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

[H.J. Lu]

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

> already have in glibc, what corresponding features are involved on other

ARM MTE is built on top of TBI.   My <sys/tagged-address.h> supports
LAM and TBI.  It can be used to:

1. Enable LAM/TBI.
2. Make mommove LAM/TBI compatible.
3. Enable LAM in HWASAN.

> architectures?) and what the API is intended to be useful for.  A new API
> also needs additions to the manual and NEWS - again, explaining things at
> the user level.
>
> The header naming suggests installed headers, but you don't appear to be
> installing them.

I will install them in the final version.  The complete LAM patch set is on
users/intel/lam/master branch at

https://gitlab.com/x86-glibc/glibc/-/tree/users/intel/lam/master

> I don't see anything architecture-specific about the build logic, so I'd
> expect all libc.abilist files to have the new functions rather than just a
> few.

The final version will update all libc.abilist files.

Thanks.

-- 
H.J.