[PATCH 4/8] tools/ocaml/evtchn: Extend the init() binding with a cloexec flag

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

From: Edwin Török <edvin.torok@xxxxxxxxxx>

For live update, oxenstored wants to clear CLOEXEC on the evtchn handle, so it
survives the execve() into the new oxenstored.

Have the new interface match how cloexec works in other Ocaml standard
libraries.

Signed-off-by: Edwin Török <edvin.torok@xxxxxxxxxx>
Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Acked-by: Christian Lindig <christian.lindig@xxxxxxxxxx>
---
CC: Christian Lindig <christian.lindig@xxxxxxxxxx>
CC: David Scott <dave@xxxxxxxxxx>
CC: Edwin Torok <edvin.torok@xxxxxxxxxx>
CC: Rob Hoes <Rob.Hoes@xxxxxxxxxx>

Split out of combined patch
---
 tools/ocaml/libs/eventchn/xeneventchn.ml      |  5 ++++-
 tools/ocaml/libs/eventchn/xeneventchn.mli     |  9 ++++++---
 tools/ocaml/libs/eventchn/xeneventchn_stubs.c | 10 +++++++---
 3 files changed, 17 insertions(+), 7 deletions(-)

diff --git a/tools/ocaml/libs/eventchn/xeneventchn.ml 
b/tools/ocaml/libs/eventchn/xeneventchn.ml
index be4de82f46b9..c16fdd4674f7 100644
--- a/tools/ocaml/libs/eventchn/xeneventchn.ml
+++ b/tools/ocaml/libs/eventchn/xeneventchn.ml
@@ -16,7 +16,10 @@
 
 type handle
 
-external init: unit -> handle = "stub_eventchn_init"
+external _init: bool -> handle = "stub_eventchn_init"
+
+let init ?(cloexec=true) () = _init cloexec
+
 external fdopen: Unix.file_descr -> handle = "stub_eventchn_fdopen"
 external fd: handle -> Unix.file_descr = "stub_eventchn_fd"
 
diff --git a/tools/ocaml/libs/eventchn/xeneventchn.mli 
b/tools/ocaml/libs/eventchn/xeneventchn.mli
index 98b3c86f3702..870429b6b53a 100644
--- a/tools/ocaml/libs/eventchn/xeneventchn.mli
+++ b/tools/ocaml/libs/eventchn/xeneventchn.mli
@@ -43,9 +43,12 @@ val to_int: t -> int
 
 val of_int: int -> t
 
-val init: unit -> handle
-(** Return an initialised event channel interface. On error it
-    will throw a Failure exception. *)
+val init: ?cloexec:bool -> unit -> handle
+(** [init ?cloexec ()]
+    Return an initialised event channel interface.
+    The default is to close the underlying file descriptor
+    on [execve], which can be overriden with [~cloexec:false].
+    On error it will throw a Failure exception. *)
 
 val fdopen: Unix.file_descr -> handle
 (** Return an initialised event channel interface, from an already open evtchn
diff --git a/tools/ocaml/libs/eventchn/xeneventchn_stubs.c 
b/tools/ocaml/libs/eventchn/xeneventchn_stubs.c
index 7bdf711bc150..aa8a69cc1ecb 100644
--- a/tools/ocaml/libs/eventchn/xeneventchn_stubs.c
+++ b/tools/ocaml/libs/eventchn/xeneventchn_stubs.c
@@ -50,14 +50,18 @@ static struct custom_operations xenevtchn_ops = {
        .compare_ext = custom_compare_ext_default, /* Can't compare     */
 };
 
-CAMLprim value stub_eventchn_init(void)
+CAMLprim value stub_eventchn_init(value cloexec)
 {
-       CAMLparam0();
+       CAMLparam1(cloexec);
        CAMLlocal1(result);
        xenevtchn_handle *xce;
+       unsigned int flags = 0;
+
+       if ( !Bool_val(cloexec) )
+               flags |= XENEVTCHN_NO_CLOEXEC;
 
        caml_enter_blocking_section();
-       xce = xenevtchn_open(NULL, 0);
+       xce = xenevtchn_open(NULL, flags);
        caml_leave_blocking_section();
 
        if (xce == NULL)
-- 
2.11.0