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Add ACLE macros for FEAT_PAuth_LR
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The Armv9.5a introduces the FEAT_PAuth_LR extension, adding an enhancement
to the Pointer Authentication extension where the value of PC is used as
a diversifier when signing pointers.

This updates the ACLE to support the extension by the introduction of a
new feature marcro and the addition of a new possible value to the
existing `__ARM_FEATURE_PAC_DEFAULT` macro.
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@pratlucas
pratlucas committed Jan 24, 2024
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26 changes: 19 additions & 7 deletions main/acle.md
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Expand Up @@ -362,6 +362,11 @@ Armv8.4-A [[ARMARMv84]](#ARMARMv84). Support is added for the Dot Product intrin
* Added description of SVE reinterpret intrinsics.
* Changes for [Function Multi Versioning](#function-multi-versioning):
* Added [MOPS](#memcpy-family-of-operations-intrinsics---mops).
* Introduced the `__ARM_FEATURE_PAUTH_LR` feature macro in section
[Pointer Authentication](#pointer-authentication) to indicate target support
for the Armv9.5a's PAC Enhancements.
* Introduced a new value to the `__ARM_FEATURE_PAC_DEFAULT` macro to indicate
the use of PC as a diversifier for [Pointer Authentication](#pointer-authentication).

### References

Expand Down Expand Up @@ -1570,11 +1575,12 @@ Pointer Authentication extension to protect code against code reuse attacks
by default.
The bits are defined as follows:

| **Bit** | **Meaning** |
| ------- | ----------------------------------- |
| 0 | Protection using the A key |
| 1 | Protection using the B key |
| 2 | Protection including leaf functions |
| **Bit** | **Meaning** |
| ------- | ------------------------------------ |
| 0 | Protection using the A key |
| 1 | Protection using the B key |
| 2 | Protection including leaf functions |
| 3 | Protection using PC as a diversifier |

For example, a value of `0x5` indicates that the Pointer Authentication
extension is used to protect function entry points, including leaf functions,
Expand All @@ -1583,7 +1589,11 @@ The protection applied to any particular function may be overridden by
mechanisms such as function attributes.

`__ARM_FEATURE_PAUTH` is defined to 1 if Pointer Authentication extension
is available on the target. It is undefined otherwise.
(FEAT_PAuth) is available on the target. It is undefined otherwise.

`__ARM_FEATURE_PAUTH_LR` is defined to 1 if Armv9.5a enhancements to the
Pointer Authentication extension (FEAT_PAuth_LR) are available on the target.
It is undefined otherwise.

### Large System Extensions

Expand Down Expand Up @@ -2284,7 +2294,9 @@ be found in [[BA]](#BA).
| [`__ARM_FEATURE_MOPS`](#memcpy-family-of-memory-operations-standarization-instructions---mops) | `memcpy`, `memset`, and `memmove` family of operations standardization instructions | 1 |
| [`__ARM_FEATURE_MVE`](#m-profile-vector-extension) | M-profile Vector Extension | 1 |
| [`__ARM_FEATURE_NUMERIC_MAXMIN`](#numeric-maximum-and-minimum) | Numeric Maximum and Minimum | 1 |
| [`__ARM_FEATURE_PAC_DEFAULT`](#pointer-authentication) | Pointer authentication | 0x5 |
| [`__ARM_FEATURE_PAC_DEFAULT`](#pointer-authentication) | Pointer authentication protection | 0x5 |
| [`__ARM_FEATURE_PAUTH`](#pointer-authentication) | Pointer Authentication Extension (FEAT_PAuth) | 1 |
| [`__ARM_FEATURE_PAUTH_LR`](#pointer-authentication) | Armv9.5a Enhancements to Pointer Authentication Extension (FEAT_PAuth_LR) | 1 |
| [`__ARM_FEATURE_QBIT`](#q-saturation-flag) | Q (saturation) flag (32-bit-only) | 1 |
| [`__ARM_FEATURE_QRDMX`](#rounding-doubling-multiplies) | SQRDMLxH instructions and associated intrinsics availability | 1 |
| [`__ARM_FEATURE_RCPC`](#rcpc) | Release Consistent processor consistent Model (64-bit-only) | 1 |
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