linux-kernel - Re: [PATCH 0/4] kselftests/arm64: add PAuth tests

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Date:   Wed, 2 Sep 2020 17:48:26 +0100
From:   Dave Martin <Dave.Martin@....com>
To:     Boyan Karatotev <boyan.karatotev@....com>
Cc:     linux-arm-kernel@...ts.infradead.org,
        linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org,
        Will Deacon <will@...nel.org>, boian4o1@...il.com,
        Catalin Marinas <catalin.marinas@....com>,
        amit.kachhap@....com, vincenzo.frascino@....com,
        Shuah Khan <shuah@...nel.org>
Subject: Re: [PATCH 0/4] kselftests/arm64: add PAuth tests

On Fri, Aug 28, 2020 at 02:16:02PM +0100, Boyan Karatotev wrote:
> Pointer Authentication (PAuth) is a security feature introduced in ARMv8.3.
> It introduces instructions to sign addresses and later check for potential
> corruption using a second modifier value and one of a set of keys. The
> signature, in the form of the Pointer Authentication Code (PAC), is stored
> in some of the top unused bits of the virtual address (e.g. [54: 49] if
> TBID0 is enabled and TnSZ is set to use a 48 bit VA space). A set of
> controls are present to enable/disable groups of instructions (which use
> certain keys) for compatibility with libraries that do not utilize the
> feature. PAuth is used to verify the integrity of return addresses on the
> stack with less memory than the stack canary.
> 
> This patchset adds kselftests to verify the kernel's configuration of the
> feature and its runtime behaviour. There are 7 tests which verify that:
> 	* an authentication failure leads to a SIGSEGV
> 	* the data/instruction instruction groups are enabled
> 	* the generic instructions are enabled
> 	* all 5 keys are unique for a single thread
> 	* exec() changes all keys to new unique ones
> 	* context switching preserves the 4 data/instruction keys
> 	* context switching preserves the generic keys
> 
> The tests have been verified to work on qemu without a working PAUTH
> Implementation and on ARM's FVP with a full or partial PAuth
> implementation.
> 
> Note: This patchset is only verified for ARMv8.3 and there will be some
> changes required for ARMv8.6. More details can be found here [1]. Once
> ARMv8.6 PAuth is merged the first test in this series will required to be
> updated.

Nit: is it worth running checkpatch over this series?

Although this is not kernel code, there are a number of formatting
weirdnesses and surplus blank lines etc. that checkpatch would probably
warn about.

[...]

Cheers
---Dave