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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [PATCH v11 05/27] 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_fdopen() 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
V11:
- rename to xenevtchn_fdopen() (Andrew Cooper)
---
tools/include/xenevtchn.h | 16 +++++++-
tools/libs/evtchn/Makefile | 2 +-
tools/libs/evtchn/core.c | 64 ++++++++++++++++++++++--------
tools/libs/evtchn/freebsd.c | 6 ++-
tools/libs/evtchn/libxenevtchn.map | 4 ++
tools/libs/evtchn/linux.c | 6 ++-
tools/libs/evtchn/minios.c | 4 ++
7 files changed, 81 insertions(+), 21 deletions(-)
diff --git a/tools/include/xenevtchn.h b/tools/include/xenevtchn.h
index 3e9b6e7323..b6dd8f3186 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_fdopen() 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 int flags);
+/* Flag XENEVTCHN_NO_CLOEXEC is ignored by xenevtchn_fdopen(). */
+xenevtchn_handle *xenevtchn_fdopen(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 c069d5da71..f2ab27384b 100644
--- a/tools/libs/evtchn/core.c
+++ b/tools/libs/evtchn/core.c
@@ -30,18 +30,10 @@ 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 int flags)
+static xenevtchn_handle *xenevtchn_alloc_handle(xentoollog_logger *logger)
{
- xenevtchn_handle *xce;
- int rc;
-
- if ( flags )
- {
- errno = EINVAL;
- return NULL;
- }
+ xenevtchn_handle *xce = malloc(sizeof(*xce));
- xce = malloc(sizeof(*xce));
if ( !xce )
return NULL;
@@ -60,21 +52,59 @@ xenevtchn_handle *xenevtchn_open(xentoollog_logger *logger,
unsigned int flags)
goto err;
}
+ return xce;
+
+err:
+ xenevtchn_close(xce);
+ return NULL;
+}
+
+xenevtchn_handle *xenevtchn_open(xentoollog_logger *logger, unsigned int flags)
+{
+ xenevtchn_handle *xce;
+ int rc;
+
+ if ( flags & ~XENEVTCHN_NO_CLOEXEC )
+ {
+ errno = EINVAL;
+ return NULL;
+ }
+
+ xce = xenevtchn_alloc_handle(logger);
+ if ( !xce )
+ return NULL;
+
rc = osdep_evtchn_open(xce, flags);
- if ( rc < 0 )
+ 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);
-
+err:
+ xenevtchn_close(xce);
return NULL;
}
+xenevtchn_handle *xenevtchn_fdopen(struct xentoollog_logger *logger,
+ int fd, unsigned int flags)
+{
+ xenevtchn_handle *xce;
+
+ if ( 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 bb601f350f..ed2baf3c95 100644
--- a/tools/libs/evtchn/freebsd.c
+++ b/tools/libs/evtchn/freebsd.c
@@ -33,8 +33,12 @@
int osdep_evtchn_open(xenevtchn_handle *xce, unsigned int flags)
{
- int fd = open(EVTCHN_DEV, O_RDWR|O_CLOEXEC);
+ int open_flags = O_RDWR;
+ int fd;
+ if ( !(flags & XENEVTCHN_NO_CLOEXEC) )
+ open_flags |= O_CLOEXEC;
+ fd = open(EVTCHN_DEV, open_flags);
if ( fd == -1 )
return -1;
diff --git a/tools/libs/evtchn/libxenevtchn.map
b/tools/libs/evtchn/libxenevtchn.map
index 33a38f953a..4c180ea65d 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_fdopen;
+} VERS_1.1;
diff --git a/tools/libs/evtchn/linux.c b/tools/libs/evtchn/linux.c
index 62adc0e574..60bb75a791 100644
--- a/tools/libs/evtchn/linux.c
+++ b/tools/libs/evtchn/linux.c
@@ -36,8 +36,12 @@
int osdep_evtchn_open(xenevtchn_handle *xce, unsigned int flags)
{
- int fd = open("/dev/xen/evtchn", O_RDWR|O_CLOEXEC);
+ int open_flags = O_RDWR;
+ int fd;
+ if ( !(flags & XENEVTCHN_NO_CLOEXEC) )
+ open_flags |= O_CLOEXEC;
+ fd = open("/dev/xen/evtchn", open_flags);
if ( fd == -1 )
return -1;
diff --git a/tools/libs/evtchn/minios.c b/tools/libs/evtchn/minios.c
index 47c153c268..5728991cb8 100644
--- a/tools/libs/evtchn/minios.c
+++ b/tools/libs/evtchn/minios.c
@@ -69,6 +69,10 @@ static void port_dealloc(struct evtchn_port_info *port_info)
free(port_info);
}
+/*
+ * 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 flags)
{
int fd = alloc_fd(FTYPE_EVTCHN);
--
2.26.2
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