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 <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 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