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From: Will Deacon <will.deacon@arm.com>
To: Kristina Martsenko <kristina.martsenko@arm.com>
Cc: linux-arm-kernel@lists.infradead.org,
	Adam Wallis <awallis@codeaurora.org>,
	Amit Kachhap <Amit.Kachhap@arm.com>,
	Andrew Jones <drjones@redhat.com>,
	Ard Biesheuvel <ard.biesheuvel@linaro.org>,
	Arnd Bergmann <arnd@arndb.de>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Christoffer Dall <christoffer.dall@arm.com>,
	Dave P Martin <Dave.Martin@arm.com>,
	Jacob Bramley <jacob.bramley@arm.com>,
	Kees Cook <keescook@chromium.org>,
	Marc Zyngier <marc.zyngier@arm.com>,
	Mark Rutland <mark.rutland@arm.com>,
	Ramana Radhakrishnan <ramana.radhakrishnan@arm.com>,
	"Suzuki K . Poulose" <suzuki.poulose@arm.com>,
	kvmarm@lists.cs.columbia.edu, linux-arch@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH 00/17] ARMv8.3 pointer authentication support
Date: Fri, 19 Oct 2018 13:36:47 +0100
Message-ID: <20181019123646.GG14246@arm.com> (raw)
In-Reply-To: <20181005084754.20950-1-kristina.martsenko@arm.com>

On Fri, Oct 05, 2018 at 09:47:37AM +0100, Kristina Martsenko wrote:
> 1) Key support
> 
> This series enables the use of instructions using APIAKey, which is
> initialised and maintained per-process (shared by all threads). GCC
> currently only makes use of APIAKey.
> 
> This series does not add support for APIBKey, APDAKey, APDBKey, nor
> APGAKey. HINT-space instructions using these keys will currently execute
> as NOPs. Support for these keys can be added as users appear.
> 
> Note that while we expose the cpuid register (ID_AA64ISAR1_EL1) to
> userspace, it only contains one feature for address authentication
> (API/APA), so it cannot be used by userspace to tell which keys the
> kernel supports. For this the kernel exposes HWCAP bits, one per key
> (currently only APIAKey), which must be checked instead.

Given that the architecture doesn't provide an identification mechanism
for the case where only one of the keys is available, I would much prefer
that we expose both of the keys to userspace. Is the only downside of
that a possible exception entry overhead if the kernel wants to use pointer
authentication as well?

Having an initial implementation where the B key operations act as NOPs
isn't ideal if we want to support future users -- chances are they'll
be put off because deployed kernels don't give them whatever security
guarantees they require. It's a bit of a chicken-and-egg problem, so
unless we have good reasons to keep the B key hidden, I think we should
be exposing it from the start.

Will

  parent reply index

Thread overview: 62+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-10-05  8:47 Kristina Martsenko
2018-10-05  8:47 ` [PATCH v5 01/17] arm64: add pointer authentication register bits Kristina Martsenko
2018-10-11 16:28   ` Will Deacon
2018-10-12  8:53     ` Mark Rutland
2018-10-12  8:56       ` Will Deacon
2018-10-12  9:50         ` Mark Rutland
2018-10-05  8:47 ` [PATCH v5 02/17] arm64/kvm: consistently handle host HCR_EL2 flags Kristina Martsenko
2018-10-05  8:47 ` [PATCH v5 03/17] arm64/kvm: hide ptrauth from guests Kristina Martsenko
2018-10-05  8:47 ` [PATCH v5 04/17] arm64: Don't trap host pointer auth use to EL2 Kristina Martsenko
2018-10-05  8:47 ` [PATCH v5 05/17] arm64/cpufeature: detect pointer authentication Kristina Martsenko
2018-10-05  8:47 ` [PATCH v5 06/17] asm-generic: mm_hooks: allow hooks to be overridden individually Kristina Martsenko
2018-10-05  8:47 ` [PATCH v5 07/17] arm64: add basic pointer authentication support Kristina Martsenko
2018-10-11 16:00   ` Suzuki K Poulose
2018-10-19 11:15   ` Catalin Marinas
2018-10-19 11:24     ` Will Deacon
2018-10-19 15:36       ` Kees Cook
2018-10-19 15:49         ` Will Deacon
2018-10-19 16:05           ` Kees Cook
2018-10-19 16:16             ` Will Deacon
2018-10-19 15:54         ` Mark Rutland
2018-10-19 16:49       ` Cyrill Gorcunov
2018-11-14 18:11       ` Will Deacon
2018-11-15 10:25         ` Dave Martin
2018-10-23  8:36     ` Ramana Radhakrishnan
2018-10-23 10:20       ` Will Deacon
2018-10-05  8:47 ` [PATCH v5 08/17] arm64: expose user PAC bit positions via ptrace Kristina Martsenko
2018-10-05  8:47 ` [PATCH v5 09/17] arm64: perf: strip PAC when unwinding userspace Kristina Martsenko
2018-10-05  8:47 ` [PATCH v5 10/17] arm64: enable pointer authentication Kristina Martsenko
2018-10-05  8:47 ` [PATCH v5 11/17] arm64: docs: document " Kristina Martsenko
2018-10-05  9:04   ` Ramana Radhakrishnan
2018-10-16 16:14     ` Kristina Martsenko
2018-10-19 11:35       ` Catalin Marinas
2018-10-19 11:47         ` Marc Zyngier
2018-10-19 12:22         ` Will Deacon
2018-10-19 14:42         ` Kristina Martsenko
2018-10-19 15:10           ` Catalin Marinas
2018-10-19 17:45             ` Will Deacon
2018-11-02  6:02               ` Jon Masters
2018-10-24 10:56         ` Ramana Radhakrishnan
2018-10-15 22:35   ` Kees Cook
2018-11-02  9:46     ` Ramana Radhakrishnan
2018-10-05  8:47 ` [RFC 12/17] arm64: move ptrauth keys to thread_info Kristina Martsenko
2018-10-19 11:38   ` Catalin Marinas
2018-10-05  8:47 ` [RFC 13/17] arm64: install user ptrauth keys at kernel exit time Kristina Martsenko
2018-10-05  8:47 ` [RFC 14/17] arm64: unwind: strip PAC from kernel addresses Kristina Martsenko
2018-10-05  8:47 ` [RFC 15/17] arm64: enable ptrauth earlier Kristina Martsenko
2018-10-06 12:51   ` Amit Kachhap
2018-10-05  8:47 ` [RFC 16/17] arm64: initialize and switch ptrauth kernel keys Kristina Martsenko
2018-10-06 12:56   ` Amit Kachhap
2018-10-05  8:47 ` [RFC 17/17] arm64: compile the kernel with ptrauth -msign-return-address Kristina Martsenko
2018-10-05  9:01   ` Ramana Radhakrishnan
2018-10-11 14:00     ` Kristina Martsenko
2018-10-11 14:23   ` Vladimir Murzin
2018-10-15 22:38     ` Kees Cook
2018-10-15 22:42 ` [PATCH 00/17] ARMv8.3 pointer authentication support Kees Cook
2018-11-13 16:17   ` Kristina Martsenko
2018-11-13 23:09     ` Kees Cook
2018-11-14 15:54       ` Kristina Martsenko
2018-11-14 21:47       ` Mark Rutland
2018-11-14 22:48         ` Kees Cook
2018-10-19 12:36 ` Will Deacon [this message]
2018-10-23  8:39   ` Ramana Radhakrishnan

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