Messages in this thread | | | Date | Sun, 4 Apr 2021 22:03:37 -0700 | From | Andrei Vagin <> | Subject | Re: [PATCH RESEND v1 3/4] powerpc/vdso: Separate vvar vma from vdso |
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On Wed, Mar 31, 2021 at 04:48:46PM +0000, Christophe Leroy wrote: > From: Dmitry Safonov <dima@arista.com> > > Since commit 511157ab641e ("powerpc/vdso: Move vdso datapage up front") > VVAR page is in front of the VDSO area. In result it breaks CRIU > (Checkpoint Restore In Userspace) [1], where CRIU expects that "[vdso]" > from /proc/../maps points at ELF/vdso image, rather than at VVAR data page. > Laurent made a patch to keep CRIU working (by reading aux vector). > But I think it still makes sence to separate two mappings into different > VMAs. It will also make ppc64 less "special" for userspace and as > a side-bonus will make VVAR page un-writable by debugger (which previously > would COW page and can be unexpected). > > I opportunistically Cc stable on it: I understand that usually such > stuff isn't a stable material, but that will allow us in CRIU have > one workaround less that is needed just for one release (v5.11) on > one platform (ppc64), which we otherwise have to maintain. > I wouldn't go as far as to say that the commit 511157ab641e is ABI > regression as no other userspace got broken, but I'd really appreciate > if it gets backported to v5.11 after v5.12 is released, so as not > to complicate already non-simple CRIU-vdso code. Thanks! > > Cc: Andrei Vagin <avagin@gmail.com>
Acked-by: Andrei Vagin <avagin@gmail.com>
> Cc: Andy Lutomirski <luto@kernel.org> > Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> > Cc: Christophe Leroy <christophe.leroy@csgroup.eu> > Cc: Laurent Dufour <ldufour@linux.ibm.com> > Cc: Michael Ellerman <mpe@ellerman.id.au> > Cc: Paul Mackerras <paulus@samba.org> > Cc: linuxppc-dev@lists.ozlabs.org > Cc: stable@vger.kernel.org # v5.11 > [1]: https://github.com/checkpoint-restore/criu/issues/1417 > Signed-off-by: Dmitry Safonov <dima@arista.com> > Tested-by: Christophe Leroy <christophe.leroy@csgroup.eu> > Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
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