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Re: [RFC PATCH glibc 09/13] glibc: Perform rseq(2) registration at C startup and thread creation (v13)
- From: Mathieu Desnoyers <mathieu dot desnoyers at efficios dot com>
- To: Florian Weimer <fweimer at redhat dot com>
- Cc: carlos <carlos at redhat dot com>, Joseph Myers <joseph at codesourcery dot com>, Szabolcs Nagy <szabolcs dot nagy at arm dot com>, libc-alpha <libc-alpha at sourceware dot org>, Thomas Gleixner <tglx at linutronix dot de>, Ben Maurer <bmaurer at fb dot com>, Peter Zijlstra <peterz at infradead dot org>, "Paul E. McKenney" <paulmck at linux dot vnet dot ibm dot com>, Boqun Feng <boqun dot feng at gmail dot com>, Will Deacon <will dot deacon at arm dot com>, Dave Watson <davejwatson at fb dot com>, Paul Turner <pjt at google dot com>, Rich Felker <dalias at libc dot org>, linux-kernel <linux-kernel at vger dot kernel dot org>, linux-api <linux-api at vger dot kernel dot org>
- Date: Tue, 7 Jan 2020 15:44:00 -0500 (EST)
- Subject: Re: [RFC PATCH glibc 09/13] glibc: Perform rseq(2) registration at C startup and thread creation (v13)
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- References: <20200106155713.397-1-mathieu.desnoyers@efficios.com> <20200106155713.397-10-mathieu.desnoyers@efficios.com> <871rsbv4io.fsf@oldenburg2.str.redhat.com>
----- On Jan 7, 2020, at 7:23 AM, Florian Weimer fweimer@redhat.com wrote:
> * Mathieu Desnoyers:
>
>> Register rseq(2) TLS for each thread (including main), and unregister
>> for each thread (excluding main). "rseq" stands for Restartable
>> Sequences.
>>
>> See the rseq(2) man page proposed here:
>> https://lkml.org/lkml/2018/9/19/647
>>
>> This patch is based on glibc-2.30. The rseq(2) system call was merged
>> into Linux 4.18.
>
> This patch needs to be updated for some be/le abilist splits.
> Big-endian ABI lists for arm, microblaze, sh, appear to be missing.
done.
> This is something that can be checked with build-many-glibcs.py.
OK.
>
>> diff --git a/manual/threads.texi b/manual/threads.texi
>> index 0858ef8f92..059f781120 100644
>> --- a/manual/threads.texi
>> +++ b/manual/threads.texi
>> @@ -881,3 +881,20 @@ Behaves like @code{pthread_timedjoin_np} except that the
>> absolute time in
>> @c pthread_spin_unlock
>> @c pthread_testcancel
>> @c pthread_yield
>> +
>> +@node Restartable Sequences
>> +@section Restartable Sequences
>> +@cindex rseq
>> +
>> +This section describes the @glibcadj{} Restartable Sequences integration.
>> +
>> +The @glibcadj{} implements a __rseq_abi TLS symbol to interact with the
> @Theglibc{} @code{__rseq_abi}
>
>
>> +Restartable Sequences system call (Linux-specific). The layout of this
>> +structure is defined by the Linux kernel rseq.h UAPI. Registration of each
>> +thread's __rseq_abi is performed by @glibcadj{} at libc initialization and
> @theglibc{}
> @code{__rseq_abi}
>> +pthread creation.
>
>> +Each supported architecture provide a RSEQ_SIG signature in sys/rseq.h. That
> @code{RSEQ_SIG} @file{sys/rseq.h}
>
>> +signature is expected to be present in the code before each Restartable
>> +Sequences abort handler. Failure to provide the expected signature may
>> +terminate the process with a Segmentation fault.
>
>
> Two spaces at the end of setences, please.
All above done.
>
> The manual should use @deftypevar to create an index entry etc. for
> __rseq_abi. See argp_program_version for an example of how to do this.
OK. I've added __rseq_abi as a variable and RSEQ_SIG as a macro.
>
> I think current policy is to have documentation for at least the minimum
> functionality in the manual. I understand that it makes it a lot of
> work to write patches which add system call wrappers.
Makes sense.
Thanks!
Mathieu
>
> Thanks,
> Florian
--
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com