linux-kernel - Re: [PATCH 3/4] kselftests/arm64: add PAuth test for whether exec() changes keys

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Message-ID: <20200916153809.GZ6642@arm.com>
Date:   Wed, 16 Sep 2020 16:38:12 +0100
From:   Dave Martin <Dave.Martin@....com>
To:     Boyan Karatotev <boian4o1@...il.com>
Cc:     Boyan Karatotev <boyan.karatotev@....com>,
        Will Deacon <will@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org,
        amit.kachhap@....com, vincenzo.frascino@....com,
        Shuah Khan <shuah@...nel.org>,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 3/4] kselftests/arm64: add PAuth test for whether exec()
 changes keys

On Tue, Sep 15, 2020 at 04:18:28PM +0100, Boyan Karatotev wrote:
> On 07/09/2020 11:27 am, Dave Martin wrote:
> > On Thu, Sep 03, 2020 at 11:20:25AM +0100, Boyan Karatotev wrote:
> >> On 02/09/2020 18:00, Dave Martin wrote:
> >>> On Fri, Aug 28, 2020 at 02:16:05PM +0100, Boyan Karatotev wrote:
> >>>> +int exec_sign_all(struct signatures *signed_vals, size_t val)
> >>>> +{
> >>>
> >>> Could popen(3) be used here?
> >>>
> >>> Fork-and-exec is notoriously fiddly, so it's preferable to use a library
> >>> function to do it where applicable.I would love to, but the worker needs a bidirectional channel and popen
> >> only gives a unidirectional stream.
> > 
> > Ah, fair point.
> > 
> > Would it help if you created an additional pipe before calling popen()?
> > 
> > May not be worth it, though.  For one thing, wiring that extra pipe to
> > stdin or stdout in the child process would require some extra work...
> Well, I probably could, but I doubt the result would be any better. I
> agree that I'm not sure the effort is worth it and would rather keep it
> the same.

Sure, fair enough.

Ideally kselftest would provide some common code for this sort of thing,
but I guess that's a separate discussion.

Cheers
---Dave