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    SubjectRe: [PATCH 0/6] x86: 32-bit compatible C/R on x86_64
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    On 06/01/2016 04:11 PM, Dmitry Safonov wrote:
    > This patches set is an attempt to add checkpoint/restore
    > for 32-bit tasks in compatibility mode on x86_64 hosts.
    >
    > Restore in CRIU starts from one root restoring process, which
    > reads info for all threads being restored from images files.
    > This information is used further to to find out which processes
    > share some resources. Later shared resources are restored only
    > by one process and all other inherit them.
    > After that it calls clone() and new threads restore their
    > properties in parallel. Those threads inherit all parent's
    > mappings and fetch properties from those mappings
    > (and do clone themself, if they have children/subthreads). [1]
    > Then starts restorer blob's play, it's PIE binary, which
    > unmaps all unneeded for restoring VMAs, maps new VMAs and
    > finalize restoring with sigreturn syscall. [2]
    >
    > To restore of 32-bit task we need three things to do in running
    > x86_64 restorer blob:
    > a) set code selector to __USER32_CS (to run 32-bit code);
    > b) remap vdso blob from 64-bit to 32-bit
    > This is primary needed because restore may happen on a different
    > kernel, which has different vDSO image than we had on dump.
    > c) if 32-bit vDSO differ to dumped image, move it on free place
    > and add jump trampolines to that place.
    > d) switch TIF_IA32 flag, so kernel would know that it deals with
    > compatible 32-bit application.
    >
    > From all this:
    > a) setting CS may be done from userspace, no patches needed;
    > b) patches 1-3 add ability to map different vDSO blobs on x86 kernel;
    > c) for remapping/moving 32-bit vDSO blob patches have been send earlier
    > and seems to be accepted [3]
    > d) and for swapping TIF_IA32 flag discussion with Andy ended in conclusion
    > that it's better to remove this flag completely.
    > Patches 4-6 deletes usage of TIF_IA32 from ptrace, signal and coredump
    > code. This is rework/resend of RFC [4]
    >
    > [1] https://criu.org/Checkpoint/Restore#Restore
    > [2] https://criu.org/Restorer_context
    > [3] https://lkml.org/lkml/2016/5/17/243
    > [4] https://lkml.org/lkml/2016/4/25/650
    >
    > Dmitry Safonov (6):
    > x86/vdso: unmap vdso blob on vvar mapping failure
    > x86/vdso: introduce do_map_vdso() and vdso_type enum
    > x86/arch_prctl/vdso: add ARCH_MAP_VDSO_*
    > x86/coredump: use core regs, rather that TIF_IA32 flag
    > x86/ptrace: down with test_thread_flag(TIF_IA32)
    > x86/signal: add SA_{X32,IA32}_ABI sa_flags

    Oh, forgot to mention: this patches set is based on [3],
    so kernel build bot may be not happy about applying them.
    Anyway, I hope for the next revisions, the base-patches
    will be applied to linux-next and build-bot will test them
    just fine.

    >
    > arch/x86/entry/vdso/vma.c | 72 +++++++++++++++++++++-----------------
    > arch/x86/ia32/ia32_signal.c | 2 +-
    > arch/x86/include/asm/compat.h | 8 ++---
    > arch/x86/include/asm/fpu/signal.h | 6 ++++
    > arch/x86/include/asm/vdso.h | 4 +++
    > arch/x86/include/uapi/asm/prctl.h | 6 ++++
    > arch/x86/include/uapi/asm/signal.h | 6 +++-
    > arch/x86/kernel/process_64.c | 10 ++++++
    > arch/x86/kernel/ptrace.c | 2 +-
    > arch/x86/kernel/signal.c | 19 +++++-----
    > arch/x86/kernel/signal_compat.c | 30 ++++++++++++++--
    > fs/binfmt_elf.c | 18 +++++-----
    > kernel/signal.c | 5 +++
    > 13 files changed, 129 insertions(+), 59 deletions(-)
    >


    --
    Regards,
    Dmitry Safonov

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