GitLab

This patch adds an argument to bl1_plat_post/pre_image_load() APIs
to make it more future proof. The default implementation of
these are moved to `plat_bl1_common.c` file.

These APIs are now invoked appropriately in the FWU code path prior
to or post image loading by BL1 and are not restricted
to LOAD_IMAGE_V2.

The patch also reorganizes some common platform files. The previous
`plat_bl2_el3_common.c` and `platform_helpers_default.c` files are
merged into a new `plat_bl_common.c` file.

NOTE: The addition of an argument to the above mentioned platform APIs
is not expected to have a great impact because these APIs were only
recently added and are unlikely to be used.

Change-Id: I0519caaee0f774dd33638ff63a2e597ea178c453
Signed-off-by: Soby Mathew <soby.mathew@arm.com>

After executing a TLBI a DSB is needed to ensure completion of the
TLBI.

rk3328: The MMU is allowed to load TLB entries for as long as it is
enabled. Because of this, the correct place to execute a TLBI is right
after disabling the MMU.

Change-Id: I8280f248d10b49a8c354a4ccbdc8f8345ac4c170
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>

Add 'lr_svc' as a boot parameter in AArch32 bl1. This is used by Optee
and Trusty to get the non-secure entry point on AArch32 platforms.

This change is not ported in AArch64 mode where the BL31, not BL32,
is in charge of booting the non secure image (BL33).
Signed-off-by: Etienne Carriere <etienne.carriere@linaro.org>

Just like bl2_, add pre/post image load handlers for BL1.  No argument
is needed since BL2 is the only image loaded by BL1.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

This patch modifies the makefiles to avoid the definition
of BL1_SOURCES and BL2_SOURCES in the tbbr makefiles, and
it lets to the platform makefiles to define them if they
actually need these images. In the case of BL2_AT_EL3
BL1 will not be needed usually because the Boot ROM will
jump directly to BL2.

Change-Id: Ib6845a260633a22a646088629bcd7387fe35dcf9
Signed-off-by: Roberto Vargas <roberto.vargas@arm.com>

When defining different sections in linker scripts it is needed to align
them to multiples of the page size. In most linker scripts this is done
by aligning to the hardcoded value 4096 instead of PAGE_SIZE.

This may be confusing when taking a look at all the codebase, as 4096
is used in some parts that aren't meant to be a multiple of the page
size.

Change-Id: I36c6f461c7782437a58d13d37ec8b822a1663ec1
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>

This fix modifies the order of system includes to meet the ARM TF coding
standard. There are some exceptions in order to retain header groupings,
minimise changes to imported headers, and where there are headers within
the #if and #ifndef statements.

Change-Id: I65085a142ba6a83792b26efb47df1329153f1624
Signed-off-by: Isla Mitchell <isla.mitchell@arm.com>

This change avoids warnings when setting -Wmissing-prototypes or when
using sparse tool.
Signed-off-by: Yann Gautier <yann.gautier@st.com>
Signed-off-by: Etienne Carriere <etienne.carriere@st.com>

This change avoids warning when setting -Wmissing-prototypes to
compile bl1_context_mgmt.c.
Reported-by: Yann Gautier <yann.gautier@st.com>
Signed-off-by: Etienne Carriere <etienne.carriere@st.com>

security_state is either 0 or 1. Prevent sign conversion potential
error (setting -Werror=sign-conversion results in a build error).
Signed-off-by: Yann Gautier <yann.gautier@st.com>
Signed-off-by: Etienne Carriere <etienne.carriere@st.com>

This patch updates the el3_arch_init_common macro so that it fully
initialises essential control registers rather then relying on hardware
to set the reset values.

The context management functions are also updated to fully initialise
the appropriate control registers when initialising the non-secure and
secure context structures and when preparing to leave EL3 for a lower
EL.

This gives better alignement with the ARM ARM which states that software
must initialise RES0 and RES1 fields with 0 / 1.

This patch also corrects the following typos:

"NASCR definitions" -> "NSACR definitions"

Change-Id: Ia8940b8351dc27bc09e2138b011e249655041cfc
Signed-off-by: David Cunado <david.cunado@arm.com>

This patch fixes the following issues in Firmware Update (FWU) code:

1. The FWU layer maintains a list of loaded image ids and
   while checking for image overlaps, INVALID_IMAGE_IDs were not
   skipped. The patch now adds code to skip INVALID_IMAGE_IDs.

2. While resetting the state corresponding to an image, the code
   now resets the memory used by the image only if the image were
   copied previously via IMAGE_COPY smc. This prevents the invalid
   zeroing of image memory which are not copied but are directly
   authenticated via IMAGE_AUTH smc.

Change-Id: Idf18e69bcba7259411c88807bd0347d59d9afb8f
Signed-off-by: Soby Mathew <soby.mathew@arm.com>

This SMC is as a means for the image loading state machine to go from
COPYING, COPIED or AUTHENTICATED states to RESET state. Previously, this
was only done when the authentication of an image failed or when the
execution of the image finished.

Documentation updated.

Change-Id: Ida6d4c65017f83ae5e27465ec36f54499c6534d9
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>

Added checks to FWU_SMC_IMAGE_COPY to prevent loading data into a
memory region where another image data is already loaded.

Without this check, if two images are configured to be loaded in
overlapping memory regions, one of them can be loaded and
authenticated and the copy function is still able to load data from
the second image on top of the first one. Since the first image is
still in authenticated state, it can be executed, which could lead to
the execution of unauthenticated arbitrary code of the second image.

Firmware update documentation updated.

Change-Id: Ib6871e569794c8e610a5ea59fe162ff5dcec526c
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>

This patch adds `TRUSTED_BOARD_BOOT` support for AArch32 mode.

To build this patch the "mbedtls/include/mbedtls/bignum.h"
needs to be modified to remove `#define MBEDTLS_HAVE_UDBL`
when `MBEDTLS_HAVE_INT32` is defined. This is a workaround
for "https://github.com/ARMmbed/mbedtls/issues/708

"

NOTE: TBBR support on Juno AArch32 is not currently supported.

Change-Id: I86d80e30b9139adc4d9663f112801ece42deafcf
Signed-off-by: dp-arm <dimitris.papastamos@arm.com>
Co-Authored-By: Yatharth Kochar <yatharth.kochar@arm.com>

The current SMC context data structure `smc_ctx_t` and related helpers are
optimized for case when SMC call does not result in world switch. This was
the case for SP_MIN and BL1 cold boot flow. But the firmware update usecase
requires world switch as a result of SMC and the current SMC context helpers
were not helping very much in this regard. Therefore this patch does the
following changes to improve this:

1. Add monitor stack pointer, `spmon` to `smc_ctx_t`

The C Runtime stack pointer in monitor mode, `sp_mon` is added to the
SMC context, and the `smc_ctx_t` pointer is cached in `sp_mon` prior
to exit from Monitor mode. This makes is easier to retrieve the
context when the next SMC call happens. As a result of this change,
the SMC context helpers no longer depend on the stack to save and
restore the register.

This aligns it with the context save and restore mechanism in AArch64.

2. Add SCR in `smc_ctx_t`

Adding the SCR register to `smc_ctx_t` makes it easier to manage this
register state when switching between non secure and secure world as a
result of an SMC call.

Change-Id: I5e12a7056107c1701b457b8f7363fdbf892230bf
Signed-off-by: Soby Mathew <soby.mathew@arm.com>
Signed-off-by: dp-arm <dimitris.papastamos@arm.com>

To make software license auditing simpler, use SPDX[0] license
identifiers instead of duplicating the license text in every file.

NOTE: Files that have been imported by FreeBSD have not been modified.

[0]: https://spdx.org/



Change-Id: I80a00e1f641b8cc075ca5a95b10607ed9ed8761a
Signed-off-by: dp-arm <dimitris.papastamos@arm.com>

Replace all instances of checks with the new macro.

Change-Id: I0eec39b9376475a1a9707a3115de9d36f88f8a2a
Signed-off-by: Jeenu Viswambharan <jeenu.viswambharan@arm.com>

Many asserts depend on code that is conditionally compiled based on the
DEBUG define. This patch modifies the conditional inclusion of such code
so that it is based on the ENABLE_ASSERTIONS build option.

Change-Id: I6406674788aa7e1ad7c23d86ce94482ad3c382bd
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>

SMC_RET0 should only be used when the SMC code works as a function that
returns void. If the code of the SMC uses SMC_RET1 to return a value to
signify success and doesn't return anything in case of an error (or the
other way around) SMC_RET1 should always be used to return clearly
identifiable values.

This patch fixes two cases in which the code used SMC_RET0 instead of
SMC_RET1.

It also introduces the define SMC_OK to use when an SMC must return a
value to tell that it succeeded, the same way as SMC_UNK is used in case
of failure.

Change-Id: Ie4278b51559e4262aced13bbde4e844023270582
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>

Introduce new build option ENABLE_STACK_PROTECTOR. It enables
compilation of all BL images with one of the GCC -fstack-protector-*
options.

A new platform function plat_get_stack_protector_canary() is introduced.
It returns a value that is used to initialize the canary for stack
corruption detection. Returning a random value will prevent an attacker
from predicting the value and greatly increase the effectiveness of the
protection.

A message is printed at the ERROR level when a stack corruption is
detected.

To be effective, the global data must be stored at an address
lower than the base of the stacks. Failure to do so would allow an
attacker to overwrite the canary as part of an attack which would void
the protection.

FVP implementation of plat_get_stack_protector_canary is weak as
there is no real source of entropy on the FVP. It therefore relies on a
timer's value, which could be predictable.

Change-Id: Icaaee96392733b721fa7c86a81d03660d3c1bc06
Signed-off-by: Douglas Raillard <douglas.raillard@arm.com>

Call console_flush() before execution either terminates or leaves an
exception level.

Fixes: ARM-software/tf-issues#123

Change-Id: I64eeb92effb039f76937ce89f877b68e355588e3
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>

These source file definitions should be defined in generic
Makefiles so that all platforms can benefit. Ensure that the
symbols are properly marked as weak so they can be overridden
by platforms.

NOTE: This change is a potential compatibility break for
non-upstream platforms.

Change-Id: I7b892efa9f2d6d216931360dc6c436e1d10cffed
Signed-off-by: dp-arm <dimitris.papastamos@arm.com>

Introduce zeromem_dczva function on AArch64 that can handle unaligned
addresses and make use of DC ZVA instruction to zero a whole block at a
time. This zeroing takes place directly in the cache to speed it up
without doing external memory access.

Remove the zeromem16 function on AArch64 and replace it with an alias to
zeromem. This zeromem16 function is now deprecated.

Remove the 16-bytes alignment constraint on __BSS_START__ in
firmware-design.md as it is now not mandatory anymore (it used to comply
with zeromem16 requirements).

Change the 16-bytes alignment constraints in SP min's linker script to a
8-bytes alignment constraint as the AArch32 zeromem implementation is now
more efficient on 8-bytes aligned addresses.

Introduce zero_normalmem and zeromem helpers in platform agnostic header
that are implemented this way:
* AArch32:
	* zero_normalmem: zero using usual data access
	* zeromem: alias for zero_normalmem
* AArch64:
	* zero_normalmem: zero normal memory  using DC ZVA instruction
	                  (needs MMU enabled)
	* zeromem: zero using usual data access

Usage guidelines: in most cases, zero_normalmem should be preferred.

There are 2 scenarios where zeromem (or memset) must be used instead:
* Code that must run with MMU disabled (which means all memory is
  considered device memory for data accesses).
* Code that fills device memory with null bytes.

Optionally, the following rule can be applied if performance is
important:
* Code zeroing small areas (few bytes) that are not secrets should use
  memset to take advantage of compiler optimizations.

  Note: Code zeroing security-related critical information should use
  zero_normalmem/zeromem instead of memset to avoid removal by
  compilers' optimizations in some cases or misbehaving versions of GCC.

Fixes ARM-software/tf-issues#408

Change-Id: Iafd9663fc1070413c3e1904e54091cf60effaa82
Signed-off-by: Douglas Raillard <douglas.raillard@arm.com>

The errata reporting policy is as follows:

  - If an errata workaround is enabled:

    - If it applies (i.e. the CPU is affected by the errata), an INFO
      message is printed, confirming that the errata workaround has been
      applied.

    - If it does not apply, a VERBOSE message is printed, confirming
      that the errata workaround has been skipped.

  - If an errata workaround is not enabled, but would have applied had
    it been, a WARN message is printed, alerting that errata workaround
    is missing.

The CPU errata messages are printed by both BL1 (primary CPU only) and
runtime firmware on debug builds, once for each CPU/errata combination.

Relevant output from Juno r1 console when ARM Trusted Firmware is built
with PLAT=juno LOG_LEVEL=50 DEBUG=1:

  VERBOSE: BL1: cortex_a57: errata workaround for 806969 was not applied
  VERBOSE: BL1: cortex_a57: errata workaround for 813420 was not applied
  INFO:    BL1: cortex_a57: errata workaround for disable_ldnp_overread was applied
  WARNING: BL1: cortex_a57: errata workaround for 826974 was missing!
  WARNING: BL1: cortex_a57: errata workaround for 826977 was missing!
  WARNING: BL1: cortex_a57: errata workaround for 828024 was missing!
  WARNING: BL1: cortex_a57: errata workaround for 829520 was missing!
  WARNING: BL1: cortex_a57: errata workaround for 833471 was missing!
  ...
  VERBOSE: BL31: cortex_a57: errata workaround for 806969 was not applied
  VERBOSE: BL31: cortex_a57: errata workaround for 813420 was not applied
  INFO:    BL31: cortex_a57: errata workaround for disable_ldnp_overread was applied
  WARNING: BL31: cortex_a57: errata workaround for 826974 was missing!
  WARNING: BL31: cortex_a57: errata workaround for 826977 was missing!
  WARNING: BL31: cortex_a57: errata workaround for 828024 was missing!
  WARNING: BL31: cortex_a57: errata workaround for 829520 was missing!
  WARNING: BL31: cortex_a57: errata workaround for 833471 was missing!
  ...
  VERBOSE: BL31: cortex_a53: errata workaround for 826319 was not applied
  INFO:    BL31: cortex_a53: errata workaround for disable_non_temporal_hint was applied

Also update documentation.

Change-Id: Iccf059d3348adb876ca121cdf5207bdbbacf2aba
Signed-off-by: Jeenu Viswambharan <jeenu.viswambharan@arm.com>

Before adding a base address and a size to compute the end
address of an image to copy or authenticate, check this
won't result in an integer overflow. If it does then consider
the input arguments are invalid.

As a result, bl1_plat_mem_check() can now safely assume the
end address (computed as the sum of the base address and size
of the memory region) doesn't overflow, as the validation is
done upfront in bl1_fwu_image_copy/auth(). A debug assertion
has been added nonetheless in the ARM implementation in order
to help catching such problems, should bl1_plat_mem_check()
be called in a different context in the future.

Fixes TFV-1: Malformed Firmware Update SMC can result in copy
of unexpectedly large data into secure memory

Change-Id: I8b8f8dd4c8777705722c7bd0e8b57addcba07e25
Signed-off-by: Sandrine Bailleux <sandrine.bailleux@arm.com>
Signed-off-by: Dan Handley <dan.handley@arm.com>

These debug assertions sanity check the state of the internal
FWU state machine data when resuming an incomplete image copy
operation.

Change-Id: I38a125b0073658c3e2b4b1bdc623ec221741f43e
Signed-off-by: Sandrine Bailleux <sandrine.bailleux@arm.com>

This patch refactors the code of the function handling a FWU_AUTH_COPY
SMC in BL1. All input validation has been moved upfront so it is now
shared between the RESET and COPYING states.

Change-Id: I6a86576b9ce3243c401c2474fe06f06687a70e2f
Signed-off-by: Sandrine Bailleux <sandrine.bailleux@arm.com>
Signed-off-by: Dan Handley <dan.handley@arm.com>

This patch introduces no functional change, it just changes
the serial console output.

 - Improve accuracy of error messages by decoupling some
   error cases;

 - Improve comments;

 - Move declaration of 'mem_layout' local variable closer to
   where it is used and make it const;

 - Rename a local variable to clarify whether it is a source
   or a destination address (base_addr -> dest_addr).

Change-Id: I349fcf053e233f316310892211d49e35ef2c39d9
Signed-off-by: Sandrine Bailleux <sandrine.bailleux@arm.com>
Signed-off-by: Dan Handley <dan.handley@arm.com>

This patch enables TRUSTED_BOARD_BOOT (Authentication and FWU)
support, for AArch64, when LOAD_IMAGE_V2 is enabled.

This patch also enables LOAD_IMAGE_V2 for ARM platforms.

Change-Id: I294a2eebce7a30b6784c80c9d4ac7752808ee3ad
Signed-off-by: Yatharth Kochar <yatharth.kochar@arm.com>

There are many instances in ARM Trusted Firmware where control is
transferred to functions from which return isn't expected. Such jumps
are made using 'bl' instruction to provide the callee with the location
from which it was jumped to. Additionally, debuggers infer the caller by
examining where 'lr' register points to. If a 'bl' of the nature
described above falls at the end of an assembly function, 'lr' will be
left pointing to a location outside of the function range. This misleads
the debugger back trace.

This patch defines a 'no_ret' macro to be used when jumping to functions
from which return isn't expected. The macro ensures to use 'bl'
instruction for the jump, and also, for debug builds, places a 'nop'
instruction immediately thereafter (unless instructed otherwise) so as
to leave 'lr' pointing within the function range.

Change-Id: Ib34c69fc09197cfd57bc06e147cc8252910e01b0
Co-authored-by: Douglas Raillard <douglas.raillard@arm.com>
Signed-off-by: Jeenu Viswambharan <jeenu.viswambharan@arm.com>

The Virtualization field in the ID_PFR1 register has only 2
valid values (0 or 1) but it was incorrectly checked against
unrelated value tied to the SPSR register instead.

This patch fixes the detection of virtualization support by
using the valid values in BL1 context management code.

Change-Id: If12592e343770e1da90f0f5fecf0a3376047ac29

This patch adds generic changes in BL1 to support AArch32 state.
New AArch32 specific assembly/C files are introduced and
some files are moved to AArch32/64 specific folders.
BL1 for AArch64 is refactored but functionally identical.
BL1 executes in Secure Monitor mode in AArch32 state.

NOTE: BL1 in AArch32 state ONLY handles BL1_RUN_IMAGE SMC.

Change-Id: I6e2296374c7efbf3cf2aa1a0ce8de0732d8c98a5

This patch adds changes in BL1 & BL2 to use new version
of image loading to load the BL images.

Following are the changes in BL1:
  -Use new version of load_auth_image() to load BL2
  -Modified `bl1_init_bl2_mem_layout()` to remove using
   `reserve_mem()` and to calculate `bl2_mem_layout`.
   `bl2_mem_layout` calculation now assumes that BL1 RW
   data is at the top of the bl1_mem_layout, which is more
   restrictive than the previous BL1 behaviour.

Following are the changes in BL2:
  -The `bl2_main.c` is refactored and all the functions
   for loading BLxx images are now moved to `bl2_image_load.c`
   `bl2_main.c` now calls a top level `bl2_load_images()` to
   load all the images that are applicable in BL2.
  -Added new file `bl2_image_load_v2.c` that uses new version
   of image loading to load the BL images in BL2.

All the above changes are conditionally compiled using the
`LOAD_IMAGE_V2` flag.

Change-Id: Ic6dcde5a484495bdc05526d9121c59fa50c1bf23

This patch removes the tight loop that calls `plat_report_exception`
in unhandled exceptions in AArch64 state.
The new behaviour is to call the `plat_report_exception` only
once followed by call to `plat_panic_handler`.
This allows platforms to take platform-specific action when
there is an unhandled exception, instead of always spinning
in a tight loop.

Note: This is a subtle break in behaviour for platforms that
      expect `plat_report_exception` to be continuously executed
      when there is an unhandled exception.

Change-Id: Ie2453804b9b7caf9b010ee73e1a90eeb8384e4e8

This patch moves the macro SIZE_FROM_LOG2_WORDS() defined in
`arch.h` to `utils.h` as it is utility macro.

Change-Id: Ia8171a226978f053a1ee4037f80142c0a4d21430

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

At the moment, all BL images share a similar memory layout: they start
with their code section, followed by their read-only data section.
The two sections are contiguous in memory. Therefore, the end of the
code section and the beginning of the read-only data one might share
a memory page. This forces both to be mapped with the same memory
attributes. As the code needs to be executable, this means that the
read-only data stored on the same memory page as the code are
executable as well. This could potentially be exploited as part of
a security attack.

This patch introduces a new build flag called
SEPARATE_CODE_AND_RODATA, which isolates the code and read-only data
on separate memory pages. This in turn allows independent control of
the access permissions for the code and read-only data.

This has an impact on memory footprint, as padding bytes need to be
introduced between the code and read-only data to ensure the
segragation of the two. To limit the memory cost, the memory layout
of the read-only section has been changed in this case.

 - When SEPARATE_CODE_AND_RODATA=0, the layout is unchanged, i.e.
   the read-only section still looks like this (padding omitted):

   |        ...        |
   +-------------------+
   | Exception vectors |
   +-------------------+
   |  Read-only data   |
   +-------------------+
   |       Code        |
   +-------------------+ BLx_BASE

   In this case, the linker script provides the limits of the whole
   read-only section.

 - When SEPARATE_CODE_AND_RODATA=1, the exception vectors and
   read-only data are swapped, such that the code and exception
   vectors are contiguous, followed by the read-only data. This
   gives the following new layout (padding omitted):

   |        ...        |
   +-------------------+
   |  Read-only data   |
   +-------------------+
   | Exception vectors |
   +-------------------+
   |       Code        |
   +-------------------+ BLx_BASE

   In this case, the linker script now exports 2 sets of addresses
   instead: the limits of the code and the limits of the read-only
   data. Refer to the Firmware Design guide for more details. This
   provides platform code with a finer-grained view of the image
   layout and allows it to map these 2 regions with the appropriate
   access permissions.

Note that SEPARATE_CODE_AND_RODATA applies to all BL images.

Change-Id: I936cf80164f6b66b6ad52b8edacadc532c935a49

This patch adds a new linker symbol in BL1's linker script named
'__BL1_ROM_END__', which marks the end of BL1's ROM content. This
covers BL1's code, read-only data and read-write data to relocate
in Trusted SRAM. The address of this new linker symbol is exported
to C code through the 'BL1_ROM_END' macro.

The section related to linker symbols in the Firmware Design guide
has been updated and improved.

Change-Id: I5c442ff497c78d865ffba1d7d044511c134e11c7

The system registers that are saved and restored in CPU context include
AArch32 systems registers like SPSR_ABT, SPSR_UND, SPSR_IRQ, SPSR_FIQ,
DACR32_EL2, IFSR32_EL2 and FPEXC32_EL2. Accessing these registers on an
AArch64-only (i.e. on hardware that does not implement AArch32, or at
least not at EL1 and higher ELs) platform leads to an exception. This patch
introduces the build option `CTX_INCLUDE_AARCH32_REGS` to specify whether to
include these AArch32 systems registers in the cpu context or not. By default
this build option is set to 1 to ensure compatibility. AArch64-only platforms
must set it to 0. A runtime check is added in BL1 and BL31 cold boot path to
verify this.

Fixes ARM-software/tf-issues#386

Change-Id: I720cdbd7ed7f7d8516635a2ec80d025f478b95ee