Messages in this thread | | | Subject | Re: [CRIU] [PATCH] Add VDSO time function support for x86 32-bit kernel | From | "H. Peter Anvin" <> | Date | Mon, 17 Dec 2012 07:21:45 -0800 |
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Because it is almost impossible to do right?
Pavel Emelyanov <xemul@parallels.com> wrote:
>On 12/14/2012 10:44 PM, Andy Lutomirski wrote: >> On Fri, Dec 14, 2012 at 10:35 AM, H. Peter Anvin <hpa@zytor.com> >wrote: >>> On 12/14/2012 12:34 AM, Pavel Emelyanov wrote: >>>> On 12/14/2012 06:20 AM, Andy Lutomirski wrote: >>>>> On Thu, Dec 13, 2012 at 6:18 PM, H. Peter Anvin <hpa@zytor.com> >wrote: >>>>>> Wouldn't the vdso get mapped already and could be mremap()'d. If >we >>>>> really need more control I'd almost push for a device/filesystem >node >>>>> that could be mmapped the usual way. >>>>> >>>>> Hmm. That may work, but it'll still break ABI. I'm not sure that >>>>> criu is stable enough yet that we should care. Criu people? >>>> >>>> It's not yet, but we'd still appreciate the criu-friendly vdso >redesign. >>>> >>>>> (In brief summary: how annoying would it be if the vdso was no >longer >>>>> just a bunch of constant bytes that lived somewhere?) >>>> >>>> It depends on what vdso is going to be. In the perfect case it >should >>>> a) be mremap-able to any address (or be at fixed address _forever_, >but >>>> I assume this is not feasible); >>>> b) have entry points at fixed (or somehow movable) places. >>>> >>>> I admit that I didn't understand your question properly, if I did, >>>> please correct me. >>>> >>> >>> mremap() should work. At the same time, the code itself is not >going to >>> have any stability guarantees between kernel versions -- it >obviously >>> cannot. >> >> We could guarantee that the symbols in the vdso resolve to particular >> offsets within the vdso. (Yes, this is ugly.) >> >> Does criu support checkpointing with one version of a shared library >> and restoring with another? > >No, neither we have this in plans. >However, if somebody needs this and implements -- why not?! > >Thanks, >Pavel
-- Sent from my mobile phone. Please excuse brevity and lack of formatting.
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