YA pseudofs megacommit, part 2:
- Merge the pfs_vnode and pfs_vdata structures, and make the vnode cache
a doubly-linked list. This eliminates the need to walk the list in
pfs_vncache_free().
- Add an exit callout which revokes vnodes associated with the process
that just exited. Since it needs to lock the cache when it does this,
pfs_vncache_mutex needs MTX_RECURSE.
- Add a third callback to the pfs_node structure. This one simply returns
non-zero if the specified requesting process is allowed to access the
specified node for the specified target process. This is used in
addition to the usual permission checks, e.g. when certain files don't
make sense for certain (system) processes.
- Make sure that pfs_lookup() and pfs_readdir() don't yap about files
which aren't pfs_visible(). Also check pfs_visible() before performing
reads and writes, to prevent the kind of races reported in SA-00:77 and
SA-01:55 (fork a child, open /proc/child/ctl, have that child fork a
setuid binary, and assume control of it).
- Add some more trace points.
- Rearrange the flag constants a little to simplify specifying and testing
for readability and writeability.
pseudofs_vnops.c:
- Track the aforementioned change.
- Add checks to pfs_open() to prevent opening read-only files for writing
or vice versa (pfs_{read,write} would block the actual reads and writes,
but it's still a bug to allow the open() to succeed). Also, return
EOPNOTSUPP if the caller attempts to lock the file.
- Add more trace points.
- Remove hardcoded uid, gid, mode from struct pfs_node; make pfs_getattr()
smart enough to get it right most of the time, and allow for callbacks
to handle the remaining cases. Rework the definition macros to match.
- Add lots of (conditional) debugging output.
- Fix a long-standing bug inherited from procfs: don't pretend to be a
read-only file system. Instead, return EOPNOTSUPP for operations we
truly can't support and allow others to fail silently. In particular,
pfs_lookup() now treats CREATE as LOOKUP. This may need more work.
- In pfs_lookup(), if the parent node is process-dependent, check that
the process in question still exists.
- Implement pfs_open() - its only current function is to check that the
process opening the file can see the process it belongs to.
- Finish adding support for writeable nodes.
- Bump module version number.
- Introduce lots of new bugs.
Note ALL MODULES MUST BE RECOMPILED
make the kernel aware that there are smaller units of scheduling than the
process. (but only allow one thread per process at this time).
This is functionally equivalent to teh previousl -current except
that there is a thread associated with each process.
Sorry john! (your next MFC will be a doosie!)
Reviewed by: peter@freebsd.org, dillon@freebsd.org
X-MFC after: ha ha ha ha
It's not finished yet (I still have to find a way to implement process-
dependent nodes without consuming too much memory, and the permission
system needs tightening up), but it's becoming hard to work on without
a repo (I've accidentally almost nuked it once already), and it works
(except for the lack of process-dependent nodes, that is).
I was supposed to commit this a week ago, but timed out waiting for jkh
to reply to some questions I had. Pass him a spoonful of bad karma :)
