Changeset 0882a9a in mainline for arch/amd64/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/amd64/include/mm/page.h (modified) (3 diffs)

arch/amd64/include/mm/page.h

@@ -76 +76 @@
 #ifndef __ASM__
 
+/** Page Table Entry. */
 struct page_specifier {
         unsigned present : 1;
@@ -86 +87 @@
         unsigned unused: 1;
         unsigned global : 1;
-        unsigned avl : 3;
+        unsigned soft_valid : 1;                /**< Valid content even if present bit is cleared. */
+        unsigned avl : 2;
         unsigned addr_12_31 : 30;
         unsigned addr_32_51 : 21;
@@ -125 +127 @@
         p->no_execute = (flags & PAGE_EXEC) == 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 = 1;
 }