Avoid overflow with ephemerons (case UUM-25411)

Use GC_mark_and_push to safely push object for marking.

Author: joncham

external/bdwgc

@@ -73,8 +73,8 @@ mono_push_other_roots(void);
 
 static void
 mono_clear_ephemerons (void);
-static void
-mono_push_ephemerons (void);
+static struct GC_ms_entry*
+mono_push_ephemerons(struct GC_ms_entry* mark_stack_ptr, struct GC_ms_entry* mark_stack_limit);
 static void*
 null_ephemerons_for_domain (MonoDomain* domain);
 
@@ -2121,8 +2121,8 @@ mono_clear_ephemerons (void)
 }
 }
 
-static void
-mono_push_ephemerons (void)
+static struct GC_ms_entry*
+mono_push_ephemerons (struct GC_ms_entry* mark_stack_ptr, struct GC_ms_entry* mark_stack_limit)
 {
 ephemeron_node* prev_node = NULL;
 ephemeron_node* current_node = NULL;
@@ -2155,12 +2155,13 @@ mono_push_ephemerons (void)
 if (!GC_is_marked (current_ephemeron->key))
 continue;
 
-if (current_ephemeron->value && !GC_is_marked (current_ephemeron->value)) {
-/* the key is marked, so mark the value if needed */
-GC_push_all (&current_ephemeron->value, &current_ephemeron->value + 1);
+if (current_ephemeron->value) {
+mark_stack_ptr = GC_mark_and_push(current_ephemeron->value, mark_stack_ptr, mark_stack_limit, &current_ephemeron->value);
 }
 }
 }
+
+return mark_stack_ptr;
 }
 
 static void*