1 Ed L Cashin <ecashin@uga.edu> writes:
3 > Hi. This small patch documents that bits 9, 10, and 11 are unused by
4 > the Linux kernel. The IA-32 Intel Architecture Software Developer's
5 > Manual says that these bits are available for programmer use.
7 > I checked and couldn't see any use of these bits in the Linux kernel.
8 > If I'm wrong and these bits *are* being used by the linux kernel, a
9 > comment in include/asm-i386/pgtable.h would be helpful. If they are
10 > not, this patch confirms for developers that the kernel isn't using
13 For consistency, there should be the analogous _PAGE_BIT_XXX macros,
14 too, so here's a replacement patch that has those.
18 --- trivial-2.6.0-test5-bk10/include/asm-i386/pgtable.h.orig 2003-09-24 12:27:18.000000000 +1000
19 +++ trivial-2.6.0-test5-bk10/include/asm-i386/pgtable.h 2003-09-24 12:27:18.000000000 +1000
21 #define _PAGE_BIT_DIRTY 6
22 #define _PAGE_BIT_PSE 7 /* 4 MB (or 2MB) page, Pentium+, if present.. */
23 #define _PAGE_BIT_GLOBAL 8 /* Global TLB entry PPro+ */
24 +#define _PAGE_BIT_UNUSED1 9 /* available for programmer */
25 +#define _PAGE_BIT_UNUSED2 10
26 +#define _PAGE_BIT_UNUSED3 11
28 #define _PAGE_PRESENT 0x001
29 #define _PAGE_RW 0x002
31 #define _PAGE_DIRTY 0x040
32 #define _PAGE_PSE 0x080 /* 4 MB (or 2MB) page, Pentium+, if present.. */
33 #define _PAGE_GLOBAL 0x100 /* Global TLB entry PPro+ */
34 +#define _PAGE_UNUSED1 0x200 /* available for programmer */
35 +#define _PAGE_UNUSED2 0x400
36 +#define _PAGE_UNUSED3 0x800
38 #define _PAGE_FILE 0x040 /* set:pagecache unset:swap */
39 #define _PAGE_PROTNONE 0x080 /* If not present */