*/
/*
- * Return a handle to the event channel driver, or NULL on failure, in
- * which case errno will be set appropriately.
+ * Opens the evtchn device node. Return a handle to the event channel
+ * driver, or NULL on failure, in which case errno will be set
+ * appropriately.
*
- * Note: After fork(2) a child process must not use any opened evtchn
- * handle inherited from their parent, nor access any grant mapped
- * areas associated with that handle.
+ * On fork(2):
*
- * The child must open a new handle if they want to interact with
- * evtchn.
+ * After fork, a child process must not use any opened evtchn handle
+ * inherited from their parent. This includes operations such as
+ * poll() on the underlying file descriptor. Calling xenevtchn_close()
+ * is the only safe operation on a xenevtchn_handle which has been
+ * inherited.
*
- * Calling exec(2) in a child will safely (and reliably) reclaim any
- * allocated resources via a xenevtchn_handle in the parent.
+ * The child must open a new handle if they want to interact with
+ * evtchn.
*
- * A child which does not call exec(2) may safely call
- * xenevtchn_close() on a xenevtchn_handle inherited from their
- * parent. This will attempt to reclaim any resources associated with
- * that handle. Note that in some implementations this reclamation may
- * not be completely effective, in this case any affected resources
- * remain allocated.
+ * On exec(2):
*
- * Calling xenevtchn_close() is the only safe operation on a
- * xenevtchn_handle which has been inherited.
+ * Wherever possible, the device node will be opened with O_CLOEXEC,
+ * so it is not inherited by the subsequent program.
+ *
+ * However the XENEVTCHN_NO_CLOEXEC flag may be used to avoid opening
+ * the device node with O_CLOEXEC. This is intended for use by
+ * daemons which support a self-reexec method of updating themselves.
+ *
+ * In this case, the updated daemon should pass the underlying file
+ * descriptor it inherited to xenevtchn_fdopen() to reconstruct the
+ * library handle.
*/
-/* Currently no flags are defined */
+
+/* Don't set O_CLOEXEC when opening event channel driver node. */
+#define XENEVTCHN_NO_CLOEXEC (1 << 0)
+
xenevtchn_handle *xenevtchn_open(struct xentoollog_logger *logger,
unsigned int flags);
+/* Flag XENEVTCHN_NO_CLOEXEC is rejected by xenevtchn_fdopen(). */
+xenevtchn_handle *xenevtchn_fdopen(struct xentoollog_logger *logger,
+ int fd, unsigned open_flags);
+
/*
- * Close a handle previously allocated with xenevtchn_open().
+ * Close a handle previously allocated with xenevtchn_{,fd}open().
*/
int xenevtchn_close(xenevtchn_handle *xce);
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;
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 )
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_fdopen(struct xentoollog_logger *logger,
+ int fd, unsigned int flags)
+{
+ xenevtchn_handle *xce;
+
+ if ( flags )
+ {
+ 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;
projects / xen.git / commitdiff