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=-6.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 D41FBC2D0A3 for ; Mon, 16 Nov 2020 19:02:07 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (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 65C4D206C0 for ; Mon, 16 Nov 2020 19:02:06 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="Q3uDyknz" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 65C4D206C0 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+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=merlin.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=byjZsvAJqFP6R5ZzdyhMp9qkoUUwGTh49UoligFPu18=; b=Q3uDyknzIVf9TMyxpIGucw3pi 90cxE0sSWQpHm61ochYf3fiy/7LJTp0FsvmHyMQoHUevgZn9iqbOg7b/HQ0SKSEiZn1N1LqVgmdy9 xTL141kvgvzCmE4In2fbnmv3QwvM9eybjG98XsFOmpGd9PR8LGCGzBb+PjtyQ9Rvmz+yiMxHCPpPg 9cbteJEHM6XBR6MsifbGQ8jaYqORsUj3SqPLwx3NVcLxTi6z6lf2YubB34HfioVABv2FFmE3yHeVr JQ6xr7fvzobF74Jyn0PB8eHbL6pM3kmfcIA462FLiS8tXUdu4MxND8On36VxDQrnHmH2kXzHzwZ34 rxAxc7DIQ==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1kejkl-0003ve-Rp; Mon, 16 Nov 2020 19:01:27 +0000 Received: from mail.kernel.org ([198.145.29.99]) by merlin.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1kejkj-0003vJ-5Q for linux-arm-kernel@lists.infradead.org; Mon, 16 Nov 2020 19:01:26 +0000 Received: from trantor (unknown [2.26.170.190]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 69FBA206A1; Mon, 16 Nov 2020 19:01:21 +0000 (UTC) Date: Mon, 16 Nov 2020 19:01:18 +0000 From: Catalin Marinas To: Peter Collingbourne Subject: Re: [PATCH v16 6/6] arm64: expose FAR_EL1 tag bits in siginfo Message-ID: References: <81e1307108ca8ea67aa1060f6f47b34a507410f1.1605235762.git.pcc@google.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <81e1307108ca8ea67aa1060f6f47b34a507410f1.1605235762.git.pcc@google.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20201116_140125_314530_1B7FAEBC X-CRM114-Status: GOOD ( 22.02 ) 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 ARM , Andrey Konovalov , Helge Deller , Kevin Brodsky , Oleg Nesterov , "James E.J. Bottomley" , Kostya Serebryany , "Eric W. Biederman" , linux-api@vger.kernel.org, David Spickett , Vincenzo Frascino , Will Deacon , Dave Martin , Evgenii Stepanov Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Thu, Nov 12, 2020 at 06:53:36PM -0800, Peter Collingbourne wrote: > diff --git a/Documentation/arm64/tagged-pointers.rst b/Documentation/arm64/tagged-pointers.rst > index eab4323609b9..19d284b70384 100644 > --- a/Documentation/arm64/tagged-pointers.rst > +++ b/Documentation/arm64/tagged-pointers.rst > @@ -53,12 +53,25 @@ visibility. > Preserving tags > --------------- > > -Non-zero tags are not preserved when delivering signals. This means that > -signal handlers in applications making use of tags cannot rely on the > -tag information for user virtual addresses being maintained for fields > -inside siginfo_t. One exception to this rule is for signals raised in > -response to watchpoint debug exceptions, where the tag information will > -be preserved. > +When delivering signals, non-zero tags are not preserved in > +siginfo.si_addr unless the flag SA_EXPOSE_TAGBITS was set in > +sigaction.sa_flags when the signal handler was installed. This means > +that signal handlers in applications making use of tags cannot rely > +on the tag information for user virtual addresses being maintained > +in these fields unless the flag was set. > + > +Due to architecture limitations, bits 63:60 of the fault address > +are not preserved in response to synchronous tag check faults > +(SEGV_MTESERR) even if SA_EXPOSE_TAGBITS was set. Applications should > +treat the values of these bits as undefined in order to accommodate > +future architecture revisions which may preserve the bits. If future architecture versions will preserve these bits, most likely we'll add a new HWCAP bit so that the user knows what's going on. But the user shouldn't rely on them being 0, just in case. > +For signals raised in response to watchpoint debug exceptions, the > +tag information will be preserved regardless of the SA_EXPOSE_TAGBITS > +flag setting. > + > +Non-zero tags are never preserved in sigcontext.fault_address > +regardless of the SA_EXPOSE_TAGBITS flag setting. We could've done it the other way around (fault_address tagged, si_addr untagged) but that would be specific to arm64, so I think we should solve it for other architectures that implement (or plan to) tagging. The fault_address in the arm64 sigcontext was an oversight, we should have removed it but when we realised it was already ABI. Anyway, I'm fine with the arm64 changes here: Reviewed-by: Catalin Marinas With Eric's ack, I'm happy to take the series through the arm64 tree, otherwise Eric's tree is fine as well. Thanks. -- Catalin _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel