Changeset 38dc82d in mainline for kernel/genarch/src/mm/page_pt.c

Timestamp:

2016-08-31T14:16:45Z (8 years ago)

Author:

Jakub Jermar <jakub@…>

Branches:

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

Children:

346b12a2

Parents:

dc05a9a

Message:

Make page_mapping_find() return a copy rather than the actual PTE

This makes page_mapping_find() more suitable for use with lock-free data
structures such as CHT that guarantee existence of the data only for
some limited time while a condition holds (e.g. inside of a RCU-protected
critical section that must be around all CHT lookups).

File:

• kernel/genarch/src/mm/page_pt.c (modified) (6 diffs)

kernel/genarch/src/mm/page_pt.c

@@ -53 +53 @@
 static void pt_mapping_insert(as_t *, uintptr_t, uintptr_t, unsigned int);
 static void pt_mapping_remove(as_t *, uintptr_t);
-static pte_t *pt_mapping_find(as_t *, uintptr_t, bool);
+static bool pt_mapping_find(as_t *, uintptr_t, bool, pte_t *pte);
 static void pt_mapping_make_global(uintptr_t, size_t);
 
@@ -291 +291 @@
 /** Find mapping for virtual page in hierarchical page tables.
  *
- * @param as     Address space to which page belongs.
- * @param page   Virtual page.
- * @param nolock True if the page tables need not be locked.
- *
- * @return NULL if there is no such mapping; entry from PTL3 describing
- *         the mapping otherwise.
- *
- */
-pte_t *pt_mapping_find(as_t *as, uintptr_t page, bool nolock)
+ * @param as       Address space to which page belongs.
+ * @param page     Virtual page.
+ * @param nolock   True if the page tables need not be locked.
+ * @param[out] pte Structure that will receive a copy of the found PTE.
+ *
+ * @return True if the mapping was found, false otherwise.
+ */
+bool pt_mapping_find(as_t *as, uintptr_t page, bool nolock, pte_t *pte)
 {
         ASSERT(nolock || page_table_locked(as));
@@ -305 +304 @@
         pte_t *ptl0 = (pte_t *) PA2KA((uintptr_t) as->genarch.page_table);
         if (GET_PTL1_FLAGS(ptl0, PTL0_INDEX(page)) & PAGE_NOT_PRESENT)
-                return NULL;
+                return false;
 
         read_barrier();
@@ -311 +310 @@
         pte_t *ptl1 = (pte_t *) PA2KA(GET_PTL1_ADDRESS(ptl0, PTL0_INDEX(page)));
         if (GET_PTL2_FLAGS(ptl1, PTL1_INDEX(page)) & PAGE_NOT_PRESENT)
-                return NULL;
+                return false;
 
 #if (PTL1_ENTRIES != 0)
@@ -322 +321 @@
         pte_t *ptl2 = (pte_t *) PA2KA(GET_PTL2_ADDRESS(ptl1, PTL1_INDEX(page)));
         if (GET_PTL3_FLAGS(ptl2, PTL2_INDEX(page)) & PAGE_NOT_PRESENT)
-                return NULL;
+                return false;
 
 #if (PTL2_ENTRIES != 0)
@@ -333 +332 @@
         pte_t *ptl3 = (pte_t *) PA2KA(GET_PTL3_ADDRESS(ptl2, PTL2_INDEX(page)));
         
-        return &ptl3[PTL3_INDEX(page)];
+        *pte = ptl3[PTL3_INDEX(page)];
+        return true;
 }