[OpenAFS-devel] keyring/pag support for linux

[David Howells]

chas williams - CONTRACTOR <chas@cmf.nrl.navy.mil> wrote:

> and yet another version.  this time, you dont (or shouldnt) need changes
> to your local kernel tree.  we have our own version of join_session_keyring()
> which uses the public bits of the keyring api and a bit of information from
> task 1 to allocate and link a new session keyring.

I like your ingenuity:-)

> what we really need from the linux kernel: the keyring key_type exported,

Whilst I could do that, I'm not sure it'd help you as you'd need to use the
RCU interface to access keyrings directly.

> the keyring primitives exported,

That should be possible for the most part.  Which ones were you thinking of?

> or join_session_keyring() exported.

That should be possible.

You could also use something like:

	#include <asm/unistd.h>

	static inline _syscall2(long, keyctl, int, option, void*, arg2)

	long serial = keyctl(KEYCTL_JOIN_SESSION_KEYRING, NULL);

Which isn't very nice, but which ought to work.

> the first time might suffer a bit when it comes to safely inserting the
> session_key into the user task since the rcu primitives are not available to
> openafs, so the third option is preferred.

The first is a definite no-go if you can't use RCU - you could cause other
parts of the kernel to oops.

Another alternative might be to try putting the PAG stuff in the main kernel,
and add a keyctl function to set or get a pag.

The main thing I'm not sure about how to do is to change the PAG to which a
process's parent subscribes.  It is possible, but the locking is interesting.

David