linux-kernel - [PATCH v2 13/14] powerpc/bug: Annotate reachable after warning trap

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Message-Id: <c5df2e21e585078677c7444cb6aee3e4404047ce.1687430631.git.christophe.leroy@csgroup.eu>
Date:   Thu, 22 Jun 2023 12:54:35 +0200
From:   Christophe Leroy <christophe.leroy@...roup.eu>
To:     Michael Ellerman <mpe@...erman.id.au>,
        Nicholas Piggin <npiggin@...il.com>,
        Josh Poimboeuf <jpoimboe@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Sathvika Vasireddy <sv@...ux.ibm.com>,
        Naveen N Rao <naveen@...nel.org>
Cc:     Christophe Leroy <christophe.leroy@...roup.eu>,
        linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: [PATCH v2 13/14] powerpc/bug: Annotate reachable after warning trap

This commit is copied from commit bfb1a7c91fb7 ("x86/bug: Merge
annotate_reachable() into _BUG_FLAGS() asm")

'twi 31,0,0' is a BUG instruction, which is by default a dead end.

But the same instruction is used for WARNINGs and the execution
resumes with the following instruction. Mark it reachable so
that objtool knows that it is not a dead end in that case.

Also change the unreachable() annotation by __builtin_unreachable()
since objtool already knows that a BUG instruction is a dead end.

Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
---
 arch/powerpc/include/asm/bug.h | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/arch/powerpc/include/asm/bug.h b/arch/powerpc/include/asm/bug.h
index a565995fb742..5550ebffb146 100644
--- a/arch/powerpc/include/asm/bug.h
+++ b/arch/powerpc/include/asm/bug.h
@@ -4,6 +4,7 @@
 #ifdef __KERNEL__
 
 #include <asm/asm-compat.h>
+#include <linux/objtool.h>
 
 #ifdef CONFIG_BUG
 
@@ -51,10 +52,11 @@
 	".previous\n"
 #endif
 
-#define BUG_ENTRY(insn, flags, ...)			\
+#define BUG_ENTRY(insn, flags, extra, ...)		\
 	__asm__ __volatile__(				\
 		"1:	" insn "\n"			\
 		_EMIT_BUG_ENTRY				\
+		extra					\
 		: : "i" (__FILE__), "i" (__LINE__),	\
 		  "i" (flags),				\
 		  "i" (sizeof(struct bug_entry)),	\
@@ -67,12 +69,12 @@
  */
 
 #define BUG() do {						\
-	BUG_ENTRY("twi 31, 0, 0", 0);				\
-	unreachable();						\
+	BUG_ENTRY("twi 31, 0, 0", 0, "");			\
+	__builtin_unreachable();				\
 } while (0)
 #define HAVE_ARCH_BUG
 
-#define __WARN_FLAGS(flags) BUG_ENTRY("twi 31, 0, 0", BUGFLAG_WARNING | (flags))
+#define __WARN_FLAGS(flags) BUG_ENTRY("twi 31, 0, 0", BUGFLAG_WARNING | (flags), ASM_REACHABLE)
 
 #ifdef CONFIG_PPC64
 #define BUG_ON(x) do {						\
@@ -80,7 +82,7 @@
 		if (x)						\
 			BUG();					\
 	} else {						\
-		BUG_ENTRY(PPC_TLNEI " %4, 0", 0, "r" ((__force long)(x)));	\
+		BUG_ENTRY(PPC_TLNEI " %4, 0", 0, "", "r" ((__force long)(x)));	\
 	}							\
 } while (0)
 
@@ -92,7 +94,7 @@
 	} else {						\
 		BUG_ENTRY(PPC_TLNEI " %4, 0",			\
 			  BUGFLAG_WARNING | BUGFLAG_TAINT(TAINT_WARN),	\
-			  "r" (__ret_warn_on));	\
+			  "", "r" (__ret_warn_on));	\
 	}							\
 	unlikely(__ret_warn_on);				\
 })
-- 
2.40.1