Re: [RFC] <sys/tagged-address.h>: An API for tagged address

[Florian Weimer <fweimer@redhat.com>]

* H. J. Lu via Libc-alpha:

> On Thu, Feb 11, 2021 at 12:28 PM Joseph Myers <joseph@codesourcery.com> wrote:
>>
>> On Thu, 11 Feb 2021, H.J. Lu via Libc-alpha wrote:
>>
>> > An API for tagged address:
>>
>> Please write a longer commit message, discussing what "tagged address" is,
>> which architectures have such a thing (the API should try to cover
>> whatever is common between architectures as far as possible - is this
>> meant to relate to AArch64 MTE, how does it relate to the MTE code we
>
> This API is for Intel LAM:
>
> https://www.phoronix.com/scan.php?page=news_item&px=Intel-LAM-Glibc#:~:text=Intel%20Linear%20Address%20Masking%20(LAM,bit%20linear%20addresses%20for%20metadata.&text=With%20LAM%20enabled%2C%20the%20processor,linear%20address%20to%20access%20memory.
>
> and ARM TBI:
>
> https://en.wikichip.org/wiki/arm/tbi

Do the setters/getters change process or thread properties?

The interface assumes that the tag bits are uniform across pointer
types.  I think that's not true, at least from a historical perspective.

People complained that our protection key interfaces are too slow to be
useful.  Do we need to find a way to inline the tag/untag operations?

Thanks,
Florian
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