From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Serge E. Hallyn" Subject: Re: [PATCH 1/1] cr: remap vdso at original address Date: Mon, 30 Mar 2009 17:58:44 -0500 Message-ID: <20090330225844.GA1143@us.ibm.com> References: <20090325143116.GA14040@us.ibm.com> <49D0C977.8060807@cs.columbia.edu> <20090330145054.GA23411@us.ibm.com> <49D0DF07.7030604@cs.columbia.edu> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <49D0DF07.7030604-eQaUEPhvms7ENvBUuze7eA@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: containers-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org Errors-To: containers-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org To: Oren Laadan Cc: Linux Containers List-Id: containers.vger.kernel.org Quoting Oren Laadan (orenl-eQaUEPhvms7ENvBUuze7eA@public.gmane.org): > Actually, I think that the get_gate_vma() is broken with randomized vdso > in the main kernel - it simply won't work just like remapping won't work :) > It simply didn't show up so far either because no-one is using it, or the > function is not really important ? I'm not so sure. It appears to be just an optimization for the compat vdso mode. Well, so long as VDSO_HIGH_BASE isn't a legitimate address for a user mapping when not in compat vdso mode, which seems reasonable (0xffffe000U)? So if not in compat vdso mode, then you don't use gate_vma, but notice that powerpc for instance always returns 0 for in_gate_area() and NULL for get_gate_vma(). > Who would be the right person to report this issue ? Well git-blame suggests that the main people touching that code have been Ingo and Jeremy. > > But so for now I'm definately withdrawing this patch. In the meantime, > > do we prefer requiring COMPAT_VDSO (using config logic?), or do we > > prefer resetting the context.vdso on x86 at restart? > > I fear that if we require that, then we forget to un-require it later ... Nonsense, if people care about it they'll yell. > Another thing that we should do it transder the vdso page (one copy of > each page) from the checkpoint and compare to the version available at > the restart. Yell if differs. As Matt points out, we'd need an arch-specific comparison function which ignores the data page. > (vdso page pointer will be treated as a shared resource - so only copied > once). That seems beneficial at least. thanks, -serge