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Date:   Wed, 30 Jan 2019 21:10:07 +0000
From:   Joseph Myers <joseph@codesourcery.com>
To:     Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
CC:     carlos <carlos@redhat.com>, Florian Weimer <fweimer@redhat.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 E. McKenney" <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: [RFC PATCH glibc 1/4] glibc: Perform rseq(2) registration at C
 startup and thread creation (v6)
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On Wed, 30 Jan 2019, Mathieu Desnoyers wrote:

> #if defined (__NR_rseq) && !defined (RSEQ_SIG)
> # error "UAPI headers support rseq system call, but glibc does not define RSEQ_SIG."
> #endif
> 
> Would that take care of your concerns ?

That would of course need appropriate conditionals based on the most 
recent kernel version for which a given glibc version has been updated, so 
that using new kernel headers with an existing glibc release does not make 
the build fail (cf. the test of syscall-names.list).  And being able to 
write such a test only solves one half of the problem - it needs to be 
easy to determine what value to put in that header in glibc for an 
architecture that's newly gained support in the kernel, *without* needing 
any architecture expertise.

-- 
Joseph S. Myers
joseph@codesourcery.com