MISRA C Rule 17.1 states: "The features of `<stdarg.h>' shall not be used"

The Xen community wants to avoid using variadic functions except for
specific circumstances where it feels appropriate by strict code review.

Functions hypercall_create_continuation and hypercall_xlat_continuation
are internal helper functions made to break long running hypercalls into
multiple calls. They take a variable number of arguments depending on the
original hypercall they are trying to continue.

Add SAF deviations for the aforementioned functions.

Signed-off-by: Simone Ballarin <simone.ballarin@bugseng.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>

docs/misra/safe.json

@@ -36,6 +36,14 @@
         },
         {
             "id": "SAF-4-safe",
+            "analyser": {
+                "eclair": "MC3R1.R17.1"
+            },
+            "name": "Rule 17.1: internal helper functions made to break long running hypercalls into multiple calls.",
+            "text": "They need to take a variable number of arguments depending on the original hypercall they are trying to continue."
+        },
+        {
+            "id": "SAF-5-safe",
             "analyser": {},
             "name": "Sentinel",
             "text": "Next ID to be used"

xen/arch/arm/domain.c

@@ -382,6 +382,7 @@ unsigned long hypercall_create_continuation(
     const char *p = format;
     unsigned long arg, rc;
     unsigned int i;
+    /* SAF-4-safe allowed variadic function */
     va_list args;
 
     current->hcall_preempted = true;

xen/arch/x86/hypercall.c

@@ -31,6 +31,7 @@ unsigned long hypercall_create_continuation(
     const char *p = format;
     unsigned long arg;
     unsigned int i;
+    /* SAF-4-safe allowed variadic function */
     va_list args;
 
     curr->hcall_preempted = true;
@@ -115,6 +116,7 @@ int hypercall_xlat_continuation(unsigned int *id, unsigned int nr,
     struct cpu_user_regs *regs;
     unsigned int i, cval = 0;
     unsigned long nval = 0;
+    /* SAF-4-safe allowed variadic function */
     va_list args;
 
     ASSERT(nr <= ARRAY_SIZE(mcs->call.args));