vm/vm_map: fix map entry merging

Map entry merging would not consider requests with objects, but it would
merge two neighbor entries without checking their object. Make checking the
object of both entries and requests part of the generic compatibility test.

1 files changed, 12 insertions, 10 deletions

diff --git a/vm/vm_map.c b/vm/vm_map.c
index 49b9e629..27361558 100644
--- a/vm/vm_map.c
+++ b/vm/vm_map.c
@@ -635,9 +635,14 @@ vm_map_prepare(struct vm_map *map, struct vm_object *object, unsigned long offse
  */
 
 static inline int
-vm_map_try_merge_compatible(int flags1, int flags2)
+vm_map_try_merge_compatible(const struct vm_map_request *request,
+                            const struct vm_map_entry *entry)
 {
-    return (flags1 & VM_MAP_ENTRY_MASK) == (flags2 & VM_MAP_ENTRY_MASK);
+    /* Only merge special kernel mappings for now */
+    return (request->object == NULL)
+           && (entry->object == NULL)
+           && ((request->flags & VM_MAP_ENTRY_MASK)
+               == (entry->flags & VM_MAP_ENTRY_MASK));
 }
 
 static struct vm_map_entry *
@@ -648,7 +653,7 @@ vm_map_try_merge_prev(struct vm_map *map, const struct vm_map_request *request,
 
     assert(entry != NULL);
 
-    if (!vm_map_try_merge_compatible(entry->flags, request->flags))
+    if (!vm_map_try_merge_compatible(request, entry))
         return NULL;
 
     if (entry->end != request->start)
@@ -671,7 +676,7 @@ vm_map_try_merge_next(struct vm_map *map, const struct vm_map_request *request,
 
     assert(entry != NULL);
 
-    if (!vm_map_try_merge_compatible(entry->flags, request->flags))
+    if (!vm_map_try_merge_compatible(request, entry))
         return NULL;
 
     end = request->start + request->size;
@@ -698,8 +703,8 @@ vm_map_try_merge_near(struct vm_map *map, const struct vm_map_request *request,
 
     if ((first->end == request->start)
         && ((request->start + request->size) == second->start)
-        && vm_map_try_merge_compatible(first->flags, request->flags)
-        && vm_map_try_merge_compatible(request->flags, second->flags)) {
+        && vm_map_try_merge_compatible(request, first)
+        && vm_map_try_merge_compatible(request, second)) {
         struct vm_map_entry *prev, *next;
 
         prev = vm_map_prev(map, first);
@@ -726,12 +731,9 @@ vm_map_try_merge(struct vm_map *map, const struct vm_map_request *request)
     struct vm_map_entry *entry, *prev;
     struct list *node;
 
+    /* Statically allocated map entries must not be merged */
     assert(!(request->flags & VM_MAP_NOMERGE));
 
-    /* Only merge special kernel mappings for now */
-    if (request->object != NULL)
-        return NULL;
-
     if (request->next == NULL) {
         node = list_last(&map->entry_list);