Changeset 0882a9a in mainline for arch/ia32/include/mm/page.h

Timestamp:

2006-02-10T16:11:14Z (19 years ago)

Author:

Jakub Jermar <jakub@…>

Branches:

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

Children:

ecbdc724

Parents:

d0a0f12

Message:

Make use of one unused bit in PTE formats of amd64, ia32 and mips32 to store 1 in valid mappings.
This helps to distinguish valid entries from not present entries with 0 content (i.e. not present
entries with PFN 0 and other bits cleared).

File:

• arch/ia32/include/mm/page.h (modified) (3 diffs)

arch/ia32/include/mm/page.h

@@ -78 +78 @@
 #include <typedefs.h>
 
+/** Page Table Entry. */
 struct page_specifier {
         unsigned present : 1;
@@ -88 +89 @@
         unsigned pat : 1;
         unsigned global : 1;
-        unsigned avl : 3;
+        unsigned soft_valid : 1;        /**< Valid content even if the present bit is not set. */
+        unsigned avl : 2;
         unsigned frame_address : 20;
 } __attribute__ ((packed));
@@ -116 +118 @@
         p->writeable = (flags & PAGE_WRITE) != 0;
         p->global = (flags & PAGE_GLOBAL) != 0;
+        
+        /*
+         * Ensure that there is at least one bit set even if the present bit is cleared.
+         */
+        p->soft_valid = true;
 }