Hi,

On 03/20/2015 11:53 AM, Laurent Dufour wrote:

CRIU is recreating the process memory layout by remapping the checkpointee
memory area on top of the current process (criu). This includes remapping
the vDSO to the place it has at checkpoint time.

However some architectures like powerpc are keeping a reference to the vDSO
base address to build the signal return stack frame by calling the vDSO
sigreturn service. So once the vDSO has been moved, this reference is no
more valid and the signal frame built later are not usable.

This patch serie is introducing a new mm hook 'arch_remap' which is called
when mremap is done and the mm lock still hold. The next patch is adding the
vDSO remap and unmap tracking to the powerpc architecture.

Laurent Dufour (2):
  mm: Introducing arch_remap hook
  powerpc/mm: Tracking vDSO remap

 arch/powerpc/include/asm/mmu_context.h   | 35 +++++++++++++++++++++++++++++++-
 arch/s390/include/asm/mmu_context.h      |  6 ++++++
 arch/um/include/asm/mmu_context.h        |  5 +++++
 arch/unicore32/include/asm/mmu_context.h |  6 ++++++
 arch/x86/include/asm/mmu_context.h       |  6 ++++++
 include/asm-generic/mm_hooks.h           |  6 ++++++
 mm/mremap.c                              |  9 ++++++--
 7 files changed, 70 insertions(+), 3 deletions(-)

We would like to be able to remap/unmap the VDSO on arm and arm64 as
well. When I proposed a patch with mmu_context.h and mmu-arch-hooks.h
changes to arm64 that were nearly identical to those done to powerpc,
Will Deacon reasonably suggested [1] attempting to combine the code and
provide generic VDSO accessors. Unfortunately, I no prior experience
with generic MM code. Can anyone advise on how to get started with that?

1. http://www.spinics.net/lists/linux-arm-msm/msg18441.html

Thanks,
Christopher Covington

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