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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [PATCH v10 04/25] tools/libxenevtchn: add possibility to not close file descriptor on exec
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 <jgross@xxxxxxxx>
Reviewed-by: Wei Liu <wl@xxxxxxx>
Reviewed-by: Julien Grall <jgrall@xxxxxxxxxx>
---
V7:
- new patch
V8:
- some minor comments by Julien Grall addressed
Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
---
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
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