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Miller" , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , Chris Zankel , Max Filippov Subject: Re: [RFC PATCH] UAPI: Document auxvec AT_* namespace policy and note reservations In-Reply-To: <1526480447-18185-1-git-send-email-Dave.Martin@arm.com> References: <1526480447-18185-1-git-send-email-Dave.Martin@arm.com> Date: Thu, 17 May 2018 16:40:19 +1000 Message-ID: <8736yqokdo.fsf@concordia.ellerman.id.au> MIME-Version: 1.0 Content-Type: text/plain Sender: linux-api-owner@vger.kernel.org X-Mailing-List: linux-api@vger.kernel.org X-getmail-retrieved-from-mailbox: INBOX X-Mailing-List: linux-kernel@vger.kernel.org List-ID: Dave Martin writes: > There are constraints on defining AT_* auxvec tags that are not > obvious to the casual maintainer of either the global > 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. > 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