From patchwork Fri Aug 23 16:37:17 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Catalin Marinas X-Patchwork-Id: 11112077 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 1FE2A1399 for ; Fri, 23 Aug 2019 16:37:28 +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 EF2772339D for ; Fri, 23 Aug 2019 16:37:27 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="cUGBQ93H" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org EF2772339D 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+patchwork-linux-arm=patchwork.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:MIME-Version:References:In-Reply-To: Message-Id:Date:Subject:To:From:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=81K0jEJhwLJLQqlbDjEFAGhkGR9iDZ6hWS8TAVg5U64=; b=cUGBQ93HM7lNNX WvQowoXKmlm3QXyiSWniZgZWfQet/Y6mypLzPg29hTv+kWPfiMtiV2NxOZ23JEq5cCtq1lugySPUY RYnEgCseTGBI3ieh863KDeu14c0xeGfW/Vr+ZhQbtDUq5UJErDIfKv17El02aO9xMZkE32WgKXWpF l9NPRz5KUBWSymRmYgCQuWfum7LAKbMmUD5QOuV3OJi4UEtFPye4CLEplv7snPUhOirOmBiEq84h3 w2uRbNpGNA66FA1PFDKnng+x4reioXjdYZUMX+BgpRsOzkM0ojNQb5itz3FfL/aOe+UTeml3Xwy5l 9o0beLk6Z9F/noB0DfPw==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92 #3 (Red Hat Linux)) id 1i1CZ5-0003Yd-Ef; Fri, 23 Aug 2019 16:37:27 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.92 #3 (Red Hat Linux)) id 1i1CZ2-0003XY-Jb for linux-arm-kernel@lists.infradead.org; Fri, 23 Aug 2019 16:37:26 +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 44B021570; Fri, 23 Aug 2019 09:37:24 -0700 (PDT) Received: from arrakis.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.121.207.14]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 75CAC3F246; Fri, 23 Aug 2019 09:37:22 -0700 (PDT) From: Catalin Marinas To: linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org Subject: [PATCH v10 1/1] arm64: Relax Documentation/arm64/tagged-pointers.rst Date: Fri, 23 Aug 2019 17:37:17 +0100 Message-Id: <20190823163717.19569-2-catalin.marinas@arm.com> X-Mailer: git-send-email 2.23.0.rc0 In-Reply-To: <20190823163717.19569-1-catalin.marinas@arm.com> References: <20190823163717.19569-1-catalin.marinas@arm.com> MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190823_093724_736543_E0DB1871 X-CRM114-Status: GOOD ( 10.77 ) X-Spam-Score: 0.0 (/) X-Spam-Report: SpamAssassin version 3.4.2 on bombadil.infradead.org summary: Content analysis details: (0.0 points) pts rule name description ---- ---------------------- -------------------------------------------------- 0.0 SPF_HELO_NONE SPF: HELO does not publish an SPF Record -0.0 SPF_PASS SPF: sender matches SPF record 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: linux-arch@vger.kernel.org, linux-doc@vger.kernel.org, Szabolcs Nagy , Andrey Konovalov , Kevin Brodsky , Will Deacon , Dave Hansen , Andrew Morton , Vincenzo Frascino , Will Deacon , Dave P Martin Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org From: Vincenzo Frascino On AArch64 the TCR_EL1.TBI0 bit is set by default, allowing userspace (EL0) to perform memory accesses through 64-bit pointers with a non-zero top byte. However, such pointers were not allowed at the user-kernel syscall ABI boundary. With the Tagged Address ABI patchset, it is now possible to pass tagged pointers to the syscalls. Relax the requirements described in tagged-pointers.rst to be compliant with the behaviours guaranteed by the AArch64 Tagged Address ABI. Cc: Will Deacon Cc: Szabolcs Nagy Cc: Kevin Brodsky Acked-by: Andrey Konovalov Signed-off-by: Vincenzo Frascino Co-developed-by: Catalin Marinas Signed-off-by: Catalin Marinas --- Documentation/arm64/tagged-pointers.rst | 21 ++++++++++++++------- 1 file changed, 14 insertions(+), 7 deletions(-) diff --git a/Documentation/arm64/tagged-pointers.rst b/Documentation/arm64/tagged-pointers.rst index 2acdec3ebbeb..eab4323609b9 100644 --- a/Documentation/arm64/tagged-pointers.rst +++ b/Documentation/arm64/tagged-pointers.rst @@ -20,7 +20,9 @@ Passing tagged addresses to the kernel -------------------------------------- All interpretation of userspace memory addresses by the kernel assumes -an address tag of 0x00. +an address tag of 0x00, unless the application enables the AArch64 +Tagged Address ABI explicitly +(Documentation/arm64/tagged-address-abi.rst). This includes, but is not limited to, addresses found in: @@ -33,13 +35,15 @@ This includes, but is not limited to, addresses found in: - the frame pointer (x29) and frame records, e.g. when interpreting them to generate a backtrace or call graph. -Using non-zero address tags in any of these locations may result in an -error code being returned, a (fatal) signal being raised, or other modes -of failure. +Using non-zero address tags in any of these locations when the +userspace application did not enable the AArch64 Tagged Address ABI may +result in an error code being returned, a (fatal) signal being raised, +or other modes of failure. -For these reasons, passing non-zero address tags to the kernel via -system calls is forbidden, and using a non-zero address tag for sp is -strongly discouraged. +For these reasons, when the AArch64 Tagged Address ABI is disabled, +passing non-zero address tags to the kernel via system calls is +forbidden, and using a non-zero address tag for sp is strongly +discouraged. Programs maintaining a frame pointer and frame records that use non-zero address tags may suffer impaired or inaccurate debug and profiling @@ -59,6 +63,9 @@ be preserved. The architecture prevents the use of a tagged PC, so the upper byte will be set to a sign-extension of bit 55 on exception return. +This behaviour is maintained when the AArch64 Tagged Address ABI is +enabled. + Other considerations --------------------