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=-6.0 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable 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 BC592C04AAC for ; Mon, 20 May 2019 12:41:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9297B204FD for ; Mon, 20 May 2019 12:41:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1558356076; bh=jHnr8GD1aKn2Y3iOscmw3lW7VcwC0q2BQGI0AZcz3N8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=2D98vYpRH2cG5GxgaTkkk2VRs+rjzwTnxAU/XfhvR8UpFFq+omymDEwzCmLOjodLh QHfvl5wD1Qq2Xu8ZWx+YOcM+WOG9QpHDzMGR0L/jACM0f0iaq+D88sVKdtrJ9Zpz53 FhiTqqqkUExVXgavTJl3v3wWoz6JhGbzX6iCk1ic= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2390357AbfETMbe (ORCPT ); Mon, 20 May 2019 08:31:34 -0400 Received: from mail.kernel.org ([198.145.29.99]:48148 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2390351AbfETMbe (ORCPT ); Mon, 20 May 2019 08:31:34 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 945F0216FD; Mon, 20 May 2019 12:31:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1558355493; bh=jHnr8GD1aKn2Y3iOscmw3lW7VcwC0q2BQGI0AZcz3N8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=O6Wwx4apx/MVLroV3NrPk2LWsU0Gk9+6CmiqZ+X5NVGR9vobvmzHUWkjBT5vGp9FY QBGEHs6RMBnuHDgnvqWb7wLvIzlQJk/exIunQyiQgY24iRgLuUppeeWA9gKrdIx3Qm BSjkHEg2IanYaJgF5yBzgTOl3F3mUzMB9n0fx7DA= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Marc Zyngier , Vincenzo Frascino , Thomas Gleixner , Will Deacon Subject: [PATCH 5.1 016/128] arm64: arch_timer: Ensure counter register reads occur with seqlock held Date: Mon, 20 May 2019 14:13:23 +0200 Message-Id: <20190520115250.577618868@linuxfoundation.org> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20190520115249.449077487@linuxfoundation.org> References: <20190520115249.449077487@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Will Deacon commit 75a19a0202db21638a1c2b424afb867e1f9a2376 upstream. When executing clock_gettime(), either in the vDSO or via a system call, we need to ensure that the read of the counter register occurs within the seqlock reader critical section. This ensures that updates to the clocksource parameters (e.g. the multiplier) are consistent with the counter value and therefore avoids the situation where time appears to go backwards across multiple reads. Extend the vDSO logic so that the seqlock critical section covers the read of the counter register as well as accesses to the data page. Since reads of the counter system registers are not ordered by memory barrier instructions, introduce dependency ordering from the counter read to a subsequent memory access so that the seqlock memory barriers apply to the counter access in both the vDSO and the system call paths. Cc: Cc: Marc Zyngier Tested-by: Vincenzo Frascino Link: https://lore.kernel.org/linux-arm-kernel/alpine.DEB.2.21.1902081950260.1662@nanos.tec.linutronix.de/ Reported-by: Thomas Gleixner Signed-off-by: Will Deacon Signed-off-by: Greg Kroah-Hartman --- arch/arm64/include/asm/arch_timer.h | 33 +++++++++++++++++++++++++++++++-- arch/arm64/kernel/vdso/gettimeofday.S | 15 +++++++++++---- 2 files changed, 42 insertions(+), 6 deletions(-) --- a/arch/arm64/include/asm/arch_timer.h +++ b/arch/arm64/include/asm/arch_timer.h @@ -148,18 +148,47 @@ static inline void arch_timer_set_cntkct isb(); } +/* + * Ensure that reads of the counter are treated the same as memory reads + * for the purposes of ordering by subsequent memory barriers. + * + * This insanity brought to you by speculative system register reads, + * out-of-order memory accesses, sequence locks and Thomas Gleixner. + * + * http://lists.infradead.org/pipermail/linux-arm-kernel/2019-February/631195.html + */ +#define arch_counter_enforce_ordering(val) do { \ + u64 tmp, _val = (val); \ + \ + asm volatile( \ + " eor %0, %1, %1\n" \ + " add %0, sp, %0\n" \ + " ldr xzr, [%0]" \ + : "=r" (tmp) : "r" (_val)); \ +} while (0) + static inline u64 arch_counter_get_cntpct(void) { + u64 cnt; + isb(); - return arch_timer_reg_read_stable(cntpct_el0); + cnt = arch_timer_reg_read_stable(cntpct_el0); + arch_counter_enforce_ordering(cnt); + return cnt; } static inline u64 arch_counter_get_cntvct(void) { + u64 cnt; + isb(); - return arch_timer_reg_read_stable(cntvct_el0); + cnt = arch_timer_reg_read_stable(cntvct_el0); + arch_counter_enforce_ordering(cnt); + return cnt; } +#undef arch_counter_enforce_ordering + static inline int arch_timer_arch_init(void) { return 0; --- a/arch/arm64/kernel/vdso/gettimeofday.S +++ b/arch/arm64/kernel/vdso/gettimeofday.S @@ -73,6 +73,13 @@ x_tmp .req x8 movn x_tmp, #0xff00, lsl #48 and \res, x_tmp, \res mul \res, \res, \mult + /* + * Fake address dependency from the value computed from the counter + * register to subsequent data page accesses so that the sequence + * locking also orders the read of the counter. + */ + and x_tmp, \res, xzr + add vdso_data, vdso_data, x_tmp .endm /* @@ -147,12 +154,12 @@ ENTRY(__kernel_gettimeofday) /* w11 = cs_mono_mult, w12 = cs_shift */ ldp w11, w12, [vdso_data, #VDSO_CS_MONO_MULT] ldp x13, x14, [vdso_data, #VDSO_XTIME_CLK_SEC] - seqcnt_check fail=1b get_nsec_per_sec res=x9 lsl x9, x9, x12 get_clock_shifted_nsec res=x15, cycle_last=x10, mult=x11 + seqcnt_check fail=1b get_ts_realtime res_sec=x10, res_nsec=x11, \ clock_nsec=x15, xtime_sec=x13, xtime_nsec=x14, nsec_to_sec=x9 @@ -211,13 +218,13 @@ realtime: /* w11 = cs_mono_mult, w12 = cs_shift */ ldp w11, w12, [vdso_data, #VDSO_CS_MONO_MULT] ldp x13, x14, [vdso_data, #VDSO_XTIME_CLK_SEC] - seqcnt_check fail=realtime /* All computations are done with left-shifted nsecs. */ get_nsec_per_sec res=x9 lsl x9, x9, x12 get_clock_shifted_nsec res=x15, cycle_last=x10, mult=x11 + seqcnt_check fail=realtime get_ts_realtime res_sec=x10, res_nsec=x11, \ clock_nsec=x15, xtime_sec=x13, xtime_nsec=x14, nsec_to_sec=x9 clock_gettime_return, shift=1 @@ -231,7 +238,6 @@ monotonic: ldp w11, w12, [vdso_data, #VDSO_CS_MONO_MULT] ldp x13, x14, [vdso_data, #VDSO_XTIME_CLK_SEC] ldp x3, x4, [vdso_data, #VDSO_WTM_CLK_SEC] - seqcnt_check fail=monotonic /* All computations are done with left-shifted nsecs. */ lsl x4, x4, x12 @@ -239,6 +245,7 @@ monotonic: lsl x9, x9, x12 get_clock_shifted_nsec res=x15, cycle_last=x10, mult=x11 + seqcnt_check fail=monotonic get_ts_realtime res_sec=x10, res_nsec=x11, \ clock_nsec=x15, xtime_sec=x13, xtime_nsec=x14, nsec_to_sec=x9 @@ -253,13 +260,13 @@ monotonic_raw: /* w11 = cs_raw_mult, w12 = cs_shift */ ldp w12, w11, [vdso_data, #VDSO_CS_SHIFT] ldp x13, x14, [vdso_data, #VDSO_RAW_TIME_SEC] - seqcnt_check fail=monotonic_raw /* All computations are done with left-shifted nsecs. */ get_nsec_per_sec res=x9 lsl x9, x9, x12 get_clock_shifted_nsec res=x15, cycle_last=x10, mult=x11 + seqcnt_check fail=monotonic_raw get_ts_clock_raw res_sec=x10, res_nsec=x11, \ clock_nsec=x15, nsec_to_sec=x9