From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wr1-f71.google.com (mail-wr1-f71.google.com [209.85.221.71]) by kanga.kvack.org (Postfix) with ESMTP id B761E6B060C for ; Thu, 8 Nov 2018 09:36:32 -0500 (EST) Received: by mail-wr1-f71.google.com with SMTP id g17-v6so17305722wrw.6 for ; Thu, 08 Nov 2018 06:36:32 -0800 (PST) Received: from mail-sor-f65.google.com (mail-sor-f65.google.com. [209.85.220.65]) by mx.google.com with SMTPS id p7-v6sor3155535wro.17.2018.11.08.06.36.31 for (Google Transport Security); Thu, 08 Nov 2018 06:36:31 -0800 (PST) From: Andrey Konovalov Subject: [PATCH v8 7/8] arm64: update Documentation/arm64/tagged-pointers.txt Date: Thu, 8 Nov 2018 15:36:14 +0100 Message-Id: <8526edb07fd5a762847306bba89fbadbb19210b7.1541687720.git.andreyknvl@google.com> In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: owner-linux-mm@kvack.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 Document the changes in Documentation/arm64/tagged-pointers.txt. Signed-off-by: Andrey Konovalov --- Documentation/arm64/tagged-pointers.txt | 25 +++++++++++++++---------- 1 file changed, 15 insertions(+), 10 deletions(-) diff --git a/Documentation/arm64/tagged-pointers.txt b/Documentation/arm64/tagged-pointers.txt index a25a99e82bb1..f4cf1f5cf362 100644 --- a/Documentation/arm64/tagged-pointers.txt +++ b/Documentation/arm64/tagged-pointers.txt @@ -17,13 +17,22 @@ 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) for a limited set of syscalls, the exceptions are: -This includes, but is not limited to, addresses found in: + - memory syscalls: brk, madvise, mbind, mincore, mlock, mlock2, move_pages, + mprotect, mremap, msync, munlock, munmap, pkey_mprotect, process_vm_readv, + process_vm_writev, remap_file_pages; - - pointer arguments to system calls, including pointers in structures - passed to system calls, + - ioctls that accept user pointers that describe virtual memory ranges; + + - TCP_ZEROCOPY_RECEIVE setsockopt. + +The kernel supports tags in user fault addresses. However the fault_address +field in the sigcontext struct will contain an untagged address. + +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 +42,7 @@ 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 -- 2.19.1.930.g4563a0d9d0-goog