Implement the pte_special bit for x86. This is required to support lockless
get_user_pages, because we need to know whether or not we can refcount a
particular page given only its pte (and no vma).
Signed-off-by: Nick Piggin <npiggin@xxxxxxx>
---
Index: linux-2.6/include/asm-x86/pgtable.h
===================================================================
--- linux-2.6.orig/include/asm-x86/pgtable.h
+++ linux-2.6/include/asm-x86/pgtable.h
@@ -18,6 +18,7 @@
#define _PAGE_BIT_UNUSED1 9 /* available for programmer */
#define _PAGE_BIT_UNUSED2 10
#define _PAGE_BIT_UNUSED3 11
+#define _PAGE_BIT_SPECIAL _PAGE_BIT_UNUSED1
#define _PAGE_BIT_PAT_LARGE 12 /* On 2MB or 1GB pages */
#define _PAGE_BIT_NX 63 /* No execute: only valid after cpuid check */
@@ -40,6 +41,8 @@
#define _PAGE_UNUSED3 (_AC(1, L)<<_PAGE_BIT_UNUSED3)
#define _PAGE_PAT (_AC(1, L)<<_PAGE_BIT_PAT)
#define _PAGE_PAT_LARGE (_AC(1, L)<<_PAGE_BIT_PAT_LARGE)
+#define _PAGE_SPECIAL (_AC(1, L)<<_PAGE_BIT_SPECIAL)
+#define __HAVE_ARCH_PTE_SPECIAL
#if defined(CONFIG_X86_64) || defined(CONFIG_X86_PAE)
#define _PAGE_NX (_AC(1, ULL) << _PAGE_BIT_NX)
@@ -149,7 +152,7 @@ static inline int pte_file(pte_t pte) {
static inline int pte_huge(pte_t pte) { return pte_val(pte) & _PAGE_PSE; }
static inline int pte_global(pte_t pte) { return pte_val(pte) & _PAGE_GLOBAL; }
static inline int pte_exec(pte_t pte) { return !(pte_val(pte) & _PAGE_NX); }
-static inline int pte_special(pte_t pte) { return 0; }
+static inline int pte_special(pte_t pte) { return pte_val(pte) & _PAGE_SPECIAL; }
static inline int pmd_large(pmd_t pte) {
return (pmd_val(pte) & (_PAGE_PSE|_PAGE_PRESENT)) ==
@@ -167,7 +170,7 @@ static inline pte_t pte_mkhuge(pte_t pte
static inline pte_t pte_clrhuge(pte_t pte) { return __pte(pte_val(pte) & ~(pteval_t)_PAGE_PSE); }
static inline pte_t pte_mkglobal(pte_t pte) { return __pte(pte_val(pte) | _PAGE_GLOBAL); }
static inline pte_t pte_clrglobal(pte_t pte) { return __pte(pte_val(pte) & ~(pteval_t)_PAGE_GLOBAL); }
-static inline pte_t pte_mkspecial(pte_t pte) { return pte; }
+static inline pte_t pte_mkspecial(pte_t pte) { return __pte(pte_val(pte) | _PAGE_SPECIAL); }
extern pteval_t __supported_pte_mask;
--
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