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=-9.8 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_GIT 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 4FC32C433DF for ; Wed, 27 May 2020 21:20:01 +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 F0075207E8 for ; Wed, 27 May 2020 21:20:00 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="ZXuTRZzs" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org F0075207E8 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:MIME-Version:Cc:List-Subscribe: List-Help:List-Post:List-Archive:List-Unsubscribe:List-Id: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=QEdp/mlBPIZIgXrLIO6UmBNko36InIYhxxUWVD9F6tw=; b=ZXuTRZzsHWICNCm/Bjgz4Hz2FK uZTVZkG1DrI7zw3B+bhW5RX9jmSTqunJRuWwVCMDbGQFd+e402RPTbJFlFPNZSkROMlAlG+HAj4o7 wSZFRieEKSR6lkqPeKepQzzWW7k/cEo3t/cHEmWsr8E6sN8sU3ZoBumMXJ9TmqIwC1Dr3x5iTiXR2 TwsDApf08adkYuALnAIwBtyeE8D7dpkURJEP67i5NYFxBJjPBacPnWYuek8TaCz4QYVl7fRY1wXSg Fh7zefaFS2yRTFeIRFFFkGjf9I7Eeg3e5O1Nwondg3WU9YZy1pFtQ5TvppF2V/dQ7Kbb+SsPdXkUP 90zuAj7g==; 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 1je3Sw-0002aY-NL; Wed, 27 May 2020 21:19:58 +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 1je3RZ-0001P8-42 for linux-arm-kernel@lists.infradead.org; Wed, 27 May 2020 21:18:37 +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 55ECB113E; Wed, 27 May 2020 14:18:32 -0700 (PDT) Received: from e103592.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 58DC83F52E; Wed, 27 May 2020 14:18:31 -0700 (PDT) From: Dave Martin To: Michael Kerrisk Subject: [RFC PATCH v2 6/6] prctl.2: Add tagged address ABI control prctls (arm64) Date: Wed, 27 May 2020 22:17:38 +0100 Message-Id: <1590614258-24728-7-git-send-email-Dave.Martin@arm.com> X-Mailer: git-send-email 2.1.4 In-Reply-To: <1590614258-24728-1-git-send-email-Dave.Martin@arm.com> References: <1590614258-24728-1-git-send-email-Dave.Martin@arm.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200527_141833_263126_F818B6F0 X-CRM114-Status: GOOD ( 14.93 ) 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-man@vger.kernel.org, Catalin Marinas , Vincenzo Frascino , Will Deacon , linux-arm-kernel@lists.infradead.org MIME-Version: 1.0 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 ** This patch is a draft for review and should not be applied before it has been discussed. ** Add documentation for the the PR_SET_TAGGED_ADDR_CTRL and PR_GET_TAGGED_ADDR_CTRL prctls added in Linux 5.4 for arm64. Signed-off-by: Dave Martin Cc: Catalin Marinas Cc: Will Deacon Cc: Vincenzo Frascino --- man2/prctl.2 | 156 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 156 insertions(+) diff --git a/man2/prctl.2 b/man2/prctl.2 index 3ee2702..062fd51 100644 --- a/man2/prctl.2 +++ b/man2/prctl.2 @@ -1504,6 +1504,143 @@ For more information, see the kernel source file (or .I Documentation/arm64/sve.txt before Linux 5.3). +.\" prctl PR_SET_TAGGED_ADDR_CTRL +.\" commit 63f0c60379650d82250f22e4cf4137ef3dc4f43d +.TP +.BR PR_SET_TAGGED_ADDR_CTRL " (since Linux 5.4, only on arm64)" +Controls support for passing tagged userspace addresses to the kernel +(i.e., addresses where bits 56\(em63 are not all zero). +.IP +The level of support is selected by +.IR "(unsigned int) arg2" , +which can be one of the following: +.RS +.TP +.B 0 +Addresses that are passed +for the purpose of being dereferenced by the kernel +must be untagged. +.TP +.B PR_TAGGED_ADDR_ENABLE +Addresses that are passed +for the purpose of being dereferenced by the kernel +may be tagged, with the exceptions summarized below. +.RE +.IP +The remaining arguments +.IR arg3 ", " arg4 " and " arg5 +must all be zero. +.IP +On success, the mode specified in +.I arg2 +is set for the calling thread and the the return value is 0. +If the arguments are invalid, +the mode specified in +.I arg2 +is unrecognized, +or if this feature is disabled or unsupported by the kernel, +the call fails with +.BR EINVAL . +.IP +In particular, if +.BR prctl ( PR_SET_TAGGED_ADDR_CTRL , +0, 0, 0, 0) +fails with +.B EINVAL +then all addresses passed to the kernel must be untagged. +.IP +Irrespective of which mode is set, +addresses passed to certain interfaces +must always be untagged: +.RS +.IP \(em +.BR brk (2), +.BR mmap (2), +.BR shmat (2), +and the +.I new_address +argument of +.BR mremap (2). +.IP +(Prior to Linux 5.6 these accepted tagged addresses, +but the behaviour may not be what you expect. +Don't rely on it.) +.IP \(em +\(oqpolymorphic\(cq interfaces +that accept pointers to arbitrary types cast to a +.I void * +or other generic type, specifically +.BR prctl (2), +.BR ioctl (2), +and in general +.BR setsockopt (2) +(only certain specific +.BR setsockopt (2) +options allow tagged addresses). +.IP \(em +.BR shmdt (2). +.RE +.IP +This list of exclusions may shrink +when moving from one kernel version to a later kernel version. +While the kernel may make some guarantees +for backwards compatibility reasons, +for the purposes of new software +the effect of passing tagged addresses to these interfaces +is unspecified. +.IP +The mode set by this call is inherited across +.BR fork (2) +and +.BR clone (2). +The mode is reset by +.BR execve (2) +to 0 +(i.e., tagged addresses not permitted in the user/kernel ABI). +.IP +.B Warning: +Because the compiler or run-time environment +may make use of address tagging, +a successful +.B PR_SET_TAGGED_ADDR_CTRL +may crash the calling process. +The conditions for using it safely are complex and system-dependent. +Don't use it unless you know what you are doing. +.IP +For more information, see the kernel source file +.IR Documentation/arm64/tagged\-address\-abi.rst . +.\" prctl PR_GET_TAGGED_ADDR_CTRL +.\" commit 63f0c60379650d82250f22e4cf4137ef3dc4f43d +.TP +.BR PR_GET_TAGGED_ADDR_CTRL " (since Linux 5.4, only on arm64)" +Returns the current tagged address mode +for the calling thread. +.IP +Arguments +.IR arg2 ", " arg3 ", " arg4 " and " arg5 +must all be zero. +.IP +If the arguments are invalid +or this feature is disabled or unsupported by the kernel, +the call fails with +.BR EINVAL . +In particular, if +.BR prctl ( PR_GET_TAGGED_ADDR_CTRL , +0, 0, 0, 0) +fails with +.BR EINVAL , +then this feature is definitely unsupported or disabled, +and all addresses passed to the kernel must be untagged. +.IP +Otherwise, the call returns a nonnegative value +describing the current tagged address mode, +encoded in the same way as the +.I arg2 +argument of +.BR PR_SET_TAGGED_ADDR_CTRL . +.IP +For more information, see the kernel source file +.IR Documentation/arm64/tagged\-address\-abi.rst . .\" .\" prctl PR_TASK_PERF_EVENTS_DISABLE .TP @@ -1749,6 +1886,7 @@ On success, .BR PR_GET_SPECULATION_CTRL , .BR PR_SVE_GET_VL , .BR PR_SVE_SET_VL , +.BR PR_GET_TAGGED_ADDR_CTRL , .BR PR_GET_THP_DISABLE , .BR PR_GET_TIMING , .BR PR_GET_TIMERSLACK , @@ -2057,6 +2195,24 @@ is .B PR_SVE_GET_VL and SVE is not available on this platform. .TP +.B EINVAL +.I option +is +.BR PR_SET_TAGGED_ADDR_CTRL +and the arguments are invalid or unsupported. +See the description of +.B PR_SET_TAGGED_ADDR_CTRL +above for details. +.TP +.B EINVAL +.I option +is +.BR PR_GET_TAGGED_ADDR_CTRL +and the arguments are invalid or unsupported. +See the description of +.B PR_GET_TAGGED_ADDR_CTRL +above for details. +.TP .B ENODEV .I option was -- 2.1.4 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org 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