x86/include/asm/bug.h
+++ b/arch/x86/include/asm/bug.h
@@ -32,46 +32,40 @@
#ifdef CONFIG_GENERIC_BUG

#ifdef CONFIG_X86_32
-# define __BUG_REL(val) ".long " __stringify(val)
+#define ASM_BUG_REL(val) .long val
#else
-# define __BUG_REL(val) ".long " __stringify(val) " - ."
+#define ASM_BUG_REL(val) .long val - .
#endif

#ifdef CONFIG_DEBUG_BUGVERBOSE
+#define ASM_BUGTABLE_VERBOSE(file, line) \
+ ASM_BUG_REL(file) ; \
+ .word line
+#define ASM_BUGTABLE_VERBOSE_SIZE 6 /* sizeof(file) + sizeof(line) */
+#else
+#define ASM_BUGTABLE_VERBOSE(file, line)
+#define ASM_BUGTABLE_VERBOSE_SIZE 0
+#endif

-#define _BUG_FLAGS(ins, flags, extra) \
-do { \
- asm_inline volatile("1:\t" ins "\n" \
- ".pushsection __bug_table,\"aw\"\n" \
- "2:\t" __BUG_REL(1b) "\t# bug_entry::bug_addr\n" \
- "\t" __BUG_REL(%c0) "\t# bug_entry::file\n" \
- "\t.word %c1" "\t# bug_entry::line\n" \
- "\t.word %c2" "\t# bug_entry::flags\n" \
- "\t.org 2b+%c3\n" \
- ".popsection\n" \
- extra \
- : : "i" (__FILE__), "i" (__LINE__), \
- "i" (flags), \
- "i" (sizeof(struct bug_entry))); \
-} while (0)
+#define ASM_BUGTABLE_BASE_SIZE 6 /* sizeof(bug_addr) + sizeof(flags) */

-#else /* !CONFIG_DEBUG_BUGVERBOSE */
+#define ASM_BUGTABLE_FLAGS(at, file, line, flags) \
+ .pushsection __bug_table, "aw" ; \
+ 123: ASM_BUG_REL(at) ; \
+ ASM_BUGTABLE_VERBOSE(file, line) ; \
+ .word flags ; \
+ .org 123b + ASM_BUGTABLE_BASE_SIZE + ASM_BUGTABLE_VERBOSE_SIZE ;\
+ .popsection

-#define _BUG_FLAGS(ins, flags, extra) \
+#define _BUG_FLAGS(insn, flags, extra) \
do { \
- asm_inline volatile("1:\t" ins "\n" \
- ".pushsection __bug_table,\"aw\"\n" \
- "2:\t" __BUG_REL(1b) "\t# bug_entry::bug_addr\n" \
- "\t.word %c0" "\t# bug_entry::flags\n" \
- "\t.org 2b+%c1\n" \
- ".popsection\n" \
- extra \
- : : "i" (flags), \
- "i" (sizeof(struct bug_entry))); \
+ asm_inline volatile("1:\t" insn "\n" \
+ __stringify(ASM_BUGTABLE_FLAGS(1b, %c[file], %c[line], %c[fl])) "\n" \
+ extra \
+ : : [file] "i" (__FILE__), [line] "i" (__LINE__), \
+ [fl] "i" (flags)); \
} while (0)

-#endif /* CONFIG_DEBUG_BUGVERBOSE */
-
#else

#define _BUG_FLAGS(ins, flags, extra) asm volatile(ins)