From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754241AbdIGHMr (ORCPT ); Thu, 7 Sep 2017 03:12:47 -0400 Received: from mail-wr0-f196.google.com ([209.85.128.196]:35867 "EHLO mail-wr0-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752021AbdIGHMq (ORCPT ); Thu, 7 Sep 2017 03:12:46 -0400 X-Google-Smtp-Source: ADKCNb5ZTkFs2BI2frrBb69BwDgqi6qnX3Dy4VSH9APWNkGo47bmC4+DP/r9NyojhzQha2WUCJ2qlA== Date: Thu, 7 Sep 2017 09:12:42 +0200 From: Ingo Molnar To: Miguel Bernal Marin Cc: Josh Poimboeuf , Peter Zijlstra , Ingo Molnar , Thomas Gleixner , "H . Peter Anvin" , linux-kernel@vger.kernel.org, x86@kernel.org Subject: Re: [PATCH v2 1/3] locking/rwsem/x86: Add stack frame dependency for __up_read() Message-ID: <20170907071242.rgbw33qmjhhkujyl@gmail.com> References: <20170906052613.30058-1-miguel.bernal.marin@linux.intel.com> <20170906224501.11816-1-miguel.bernal.marin@linux.intel.com> <20170906224501.11816-2-miguel.bernal.marin@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170906224501.11816-2-miguel.bernal.marin@linux.intel.com> User-Agent: NeoMutt/20170113 (1.7.2) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Miguel Bernal Marin wrote: > kernel/locking/rwsem.o: warning: objtool: up_read()+0x11: call without frame pointer save/setup > > The warning means gcc 7.2.0 placed the __up_read() inline asm (and its > call instruction) before the frame pointer setup in up_read(), > 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 a34e0d4b957d..762167afaec0 100644 > --- a/arch/x86/include/asm/rwsem.h > +++ b/arch/x86/include/asm/rwsem.h > @@ -166,14 +166,16 @@ static inline bool __down_write_trylock(struct rw_semaphore *sem) > static inline void __up_read(struct rw_semaphore *sem) > { > long tmp; > + register void *__sp asm(_ASM_SP); > + > asm volatile("# beginning __up_read\n\t" > - LOCK_PREFIX " xadd %1,(%2)\n\t" > + LOCK_PREFIX " xadd %1,(%3)\n\t" > /* subtracts 1, returns the old value */ > " jns 1f\n\t" > " call call_rwsem_wake\n" /* expects old value in %edx */ > "1:\n" > "# ending __up_read\n" > - : "+m" (sem->count), "=d" (tmp) > + : "+m" (sem->count), "=d" (tmp), "+r" (__sp) > : "a" (sem), "1" (-RWSEM_ACTIVE_READ_BIAS) > : "memory", "cc"); Please also convert it to named operands (in separate patches!) - this apparently BASIC inspired labeling syntax of GCC is utterly confusing, counterproductive and somewhat embarrasing as well, considering that we write 2017. Thanks, Ingo