Re: [PATCH v1] gdb/linux: add helpers to read AT_HWCAP3 and AT_HWCAP4

[Matthieu Longo <matthieu.longo@arm.com>]

On 20/08/2026 15:29, Simon Marchi wrote:
> On 7/27/26 1:28 PM, Matthieu Longo wrote:
>> Add linux_get_hwcap3 and linux_get_hwcap4 helpers to GDB and gdbserver,
>> mirroring the existing linux_get_hwcap and linux_get_hwcap2 interfaces.
>>
>> The new helpers retrieve the AT_HWCAP3 and AT_HWCAP4 auxiliary vector
>> entry either from explicitly supplied auxv data or from the current
>> inferior.
>>
>> This prepares for future features that depend on HWCAP3 and HWCAP4
>> capability bits.
>>
>> Reviewed-by: Thiago Jung Bauermann <thiago.bauermann@linaro.org>
> 
> LGTM
> 
> Approved-By: Simon Marchi <simon.marchi@efficios.com>
> 

Thanks !

> But one question that picked my curiosity:
> 
>> diff --git a/gdbserver/linux-low.cc b/gdbserver/linux-low.cc
>> index f1be62225e2..c4daba0bf40 100644
>> --- a/gdbserver/linux-low.cc
>> +++ b/gdbserver/linux-low.cc
>> @@ -70,6 +70,14 @@
>>  #define AT_HWCAP2 26
>>  #endif
>>  
>> +#ifndef AT_HWCAP3
>> +#define AT_HWCAP3 29
>> +#endif
>> +
>> +#ifndef AT_HWCAP4
>> +#define AT_HWCAP4 30
>> +#endif
> 
> How come we need to provide these values in gdbserver, but not in the
> equivalent native part of gdb?
> 
> Simon

Those values had already been added in elf/common.h by this patch:
https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=0c90306549b02dd2b07fe3f2639ab3ac75a29558

Matthieu