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Re: [RFC PATCH glibc 09/13] glibc: Perform rseq(2) registration at C startup and thread creation (v13)
- From: Florian Weimer <fweimer at redhat dot com>
- To: Mathieu Desnoyers <mathieu dot desnoyers at efficios dot com>
- Cc: Carlos O'Donell <carlos at redhat dot com>, Joseph Myers <joseph at codesourcery dot com>, Szabolcs Nagy <szabolcs dot nagy at arm dot com>, 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 at vger dot kernel dot org, linux-api at vger dot kernel dot org
- Date: Tue, 07 Jan 2020 13:23:59 +0100
- Subject: Re: [RFC PATCH glibc 09/13] glibc: Perform rseq(2) registration at C startup and thread creation (v13)
- References: <20200106155713.397-1-mathieu.desnoyers@efficios.com> <20200106155713.397-10-mathieu.desnoyers@efficios.com>
* 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.
This is something that can be checked with build-many-glibcs.py.
> 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.
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.
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.
Thanks,
Florian