linux-kernel - Re: [PATCH v2 08/12] x86/bug: Add BUG

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Message-ID: <20251126105651.GX3245006@noisy.programming.kicks-ass.net>
Date: Wed, 26 Nov 2025 11:56:51 +0100
From: Peter Zijlstra <peterz@...radead.org>
To: Linus Torvalds <torvalds@...uxfoundation.org>
Cc: x86@...nel.org, ardb@...nel.org, linux-kernel@...r.kernel.org,
	kees@...nel.org, acarmina@...hat.com, jpoimboe@...nel.org,
	mark.rutland@....com, maciej.wieczor-retman@...el.com
Subject: Re: [PATCH v2 08/12] x86/bug: Add BUG_FORMAT basics

On Tue, Nov 25, 2025 at 08:27:50AM -0800, Linus Torvalds wrote:
> (Slightly related thing: could we perhaps just make x86-32 also use
> the relative format, and get rid of some of the horrid #ifdef's in the
> x86 <asm/bug.h> implementation? Because that "__BUG_REL" thing is not
> a thing of beauty either).

This builds and appears to work. I'll slap a changelog on and stick on
top of those other patches.

--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -381,7 +381,7 @@ config GENERIC_CSUM
 config GENERIC_BUG
 	def_bool y
 	depends on BUG
-	select GENERIC_BUG_RELATIVE_POINTERS if X86_64
+	select GENERIC_BUG_RELATIVE_POINTERS
 
 config GENERIC_BUG_RELATIVE_POINTERS
 	bool
--- a/arch/x86/include/asm/bug.h
+++ b/arch/x86/include/asm/bug.h
@@ -42,16 +42,10 @@ extern void __WARN_trap(struct bug_entry
 
 #ifdef CONFIG_GENERIC_BUG
 
-#ifdef CONFIG_X86_32
-#define __BUG_REL(val)		".long " val
-#else
-#define __BUG_REL(val)		".long " val " - ."
-#endif
-
 #ifdef CONFIG_DEBUG_BUGVERBOSE
 #define __BUG_ENTRY_VERBOSE(file, line)					\
-	"\t" __BUG_REL(file)   "\t# bug_entry::file\n"			\
-	"\t.word " line        "\t# bug_entry::line\n"
+	"\t.long " file " - .\t# bug_entry::file\n"			\
+	"\t.word " line     "\t# bug_entry::line\n"
 #else
 #define __BUG_ENTRY_VERBOSE(file, line)
 #endif
@@ -59,7 +53,7 @@ extern void __WARN_trap(struct bug_entry
 #if defined(CONFIG_X86_64) || defined(CONFIG_DEBUG_BUGVERBOSE_DETAILED)
 #define HAVE_ARCH_BUG_FORMAT
 #define __BUG_ENTRY_FORMAT(format)					\
-	"\t" __BUG_REL(format)	"\t# bug_entry::format\n"
+	"\t.long " format " - .\t# bug_entry::format\n"
 #else
 #define __BUG_ENTRY_FORMAT(format)
 #endif
@@ -69,7 +63,7 @@ extern void __WARN_trap(struct bug_entry
 #endif
 
 #define __BUG_ENTRY(format, file, line, flags)				\
-	__BUG_REL("1b")		"\t# bug_entry::bug_addr\n"		\
+	"\t.long 1b - ."	"\t# bug_entry::bug_addr\n"		\
 	__BUG_ENTRY_FORMAT(format)					\
 	__BUG_ENTRY_VERBOSE(file, line)					\
 	"\t.word " flags	"\t# bug_entry::flags\n"