x86: define PTE_MASK in a universally useful way

Define PTE_MASK so that it contains a meaningful value for all x86
pagetable configurations.  Previously it was defined as a "long" which
means that it was too short to cover a 32-bit PAE pte entry.

It is now defined as a pteval_t, which is an integer type long enough
to contain a full pte (or pmd, pud, pgd).

This fixes an Xorg crash on 32-bit x86 with PAE due to corruption of the
NX bit in mprotect due to the incorrect type/value of PTE_MASK reported
by Hugh Dickins:

  "Yes, thanks Jeremy: I've checked that each stage builds and runs X on
   my boxes here, x86_32 and x86_32+PAE and x86_64.  (So even 1/8 is
   enough to fix the PAT pte_modify issue, though 2/8 then fixes
   compiler warnings.)"

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Tested-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 9 insertions, 4 deletions

diff --git a/include/asm-x86/page.h b/include/asm-x86/page.h
index b381f4a5a0bd..76b35e636d7d 100644
--- a/include/asm-x86/page.h
+++ b/include/asm-x86/page.h
@@ -10,8 +10,13 @@
 
 #ifdef __KERNEL__
 
-#define PHYSICAL_PAGE_MASK      (PAGE_MASK & __PHYSICAL_MASK)
-#define PTE_MASK                (_AT(long, PHYSICAL_PAGE_MASK))
+/* Cast PAGE_MASK to a signed type so that it is sign-extended if
+   virtual addresses are 32-bits but physical addresses are larger
+   (ie, 32-bit PAE). */
+#define PHYSICAL_PAGE_MASK      (((signed long)PAGE_MASK) & __PHYSICAL_MASK)
+
+/* PTE_MASK extracts the PFN from a (pte|pmd|pud|pgd)val_t */
+#define PTE_MASK                ((pteval_t)PHYSICAL_PAGE_MASK)
 
 #define PMD_PAGE_SIZE           (_AC(1, UL) << PMD_SHIFT)
 #define PMD_PAGE_MASK           (~(PMD_PAGE_SIZE-1))
@@ -24,8 +29,8 @@
 /* to align the pointer to the (next) page boundary */
 #define PAGE_ALIGN(addr)        (((addr)+PAGE_SIZE-1)&PAGE_MASK)
 
-#define __PHYSICAL_MASK         _AT(phys_addr_t, (_AC(1,ULL) << __PHYSICAL_MASK_SHIFT) - 1)
-#define __VIRTUAL_MASK          ((_AC(1,UL) << __VIRTUAL_MASK_SHIFT) - 1)
+#define __PHYSICAL_MASK         ((((phys_addr_t)1) << __PHYSICAL_MASK_SHIFT) - 1)
+#define __VIRTUAL_MASK          ((1UL << __VIRTUAL_MASK_SHIFT) - 1)
 
 #ifndef __ASSEMBLY__
 #include <linux/types.h>