Re: [PATCH] [AArch64] Fix pseudo-register numbering in the presence of unexpected additional registers

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

On 9/21/22 18:53, Luis Machado via Gdb-patches wrote:
> When using AArch64 GDB with the QEMU debugging stub (in user mode), we get
> additional system registers that GDB doesn't particularly care about, so
> it doesn't number those explicitly.
> 
> But given the pseudo-register numbers are above the number of real registers,
> we need to setup/account for the real registers first before going ahead and
> numbering the pseudo-registers.  This has to happen at the end of
> aarch64_gdbarch_init, after the call to tdesc_use_registers, as that
> updates the total number of real registers.
> 
> This is in preparation to supporting pointer authentication for bare metal
> aarch64 (QEMU).
> ---
>   gdb/aarch64-tdep.c | 15 +++++++++++++--
>   1 file changed, 13 insertions(+), 2 deletions(-)
> 
> diff --git a/gdb/aarch64-tdep.c b/gdb/aarch64-tdep.c
> index 7229b53838e..f94e810f904 100644
> --- a/gdb/aarch64-tdep.c
> +++ b/gdb/aarch64-tdep.c
> @@ -3598,8 +3598,7 @@ aarch64_gdbarch_init (struct gdbarch_info info, struct gdbarch_list *arches)
>     tdep->jb_elt_size = 8;
>     tdep->vq = vq;
>     tdep->pauth_reg_base = first_pauth_regnum;
> -  tdep->ra_sign_state_regnum = (feature_pauth == NULL) ? -1
> -				: ra_sign_state_offset + num_regs;
> +  tdep->ra_sign_state_regnum = -1;
>     tdep->mte_reg_base = first_mte_regnum;
>     tdep->tls_regnum = tls_regnum;
>   
> @@ -3698,6 +3697,18 @@ aarch64_gdbarch_init (struct gdbarch_info info, struct gdbarch_list *arches)
>   
>     tdesc_use_registers (gdbarch, tdesc, std::move (tdesc_data));
>   
> +  /* Fetch the updated number of registers after we're done adding all
> +     entries from features we don't explicitly care about.  This is the case
> +     for bare metal debugging stubs that include a lot of system registers.  */
> +  num_regs = gdbarch_num_regs (gdbarch);
> +
> +  /* With the number of real registers updated, setup the pseudo-registers and
> +     record their numbers.  */
> +
> +  /* Pointer authentication pseudo-registers.  */
> +  if (tdep->has_pauth ())
> +    tdep->ra_sign_state_regnum = ra_sign_state_offset + num_regs;
> +
>     /* Add standard register aliases.  */
>     for (i = 0; i < ARRAY_SIZE (aarch64_register_aliases); i++)
>       user_reg_add (gdbarch, aarch64_register_aliases[i].name,

Pushed now.