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Enforce full include path for includes. Deprecate old paths.

The following folders inside include/lib have been left unchanged:

- include/lib/cpus/${ARCH}
- include/lib/el3_runtime/${ARCH}

The reason for this change is that having a global namespace for
includes isn't a good idea. It defeats one of the advantages of having
folders and it introduces problems that are sometimes subtle (because
you may not know the header you are actually including if there are two
of them).

For example, this patch had to be created because two headers were
called the same way: e0ea0928 ("Fix gpio includes of mt8173 platform
to avoid collision."). More recently, this patch has had similar
problems: 46f9b2c3 ("drivers: add tzc380 support").

This problem was introduced in commit 4ecca339

 ("Move include and
source files to logical locations"). At that time, there weren't too
many headers so it wasn't a real issue. However, time has shown that
this creates problems.

Platforms that want to preserve the way they include headers may add the
removed paths to PLAT_INCLUDES, but this is discouraged.

Change-Id: I39dc53ed98f9e297a5966e723d1936d6ccf2fc8f
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>

The architecture dependant header files in include/lib/${ARCH} and
include/common/${ARCH} have been moved to /include/arch/${ARCH}.

Change-Id: I96f30fdb80b191a51448ddf11b1d4a0624c03394
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>

All identifiers, regardless of use, that start with two underscores are
reserved. This means they can't be used in header guards.

The style that this project is now to use the full name of the file in
capital letters followed by 'H'. For example, for a file called
"uart_example.h", the header guard is UART_EXAMPLE_H.

The exceptions are files that are imported from other projects:

- CryptoCell driver
- dt-bindings folders
- zlib headers

Change-Id: I50561bf6c88b491ec440d0c8385c74650f3c106e
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>

This patch fixes up the AArch64 assembly code to use
adrp/adr instructions instead of ldr instruction for
reference to symbols. This allows these assembly
sequences to be Position Independant. Note that the
the reference to sizes have been replaced with
calculation of size at runtime. This is because size
is a constant value and does not depend on execution
address and using PC relative instructions for loading
them makes them relative to execution address. Also
we cannot use `ldr` instruction to load size as it
generates a dynamic relocation entry which must *not*
be fixed up and it is difficult for a dynamic loader
to differentiate which entries need to be skipped.

Change-Id: I8bf4ed5c58a9703629e5498a27624500ef40a836
Signed-off-by: Soby Mathew <soby.mathew@arm.com>

Change-Id: Icd1cdd42afdc78895a9be6c46b414b0a155cfa63
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>

Change-Id: I40d040aa05bcbf11536a96ce59827711456b93a8
Co-authored-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>

Check_vector_size checks if the size of the vector fits
in the size reserved for it. This check creates problems in
the Clang assembler. A new macro, end_vector_entry, is added
and check_vector_size is deprecated.

This new macro fills the current exception vector until the next
exception vector. If the size of the current vector is bigger
than 32 instructions then it gives an error.

Change-Id: Ie8545cf1003a1e31656a1018dd6b4c28a4eaf671
Signed-off-by: Roberto Vargas <roberto.vargas@arm.com>

These directives are only used when stabs debugging information
is used, but we use ELF which uses DWARF debugging information.
Clang assembler doesn't support these directives, and removing
them makes the code more compatible with clang.

Change-Id: I2803f22ebd24c0fe248e04ef1b17de9cec5f89c4
Signed-off-by: Roberto Vargas <roberto.vargas@arm.com>

At present, the function provided by the translation library to enable
MMU constructs appropriate values for translation library, and programs
them to the right registers. The construction of initial values,
however, is only required once as both the primary and secondaries
program the same values.

Additionally, the MMU-enabling function is written in C, which means
there's an active stack at the time of enabling MMU. On some systems,
like Arm DynamIQ, having active stack while enabling MMU during warm
boot might lead to coherency problems.

This patch addresses both the above problems by:

  - Splitting the MMU-enabling function into two: one that sets up
    values to be programmed into the registers, and another one that
    takes the pre-computed values and writes to the appropriate
    registers. With this, the primary effectively calls both functions
    to have the MMU enabled, but secondaries only need to call the
    latter.

  - Rewriting the function that enables MMU in assembly so that it
    doesn't use stack.

This patch fixes a bunch of MISRA issues on the way.

Change-Id: I0faca97263a970ffe765f0e731a1417e43fbfc45
Signed-off-by: Jeenu Viswambharan <jeenu.viswambharan@arm.com>

RAS extensions are mandatory for ARMv8.2 CPUs, but are also optional
extensions to base ARMv8.0 architecture.

This patch adds build system support to enable RAS features in ARM
Trusted Firmware. A boolean build option RAS_EXTENSION is introduced for
this.

With RAS_EXTENSION, an Exception Synchronization Barrier (ESB) is
inserted at all EL3 vector entry and exit. ESBs will synchronize pending
external aborts before entering EL3, and therefore will contain and
attribute errors to lower EL execution. Any errors thus synchronized are
detected via. DISR_EL1 register.

When RAS_EXTENSION is set to 1, HANDLE_EL3_EA_FIRST must also be set to 1.

Change-Id: I38a19d84014d4d8af688bd81d61ba582c039383a
Signed-off-by: Jeenu Viswambharan <jeenu.viswambharan@arm.com>

A Secure Partition is a software execution environment instantiated in
S-EL0 that can be used to implement simple management and security
services. Since S-EL0 is an unprivileged exception level, a Secure
Partition relies on privileged firmware e.g. ARM Trusted Firmware to be
granted access to system and processor resources. Essentially, it is a
software sandbox that runs under the control of privileged software in
the Secure World and accesses the following system resources:

- Memory and device regions in the system address map.
- PE system registers.
- A range of asynchronous exceptions e.g. interrupts.
- A range of synchronous exceptions e.g. SMC function identifiers.

A Secure Partition enables privileged firmware to implement only the
absolutely essential secure services in EL3 and instantiate the rest in
a partition. Since the partition executes in S-EL0, its implementation
cannot be overly complex.

The component in ARM Trusted Firmware responsible for managing a Secure
Partition is called the Secure Partition Manager (SPM). The SPM is
responsible for the following:

- Validating and allocating resources requested by a Secure Partition.
- Implementing a well defined interface that is used for initialising a
  Secure Partition.
- Implementing a well defined interface that is used by the normal world
  and other secure services for accessing the services exported by a
  Secure Partition.
- Implementing a well defined interface that is used by a Secure
  Partition to fulfil service requests.
- Instantiating the software execution environment required by a Secure
  Partition to fulfil a service request.

Change-Id: I6f7862d6bba8732db5b73f54e789d717a35e802f
Co-authored-by: Douglas Raillard <douglas.raillard@arm.com>
Co-authored-by: Sandrine Bailleux <sandrine.bailleux@arm.com>
Co-authored-by: Achin Gupta <achin.gupta@arm.com>
Co-authored-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>

Add Call Frame Information assembler directives to vector entries so
that debuggers display the backtrace of functions that triggered a
synchronous exception. For example, a function triggering a data abort
will be easier to debug if the backtrace can be displayed from a
breakpoint at the beginning of the synchronous exception vector.

DS-5 needs CFI otherwise it will not attempt to display the backtrace.
Other debuggers might have other needs. These debug information are
stored in the ELF file but not in the final binary.

Change-Id: I32dc4e4b7af02546c93c1a45c71a1f6d710d36b1
Signed-off-by: Douglas Raillard <douglas.raillard@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>

At present, spin locks can only defined from C files. Add some macros
such that they can be defined from assembly files too.

Change-Id: I64f0c214062f5c15b3c8b412c7f25c908e87d970
Signed-off-by: Jeenu Viswambharan <jeenu.viswambharan@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>

This patch moves assembler macros which are not architecture specific
to a new file `asm_macros_common.S` and moves the `el3_common_macros.S`
into `aarch64` specific folder.

Change-Id: I444a1ee3346597bf26a8b827480cd9640b38c826

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

The per-cpu stacks should be aligned to the cache-line size and
the `declare_stack` helper in asm_macros.S macro assumed a
cache-line size of 64 bytes. The platform defines the cache-line
size via CACHE_WRITEBACK_GRANULE macro. This patch modifies
`declare_stack` helper macro to derive stack alignment from the
platform defined macro.

Change-Id: I1e1b00fc8806ecc88190ed169f4c8d3dd25fe95b

The documentation of the GNU assembler specifies the following about
the .align assembler directive:
 "the padding bytes are normally zero. However, on some systems, if
 the section is marked as containing code and the fill value is
 omitted, the space is filled with no-op instructions."
(see https://sourceware.org/binutils/docs/as/Align.html)

When building Trusted Firmware, the AArch64 GNU assembler uses a
mix of zero bytes and no-op instructions as the padding bytes to
align exception vectors.

This patch mandates to use zero bytes to be stored in the padding
bytes in the exception vectors. In the AArch64 instruction set, no
valid instruction encodes as zero so this effectively inserts
illegal instructions. Should this code end up being executed for
any reason, it would crash immediately. This gives us an extra
protection against misbehaving code at no extra cost.

Change-Id: I4f2abb39d0320ca0f9d467fc5af0cb92ae297351

This patch introduces some assembler macros to simplify the
declaration of the exception vectors. It abstracts the section
the exception code is put into as well as the alignments
constraints mandated by the ARMv8 architecture. For all TF images,
the exception code has been updated to make use of these macros.

This patch also updates some invalid comments in the exception
vector code.

Change-Id: I35737b8f1c8c24b6da89b0a954c8152a4096fa95

This patch changes the build time behaviour when using deprecated API within
Trusted Firmware. Previously the use of deprecated APIs would only trigger a
build warning (which was always treated as a build error), when
WARN_DEPRECATED = 1. Now, the use of deprecated C declarations will always
trigger a build time warning. Whether this warning is treated as error or not
is determined by the build flag ERROR_DEPRECATED which is disabled by default.
When the build flag ERROR_DEPRECATED=1, the invocation of deprecated API or
inclusion of deprecated headers will result in a build error.

Also the deprecated context management helpers in context_mgmt.c are now
conditionally compiled depending on the value of ERROR_DEPRECATED flag
so that the APIs themselves do not result in a build error when the
ERROR_DEPRECATED flag is set.

NOTE: Build systems that use the macro WARN_DEPRECATED must migrate to
using ERROR_DEPRECATED, otherwise deprecated API usage will no longer
trigger a build error.

Change-Id: I843bceef6bde979af7e9b51dddf861035ec7965a

This patch defines deprecated platform APIs to enable Trusted
Firmware components like Secure Payload and their dispatchers(SPD)
to continue to build and run when platform compatibility is disabled.
This decouples the migration of platform ports to the new platform API
from SPD and enables them to be migrated independently. The deprecated
platform APIs defined in this patch are : platform_get_core_pos(),
platform_get_stack() and platform_set_stack().

The patch also deprecates MPIDR based context management helpers like
cm_get_context_by_mpidr(), cm_set_context_by_mpidr() and cm_init_context().
A mechanism to deprecate APIs and identify callers of these APIs during
build is introduced, which is controlled by the build flag WARN_DEPRECATED.
If WARN_DEPRECATED is defined to 1, the users of the deprecated APIs will be
flagged either as a link error for assembly files or compile time warning
for C files during build.

Change-Id: Ib72c7d5dc956e1a74d2294a939205b200f055613

This commit does the switch to the new PSCI framework implementation replacing
the existing files in PSCI folder with the ones in PSCI1.0 folder. The
corresponding makefiles are modified as required for the new implementation.
The platform.h header file is also is switched to the new one
as required by the new frameworks. The build flag ENABLE_PLAT_COMPAT defaults
to 1 to enable compatibility layer which let the existing platform ports to
continue to build and run with minimal changes.

The default weak implementation of platform_get_core_pos() is now removed from
platform_helpers.S and is provided by the compatibility layer.

Note: The Secure Payloads and their dispatchers still use the old platform
and framework APIs and hence it is expected that the ENABLE_PLAT_COMPAT build
flag will remain enabled in subsequent patch. The compatibility for SPDs using
the older APIs on platforms migrated to the new APIs will be added in the
following patch.

Change-Id: I18c51b3a085b564aa05fdd98d11c9f3335712719

This patch introduces new platform APIs and context management helper APIs
to support the new topology framework based on linear core position. This
framework will be introduced in the follwoing patch and it removes the
assumption that the MPIDR based affinity levels map directly to levels
in a power domain tree. The new platforms APIs and context management
helpers based on core position are as described below:

* plat_my_core_pos() and plat_core_pos_by_mpidr()

These 2 new mandatory platform APIs are meant to replace the existing
'platform_get_core_pos()' API. The 'plat_my_core_pos()' API returns the
linear index of the calling core and 'plat_core_pos_by_mpidr()' returns
the linear index of a core specified by its MPIDR. The latter API will also
validate the MPIDR passed as an argument and will return an error code (-1)
if an invalid MPIDR is passed as the argument. This enables the caller to
safely convert an MPIDR of another core to its linear index without querying
the PSCI topology tree e.g. during a call to PSCI CPU_ON.

Since the 'plat_core_pos_by_mpidr()' API verifies an MPIDR, which is always
platform specific, it is no longer possible to maintain a default implementation
of this API. Also it might not be possible for a platform port to verify an
MPIDR before the C runtime has been setup or the topology has been initialized.
This would prevent 'plat_core_pos_by_mpidr()' from being callable prior to
topology setup. As a result, the generic Trusted Firmware code does not call
this API before the topology setup has been done.

The 'plat_my_core_pos' API should be able to run without a C runtime.
Since this API needs to return a core position which is equal to the one
returned by 'plat_core_pos_by_mpidr()' API for the corresponding MPIDR,
this too cannot have default implementation and is a mandatory API for
platform ports. These APIs will be implemented by the ARM reference platform
ports later in the patch stack.

* plat_get_my_stack() and plat_set_my_stack()

These APIs are the stack management APIs which set/return stack addresses
appropriate for the calling core. These replace the 'platform_get_stack()' and
'platform_set_stack()' APIs. A default weak MP version and a global UP version
of these APIs are provided for the platforms.

* Context management helpers based on linear core position

A set of new context management(CM) helpers viz cm_get_context_by_index(),
cm_set_context_by_index(), cm_init_my_context() and cm_init_context_by_index()
are defined which are meant to replace the old helpers which took MPIDR
as argument. The old CM helpers are implemented based on the new helpers to
allow for code consolidation and will be deprecated once the switch to the new
framework is done.

Change-Id: I89758632b370c2812973a4b2efdd9b81a41f9b69

The attempt to run the CPU reset code as soon as possible after reset
results in highly complex conditional code relating to the
RESET_TO_BL31 option.

This patch relaxes this requirement a little. In the BL1, BL3-1 and
PSCI entrypoints code, the sequence of operations is now as follows:
 1) Detect whether it is a cold or warm boot;
 2) For cold boot, detect whether it is the primary or a secondary
    CPU. This is needed to handle multiple CPUs entering cold reset
    simultaneously;
 3) Run the CPU init code.

This patch also abstracts the EL3 registers initialisation done by
the BL1, BL3-1 and PSCI entrypoints into common code.

This improves code re-use and consolidates the code flows for
different types of systems.

NOTE: THE FUNCTION plat_secondary_cold_boot() IS NOW EXPECTED TO
NEVER RETURN. THIS PATCH FORCES PLATFORM PORTS THAT RELIED ON THE
FORMER RETRY LOOP AT THE CALL SITE TO MODIFY THEIR IMPLEMENTATION.
OTHERWISE, SECONDARY CPUS WILL PANIC.

Change-Id: If5ecd74d75bee700b1bd718d23d7556b8f863546

Some assembly files containing macros are included like header files
into other assembly files. This will cause assembler errors if they
are included multiple times.

Add header guards to assembly macro files to avoid assembler errors.

Change-Id: Ia632e767ed7df7bf507b294982b8d730a6f8fe69

In order for the symbol table in the ELF file to contain the size of
functions written in assembly, it is necessary to report it to the
assembler using the .size directive.

To fulfil the above requirements, this patch introduces an 'endfunc'
macro which contains the .endfunc and .size directives. It also adds
a .func directive to the 'func' assembler macro.

The .func/.endfunc have been used so the assembler can fail if
endfunc is omitted.

Fixes ARM-Software/tf-issues#295

Change-Id: If8cb331b03d7f38fe7e3694d4de26f1075b278fc
Signed-off-by: Kévin Petit <kevin.petit@arm.com>

This patch introduces platform APIs to initialise and
print a character on a designated crash console.
For the FVP platform, PL011_UART0 is the designated
crash console. The platform porting guide is also updated
to document the new APIs.

Change-Id: I5e97d8762082e0c88c8c9bbb479353eac8f11a66

This change adds optional reset vector support to BL3-1
which means BL3-1 entry point can detect cold/warm boot,
initialise primary cpu, set up cci and mail box.

When using BL3-1 as a reset vector it is assumed that
the BL3-1 platform code can determine the location of
the BL3-2 images, or load them as there are no parameters
that can be passed to BL3-1 at reset.

It also fixes the incorrect initialisation of mailbox
registers on the FVP platform

This feature can be enabled by building the code with
make variable RESET_TO_BL31 set as 1

Fixes ARM-software/TF-issues#133
Fixes ARM-software/TF-issues#20

Change-Id: I4e23939b1c518614b899f549f1e8d412538ee570

The data cache clean and invalidate operations dcsw_op_all()
and dcsw_op_loius() were implemented to invoke a DSB and ISB
barrier for every set/way operation. This adds a substantial
performance penalty to an already expensive operation.

These functions have been reworked to provide an optimised
implementation derived from the code in section D3.4 of the
ARMv8 ARM. The helper macro setup_dcsw_op_args has been moved
and reworked alongside the implementation.

Fixes ARM-software/tf-issues#146

Change-Id: Icd5df57816a83f0a842fce935320a369f7465c7f

Instead of using the system register helper functions to read
or write system registers, assembler coded functions should
use MRS/MSR instructions. This results in faster and more
compact code.

This change replaces all usage of the helper functions with
direct register accesses.

Change-Id: I791d5f11f257010bb3e6a72c6c5ab8779f1982b3

Reduce the number of header files included from other header
files as much as possible without splitting the files. Use forward
declarations where possible. This allows removal of some unnecessary
"#ifndef __ASSEMBLY__" statements.

Also, review the .c and .S files for which header files really need
including and reorder the #include statements alphabetically.

Fixes ARM-software/tf-issues#31

Change-Id: Iec92fb976334c77453e010b60bcf56f3be72bd3e

Move almost all system include files to a logical sub-directory
under ./include. The only remaining system include directories
not under ./include are specific to the platform. Move the
corresponding source files to match the include directory
structure.

Also remove pm.h as it is no longer used.

Change-Id: Ie5ea6368ec5fad459f3e8a802ad129135527f0b3

The BL images share common stack management code which provides
one coherent and one cacheable stack for every CPU. BL1 and BL2
just execute on the primary CPU during boot and do not require
the additional CPU stacks. This patch provides separate stack
support code for UP and MP images, substantially reducing the
RAM usage for BL1 and BL2 for the FVP platform.

This patch also provides macros for declaring stacks and
calculating stack base addresses to improve consistency where
this has to be done in the firmware.

The stack allocation source files are now included via
platform.mk rather than the common BLx makefiles. This allows
each platform to select the appropriate MP/UP stack support
for each BL image.

Each platform makefile must be updated when including this
commit.

Fixes ARM-software/tf-issues#76

Change-Id: Ia251f61b8148ffa73eae3f3711f57b1ffebfa632

This extends the --gc-sections behaviour to the many assembler
support functions in the firmware images by placing each function
into its own code section. This is achieved by creating a 'func'
macro used to declare each function label.

Fixes ARM-software/tf-issues#80

Change-Id: I301937b630add292d2dec6d2561a7fcfa6fec690

This patch adds guards so that an exception vector exceeding 32
instructions will generate a compile-time error. This keeps the
exception handlers in check from spilling over.

Change-Id: I7aa56dd0071a333664e2814c656d3896032046fe

This patch uses the reworked exception handling support to handle
runtime service requests through SMCs following the SMC calling
convention. This is a giant commit since all the changes are
inter-related. It does the following:

1. Replace the old exception handling mechanism with the new one
2. Enforce that SP_EL0 is used C runtime stacks.
3. Ensures that the cold and warm boot paths use the 'cpu_context'
   structure to program an ERET into the next lower EL.
4. Ensures that SP_EL3 always points to the next 'cpu_context'
   structure prior to an ERET into the next lower EL
5. Introduces a PSCI SMC handler which completes the use of PSCI as a
   runtime service

Change-Id: I661797f834c0803d2c674d20f504df1b04c2b852
Co-authored-by: Achin Gupta <achin.gupta@arm.com>

This patch introduces the reworked exception handling logic which lays
the foundation for accessing runtime services in later patches. The
type of an exception has a greater say in the way it is
handled. SP_EL3 is used as the stack pointer for:

1. Determining the type of exception and handling the unexpected ones
   on the exception stack

2. Saving and restoring the essential general purpose and system
   register state after exception entry and prior to exception exit.

SP_EL0 is used as the stack pointer for handling runtime service
requests e.g. SMCs. A new structure for preserving general purpose
register state has been added to the 'cpu_context' structure. All
assembler ensures that it does not use callee saved registers
(x19-x29). The C runtime preserves them across functions calls. Hence
EL3 code does not have to save and restore them explicitly.

Since the exception handling framework has undergone substantial change,
the changes have been kept in separate files to aid readability. These
files will replace the existing ones in subsequent patches.

Change-Id: Ice418686592990ff7a4260771e8d6676e6c8c5ef

Change-Id: Ic7fb61aabae1d515b9e6baf3dd003807ff42da60

The runtime exception handling assembler code used magic numbers for
saving and restoring the general purpose register context on stack
memory. The memory is interpreted as a 'gp_regs' structure and the
magic numbers are offsets to members of this structure. This patch
replaces the magic number offsets with constants. It also adds compile
time assertions to prevent an incorrect assembler view of this
structure.

Change-Id: Ibf125bfdd62ba3a33e58c5f1d71f8c229720781c