From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1468FC432C0 for ; Mon, 25 Nov 2019 17:38:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E627E20836 for ; Mon, 25 Nov 2019 17:38:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729157AbfKYRiC (ORCPT ); Mon, 25 Nov 2019 12:38:02 -0500 Received: from foss.arm.com ([217.140.110.172]:53306 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725868AbfKYRiB (ORCPT ); Mon, 25 Nov 2019 12:38:01 -0500 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id E134731B; Mon, 25 Nov 2019 09:38:00 -0800 (PST) Received: from lakrids.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.121.207.14]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 75FDE3F68E; Mon, 25 Nov 2019 09:37:59 -0800 (PST) Date: Mon, 25 Nov 2019 17:37:57 +0000 From: Mark Rutland To: Marco Elver Cc: will@kernel.org, peterz@infradead.org, boqun.feng@gmail.com, arnd@arndb.de, dvyukov@google.com, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, kasan-dev@googlegroups.com, paulmck@kernel.org, Randy Dunlap Subject: Re: [PATCH 1/2] asm-generic/atomic: Prefer __always_inline for wrappers Message-ID: <20191125173756.GF32635@lakrids.cambridge.arm.com> References: <20191122154221.247680-1-elver@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191122154221.247680-1-elver@google.com> User-Agent: Mutt/1.11.1+11 (2f07cb52) (2018-12-01) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Nov 22, 2019 at 04:42:20PM +0100, Marco Elver wrote: > Prefer __always_inline for atomic wrappers. When building for size > (CC_OPTIMIZE_FOR_SIZE), some compilers appear to be less inclined to > inline even relatively small static inline functions that are assumed to > be inlinable such as atomic ops. This can cause problems, for example in > UACCESS regions. >From looking at the link below, the problem is tat objtool isn't happy about non-whiteliested calls within UACCESS regions. Is that a problem here? are the kasan/kcsan calls whitelisted? > By using __always_inline, we let the real implementation and not the > wrapper determine the final inlining preference. That sounds reasonable to me, assuming that doesn't end up significantly bloating the kernel text. What impact does this have on code size? > This came up when addressing UACCESS warnings with CC_OPTIMIZE_FOR_SIZE > in the KCSAN runtime: > http://lkml.kernel.org/r/58708908-84a0-0a81-a836-ad97e33dbb62@infradead.org > > Reported-by: Randy Dunlap > Signed-off-by: Marco Elver > --- > include/asm-generic/atomic-instrumented.h | 334 +++++++++++----------- > include/asm-generic/atomic-long.h | 330 ++++++++++----------- > scripts/atomic/gen-atomic-instrumented.sh | 6 +- > scripts/atomic/gen-atomic-long.sh | 2 +- > 4 files changed, 336 insertions(+), 336 deletions(-) Do we need to do similar for gen-atomic-fallback.sh and the fallbacks defined in scripts/atomic/fallbacks/ ? [...] > diff --git a/scripts/atomic/gen-atomic-instrumented.sh b/scripts/atomic/gen-atomic-instrumented.sh > index 8b8b2a6f8d68..68532d4f36ca 100755 > --- a/scripts/atomic/gen-atomic-instrumented.sh > +++ b/scripts/atomic/gen-atomic-instrumented.sh > @@ -84,7 +84,7 @@ gen_proto_order_variant() > [ ! -z "${guard}" ] && printf "#if ${guard}\n" > > cat < -static inline ${ret} > +static __always_inline ${ret} We should add an include of to the preamble if we're explicitly using __always_inline. > diff --git a/scripts/atomic/gen-atomic-long.sh b/scripts/atomic/gen-atomic-long.sh > index c240a7231b2e..4036d2dd22e9 100755 > --- a/scripts/atomic/gen-atomic-long.sh > +++ b/scripts/atomic/gen-atomic-long.sh > @@ -46,7 +46,7 @@ gen_proto_order_variant() > local retstmt="$(gen_ret_stmt "${meta}")" > > cat < -static inline ${ret} > +static __always_inline ${ret} Likewise here Thanks, Mark.