xen: fix build race condition

It has been reported that xen can fail to build with the
following error:

| In file included from xsm/flask/ss/services.c:46:
| ./xsm/flask/include/avc.h:18:10: fatal error: av_permissions.h: No
such file or directory
|    18 | #include "av_permissions.h"
|       |          ^~~~~~~~~~~~~~~~~~

This fix has been proposed upstream:
https://lore.kernel.org/xen-devel/20230120133626.55680-1-anthony.perard@citrix.com/T/#u

It doesn't break our build, so we include it for stress testing.

Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>

recipes-extended/xen/files/xen-flask-race-fix.patch

@@ -0,0 +1,54 @@
+From mboxrd@z Thu Jan  1 00:00:00 1970
+From: Anthony PERARD <anthony.perard@citrix.com>
+Subject: [XEN PATCH] build: fix building flask headers before descending in flask/ss/
+Date: Fri, 20 Jan 2023 13:36:26 +0000
+Message-ID: <20230120133626.55680-1-anthony.perard@citrix.com>
+X-Mailer: git-send-email 2.30.2
+MIME-Version: 1.0
+Content-Transfer-Encoding: 8bit
+Content-Type: text/plain
+
+Unfortunatly, adding prerequisite to "$(obj)/ss/built_in.o" doesn't
+work because we have "$(obj)/%/built_in.o: $(obj)/% ;" in Rules.mk.
+So, make is allow to try to build objects in "xsm/flask/ss/" before
+generating the headers.
+
+Adding a prerequisite on "$(obj)/ss" instead will fix the issue has
+that the target used to run make in this subdirectory.
+
+Unfortunatly, that target is also used when running `make clean`, so
+we need to ignore it in this case. $(MAKECMDGOALS) can't be used in
+this case as it is empty, but we can guess which operation is done by
+looking at the list of loaded makefiles.
+
+Upstream-Status: backport [https://lore.kernel.org/xen-devel/20230120133626.55680-1-anthony.perard@citrix.com/T/#u]
+
+Fixes: 7a3bcd2babcc ("build: build everything from the root dir, use obj=$subdir")
+Reported-by: "Daniel P. Smith" <dpsmith@apertussolutions.com>
+Signed-off-by: Anthony PERARD <anthony.perard@citrix.com>
+---
+ xen/xsm/flask/Makefile | 6 +++++-
+ 1 file changed, 5 insertions(+), 1 deletion(-)
+
+diff --git a/xen/xsm/flask/Makefile b/xen/xsm/flask/Makefile
+index d25312f4fa..2d24346ee3 100644
+--- a/xen/xsm/flask/Makefile
++++ b/xen/xsm/flask/Makefile
+@@ -16,7 +16,11 @@ FLASK_H_FILES := flask.h class_to_string.h initial_sid_to_string.h
+ AV_H_FILES := av_perm_to_string.h av_permissions.h
+ ALL_H_FILES := $(addprefix include/,$(FLASK_H_FILES) $(AV_H_FILES))
+ 
+-$(addprefix $(obj)/,$(obj-y)) $(obj)/ss/built_in.o: $(addprefix $(obj)/,$(ALL_H_FILES))
++# Adding prerequisite to descending into ss/ folder only when not running `make
++# clean`.
++ifeq ($(filter %/Makefile.clean,$(MAKEFILE_LIST)),)
++$(addprefix $(obj)/,$(obj-y)) $(obj)/ss: $(addprefix $(obj)/,$(ALL_H_FILES))
++endif
+ extra-y += $(ALL_H_FILES)
+ 
+ mkflask := $(srcdir)/policy/mkflask.sh
+-- 
+Anthony PERARD
+
+
+

recipes-extended/xen/xen_4.17.bb

@@ -7,6 +7,7 @@ XEN_BRANCH ?= "stable-${XEN_REL}"
 SRC_URI = " \
     git://xenbits.xen.org/xen.git;branch=${XEN_BRANCH} \
     file://0001-menuconfig-mconf-cfg-Allow-specification-of-ncurses-location.patch \
+    file://xen-flask-race-fix.patch \
     "
 
 LIC_FILES_CHKSUM ?= "file://COPYING;md5=d1a1e216f80b6d8da95fec897d0dbec9"

recipes-extended/xen/xen_git.bb

@@ -7,6 +7,7 @@ XEN_BRANCH ?= "master"
 SRC_URI = " \
     git://xenbits.xen.org/xen.git;branch=${XEN_BRANCH} \
     file://0001-menuconfig-mconf-cfg-Allow-specification-of-ncurses-location.patch \
+    file://xen-flask-race-fix.patch \
     "
 
 LIC_FILES_CHKSUM ?= "file://COPYING;md5=d1a1e216f80b6d8da95fec897d0dbec9"