From: Andrey Konovalov <andreyknvl@google.com>
To: Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will.deacon@arm.com>,
Mark Rutland <mark.rutland@arm.com>,
Robin Murphy <robin.murphy@arm.com>,
Kees Cook <keescook@chromium.org>,
Kate Stewart <kstewart@linuxfoundation.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Andrew Morton <akpm@linux-foundation.org>,
Ingo Molnar <mingo@kernel.org>,
"Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
Shuah Khan <shuah@kernel.org>,
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: Chintan Pandya <cpandya@codeaurora.org>,
Jacob Bramley <Jacob.Bramley@arm.com>,
Ruben Ayrapetyan <Ruben.Ayrapetyan@arm.com>,
Andrey Konovalov <andreyknvl@google.com>,
Lee Smith <Lee.Smith@arm.com>, Kostya Serebryany <kcc@google.com>,
Dmitry Vyukov <dvyukov@google.com>,
Ramana Radhakrishnan <Ramana.Radhakrishnan@arm.com>,
Luc Van Oostenryck <luc.vanoostenryck@gmail.com>,
Evgeniy Stepanov <eugenis@google.com>
Subject: [PATCH v9 7/8] arm64: update Documentation/arm64/tagged-pointers.txt
Date: Mon, 10 Dec 2018 13:51:04 +0100 [thread overview]
Message-ID: <5b08153a9d69a5aa958071dcc5477c881f56dcde.1544445454.git.andreyknvl@google.com> (raw)
In-Reply-To: <cover.1544445454.git.andreyknvl@google.com>
Document the changes in Documentation/arm64/tagged-pointers.txt.
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
---
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
--
2.20.0.rc2.403.gdbc3b29805-goog
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next prev parent reply other threads:[~2018-12-10 12:52 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-12-10 12:50 [PATCH v9 0/8] arm64: untag user pointers passed to the kernel Andrey Konovalov
2018-12-10 12:50 ` [PATCH v9 1/8] arm64: add type casts to untagged_addr macro Andrey Konovalov
2018-12-10 12:50 ` [PATCH v9 2/8] uaccess: add untagged_addr definition for other arches Andrey Konovalov
2018-12-10 12:51 ` [PATCH v9 3/8] arm64: untag user addresses in access_ok and __uaccess_mask_ptr Andrey Konovalov
2018-12-10 12:51 ` [PATCH v9 4/8] mm, arm64: untag user addresses in mm/gup.c Andrey Konovalov
2018-12-10 12:51 ` [PATCH v9 5/8] lib, arm64: untag addrs passed to strncpy_from_user and strnlen_user Andrey Konovalov
2018-12-10 12:51 ` [PATCH v9 6/8] fs, arm64: untag user address in copy_mount_options Andrey Konovalov
2018-12-10 12:51 ` Andrey Konovalov [this message]
2018-12-10 12:51 ` [PATCH v9 8/8] selftests, arm64: add a selftest for passing tagged pointers to kernel Andrey Konovalov
2018-12-10 14:30 ` [RFC][PATCH 0/3] arm64 relaxed ABI Vincenzo Frascino
2018-12-10 14:30 ` [RFC][PATCH 1/3] elf: Make AT_FLAGS arch configurable Vincenzo Frascino
2018-12-10 14:30 ` [RFC][PATCH 2/3] arm64: Define Documentation/arm64/elf_at_flags.txt Vincenzo Frascino
2018-12-12 17:34 ` Dave Martin
2019-01-09 13:05 ` Vincenzo Frascino
2018-12-10 14:30 ` [RFC][PATCH 3/3] arm64: elf: Advertise relaxed ABI Vincenzo Frascino
2018-12-12 14:23 ` [RFC][PATCH 0/3] arm64 " Andrey Konovalov
2018-12-12 15:02 ` Catalin Marinas
2018-12-18 15:03 ` Andrey Konovalov
2018-12-18 17:59 ` Catalin Marinas
2018-12-19 12:52 ` Dave Martin
2019-02-11 17:28 ` Kevin Brodsky
2019-02-11 20:32 ` Evgenii Stepanov
2019-02-12 18:02 ` Catalin Marinas
2019-02-13 14:58 ` Dave Martin
2019-02-13 16:42 ` Kevin Brodsky
2019-02-13 17:43 ` Dave Martin
2019-02-13 21:41 ` Evgenii Stepanov
2019-02-14 11:22 ` Kevin Brodsky
2019-02-19 18:38 ` Szabolcs Nagy
2019-02-25 16:57 ` Catalin Marinas
2019-02-25 18:02 ` Szabolcs Nagy
2019-02-26 17:30 ` Kevin Brodsky
2018-12-12 17:01 ` [PATCH v9 0/8] arm64: untag user pointers passed to the kernel Dave Martin
2018-12-18 17:17 ` Andrey Konovalov
2019-02-11 11:35 ` Catalin Marinas
2019-02-11 17:02 ` Dave Martin
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