[PATCH v2 0/2] linux-user: implement fsmount(2) series of syscalls

[Xinhui Yang <cyan@cyano.uk>]

The motivation of the implementation is to allow any foreign guest OSes
with systemd v259+ to boot using systemd-nspawn(1), otherwise any
systemd service requiring importing credentials will fail, including
journald, D-Bus service and getty. We used to work around this issue by
patching systemd to retry the clone() without CLONE_NEWNS, which is not
and can not be implemented in QEMU user emulation.

mount(8) from util-linux worked prior to this patch because it will
fallback to the old mount(2) syscall if fsmount(8) series of syscalls
is not available.

Tested good on an x86-64 host, with:

- an AOSC OS mips64r6el guest, which boots successfully with full systemd
  support using systemd-nspawn(1).
- a Gentoo ppc (big endian) guest, which boots successfully with full
  systemd support, using systemd-nspawn(1).

Changes from v1:

* Add missing guard for FSCONFIG_CMD_CREATE_EXCL in strace.c, since it is
  only available since 6.6.
* Fix some wording issues in the cover letter.

Xinhui Yang (2):
  linux-user: implement fsmount(2) series of syscalls
  linux-user/strace: add fsmount series of syscalls

 linux-user/strace.c    | 105 +++++++++++++++++++++++++++++++++++++++++
 linux-user/strace.list |  15 ++++++
 linux-user/syscall.c   |  81 +++++++++++++++++++++++++++++++
 3 files changed, 201 insertions(+)

-- 
2.52.0