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 -- 1.9.1
