[RFC 5/8] x86_64/bug: Add BUG_FORMAT basics

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

Opt-in to BUG_FORMAT for x86_64, adjust the BUGTABLE helper and for
now, just store NULL pointers.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
arch/x86/include/asm/bug.h | 22 ++++++++++++++++++----
1 file changed, 18 insertions(+), 4 deletions(-)

--- a/arch/x86/include/asm/bug.h
+++ b/arch/x86/include/asm/bug.h
@@ -31,6 +31,7 @@

#ifdef CONFIG_GENERIC_BUG

+
#ifdef CONFIG_X86_32
#define ASM_BUG_REL(val) .long val
#else
@@ -47,22 +48,35 @@
#define ASM_BUGTABLE_VERBOSE_SIZE 0
#endif

+#ifdef CONFIG_X86_64
+#define HAVE_ARCH_BUG_FORMAT
+#define ASM_BUGTABLE_FORMAT(format) \
+ ASM_BUG_REL(format)
+#define ASM_BUGTABLE_FORMAT_SIZE 4 /* sizeof(format) */
+#else
+#define ASM_BUGTABLE_FORMAT(format)
+#define ASM_BUGTABLE_FORMAT_SIZE 0
+#endif
+
#define ASM_BUGTABLE_BASE_SIZE 6 /* sizeof(bug_addr) + sizeof(flags) */

-#define ASM_BUGTABLE_FLAGS(at, file, line, flags) \
+#define ASM_BUGTABLE_FLAGS(at, format, file, line, flags) \
.pushsection __bug_table, "aw" ; \
123: ASM_BUG_REL(at) ; \
+ ASM_BUGTABLE_FORMAT(format) ; \
ASM_BUGTABLE_VERBOSE(file, line) ; \
.word flags ; \
- .org 123b + ASM_BUGTABLE_BASE_SIZE + ASM_BUGTABLE_VERBOSE_SIZE ;\
+ .org 123b + ASM_BUGTABLE_BASE_SIZE + ASM_BUGTABLE_FORMAT_SIZE + ASM_BUGTABLE_VERBOSE_SIZE ; \
.popsection

#define _BUG_FLAGS(insn, flags, extra) \
do { \
asm_inline volatile("1:\t" insn "\n" \
- __stringify(ASM_BUGTABLE_FLAGS(1b, %c[file], %c[line], %c[fl])) "\n" \
+ __stringify(ASM_BUGTABLE_FLAGS(1b, %c[fmt], %c[file], %c[line], %c[fl])) "\n" \
extra \
- : : [file] "i" (__FILE__), [line] "i" (__LINE__), \
+ : : [fmt] "i" (NULL), \
+ [file] "i" (__FILE__), \
+ [line] "i" (__LINE__), \
[fl] "i" (flags)); \
} while (0)