Improve __copy_to_user and __copy_from_user performance

Improve __copy_to_user and __copy_from_user performance

Provide a __copy_from_user that uses memcpy. On BCM2708, use
optimised memcpy/memmove/memcmp/memset implementations.

arch/arm: Add mmiocpy/set aliases for memcpy/set

See: https://github.com/raspberrypi/linux/issues/1082

copy_from_user: CPU_SW_DOMAIN_PAN compatibility

The downstream copy_from_user acceleration must also play nice with
CONFIG_CPU_SW_DOMAIN_PAN.

See: https://github.com/raspberrypi/linux/issues/1381

Signed-off-by: Phil Elwell <phil@raspberrypi.org>
Fix copy_from_user if BCM2835_FAST_MEMCPY=n

The change which introduced CONFIG_BCM2835_FAST_MEMCPY unconditionally
changed the behaviour of arm_copy_from_user. The page pinning code
is not safe on ARMv7 if LPAE & high memory is enabled and causes
crashes which look like PTE corruption.

Make __copy_from_user_memcpy conditional on CONFIG_2835_FAST_MEMCPY=y
which is really an ARMv6 / Pi1 optimization and not necessary on newer
ARM processors.

arm: fix mmap unlocks in uaccess_with_memcpy.c

This is a regression that was added with the commit 192a4e923ef092924dd013e7326f2ec520ee4783 as of rpi-5.8.y, since that is when the move to the mmap locking API was introduced - d8ed45c5dcd455fc5848d47f86883a1b872ac0d0

The issue is that when the patch to improve performance for the __copy_to_user and __copy_from_user functions were added for the Raspberry Pi, some of the mmaps were incorrectly mapped to write instead of read. This would cause a verity of issues, and in my case, prevent the booting of a squashfs filesystem on rpi-5.8-y and above. An example of the panic you would see from this can be seen at https://pastebin.com/raw/jBz5xCzL

Signed-off-by: Christian Lamparter <chunkeey@gmail.com>
Signed-off-by: Christopher Blake <chrisrblake93@gmail.com>
arch/arm: Add __memset alias to memset_rpi.S

memset_rpi.S is an optimised memset implementation, but doesn't define
__memset (which was just added to memset.S). As a result, building
for the BCM2835 platform causes a link failure.

Add __memset as yet another alias to our common implementation.

Signed-off-by: Phil Elwell <phil@raspberrypi.com>
arm: Fix custom rpi __memset32 and __memset64

See: https://github.com/raspberrypi/linux/issues/4798

Signed-off-by: Phil Elwell <phil@raspberrypi.com>
arm: Fix annoying .eh_frame section warnings

Replace the cfi directives with the UNWIND equivalents. This prevents
the .eh_frame section from being created, eliminating the warnings.

Signed-off-by: Phil Elwell <phil@raspberrypi.com>