Merge remote-tracking branch 'remotes/bsdimp/tags/pull-bsd-user-20210910' into staging

Merge remote-tracking branch 'remotes/bsdimp/tags/pull-bsd-user-20210910' into staging

This series of patches gets me to the point that I can run "Hello World" on i386
and x86_64. This is for static binaries only, that are relatively small, but
it's better than the 100% instant mmap failre that is the current state of all
things bsd-user in upstream qemu. Future patch sets will refine this, add
the missing system calls, fix bugs preventing more sophisticated programms
from running and add a bunch of new architecture support.

There's three large themes in these patches, though the changes that
represent them are interrelated making it hard to separate out further.
1. Reorganization to support multiple OS and architectures (though I've only
   tested FreeBSD, other BSDs might not even compile yet).
2. Diff reduction with the bsd-user fork for several files. These diffs include
   changes that borrowed from linux-user as well as changes to make things work
   on FreeBSD. The records keeping when this was done, however, was poor at
   best, so many of the specific borrowings are going unacknowledged here, apart
   from this general ack. These diffs also include some minor code shuffling.
   Some of the changes are done specifically to make it easier to rebase
   the bsd-user fork's changes when these land in the tree (a number of changes
   have been pushed there to make this more possible).
3. Filling in the missing pieces to make things work. There's many changes to
   elfload to make it load things in the right places, to find the interpreter
   better, etc. There's changes to mmap.c to make the mappings work better and
   there's changes to main.c that were inspired, at least, by now-ancient changes
   to linux-user's main.c.

I ran checkpatch.pl on this, and there's 350-odd errors it identifies (the vast
majoirty come from BSD's fetish for tabs), so there will need to be a V2 to fix
this at the very least. In addition, the change set is big (about +~4.5k/-~2.5k
lines), so I anticipate some iteration as well just based on its sheer
size. I've tried to keep each set small to make it easy to review in isolation,
but I've also allowed some interrelated ones to get a little bigger than I'd
normally like. I've not done the customary documentation of the expected
checkpatch.pl output because it is large, and because I wanted to get review
of the other parts rolling to get this project unstuck. Future versions of the
patch will document the expected output.

In addition, I noticed a number of places where I could modernize to make the
code match things like linux-user better. I've resisted the urge to do these at
this time, since it would complicate merging the other ~30k lines of diff that
remains after this batch. Future batches should generally be smaller once this
one has landed since they are, by and large, either a bunch of new files to
support armv7, aarch64, riscv64, mips, mipsel, mips64, ppc, ppc64 and ppc64le,
or are adding system calls, which can be done individually or small groups. I've
removed sparc and sparc64 support as they've been removed from FreeBSD and
have been near totally busted for years.

Stacey Son did the bulk of this work originally, but since I had to move things
around so much and/or retool that work in non-trivial ways, I've kept myself as
author, and added his signed-off-by line. I'm unsure of the qemu standard
practice for this, but am happy to learn if this is too far outside its current
mainstream. For a while Sean Bruno did the merges from upstream, and he's
credited using his signed-off-by in appropriate places, though for this patch
set there's only a few. I've tried to ensure that others who have work in
individual patches that I've aggregated together also are reflected in their
signed-off-by. Given the chaotic stat of the upstream repo for its early
history, this may be the best that can be reconstructed at this late date. Most
of these files are 'foundational' so have existed from the earliest days when
record keeping wasn't quite what I'd wish for in hindsight. There was only
really one change that I could easily cherry-pick (Colin's), so I did that.

# gpg: Signature made Fri 10 Sep 2021 21:24:08 BST
# 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]
# gpg: WARNING: This key is not certified with a trusted signature!
# gpg:          There is no indication that the signature belongs to the owner.
# Primary key fingerprint: 2035 F894 B00A A3CF 7CCD  E1B7 6C1C D128 7DB0 1100

* remotes/bsdimp/tags/pull-bsd-user-20210910: (42 commits)
  bsd-user: Update mapping to handle reserved and starting conditions
  bsd-user: Add '-0 argv0' option to bsd-user/main.c
  bsd-user: Implement interlock for atomic operations
  bsd-user: move gemu_log to later in the file
  bsd-user: Refactor load_elf_sections and is_target_elf_binary
  bsd-user: elfload.c style catch up patch
  bsd-user: add stubbed out core dump support
  bsd-user: Add target_os_user.h to capture the user/kernel structures
  bsd-user: Add target_arch_reg to describe a target's register set
  bsd-user: update debugging in mmap.c
  bsd-user: Rewrite target system call definintion glue
  bsd-user: Remove dead #ifdefs from elfload.c
  bsd-user: elf cleanup
  bsd-user: Add architecture specific signal tramp code
  bsd-user: Move stack initializtion into a per-os file.
  bsd-user: Implement --seed and initialize random state
  bsd-user: *BSD specific siginfo defintions
  bsd-user: Add system independent stack, data and text limiting
  bsd-user: Create target specific vmparam.h
  bsd-user: define max args in terms of pages
  ...

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