Merge remote-tracking branch 'remotes/bsdimp/tags/bsd-user-arm-2022q1-pull-request...

Merge remote-tracking branch 'remotes/bsdimp/tags/bsd-user-arm-2022q1-pull-request' into staging

bsd-user: upstream signal implementation

Upstream the bsd-user fork signal implementation, for the most part.  This
series of commits represents nearly all of the infrastructure that surround
signals, except the actual system call glue (that was also reworked in the
fork and needs its own series). In addition, this adds the sigsegv and sigbus
code to arm. Even in the fork, we don't have good x86 signal implementation,
so there's little to upstream for that at the moment.

bsd-user's signal implementation is similar to linux-user's. The full context
can be found in the bsd-user's fork's 'blitz branch' at
https://github.com/qemu-bsd-user/qemu-bsd-user/tree/blitz which shows how these
are used to implement various system calls. Since this was built from
linux-user's stack stuff, evolved for BSD with the passage of a few years, it
no-doubt missed some bug fixes from linux-user (though nothing obvious stood out
in the quick comparison I made). After the first round of reviews, many of these
improvements have been incorporated.

Patchew history: https://patchew.org/QEMU/20220125012947.14974-1-imp@bsdimp.com/

# gpg: Signature made Mon 31 Jan 2022 19:55:51 GMT
# gpg:                using RSA key 2035F894B00AA3CF7CCDE1B76C1CD1287DB01100
# gpg: Good signature from "Warner Losh <wlosh@netflix.com>" [unknown]
# gpg:                 aka "Warner Losh <imp@bsdimp.com>" [unknown]
# gpg:                 aka "Warner Losh <imp@freebsd.org>" [unknown]
# gpg:                 aka "Warner Losh <imp@village.org>" [unknown]
# gpg:                 aka "Warner Losh <wlosh@bsdimp.com>" [unknown]
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# Primary key fingerprint: 2035 F894 B00A A3CF 7CCD  E1B7 6C1C D128 7DB0 1100

* remotes/bsdimp/tags/bsd-user-arm-2022q1-pull-request: (40 commits)
  bsd-user/freebsd/target_os_ucontext.h: Prefer env as arg name for CPUArchState args
  bsd-user: Rename arg name for target_cpu_reset to env
  MAINTAINERS: Add tests/vm/*bsd to the list to get reviews on
  bsd-user/signal.c: do_sigaltstack
  bsd-user/signal.c: implement do_sigaction
  bsd-user/signal.c: implement do_sigreturn
  bsd-user/signal.c: process_pending_signals
  bsd-user/signal.c: tswap_siginfo
  bsd-user/signal.c: handle_pending_signal
  bsd-user/signal.c: setup_frame
  bsd-user/signal.c: sigset manipulation routines.
  bsd-user/signal.c: Fill in queue_signal
  bsd-user/signal.c: Implement dump_core_and_abort
  bsd-user/strace.c: print_taken_signal
  bsd-user/signal.c: Implement host_signal_handler
  bsd-user/signal.c: Implement rewind_if_in_safe_syscall
  bsd-user/signal.c: host_to_target_siginfo_noswap
  bsd-user: Add trace events for bsd-user
  bsd-user: Add host signals to the build
  bsd-user/host/x86_64/host-signal.h: Implement host_signal_*
  ...

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>