Hello,
Can someone please help me understand if
1. a 'value' of '1' for BRANCH_PROTECTION covers the PAuth protection provided by a value of '2' and/or '3'? 2. there is a way to enable BTI and "pac-ret" at the same time?
The docs provide this information.
<snip>
- ``BRANCH_PROTECTION``: Numeric value to enable ARMv8.3 Pointer Authentication
and ARMv8.5 Branch Target Identification support for TF-A BL images themselves.
If enabled, it is needed to use a compiler that supports the option
``-mbranch-protection``. Selects the branch protection features to use:
- 0: Default value turns off all types of branch protection
- 1: Enables all types of branch protection features
- 2: Return address signing to its standard level
- 3: Extend the signing to include leaf functions
The table below summarizes ``BRANCH_PROTECTION`` values, GCC compilation options
and resulting PAuth/BTIhttps://tegra-sw-opengrok.nvidia.com/source/s?path=PAuth/BTI&project=stage-main_automotive features.
+-------+--------------+-------+-----+
| Value | GCC option | PAuth | BTI |
+=======+==============+=======+=====+
| 0 | none | N | N |
+-------+--------------+-------+-----+
| 1 | standard | Y | Y |
+-------+--------------+-------+-----+
| 2 | pac-ret | Y | N |
+-------+--------------+-------+-----+
| 3 | pac-ret+leaf | Y | N |
+-------+--------------+-------+-----+
This option 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 option if the CPU supports it. <snip>
Thanks, Varun
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