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Re: [PATCH][aarch64] Fix hpwcap argument passed to ifunc resolvers

On 08/31/2017 11:12 AM, Steve Ellcey wrote:
> On Thu, 2017-08-31 at 16:19 +0100, Szabolcs Nagy wrote:
>> i'm not yet convinced that LD_HWCAP_MASK should be
>> applied to ifunc resolvers: glibc might be interested
>> in different hwcap flags than external users and the
>> important hwcaps mask has other effect in glibc that
>> i need to review.
> Personally, I like the idea that LD_HWCAP_MASK can affect ifunc
> resolvers.  It gives users a single method to turn off some hardware
> capability across all libraries.  I can see where finer grain control
> might also be useful but I think that in general we are going to have
> situations where a particular hardware capability is just not working
> the way it should and so we want to turn off its use everywhere in an
> executable.

I agree with Szabolcs.

The use of LD_HWCAP_MASK is a bit of mess in glibc.


* We have one LD_HWCAP_MASK, but two HWCAPs e.g. AT_HWCAP, AT_HWCAP2.

* LD_HWCAP_MASK is used for multiple things:

  * As a filter for results.

  * As a filter for multilib directory selection.

* We already have sysdeps/aarch64/dl-tunables.list to select

I'd just use the tunables.


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