[PATCH 0/5] linux-user: Support extended clone(CLONE_VM)

[Josh Kunz <jkz@google.com>]

This patch series implements extended support for the `clone` system
call. As best I can tell, any option combination including `CLONE_VM`
should be supported with the addition of this patch series. The
implementation is described in greater detail in the patches themselves.

Testing:

  * All targets built on x86_64.
  * `make check` and `make check-tcg` are passing. Additional tests have
    been added to `linux-test.c` to validate clone behavior.

Caveats:

  * This series touches, but does not fix, several bits of code that are
    racey (namely the sigact table and the fd trans table).
  * `exit_group` does not perform the appropriate cleanup for non-thread
    children created with `CLONE_VM`. CPUs for such children are never
    cleaned up. The correct implementation of exit-group is non-trivial
    (since it also needs to track/handle cleanup for threads in the
    clone'd child process). Also, I don't fully understand the
    interaction between QOM<->linux-user. My naive implementation based
    on the current implementation `exit(2)` was regularly crashing. If
    maintainers have suggestions for better ways to handle exit_group,
    they would be greatly appreciated. 
  * execve does not clean up the CPUs of clone'd children, for the same
    reasons as `exit_group`.

Josh Kunz (5):
  linux-user: Refactor do_fork to use new `qemu_clone`
  linux-user: Make fd_trans task-specific.
  linux-user: Make sigact_table part of the task state.
  linux-user: Support CLONE_VM and extended clone options
  linux-user: Add PDEATHSIG test for clone process hierarchy.

 linux-user/Makefile.objs            |   2 +-
 linux-user/clone.c                  | 565 ++++++++++++++++++++++++++++
 linux-user/clone.h                  |  27 ++
 linux-user/fd-trans-tbl.c           |  13 +
 linux-user/fd-trans-type.h          |  17 +
 linux-user/fd-trans.c               |   3 -
 linux-user/fd-trans.h               |  75 ++--
 linux-user/main.c                   |   1 +
 linux-user/qemu.h                   |  49 +++
 linux-user/signal.c                 |  84 ++++-
 linux-user/syscall.c                | 452 ++++++++++++----------
 tests/tcg/multiarch/Makefile.target |   3 +
 tests/tcg/multiarch/linux-test.c    | 227 ++++++++++-
 13 files changed, 1264 insertions(+), 254 deletions(-)
 create mode 100644 linux-user/clone.c
 create mode 100644 linux-user/clone.h
 create mode 100644 linux-user/fd-trans-tbl.c
 create mode 100644 linux-user/fd-trans-type.h

-- 
2.27.0.290.gba653c62da-goog