Date: Mon, 27 Nov 2017 16:37:54 +0000 From: Mark Rutland <mark.rutland@....com> To: linux-arm-kernel@...ts.infradead.org Cc: arnd@...db.de, catalin.marinas@....com, cdall@...aro.org, kvmarm@...ts.cs.columbia.edu, linux-arch@...r.kernel.org, marc.zyngier@....com, mark.rutland@....com, suzuki.poulose@....com, will.deacon@....com, yao.qi@....com, kernel-hardening@...ts.openwall.com, linux-kernel@...r.kernel.org, awallis@...eaurora.org Subject: [PATCHv2 00/12] ARMv8.3 pointer authentication userspace support This series adds support for the ARMv8.3 pointer authentication extension, enabling userspace return address protection with recent versions of GCC. Since RFC : * Make the KVM context switch (semi-lazy) * Rebase to v4.13-rc1 * Improve pointer authentication documentation * Add hwcap documentation * Various minor cleanups Since v1 : * Rebase to v4.15-rc1 * Settle on per-process keys * Strip PACs when unwinding userspace * Don't expose an XPAC hwcap (this is implied by ID registers) * Leave APIB, ABPDA, APDB, and APGA keys unsupported for now * Support IMP DEF algorithms * Rely on KVM ID register emulation * Various cleanups While there are use-cases for keys other than APIAKey, the only software that I'm aware of with pointer authentication support is GCC, which only makes use of APIAKey. I'm happy to add support for other keys as users appear. I've pushed the series to the arm64/pointer-auth branch  of my linux tree. I've also pushed out a necessary bootwrapper patch to the pointer-auth branch  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-A 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. 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, which relies on the recently introduced ID register emulation to hide mismatched support from guests. Thanks, Mark.  http://lists.infradead.org/pipermail/linux-arm-kernel/2017-April/498941.html  https://email@example.com  git://git.kernel.org/pub/scm/linux/kernel/git/mark/linux.git arm64/pointer-auth  git://git.kernel.org/pub/scm/linux/kernel/git/mark/boot-wrapper-aarch64.git pointer-auth Mark Rutland (12): 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 user PAC bit positions via ptrace arm64: perf: strip PAC when unwinding userspace arm64/kvm: preserve host HCR_EL2 value arm64/kvm: context-switch ptrauth registers arm64: enable pointer authentication arm64: docs: document pointer authentication Documentation/arm64/booting.txt | 8 ++ Documentation/arm64/elf_hwcaps.txt | 6 ++ Documentation/arm64/pointer-authentication.txt | 85 ++++++++++++++++++++ arch/arm64/Kconfig | 23 ++++++ arch/arm64/include/asm/cpucaps.h | 8 +- arch/arm64/include/asm/esr.h | 3 +- arch/arm64/include/asm/kvm_arm.h | 3 +- arch/arm64/include/asm/kvm_host.h | 28 ++++++- arch/arm64/include/asm/kvm_hyp.h | 7 ++ arch/arm64/include/asm/mmu.h | 5 ++ arch/arm64/include/asm/mmu_context.h | 25 +++++- arch/arm64/include/asm/pointer_auth.h | 104 +++++++++++++++++++++++++ arch/arm64/include/asm/sysreg.h | 30 +++++++ arch/arm64/include/uapi/asm/hwcap.h | 1 + arch/arm64/include/uapi/asm/ptrace.h | 7 ++ arch/arm64/kernel/cpufeature.c | 103 ++++++++++++++++++++++++ arch/arm64/kernel/cpuinfo.c | 1 + arch/arm64/kernel/head.S | 19 ++++- arch/arm64/kernel/perf_callchain.c | 5 +- arch/arm64/kernel/ptrace.c | 38 +++++++++ arch/arm64/kvm/handle_exit.c | 21 +++++ arch/arm64/kvm/hyp/Makefile | 1 + arch/arm64/kvm/hyp/ptrauth-sr.c | 91 ++++++++++++++++++++++ arch/arm64/kvm/hyp/switch.c | 9 ++- arch/arm64/kvm/hyp/tlb.c | 6 +- arch/arm64/kvm/sys_regs.c | 32 ++++++++ include/asm-generic/mm_hooks.h | 11 +++ include/uapi/linux/elf.h | 1 + 28 files changed, 668 insertions(+), 13 deletions(-) create mode 100644 Documentation/arm64/pointer-authentication.txt create mode 100644 arch/arm64/include/asm/pointer_auth.h create mode 100644 arch/arm64/kvm/hyp/ptrauth-sr.c -- 2.11.0
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