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, URIBL_BLOCKED,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 77858C34047 for ; Wed, 19 Feb 2020 11:34:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5A49C21D56 for ; Wed, 19 Feb 2020 11:34:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727171AbgBSLeE (ORCPT ); Wed, 19 Feb 2020 06:34:04 -0500 Received: from foss.arm.com ([217.140.110.172]:46970 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727069AbgBSLeE (ORCPT ); Wed, 19 Feb 2020 06:34:04 -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 D7CD631B; Wed, 19 Feb 2020 03:34:03 -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 8AF023F6CF; Wed, 19 Feb 2020 03:34:01 -0800 (PST) Date: Wed, 19 Feb 2020 11:33:52 +0000 From: Mark Rutland To: Sami Tolvanen Cc: Will Deacon , Catalin Marinas , Steven Rostedt , Masami Hiramatsu , Ard Biesheuvel , james.morse@arm.com, Dave Martin , Kees Cook , Laura Abbott , Marc Zyngier , Nick Desaulniers , Jann Horn , Miguel Ojeda , Masahiro Yamada , clang-built-linux@googlegroups.com, kernel-hardening@lists.openwall.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v8 04/12] scs: disable when function graph tracing is enabled Message-ID: <20200219113351.GA14462@lakrids.cambridge.arm.com> References: <20191018161033.261971-1-samitolvanen@google.com> <20200219000817.195049-1-samitolvanen@google.com> <20200219000817.195049-5-samitolvanen@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200219000817.195049-5-samitolvanen@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 Tue, Feb 18, 2020 at 04:08:09PM -0800, Sami Tolvanen wrote: > The graph tracer hooks returns by modifying frame records on the > (regular) stack, but with SCS the return address is taken from the > shadow stack, and the value in the frame record has no effect. As we > don't currently have a mechanism to determine the corresponding slot > on the shadow stack (and to pass this through the ftrace > infrastructure), for now let's disable SCS when the graph tracer is > enabled. > > Signed-off-by: Sami Tolvanen > Reviewed-by: Kees Cook > --- > arch/Kconfig | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/arch/Kconfig b/arch/Kconfig > index 66b34fd0df54..4102b8e0eea9 100644 > --- a/arch/Kconfig > +++ b/arch/Kconfig > @@ -535,6 +535,7 @@ config ARCH_SUPPORTS_SHADOW_CALL_STACK > > config SHADOW_CALL_STACK > bool "Clang Shadow Call Stack" > + depends on !FUNCTION_GRAPH_TRACER Fangrui Song has implemented `-fpatchable-function-entry` in LLVM (for 10.x onwards), so we can support this when DYNAMIC_FTRACE_WITH_REGS is selected. This can be: depends on DYNAMIC_FTRACE_WITH_REGS || !FUNCTION_GRAPH_TRACER ... and we can update the commit message to something like: | With SCS the return address is taken from the shadow stack and the | value in the frame record has no effect. The mcount based graph tracer | hooks returns by modifying frame records on the (regular) stack, and | thus is not compatible. The patchable-function-entry graph tracer | used for DYNAMIC_FTRACE_WITH_REGS modifies the LR before it is saved | to the shadow stack, and is compatible. | | Modifying the mcount based graph tracer to work with SCS would require | a mechanism to determine the corresponding slot on the shadow stack | (and to pass this through the ftrace infrastructure), and we expect | that everyone will eventually move to the patchable-function-entry | based graph tracer anyway, so for now let's disable SCS when the | mcount-based graph tracer is enabled. | | SCS and patchable-function-entry are both supported from LLVM 10.x. Assuming you're happy with that: Reviewed-by: Mark Rutland Thanks, Mark. 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=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 D020FC34047 for ; Wed, 19 Feb 2020 11:34:17 +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 3E4DE21D56 for ; Wed, 19 Feb 2020 11:34:17 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="Y2ztuh8y" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3E4DE21D56 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=Gc34Lcf1Se7lAOuDipIV5RMVdn1R/Dk9hrtLvvO/ADk=; b=Y2ztuh8yT5HNga xia2pbKuCay+UqBI4zZ9VwB+J2BglAP2unKlfIRbCw421bvOoDjKHkL9/loC4RX20GTn3aTOPPjii vyt3RLiiyTvy55iMr0cgdAG6BWsgptnGN8lYC6ajizBbJQxTzS0I0hxIPNuJPs027NQnLtXQKPJVV 5JpQz7RQrLrsEDgB9Fb0yYYXTbnRGVzEr5RgkYB+ZDD0z4UW92QcN9mVEufO/DoOOfVY9Wg/s8WsN az2fKxL2aCQEXPHI8qA22O6ZtdKfyiRxY64Ib6AlmHJgSZGzLHp/P7HR87F+JFmQrKH0cIoo40yT4 neR5u6tfO3p7w1NgFatQ==; 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 1j4NcG-0004vc-9R; Wed, 19 Feb 2020 11:34:08 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1j4NcC-0004rL-JA for linux-arm-kernel@lists.infradead.org; Wed, 19 Feb 2020 11:34:06 +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 D7CD631B; Wed, 19 Feb 2020 03:34:03 -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 8AF023F6CF; Wed, 19 Feb 2020 03:34:01 -0800 (PST) Date: Wed, 19 Feb 2020 11:33:52 +0000 From: Mark Rutland To: Sami Tolvanen Subject: Re: [PATCH v8 04/12] scs: disable when function graph tracing is enabled Message-ID: <20200219113351.GA14462@lakrids.cambridge.arm.com> References: <20191018161033.261971-1-samitolvanen@google.com> <20200219000817.195049-1-samitolvanen@google.com> <20200219000817.195049-5-samitolvanen@google.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20200219000817.195049-5-samitolvanen@google.com> 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-20200219_033404_700820_32C70417 X-CRM114-Status: GOOD ( 20.21 ) 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 , Masahiro Yamada , Catalin Marinas , Jann Horn , Nick Desaulniers , linux-kernel@vger.kernel.org, Steven Rostedt , Miguel Ojeda , clang-built-linux@googlegroups.com, james.morse@arm.com, Masami Hiramatsu , Marc Zyngier , kernel-hardening@lists.openwall.com, Laura Abbott , Will Deacon , Dave Martin , linux-arm-kernel@lists.infradead.org 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 On Tue, Feb 18, 2020 at 04:08:09PM -0800, Sami Tolvanen wrote: > The graph tracer hooks returns by modifying frame records on the > (regular) stack, but with SCS the return address is taken from the > shadow stack, and the value in the frame record has no effect. As we > don't currently have a mechanism to determine the corresponding slot > on the shadow stack (and to pass this through the ftrace > infrastructure), for now let's disable SCS when the graph tracer is > enabled. > > Signed-off-by: Sami Tolvanen > Reviewed-by: Kees Cook > --- > arch/Kconfig | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/arch/Kconfig b/arch/Kconfig > index 66b34fd0df54..4102b8e0eea9 100644 > --- a/arch/Kconfig > +++ b/arch/Kconfig > @@ -535,6 +535,7 @@ config ARCH_SUPPORTS_SHADOW_CALL_STACK > > config SHADOW_CALL_STACK > bool "Clang Shadow Call Stack" > + depends on !FUNCTION_GRAPH_TRACER Fangrui Song has implemented `-fpatchable-function-entry` in LLVM (for 10.x onwards), so we can support this when DYNAMIC_FTRACE_WITH_REGS is selected. This can be: depends on DYNAMIC_FTRACE_WITH_REGS || !FUNCTION_GRAPH_TRACER ... and we can update the commit message to something like: | With SCS the return address is taken from the shadow stack and the | value in the frame record has no effect. The mcount based graph tracer | hooks returns by modifying frame records on the (regular) stack, and | thus is not compatible. The patchable-function-entry graph tracer | used for DYNAMIC_FTRACE_WITH_REGS modifies the LR before it is saved | to the shadow stack, and is compatible. | | Modifying the mcount based graph tracer to work with SCS would require | a mechanism to determine the corresponding slot on the shadow stack | (and to pass this through the ftrace infrastructure), and we expect | that everyone will eventually move to the patchable-function-entry | based graph tracer anyway, so for now let's disable SCS when the | mcount-based graph tracer is enabled. | | SCS and patchable-function-entry are both supported from LLVM 10.x. Assuming you're happy with that: Reviewed-by: Mark Rutland Thanks, Mark. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel