Messages in this thread | | | Date | Mon, 17 Dec 2012 22:56:12 +0400 | From | Pavel Emelyanov <> | Subject | Re: [CRIU] [PATCH] Add VDSO time function support for x86 32-bit kernel |
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On 12/17/2012 07:21 PM, H. Peter Anvin wrote: > Because it is almost impossible to do right?
In the generic case -- I tend to agree. But it's possible to describe how a library should communicate to crtools to make it possible.
Anyway, what I wanted to say -- we didn't have this scenario in our plans, but criu project is open, and if someone comes with sane idea, we will not object merging it.
> 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 >
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