[PATCH 02/22] objtool: Warn when disabling unreachable warnings

[Josh Poimboeuf <jpoimboe@kernel.org>]

Print a warning when disabling the unreachable warnings (due to a GCC
bug).  This will help determine if recent GCCs still have the issue and
alert us if any other issues might be silently lurking behind the
unreachable disablement.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
---
 tools/objtool/arch/x86/special.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/tools/objtool/arch/x86/special.c b/tools/objtool/arch/x86/special.c
index 9c1c9df09aaa..5f46d4e7f7f8 100644
--- a/tools/objtool/arch/x86/special.c
+++ b/tools/objtool/arch/x86/special.c
@@ -3,6 +3,7 @@
 
 #include <objtool/special.h>
 #include <objtool/builtin.h>
+#include <objtool/warn.h>
 
 #define X86_FEATURE_POPCNT (4 * 32 + 23)
 #define X86_FEATURE_SMAP   (9 * 32 + 20)
@@ -156,8 +157,10 @@ struct reloc *arch_find_switch_table(struct objtool_file *file,
 	 * indicates a rare GCC quirk/bug which can leave dead
 	 * code behind.
 	 */
-	if (reloc_type(text_reloc) == R_X86_64_PC32)
+	if (reloc_type(text_reloc) == R_X86_64_PC32) {
+		WARN_INSN(insn, "ignoring unreachables due to jump table quirk");
 		file->ignore_unreachables = true;
+	}
 
 	*table_size = 0;
 	return rodata_reloc;
-- 
2.48.1