Today the file descriptor for the access of the event channel driver
is being closed in case of exec(2). For the support of live update of
a daemon using libxenevtchn this can be problematic, so add a way to
keep that file descriptor open.
Add support of a flag XENEVTCHN_NO_CLOEXEC for xenevtchn_open() which
will result in _not_ setting O_CLOEXEC when opening the event channel
driver node.
The caller can then obtain the file descriptor via xenevtchn_fd().
Add an alternative open function xenevtchn_open_fd() which takes that
file descriptor as an additional parameter. This allows to allocate a
xenevtchn_handle and to associate it with that file descriptor.
Signed-off-by: Juergen Gross <jgr...@suse.com>
Reviewed-by: Wei Liu <w...@xen.org>
Reviewed-by: Julien Grall <jgr...@amazon.com>
---
V7:
- new patch
V8:
- some minor comments by Julien Grall addressed
Signed-off-by: Juergen Gross <jgr...@suse.com>
---
tools/include/xenevtchn.h | 16 ++++++++++-
tools/libs/evtchn/Makefile | 2 +-
tools/libs/evtchn/core.c | 45 ++++++++++++++++++++++++------
tools/libs/evtchn/freebsd.c | 9 ++++--
tools/libs/evtchn/libxenevtchn.map | 4 +++
tools/libs/evtchn/linux.c | 9 ++++--
tools/libs/evtchn/minios.c | 6 +++-
tools/libs/evtchn/netbsd.c | 2 +-
tools/libs/evtchn/private.h | 2 +-
tools/libs/evtchn/solaris.c | 2 +-
10 files changed, 79 insertions(+), 18 deletions(-)
diff --git a/tools/include/xenevtchn.h b/tools/include/xenevtchn.h
index 91821ee56d..dadc46ea36 100644
--- a/tools/include/xenevtchn.h
+++ b/tools/include/xenevtchn.h
@@ -64,11 +64,25 @@ struct xentoollog_logger;
*
* Calling xenevtchn_close() is the only safe operation on a
* xenevtchn_handle which has been inherited.
+ *
+ * Setting XENEVTCHN_NO_CLOEXEC allows to keep the file descriptor used
+ * for the event channel driver open across exec(2). In order to be able
+ * to use that file descriptor the new binary activated via exec(2) has
+ * to call xenevtchn_open_fd() with that file descriptor as parameter in
+ * order to associate it with a new handle. The file descriptor can be
+ * obtained via xenevtchn_fd() before calling exec(2).
*/
-/* Currently no flags are defined */
+
+/* Don't set O_CLOEXEC when opening event channel driver node. */
+#define XENEVTCHN_NO_CLOEXEC 0x01
+
xenevtchn_handle *xenevtchn_open(struct xentoollog_logger *logger,
unsigned open_flags);
+/* Flag XENEVTCHN_NO_CLOEXEC is ignored by xenevtchn_open_fd(). */
+xenevtchn_handle *xenevtchn_open_fd(struct xentoollog_logger *logger,
+ int fd, unsigned open_flags);
+
/*
* Close a handle previously allocated with xenevtchn_open().
*/
diff --git a/tools/libs/evtchn/Makefile b/tools/libs/evtchn/Makefile
index ad01a17b3d..b8c37b5b97 100644
--- a/tools/libs/evtchn/Makefile
+++ b/tools/libs/evtchn/Makefile
@@ -2,7 +2,7 @@ XEN_ROOT = $(CURDIR)/../../..
include $(XEN_ROOT)/tools/Rules.mk
MAJOR = 1
-MINOR = 1
+MINOR = 2
SRCS-y += core.c
SRCS-$(CONFIG_Linux) += linux.c
diff --git a/tools/libs/evtchn/core.c b/tools/libs/evtchn/core.c
index aff6ecfaa0..fa1e44b6ea 100644
--- a/tools/libs/evtchn/core.c
+++ b/tools/libs/evtchn/core.c
@@ -13,6 +13,7 @@
* License along with this library; If not, see <http://www.gnu.org/licenses/>.
*/
+#include <errno.h>
#include <unistd.h>
#include <stdlib.h>
@@ -28,10 +29,9 @@ static int all_restrict_cb(Xentoolcore__Active_Handle *ah,
domid_t domid) {
return xenevtchn_restrict(xce, domid);
}
-xenevtchn_handle *xenevtchn_open(xentoollog_logger *logger, unsigned
open_flags)
+static xenevtchn_handle *xenevtchn_alloc_handle(xentoollog_logger *logger)
{
xenevtchn_handle *xce = malloc(sizeof(*xce));
- int rc;
if (!xce) return NULL;
@@ -49,19 +49,48 @@ xenevtchn_handle *xenevtchn_open(xentoollog_logger *logger,
unsigned open_flags)
if (!xce->logger) goto err;
}
- rc = osdep_evtchn_open(xce);
- if ( rc < 0 ) goto err;
+ return xce;
+
+err:
+ xenevtchn_close(xce);
+ return NULL;
+}
+
+xenevtchn_handle *xenevtchn_open(xentoollog_logger *logger, unsigned
open_flags)
+{
+ xenevtchn_handle *xce = xenevtchn_alloc_handle(logger);
+ int rc;
+
+ if (!xce) return NULL;
+
+ rc = osdep_evtchn_open(xce, open_flags);
+ if ( rc < 0 ) goto err;
return xce;
err:
- xentoolcore__deregister_active_handle(&xce->tc_ah);
- osdep_evtchn_close(xce);
- xtl_logger_destroy(xce->logger_tofree);
- free(xce);
+ xenevtchn_close(xce);
return NULL;
}
+xenevtchn_handle *xenevtchn_open_fd(struct xentoollog_logger *logger,
+ int fd, unsigned open_flags)
+{
+ xenevtchn_handle *xce;
+
+ if (open_flags & ~XENEVTCHN_NO_CLOEXEC) {
+ errno = EINVAL;
+ return NULL;
+ }
+
+ xce = xenevtchn_alloc_handle(logger);
+ if (!xce) return NULL;
+
+ xce->fd = fd;
+
+ return xce;
+}
+
int xenevtchn_close(xenevtchn_handle *xce)
{
int rc;
diff --git a/tools/libs/evtchn/freebsd.c b/tools/libs/evtchn/freebsd.c
index 6564ed4c44..635c10f09f 100644
--- a/tools/libs/evtchn/freebsd.c
+++ b/tools/libs/evtchn/freebsd.c
@@ -31,9 +31,14 @@
#define EVTCHN_DEV "/dev/xen/evtchn"
-int osdep_evtchn_open(xenevtchn_handle *xce)
+int osdep_evtchn_open(xenevtchn_handle *xce, unsigned int open_flags)
{
- int fd = open(EVTCHN_DEV, O_RDWR|O_CLOEXEC);
+ int flags = O_RDWR;
+ int fd;
+
+ if ( !(open_flags & XENEVTCHN_NO_CLOEXEC) )
+ flags |= O_CLOEXEC;
+ fd = open(EVTCHN_DEV, flags);
if ( fd == -1 )
return -1;
xce->fd = fd;
diff --git a/tools/libs/evtchn/libxenevtchn.map
b/tools/libs/evtchn/libxenevtchn.map
index 33a38f953a..722fa026f9 100644
--- a/tools/libs/evtchn/libxenevtchn.map
+++ b/tools/libs/evtchn/libxenevtchn.map
@@ -21,3 +21,7 @@ VERS_1.1 {
global:
xenevtchn_restrict;
} VERS_1.0;
+VERS_1.2 {
+ global:
+ xenevtchn_open_fd;
+} VERS_1.1;
diff --git a/tools/libs/evtchn/linux.c b/tools/libs/evtchn/linux.c
index 17e64aea32..2297488f88 100644
--- a/tools/libs/evtchn/linux.c
+++ b/tools/libs/evtchn/linux.c
@@ -34,9 +34,14 @@
#define O_CLOEXEC 0
#endif
-int osdep_evtchn_open(xenevtchn_handle *xce)
+int osdep_evtchn_open(xenevtchn_handle *xce, unsigned int open_flags)
{
- int fd = open("/dev/xen/evtchn", O_RDWR|O_CLOEXEC);
+ int flags = O_RDWR;
+ int fd;
+
+ if ( !(open_flags & XENEVTCHN_NO_CLOEXEC) )
+ flags |= O_CLOEXEC;
+ fd = open("/dev/xen/evtchn", flags);
if ( fd == -1 )
return -1;
xce->fd = fd;
diff --git a/tools/libs/evtchn/minios.c b/tools/libs/evtchn/minios.c
index 9cd7636fc5..f5db021747 100644
--- a/tools/libs/evtchn/minios.c
+++ b/tools/libs/evtchn/minios.c
@@ -63,7 +63,11 @@ static void port_dealloc(struct evtchn_port_info *port_info)
{
free(port_info);
}
-int osdep_evtchn_open(xenevtchn_handle *xce)
+/*
+ * XENEVTCHN_NO_CLOEXEC is being ignored, as there is no exec() call supported
+ * in Mini-OS.
+ */
+int osdep_evtchn_open(xenevtchn_handle *xce, unsigned int open_flags)
{
int fd = alloc_fd(FTYPE_EVTCHN);
if ( fd == -1 )
diff --git a/tools/libs/evtchn/netbsd.c b/tools/libs/evtchn/netbsd.c
index 8b8545d2f9..7c73d1c599 100644
--- a/tools/libs/evtchn/netbsd.c
+++ b/tools/libs/evtchn/netbsd.c
@@ -31,7 +31,7 @@
#define EVTCHN_DEV_NAME "/dev/xenevt"
-int osdep_evtchn_open(xenevtchn_handle *xce)
+int osdep_evtchn_open(xenevtchn_handle *xce, unsigned int open_flags)
{
int fd = open(EVTCHN_DEV_NAME, O_NONBLOCK|O_RDWR);
if ( fd == -1 )
diff --git a/tools/libs/evtchn/private.h b/tools/libs/evtchn/private.h
index 31e595bea2..bcac2a191d 100644
--- a/tools/libs/evtchn/private.h
+++ b/tools/libs/evtchn/private.h
@@ -14,7 +14,7 @@ struct xenevtchn_handle {
Xentoolcore__Active_Handle tc_ah;
};
-int osdep_evtchn_open(xenevtchn_handle *xce);
+int osdep_evtchn_open(xenevtchn_handle *xce, unsigned int open_flags);
int osdep_evtchn_close(xenevtchn_handle *xce);
int osdep_evtchn_restrict(xenevtchn_handle *xce, domid_t domid);
diff --git a/tools/libs/evtchn/solaris.c b/tools/libs/evtchn/solaris.c
index dd41f62a24..7e22f7906a 100644
--- a/tools/libs/evtchn/solaris.c
+++ b/tools/libs/evtchn/solaris.c
@@ -29,7 +29,7 @@
#include "private.h"
-int osdep_evtchn_open(xenevtchn_handle *xce)
+int osdep_evtchn_open(xenevtchn_handle *xce, unsigned int open_flags)
{
int fd;
--
2.26.2
