them visible from userland, if need be.
I wish that the C language contained this as part of struct definintions,
but failing that, I would settle for an agreed upon set of functions for
packing/unpacking integers in various sizes from byte-streams which may
have unfriendly alignment.
This really belongs in <sys/endian.h> I guess.
the relevant classes.
Some methods may implement various "magic spaces", this is reserved
or magic areas on the disk, set a side for various and sundry purposes.
A good example is the BSD disklabel and boot code on i386 which occupies
a total of four magic spaces: boot1, the disklabel, the padding behind
the disklabel and boot2. The reason we don't simply tell people to
write the appropriate stuff on the underlying device is that (some of)
the magic spaces might be real-time modifiable. It is for instance
possible to change a disklabel while partitions are open, provided
the open partitions do not get trampled in the process.
Sponsored by: DARPA & NAI Labs.
Notice that if the device on which the dump is set is destroyed for
any reason, the dump setting is lost. This in particular will
happen in the case of spoilage. For instance if you set dump on
ad0s1b and open ad0 for writing, ad0s* will be spoilt and the dump
setting lost. See geom(4) for more about spoiling.
Sponsored by: DARPA & NAI Labs.
test and play with this.
This is not yet production quality and should be run only on dedicated
test boxes.
For people who want to develop transformations for GEOM there exist a
set of shims to run geom in userland (ask phk@freebsd.org).
Reports of all kinds to: phk@freebsd.org
Please include in report:
dmesg
sysctl debug.geomdot
sysctl debug.geomconf
Known significant limitations:
no kernel dump facility.
ioctls severely restricted.
Sponsored by: DARPA, NAI Labs
