linux-kernel - [tip:core/urgent] objtool: Skip unreachable warnings for GCC 4.4 and older

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Date:   Wed, 27 Sep 2017 22:31:01 -0700
From:   tip-bot for Josh Poimboeuf <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     tglx@...utronix.de, jpoimboe@...hat.com,
        linux-kernel@...r.kernel.org, hpa@...or.com, peterz@...radead.org,
        fengguang.wu@...el.com, torvalds@...ux-foundation.org,
        mingo@...nel.org
Subject: [tip:core/urgent] objtool: Skip unreachable warnings for GCC 4.4
 and older

Commit-ID:  da541b20021c781f8b65492eeaee824e729599eb
Gitweb:     https://git.kernel.org/tip/da541b20021c781f8b65492eeaee824e729599eb
Author:     Josh Poimboeuf <jpoimboe@...hat.com>
AuthorDate: Wed, 27 Sep 2017 17:34:23 -0500
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Thu, 28 Sep 2017 07:23:02 +0200

objtool: Skip unreachable warnings for GCC 4.4 and older

The kbuild bot occasionally reports warnings like:

  drivers/scsi/pcmcia/aha152x_core.o: warning: objtool: seldo_run()+0x130: unreachable instruction

These warnings are always with GCC 4.4.  That version of GCC sometimes
places unreachable instructions after calls to noreturn functions.

The unreachable warnings aren't very important anyway.  Just ignore them
for old versions of GCC.

Reported-by: kbuild test robot <fengguang.wu@...el.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@...hat.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Link: http://lkml.kernel.org/r/bc89b807d965b98ec18a0bb94f96a594bd58f2f2.1506551639.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 scripts/Makefile.build | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index 2e3a10e7..061d0c3 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -265,6 +265,8 @@ objtool_args += --no-fp
 endif
 ifdef CONFIG_GCOV_KERNEL
 objtool_args += --no-unreachable
+else
+objtool_args += $(call cc-ifversion, -lt, 0405, --no-unreachable)
 endif
 
 # 'OBJECT_FILES_NON_STANDARD := y': skip objtool checking for a directory