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

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

Hi,

On 10/3/22 14:16, Luis Machado wrote:
> 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.

I'd like to push this patch to both gdb 12 and gdb 11. Does that sound reasonable?