Re: [RFC PATCH glibc 09/13] glibc: Perform rseq(2) registration at C startup and thread creation (v13)
From: Florian Weimer <hidden>
Date: 2020-01-07 12:24:13
Also in:
lkml
* 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.
quoted hunk
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