Put the kernelside rump kernel headers into <rump-sys> instead of
sprinkling them around the faction directories. Avoids having
to add a CPPFLAGS (or several) to pretty much every component
Makefile.

Leave compat headers around in the old locations.

The commit changes some autogenerated files, but I'll fix the
generators shortly and regen.

Allow device components to create symlinks in /dev
e.g. /dev/audio -> audio0

from Robert Millan <rmh@freebsd.org> via rumpkernel-users

branches: 1.18.2;
Release all hypervisor-level resources for rump_etfs paths when the
rump kernel is halted.

Allows a Xen domU to not complain after it was shut down, or something
like that. Requested by Martin Lucina.

Make the device node creation routines function pointers which default
to nullop without VFS. This relaxes the dependency between VFS and many
components, some of which can be used perfectly fine without VFS.

Don't use __weak_alias where the component framework is sufficient.

branches: 1.15.2; 1.15.12;
define RUMPFS_MAXNAMLEN and use it.

Make the Diabolical (Page)Daemon Director drain vfs buffers when
we are short of memory.

There are still some funnies left to iron out. For example, with
a certain file system / memory size configuration it's still not
possible to create enough files to make the file system run out of
inodes before the kernel runs out of memory. Also, with some other
configurations disk access slows down gargantually (though i'm sure
there are >0 buffers available). Anyway, it ~works for now and
it's by no means worse than what it was before.

Implement rumpblk_deregister, for unregistering fake block devices
(from etfs_deregister). Prompted by use case from njoly.

Autogenerate /dev nodes. Use (recreate) the naming policy in
MAKEDEV. -- Not the famous irrational file system devfs, but an
incredible simulation.

Use reserved major for rumpblk instead of picking something which
may conflict.

branches: 1.10.2; 1.10.4;
* implement rump_vfs_makeonedevnode(), where the interface for creating
multiple nodes doesn't make sense: e.g. /dev/null would've had to
be created with ("/dev/nul", 'l', 1)
* implement said /dev/null (just for show)

Decide it's not worth the fuss to have rumpfs as a module and just
hardcode attach into rump_vfs_init(). Saves us from a lot of
pingpong init bouncing from one component to another to get the order
right.

For rumpfs, do mountroot instead of the bunch of homegrown hacks
currently there. Still needs a little massage to get the kernel
interfaces right and avoid copypaste especially from main().

Also, move it a bit more into the direction of a real file system
(finally!) by giving it a vfsops. Most ops are still unimplemented,
though.

Adjust rump sources for external/internal interfaces.
No functional change.

Provide an interface for reboot.

Allow to set size and host file offset for etfs files and rumpblk.

Rename rump_dev_makenodes() to rump_vfs_makedevnodes() -- while it
will most likely be used devices, the implementation requires
services provided by vfs (mkdir, mknod).

* get rid of the old fakeblk registration interface. Instead,
introduce a new and improved "etfs" interface, which can be used
to register host files accessible from rump fs namespace. This
new interface is not restriced to block devices, and neither does
it require the same pathname in host namespace and rump namespace.
Therefore, the same host file can be represented both as a char
and block device in rump namespace.

* adjust rumpblk to make the above possible

* improve rumpfs: nodes are now created properly and not implicitly
tied to the vnode lifecycle

branches: 1.2.2; 1.2.4; 1.2.8;
Implement block I/O as a real block driver instead of a hacked copy
of specfs. That was easier years ago when rump didn't support
devices, but brings no gain now. This allows us to include the
real specfs in rump.

Split vfs out of rumpkern into rumpvfs. Non-fs rumps no longer
include the file system code. File system rumps explicitly need
to include rumpvfs from now on.