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From:   Florian Weimer <fweimer@redhat.com>
To:     Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc:     carlos <carlos@redhat.com>, Joseph Myers <joseph@codesourcery.com>,
        Szabolcs Nagy <szabolcs.nagy@arm.com>,
        libc-alpha <libc-alpha@sourceware.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ben Maurer <bmaurer@fb.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Paul <paulmck@linux.vnet.ibm.com>,
        Boqun Feng <boqun.feng@gmail.com>,
        Will Deacon <will.deacon@arm.com>,
        Dave Watson <davejwatson@fb.com>, Paul Turner <pjt@google.com>,
        Rich Felker <dalias@libc.org>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        linux-api <linux-api@vger.kernel.org>
Subject: Re: [PATCH 1/3] glibc: Perform rseq registration at C startup and thread creation (v21)
References: <20200622180803.1449-1-mathieu.desnoyers@efficios.com>
        <20200622180803.1449-2-mathieu.desnoyers@efficios.com>
        <87d05obl4w.fsf@oldenburg2.str.redhat.com>
        <1158112159.11628.1593025203438.JavaMail.zimbra@efficios.com>
Date:   Wed, 24 Jun 2020 21:11:50 +0200
In-Reply-To: <1158112159.11628.1593025203438.JavaMail.zimbra@efficios.com>
        (Mathieu Desnoyers's message of "Wed, 24 Jun 2020 15:00:03 -0400
        (EDT)")
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* 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