Re: [RFC PATCH 2/5] gdbserver/aarch64: Enable FPMR for AArch64 in gdbserver on Linux

[Luis <luis.machado.foss@gmail.com>]

On 05/09/2025 14:17, Ezra.Sitorus@arm.com wrote:
> From: Ezra Sitorus <ezra.sitorus@arm.com>
> 
> Support FPMR in gdbserver.
> 
> Manually validated under Shrinkwrap (Arm FVP).
> ---
>   gdbserver/linux-aarch64-low.cc | 29 +++++++++++++++++++++++++++++
>   1 file changed, 29 insertions(+)
> 
> diff --git a/gdbserver/linux-aarch64-low.cc b/gdbserver/linux-aarch64-low.cc
> index 9d3ac803e7b..e15280c3681 100644
> --- a/gdbserver/linux-aarch64-low.cc
> +++ b/gdbserver/linux-aarch64-low.cc
> @@ -248,6 +248,26 @@ aarch64_store_fpregset (struct regcache *regcache, const void *buf)
>     supply_register (regcache, AARCH64_FPCR_REGNUM, &regset->fpcr);
>   }
>   
> +/* Fill BUF with the FPMR from the regcache.  */

s/FPMR/FPMR register"

> +
> +static void
> +aarch64_fill_fpmr_regset (struct regcache *regcache, void *buf)
> +{
> +  uint64_t *fpmr = (uint64_t *) buf;
> +  int fpmr_regnum = find_regno (regcache->tdesc, "fpmr");
> +  collect_register (regcache, fpmr_regnum, fpmr);
> +}
> +
> +/* Store the FPMR to regcache.  */

s/FPMR/FPMR register

> +
> +static void
> +aarch64_store_fpmr_regset (struct regcache *regcache, const void *buf)
> +{
> +  uint64_t *fpmr = (uint64_t *) buf;
> +  int fpmr_regnum = find_regno (regcache->tdesc, "fpmr");
> +  supply_register (regcache, fpmr_regnum, fpmr);
> +}
> +
>   /* Store the pauth registers to regcache.  */
>   
>   static void
> @@ -879,6 +899,10 @@ static struct regset_info aarch64_regsets[] =
>     { PTRACE_GETREGSET, PTRACE_SETREGSET, NT_ARM_TAGGED_ADDR_CTRL,
>       0, OPTIONAL_REGS,
>       aarch64_fill_mteregset, aarch64_store_mteregset },
> +  /* Floating Point Mode Register (FPMR).  */
> +  { PTRACE_GETREGSET, PTRACE_SETREGSET, NT_ARM_FPMR,
> +    0, OPTIONAL_REGS,
> +    aarch64_fill_fpmr_regset, aarch64_store_fpmr_regset },
>     /* TLS register.  */
>     { PTRACE_GETREGSET, PTRACE_SETREGSET, NT_ARM_TLS,
>       0, OPTIONAL_REGS,
> @@ -954,6 +978,10 @@ aarch64_adjust_register_sets (const struct aarch64_features &features)
>   	  if (features.gcs_linux)
>   	    regset->size = sizeof (user_gcs);
>   	  break;
> +	case NT_ARM_FPMR:
> +	  if (features.fpmr)
> +	    regset->size = sizeof (uint64_t);
> +	  break;
>   	default:
>   	  gdb_assert_not_reached ("Unknown register set found.");
>   	}
> @@ -986,6 +1014,7 @@ aarch64_target::low_arch_setup ()
>         features.mte = linux_get_hwcap2 (pid, 8) & HWCAP2_MTE;
>         features.tls = aarch64_tls_register_count (tid);
>         features.gcs = features.gcs_linux = linux_get_hwcap (pid, 8) & HWCAP_GCS;
> +      features.fpmr = linux_get_hwcap2 (pid, 8) & (1UL << 48);

s/1UL/1ULL

>   
>         /* Scalable Matrix Extension feature and size check.  */
>         if (linux_get_hwcap2 (pid, 8) & HWCAP2_SME)