Implement the core of the world switch in C. Not everything is there
yet, and there is nothing to re-enter the world switch either.

But this already outlines the code structure well enough.
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>
Reviewed-by: NChristoffer Dall <christoffer.dall@linaro.org>

KVM so far relies on code patching, and is likely to use it more
in the future. The main issue is that our alternative system works
at the instruction level, while we'd like to have alternatives at
the function level.

In order to cope with this, add the "hyp_alternate_select" macro that
outputs a brief sequence of code that in turn can be patched, allowing
an alternative function to be selected.
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>

Contrary to the previous patch, the guest entry is fairly different
from its assembly counterpart, mostly because it is only concerned
with saving/restoring the GP registers, and nothing else.
Reviewed-by: NChristoffer Dall <christoffer.dall@linaro.org>
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>

Implement the debug save restore as a direct translation of
the assembly code version.
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>
Tested-by: NAlex Bennée <alex.bennee@linaro.org>
Reviewed-by: NAlex Bennée <alex.bennee@linaro.org>
Reviewed-by: NChristoffer Dall <christoffer.dall@linaro.org>

Implement the 32bit system register save/restore as a direct
translation of the assembly code version.
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>
Reviewed-by: NChristoffer Dall <christoffer.dall@linaro.org>

Implement the system register save/restore as a direct translation of
the assembly code version.
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>
Reviewed-by: NChristoffer Dall <christoffer.dall@linaro.org>

Implement the timer save restore as a direct translation of
the assembly code version.
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>

Implement the vgic-v3 save restore as a direct translation of
the assembly code version.
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>

Implement the vgic-v2 save restore (mostly) as a direct translation
of the assembly code version.
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>

In order to expose the various EL2 services that are private to
the hypervisor, add a new hyp.h file.

So far, it only contains mundane things such as section annotation
and VA manipulation.
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>