GitLab

As per latest mailing communication [1], we decided to
update AT speculative workaround implementation in order to
disable page table walk for lower ELs(EL1 or EL0) immediately
after context switching to EL3 from lower ELs.

Previous implementation of AT speculative workaround is available
here: 45aecff0

AT speculative workaround is updated as below:
1. Avoid saving and restoring of SCTLR and TCR registers for EL1
   in context save and restore routine respectively.
2. On EL3 entry, save SCTLR and TCR registers for EL1.
3. On EL3 entry, update EL1 system registers to disable stage 1
   page table walk for lower ELs (EL1 and EL0) and enable EL1
   MMU.
4. On EL3 exit, restore SCTLR and TCR registers for EL1 which
   are saved in step 2.

[1]:
https://lists.trustedfirmware.org/pipermail/tf-a/2020-July/000586.html



Change-Id: Iee8de16f81dc970a8f492726f2ddd57e7bd9ffb5
Signed-off-by: Manish V Badarkhe <Manish.Badarkhe@arm.com>

In case of AT speculative workaround applied, page table walk
is disabled for lower ELs (EL1 and EL0) in EL3.
Hence added a wrapper function which temporarily enables page
table walk to execute AT instruction for lower ELs and then
disables page table walk.

Execute AT instructions directly for lower ELs (EL1 and EL0)
assuming page table walk is enabled always when AT speculative
workaround is not applied.

Change-Id: I4ad4c0bcbb761448af257e9f72ae979473c0dde8
Signed-off-by: Manish V Badarkhe <Manish.Badarkhe@arm.com>

This patch fixes the bug when AMUv1 group1 counters was
always assumed being implemented without checking for its
presence which was causing exception otherwise.
The AMU extension code was also modified as listed below:
- Added detection of AMUv1 for ARMv8.6
- 'PLAT_AMU_GROUP1_NR_COUNTERS' build option is removed and
number of group1 counters 'AMU_GROUP1_NR_COUNTERS' is now
calculated based on 'AMU_GROUP1_COUNTERS_MASK' value
- Added bit fields definitions and access functions for
AMCFGR_EL0/AMCFGR and AMCGCR_EL0/AMCGCR registers
- Unification of amu.c Aarch64 and Aarch32 source files
- Bug fixes and TF-A coding style compliant changes.

Change-Id: I14e407be62c3026ebc674ec7045e240ccb71e1fb
Signed-off-by: Alexei Fedorov <Alexei.Fedorov@arm.com>

This patch adds a build config 'RAS_TRAP_LOWER_EL_ERR_ACCESS' to set
SCR_EL3.TERR during CPU boot. This bit enables trapping RAS register
accesses from EL1 or EL2 to EL3.

RAS_TRAP_LOWER_EL_ERR_ACCESS is disabled by default.
Signed-off-by: Varun Wadekar <vwadekar@nvidia.com>
Change-Id: Ifb0fb0afedea7dd2a29a0b0491a1161ecd241438

Enhanced Counter Virtualization, ECV, is an architecture extension introduced
in ARMv8.6. This extension allows the hypervisor, at EL2, to setup
self-synchronizing views of the timers for it's EL1 Guests. This patch pokes the
control register to enable this extension when booting a hypervisor at EL2.

Change-Id: I4e929ecdf400cea17eff1de5cf8704aa7e40973d
Signed-off-by: Jimmy Brisson <jimmy.brisson@arm.com>

The Fine Grained Traps (FGT) architecture extension was added to aarch64 in
ARMv8.6. This extension primarily allows hypervisors, at EL2, to trap specific
instructions in a more fine grained manner, with an enable bit for each
instruction. This patch adds support for this extension by enabling the
extension when booting an hypervisor at EL2.

Change-Id: Idb9013ed118b6a1b7b76287237096de992ca4da3
Signed-off-by: Jimmy Brisson <jimmy.brisson@arm.com>

This patch fixes wrong ID_AA64DFR0_EL1 register read instead of
ID_AA64PFR0_EL1 to detect support for MPAM extension.
It also implements get_mpam_version() function which returns
MPAM version as:
0x00: None Armv8.0 or later;
0x01: v0.1 Armv8.4 or later;
0x10: v1.0 Armv8.2 or later;
0x11: v1.1 Armv8.4 or later;

Change-Id: I31d776b1a1b60cb16e5e62296d70adb129d7b760
Reported-by: Matteo Zini <matteozini96@gmail.com>
Signed-off-by: Alexei Fedorov <Alexei.Fedorov@arm.com>

This patch enables the v8.6 extension to add a delay before WFE traps
are taken. A weak hook plat_arm_set_twedel_scr_el3 has been added in
plat/common/aarch64/plat_common.c that disables this feature by default
but platform-specific code can override it when needed.

The only hook provided sets the TWED fields in SCR_EL3, there are similar
fields in HCR_EL2, SCTLR_EL2, and SCTLR_EL1 to control WFE trap delays in
lower ELs but these should be configured by code running at EL2 and/or EL1
depending on the platform configuration and is outside the scope of TF-A.
Signed-off-by: John Powell <john.powell@arm.com>
Change-Id: I0a9bb814205efeab693a3d0a0623e62144abba2d

This patch fixes compilation errors when ENABLE_PIE=1.

<snip>
bl31/aarch64/bl31_entrypoint.S: Assembler messages:
bl31/aarch64/bl31_entrypoint.S:61: Error: invalid operand (*UND* section) for `~'
bl31/aarch64/bl31_entrypoint.S:61: Error: invalid immediate
Makefile:1079: recipe for target 'build/tegra/t194/debug/bl31/bl31_entrypoint.o' failed
<snip>

Verified by setting 'ENABLE_PIE=1' for Tegra platform builds.
Signed-off-by: Varun Wadekar <vwadekar@nvidia.com>
Change-Id: Ifd184f89b86b4360fda86a6ce83fd8495f930bbc

During context switching from higher EL (EL2 or higher)
to lower EL can cause incorrect translation in TLB due to
speculative execution of AT instruction using out-of-context
translation regime.

Workaround is implemented as below during EL's (EL1 or EL2)
"context_restore" operation:
1. Disable page table walk using SCTLR.M and TCR.EPD0 & EPD1
   bits for EL1 or EL2 (stage1 and stage2 disabled)
2. Save all system registers except TCR and SCTLR (for EL1 and EL2)
3. Do memory barrier operation (isb) to ensure all
   system register writes are done.
4. Restore TCR and SCTLR registers (for EL1 and EL2)

Errata details are available for various CPUs as below:
Cortex-A76: 1165522
Cortex-A72: 1319367
Cortex-A57: 1319537
Cortex-A55: 1530923
Cortex-A53: 1530924

More details can be found in mail-chain:
https://lists.trustedfirmware.org/pipermail/tf-a/2020-April/000445.html



Currently, Workaround is implemented as build option which is default
disabled.
Signed-off-by: Manish V Badarkhe <Manish.Badarkhe@arm.com>
Change-Id: If8545e61f782cb0c2dda7ffbaf50681c825bd2f0

As a follow-up to bdd2596d

, and related to SPM Dispatcher
EL3 component and SPM Core S-EL2/S-EL1 component: update
with cosmetic and coding rules changes. In addition:
-Add Armv8.4-SecEL2 arch detection helper.
-Add an SPMC context (on current core) get helper.
-Return more meaningful error return codes.
-Remove complexity in few spmd_smc_handler switch-cases.
-Remove unused defines and structures from spmd_private.h
Signed-off-by: Olivier Deprez <olivier.deprez@arm.com>
Change-Id: I99e642450b0dafb19d3218a2f0e2d3107e8ca3fe

By writing 0 to CLUSTERPWRDN DSU register bit 0, we send an
advisory to the power controller that cluster power is not required
when all cores are powered down.

The AArch32 CLUSTERPWRDN register is architecturally mapped to the
AArch64 CLUSTERPWRDN_EL1 register

Change-Id: Ie6e67c1c7d811fa25c51e2e405ca7f59bd20c81b
Signed-off-by: Madhukar Pappireddy <madhukar.pappireddy@arm.com>

bakery_lock_normal.c uses the raw register accessor, read_sctlr(_el3)
to check whether the dcache is enabled.

Using is_dcache_enabled() is cleaner, and a good abstraction for
the library code like this.

A problem is is_dcache_enabled() is declared in the local header,
lib/xlat_tables_v2/xlat_tables_private.h

I searched for a good place to declare this helper. Moving it to
arch_helpers.h, closed to cache operation helpers, looks good enough
to me.

I also changed the type of 'is_cached' to bool for consistency,
and to avoid MISRA warnings.

Change-Id: I9b016f67bc8eade25c316aa9c0db0fa4cd375b79
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

Attempts to address MISRA compliance issues in BL1, BL2, and BL31 code.
Mainly issues like not using boolean expressions in conditionals,
conflicting variable names, ignoring return values without (void), adding
explicit casts, etc.

Change-Id: If1fa18ab621b9c374db73fa6eaa6f6e5e55c146a
Signed-off-by: John Powell <john.powell@arm.com>

There are some cases where we want to run EL-dependent code in the
shared code.

We could use #ifdef, but it leaves slight possibility where we do not
know the exception level at the build-time (e.g. library code).

The counter approach is to use get_current_el(), but it is run-time
detection, so all EL code is linked, some of which might be unneeded.

This commit adds get_current_el_maybe_constant(). This is a static
inline function that returns a constant value if we know the exception
level at build-time. This is mostly the case.

    if (get_current_el_maybe_constant() == 1) {
            /* do something for EL1 */
    } else if (get_current_el_maybe_constant() == 3) {
            /* do something for EL3 */
    }

If get_current_el_maybe_constant() is build-time constant, the compiler
will optimize out the unreachable code.

If such code is included from the library code, it is not built-time
constant. In this case, it falls back to get_current_el(), so it still
works.

Change-Id: Idb03c20342a5b5173fe2d6b40e1fac7998675ad3
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

Change-Id: Ie1018bfbae2fe95c699e58648665baa75e862000
Signed-off-by: Madhukar Pappireddy <madhukar.pappireddy@arm.com>

This patch provides a fix for incorrect crash dump data for
lower EL when TF-A is built with HANDLE_EA_EL3_FIRST=1 option
which enables routing of External Aborts and SErrors to EL3.

Change-Id: I9d5e6775e6aad21db5b78362da6c3a3d897df977
Signed-off-by: Alexei Fedorov <Alexei.Fedorov@arm.com>

This patch adds EL2 registers that are supported up to ARMv8.6.
ARM_ARCH_MINOR has to specified to enable save/restore routine.

Note: Following registers are still not covered in save/restore.
 * AMEVCNTVOFF0<n>_EL2
 * AMEVCNTVOFF1<n>_EL2
 * ICH_AP0R<n>_EL2
 * ICH_AP1R<n>_EL2
 * ICH_LR<n>_EL2

Change-Id: I4813f3243e56e21cb297b31ef549a4b38d4876e1
Signed-off-by: Max Shvetsov <maksims.svecovs@arm.com>

NOTE: Not all EL-2 system registers are saved/restored.
This subset includes registers recognized by ARMv8.0

Change-Id: I9993c7d78d8f5f8e72d1c6c8d6fd871283aa3ce0
Signed-off-by: Jose Marinho <jose.marinho@arm.com>
Signed-off-by: Olivier Deprez <olivier.deprez@arm.com>
Signed-off-by: Artsem Artsemenka <artsem.artsemenka@arm.com>
Signed-off-by: Max Shvetsov <maksims.svecovs@arm.com>

aarch32 CPUs speculatively execute instructions following a
ERET as if it was not a jump instruction. This could lead to
cache-based side channel vulnerabilities. The software fix is
to place barrier instructions following ERET.

The counterpart patch for aarch64 is merged:
https://git.trustedfirmware.org/TF-A/trusted-firmware-a.git/commit/?id=f461fe346b728d0e88142fd7b8f2816415af18bc



Change-Id: I2aa3105bee0b92238f389830b3a3b8650f33af3d
Signed-off-by: Madhukar Pappireddy <madhukar.pappireddy@arm.com>

At each BL entry point, the registers r9 to r12 are used to save info from
the previous BL parameters put in r0 to r3. But zeromem uses r12, leading
to a corruption of arg3. Therefore this change copies r12 to r7 before
zeromem() call and restores r12 afterwards. It may be better to save it
in r7 in el3_arch_init_common and not at the entrypoint as r7 could be used
in other functions, especially platform ones.
This is a fix for Task T661.

Change-Id: Icc11990c69b5d4c542d08aca1a77b1f754b61a53
Signed-off-by: Yann Gautier <yann.gautier@st.com>

This patch modifies the delay timer driver to switch to the ARM
secure physical timer instead of using Tegra's on-chip uS timer.

The secure timer is not accessible to the NS world and so eliminates
an important attack vector, where the Tegra timer source gets switched
off from the NS world leading to a DoS attack for the trusted world.

This timer is shared with the S-EL1 layer for now, but later patches
will mark it as exclusive to the EL3 exception mode.

Change-Id: I2c00f8cb4c48b25578971c626c314603906ad7cc
Signed-off-by: Varun Wadekar <vwadekar@nvidia.com>

At the moment, address demangling is only used by the backtrace
functionality. However, at some point, other parts of the TF-A
codebase may want to use it.
The 'demangle_address' function is replaced with a single XPACI
instruction which is also added in 'do_crash_reporting()'.
Signed-off-by: Alexei Fedorov <Alexei.Fedorov@arm.com>
Change-Id: I4424dcd54d5bf0a5f9b2a0a84c4e565eec7329ec

Even though ERET always causes a jump to another address, aarch64 CPUs
speculatively execute following instructions as if the ERET
instruction was not a jump instruction.
The speculative execution does not cross privilege-levels (to the jump
target as one would expect), but it continues on the kernel privilege
level as if the ERET instruction did not change the control flow -
thus execution anything that is accidentally linked after the ERET
instruction. Later, the results of this speculative execution are
always architecturally discarded, however they can leak data using
microarchitectural side channels. This speculative execution is very
reliable (seems to be unconditional) and it manages to complete even
relatively performance-heavy operations (e.g. multiple dependent
fetches from uncached memory).

This was fixed in Linux, FreeBSD, OpenBSD and Optee OS:
https://github.com/torvalds/linux/commit/679db70801da9fda91d26caf13bf5b5ccc74e8e8
https://github.com/freebsd/freebsd/commit/29fb48ace4186a41c409fde52bcf4216e9e50b61
https://github.com/openbsd/src/commit/3a08873ece1cb28ace89fd65e8f3c1375cc98de2
https://github.com/OP-TEE/optee_os/commit/abfd092aa19f9c0251e3d5551e2d68a9ebcfec8a

It is demonstrated in a SafeSide example:
https://github.com/google/safeside/blob/master/demos/eret_hvc_smc_wrapper.cc
https://github.com/google/safeside/blob/master/kernel_modules/kmod_eret_hvc_smc/eret_hvc_smc_module.c

Signed-off-by: Anthony Steinhauser <asteinhauser@google.com>
Change-Id: Iead39b0b9fb4b8d8b5609daaa8be81497ba63a0f

Some platforms are extremely memory constrained and must split BL31
between multiple non-contiguous areas in SRAM. Allow the NOBITS
sections (.bss, stacks, page tables, and coherent memory) to be placed
in a separate region of RAM from the loaded firmware image.

Because the NOBITS region may be at a lower address than the rest of
BL31, __RW_{START,END}__ and __BL31_{START,END}__ cannot include this
region, or el3_entrypoint_common would attempt to invalidate the dcache
for the entire address space. New symbols __NOBITS_{START,END}__ are
added when SEPARATE_NOBITS_REGION is enabled, and the dcached for the
NOBITS region is invalidated separately.
Signed-off-by: Samuel Holland <samuel@sholland.org>
Change-Id: Idedfec5e4dbee77e94f2fdd356e6ae6f4dc79d37

When a Firmware is complied as Position Independent Executable it needs
to request GDT fixup by passing size of the memory region to
el3_entrypoint_common macro.
The Global descriptor table fixup will be done early on during cold boot
process of primary core.

Currently only BL31 supports PIE, but in future when BL2_AT_EL3 will be
compiled as PIE, it can simply pass fixup size to the common el3
entrypoint macro to fixup GDT.

The reason for this patch was to overcome the bug introduced by SHA
330ead80

 which called fixup routine for each core causing
re-initializing of global pointers thus overwriting any changes
done by the previous core.

Change-Id: I55c792cc3ea9e7eef34c2e4653afd04572c4f055
Signed-off-by: Manish Pandey <manish.pandey2@arm.com>

Check that entry point information requesting S-EL2
has AArch64 as an execution state during context setup.
Signed-off-by: Artsem Artsemenka <artsem.artsemenka@arm.com>
Change-Id: I447263692fed6e55c1b076913e6eb73b1ea735b7

This patch adds support for enabling S-EL2 if this EL is specified in the entry
point information being used to initialise a secure context. It is the caller's
responsibility to check if S-EL2 is available on the system before requesting
this EL through the entry point information.
Signed-off-by: Achin Gupta <achin.gupta@arm.com>
Change-Id: I2752964f078ab528b2e80de71c7d2f35e60569e1

From AArch64 state, arguments are passed in registers W0-W7(X0-X7)
and results are returned in W0-W7(X0-X7) for SMC32(SMC64) calls.
From AArch32 state, arguments are passed in registers R0-R7 and
results are returned in registers R0-R7 for SMC32 calls.

Most of the functions and macros already existed to support using
upto 8 registers for passing/returning parameters/results. Added
few helper macros for SMC calls from AArch32 state.

Link to the specification:
https://developer.arm.com/docs/den0028/c



Change-Id: I87976b42454dc3fc45c8343e9640aa78210e9741
Signed-off-by: Madhukar Pappireddy <madhukar.pappireddy@arm.com>

Currently the MDCR_EL3 initialisation implicitly disables
MDCR_EL3.SPME by using mov_imm.

This patch makes the SPME bit more visible by explicitly
disabling it and documenting its use in different versions
of the architecture.
Signed-off-by: Petre-Ionut Tudor <petre-ionut.tudor@arm.com>
Change-Id: I221fdf314f01622f46ac5aa43388f59fa17a29b3

Add the missing flag for aarch32 XIP memory mode. It was
previously added in aarch64 only.
Minor: Correct the aarch64 missing flag.
Signed-off-by: Lionel Debieve <lionel.debieve@st.com>
Change-Id: Iac0a7581a1fd580aececa75f97deb894858f776f

This patch changes implementation for disabling Secure Cycle
Counter. For ARMv8.5 the counter gets disabled by setting
SDCR.SCCD bit on CPU cold/warm boot. For the earlier
architectures PMCR register is saved/restored on secure
world entry/exit from/to Non-secure state, and cycle counting
gets disabled by setting PMCR.DP bit.
In 'include\aarch32\arch.h' header file new
ARMv8.5-PMU related definitions were added.

Change-Id: Ia8845db2ebe8de940d66dff479225a5b879316f8
Signed-off-by: Alexei Fedorov <Alexei.Fedorov@arm.com>

This patch provides the following features and makes modifications
listed below:
- Individual APIAKey key generation for each CPU.
- New key generation on every BL31 warm boot and TSP CPU On event.
- Per-CPU storage of APIAKey added in percpu_data[]
  of cpu_data structure.
- `plat_init_apiakey()` function replaced with `plat_init_apkey()`
  which returns 128-bit value and uses Generic timer physical counter
  value to increase the randomness of the generated key.
  The new function can be used for generation of all ARMv8.3-PAuth keys
- ARMv8.3-PAuth specific code placed in `lib\extensions\pauth`.
- New `pauth_init_enable_el1()` and `pauth_init_enable_el3()` functions
  generate, program and enable APIAKey_EL1 for EL1 and EL3 respectively;
  pauth_disable_el1()` and `pauth_disable_el3()` functions disable
  PAuth for EL1 and EL3 respectively;
  `pauth_load_bl31_apiakey()` loads saved per-CPU APIAKey_EL1 from
  cpu-data structure.
- Combined `save_gp_pauth_registers()` function replaces calls to
  `save_gp_registers()` and `pauth_context_save()`;
  `restore_gp_pauth_registers()` replaces `pauth_context_restore()`
  and `restore_gp_registers()` calls.
- `restore_gp_registers_eret()` function removed with corresponding
  code placed in `el3_exit()`.
- Fixed the issue when `pauth_t pauth_ctx` structure allocated space
  for 12 uint64_t PAuth registers instead of 10 by removal of macro
  CTX_PACGAKEY_END from `include/lib/el3_runtime/aarch64/context.h`
  and assigning its value to CTX_PAUTH_REGS_END.
- Use of MODE_SP_ELX and MODE_SP_EL0 macro definitions
  in `msr	spsel`  instruction instead of hard-coded values.
- Changes in documentation related to ARMv8.3-PAuth and ARMv8.5-BTI.

Change-Id: Id18b81cc46f52a783a7e6a09b9f149b6ce803211
Signed-off-by: Alexei Fedorov <Alexei.Fedorov@arm.com>

Some of the platform (ie. Agilex) make use of CCU IPs which will only be
initialized during bl2_el3_early_platform_setup. Any operation to the
cache beforehand will crash the platform. Hence, this will provide an
option to skip the data cache invalidation upon bl2 entry at EL3
Signed-off-by: Hadi Asyrafi <muhammad.hadi.asyrafi.abdul.halim@intel.com>
Change-Id: I2c924ed0589a72d0034714c31be8fe57237d1f06

This patch adds support for the Undefined Behaviour sanitizer. There are
two types of support offered - minimalistic trapping support which
essentially immediately crashes on undefined behaviour and full support
with full debug messages.

The full support relies on ubsan.c which has been adapted from code used
by OPTEE.

Change-Id: I417c810f4fc43dcb56db6a6a555bfd0b38440727
Signed-off-by: Justin Chadwell <justin.chadwell@arm.com>

This patch adds support for the new Memory Tagging Extension arriving in
ARMv8.5. MTE support is now enabled by default on systems that support
at EL0. To enable it at ELx for both the non-secure and the secure
world, the compiler flag CTX_INCLUDE_MTE_REGS includes register saving
and restoring when necessary in order to prevent register leakage
between the worlds.

Change-Id: I2d4ea993d6b11654ea0d4757d00ca20d23acf36c
Signed-off-by: Justin Chadwell <justin.chadwell@arm.com>

This patch fixes an issue when secure world timing information
can be leaked because Secure Cycle Counter is not disabled.
For ARMv8.5 the counter gets disabled by setting MDCR_El3.SCCD
bit on CPU cold/warm boot.
For the earlier architectures PMCR_EL0 register is saved/restored
on secure world entry/exit from/to Non-secure state, and cycle
counting gets disabled by setting PMCR_EL0.DP bit.
'include\aarch64\arch.h' header file was tided up and new
ARMv8.5-PMU related definitions were added.

Change-Id: I6f56db6bc77504634a352388990ad925a69ebbfa
Signed-off-by: Alexei Fedorov <Alexei.Fedorov@arm.com>

This patch fixes FVP_Base_AEMv8A model hang issue with
ARMv8.4+ with cache modelling enabled configuration.
Incorrect L1 cache flush operation to PoU, using CLIDR_EL1
LoUIS field, which is required by the architecture to be
zero for ARMv8.4-A with ARMv8.4-S2FWB feature is replaced
with L1 to L2 and L2 to L3 (if L3 is present) cache flushes.
FVP_Base_AEMv8A model can be configured with L3 enabled by
setting `cluster0.l3cache-size` and `cluster1.l3cache-size`
to non-zero values, and presence of L3 is checked in
`aem_generic_core_pwr_dwn` function by reading
CLIDR_EL1.Ctype3 field value.

Change-Id: If3de3d4eb5ed409e5b4ccdbc2fe6d5a01894a9af
Signed-off-by: Alexei Fedorov <Alexei.Fedorov@arm.com>

NOTE: __ASSEMBLY__ macro is now deprecated in favor of __ASSEMBLER__.

All common C compilers predefine a macro called __ASSEMBLER__ when
preprocessing a .S file. There is no reason for TF-A to define it's own
__ASSEMBLY__ macro for this purpose instead. To unify code with the
export headers (which use __ASSEMBLER__ to avoid one extra dependency),
let's deprecate __ASSEMBLY__ and switch the code base over to the
predefined standard.

Change-Id: Id7d0ec8cf330195da80499c68562b65cb5ab7417
Signed-off-by: Julius Werner <jwerner@chromium.org>

This patch introduces an additional precautionary step to further
enhance protection against variant 4. During the context initialisation
before we enter the various BL stages, the SPSR.SSBS bit is explicitly
set to zero. As such, speculative loads/stores are by default disabled
for all BL stages when they start executing. Subsequently, each BL
stage, can choose to enable speculative loads/stores or keep them
disabled.

This change doesn't affect the initial execution context of BL33 which
is totally platform dependent and, thus, it is intentionally left up to
each platform to initialise.

For Arm platforms, SPSR.SSBS is set to zero for BL33 too. This means
that, for Arm platforms, all BL stages start with speculative
loads/stores disabled.

Change-Id: Ie47d39c391d3f20fc2852fc59dbd336f8cacdd6c
Signed-off-by: John Tsichritzis <john.tsichritzis@arm.com>