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=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 7280BCA9ECF for ; Mon, 4 Nov 2019 17:05:08 +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 38F9E2080F for ; Mon, 4 Nov 2019 17:05:08 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="gC7r3Ii8" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 38F9E2080F 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=bZ5grUOThjcyXrtly8dBa5NOeuOAJr4ifaj17ORsPCc=; b=gC7r3Ii8+OmqKT dadFjvM7ypS4ZEjE6nzILGHs6br47L04dOnaEgB1z7YhdJG4A+5IBeaGNbZP8w2GHdIYMJur6NUq7 e1Z1hK+qIqtm9QTCbpCzoyciEbZluIq72JqeBmSa7w8fJCkqhjnP7PZOJqam06lxi3NDJ6+RkueUQ Z6PeiP23rOsEo7vjP4jLJLRikX1eWJc88hLBodiFXn4v+iOSRz+X48EyiBhCYECxJ4Zry7hQoJU0Z lTocccsIA06eE8AMyeNomCm4535MstVrItwGzD5JG3mguLdCTHKlJ3g2uOiJU7c4Mpc3JQHuBXP58 w7ZqqAtyi+5pDhZCjvnw==; 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 1iRfmt-0004WU-Fw; Mon, 04 Nov 2019 17:05:07 +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 1iRfmp-0004Ea-VD for linux-arm-kernel@lists.infradead.org; Mon, 04 Nov 2019 17:05:05 +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 9992D1F1; Mon, 4 Nov 2019 09:05:02 -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 605073F71A; Mon, 4 Nov 2019 09:05:00 -0800 (PST) Date: Mon, 4 Nov 2019 17:04:54 +0000 From: Mark Rutland To: Sami Tolvanen Subject: Re: [PATCH v4 10/17] arm64: disable kretprobes with SCS Message-ID: <20191104170454.GA2024@lakrids.cambridge.arm.com> References: <20191018161033.261971-1-samitolvanen@google.com> <20191101221150.116536-1-samitolvanen@google.com> <20191101221150.116536-11-samitolvanen@google.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20191101221150.116536-11-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-20191104_090504_050450_AC786CAF X-CRM114-Status: GOOD ( 18.55 ) 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, 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 Fri, Nov 01, 2019 at 03:11:43PM -0700, Sami Tolvanen wrote: > With CONFIG_KRETPROBES, function return addresses are modified to > redirect control flow to kretprobe_trampoline. This is incompatible > with SCS. I'm a bit confused as to why that's the case -- could you please elaborate on how this is incompatible? IIUC kretrobes works by patching the function entry point with a BRK, so that it can modify the LR _before_ it is saved to the stack. I don't see how SCS affects that. When the instrumented function returns, it'll balance its SCS state, then "return" to kretprobe_trampoline. Since kretprobe_trampoline is plain assembly, it doesn't have SCS, and can modify the LR live, as it does. So functionally, that appears to work. What am I missing? Thanks, Mark. > Signed-off-by: Sami Tolvanen > Reviewed-by: Kees Cook > --- > arch/arm64/Kconfig | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig > index 3f047afb982c..e7b57a8a5531 100644 > --- a/arch/arm64/Kconfig > +++ b/arch/arm64/Kconfig > @@ -165,7 +165,7 @@ config ARM64 > select HAVE_STACKPROTECTOR > select HAVE_SYSCALL_TRACEPOINTS > select HAVE_KPROBES > - select HAVE_KRETPROBES > + select HAVE_KRETPROBES if !SHADOW_CALL_STACK > select HAVE_GENERIC_VDSO > select IOMMU_DMA if IOMMU_SUPPORT > select IRQ_DOMAIN > -- > 2.24.0.rc1.363.gb1bccd3e3d-goog > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel