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[209.85.220.65]) by mx.google.com with SMTPS id l7sor1101025wrr.32.2019.02.22.04.53.51 for (Google Transport Security); Fri, 22 Feb 2019 04:53:51 -0800 (PST) Received-SPF: pass (google.com: domain of andreyknvl@google.com designates 209.85.220.65 as permitted sender) client-ip=209.85.220.65; Authentication-Results: mx.google.com; dkim=pass header.i=@google.com header.s=20161025 header.b=SP+p1d8f; spf=pass (google.com: domain of andreyknvl@google.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=andreyknvl@google.com; dmarc=pass (p=REJECT sp=REJECT dis=NONE) header.from=google.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=QBwzVVFrwl/lt9+IMfY2XIzbrADnd5gfL2MVdMoEoBA=; b=SP+p1d8f0BVnFGmwpzP5ObmgqSe7l5anq9SYK3Z0/3NQEWTdLTfJgPvtmksh4rCpqp IfRqUp24iOQF92rOfMBXwE8SN4Qg9+J3Ff0nPtSyfwTEqbyNm+DeeN5PWzbyT11CnE2+ NiNjrCubovAK/wbw8TnBd9rAdhYi2JGQm/9ZBjiURbGSLjfWJPtszQ5Wp43UoL05Tluv TlBFrRQljeAOUxOv3LCaFgOpw7HH2il9JHvSEnJIjNEhD/hw3TxMJV0heNgWZ4hyYnqc k67G6tBgxNf5nw4KsRQIR60AgXHPgBerP6BueL5DUb/aboLZYnGfKfMCtobiEEHXKnw+ xU8Q== X-Google-Smtp-Source: AHgI3IZQ0MX6sfukCDFdoJfLKBs/7VPcUCMns2qTz5bt2s0RG4yqp/Tz4fV7jNtbv7px50I5nWPT9w== X-Received: by 2002:adf:efc8:: with SMTP id i8mr3073265wrp.164.1550840031452; Fri, 22 Feb 2019 04:53:51 -0800 (PST) Received: from andreyknvl0.muc.corp.google.com ([2a00:79e0:15:13:8ce:d7fa:9f4c:492]) by smtp.gmail.com with ESMTPSA id o14sm808209wrp.34.2019.02.22.04.53.49 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 22 Feb 2019 04:53:50 -0800 (PST) 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 , 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 , Dave Martin , Kevin Brodsky , Szabolcs Nagy , Andrey Konovalov Subject: [PATCH v10 11/12] arm64: update Documentation/arm64/tagged-pointers.txt Date: Fri, 22 Feb 2019 13:53:23 +0100 Message-Id: X-Mailer: git-send-email 2.21.0.rc0.258.g878e2cd30e-goog In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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 -- 2.21.0.rc0.258.g878e2cd30e-goog