On Thu, May 18, 2017 at 02:13:29PM +0300, Dmitry Safonov wrote:
> On 04/25/2017 08:18 PM, Dmitry Safonov wrote:
> >On 04/14/2017 04:25 PM, Dmitry Safonov wrote:
> >>CRIU restores application mappings on the same place where they
> >>were before Checkpoint. That means, that we need to move vDSO
> >>and sigpage during restore on exactly the same place where
> >>they were before C/R.
> >>
> >>Make mremap() code update mm->context.{sigpage,vdso} pointers
> >>during VMA move. Sigpage is used for landing after handling
> >>a signal - if the pointer is not updated during moving, the
> >>application might crash on any signal after mremap().
> >>
> >>vDSO pointer on ARM32 is used only for setting auxv at this moment,
> >>update it during mremap() in case of future usage.
> >>
> >>Without those updates, current work of CRIU on ARM32 is not reliable.
> >>Historically, we error Checkpointing if we find vDSO page on ARM32
> >>and suggest user to disable CONFIG_VDSO.
> >>But that's not correct - it goes from x86 where signal processing
> >>is ended in vDSO blob. For arm32 it's sigpage, which is not disabled
> >>with `CONFIG_VDSO=n'.
> >>
> >>Looks like C/R was working by luck - because userspace on ARM32 at
> >>this moment always sets SA_RESTORER.
> >>
> >>Cc: linux-arm-ker...@lists.infradead.org
> >>Cc: Russell King <li...@armlinux.org.uk>
> >>Cc: Will Deacon <will.dea...@arm.com>
> >>Cc: Andy Lutomirski <l...@amacapital.net>
> >>Cc: Thomas Gleixner <t...@linutronix.de>
> >>Cc: Cyrill Gorcunov <gorcu...@openvz.org>
> >>Cc: Pavel Emelyanov <xe...@virtuozzo.com>
> >>Cc: Christopher Covington <c...@codeaurora.org>
> >>Signed-off-by: Dmitry Safonov <dsafo...@virtuozzo.com>
> >>---
> >>v2: (buildbot) Fix (unsinged long) to (void*) cast warning.
> >>
> >> arch/arm/kernel/process.c | 8 ++++++++
> >> arch/arm/kernel/vdso.c | 18 ++++++++++++++++++
> >> arch/x86/entry/vdso/vma.c | 3 ---
> >> mm/mmap.c | 4 ++++
> >> 4 files changed, 30 insertions(+), 3 deletions(-)
> >
> >Ping?
>
> Ping?
I'm mostly happy with the ARM bits, but I can't take the patch without
acks from others because it touches other architectures/generic code.
--
RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up
according to speedtest.net.
