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=-2.3 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no 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 A6B47CA9EAF for ; Mon, 21 Oct 2019 16:49:22 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 6CE112086D for ; Mon, 21 Oct 2019 16:49:22 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="ei0J4PjF" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6CE112086D Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=9jLl1g+lqh6BtbpZj5YNA002C1/5yZc/+yJOJxi3pt0=; b=ei0J4PjFu8meDR sdTFGra+nu/+655tJtgyiZfCX4vnJQCOwaTb4qPZ7CB/gn19dTKg5tDxni5jBegyJmdJp6Oc0dU7A co4626Tk50NQG1Mvt3PHLPFUIzb5dorYQYaw17P5+/QNhOTp1+5V8eupFK0I2Wy1Q94CmcvgT+O3i VsxmeYZpqPu+2lvNEBjswmC33iR0Ql0EOxTZhufkFoyIsniiXIT0a+jYBFOunhPlqUiXaJWbKqzuo pZuWqGcgD2bqq4ZM45luIzeLieoDEm3C7ta14YR2GJYIUrnRii3MNSqtdCNygu2f+viS3ajuLzlEb aKNrgSCHfhUUoMcvzNiQ==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1iMarx-0004OJ-TT; Mon, 21 Oct 2019 16:49:21 +0000 Received: from [217.140.110.172] (helo=foss.arm.com) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1iMarv-0004NY-7L for linux-arm-kernel@lists.infradead.org; Mon, 21 Oct 2019 16:49:20 +0000 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 AD150175A; Mon, 21 Oct 2019 09:49:08 -0700 (PDT) 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 E008A3F71F; Mon, 21 Oct 2019 09:49:06 -0700 (PDT) Date: Mon, 21 Oct 2019 17:49:04 +0100 From: Mark Rutland To: Sami Tolvanen Subject: Re: [PATCH 18/18] arm64: implement Shadow Call Stack Message-ID: <20191021164904.GD56589@lakrids.cambridge.arm.com> References: <20191018161033.261971-1-samitolvanen@google.com> <20191018161033.261971-19-samitolvanen@google.com> <20191018172309.GB18838@lakrids.cambridge.arm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.11.1+11 (2f07cb52) (2018-12-01) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20191021_094919_308494_8D84F5BE X-CRM114-Status: GOOD ( 14.74 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Kees Cook , Ard Biesheuvel , Catalin Marinas , Jann Horn , Nick Desaulniers , kernel list , Steven Rostedt , clang-built-linux , Kernel Hardening , Laura Abbott , Will Deacon , Dave Martin , linux-arm-kernel Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org Archived-At: List-Archive: On Fri, Oct 18, 2019 at 10:35:49AM -0700, Sami Tolvanen wrote: > On Fri, Oct 18, 2019 at 10:23 AM Mark Rutland wrote: > > I think scs_save() would better live in assembly in cpu_switch_to(), > > where we switch the stack and current. It shouldn't matter whether > > scs_load() is inlined or not, since the x18 value _should_ be invariant > > from the PoV of the task. > > Note that there's also a call to scs_save in cpu_die, because the > current task's shadow stack pointer is only stored in x18 and we don't > want to lose it. > > > We just need to add a TSK_TI_SCS to asm-offsets.c, and then insert a > > single LDR at the end: > > > > mov sp, x9 > > msr sp_el0, x1 > > #ifdef CONFIG_SHADOW_CALL_STACK > > ldr x18, [x1, TSK_TI_SCS] > > #endif > > ret > > TSK_TI_SCS is already defined, so yes, we could move this to > cpu_switch_to. I would still prefer to have the overflow check that's > in scs_thread_switch though. The only bit that I think needs to be in cpu_switch_to() is the install of the next task's shadow addr into x18. Having a separate scs_check_overflow() sounds fine to me, as that only has to read from the shadow stack. IIUC that's also for the prev task, not next, in the current patches. Thanks, Mark. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel