openrisc: Add clone3 ABI wrapper

Like fork and clone the clone3 syscall needs a wrapper to save callee
saved registers, which is required by the OpenRISC ABI. This came up
after auditing code following a discussion with Rob Landley and Arnd
Bergmann [0].

Tested with the clone3 kselftests and there were no issues.

[0] https://lore.kernel.org/all/41206fc7-f8ce-98aa-3718-ba3e1431e320@landley.net/T/#m9c0cdb2703813b9df4da04cf6b30de1f1aa89944

Fixes: 07e83dfbe16c ("openrisc: Enable the clone3 syscall")
Cc: Rob Landley <rob@landley.net>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Stafford Horne <shorne@gmail.com>

treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152

Based on 1 normalized pattern(s):

this program is free software you can redistribute it and or modify
it under the terms of the gnu general public license as published by
the free software foundation either version 2 of the license or at
your option any later version

extracted by the scancode license scanner the SPDX license identifier

GPL-2.0-or-later

has been chosen to replace the boilerplate/reference in 3029 file(s).

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Allison Randal <allison@lohutok.net>
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190527070032.746973796@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

openrisc: switch to use of generic fork and clone

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

OpenRISC: System calls

The OpenRISC Linux kernel conforms to the "generic" syscall interface which
contains only the reduced set of syscalls deemed necessary for new
architectures. Unfortunately, the uClibc port for OpenRISC does not fully
support this reduced set; as such, an additional patch available out-of-tree
needs to be applied to the kernel in order to use the current uClibc. This
is just a temporary measure until the libc port can be straightened out; it
is likely that OpenRISC will make the transition to glibc shortly where the
generic syscall interface is better supported.

Signed-off-by: Jonas Bonn <jonas@southpole.se>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>