From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752041AbdIFF1D (ORCPT ); Wed, 6 Sep 2017 01:27:03 -0400 Received: from mga01.intel.com ([192.55.52.88]:27835 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751913AbdIFF0h (ORCPT ); Wed, 6 Sep 2017 01:26:37 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.41,482,1498546800"; d="scan'208";a="308411974" From: Miguel Bernal Marin To: Peter Zijlstra , Ingo Molnar , Thomas Gleixner , "H . Peter Anvin" Cc: linux-kernel@vger.kernel.org, x86@kernel.org Subject: [PATCH 3/3] locking/rwsem/x86: Add stack frame dependency for __downgrade_write() Date: Wed, 6 Sep 2017 00:26:13 -0500 Message-Id: <20170906052613.30058-4-miguel.bernal.marin@linux.intel.com> X-Mailer: git-send-email 2.14.1 In-Reply-To: <20170906052613.30058-1-miguel.bernal.marin@linux.intel.com> References: <20170906052613.30058-1-miguel.bernal.marin@linux.intel.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org kernel/locking/rwsem.o: warning: objtool: downgrade_write()+0x22: call without frame pointer save/setup The warning means gcc 7.2.0 placed the __downgrade_write() inline asm (and its call instruction) before the frame pointer setup in downgrade_write(), which breaks frame pointer convention and can result in incorrect stack traces. Force a stack frame to be created before the call instruction by listing the stack pointer as an output operand in the inline asm statement. Signed-off-by: Miguel Bernal Marin --- arch/x86/include/asm/rwsem.h | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/arch/x86/include/asm/rwsem.h b/arch/x86/include/asm/rwsem.h index d26b6916b935..a749dc6a3103 100644 --- a/arch/x86/include/asm/rwsem.h +++ b/arch/x86/include/asm/rwsem.h @@ -205,8 +205,10 @@ static inline void __up_write(struct rw_semaphore *sem) */ static inline void __downgrade_write(struct rw_semaphore *sem) { + register void *__sp asm(_ASM_SP); + asm volatile("# beginning __downgrade_write\n\t" - LOCK_PREFIX _ASM_ADD "%2,(%1)\n\t" + LOCK_PREFIX _ASM_ADD "%2,(%2)\n\t" /* * transitions 0xZZZZ0001 -> 0xYYYY0001 (i386) * 0xZZZZZZZZ00000001 -> 0xYYYYYYYY00000001 (x86_64) @@ -215,7 +217,7 @@ static inline void __downgrade_write(struct rw_semaphore *sem) " call call_rwsem_downgrade_wake\n" "1:\n\t" "# ending __downgrade_write\n" - : "+m" (sem->count) + : "+m" (sem->count), "+r" (__sp) : "a" (sem), "er" (-RWSEM_WAITING_BIAS) : "memory", "cc"); } -- 2.14.1