Re: [PATCH v2 2/4] arm64/ptrace: Document extension of NT_ARM_TLS to cover TPIDR2_EL0

[Luis Machado <luis.machado@arm.com>]

On 8/15/22 14:30, Mark Brown wrote:
> In order to allow debuggers to discover lazily saved SME state we need
> to provide access to TPIDR2_EL0, we will extend the existing NT_ARM_TLS
> used for TPIDR to also include TPIDR2_EL0 as the second register in the
> regset.
> 
> Signed-off-by: Mark Brown <broonie@kernel.org>
> ---
>   Documentation/arm64/sme.rst | 3 +++
>   1 file changed, 3 insertions(+)
> 
> diff --git a/Documentation/arm64/sme.rst b/Documentation/arm64/sme.rst
> index 937147f58cc5..16d2db4c2e2e 100644
> --- a/Documentation/arm64/sme.rst
> +++ b/Documentation/arm64/sme.rst
> @@ -331,6 +331,9 @@ The regset data starts with struct user_za_header, containing:
>     been read if a PTRACE_GETREGSET of NT_ARM_ZA were executed for each thread
>     when the coredump was generated.
>   
> +* The NT_ARM_TLS note will be extended to two registers, the second register
> +  will contain TPIDR2_EL0 on systems that support SME and will be read as
> +  zero with writes ignored otherwise.
>   
>   9.  System runtime configuration
>   --------------------------------

I wonder if we should document a bit more about the use of TPIDR2, its states, values and
block format when TPIDR2 points to valid ZA state.

Would that make sense?