Closing the fd before unhooking it from the list runs the risk that a
concurrent thread calls xentoolcore_restrict_all will operate on the
old fd value, which might refer to a new fd by then. So we need to do
it in the other order.
Sadly this weakens the guarantee provided by xentoolcore_restrict_all
slightly, but not (I think) in a problematic way. It would be
possible to implement the previous guarantee, but it would involve
replacing all of the close() calls in all of the individual osdep
parts of all of the individual libraries with calls to a new function
which does
dup2("/dev/null", thing->fd);
pthread_mutex_lock(&handles_lock);
thing->fd = -1;
pthread_mutex_unlock(&handles_lock);
close(fd);
which would be terribly tedious.
Signed-off-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
Acked-by: Wei Liu <wei.liu2@citrix.com>
Reviewed-by: Ross Lagerwall <ross.lagerwall@citrix.com>
Release-acked-by: Julien Grall <julien.grall@linaro.org>
This necessitates adding $(CFLAGS_xeninclude) to all the depending
libraries (which can be done via Rules.mk), so that the definition of
domid_t (in xen.h) can be found.
Signed-off-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
Acked-by: Wei Liu <wei.liu2@citrix.com>
In practice, qemu opens a great many fds. Tracking them all down and
playing whack-a-mole is unattractive. It is also potentially fragile
in that future changes might accidentally undo our efforts.
Instead, we are going to teach all the Xen libraries how to register
their fds so that they can be neutered with one qemu call.
Right now, nothing will go wrong if some tries to link without
-ltoolcore, but that will stop working as soon as the first other Xen
library starts to register. So this patch will be followed by the
stubdom build update, and should be followed by a
MINIOS_UPSTREAM_REVISION updated.
Sadly qemu upstream's configuration arrangements are too crude, being
keyed solely off the Xen version number. So they cannot provide
forward/backward build compatibility across changes in xen-unstable,
like this one. qemu patches to link against xentoolcore should be
applied in qemu upstream so avoid the qemu build breaking against the
released version of Xen 4.10.
Signed-off-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
Acked-by: Wei Liu <wei.liu2@citrix.com>
Ian Jackson
Ross Lagerwall