[PATCH 2/2] malloc: change tunable glibc.mem.tagging to glibc.mem.aarch64_mte

[Yury Khrustalev]

Hello Sunil,

On Thu, Mar 26, 2026 at 10:22:36AM -0700, Sunil Pandey wrote:
> On Thu, Mar 26, 2026 at 2:32 AM Yury Khrustalev <yury.khrustalev@arm.com>
> wrote:
>
> ...
>
> > We're going to have aarch64 tunable for memory tagging with
> > MTE-specific values. I don't mind keeping the existing generic
> > tunable 'glibc.mem.tagging', however it would be ignored on
> > aarch64, and I just thought it would be confusing to have it
> > since it's not used anywhere else.
> >
> My concerns are related to changes in architecture independent files.

I understand your concerns and I agree that this is not ideal that some
target-dependent elements are included in the code that is supposed to
be generic.

However, this existed before my patch, I've only made it explicit by
changing the name of the macro. If you insist, I could keep the generic
name for this macro, but it would only hide the issue, not solve it.

We should probably use sysdeps files for such arch-dependent things,
however this would be one of the next steps.

> 
> Most guarded variables are useful across architecture, keeping generic
> names will reduce code
>  duplication for other architecture.

Agreed, but one step at a time.

> 
> Another comment, if you look into this call in malloc.c and whether it can
> be replaced
> 
> From
> 
> return __libc_mtag_tag_zero_region (__libc_mtag_new_tag (ptr), size);
> 
> To
> 
> return __libc_mtag_tag_zero_region (ptr, size);
> 
> Avoiding function call in parameter.

This is good point, but it's out of scope of this patch. I'll keep this
in mind for the future.

Thanks,
Yury