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Subject[TRIVIAL][PATCH] document unused pte bits on i386
Hi.  This small patch documents that bits 9, 10, and 11 are unused by
the Linux kernel. The IA-32 Intel Architecture Software Developer's
Manual says that these bits are available for programmer use.

I checked and couldn't see any use of these bits in the Linux kernel.
If I'm wrong and these bits *are* being used by the linux kernel, a
comment in include/asm-i386/pgtable.h would be helpful. If they are
not, this patch confirms for developers that the kernel isn't using
these bits.

--- linux-2.6.0-test2/include/asm-i386/pgtable.h~ Sun Jul 27 13:06:27 2003
+++ linux-2.6.0-test2/include/asm-i386/pgtable.h Thu Aug 7 11:16:36 2003
@@ -118,6 +118,9 @@
#define _PAGE_DIRTY 0x040
#define _PAGE_PSE 0x080 /* 4 MB (or 2MB) page, Pentium+, if present.. */
#define _PAGE_GLOBAL 0x100 /* Global TLB entry PPro+ */
+#define _PAGE_UNUSED1 0x200 /* available for programmer */
+#define _PAGE_UNUSED2 0x400
+#define _PAGE_UNUSED3 0x800

#define _PAGE_FILE 0x040 /* set:pagecache unset:swap */
#define _PAGE_PROTNONE 0x080 /* If not present */

--Ed L Cashin | PGP public key: |
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