- Fix a case where objtool would mistakenly warn about instructions being unreachable

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Merge tag 'objtool_urgent_for_v5.17_rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull objtool fix from Borislav Petkov:
 "Fix a case where objtool would mistakenly warn about instructions
  being unreachable"

* tag 'objtool_urgent_for_v5.17_rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/bug: Merge annotate_reachable() into _BUG_FLAGS() asm

arch/x86/include/asm/bug.h

@@ -22,7 +22,7 @@
 
 #ifdef CONFIG_DEBUG_BUGVERBOSE
 
-#define _BUG_FLAGS(ins, flags)						\
+#define _BUG_FLAGS(ins, flags, extra)					\
 do {									\
 	asm_inline volatile("1:\t" ins "\n"				\
 		     ".pushsection __bug_table,\"aw\"\n"		\
@@ -31,7 +31,8 @@ do {									\
 		     "\t.word %c1"        "\t# bug_entry::line\n"	\
 		     "\t.word %c2"        "\t# bug_entry::flags\n"	\
 		     "\t.org 2b+%c3\n"					\
-		     ".popsection"					\
+		     ".popsection\n"					\
+		     extra						\
 		     : : "i" (__FILE__), "i" (__LINE__),		\
 			 "i" (flags),					\
 			 "i" (sizeof(struct bug_entry)));		\
@@ -39,14 +40,15 @@ do {									\
 
 #else /* !CONFIG_DEBUG_BUGVERBOSE */
 
-#define _BUG_FLAGS(ins, flags)						\
+#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.word %c0"        "\t# bug_entry::flags\n"	\
 		     "\t.org 2b+%c1\n"					\
-		     ".popsection"					\
+		     ".popsection\n"					\
+		     extra						\
 		     : : "i" (flags),					\
 			 "i" (sizeof(struct bug_entry)));		\
 } while (0)
@@ -55,7 +57,7 @@ do {									\
 
 #else
 
-#define _BUG_FLAGS(ins, flags)  asm volatile(ins)
+#define _BUG_FLAGS(ins, flags, extra)  asm volatile(ins)
 
 #endif /* CONFIG_GENERIC_BUG */
 
@@ -63,8 +65,8 @@ do {									\
 #define BUG()							\
 do {								\
 	instrumentation_begin();				\
-	_BUG_FLAGS(ASM_UD2, 0);					\
-	unreachable();						\
+	_BUG_FLAGS(ASM_UD2, 0, "");				\
+	__builtin_unreachable();				\
 } while (0)
 
 /*
@@ -75,9 +77,9 @@ do {								\
  */
 #define __WARN_FLAGS(flags)					\
 do {								\
+	__auto_type f = BUGFLAG_WARNING|(flags);		\
 	instrumentation_begin();				\
-	_BUG_FLAGS(ASM_UD2, BUGFLAG_WARNING|(flags));		\
-	annotate_reachable();					\
+	_BUG_FLAGS(ASM_UD2, f, ASM_REACHABLE);			\
 	instrumentation_end();					\
 } while (0)
 

include/linux/compiler.h

@@ -117,14 +117,6 @@ void ftrace_likely_update(struct ftrace_likely_data *f, int val,
  */
 #define __stringify_label(n) #n
 
-#define __annotate_reachable(c) ({					\
-	asm volatile(__stringify_label(c) ":\n\t"			\
-		     ".pushsection .discard.reachable\n\t"		\
-		     ".long " __stringify_label(c) "b - .\n\t"		\
-		     ".popsection\n\t" : : "i" (c));			\
-})
-#define annotate_reachable() __annotate_reachable(__COUNTER__)
-
 #define __annotate_unreachable(c) ({					\
 	asm volatile(__stringify_label(c) ":\n\t"			\
 		     ".pushsection .discard.unreachable\n\t"		\
@@ -133,24 +125,21 @@ void ftrace_likely_update(struct ftrace_likely_data *f, int val,
 })
 #define annotate_unreachable() __annotate_unreachable(__COUNTER__)
 
-#define ASM_UNREACHABLE							\
-	"999:\n\t"							\
-	".pushsection .discard.unreachable\n\t"				\
-	".long 999b - .\n\t"						\
+#define ASM_REACHABLE							\
+	"998:\n\t"							\
+	".pushsection .discard.reachable\n\t"				\
+	".long 998b - .\n\t"						\
 	".popsection\n\t"
 
 /* Annotate a C jump table to allow objtool to follow the code flow */
 #define __annotate_jump_table __section(".rodata..c_jump_table")
 
 #else
-#define annotate_reachable()
 #define annotate_unreachable()
+# define ASM_REACHABLE
 #define __annotate_jump_table
 #endif
 
-#ifndef ASM_UNREACHABLE
-# define ASM_UNREACHABLE
-#endif
 #ifndef unreachable
 # define unreachable() do {		\
 	annotate_unreachable();		\