Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752100AbeADCAt (ORCPT + 1 other); Wed, 3 Jan 2018 21:00:49 -0500 Received: from mga07.intel.com ([134.134.136.100]:37434 "EHLO mga07.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752053AbeADCAq (ORCPT ); Wed, 3 Jan 2018 21:00:46 -0500 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.45,505,1508828400"; d="scan'208";a="8291991" From: Andi Kleen To: tglx@linutronix.de Cc: torvalds@linux-foundation.org, gregkh@linux-foundation.org, linux-kernel@vger.kernel.org, tim.c.chen@linux.intel.com, Andi Kleen , jpoimboe@redhat.com Subject: [PATCH v2 12/12] retpoline: Attempt to quiten objtool warning for unreachable code Date: Wed, 3 Jan 2018 18:00:19 -0800 Message-Id: <20180104020019.1173-13-andi@firstfloor.org> X-Mailer: git-send-email 2.14.3 In-Reply-To: <20180104020019.1173-1-andi@firstfloor.org> References: <20180104020019.1173-1-andi@firstfloor.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Return-Path: From: Andi Kleen The speculative jump trampoline has to contain unreachable code. objtool keeps complaining arch/x86/lib/retpoline.o: warning: objtool: __x86.indirect_thunk()+0x8: unreachable instruction I tried to fix it here by adding ASM_UNREACHABLE annotation (after supporting them for pure assembler), but it still complains. Seems like a objtool bug? So it doesn't actually fix the warning oyet. Of course it's just a warning so the kernel will still work fine. Perhaps Josh can figure it out Cc: jpoimboe@redhat.com Not-Signed-off-by: Andi Kleen --- arch/x86/lib/retpoline.S | 3 +++ include/linux/compiler.h | 10 +++++++++- 2 files changed, 12 insertions(+), 1 deletion(-) diff --git a/arch/x86/lib/retpoline.S b/arch/x86/lib/retpoline.S index cb40781adbfe..f4ed556a90ee 100644 --- a/arch/x86/lib/retpoline.S +++ b/arch/x86/lib/retpoline.S @@ -11,6 +11,7 @@ */ #include +#include #include #include @@ -21,7 +22,9 @@ ENTRY(__x86.indirect_thunk) call retpoline_call_target 2: lfence /* stop speculation */ + ASM_UNREACHABLE jmp 2b + ASM_UNREACHABLE retpoline_call_target: #ifdef CONFIG_64BIT lea 8(%rsp), %rsp diff --git a/include/linux/compiler.h b/include/linux/compiler.h index 52e611ab9a6c..cfba91acc79a 100644 --- a/include/linux/compiler.h +++ b/include/linux/compiler.h @@ -269,7 +269,15 @@ static __always_inline void __write_once_size(volatile void *p, void *res, int s #endif /* __KERNEL__ */ -#endif /* __ASSEMBLY__ */ +#else /* __ASSEMBLY__ */ + +#define ASM_UNREACHABLE \ + 999: \ + .pushsection .discard.unreachable; \ + .long 999b - .; \ + .popsection + +#endif /* !__ASSEMBLY__ */ /* Compile time object size, -1 for unknown */ #ifndef __compiletime_object_size -- 2.14.3