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From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
To: Joseph Myers <joseph@codesourcery.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)
Date: Thu, 31 Jan 2019 11:37:08 -0500 (EST)	[thread overview]
Message-ID: <19276261.499.1548952628477.JavaMail.zimbra@efficios.com> (raw)
In-Reply-To: <alpine.DEB.2.21.1901302104360.16754@digraph.polyomino.org.uk>

----- On Jan 30, 2019, at 4:10 PM, Joseph Myers joseph@codesourcery.com wrote:

> 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).

The test I hint at above would not be for the glibc build per se. It would
be for a check that glibc implements support for all the system calls
available in the kernel headers (if such a test target currently exists).

> 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.

I'm afraid this requirement is incompatible with the nature of the RSEQ
signature. This signature may be required to be a specific trap instruction
by the architecture, so deciding on its value without architecture expertise
is not possible.

Thanks,

Mathieu

-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com

  reply	other threads:[~2019-01-31 16:37 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-01-21 21:35 [RFC PATCH glibc 1/4] glibc: Perform rseq(2) registration at C startup and thread creation (v6) Mathieu Desnoyers
2019-01-21 21:35 ` [RFC PATCH glibc 2/4] glibc: sched_getcpu(): use rseq cpu_id TLS on Linux Mathieu Desnoyers
2019-01-29 16:57 ` [RFC PATCH glibc 1/4] glibc: Perform rseq(2) registration at C startup and thread creation (v6) Mathieu Desnoyers
2019-01-29 21:56   ` Joseph Myers
2019-01-30  1:39     ` Mathieu Desnoyers
2019-01-30  2:40       ` Joseph Myers
2019-01-30 18:03         ` Mathieu Desnoyers
2019-01-30 21:10           ` Joseph Myers
2019-01-31 16:37             ` Mathieu Desnoyers [this message]
2019-01-31 16:53               ` Mathieu Desnoyers

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