From patchwork Mon Apr 22 16:49:29 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Julien Grall X-Patchwork-Id: 10911273 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id CB1241708 for ; Mon, 22 Apr 2019 16:51:45 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id BDD3D285CC for ; Mon, 22 Apr 2019 16:51:45 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id B2598285E5; Mon, 22 Apr 2019 16:51:45 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.2 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI, RCVD_IN_DNSWL_MED autolearn=ham version=3.3.1 Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (using TLSv1.2 with cipher AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id 5CF25285E0 for ; Mon, 22 Apr 2019 16:51:45 +0000 (UTC) Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.89) (envelope-from ) id 1hIc8v-00058o-O4; Mon, 22 Apr 2019 16:50:09 +0000 Received: from us1-rack-dfw2.inumbo.com ([104.130.134.6]) by lists.xenproject.org with esmtp (Exim 4.89) (envelope-from ) id 1hIc8u-00054g-FK for xen-devel@lists.xenproject.org; Mon, 22 Apr 2019 16:50:08 +0000 X-Inumbo-ID: af2501c1-651e-11e9-92d7-bc764e045a96 Received: from foss.arm.com (unknown [217.140.101.70]) by us1-rack-dfw2.inumbo.com (Halon) with ESMTP id af2501c1-651e-11e9-92d7-bc764e045a96; Mon, 22 Apr 2019 16:50:07 +0000 (UTC) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 3A0B615AB; Mon, 22 Apr 2019 09:50:07 -0700 (PDT) Received: from e108454-lin.cambridge.arm.com (e108454-lin.cambridge.arm.com [10.1.196.50]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 2A9B43F557; Mon, 22 Apr 2019 09:50:06 -0700 (PDT) From: Julien Grall To: xen-devel@lists.xenproject.org Date: Mon, 22 Apr 2019 17:49:29 +0100 Message-Id: <20190422164937.21350-13-julien.grall@arm.com> X-Mailer: git-send-email 2.11.0 In-Reply-To: <20190422164937.21350-1-julien.grall@arm.com> References: <20190422164937.21350-1-julien.grall@arm.com> Subject: [Xen-devel] [PATCH 12/20] xen/arm32: head: Always zero r3 before update a page-table entry X-BeenThere: xen-devel@lists.xenproject.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Cc: Oleksandr_Tyshchenko@epam.com, Julien Grall , sstabellini@kernel.org, Andrii_Anisov@epam.com MIME-Version: 1.0 Errors-To: xen-devel-bounces@lists.xenproject.org Sender: "Xen-devel" X-Virus-Scanned: ClamAV using ClamSMTP The boot code is using r2 and r3 to hold the page-table entry value. While r2 is always updated before storing the value, this is not always the case for r3. Thankfully today, r3 will always be zero when we care. But this is difficult to track and error-prone. So always zero r3 within the few instructions before the write the page-table entry. Signed-off-by: Julien Grall Reviewed-by: Andrii Anisov --- xen/arch/arm/arm32/head.S | 3 +++ 1 file changed, 3 insertions(+) diff --git a/xen/arch/arm/arm32/head.S b/xen/arch/arm/arm32/head.S index 3448817aab..0536b62aec 100644 --- a/xen/arch/arm/arm32/head.S +++ b/xen/arch/arm/arm32/head.S @@ -270,6 +270,7 @@ cpu_init_done: orr r2, r2, #PT_UPPER(MEM) /* r2:r3 := section map */ orr r2, r2, #PT_LOWER(MEM) lsl r1, r1, #3 /* r1 := Slot offset */ + mov r3, #0x0 strd r2, r3, [r4, r1] /* Mapping of paddr(start) */ mov r6, #1 /* r6 := identity map now in place */ @@ -377,6 +378,7 @@ paging: lsl r2, r2, #THIRD_SHIFT /* 4K aligned paddr of UART */ orr r2, r2, #PT_UPPER(DEV_L3) orr r2, r2, #PT_LOWER(DEV_L3) /* r2:r3 := 4K dev map including UART */ + mov r3, #0 strd r2, r3, [r1, #(FIXMAP_CONSOLE*8)] /* Map it in the first fixmap's slot */ 1: @@ -388,6 +390,7 @@ paging: orr r2, r2, #PT_LOWER(PT) /* r2:r3 := table map of xen_fixmap */ ldr r4, =FIXMAP_ADDR(0) mov r4, r4, lsr #(SECOND_SHIFT - 3) /* r4 := Slot for FIXMAP(0) */ + mov r3, #0 strd r2, r3, [r1, r4] /* Map it in the fixmap's slot */ /* Use a virtual address to access the UART. */