Enable support for EL3 interrupt in IMF ...

This patch enables support for EL3 interrupts in the Interrupt Management
Framework (IMF) of ARM Trusted Firmware. Please note that although the
registration of the EL3 interrupt type is now supported, it has not been
tested on any of the ARM Standard platforms.

Change-Id: If4dcdc7584621522a2f3ea13ea9b1ad0a76bb8a1

IMF: postpone SCR_EL3 update if context is not initialized ...

The set_routing_model() function in the Interrupt Management
Framework calls the context management library to update the
SCR_EL3 register. This context management library assumes that
the context has been previously initialized. Consequently, if
a Secure Payload Dispatcher (SPD) tries to set the routing model
before initializing the context, the system will fail (in debug
mode, an assertion will be raised).

This patch fixes the issue by checking if the context has been
initialized before updating SCR_EL3. If a valid context is not
available, SCR_EL3 update will be done when the SPD calls the
context initialization function. This function will call
get_scr_el3_from_routing_model() to obtain the SCR_EL3 value.
If the SPD does not call the context initialization function
then it is SPD's responsibility to obtain SCR_EL3 from the IMF
and update the context accordingly.

Fixes ARM-software/tf-issues#327

Change-Id: Ic2f1c6e899e578a8db858ec43747c63a8539c16f

Demonstrate model for routing IRQs to EL3 ...

This patch provides an option to specify a interrupt routing model
where non-secure interrupts (IRQs) are routed to EL3 instead of S-EL1.
When such an interrupt occurs, the TSPD arranges a return to
the normal world after saving any necessary context. The interrupt
routing model to route IRQs to EL3 is enabled only during STD SMC
processing. Thus the pre-emption of S-EL1 is disabled during Fast SMC
and Secure Interrupt processing.

A new build option TSPD_ROUTE_NS_INT_EL3 is introduced to change
the non secure interrupt target execution level to EL3.

Fixes ARM-software/tf-issues#225

Change-Id: Ia1e779fbbb6d627091e665c73fa6315637cfdd32

Rework incorrect use of assert() and panic() in codebase ...

Assert a valid security state using the macro sec_state_is_valid().
Replace assert() with panic() in those cases that might arise
because of runtime errors and not programming errors.
Replace panic() with assert() in those cases that might arise
because of programming errors.

Fixes ARM-software/tf-issues#96

Change-Id: I51e9ef0439fd5ff5e0edfef49050b69804bf14d5

Introduce interrupt registration framework in BL3-1 ...

This patch introduces a framework for registering interrupts routed to
EL3. The interrupt routing model is governed by the SCR_EL3.IRQ and
FIQ bits and the security state an interrupt is generated in. The
framework recognizes three type of interrupts depending upon which
exception level and security state they should be handled in
i.e. Secure EL1 interrupts, Non-secure interrupts and EL3
interrupts. It provides an API and macros that allow a runtime service
to register an handler for a type of interrupt and specify the routing
model. The framework validates the routing model and uses the context
management framework to ensure that it is applied to the SCR_EL3 prior
to entry into the target security state. It saves the handler in
internal data structures. An API is provided to retrieve the handler
when an interrupt of a particular type is asserted. Registration is
expected to be done once by the primary CPU. The same handler and
routing model is used for all CPUs.

Support for EL3 interrupts will be added to the framework in the
future. A makefile flag has been added to allow the FVP port choose
between ARM GIC v2 and v3 support in EL3. The latter version is
currently unsupported.

A framework for handling interrupts in BL3-1 will be introduced in
subsequent patches. The default routing model in the absence of any
handlers expects no interrupts to be routed to EL3.

Change-Id: Idf7c023b34fcd4800a5980f2bef85e4b5c29e649