PSCI: Decouple PSCI stat residency calculation from PMF

This patch introduces the following three platform interfaces:

* void plat_psci_stat_accounting_start(const psci_power_state_t *state_info)

PSCI: Decouple PSCI stat residency calculation from PMF

This patch introduces the following three platform interfaces:

* void plat_psci_stat_accounting_start(const psci_power_state_t *state_info)

This is an optional hook that platforms can implement in order
to perform accounting before entering a low power state. This
typically involves capturing a timestamp.

* void plat_psci_stat_accounting_stop(const psci_power_state_t *state_info)

This is an optional hook that platforms can implement in order
to perform accounting after exiting from a low power state. This
typically involves capturing a timestamp.

* u_register_t plat_psci_stat_get_residency(unsigned int lvl,
const psci_power_state_t *state_info,
unsigned int last_cpu_index)

This is an optional hook that platforms can implement in order
to calculate the PSCI stat residency.

If any of these interfaces are overridden by the platform, it is
recommended that all of them are.

By default `ENABLE_PSCI_STAT` is disabled. If `ENABLE_PSCI_STAT`
is set but `ENABLE_PMF` is not set then an alternative PSCI stat
collection backend must be provided. If both are set, then default
weak definitions of these functions are provided, using PMF to
calculate the residency.

NOTE: Previously, platforms did not have to explicitly set
`ENABLE_PMF` since this was automatically done by the top-level
Makefile.

Change-Id: I17b47804dea68c77bc284df15ee1ccd66bc4b79b
Signed-off-by: dp-arm <dimitris.papastamos@arm.com>

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Merge pull request #669 from sandrine-bailleux-arm/sb/tf-hardening

Minor improvements to harden TF code

Validate psci_find_target_suspend_lvl() result

This patch adds a runtime check that psci_find_target_suspend_lvl()
returns a valid value back to psci_cpu_suspend() and psci_get_stat().
If it is inva

Validate psci_find_target_suspend_lvl() result

This patch adds a runtime check that psci_find_target_suspend_lvl()
returns a valid value back to psci_cpu_suspend() and psci_get_stat().
If it is invalid, BL31 will now panic.

Note that on the PSCI CPU suspend path there is already a debug
assertion checking the validity of the target composite power state,
which effectively also checks the validity of the target suspend level.
Therefore, the error condition would already be caught in debug builds,
but in a release build this assertion would be compiled out.

On the PSCI stat path, there is currently no debug assertion checking
the validity of the power state before using it as an index into
the power domain state array.

Although BL31 platforms ports are responsible for validating the
power state parameter, the security impact (i.e. an out-of-bounds
array access) of a potential platform port bug in this code would
be quite high, given that this parameter comes from an untrusted
source. The cost of checking this in runtime generic code is low.

Change-Id: Icea85b8020e39928ac03ec0cd49805b5857b3906

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Merge pull request #667 from soby-mathew/sm/PSCI_lib

Introduce PSCI library

Introduce `el3_runtime` and `PSCI` libraries

This patch moves the PSCI services and BL31 frameworks like context
management and per-cpu data into new library components `PSCI` and
`el3_runtime` resp

Introduce `el3_runtime` and `PSCI` libraries

This patch moves the PSCI services and BL31 frameworks like context
management and per-cpu data into new library components `PSCI` and
`el3_runtime` respectively. This enables PSCI to be built independently from
BL31. A new `psci_lib.mk` makefile is introduced which adds the relevant
PSCI library sources and gets included by `bl31.mk`. Other changes which
are done as part of this patch are:

* The runtime services framework is now moved to the `common/` folder to
enable reuse.
* The `asm_macros.S` and `assert_macros.S` helpers are moved to architecture
specific folder.
* The `plat_psci_common.c` is moved from the `plat/common/aarch64/` folder
to `plat/common` folder. The original file location now has a stub which
just includes the file from new location to maintain platform compatibility.

Most of the changes wouldn't affect platform builds as they just involve
changes to the generic bl1.mk and bl31.mk makefiles.

NOTE: THE `plat_psci_common.c` FILE HAS MOVED LOCATION AND THE STUB FILE AT
THE ORIGINAL LOCATION IS NOW DEPRECATED. PLATFORMS SHOULD MODIFY THEIR
MAKEFILES TO INCLUDE THE FILE FROM THE NEW LOCATION.

Change-Id: I6bd87d5b59424995c6a65ef8076d4fda91ad5e86

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