Changeset cd1ecf11 in mainline

Timestamp:

2018-11-07T17:14:45Z (6 years ago)

Author:

Jiri Svoboda <jiri@…>

Branches:

lfn, master, serial, ticket/834-toolchain-update, topic/msim-upgrade, topic/simplify-dev-export

Children:

6785b88b

Parents:

d9d0088

Message:

Fix guard pages: should have one guard page before, one guard page after.

File:

• kernel/generic/src/mm/as.c (modified) (2 diffs)

kernel/generic/src/mm/as.c

@@ -324 +324 @@
  *
  * @return True if the two areas conflict, false otherwise.
- *
  */
 NO_TRACE static bool area_is_conflicting(uintptr_t addr,
@@ -331 +330 @@
         assert((addr % PAGE_SIZE) == 0);
 
-        /* Add guard page size unless area is at the end of VA domain */
         size_t gsize = P2SZ(count);
-        if (guarded && !overflows(addr, P2SZ(count)))
-                gsize += PAGE_SIZE;
-
-        /* Add guard page size unless area is at the end of VA domain */
-        size_t agsize = P2SZ(area->pages);
-        if ((area->flags & AS_AREA_GUARD) != 0 &&
-            !overflows(area->base, P2SZ(area->pages)))
-                agsize += PAGE_SIZE;
+        size_t agsize = P2SZ(area->pages);
+
+        /*
+         * A guarded area has one guard page before, one page after.
+         * What we do here is: if either area is guarded, we add
+         * PAGE_SIZE to the size of both areas. That guarantees
+         * they will be spaced at least one page apart.
+         */
+        if (guarded || (area->flags & AS_AREA_GUARD) != 0) {
+                /* Add guard page size unless area is at the end of VA domain */
+                if (!overflows(addr, P2SZ(count)))
+                        gsize += PAGE_SIZE;
+
+                /* Add guard page size unless area is at the end of VA domain */
+                if (!overflows(area->base, P2SZ(area->pages)))
+                        agsize += PAGE_SIZE;
+        }
 
         return overlaps(addr, gsize, area->base, agsize);