Declare PAuth for Secure world as experimental

Declare ENABLE_PAUTH and CTX_INCLUDE_PAUTH_REGS
build options as experimental.
Pointer Authentication is enabled for Non-secure world
irrespective of the value of these build flags if the
CPU supports it.
The patch also fixes the description of fiptool 'help' command.

Change-Id: I46de3228fbcce774a2624cd387798680d8504c38
Signed-off-by: Alexei Fedorov <Alexei.Fedorov@arm.com>

Makefile

@@ -478,6 +478,12 @@ endif
 ifeq ($(ENABLE_PAUTH),1)
     ifeq ($(CTX_INCLUDE_PAUTH_REGS),0)
         $(error ENABLE_PAUTH=1 requires CTX_INCLUDE_PAUTH_REGS=1)
+    else
+        $(info ENABLE_PAUTH and CTX_INCLUDE_PAUTH_REGS are experimental features)
+    endif
+else
+    ifeq ($(CTX_INCLUDE_PAUTH_REGS),1)
+        $(info CTX_INCLUDE_PAUTH_REGS is an experimental feature)
     endif
 endif
 

docs/firmware-design.rst

@@ -2565,11 +2565,16 @@ Armv8.3-A
    must be set to 1. This will add all pointer authentication system registers
    to the context that is saved when doing a world switch.
 
-   The Trusted Firmware itself has support for pointer authentication at runtime
+   The TF-A itself has support for pointer authentication at runtime
    that can be enabled by setting both options ``ENABLE_PAUTH`` and
    ``CTX_INCLUDE_PAUTH_REGS`` to 1. This enables pointer authentication in BL1,
    BL2, BL31, and the TSP if it is used.
 
+   These options are experimental features.
+
+   Note that Pointer Authentication is enabled for Non-secure world irrespective
+   of the value of these build flags if the CPU supports it.
+
    If ``ARM_ARCH_MAJOR == 8`` and ``ARM_ARCH_MINOR >= 3`` the code footprint of
    enabling PAuth is lower because the compiler will use the optimized
    PAuth instructions rather than the backwards-compatible ones.

docs/user-guide.rst

@@ -358,11 +358,12 @@ Common build options
    registers to be included when saving and restoring the CPU context. Default
    is 0.
 
--  ``CTX_INCLUDE_PAUTH_REGS``: Boolean option that, when set to 1, will cause
-   the ARMv8.3-PAuth registers to be included when saving and restoring the CPU
-   context. Note that if the hardware supports this extension and this option is
-   set to 0 the value of the registers will be leaked between Secure and
-   Non-secure worlds if PAuth is used on both sides. The default is 0.
+-  ``CTX_INCLUDE_PAUTH_REGS``: Boolean option that, when set to 1, enables
+   Pointer Authentication for Secure world. This will cause the ARMv8.3-PAuth
+   registers to be included when saving and restoring the CPU context as
+   part of world switch. Default value is 0 and this is an experimental feature.
+   Note that Pointer Authentication is enabled for Non-secure world irrespective
+   of the value of this flag if the CPU supports it.
 
 -  ``DEBUG``: Chooses between a debug and release build. It can take either 0
    (release) or 1 (debug) as values. 0 is the default.
@@ -412,11 +413,11 @@ Common build options
    and use partitions in EL3 as required. This option defaults to ``0``.
 
 -  ``ENABLE_PAUTH``: Boolean option to enable ARMv8.3 Pointer Authentication
-   (``ARMv8.3-PAuth``) support in the Trusted Firmware itself. Note that this
-   option doesn't affect the saving of the registers introduced with this
-   extension, they are always saved if they are detected regardless of the value
-   of this option. If enabled, it is needed to use a compiler that supports the
-   option ``-msign-return-address``. It defaults to 0.
+  support for TF-A BL images itself. If enabled, it is needed to use a compiler 
+  that supports the option ``-msign-return-address``. This flag defaults to 0
+  and this is an experimental feature.
+  Note that Pointer Authentication is enabled for Non-secure world irrespective
+  of the value of this flag if the CPU supports it.
 
 -  ``ENABLE_PIE``: Boolean option to enable Position Independent Executable(PIE)
    support within generic code in TF-A. This option is currently only supported
@@ -1049,7 +1050,7 @@ The tool binary can be located in:
 
     ./tools/fiptool/fiptool
 
-Invoking the tool with ``--help`` will print a help message with all available
+Invoking the tool with ``help`` will print a help message with all available
 options.
 
 Example 1: create a new Firmware package ``fip.bin`` that contains BL2 and BL31: