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

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Date:   Tue, 15 Sep 2020 16:18:28 +0100
From:   Boyan Karatotev <boian4o1@...il.com>
To:     Dave Martin <Dave.Martin@....com>,
        Boyan Karatotev <boyan.karatotev@....com>
Cc:     Shuah Khan <shuah@...nel.org>,
        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 3/4] kselftests/arm64: add PAuth test for whether exec()
 changes keys

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.