xen/xsm: Wire up get_dom0_console

An XSM hook for get_dom0_console is currently missing.  Using XSM with
a PVH dom0 shows:
(XEN) FLASK: Denying unknown platform_op: 64.

Wire up the hook, and allow it for dom0.

Fixes: 4dd160583c ("x86/platform: introduce hypercall to get initial video console settings")
Signed-off-by: Jason Andryuk <jason.andryuk@amd.com>
Acked-by: Daniel P. Smith <dpsmith@apertussolutions.com>
master commit: 647f7e50eb
master date: 2024-04-30 08:33:41 +0200

tools/flask/policy/modules/dom0.te

@@ -16,7 +16,7 @@ allow dom0_t xen_t:xen {
 allow dom0_t xen_t:xen2 {
 	resource_op psr_cmt_op psr_alloc pmu_ctrl get_symbol
 	get_cpu_levelling_caps get_cpu_featureset livepatch_op
-	coverage_op
+	coverage_op get_dom0_console
 };
 
 # Allow dom0 to use all XENVER_ subops that have checks.

xen/xsm/flask/hooks.c

@@ -1558,6 +1558,10 @@ static int cf_check flask_platform_op(uint32_t op)
         return avc_has_perm(domain_sid(current->domain), SECINITSID_XEN,
                             SECCLASS_XEN2, XEN2__GET_SYMBOL, NULL);
 
+    case XENPF_get_dom0_console:
+        return avc_has_perm(domain_sid(current->domain), SECINITSID_XEN,
+                            SECCLASS_XEN2, XEN2__GET_DOM0_CONSOLE, NULL);
+
     default:
         return avc_unknown_permission("platform_op", op);
     }

xen/xsm/flask/policy/access_vectors

@@ -99,6 +99,8 @@ class xen2
     livepatch_op
 # XEN_SYSCTL_coverage_op
     coverage_op
+# XENPF_get_dom0_console
+    get_dom0_console
 }
 
 # Classes domain and domain2 consist of operations that a domain performs on