Re: [PATCH 3/3] c/r: define s390-specific checkpoint-restart code (v6)

["Serge E. Hallyn" <serue-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>]

Quoting Nathan Lynch (ntl-e+AXbWqSrlAAvxtiuMwx3w@public.gmane.org):
> > +#if 0
> > +	/* Oren's v13 is on an older kernel which has no vdso_base
> > +	 * on newer kernel, we'll have to enable this
> > +	 */
> > +	CR_COPY(op, hh->vdso_base, mm->context.vdso_base);
> > +#endif
> 
> During restart, does this replace the current task's VDSO contents, and
> if so, is that wise?  VDSO areas contain things like timestamps for
> gettimeofday()...

(I've gone back and forth on this, and the following answer differs
from any interpretation i've had before :)

Well, arch_setup_additional_pages() uses get_unmapped_area() to get
a user mapping for the vdso pages.  So i would expect that in fact
the arch-independent code would set up a new vdso mapping at the
checkpointed location, and so mm->context.vdso_base does in fact
need to be changed.

But it's something to verify when we port the code to a newer
kernel.

-serge