linux-kernel - Re: [PATCH 1/3] glibc: Perform rseq registration at C startup and thread creation (v21)

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Message-ID: <87r1u48eix.fsf@oldenburg2.str.redhat.com>
Date:   Wed, 24 Jun 2020 21:11:50 +0200
From:   Florian Weimer <fweimer@...hat.com>
To:     Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Cc:     carlos <carlos@...hat.com>, Joseph Myers <joseph@...esourcery.com>,
        Szabolcs Nagy <szabolcs.nagy@....com>,
        libc-alpha <libc-alpha@...rceware.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ben Maurer <bmaurer@...com>,
        Peter Zijlstra <peterz@...radead.org>,
        Paul <paulmck@...ux.vnet.ibm.com>,
        Boqun Feng <boqun.feng@...il.com>,
        Will Deacon <will.deacon@....com>,
        Dave Watson <davejwatson@...com>, Paul Turner <pjt@...gle.com>,
        Rich Felker <dalias@...c.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        linux-api <linux-api@...r.kernel.org>
Subject: Re: [PATCH 1/3] glibc: Perform rseq registration at C startup and thread creation (v21)

* Mathieu Desnoyers:

>> I'm still worried that __rseq_static_assert and __rseq_alignof will show
>> up in the UAPI with textually different definitions.  (This does not
>> apply to __rseq_tls_model_ie.)
>
> What makes this worry not apply to __rseq_tls_model_ie ?

It's not needed by the kernel header because it doesn't contain a
__rseq_abi declaration.

>> 
>> Is my worry unfounded?
>
> So AFAIU you worry that eventually sys/rseq.h and linux/rseq.h carry different
> definitions of __rseq_static_assert and __rseq_alignof.
>
> Indeed, I did not surround those #define with #ifndef/#endif. Maybe we should ?
>
> Just in case the definitions end up being different (worse case scenario), we
> should expect their behavior to be pretty much equivalent. So going for the
> following should address your concern I think:

I think we should keep things simple on the glibc side for now and do
this changes to the kernel headers first.

Thanks,
Florian