[lkml]   [2011]   [Oct]   [21]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
    SubjectRe: [patch 5/5] elf: Add support for loading ET_CKPT files

    On Wed, Oct 19, 2011 at 11:56:32PM +0400, Cyrill Gorcunov wrote:
    > > I find that quite difficult to agree with. We're talking about some
    > > minor additions to prctl against updating exec path to do something it
    > > was never designed to do + new binary format.
    > Tejun, regardless the mm_struct entries, what about mapping vdso pages at the
    > place they had on snapshot time? How would we handle them?

    We discussed this elsewhere but just for the record.

    I haven't really looked into vdso but what the currently suggested
    implementation isn't correct. vdso is there so that kernel can
    provide userspace code which may vary depending on kernel version and
    the actual machine it's running on, so both saving vdso and restoring
    verbatim and asking the kernel to map its vdso at certain address are

    The checkpointer would need to remember the vdso symtab from the
    original process and then somehow build indirect jump table at the
    same address which redirects to the vdso of the machine the target
    process is being restored on. I'm not sure about the details of the
    implementation but it could be something like "please allow me to
    write to this original vdso address and keep your vdso elsewhere".

    I think this comes back to why one-stop-solution-in-kernel is a bad
    idea for CR. My impression is that when people say "that would
    require too many small API updatesa", it usually means that they
    haven't really thought about each necessary piece enough and just
    hacked something up lumpy and fuzzy on the edges. The thing is that
    no matter how you lump them, those problems don't go away and
    attacking things in small understandable API pieces not only ensures
    the update itself makes sense and may be useful for others too but
    also forces people to actually think about each problem.

    Thank you.


     \ /
      Last update: 2011-10-21 20:29    [W:0.022 / U:0.056 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site