Re: [RFC PATCH] UAPI: Document auxvec AT_* namespace policy and note reservations

[Michael Ellerman]

Dave Martin <Dave.Martin@xxxxxxx> writes:

> There are constraints on defining AT_* auxvec tags that are not
> obvious to the casual maintainer of either the global
> <uapi/linux/auxvec.h> or the arch-specific headers.  This is likely
> to lead to mistakes.  (I certainly fell foul of it...)

Thanks for cleaning this up.

It looks like us (powerpc) / me is the main offender here.

My excuse is it was glibc folk who asked us to add all those new AT_
entries in the first place. </buckpassing>

> For the benefit of future maintainers, this patch collects the
> relevant information in one place, documenting how the namespace
> needs to be managed, and noting all the values currently in use.
>
> Maintaining a global list may result in some merge conflicts, but
> AT_* values are not added frequently.  I'm open to suggestions on
> the best approach.

Yeah I agree with Rich that having a global list would be best. That is
the most reliable to make people think twice about adding new entries.

> I also assume that values 38 and 39 may have been used for
> historical purposes, such as an architecture that is no longer
> supported.  If they have definitely never been used for anything,
> they could be removed from the "reserved" list.

I don't know why we added the new entries starting at 40, maybe Ben
remembers. Quite likely it was just an accident.

I don't see any sign of 38 or 39 in glibc history.

cheers