y2038: hide timeval/timespec/itimerval/itimerspec types

There are no in-kernel users remaining, but there may still be users that
include linux/time.h instead of sys/time.h from user space, so leave the
types available to user space while hiding them from kernel space.

Only the __kernel_old_* versions of these types remain now.

Link: http://lkml.kernel.org/r/20200110154232.4104492-4-arnd@arndb.de
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Deepa Dinamani <deepa.kernel@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

y2038: add __kernel_old_timespec and __kernel_old_time_t

The 'struct timespec' definition can no longer be part of the uapi headers
because it conflicts with a a now incompatible libc definition. Also,
we really want to remove it in order to prevent new uses from creeping in.

The same namespace conflict exists with time_t, which should also be
removed. __kernel_time_t could be used safely, but adding 'old' in the
name makes it clearer that this should not be used for new interfaces.

Add a replacement __kernel_old_timespec structure and __kernel_old_time_t
along the lines of __kernel_old_timeval.

Acked-by: Deepa Dinamani <deepa.kernel@gmail.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

time: Add new y2038 safe __kernel_timespec

The new struct __kernel_timespec is similar to current
internal kernel struct timespec64 on 64 bit architecture.
The compat structure however is similar to below on little
endian systems (padding and tv_nsec are switched for big
endian systems):

typedef s32 compat_long_t;
typedef s64 compat_kernel_time64_t;

struct compat_kernel_timespec {
compat_kernel_time64_t tv_sec;
compat_long_t tv_nsec;
compat_long_t padding;
};

This allows for both the native and compat representations to
be the same and syscalls using this type as part of their ABI
can have a single entry point to both.

Note that the compat define is not included anywhere in the
kernel explicitly to avoid confusion.

These types will be used by the new syscalls that will be
introduced in the consequent patches.
Most of the new syscalls are just an update to the existing
native ones with this new type. Hence, put this new type under
an ifdef so that the architectures can define CONFIG_64BIT_TIME
when they are ready to handle this switch.

Cc: linux-arch@vger.kernel.org
Signed-off-by: Deepa Dinamani <deepa.kernel@gmail.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

License cleanup: add SPDX license identifier to uapi header files with no license

Many user space API headers are missing licensing information, which
makes it hard for compliance tools to determine the correct license.

By default are files without license information under the default
license of the kernel, which is GPLV2. Marking them GPLV2 would exclude
them from being included in non GPLV2 code, which is obviously not
intended. The user space API headers fall under the syscall exception
which is in the kernels COPYING file:

NOTE! This copyright does *not* cover user programs that use kernel
services by normal system calls - this is merely considered normal use
of the kernel, and does *not* fall under the heading of "derived work".

otherwise syscall usage would not be possible.

Update the files which contain no license information with an SPDX
license identifier. The chosen identifier is 'GPL-2.0 WITH
Linux-syscall-note' which is the officially assigned identifier for the
Linux syscall exception. SPDX license identifiers are a legally binding
shorthand, which can be used instead of the full boiler plate text.

This patch is based on work done by Thomas Gleixner and Kate Stewart and
Philippe Ombredanne. See the previous patch in this series for the
methodology of how this patch was researched.

Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org>
Reviewed-by: Philippe Ombredanne <pombredanne@nexb.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

UAPI: (Scripted) Disintegrate include/asm-generic

Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Michael Kerrisk <mtk.manpages@gmail.com>
Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Dave Jones <davej@redhat.com>