Re: [Bug 10732] REGRESSION: 2.6.26-rc2-git4: X server failed startonX61s laptop

From: Linus Torvalds
Date: Mon May 19 2008 - 22:35:14 EST

On Mon, 19 May 2008, Linus Torvalds wrote:
> IOE, PTE_MASK should be a "pteval_t". And it should have absolutely
> *nothing* to do with PAGE_MASK. EVER.
> IOW, maybe something like this?

.. and in addition to that, perhaps something like this too?

Making the actual _PAGE_XYZ bits be of the proper type makes using bitops
and negation on them automatically DTRT, so that we don't need those
insane casts in pte_mkclean() and friends.

Again, totally untested, but we really should just get the types right,
instead of getting them wrogn and then messing around with various silly
and incorrect work-arounds for the fact that we got them wrong.

And while it's untested - if this cleanup is buggy (or even generates
different code), then we're doing something really wrong somewhere.


include/asm-x86/pgtable.h | 49 +++++++++++++++++++++++----------------------
1 files changed, 25 insertions(+), 24 deletions(-)

diff --git a/include/asm-x86/pgtable.h b/include/asm-x86/pgtable.h
index 55c3a0e..b38b540 100644
--- a/include/asm-x86/pgtable.h
+++ b/include/asm-x86/pgtable.h
@@ -21,27 +21,28 @@
#define _PAGE_BIT_NX 63 /* No execute: only valid after cpuid check */

- * Note: we use _AC(1, L) instead of _AC(1, UL) so that we get a
- * sign-extended value on 32-bit with all 1's in the upper word,
- * which preserves the upper pte values on 64-bit ptes:
+ * Note: we use _AT(pteval_t,1) so that we get the right type
+ * even when we're using PAE and everything is 64-bit with a
+ " 32-bit word-size. That's important for various bit masks.
-#define _PAGE_RW (_AC(1, L)<<_PAGE_BIT_RW)
-#define _PAGE_USER (_AC(1, L)<<_PAGE_BIT_USER)
-#define _PAGE_PWT (_AC(1, L)<<_PAGE_BIT_PWT)
-#define _PAGE_PCD (_AC(1, L)<<_PAGE_BIT_PCD)
-#define _PAGE_DIRTY (_AC(1, L)<<_PAGE_BIT_DIRTY)
-#define _PAGE_PSE (_AC(1, L)<<_PAGE_BIT_PSE) /* 2MB page */
-#define _PAGE_GLOBAL (_AC(1, L)<<_PAGE_BIT_GLOBAL) /* Global TLB entry */
-#define _PAGE_UNUSED1 (_AC(1, L)<<_PAGE_BIT_UNUSED1)
-#define _PAGE_UNUSED2 (_AC(1, L)<<_PAGE_BIT_UNUSED2)
-#define _PAGE_UNUSED3 (_AC(1, L)<<_PAGE_BIT_UNUSED3)
-#define _PAGE_PAT (_AC(1, L)<<_PAGE_BIT_PAT)
+#define _PAGE_BIT(x) (_AT(pteval_t,1) << (x))
+#define _PAGE_PSE _PAGE_BIT(_PAGE_BIT_PSE) /* 2MB page */
+#define _PAGE_GLOBAL _PAGE_BIT(_PAGE_BIT_GLOBAL) /* Global TLB entry */

#if defined(CONFIG_X86_64) || defined(CONFIG_X86_PAE)
-#define _PAGE_NX (_AC(1, ULL) << _PAGE_BIT_NX)
#define _PAGE_NX 0
@@ -209,22 +210,22 @@ static inline int pmd_large(pmd_t pte)

static inline pte_t pte_mkclean(pte_t pte)
- return __pte(pte_val(pte) & ~(pteval_t)_PAGE_DIRTY);
+ return __pte(pte_val(pte) & ~_PAGE_DIRTY);

static inline pte_t pte_mkold(pte_t pte)
- return __pte(pte_val(pte) & ~(pteval_t)_PAGE_ACCESSED);
+ return __pte(pte_val(pte) & ~_PAGE_ACCESSED);

static inline pte_t pte_wrprotect(pte_t pte)
- return __pte(pte_val(pte) & ~(pteval_t)_PAGE_RW);
+ return __pte(pte_val(pte) & ~_PAGE_RW);

static inline pte_t pte_mkexec(pte_t pte)
- return __pte(pte_val(pte) & ~(pteval_t)_PAGE_NX);
+ return __pte(pte_val(pte) & ~_PAGE_NX);

static inline pte_t pte_mkdirty(pte_t pte)
@@ -249,7 +250,7 @@ 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);
+ return __pte(pte_val(pte) & ~_PAGE_PSE);

static inline pte_t pte_mkglobal(pte_t pte)
@@ -259,7 +260,7 @@ static inline pte_t pte_mkglobal(pte_t pte)

static inline pte_t pte_clrglobal(pte_t pte)
- return __pte(pte_val(pte) & ~(pteval_t)_PAGE_GLOBAL);
+ return __pte(pte_val(pte) & ~_PAGE_GLOBAL);

static inline pte_t pte_mkspecial(pte_t pte)
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