| Message ID | 1491232765-32501-1-git-send-email-mark.rutland@arm.com |
|---|---|
| Headers | show |
| Series | ARMv8.3 pointer authentication userspace support | expand |
On 4/3/2017 11:19 AM, Mark Rutland wrote: > This series adds support for the ARMv8.3 pointer authentication extension. > > I've included a quick intro to the extension below, with the usual series > description below that. The final patch of the series adds additional > documentation regarding the extension. > > I've based the series on the arm64 for-next/core branch [1]. I'm aware that > this series may conflict with other patches currently in flight (e.g. > allocation of ELF notes), and I intend to rebase this series as things settle. > > I've pushed the series to the arm64/pointer-auth branch [2] of my linux tree. > I've also pushed out a necessary bootwrapper patch to the pointer-auth branch > [3] of my bootwrapper repo. > > > Extension Overview > ================== > > The ARMv8.3 pointer authentication extension adds functionality to detect > modification of pointer values, mitigating certain classes of attack such as > stack smashing, and making return oriented programming attacks harder > > The extension introduces the concept of a pointer authentication code (PAC), > which is stored in some upper bits of pointers. Each PAC is derived from the > original pointer, another 64-bit value (e.g. the stack pointer), and a secret > 128-bit key. > > New instructions are added which can be used to: > > * Insert a PAC into a pointer > * Strip a PAC from a pointer > * Authenticate strip a PAC from a pointer > > If authentication succeeds, the code is removed, yielding the original pointer. > If authentication fails, bits are set in the pointer such that it is guaranteed > to cause a fault if used. > > These instructions can make use of four keys: > > * APIAKey (A.K.A. Instruction A key) > * APIBKey (A.K.A. Instruction B key) > * APDAKey (A.K.A. Data A key) > * APDBKey (A.K.A. Data B Key) > > A subset of these instruction encodings have been allocated from the HINT > space, and will operate as NOPs on any ARMv8 parts which do not feature the > extension (or if purposefully disabled by the kernel). Software using only this > subset of the instructions should function correctly on all ARMv8-A parts. > > Additionally, instructions are added to authenticate small blocks of memory in > similar fashion, using APGAKey (A.K.A. Generic key). > > > This Series > =========== > > This series enables the use of instructions using APIAKey, which is initialised > and maintained per-process (shared by all threads). This series does not add > support for APIBKey, APDAKey, APDBKey, nor APGAKey. The series only supports > the use of an architected algorithm. > > I've given this some basic testing with a homebrew test suite. More ideally, > we'd add some tests to the kernel source tree. > > I've added some basic KVM support, but this doesn't cater for systems with > mismatched support. Looking forward, we'll need ID register emulation in KVM so > that we can hide features from guests to cater for cases like this. > > There are also a few questions to consider, e.g: > > * Should we expose a per-process data key now, to go with the insn key? > * Should keys be per-thread rather than per-process? > * Should we expose generic authentication (i.e. APGAKey)? > * Should the kernel remove PACs when unwinding user stacks? > > Thanks, > Mark. > > [1] git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-next/core > [2] git://git.kernel.org/pub/scm/linux/kernel/git/mark/linux.git arm64/pointer-auth > [3] git://git.kernel.org/pub/scm/linux/kernel/git/mark/boot-wrapper-aarch64.git pointer-auth > > Mark Rutland (9): > asm-generic: mm_hooks: allow hooks to be overridden individually > arm64: add pointer authentication register bits > arm64/cpufeature: add ARMv8.3 id_aa64isar1 bits > arm64/cpufeature: detect pointer authentication > arm64: Don't trap host pointer auth use to EL2 > arm64: add basic pointer authentication support > arm64: expose PAC bit positions via ptrace > arm64/kvm: context-switch PAC registers > arm64: docs: document pointer authentication > > Documentation/arm64/booting.txt | 8 +++ > Documentation/arm64/pointer-authentication.txt | 78 +++++++++++++++++++++ > arch/arm64/Kconfig | 23 ++++++ > arch/arm64/include/asm/cpucaps.h | 4 +- > arch/arm64/include/asm/esr.h | 3 +- > arch/arm64/include/asm/kvm_arm.h | 2 + > arch/arm64/include/asm/kvm_emulate.h | 15 ++++ > arch/arm64/include/asm/kvm_host.h | 12 ++++ > arch/arm64/include/asm/mmu.h | 5 ++ > arch/arm64/include/asm/mmu_context.h | 25 ++++++- > arch/arm64/include/asm/pointer_auth.h | 96 ++++++++++++++++++++++++++ > arch/arm64/include/asm/sysreg.h | 30 ++++++++ > arch/arm64/include/uapi/asm/hwcap.h | 1 + > arch/arm64/include/uapi/asm/ptrace.h | 5 ++ > arch/arm64/kernel/cpufeature.c | 39 ++++++++++- > arch/arm64/kernel/cpuinfo.c | 1 + > arch/arm64/kernel/head.S | 19 ++++- > arch/arm64/kernel/ptrace.c | 39 +++++++++++ > arch/arm64/kvm/hyp/sysreg-sr.c | 43 ++++++++++++ > include/asm-generic/mm_hooks.h | 12 ++++ > include/uapi/linux/elf.h | 1 + > 21 files changed, 454 insertions(+), 7 deletions(-) > create mode 100644 Documentation/arm64/pointer-authentication.txt > create mode 100644 arch/arm64/include/asm/pointer_auth.h > Tested on Qualcomm platform with ARMV8 architecture (without 8.3 extensions) for backwards compatibility (meaning I did not pass -march=armv8.3-a to GCC; only -msign-return-address=all). The HINT PACIASP/AUTIASP caused no issues and no other issues were encountered. Will test again once a platform is available with 8.3-a extensions. Thanks -- Adam Wallis Qualcomm Datacenter Technologies as an affiliate of Qualcomm Technologies, Inc. Qualcomm Technologies, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project.