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

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Date:   Mon, 7 Sep 2020 11:29:00 +0100
From:   Dave Martin <Dave.Martin@....com>
To:     Boyan Karatotev <boyan.karatotev@....com>
Cc:     Shuah Khan <shuah@...nel.org>, boian4o1@...il.com,
        Catalin Marinas <catalin.marinas@....com>,
        linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org,
        amit.kachhap@....com, vincenzo.frascino@....com,
        Will Deacon <will@...nel.org>,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 0/4] kselftests/arm64: add PAuth tests

On Thu, Sep 03, 2020 at 10:46:33AM +0100, Boyan Karatotev wrote:
> On 02/09/2020 17:48, Dave Martin wrote:
> > 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.
> > 
> I ran it through checkpatch and it came out clean except for some
> MAINTAINERS warnings. I see that when I add --strict it does complain
> about multiple blank lines which I can fix for the next version. Are
> there any other flags I should be running checkpatch with?

Hmmm, probably not.  I had thought checkpatch was generally noisier
about that kind of thing.

Since the issues were all minor and nobody else objected, I would
suggest not to worry about them.

Cheers
---Dave