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Subject[PATCH glibc 1/3] glibc: Perform rseq registration at C startup and thread creation (v20)
Date
Register rseq 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

Those are based on glibc master branch commit 415d0b0b3f16.
The rseq system call was merged into Linux 4.18.

CC: Carlos O'Donell <carlos@redhat.com>
CC: Florian Weimer <fweimer@redhat.com>
CC: Joseph Myers <joseph@codesourcery.com>
CC: Szabolcs Nagy <szabolcs.nagy@arm.com>
CC: Thomas Gleixner <tglx@linutronix.de>
CC: Ben Maurer <bmaurer@fb.com>
CC: Peter Zijlstra <peterz@infradead.org>
CC: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
CC: Boqun Feng <boqun.feng@gmail.com>
CC: Will Deacon <will.deacon@arm.com>
CC: Dave Watson <davejwatson@fb.com>
CC: Paul Turner <pjt@google.com>
CC: Rich Felker <dalias@libc.org>
CC: libc-alpha@sourceware.org
CC: linux-kernel@vger.kernel.org
CC: linux-api@vger.kernel.org
---
Changes since v1:
- Move __rseq_refcount to an extra field at the end of __rseq_abi to
eliminate one symbol.

All libraries/programs which try to register rseq (glibc,
early-adopter applications, early-adopter libraries) should use the
rseq refcount. It becomes part of the ABI within a user-space
process, but it's not part of the ABI shared with the kernel per se.

- Restructure how this code is organized so glibc keeps building on
non-Linux targets.

- Use non-weak symbol for __rseq_abi.

- Move rseq registration/unregistration implementation into its own
nptl/rseq.c compile unit.

- Move __rseq_abi symbol under GLIBC_2.29.

Changes since v2:
- Move __rseq_refcount to its own symbol, which is less ugly than
trying to play tricks with the rseq uapi.
- Move __rseq_abi from nptl to csu (C start up), so it can be used
across glibc, including memory allocator and sched_getcpu(). The
__rseq_refcount symbol is kept in nptl, because there is no reason
to use it elsewhere in glibc.

Changes since v3:
- Set __rseq_refcount TLS to 1 on register/set to 0 on unregister
because glibc is the first/last user.
- Unconditionally register/unregister rseq at thread start/exit, because
glibc is the first/last user.
- Add missing abilist items.
- Rebase on glibc master commit a502c5294.
- Add NEWS entry.

Changes since v4:
- Do not use "weak" symbols for __rseq_abi and __rseq_refcount. Based on
"System V Application Binary Interface", weak only affects the link
editor, not the dynamic linker.
- Install a new sys/rseq.h system header on Linux, which contains the
RSEQ_SIG definition, __rseq_abi declaration and __rseq_refcount
declaration. Move those definition/declarations from rseq-internal.h
to the installed sys/rseq.h header.
- Considering that rseq is only available on Linux, move csu/rseq.c to
sysdeps/unix/sysv/linux/rseq-sym.c.
- Move __rseq_refcount from nptl/rseq.c to
sysdeps/unix/sysv/linux/rseq-sym.c, so it is only defined on Linux.
- Move both ABI definitions for __rseq_abi and __rseq_refcount to
sysdeps/unix/sysv/linux/Versions, so they only appear on Linux.
- Document __rseq_abi and __rseq_refcount volatile.
- Document the RSEQ_SIG signature define.
- Move registration functions from rseq.c to rseq-internal.h static
inline functions. Introduce empty stubs in misc/rseq-internal.h,
which can be overridden by architecture code in
sysdeps/unix/sysv/linux/rseq-internal.h.
- Rename __rseq_register_current_thread and __rseq_unregister_current_thread
to rseq_register_current_thread and rseq_unregister_current_thread,
now that those are only visible as internal static inline functions.
- Invoke rseq_register_current_thread() from libc-start.c LIBC_START_MAIN
rather than nptl init, so applications not linked against
libpthread.so have rseq registered for their main() thread. Note that
it is invoked separately for SHARED and !SHARED builds.

Changes since v5:
- Replace __rseq_refcount by __rseq_lib_abi, which contains two
uint32_t: register_state and refcount. The "register_state" field
allows inhibiting rseq registration from signal handlers nested on top
of glibc registration and occuring after rseq unregistration by glibc.
- Introduce enum rseq_register_state, which contains the states allowed
for the struct rseq_lib_abi register_state field.

Changes since v6:
- Introduce bits/rseq.h to define RSEQ_SIG for each architecture.
The generic bits/rseq.h does not define RSEQ_SIG, meaning that each
architecture implementing rseq needs to implement bits/rseq.h.
- Rename enum item RSEQ_REGISTER_NESTED to RSEQ_REGISTER_ONGOING.
- Port to glibc-2.29.

Changes since v7:
- Remove __rseq_lib_abi symbol, including refcount and register_state
fields.
- Remove reference counting and nested signals handling from
registration/unregistration functions.
- Introduce new __rseq_handled exported symbol, which is set to 1
by glibc on C startup when it handles restartable sequences.
This allows glibc to coexist with early adopter libraries and
applications wishing to register restartable sequences when it
is not handled by glibc.
- Introduce rseq_init (), which sets __rseq_handled to 1 from
C startup.
- Update NEWS entry.
- Update comments at the beginning of new files.
- Registration depends on both __NR_rseq and RSEQ_SIG.
- Remove ARM, powerpc, MIPS RSEQ_SIG until we agree with maintainers
on the signature choice.
- Update x86, s390 RSEQ_SIG based on discussion with arch maintainers.
- Remove rseq-internal.h from headers list of misc/Makefile, so it
it not installed by make install.

Changes since v8:
- Introduce RSEQ_SIG_CODE and RSEQ_SIG_DATA on aarch64 to handle
compiling with -mbig-endian.

Changes since v9:
- Update Changelog.
- Remove unneeded new file comment header newlines.

Changes since v10:
- Remove volatile from __rseq_abi declaration.
- Document that __rseq_handled is about library managing rseq
registration, independently of whether rseq is available or not.
- Move __rseq_handled symbol to ld.so, initialize this symbol within
the dynamic linker initialization for both shared (rtld.c) and static
(dl-support.c) builds.
- Only register the rseq TLS on initialization once in multiple-libc
scenarios. Use rtld_active () for this purpose.
- In the static libc case, register the rseq TLS after LD_PRELOAD
constructors are run, so it matches the order of this initialization
vs LD_PRELOAD contructors execution for the shared libc.
- Agreed on signature choice with powerpc and MIPS maintainers,
re-adding those signatures,
- The main architecture still left out signature-wise is ARM32.

Changes since v11:
- Rebase on glibc 2.30.
- Re-introduce ARM RSEQ_SIG following feedback from Will Deacon.

Changes since v12:
- Remove __rseq_handled,
- Rely on OS implicit rseq unregistration on thread teardown,
- Register main thread in __libc_early_init ().
- Add Restartable Sequences entry to threads manual.

Changes since v13:
- Update following be/le abilist split for arm, microblaze, and sh.
- Update manual to add the __rseq_abi variable and RSEQ_SIG macro to
generate manual index entries, and add missing "Restartable Sequences"
menu entry to the threads chapter.

Changes since v14:
- Update copyright range to include 2020.
- Introduce __ASSUME_RSEQ defined for --enable-kernel=4.18.0 and higher.
- Use ifdef __ASSUME_RSEQ rather than ifdef __NR_rseq to discover rseq
availability. This is necessary now that the system call numbers are
integrated within glibc.

Changes since v15:
- Remove __ASSUME_RSEQ from kernel features.
- rseq internal: remove assume rseq
- remove assume rseq and struct rseq def from sysdeps/unix/sysv/linux/rseq-sym.c
- sys/rseq.h: detect rseq header, implement fallback
- sysdeps/unix/sysv/linux/sys/rseq.h include cdefs.h, add _Static_assert
to validate struct rseq and struct rseq_cs alignment.
- sys/rseq.h: document that posix_memalign should be used rather than
malloc if allocating struct rseq or struct rseq_cs on the heap. This
is required to guarantee 32-byte alignement.

Changes since v16:
- Move rseq NEWS entry under 2.32.
- Move new __rseq_abi symbol to GLIBC_2.32.

Changes since v17:
- Change copyright year to 2020.
- Refer to GNU C Library manual rather than rseq manpage in NEWS.
- Use "initial" parameter from __libc_early_init ().
- Manual: rseq is Linux rather than GNU std.
- Remove rseq_unregister_current_thread () (unused).
- rseq_register_current_thread () returns void.
- Coding style fixes.
- sys/rseq.h: use "32" for alignment.
- Change http:// for https:// in comments.
- Add const struct rseq_cs * field to rseq_cs union.

Changes since v18:
- NEWS update.
- Manual update.
- Move misc/rseq-internal.h to sysdeps/generic/rseq-internal.h.
- Fix coding style in sysdeps/unix/sysv/linux/sys/rseq.h.
- Abort libc if __rseq_abi is already initialized in
rseq_register_current_thread (), which is unexpected.
- Abort libc in rseq_register_current_thread () on all
errno except EPERM (seccomp), EACCES (seccomp), and ENOSYS
(not implemented).

Changes since v19:
- Take care of feedback from Florian.
- Update manual to remove uptr field, which is removed from sys/rseq.h.
- Rebase on current master branch.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
CC: Carlos O'Donell <carlos@redhat.com>
CC: Florian Weimer <fweimer@redhat.com>
CC: Joseph Myers <joseph@codesourcery.com>
CC: Szabolcs Nagy <szabolcs.nagy@arm.com>
CC: Thomas Gleixner <tglx@linutronix.de>
CC: Ben Maurer <bmaurer@fb.com>
CC: Peter Zijlstra <peterz@infradead.org>
CC: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
CC: Boqun Feng <boqun.feng@gmail.com>
CC: Will Deacon <will.deacon@arm.com>
CC: Paul Turner <pjt@google.com>
CC: Rich Felker <dalias@libc.org>
CC: libc-alpha@sourceware.org
CC: linux-kernel@vger.kernel.org
CC: linux-api@vger.kernel.org
---
NEWS | 10 +
elf/libc_early_init.c | 4 +
manual/threads.texi | 63 +++++
nptl/pthread_create.c | 13 +
sysdeps/generic/rseq-internal.h | 26 ++
sysdeps/unix/sysv/linux/Makefile | 5 +-
sysdeps/unix/sysv/linux/Versions | 1 +
sysdeps/unix/sysv/linux/aarch64/bits/rseq.h | 43 ++++
sysdeps/unix/sysv/linux/aarch64/libc.abilist | 1 +
sysdeps/unix/sysv/linux/alpha/libc.abilist | 1 +
sysdeps/unix/sysv/linux/arm/be/libc.abilist | 1 +
sysdeps/unix/sysv/linux/arm/bits/rseq.h | 83 +++++++
sysdeps/unix/sysv/linux/arm/le/libc.abilist | 1 +
sysdeps/unix/sysv/linux/bits/rseq.h | 29 +++
sysdeps/unix/sysv/linux/csky/libc.abilist | 1 +
sysdeps/unix/sysv/linux/hppa/libc.abilist | 1 +
sysdeps/unix/sysv/linux/i386/libc.abilist | 1 +
sysdeps/unix/sysv/linux/ia64/libc.abilist | 1 +
.../sysv/linux/m68k/coldfire/libc.abilist | 1 +
.../unix/sysv/linux/m68k/m680x0/libc.abilist | 1 +
.../sysv/linux/microblaze/be/libc.abilist | 1 +
.../sysv/linux/microblaze/le/libc.abilist | 1 +
sysdeps/unix/sysv/linux/mips/bits/rseq.h | 62 +++++
.../sysv/linux/mips/mips32/fpu/libc.abilist | 1 +
.../sysv/linux/mips/mips32/nofpu/libc.abilist | 1 +
.../sysv/linux/mips/mips64/n32/libc.abilist | 1 +
.../sysv/linux/mips/mips64/n64/libc.abilist | 1 +
sysdeps/unix/sysv/linux/nios2/libc.abilist | 1 +
sysdeps/unix/sysv/linux/powerpc/bits/rseq.h | 37 +++
.../linux/powerpc/powerpc32/fpu/libc.abilist | 1 +
.../powerpc/powerpc32/nofpu/libc.abilist | 1 +
.../linux/powerpc/powerpc64/be/libc.abilist | 1 +
.../linux/powerpc/powerpc64/le/libc.abilist | 1 +
.../unix/sysv/linux/riscv/rv64/libc.abilist | 1 +
sysdeps/unix/sysv/linux/rseq-internal.h | 73 ++++++
sysdeps/unix/sysv/linux/rseq-sym.c | 26 ++
sysdeps/unix/sysv/linux/s390/bits/rseq.h | 37 +++
.../unix/sysv/linux/s390/s390-32/libc.abilist | 1 +
.../unix/sysv/linux/s390/s390-64/libc.abilist | 1 +
sysdeps/unix/sysv/linux/sh/be/libc.abilist | 1 +
sysdeps/unix/sysv/linux/sh/le/libc.abilist | 1 +
.../sysv/linux/sparc/sparc32/libc.abilist | 1 +
.../sysv/linux/sparc/sparc64/libc.abilist | 1 +
sysdeps/unix/sysv/linux/sys/rseq.h | 228 ++++++++++++++++++
sysdeps/unix/sysv/linux/x86/bits/rseq.h | 30 +++
.../unix/sysv/linux/x86_64/64/libc.abilist | 1 +
.../unix/sysv/linux/x86_64/x32/libc.abilist | 1 +
47 files changed, 798 insertions(+), 2 deletions(-)
create mode 100644 sysdeps/generic/rseq-internal.h
create mode 100644 sysdeps/unix/sysv/linux/aarch64/bits/rseq.h
create mode 100644 sysdeps/unix/sysv/linux/arm/bits/rseq.h
create mode 100644 sysdeps/unix/sysv/linux/bits/rseq.h
create mode 100644 sysdeps/unix/sysv/linux/mips/bits/rseq.h
create mode 100644 sysdeps/unix/sysv/linux/powerpc/bits/rseq.h
create mode 100644 sysdeps/unix/sysv/linux/rseq-internal.h
create mode 100644 sysdeps/unix/sysv/linux/rseq-sym.c
create mode 100644 sysdeps/unix/sysv/linux/s390/bits/rseq.h
create mode 100644 sysdeps/unix/sysv/linux/sys/rseq.h
create mode 100644 sysdeps/unix/sysv/linux/x86/bits/rseq.h

diff --git a/NEWS b/NEWS
index 55389b8466..4ac5d62e09 100644
--- a/NEWS
+++ b/NEWS
@@ -27,6 +27,16 @@ Major new features:
several APIs have been annotated with GCC 'access' attribute. This
should help GCC 10 issue better warnings.

+* Support for automatically registering threads with the Linux rseq
+ system call has been added. This system call is implemented starting
+ from Linux 4.18. The Restartable Sequences ABI accelerates user-space
+ operations on per-cpu data. It allows user-space to perform updates
+ on per-cpu data without requiring heavy-weight atomic operations.
+ Automatically registering threads allows all libraries, including libc,
+ to make immediate use of the rseq support by using the documented ABI.
+ The GNU C Library manual has details on integration of Restartable
+ Sequences.
+
Deprecated and removed features, and other changes affecting compatibility:

* The deprecated <sys/sysctl.h> header and the sysctl function have been
diff --git a/elf/libc_early_init.c b/elf/libc_early_init.c
index e6c64fb526..f0fcf6448e 100644
--- a/elf/libc_early_init.c
+++ b/elf/libc_early_init.c
@@ -18,10 +18,14 @@

#include <ctype.h>
#include <libc-early-init.h>
+#include <rseq-internal.h>

void
__libc_early_init (_Bool initial)
{
/* Initialize ctype data. */
__ctype_init ();
+ /* Register rseq ABI to the kernel for the main program's libc. */
+ if (initial)
+ rseq_register_current_thread ();
}
diff --git a/manual/threads.texi b/manual/threads.texi
index a425635179..6ec9fc7cd8 100644
--- a/manual/threads.texi
+++ b/manual/threads.texi
@@ -627,6 +627,8 @@ the standard.
threads in a process.
* Waiting with Explicit Clocks:: Functions for waiting with an
explicit clock specification.
+* Restartable Sequences:: Linux-specific Restartable Sequences
+ integration.
@end menu

@node Default Thread Attributes
@@ -771,6 +773,67 @@ Behaves like @code{pthread_timedjoin_np} except that the absolute time in
@var{abstime} is measured against the clock specified by @var{clockid}.
@end deftypefun

+@node Restartable Sequences
+@subsubsection Restartable Sequences
+
+This section describes Restartable Sequences integration for
+@theglibc{}. This functionality is only available on Linux.
+
+@deftypevar {struct rseq} __rseq_abi
+@standards{Linux, sys/rseq.h}
+@Theglibc{} implements a @code{__rseq_abi} TLS symbol to interact with
+the Restartable Sequences system call. The layout of this structure is
+defined by the @file{sys/rseq.h} header. Registration of each thread's
+@code{__rseq_abi} is performed by @theglibc{} at library initialization
+and thread creation.
+
+The main executable and shared libraries may either have an undefined
+@code{__rseq_abi} TLS symbol, or define their own, with the same
+declaration as the one present in @file{sys/rseq.h}. The dynamic linker
+will ensure that only one of those available symbols will be used at
+runtime across the process.
+
+If the main executable or shared libraries observe an uninitialized
+@code{__rseq_abi.cpu_id} field (value @code{RSEQ_CPU_ID_UNINITIALIZED}),
+they may perform rseq registration to the kernel: this means either
+glibc was prevented from doing the registration, or an older glibc
+version, which does not include rseq support, is in use. When the main
+executable or a library thus takes ownership of the registration, the
+memory used to hold the @code{__rseq_abi} TLS variable must stay
+allocated, and is not re-used, until the very end of the thread lifetime
+or until an explicit rseq unregistration for that thread is performed.
+It is not recommended to @code{dlclose} libraries owning the
+@code{__rseq_abi} TLS variable.
+
+Users of the @code{__rseq_abi} TLS symbol can store the address of a
+@code{struct rseq_cs} to the @code{__rseq_abi.rseq_cs} TLS variable,
+thus informing the kernel that it enters a Restartable Sequence critical
+section. This pointer and the code areas it itself points to must not
+be left pointing to memory areas which are freed or re-used. Several
+approaches can guarantee this. If the application or library can
+guarantee that the memory used to hold the @code{struct rseq_cs} and the
+code areas it refers to are never freed or re-used, no special action
+must be taken. Else, before that memory is re-used of freed, the
+application is responsible for setting the @code{__rseq_abi.rseq_cs} TLS
+variable to @code{NULL} in each thread's TLS to guarantee that it does
+not leak dangling references. Because the application does not
+typically have knowledge of libraries' use of Restartable Sequences, it
+is recommended that libraries using Restartable Sequences which may end
+up freeing or re-using their memory set the @code{__rseq_abi.rseq_cs}
+TLS variable to @code{NULL} before returning from library functions
+which use Restartable Sequences.
+
+@end deftypevar
+
+@deftypevr Macro int RSEQ_SIG
+@standards{Linux, sys/rseq.h}
+Each supported architecture provides a @code{RSEQ_SIG} macro in
+@file{sys/rseq.h} which contains a signature. That 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.
+@end deftypevr
+
@c FIXME these are undocumented:
@c pthread_atfork
@c pthread_attr_destroy
diff --git a/nptl/pthread_create.c b/nptl/pthread_create.c
index a43089065c..e04a1df7b3 100644
--- a/nptl/pthread_create.c
+++ b/nptl/pthread_create.c
@@ -33,6 +33,7 @@
#include <default-sched.h>
#include <futex-internal.h>
#include <tls-setup.h>
+#include <rseq-internal.h>
#include "libioP.h"

#include <shlib-compat.h>
@@ -384,6 +385,9 @@ START_THREAD_DEFN
/* Initialize pointers to locale data. */
__ctype_init ();

+ /* Register rseq TLS to the kernel. */
+ rseq_register_current_thread ();
+
#ifndef __ASSUME_SET_ROBUST_LIST
if (__set_robust_list_avail >= 0)
#endif
@@ -579,6 +583,15 @@ START_THREAD_DEFN
process is really dead since 'clone' got passed the CLONE_CHILD_CLEARTID
flag. The 'tid' field in the TCB will be set to zero.

+ rseq TLS is still registered at this point. Rely on implicit
+ unregistration performed by the kernel on thread teardown. This is not a
+ problem because the rseq TLS lives on the stack, and the stack outlives
+ the thread. If TCB allocation is ever changed, additional steps may be
+ required, such as performing explicit rseq unregistration before
+ reclaiming the rseq TLS area memory. It is NOT sufficient to block
+ signals because the kernel may write to the rseq area even without
+ signals.
+
The exit code is zero since in case all threads exit by calling
'pthread_exit' the exit status must be 0 (zero). */
__exit_thread ();
diff --git a/sysdeps/generic/rseq-internal.h b/sysdeps/generic/rseq-internal.h
new file mode 100644
index 0000000000..16f197397f
--- /dev/null
+++ b/sysdeps/generic/rseq-internal.h
@@ -0,0 +1,26 @@
+/* Restartable Sequences internal API. Stub version.
+ Copyright (C) 2020 Free Software Foundation, Inc.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <https://www.gnu.org/licenses/>. */
+
+#ifndef RSEQ_INTERNAL_H
+#define RSEQ_INTERNAL_H
+
+static inline void
+rseq_register_current_thread (void)
+{
+}
+
+#endif /* rseq-internal.h */
diff --git a/sysdeps/unix/sysv/linux/Makefile b/sysdeps/unix/sysv/linux/Makefile
index e02065dc8d..e855db2cb9 100644
--- a/sysdeps/unix/sysv/linux/Makefile
+++ b/sysdeps/unix/sysv/linux/Makefile
@@ -41,7 +41,7 @@ update-syscall-lists: arch-syscall.h
endif

ifeq ($(subdir),csu)
-sysdep_routines += errno-loc
+sysdep_routines += errno-loc rseq-sym
endif

ifeq ($(subdir),assert)
@@ -92,7 +92,8 @@ sysdep_headers += sys/mount.h sys/acct.h \
bits/termios-c_lflag.h bits/termios-tcflow.h \
bits/termios-misc.h \
bits/types/struct_semid_ds.h \
- bits/ipc-perm.h
+ bits/ipc-perm.h \
+ sys/rseq.h bits/rseq.h

tests += tst-clone tst-clone2 tst-clone3 tst-fanotify tst-personality \
tst-quota tst-sync_file_range tst-sysconf-iov_max tst-ttyname \
diff --git a/sysdeps/unix/sysv/linux/Versions b/sysdeps/unix/sysv/linux/Versions
index 9a58dda9f2..52ca223ab2 100644
--- a/sysdeps/unix/sysv/linux/Versions
+++ b/sysdeps/unix/sysv/linux/Versions
@@ -178,6 +178,7 @@ libc {
getdents64; gettid; tgkill;
}
GLIBC_2.32 {
+ __rseq_abi;
}
GLIBC_PRIVATE {
# functions used in other libraries
diff --git a/sysdeps/unix/sysv/linux/aarch64/bits/rseq.h b/sysdeps/unix/sysv/linux/aarch64/bits/rseq.h
new file mode 100644
index 0000000000..b6f6e536f4
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/aarch64/bits/rseq.h
@@ -0,0 +1,43 @@
+/* Restartable Sequences Linux aarch64 architecture header.
+ Copyright (C) 2020 Free Software Foundation, Inc.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <https://www.gnu.org/licenses/>. */
+
+#ifndef _SYS_RSEQ_H
+# error "Never use <bits/rseq.h> directly; include <sys/rseq.h> instead."
+#endif
+
+/* RSEQ_SIG is a signature required before each abort handler code.
+
+ It is a 32-bit value that maps to actual architecture code compiled
+ into applications and libraries. It needs to be defined for each
+ architecture. When choosing this value, it needs to be taken into
+ account that generating invalid instructions may have ill effects on
+ tools like objdump, and may also have impact on the CPU speculative
+ execution efficiency in some cases.
+
+ aarch64 -mbig-endian generates mixed endianness code vs data:
+ little-endian code and big-endian data. Ensure the RSEQ_SIG signature
+ matches code endianness. */
+
+#define RSEQ_SIG_CODE 0xd428bc00 /* BRK #0x45E0. */
+
+#ifdef __AARCH64EB__
+# define RSEQ_SIG_DATA 0x00bc28d4 /* BRK #0x45E0. */
+#else
+# define RSEQ_SIG_DATA RSEQ_SIG_CODE
+#endif
+
+#define RSEQ_SIG RSEQ_SIG_DATA
diff --git a/sysdeps/unix/sysv/linux/aarch64/libc.abilist b/sysdeps/unix/sysv/linux/aarch64/libc.abilist
index 6dc59b38b0..2324987a51 100644
--- a/sysdeps/unix/sysv/linux/aarch64/libc.abilist
+++ b/sysdeps/unix/sysv/linux/aarch64/libc.abilist
@@ -2149,6 +2149,7 @@ GLIBC_2.30 getdents64 F
GLIBC_2.30 gettid F
GLIBC_2.30 tgkill F
GLIBC_2.30 twalk_r F
+GLIBC_2.32 __rseq_abi T 0x20
GLIBC_2.32 pthread_attr_setaffinity_np F
GLIBC_2.32 pthread_getaffinity_np F
GLIBC_2.32 pthread_getattr_np F
diff --git a/sysdeps/unix/sysv/linux/alpha/libc.abilist b/sysdeps/unix/sysv/linux/alpha/libc.abilist
index fd628bcd28..95d6a3323b 100644
--- a/sysdeps/unix/sysv/linux/alpha/libc.abilist
+++ b/sysdeps/unix/sysv/linux/alpha/libc.abilist
@@ -2231,6 +2231,7 @@ GLIBC_2.30 getdents64 F
GLIBC_2.30 gettid F
GLIBC_2.30 tgkill F
GLIBC_2.30 twalk_r F
+GLIBC_2.32 __rseq_abi T 0x20
GLIBC_2.32 pthread_attr_setaffinity_np F
GLIBC_2.32 pthread_getaffinity_np F
GLIBC_2.32 pthread_getattr_np F
diff --git a/sysdeps/unix/sysv/linux/arm/be/libc.abilist b/sysdeps/unix/sysv/linux/arm/be/libc.abilist
index d0b1cd24c9..8fc5e07fa5 100644
--- a/sysdeps/unix/sysv/linux/arm/be/libc.abilist
+++ b/sysdeps/unix/sysv/linux/arm/be/libc.abilist
@@ -133,6 +133,7 @@ GLIBC_2.30 twalk_r F
GLIBC_2.31 msgctl F
GLIBC_2.31 semctl F
GLIBC_2.31 shmctl F
+GLIBC_2.32 __rseq_abi T 0x20
GLIBC_2.32 pthread_attr_setaffinity_np F
GLIBC_2.32 pthread_getaffinity_np F
GLIBC_2.32 pthread_getattr_np F
diff --git a/sysdeps/unix/sysv/linux/arm/bits/rseq.h b/sysdeps/unix/sysv/linux/arm/bits/rseq.h
new file mode 100644
index 0000000000..2bf780efcd
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/arm/bits/rseq.h
@@ -0,0 +1,83 @@
+/* Restartable Sequences Linux arm architecture header.
+ Copyright (C) 2020 Free Software Foundation, Inc.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <https://www.gnu.org/licenses/>. */
+
+#ifndef _SYS_RSEQ_H
+# error "Never use <bits/rseq.h> directly; include <sys/rseq.h> instead."
+#endif
+
+/*
+ RSEQ_SIG is a signature required before each abort handler code.
+
+ It is a 32-bit value that maps to actual architecture code compiled
+ into applications and libraries. It needs to be defined for each
+ architecture. When choosing this value, it needs to be taken into
+ account that generating invalid instructions may have ill effects on
+ tools like objdump, and may also have impact on the CPU speculative
+ execution efficiency in some cases.
+
+ - ARM little endian
+
+ RSEQ_SIG uses the udf A32 instruction with an uncommon immediate operand
+ value 0x5de3. This traps if user-space reaches this instruction by mistake,
+ and the uncommon operand ensures the kernel does not move the instruction
+ pointer to attacker-controlled code on rseq abort.
+
+ The instruction pattern in the A32 instruction set is:
+
+ e7f5def3 udf #24035 ; 0x5de3
+
+ This translates to the following instruction pattern in the T16 instruction
+ set:
+
+ little endian:
+ def3 udf #243 ; 0xf3
+ e7f5 b.n <7f5>
+
+ - ARMv6+ big endian (BE8):
+
+ ARMv6+ -mbig-endian generates mixed endianness code vs data: little-endian
+ code and big-endian data. The data value of the signature needs to have its
+ byte order reversed to generate the trap instruction:
+
+ Data: 0xf3def5e7
+
+ Translates to this A32 instruction pattern:
+
+ e7f5def3 udf #24035 ; 0x5de3
+
+ Translates to this T16 instruction pattern:
+
+ def3 udf #243 ; 0xf3
+ e7f5 b.n <7f5>
+
+ - Prior to ARMv6 big endian (BE32):
+
+ Prior to ARMv6, -mbig-endian generates big-endian code and data
+ (which match), so the endianness of the data representation of the
+ signature should not be reversed. However, the choice between BE32
+ and BE8 is done by the linker, so we cannot know whether code and
+ data endianness will be mixed before the linker is invoked. So rather
+ than try to play tricks with the linker, the rseq signature is simply
+ data (not a trap instruction) prior to ARMv6 on big endian. This is
+ why the signature is expressed as data (.word) rather than as
+ instruction (.inst) in assembler. */
+
+#ifdef __ARMEB__
+# define RSEQ_SIG 0xf3def5e7 /* udf #24035 ; 0x5de3 (ARMv6+) */
+#else
+# define RSEQ_SIG 0xe7f5def3 /* udf #24035 ; 0x5de3 */
+#endif
diff --git a/sysdeps/unix/sysv/linux/arm/le/libc.abilist b/sysdeps/unix/sysv/linux/arm/le/libc.abilist
index 3dde0ef8bd..95bb8ca254 100644
--- a/sysdeps/unix/sysv/linux/arm/le/libc.abilist
+++ b/sysdeps/unix/sysv/linux/arm/le/libc.abilist
@@ -130,6 +130,7 @@ GLIBC_2.30 getdents64 F
GLIBC_2.30 gettid F
GLIBC_2.30 tgkill F
GLIBC_2.30 twalk_r F
+GLIBC_2.32 __rseq_abi T 0x20
GLIBC_2.32 pthread_attr_setaffinity_np F
GLIBC_2.32 pthread_getaffinity_np F
GLIBC_2.32 pthread_getattr_np F
diff --git a/sysdeps/unix/sysv/linux/bits/rseq.h b/sysdeps/unix/sysv/linux/bits/rseq.h
new file mode 100644
index 0000000000..014c08fe0f
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/bits/rseq.h
@@ -0,0 +1,29 @@
+/* Restartable Sequences architecture header. Stub version.
+ Copyright (C) 2020 Free Software Foundation, Inc.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <https://www.gnu.org/licenses/>. */
+
+#ifndef _SYS_RSEQ_H
+# error "Never use <bits/rseq.h> directly; include <sys/rseq.h> instead."
+#endif
+
+/* RSEQ_SIG is a signature required before each abort handler code.
+
+ It is a 32-bit value that maps to actual architecture code compiled
+ into applications and libraries. It needs to be defined for each
+ architecture. When choosing this value, it needs to be taken into
+ account that generating invalid instructions may have ill effects on
+ tools like objdump, and may also have impact on the CPU speculative
+ execution efficiency in some cases. */
diff --git a/sysdeps/unix/sysv/linux/csky/libc.abilist b/sysdeps/unix/sysv/linux/csky/libc.abilist
index 4db9bbd971..0694c92a84 100644
--- a/sysdeps/unix/sysv/linux/csky/libc.abilist
+++ b/sysdeps/unix/sysv/linux/csky/libc.abilist
@@ -2093,6 +2093,7 @@ GLIBC_2.30 getdents64 F
GLIBC_2.30 gettid F
GLIBC_2.30 tgkill F
GLIBC_2.30 twalk_r F
+GLIBC_2.32 __rseq_abi T 0x20
GLIBC_2.32 pthread_attr_setaffinity_np F
GLIBC_2.32 pthread_getaffinity_np F
GLIBC_2.32 pthread_getattr_np F
diff --git a/sysdeps/unix/sysv/linux/hppa/libc.abilist b/sysdeps/unix/sysv/linux/hppa/libc.abilist
index 52aa86b191..cc8a270b5a 100644
--- a/sysdeps/unix/sysv/linux/hppa/libc.abilist
+++ b/sysdeps/unix/sysv/linux/hppa/libc.abilist
@@ -2052,6 +2052,7 @@ GLIBC_2.30 getdents64 F
GLIBC_2.30 gettid F
GLIBC_2.30 tgkill F
GLIBC_2.30 twalk_r F
+GLIBC_2.32 __rseq_abi T 0x20
GLIBC_2.32 pthread_attr_setaffinity_np F
GLIBC_2.32 pthread_getaffinity_np F
GLIBC_2.32 pthread_getattr_np F
diff --git a/sysdeps/unix/sysv/linux/i386/libc.abilist b/sysdeps/unix/sysv/linux/i386/libc.abilist
index 48ee395a64..3baa6c95c4 100644
--- a/sysdeps/unix/sysv/linux/i386/libc.abilist
+++ b/sysdeps/unix/sysv/linux/i386/libc.abilist
@@ -2218,6 +2218,7 @@ GLIBC_2.30 getdents64 F
GLIBC_2.30 gettid F
GLIBC_2.30 tgkill F
GLIBC_2.30 twalk_r F
+GLIBC_2.32 __rseq_abi T 0x20
GLIBC_2.32 pthread_attr_setaffinity_np F
GLIBC_2.32 pthread_getaffinity_np F
GLIBC_2.32 pthread_getattr_np F
diff --git a/sysdeps/unix/sysv/linux/ia64/libc.abilist b/sysdeps/unix/sysv/linux/ia64/libc.abilist
index 34458f348f..bf8a5b76df 100644
--- a/sysdeps/unix/sysv/linux/ia64/libc.abilist
+++ b/sysdeps/unix/sysv/linux/ia64/libc.abilist
@@ -2084,6 +2084,7 @@ GLIBC_2.30 getdents64 F
GLIBC_2.30 gettid F
GLIBC_2.30 tgkill F
GLIBC_2.30 twalk_r F
+GLIBC_2.32 __rseq_abi T 0x20
GLIBC_2.32 pthread_attr_setaffinity_np F
GLIBC_2.32 pthread_getaffinity_np F
GLIBC_2.32 pthread_getattr_np F
diff --git a/sysdeps/unix/sysv/linux/m68k/coldfire/libc.abilist b/sysdeps/unix/sysv/linux/m68k/coldfire/libc.abilist
index 377326b12c..2f0228d15f 100644
--- a/sysdeps/unix/sysv/linux/m68k/coldfire/libc.abilist
+++ b/sysdeps/unix/sysv/linux/m68k/coldfire/libc.abilist
@@ -134,6 +134,7 @@ GLIBC_2.30 twalk_r F
GLIBC_2.31 msgctl F
GLIBC_2.31 semctl F
GLIBC_2.31 shmctl F
+GLIBC_2.32 __rseq_abi T 0x20
GLIBC_2.32 pthread_attr_setaffinity_np F
GLIBC_2.32 pthread_getaffinity_np F
GLIBC_2.32 pthread_getattr_np F
diff --git a/sysdeps/unix/sysv/linux/m68k/m680x0/libc.abilist b/sysdeps/unix/sysv/linux/m68k/m680x0/libc.abilist
index 81eea10680..6a54bc5637 100644
--- a/sysdeps/unix/sysv/linux/m68k/m680x0/libc.abilist
+++ b/sysdeps/unix/sysv/linux/m68k/m680x0/libc.abilist
@@ -2164,6 +2164,7 @@ GLIBC_2.30 twalk_r F
GLIBC_2.31 msgctl F
GLIBC_2.31 semctl F
GLIBC_2.31 shmctl F
+GLIBC_2.32 __rseq_abi T 0x20
GLIBC_2.32 pthread_attr_setaffinity_np F
GLIBC_2.32 pthread_getaffinity_np F
GLIBC_2.32 pthread_getattr_np F
diff --git a/sysdeps/unix/sysv/linux/microblaze/be/libc.abilist b/sysdeps/unix/sysv/linux/microblaze/be/libc.abilist
index ff75663747..388608128a 100644
--- a/sysdeps/unix/sysv/linux/microblaze/be/libc.abilist
+++ b/sysdeps/unix/sysv/linux/microblaze/be/libc.abilist
@@ -2144,6 +2144,7 @@ GLIBC_2.30 twalk_r F
GLIBC_2.31 msgctl F
GLIBC_2.31 semctl F
GLIBC_2.31 shmctl F
+GLIBC_2.32 __rseq_abi T 0x20
GLIBC_2.32 pthread_attr_setaffinity_np F
GLIBC_2.32 pthread_getaffinity_np F
GLIBC_2.32 pthread_getattr_np F
diff --git a/sysdeps/unix/sysv/linux/microblaze/le/libc.abilist b/sysdeps/unix/sysv/linux/microblaze/le/libc.abilist
index e9a6375dfc..92b9d4f1c6 100644
--- a/sysdeps/unix/sysv/linux/microblaze/le/libc.abilist
+++ b/sysdeps/unix/sysv/linux/microblaze/le/libc.abilist
@@ -2141,6 +2141,7 @@ GLIBC_2.30 getdents64 F
GLIBC_2.30 gettid F
GLIBC_2.30 tgkill F
GLIBC_2.30 twalk_r F
+GLIBC_2.32 __rseq_abi T 0x20
GLIBC_2.32 pthread_attr_setaffinity_np F
GLIBC_2.32 pthread_getaffinity_np F
GLIBC_2.32 pthread_getattr_np F
diff --git a/sysdeps/unix/sysv/linux/mips/bits/rseq.h b/sysdeps/unix/sysv/linux/mips/bits/rseq.h
new file mode 100644
index 0000000000..fa945fc7c1
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/mips/bits/rseq.h
@@ -0,0 +1,62 @@
+/* Restartable Sequences Linux mips architecture header.
+ Copyright (C) 2020 Free Software Foundation, Inc.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <https://www.gnu.org/licenses/>. */
+
+#ifndef _SYS_RSEQ_H
+# error "Never use <bits/rseq.h> directly; include <sys/rseq.h> instead."
+#endif
+
+/* RSEQ_SIG is a signature required before each abort handler code.
+
+ It is a 32-bit value that maps to actual architecture code compiled
+ into applications and libraries. It needs to be defined for each
+ architecture. When choosing this value, it needs to be taken into
+ account that generating invalid instructions may have ill effects on
+ tools like objdump, and may also have impact on the CPU speculative
+ execution efficiency in some cases.
+
+ RSEQ_SIG uses the break instruction. The instruction pattern is:
+
+ On MIPS:
+ 0350000d break 0x350
+
+ On nanoMIPS:
+ 00100350 break 0x350
+
+ On microMIPS:
+ 0000d407 break 0x350
+
+ For nanoMIPS32 and microMIPS, the instruction stream is encoded as
+ 16-bit halfwords, so the signature halfwords need to be swapped
+ accordingly for little-endian. */
+
+#if defined (__nanomips__)
+# ifdef __MIPSEL__
+# define RSEQ_SIG 0x03500010
+# else
+# define RSEQ_SIG 0x00100350
+# endif
+#elif defined (__mips_micromips)
+# ifdef __MIPSEL__
+# define RSEQ_SIG 0xd4070000
+# else
+# define RSEQ_SIG 0x0000d407
+# endif
+#elif defined (__mips__)
+# define RSEQ_SIG 0x0350000d
+#else
+/* Unknown MIPS architecture. */
+#endif
diff --git a/sysdeps/unix/sysv/linux/mips/mips32/fpu/libc.abilist b/sysdeps/unix/sysv/linux/mips/mips32/fpu/libc.abilist
index 598fc488c7..fa1f90b444 100644
--- a/sysdeps/unix/sysv/linux/mips/mips32/fpu/libc.abilist
+++ b/sysdeps/unix/sysv/linux/mips/mips32/fpu/libc.abilist
@@ -2135,6 +2135,7 @@ GLIBC_2.30 getdents64 F
GLIBC_2.30 gettid F
GLIBC_2.30 tgkill F
GLIBC_2.30 twalk_r F
+GLIBC_2.32 __rseq_abi T 0x20
GLIBC_2.32 pthread_attr_setaffinity_np F
GLIBC_2.32 pthread_getaffinity_np F
GLIBC_2.32 pthread_getattr_np F
diff --git a/sysdeps/unix/sysv/linux/mips/mips32/nofpu/libc.abilist b/sysdeps/unix/sysv/linux/mips/mips32/nofpu/libc.abilist
index 77e8d6b155..520bd083ef 100644
--- a/sysdeps/unix/sysv/linux/mips/mips32/nofpu/libc.abilist
+++ b/sysdeps/unix/sysv/linux/mips/mips32/nofpu/libc.abilist
@@ -2133,6 +2133,7 @@ GLIBC_2.30 getdents64 F
GLIBC_2.30 gettid F
GLIBC_2.30 tgkill F
GLIBC_2.30 twalk_r F
+GLIBC_2.32 __rseq_abi T 0x20
GLIBC_2.32 pthread_attr_setaffinity_np F
GLIBC_2.32 pthread_getaffinity_np F
GLIBC_2.32 pthread_getattr_np F
diff --git a/sysdeps/unix/sysv/linux/mips/mips64/n32/libc.abilist b/sysdeps/unix/sysv/linux/mips/mips64/n32/libc.abilist
index a3aad2487f..c1c7ecad94 100644
--- a/sysdeps/unix/sysv/linux/mips/mips64/n32/libc.abilist
+++ b/sysdeps/unix/sysv/linux/mips/mips64/n32/libc.abilist
@@ -2141,6 +2141,7 @@ GLIBC_2.30 getdents64 F
GLIBC_2.30 gettid F
GLIBC_2.30 tgkill F
GLIBC_2.30 twalk_r F
+GLIBC_2.32 __rseq_abi T 0x20
GLIBC_2.32 pthread_attr_setaffinity_np F
GLIBC_2.32 pthread_getaffinity_np F
GLIBC_2.32 pthread_getattr_np F
diff --git a/sysdeps/unix/sysv/linux/mips/mips64/n64/libc.abilist b/sysdeps/unix/sysv/linux/mips/mips64/n64/libc.abilist
index c074f612f5..c788cfc6b5 100644
--- a/sysdeps/unix/sysv/linux/mips/mips64/n64/libc.abilist
+++ b/sysdeps/unix/sysv/linux/mips/mips64/n64/libc.abilist
@@ -2135,6 +2135,7 @@ GLIBC_2.30 getdents64 F
GLIBC_2.30 gettid F
GLIBC_2.30 tgkill F
GLIBC_2.30 twalk_r F
+GLIBC_2.32 __rseq_abi T 0x20
GLIBC_2.32 pthread_attr_setaffinity_np F
GLIBC_2.32 pthread_getaffinity_np F
GLIBC_2.32 pthread_getattr_np F
diff --git a/sysdeps/unix/sysv/linux/nios2/libc.abilist b/sysdeps/unix/sysv/linux/nios2/libc.abilist
index d1c638acb9..2b37f9f2f6 100644
--- a/sysdeps/unix/sysv/linux/nios2/libc.abilist
+++ b/sysdeps/unix/sysv/linux/nios2/libc.abilist
@@ -2182,6 +2182,7 @@ GLIBC_2.30 getdents64 F
GLIBC_2.30 gettid F
GLIBC_2.30 tgkill F
GLIBC_2.30 twalk_r F
+GLIBC_2.32 __rseq_abi T 0x20
GLIBC_2.32 pthread_attr_setaffinity_np F
GLIBC_2.32 pthread_getaffinity_np F
GLIBC_2.32 pthread_getattr_np F
diff --git a/sysdeps/unix/sysv/linux/powerpc/bits/rseq.h b/sysdeps/unix/sysv/linux/powerpc/bits/rseq.h
new file mode 100644
index 0000000000..0dc608ebd5
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/powerpc/bits/rseq.h
@@ -0,0 +1,37 @@
+/* Restartable Sequences Linux powerpc architecture header.
+ Copyright (C) 2020 Free Software Foundation, Inc.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <https://www.gnu.org/licenses/>. */
+
+#ifndef _SYS_RSEQ_H
+# error "Never use <bits/rseq.h> directly; include <sys/rseq.h> instead."
+#endif
+
+/* RSEQ_SIG is a signature required before each abort handler code.
+
+ It is a 32-bit value that maps to actual architecture code compiled
+ into applications and libraries. It needs to be defined for each
+ architecture. When choosing this value, it needs to be taken into
+ account that generating invalid instructions may have ill effects on
+ tools like objdump, and may also have impact on the CPU speculative
+ execution efficiency in some cases.
+
+ RSEQ_SIG uses the following trap instruction:
+
+ powerpc-be: 0f e5 00 0b twui r5,11
+ powerpc64-le: 0b 00 e5 0f twui r5,11
+ powerpc64-be: 0f e5 00 0b twui r5,11 */
+
+#define RSEQ_SIG 0x0fe5000b
diff --git a/sysdeps/unix/sysv/linux/powerpc/powerpc32/fpu/libc.abilist b/sysdeps/unix/sysv/linux/powerpc/powerpc32/fpu/libc.abilist
index bfc8185b0e..70b8eb37d0 100644
--- a/sysdeps/unix/sysv/linux/powerpc/powerpc32/fpu/libc.abilist
+++ b/sysdeps/unix/sysv/linux/powerpc/powerpc32/fpu/libc.abilist
@@ -2191,6 +2191,7 @@ GLIBC_2.30 getdents64 F
GLIBC_2.30 gettid F
GLIBC_2.30 tgkill F
GLIBC_2.30 twalk_r F
+GLIBC_2.32 __rseq_abi T 0x20
GLIBC_2.32 pthread_attr_setaffinity_np F
GLIBC_2.32 pthread_getaffinity_np F
GLIBC_2.32 pthread_getattr_np F
diff --git a/sysdeps/unix/sysv/linux/powerpc/powerpc32/nofpu/libc.abilist b/sysdeps/unix/sysv/linux/powerpc/powerpc32/nofpu/libc.abilist
index 9a889f1bc6..cec83b4929 100644
--- a/sysdeps/unix/sysv/linux/powerpc/powerpc32/nofpu/libc.abilist
+++ b/sysdeps/unix/sysv/linux/powerpc/powerpc32/nofpu/libc.abilist
@@ -2224,6 +2224,7 @@ GLIBC_2.30 getdents64 F
GLIBC_2.30 gettid F
GLIBC_2.30 tgkill F
GLIBC_2.30 twalk_r F
+GLIBC_2.32 __rseq_abi T 0x20
GLIBC_2.32 pthread_attr_setaffinity_np F
GLIBC_2.32 pthread_getaffinity_np F
GLIBC_2.32 pthread_getattr_np F
diff --git a/sysdeps/unix/sysv/linux/powerpc/powerpc64/be/libc.abilist b/sysdeps/unix/sysv/linux/powerpc/powerpc64/be/libc.abilist
index b69f4b126f..baa5b24bb5 100644
--- a/sysdeps/unix/sysv/linux/powerpc/powerpc64/be/libc.abilist
+++ b/sysdeps/unix/sysv/linux/powerpc/powerpc64/be/libc.abilist
@@ -2054,6 +2054,7 @@ GLIBC_2.30 getdents64 F
GLIBC_2.30 gettid F
GLIBC_2.30 tgkill F
GLIBC_2.30 twalk_r F
+GLIBC_2.32 __rseq_abi T 0x20
GLIBC_2.32 pthread_attr_setaffinity_np F
GLIBC_2.32 pthread_getaffinity_np F
GLIBC_2.32 pthread_getattr_np F
diff --git a/sysdeps/unix/sysv/linux/powerpc/powerpc64/le/libc.abilist b/sysdeps/unix/sysv/linux/powerpc/powerpc64/le/libc.abilist
index a07753847d..78b5ad53d3 100644
--- a/sysdeps/unix/sysv/linux/powerpc/powerpc64/le/libc.abilist
+++ b/sysdeps/unix/sysv/linux/powerpc/powerpc64/le/libc.abilist
@@ -2291,6 +2291,7 @@ GLIBC_2.32 __qecvtieee128_r F
GLIBC_2.32 __qfcvtieee128 F
GLIBC_2.32 __qfcvtieee128_r F
GLIBC_2.32 __qgcvtieee128 F
+GLIBC_2.32 __rseq_abi T 0x20
GLIBC_2.32 __scanfieee128 F
GLIBC_2.32 __snprintf_chkieee128 F
GLIBC_2.32 __snprintfieee128 F
diff --git a/sysdeps/unix/sysv/linux/riscv/rv64/libc.abilist b/sysdeps/unix/sysv/linux/riscv/rv64/libc.abilist
index 6d5a52dc1a..a8fa4b134a 100644
--- a/sysdeps/unix/sysv/linux/riscv/rv64/libc.abilist
+++ b/sysdeps/unix/sysv/linux/riscv/rv64/libc.abilist
@@ -2111,6 +2111,7 @@ GLIBC_2.30 getdents64 F
GLIBC_2.30 gettid F
GLIBC_2.30 tgkill F
GLIBC_2.30 twalk_r F
+GLIBC_2.32 __rseq_abi T 0x20
GLIBC_2.32 pthread_attr_setaffinity_np F
GLIBC_2.32 pthread_getaffinity_np F
GLIBC_2.32 pthread_getattr_np F
diff --git a/sysdeps/unix/sysv/linux/rseq-internal.h b/sysdeps/unix/sysv/linux/rseq-internal.h
new file mode 100644
index 0000000000..8f6772ca1d
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/rseq-internal.h
@@ -0,0 +1,73 @@
+/* Restartable Sequences internal API. Linux implementation.
+ Copyright (C) 2020 Free Software Foundation, Inc.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <https://www.gnu.org/licenses/>. */
+
+#ifndef RSEQ_INTERNAL_H
+#define RSEQ_INTERNAL_H
+
+#include <sysdep.h>
+#include <errno.h>
+#include <kernel-features.h>
+#include <stdio.h>
+#include <sys/rseq.h>
+
+#ifdef RSEQ_SIG
+static inline void
+rseq_register_current_thread (void)
+{
+ int ret;
+
+ if (__rseq_abi.cpu_id != RSEQ_CPU_ID_UNINITIALIZED)
+ __libc_fatal ("glibc fatal error: "
+ "rseq already initialized for this thread\n");
+ ret = INTERNAL_SYSCALL_CALL (rseq, &__rseq_abi, sizeof (struct rseq),
+ 0, RSEQ_SIG);
+ if (INTERNAL_SYSCALL_ERROR_P (ret))
+ {
+ const char *msg = NULL;
+
+ switch (INTERNAL_SYSCALL_ERRNO (ret))
+ {
+ case ENOSYS: /* rseq system call not implemented. */
+ case EPERM: /* rseq system call filtered by seccomp. */
+ case EACCES: /* rseq system call filtered by seccomp. */
+ __rseq_abi.cpu_id = RSEQ_CPU_ID_REGISTRATION_FAILED;
+ break;
+ case EBUSY:
+ msg = "glibc fatal error: rseq already registered for this thread\n";
+ break;
+ case EFAULT:
+ msg = "glibc fatal error: rseq parameter is an invalid address\n";
+ break;
+ case EINVAL:
+ msg = "glibc fatal error: rseq parameters are invalid\n";
+ break;
+ default:
+ msg = "glibc fatal error: unexpected rseq errno\n";
+ break;
+ }
+ if (msg != NULL)
+ __libc_fatal (msg);
+ }
+}
+#else /* RSEQ_SIG */
+static inline void
+rseq_register_current_thread (void)
+{
+}
+#endif /* RSEQ_SIG */
+
+#endif /* rseq-internal.h */
diff --git a/sysdeps/unix/sysv/linux/rseq-sym.c b/sysdeps/unix/sysv/linux/rseq-sym.c
new file mode 100644
index 0000000000..090093408f
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/rseq-sym.c
@@ -0,0 +1,26 @@
+/* Restartable Sequences exported symbols. Linux Implementation.
+ Copyright (C) 2020 Free Software Foundation, Inc.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <https://www.gnu.org/licenses/>. */
+
+#include <sys/syscall.h>
+#include <stdint.h>
+#include <kernel-features.h>
+#include <sys/rseq.h>
+
+__thread struct rseq __rseq_abi =
+ {
+ .cpu_id = RSEQ_CPU_ID_UNINITIALIZED,
+ };
diff --git a/sysdeps/unix/sysv/linux/s390/bits/rseq.h b/sysdeps/unix/sysv/linux/s390/bits/rseq.h
new file mode 100644
index 0000000000..3d6fd0cfb9
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/s390/bits/rseq.h
@@ -0,0 +1,37 @@
+/* Restartable Sequences Linux s390 architecture header.
+ Copyright (C) 2020 Free Software Foundation, Inc.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <https://www.gnu.org/licenses/>. */
+
+#ifndef _SYS_RSEQ_H
+# error "Never use <bits/rseq.h> directly; include <sys/rseq.h> instead."
+#endif
+
+/* RSEQ_SIG is a signature required before each abort handler code.
+
+ It is a 32-bit value that maps to actual architecture code compiled
+ into applications and libraries. It needs to be defined for each
+ architecture. When choosing this value, it needs to be taken into
+ account that generating invalid instructions may have ill effects on
+ tools like objdump, and may also have impact on the CPU speculative
+ execution efficiency in some cases.
+
+ RSEQ_SIG uses the trap4 instruction. As Linux does not make use of the
+ access-register mode nor the linkage stack this instruction will always
+ cause a special-operation exception (the trap-enabled bit in the DUCT
+ is and will stay 0). The instruction pattern is
+ b2 ff 0f ff trap4 4095(%r0) */
+
+#define RSEQ_SIG 0xB2FF0FFF
diff --git a/sysdeps/unix/sysv/linux/s390/s390-32/libc.abilist b/sysdeps/unix/sysv/linux/s390/s390-32/libc.abilist
index ae3849d3f6..c8ca4dcd52 100644
--- a/sysdeps/unix/sysv/linux/s390/s390-32/libc.abilist
+++ b/sysdeps/unix/sysv/linux/s390/s390-32/libc.abilist
@@ -2189,6 +2189,7 @@ GLIBC_2.30 twalk_r F
GLIBC_2.31 msgctl F
GLIBC_2.31 semctl F
GLIBC_2.31 shmctl F
+GLIBC_2.32 __rseq_abi T 0x20
GLIBC_2.32 pthread_attr_setaffinity_np F
GLIBC_2.32 pthread_getaffinity_np F
GLIBC_2.32 pthread_getattr_np F
diff --git a/sysdeps/unix/sysv/linux/s390/s390-64/libc.abilist b/sysdeps/unix/sysv/linux/s390/s390-64/libc.abilist
index 2eb931c02c..bc0c0b2403 100644
--- a/sysdeps/unix/sysv/linux/s390/s390-64/libc.abilist
+++ b/sysdeps/unix/sysv/linux/s390/s390-64/libc.abilist
@@ -2090,6 +2090,7 @@ GLIBC_2.30 getdents64 F
GLIBC_2.30 gettid F
GLIBC_2.30 tgkill F
GLIBC_2.30 twalk_r F
+GLIBC_2.32 __rseq_abi T 0x20
GLIBC_2.32 pthread_attr_setaffinity_np F
GLIBC_2.32 pthread_getaffinity_np F
GLIBC_2.32 pthread_getattr_np F
diff --git a/sysdeps/unix/sysv/linux/sh/be/libc.abilist b/sysdeps/unix/sysv/linux/sh/be/libc.abilist
index ce4f366fbb..3447af2eb5 100644
--- a/sysdeps/unix/sysv/linux/sh/be/libc.abilist
+++ b/sysdeps/unix/sysv/linux/sh/be/libc.abilist
@@ -2059,6 +2059,7 @@ GLIBC_2.30 twalk_r F
GLIBC_2.31 msgctl F
GLIBC_2.31 semctl F
GLIBC_2.31 shmctl F
+GLIBC_2.32 __rseq_abi T 0x20
GLIBC_2.32 pthread_attr_setaffinity_np F
GLIBC_2.32 pthread_getaffinity_np F
GLIBC_2.32 pthread_getattr_np F
diff --git a/sysdeps/unix/sysv/linux/sh/le/libc.abilist b/sysdeps/unix/sysv/linux/sh/le/libc.abilist
index f37a08ab09..73d5f364a3 100644
--- a/sysdeps/unix/sysv/linux/sh/le/libc.abilist
+++ b/sysdeps/unix/sysv/linux/sh/le/libc.abilist
@@ -2056,6 +2056,7 @@ GLIBC_2.30 getdents64 F
GLIBC_2.30 gettid F
GLIBC_2.30 tgkill F
GLIBC_2.30 twalk_r F
+GLIBC_2.32 __rseq_abi T 0x20
GLIBC_2.32 pthread_attr_setaffinity_np F
GLIBC_2.32 pthread_getaffinity_np F
GLIBC_2.32 pthread_getattr_np F
diff --git a/sysdeps/unix/sysv/linux/sparc/sparc32/libc.abilist b/sysdeps/unix/sysv/linux/sparc/sparc32/libc.abilist
index af3a5e2618..d5b33f1134 100644
--- a/sysdeps/unix/sysv/linux/sparc/sparc32/libc.abilist
+++ b/sysdeps/unix/sysv/linux/sparc/sparc32/libc.abilist
@@ -2180,6 +2180,7 @@ GLIBC_2.30 getdents64 F
GLIBC_2.30 gettid F
GLIBC_2.30 tgkill F
GLIBC_2.30 twalk_r F
+GLIBC_2.32 __rseq_abi T 0x20
GLIBC_2.32 pthread_attr_setaffinity_np F
GLIBC_2.32 pthread_getaffinity_np F
GLIBC_2.32 pthread_getattr_np F
diff --git a/sysdeps/unix/sysv/linux/sparc/sparc64/libc.abilist b/sysdeps/unix/sysv/linux/sparc/sparc64/libc.abilist
index 1fccc06f21..a38c0ce7d4 100644
--- a/sysdeps/unix/sysv/linux/sparc/sparc64/libc.abilist
+++ b/sysdeps/unix/sysv/linux/sparc/sparc64/libc.abilist
@@ -2107,6 +2107,7 @@ GLIBC_2.30 getdents64 F
GLIBC_2.30 gettid F
GLIBC_2.30 tgkill F
GLIBC_2.30 twalk_r F
+GLIBC_2.32 __rseq_abi T 0x20
GLIBC_2.32 pthread_attr_setaffinity_np F
GLIBC_2.32 pthread_getaffinity_np F
GLIBC_2.32 pthread_getattr_np F
diff --git a/sysdeps/unix/sysv/linux/sys/rseq.h b/sysdeps/unix/sysv/linux/sys/rseq.h
new file mode 100644
index 0000000000..afa839f8aa
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/sys/rseq.h
@@ -0,0 +1,228 @@
+/* Restartable Sequences exported symbols. Linux header.
+ Copyright (C) 2020 Free Software Foundation, Inc.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <https://www.gnu.org/licenses/>. */
+
+#ifndef _SYS_RSEQ_H
+#define _SYS_RSEQ_H 1
+
+/* Architecture-specific rseq signature. */
+#include <bits/rseq.h>
+
+#include <stdint.h>
+#include <sys/cdefs.h>
+
+#ifdef __has_include
+# if __has_include ("linux/rseq.h")
+# define __GLIBC_HAVE_KERNEL_RSEQ
+# endif
+#else
+# include <linux/version.h>
+# if LINUX_VERSION_CODE >= KERNEL_VERSION (4, 18, 0)
+# define __GLIBC_HAVE_KERNEL_RSEQ
+# endif
+#endif
+
+#ifdef __cplusplus
+# if __cplusplus >= 201103L
+# define __rseq_static_assert(expr, diagnostic) static_assert (expr, diagnostic)
+# define __rseq_alignof(type) alignof (type)
+# define __rseq_alignas(x) alignas (x)
+# define __rseq_tls_storage_class thread_local
+# endif
+#elif (defined __STDC_VERSION__ ? __STDC_VERSION__ : 0) >= 201112L
+# define __rseq_static_assert(expr, diagnostic) _Static_assert (expr, diagnostic)
+# define __rseq_alignof(type) _Alignof (type)
+# define __rseq_alignas(x) _Alignas (x)
+# define __rseq_tls_storage_class _Thread_local
+#endif
+
+#ifndef __rseq_static_assert
+/* Try to use _Static_assert macro from sys/cdefs.h. */
+# ifdef _Static_assert
+# define __rseq_static_assert(expr, diagnostic) _Static_assert (expr, diagnostic)
+# else
+# define __rseq_static_assert(expr, diagnostic) /* Nothing. */
+# endif
+#endif
+
+/* Rely on GNU extensions for older standards and tls model. */
+#ifdef __GNUC__
+# ifndef __rseq_alignof
+# define __rseq_alignof(x) __alignof__ (x)
+# endif
+# ifndef __rseq_alignas
+# define __rseq_alignas(x) __attribute__ ((aligned (x)))
+# endif
+# define __rseq_tls_model_ie __attribute__ ((__tls_model__ ("initial-exec")))
+#else
+/* Specifying the TLS model on the declaration is optional. */
+# define __rseq_tls_model_ie /* Nothing. */
+#endif
+
+/* Fall back to __thread for TLS storage class. */
+#ifndef __rseq_tls_storage_class
+# define __rseq_tls_storage_class __thread
+#endif
+
+#ifdef __GLIBC_HAVE_KERNEL_RSEQ
+/* We use the structures declarations from the kernel headers. */
+# include <linux/rseq.h>
+#else /* __GLIBC_HAVE_KERNEL_RSEQ */
+/* We use a copy of the include/uapi/linux/rseq.h kernel header. */
+
+# include <asm/byteorder.h>
+
+enum rseq_cpu_id_state
+ {
+ RSEQ_CPU_ID_UNINITIALIZED = -1,
+ RSEQ_CPU_ID_REGISTRATION_FAILED = -2,
+ };
+
+enum rseq_flags
+ {
+ RSEQ_FLAG_UNREGISTER = (1 << 0),
+ };
+
+enum rseq_cs_flags_bit
+ {
+ RSEQ_CS_FLAG_NO_RESTART_ON_PREEMPT_BIT = 0,
+ RSEQ_CS_FLAG_NO_RESTART_ON_SIGNAL_BIT = 1,
+ RSEQ_CS_FLAG_NO_RESTART_ON_MIGRATE_BIT = 2,
+ };
+
+enum rseq_cs_flags
+ {
+ RSEQ_CS_FLAG_NO_RESTART_ON_PREEMPT =
+ (1U << RSEQ_CS_FLAG_NO_RESTART_ON_PREEMPT_BIT),
+ RSEQ_CS_FLAG_NO_RESTART_ON_SIGNAL =
+ (1U << RSEQ_CS_FLAG_NO_RESTART_ON_SIGNAL_BIT),
+ RSEQ_CS_FLAG_NO_RESTART_ON_MIGRATE =
+ (1U << RSEQ_CS_FLAG_NO_RESTART_ON_MIGRATE_BIT),
+ };
+
+/* struct rseq_cs is aligned on 32 bytes to ensure it is always
+ contained within a single cache-line. It is usually declared as
+ link-time constant data. */
+struct rseq_cs
+ {
+ /* Version of this structure. */
+ uint32_t __rseq_alignas (32) version;
+ /* enum rseq_cs_flags. */
+ uint32_t flags;
+ uint64_t start_ip;
+ /* Offset from start_ip. */
+ uint64_t post_commit_offset;
+ uint64_t abort_ip;
+ };
+
+/* struct rseq is aligned on 32 bytes to ensure it is always
+ contained within a single cache-line.
+
+ A single struct rseq per thread is allowed. */
+struct rseq
+ {
+ /* Restartable sequences cpu_id_start field. Updated by the
+ kernel. Read by user-space with single-copy atomicity
+ semantics. This field should only be read by the thread which
+ registered this data structure. Aligned on 32-bit. Always
+ contains a value in the range of possible CPUs, although the
+ value may not be the actual current CPU (e.g. if rseq is not
+ initialized). This CPU number value should always be compared
+ against the value of the cpu_id field before performing a rseq
+ commit or returning a value read from a data structure indexed
+ using the cpu_id_start value. */
+ uint32_t __rseq_alignas (32) cpu_id_start;
+ /* Restartable sequences cpu_id field. Updated by the kernel.
+ Read by user-space with single-copy atomicity semantics. This
+ field should only be read by the thread which registered this
+ data structure. Aligned on 32-bit. Values
+ RSEQ_CPU_ID_UNINITIALIZED and RSEQ_CPU_ID_REGISTRATION_FAILED
+ have a special semantic: the former means "rseq uninitialized",
+ and latter means "rseq initialization failed". This value is
+ meant to be read within rseq critical sections and compared
+ with the cpu_id_start value previously read, before performing
+ the commit instruction, or read and compared with the
+ cpu_id_start value before returning a value loaded from a data
+ structure indexed using the cpu_id_start value. */
+ uint32_t cpu_id;
+ /* Restartable sequences rseq_cs field.
+
+ Contains NULL when no critical section is active for the current
+ thread, or holds a pointer to the currently active struct rseq_cs.
+
+ Updated by user-space, which sets the address of the currently
+ active rseq_cs at the beginning of assembly instruction sequence
+ block, and set to NULL by the kernel when it restarts an assembly
+ instruction sequence block, as well as when the kernel detects that
+ it is preempting or delivering a signal outside of the range
+ targeted by the rseq_cs. Also needs to be set to NULL by user-space
+ before reclaiming memory that contains the targeted struct rseq_cs.
+
+ Read and set by the kernel. Set by user-space with single-copy
+ atomicity semantics. This field should only be updated by the
+ thread which registered this data structure. Aligned on 64-bit. */
+ union
+ {
+ uint64_t ptr64;
+# ifdef __LP64__
+ uint64_t ptr;
+# else /* __LP64__ */
+ struct
+ {
+# if (defined (__BYTE_ORDER) && (__BYTE_ORDER == __BIG_ENDIAN)) || defined (__BIG_ENDIAN)
+ uint32_t padding; /* Initialized to zero. */
+ uint32_t ptr32;
+# else /* LITTLE */
+ uint32_t ptr32;
+ uint32_t padding; /* Initialized to zero. */
+# endif /* ENDIAN */
+ } ptr;
+# endif /* __LP64__ */
+ } rseq_cs;
+
+ /* Restartable sequences flags field.
+
+ This field should only be updated by the thread which
+ registered this data structure. Read by the kernel.
+ Mainly used for single-stepping through rseq critical sections
+ with debuggers.
+
+ - RSEQ_CS_FLAG_NO_RESTART_ON_PREEMPT
+ Inhibit instruction sequence block restart on preemption
+ for this thread.
+ - RSEQ_CS_FLAG_NO_RESTART_ON_SIGNAL
+ Inhibit instruction sequence block restart on signal
+ delivery for this thread.
+ - RSEQ_CS_FLAG_NO_RESTART_ON_MIGRATE
+ Inhibit instruction sequence block restart on migration for
+ this thread. */
+ uint32_t flags;
+ };
+
+#endif /* __GLIBC_HAVE_KERNEL_RSEQ */
+
+/* Ensure the compiler supports rseq_align. */
+__rseq_static_assert (__rseq_alignof (struct rseq_cs) >= 32, "alignment");
+__rseq_static_assert (__rseq_alignof (struct rseq) >= 32, "alignment");
+
+/* Allocations of struct rseq and struct rseq_cs on the heap need to
+ be aligned on 32 bytes. Therefore, use of malloc is discouraged
+ because it does not guarantee alignment. posix_memalign should be
+ used instead. */
+
+extern __rseq_tls_storage_class struct rseq __rseq_abi __rseq_tls_model_ie;
+
+#endif /* sys/rseq.h */
diff --git a/sysdeps/unix/sysv/linux/x86/bits/rseq.h b/sysdeps/unix/sysv/linux/x86/bits/rseq.h
new file mode 100644
index 0000000000..f801d5d0a1
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/x86/bits/rseq.h
@@ -0,0 +1,30 @@
+/* Restartable Sequences Linux x86 architecture header.
+ Copyright (C) 2020 Free Software Foundation, Inc.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <https://www.gnu.org/licenses/>. */
+
+#ifndef _SYS_RSEQ_H
+# error "Never use <bits/rseq.h> directly; include <sys/rseq.h> instead."
+#endif
+
+/* RSEQ_SIG is a signature required before each abort handler code.
+
+ RSEQ_SIG is used with the following reserved undefined instructions, which
+ trap in user-space:
+
+ x86-32: 0f b9 3d 53 30 05 53 ud1 0x53053053,%edi
+ x86-64: 0f b9 3d 53 30 05 53 ud1 0x53053053(%rip),%edi */
+
+#define RSEQ_SIG 0x53053053
diff --git a/sysdeps/unix/sysv/linux/x86_64/64/libc.abilist b/sysdeps/unix/sysv/linux/x86_64/64/libc.abilist
index 03af18babb..f905d9c053 100644
--- a/sysdeps/unix/sysv/linux/x86_64/64/libc.abilist
+++ b/sysdeps/unix/sysv/linux/x86_64/64/libc.abilist
@@ -2065,6 +2065,7 @@ GLIBC_2.30 getdents64 F
GLIBC_2.30 gettid F
GLIBC_2.30 tgkill F
GLIBC_2.30 twalk_r F
+GLIBC_2.32 __rseq_abi T 0x20
GLIBC_2.32 pthread_attr_setaffinity_np F
GLIBC_2.32 pthread_getaffinity_np F
GLIBC_2.32 pthread_getattr_np F
diff --git a/sysdeps/unix/sysv/linux/x86_64/x32/libc.abilist b/sysdeps/unix/sysv/linux/x86_64/x32/libc.abilist
index 2da0af70d4..e43d704d7e 100644
--- a/sysdeps/unix/sysv/linux/x86_64/x32/libc.abilist
+++ b/sysdeps/unix/sysv/linux/x86_64/x32/libc.abilist
@@ -2162,6 +2162,7 @@ GLIBC_2.30 getdents64 F
GLIBC_2.30 gettid F
GLIBC_2.30 tgkill F
GLIBC_2.30 twalk_r F
+GLIBC_2.32 __rseq_abi T 0x20
GLIBC_2.32 pthread_attr_setaffinity_np F
GLIBC_2.32 pthread_getaffinity_np F
GLIBC_2.32 pthread_getattr_np F
--
2.17.1
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