Re: [PATCH] [AArch64] Add TPIDR2 register support for Linux

[John Baldwin <jhb@FreeBSD.org>]

On 9/23/22 6:46 AM, Luis Machado wrote:
> With the AArch64 Scalable Matrix Extension we have a new TPIDR2 register, and
> it will be added to the existing NT_ARM_TLS register set. Kernel patches are
> being reviewed here:
> 
> https://lore.kernel.org/linux-arm-kernel/20220818170111.351889-1-broonie@kernel.org/
> 
>  From GDB's perspective, we handle it in a similar way to the existing TPIDR
> register. But we need to consider cases of systems that only have TPIDR and
> systems that have both TPIDR and TPIDR2.
> 
> With that in mind, the following patch adds the required code to support
> TPIDR2 and turns the org.gnu.gdb.aarch64.tls feature into a
> dynamically-generated target description as opposed to a static target
> description containing only TPIDR.
> 
> That means we can remove the gdb/features/aarch64-tls.xml file and replace the
> existing gdb/features/aarch64-tls.c auto-generated file with a new file that
> dynamically generates the target description containing either TPIDR alone or
> TPIDR and TPIDR2.
> 
> In the future, when *BSD's start to support this register, they can just
> enable it as is being done for the AArch64 Linux target.
> 
> The core file read/write code has been updated to support TPIDR2 as well.
> 
> On GDBserver's side, there is a small change to the find_regno function to
> expose a non-throwing version of it.
> 
> It always seemed strange to me how find_regno causes the whole operation to
> abort if it doesn't find a particular register name. The patch moves code
> from find_regno into find_regno_no_throw and makes find_regno call
> find_regno_no_throw instead.
> 
> This allows us to do register name lookups to find a particular register
> number without risking erroring out if nothing is found.
> 
> The patch also adjusts the feature detection code for aarch64-fbsd, since
> the infrastructure is shared amongst all aarch64 targets. I haven't added
> code to support TPIDR2 in aarch64-fbsd though, as I'm not sure when/if
> that will happen.

The fbsd bits look fine to me.

-- 
John Baldwin