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Index: sys/kern/sys_process.c
===================================================================
--- sys/kern/sys_process.c
+++ sys/kern/sys_process.c
@@ -387,8 +387,9 @@
error = EINVAL;
break;
}
- while (entry != &map->header &&
- (entry->eflags & MAP_ENTRY_IS_SUB_MAP) != 0) {
+ KASSERT((map->header.eflags & MAP_ENTRY_IS_SUB_MAP) == 0,
+ ("Submap in map header"));
+ while ((entry->eflags & MAP_ENTRY_IS_SUB_MAP) != 0) {
entry = entry->next;
index++;
}
Index: sys/vm/vm_map.h
===================================================================
--- sys/vm/vm_map.h
+++ sys/vm/vm_map.h
@@ -146,6 +146,7 @@
#define MAP_ENTRY_GUARD 0x10000
#define MAP_ENTRY_STACK_GAP_DN 0x20000
#define MAP_ENTRY_STACK_GAP_UP 0x40000
+#define MAP_ENTRY_HEADER 0x80000
#ifdef _KERNEL
static __inline u_char
@@ -175,15 +176,17 @@
* list. Both structures are ordered based upon the start and
* end addresses contained within each map entry.
*
- * Counterintuitively, the map's min offset value is stored in
- * map->header.end, and its max offset value is stored in
- * map->header.start.
- *
- * The list header has max start value and min end value to act
- * as sentinels for sequential search of the doubly-linked list.
* Sleator and Tarjan's top-down splay algorithm is employed to
* control height imbalance in the binary search tree.
*
+ * The map's min offset value is stored in map->header.end, and
+ * its max offset value is stored in map->header.start. These
+ * values act as sentinels for any forward or backward address
+ * scan of the list. The map header has a special value for the
+ * eflags field, MAP_ENTRY_HEADER, that is set initially, is
+ * never changed, and prevents an eflags match of the header
+ * with any other map entry.
+ *
* List of locks
* (c) const until freed
*/
Index: sys/vm/vm_map.c
===================================================================
--- sys/vm/vm_map.c
+++ sys/vm/vm_map.c
@@ -796,6 +796,7 @@
{
map->header.next = map->header.prev = &map->header;
+ map->header.eflags = MAP_ENTRY_HEADER;
map->needs_wakeup = FALSE;
map->system_map = 0;
map->pmap = pmap;
@@ -1277,8 +1278,8 @@
if (object->ref_count > 1 || object->shadow_count != 0)
vm_object_clear_flag(object, OBJ_ONEMAPPING);
VM_OBJECT_WUNLOCK(object);
- } else if (prev_entry != &map->header &&
- (prev_entry->eflags & ~MAP_ENTRY_USER_WIRED) == protoeflags &&
+ } else if ((prev_entry->eflags & ~MAP_ENTRY_USER_WIRED) ==
+ protoeflags &&
(cow & (MAP_STACK_GROWS_DOWN | MAP_STACK_GROWS_UP)) == 0 &&
prev_entry->end == start && (prev_entry->cred == cred ||
(prev_entry->object.vm_object != NULL &&
@@ -1708,8 +1709,7 @@
return;
prev = entry->prev;
- if (prev != &map->header &&
- vm_map_mergeable_neighbors(prev, entry)) {
+ if (vm_map_mergeable_neighbors(prev, entry)) {
vm_map_entry_unlink(map, prev);
entry->start = prev->start;
entry->offset = prev->offset;
@@ -1719,8 +1719,7 @@
}
next = entry->next;
- if (next != &map->header &&
- vm_map_mergeable_neighbors(entry, next)) {
+ if (vm_map_mergeable_neighbors(entry, next)) {
vm_map_entry_unlink(map, next);
entry->end = next->end;
vm_map_entry_resize_free(map, entry);

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