From patchwork Fri Mar 15 19:51:37 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andrey Konovalov X-Patchwork-Id: 1057224 X-Patchwork-Delegate: davem@davemloft.net Return-Path: X-Original-To: patchwork-incoming-netdev@ozlabs.org Delivered-To: patchwork-incoming-netdev@ozlabs.org Authentication-Results: ozlabs.org; spf=none (mailfrom) smtp.mailfrom=vger.kernel.org (client-ip=209.132.180.67; helo=vger.kernel.org; envelope-from=netdev-owner@vger.kernel.org; receiver=) Authentication-Results: ozlabs.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: ozlabs.org; dkim=pass (2048-bit key; unprotected) header.d=google.com header.i=@google.com header.b="m8TjLlxT"; dkim-atps=neutral Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 44LbpV2xX1z9s71 for ; Sat, 16 Mar 2019 06:52:50 +1100 (AEDT) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727635AbfCOTwp (ORCPT ); Fri, 15 Mar 2019 15:52:45 -0400 Received: from mail-yw1-f74.google.com ([209.85.161.74]:43195 "EHLO mail-yw1-f74.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727569AbfCOTwZ (ORCPT ); Fri, 15 Mar 2019 15:52:25 -0400 Received: by mail-yw1-f74.google.com with SMTP id r8so13108064ywh.10 for ; Fri, 15 Mar 2019 12:52:25 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:in-reply-to:message-id:mime-version:references:subject:from:to :cc; bh=sAfWvHiPwt89rwowuJd122MWpb2hIcncHtjST15rjKY=; b=m8TjLlxTJg+rOoEWUReYdn8rdh11EMoghrFHbVAb9WAMjVa0U/T9FqdGOvqwTZpUfm vVbcFLqWrP3TVwdj34DrYszJNIoQ9EJXeAXrC/wvs/z5IYKQAqYP9RwBD+8emDJu5PVP Vo+huuqc6PHspT4+rXUR6NPieF9KLiWfhrJ7gi13d3MatbDKM4RF0bkO2DrrarQnmyYR 3h3NjRcSXCNOJ75ka4ui6zatbnk/g1PfEFqJlZRnqOTJFOnY1jqqoDx3fG9sQrGexBtX ZZ96/DuknTpKXEYqtVY62yQBCWP1T+ifr5PT3FJRXj7RVMG+M4Fgps93zJ4tkNbNYwin RjCQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=sAfWvHiPwt89rwowuJd122MWpb2hIcncHtjST15rjKY=; b=drOJpGQHdZMzUBHg9Z1weY4TaE0pjKEToX80FU6HizUzB64FtuthaN/NYkETG+DyXi AJZcHZQ65Gf4RThJh+8z1tCZ73bJ8ZEpDS6Y1NBRj/dc8/CGk4SVZaehuWo0dGK8zLxy s8Wo5eKJOVjnNeXnbyYCzyzpAuW4leJ1LGt2XQjwERENrWjrANSH9IW10ppl5d3xw0t4 Tbr/cmlBqCdbCxB4GK9CJrwjdpnBdhKGjEOTbU7VLnfs4WQrEInhO7IYIIglyQu5/ghx 2bUniBde2U45WHobzhahgYbHHhmj3viCqgMoTtmD5xHolsEE1+a299lUIztW45HDk9yp gx3w== X-Gm-Message-State: APjAAAU0wY/SrZsnMf8s4DW0nzbFRWfUYvYCoeJHUbl166kDYyrd55Bc A2HPU6cA+ZpRxPCfjmxVcY3xwtbAcsuIF44L X-Google-Smtp-Source: APXvYqx6fJ/Xf2Wycfnq24ZgFIr73HZ4gPKerA6ul2fF+VVXr0NweKm2RI8g9OR3XNR3hwcUmUxVL0qXK1MAydWo X-Received: by 2002:a25:41c2:: with SMTP id o185mr2528725yba.96.1552679544923; Fri, 15 Mar 2019 12:52:24 -0700 (PDT) Date: Fri, 15 Mar 2019 20:51:37 +0100 In-Reply-To: Message-Id: Mime-Version: 1.0 References: X-Mailer: git-send-email 2.21.0.360.g471c308f928-goog Subject: [PATCH v11 13/14] arm64: update Documentation/arm64/tagged-pointers.txt From: Andrey Konovalov To: Catalin Marinas , Will Deacon , Mark Rutland , Robin Murphy , Kees Cook , Kate Stewart , Greg Kroah-Hartman , Andrew Morton , Ingo Molnar , "Kirill A . Shutemov" , Shuah Khan , Vincenzo Frascino , Eric Dumazet , "David S. Miller" , Alexei Starovoitov , Daniel Borkmann , Steven Rostedt , Ingo Molnar , Peter Zijlstra , Arnaldo Carvalho de Melo , linux-arm-kernel@lists.infradead.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, linux-arch@vger.kernel.org, netdev@vger.kernel.org, bpf@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Dmitry Vyukov , Kostya Serebryany , Evgeniy Stepanov , Lee Smith , Ramana Radhakrishnan , Jacob Bramley , Ruben Ayrapetyan , Chintan Pandya , Luc Van Oostenryck , Dave Martin , Kevin Brodsky , Szabolcs Nagy , Andrey Konovalov Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org This patch is a part of a series that extends arm64 kernel ABI to allow to pass tagged user pointers (with the top byte set to something else other than 0x00) as syscall arguments. Document the ABI changes in Documentation/arm64/tagged-pointers.txt. Signed-off-by: Andrey Konovalov --- Documentation/arm64/tagged-pointers.txt | 18 ++++++++---------- 1 file changed, 8 insertions(+), 10 deletions(-) diff --git a/Documentation/arm64/tagged-pointers.txt b/Documentation/arm64/tagged-pointers.txt index a25a99e82bb1..07fdddeacad0 100644 --- a/Documentation/arm64/tagged-pointers.txt +++ b/Documentation/arm64/tagged-pointers.txt @@ -17,13 +17,15 @@ this byte for application use. Passing tagged addresses to the kernel -------------------------------------- -All interpretation of userspace memory addresses by the kernel assumes -an address tag of 0x00. +The kernel supports tags in pointer arguments (including pointers in +structures) of syscalls, however such pointers must point to memory ranges +obtained by anonymous mmap() or brk(). -This includes, but is not limited to, addresses found in: +The kernel supports tags in user fault addresses. However the fault_address +field in the sigcontext struct will contain an untagged address. - - pointer arguments to system calls, including pointers in structures - passed to system calls, +All other interpretations of userspace memory addresses by the kernel +assume an address tag of 0x00, in particular: - the stack pointer (sp), e.g. when interpreting it to deliver a signal, @@ -33,11 +35,7 @@ This includes, but is not limited to, addresses found in: 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. - -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. +of failure. 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