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=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS 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 B1A98C433DF for ; Thu, 2 Jul 2020 10:18:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9BA9920772 for ; Thu, 2 Jul 2020 10:18:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728193AbgGBKS0 (ORCPT ); Thu, 2 Jul 2020 06:18:26 -0400 Received: from foss.arm.com ([217.140.110.172]:35036 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727769AbgGBKSZ (ORCPT ); Thu, 2 Jul 2020 06:18:25 -0400 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 E240D1FB; Thu, 2 Jul 2020 03:18:24 -0700 (PDT) Received: from C02TD0UTHF1T.local (unknown [10.57.12.193]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 9EA193F71E; Thu, 2 Jul 2020 03:18:22 -0700 (PDT) Date: Thu, 2 Jul 2020 11:18:19 +0100 From: Mark Rutland To: Marc Zyngier Cc: Will Deacon , Catalin Marinas , Daniel Lezcano , Vincenzo Frascino , Thomas Gleixner , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, kernel-team@android.com Subject: Re: [PATCH 1/3] arm64: Introduce a way to disable the 32bit vdso Message-ID: <20200702101819.GB15391@C02TD0UTHF1T.local> References: <20200701161824.1346732-1-maz@kernel.org> <20200701161824.1346732-2-maz@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200701161824.1346732-2-maz@kernel.org> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jul 01, 2020 at 05:18:22PM +0100, Marc Zyngier wrote: > We have a class of errata (grouped under the ARM64_WORKAROUND_1418040 > banner) that force the trapping of counter access from 32bit EL0. > > We would normally disable the whole vdso for such defect, except that > it would disable it for 64bit userspace as well, which is a shame. > > Instead, add a new vdso_clock_mode, which signals that the vdso > isn't usable for compat tasks. This gets checked in the new > vdso_clocksource_ok() helper, now provided for the 32bit vdso. > > Signed-off-by: Marc Zyngier As-is this looks sound to me. It's not entirely clear to me how this will compose with VDSO_CLOCKMODE_TIMENS, but given this series is fixing an existing brokenness I think this has higher priority. Minor comment below, but regardless: Acked-by: Mark Rutland > --- > arch/arm64/include/asm/vdso/clocksource.h | 7 +++++-- > arch/arm64/include/asm/vdso/compat_gettimeofday.h | 8 +++++++- > 2 files changed, 12 insertions(+), 3 deletions(-) > > diff --git a/arch/arm64/include/asm/vdso/clocksource.h b/arch/arm64/include/asm/vdso/clocksource.h > index df6ea65c1dec..b054d9febfb5 100644 > --- a/arch/arm64/include/asm/vdso/clocksource.h > +++ b/arch/arm64/include/asm/vdso/clocksource.h > @@ -2,7 +2,10 @@ > #ifndef __ASM_VDSOCLOCKSOURCE_H > #define __ASM_VDSOCLOCKSOURCE_H > > -#define VDSO_ARCH_CLOCKMODES \ > - VDSO_CLOCKMODE_ARCHTIMER > +#define VDSO_ARCH_CLOCKMODES \ > + /* vdso clocksource for both 32 and 64bit tasks */ \ > + VDSO_CLOCKMODE_ARCHTIMER, \ > + /* vdso clocksource for 64bit tasks only */ \ > + VDSO_CLOCKMODE_ARCHTIMER_NOCOMPAT > > #endif > diff --git a/arch/arm64/include/asm/vdso/compat_gettimeofday.h b/arch/arm64/include/asm/vdso/compat_gettimeofday.h > index b6907ae78e53..9a625e8947ff 100644 > --- a/arch/arm64/include/asm/vdso/compat_gettimeofday.h > +++ b/arch/arm64/include/asm/vdso/compat_gettimeofday.h > @@ -111,7 +111,7 @@ static __always_inline u64 __arch_get_hw_counter(s32 clock_mode) > * update. Return something. Core will do another round and then > * see the mode change and fallback to the syscall. > */ > - if (clock_mode == VDSO_CLOCKMODE_NONE) > + if (clock_mode != VDSO_CLOCKMODE_ARCHTIMER) > return 0; > > /* > @@ -152,6 +152,12 @@ static __always_inline const struct vdso_data *__arch_get_vdso_data(void) > return ret; > } > > +static inline bool vdso_clocksource_ok(const struct vdso_data *vd) > +{ > + return vd->clock_mode == VDSO_CLOCKMODE_ARCHTIMER; > +} > +#define vdso_clocksource_ok vdso_clocksource_ok Existing issue, but it's a shame this doesn't take the clock mode directly, then we wouldn't have to duplicate the conditions (as above, inverted). Mark.