Date: Mon, 11 Feb 2008 21:10:20 -0800 From: Alfred Perlstein <alfred@freebsd.org> To: "Christian S.J. Peron" <csjp@FreeBSD.org> Cc: arch@freebsd.org, re@freebsd.org, current@freebsd.org Subject: Re: sysv IPC and shminfo ABI Message-ID: <20080212051020.GO99258@elvis.mu.org> In-Reply-To: <20080212014057.GA6027@sub.vaned.net> References: <20080212014057.GA6027@sub.vaned.net>
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* Christian S.J. Peron <csjp@FreeBSD.org> [080211 18:00] wrote: > All, > > A while ago, I committed a patch which changed what was a kernel private > structure 'shminfo'. In order to access this structure, you must define > _KERNEL which suggests to me we should not be making guarantees about it's > size. > > See /usr/src/sys/shm.h ... yeah but... > > So I guess I have a few questions: > > (1) Is struct shminfo considered a sys V standard structure that has a > predefined size that should be maintained across all architectures? No, that's not required, what is required is backwards compat. > (2) Is this an ABI breakage that we care about? Yes, if it's breaking people, then yes. for ia32 in particular. > (1) Back the change out now before any damage is done (assuming we care) > > (2) Apply this safety patch to RELENG_7 and RELENG_7_0 > > http://people.freebsd.org/~csjp/sysv_shm.1202744975.6_abi_fix.diff Honestly I was going to suggest all this cruft to "get it right", but this patch looks like the most simple, most correct thing. I think it should go in. > (3) Leave things as they are, as we are going to be getting support for large > shared memory allocations in the future. (This is why I asked if the > structure supposed to be a standard size). Afaik there's no "standard size" in the API (I think shmctl->shminfo is pretty unix specific) but it pays to keep the backward compat. > > I apologize for this, I understand this is probably the last thing we need > before the release, but I just want to make sure that we are doing the right > thing. Cool. -Alfred
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