From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wr1-f68.google.com ([209.85.221.68]:35955 "EHLO mail-wr1-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728110AbeJBT4O (ORCPT ); Tue, 2 Oct 2018 15:56:14 -0400 Received: by mail-wr1-f68.google.com with SMTP id y16so2179296wrw.3 for ; Tue, 02 Oct 2018 06:12:57 -0700 (PDT) From: Andrey Konovalov Subject: [PATCH v7 7/8] arm64: update Documentation/arm64/tagged-pointers.txt Date: Tue, 2 Oct 2018 15:12:42 +0200 Message-ID: <47a464307d4df3c0cb65f88d1fe83f9a741dd74b.1538485901.git.andreyknvl@google.com> In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-arch-owner@vger.kernel.org List-ID: 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 , linux-arm-kernel@lists.infradead.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, linux-arch@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 , Andrey Konovalov Message-ID: <20181002131242.uWPEmXTFCZwOY2sryRF3sNscRLFNJvCXV9_ag16HVPY@z> Document the changes in Documentation/arm64/tagged-pointers.txt. Signed-off-by: Andrey Konovalov --- Documentation/arm64/tagged-pointers.txt | 24 ++++++++++++++---------- 1 file changed, 14 insertions(+), 10 deletions(-) diff --git a/Documentation/arm64/tagged-pointers.txt b/Documentation/arm64/tagged-pointers.txt index a25a99e82bb1..ae877d185fdb 100644 --- a/Documentation/arm64/tagged-pointers.txt +++ b/Documentation/arm64/tagged-pointers.txt @@ -17,13 +17,21 @@ 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. +Some initial work for supporting non-zero address tags passed to the +kernel has been done. As of now, the kernel supports tags in: -This includes, but is not limited to, addresses found in: + - user fault addresses - - pointer arguments to system calls, including pointers in structures - passed to system calls, + - pointer arguments (including pointers in structures), which don't + describe virtual memory ranges, passed to system calls + +All other interpretations of userspace memory addresses by the kernel +assume an address tag of 0x00. This includes, but is not limited to, +addresses found in: + + - pointer arguments (including pointers in structures), which describe + virtual memory ranges, passed to memory system calls (mmap, mprotect, + etc.) - the stack pointer (sp), e.g. when interpreting it to deliver a signal, @@ -33,11 +41,7 @@ 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 -- 2.19.0.605.g01d371f741-goog