[SPARC64]: Fix D-cache corruption in mremap

If we move a mapping from one virtual address to another,
and this changes the virtual color of the mapping to those
pages, we can see corrupt data due to D-cache aliasing.

Check for and deal with this by overriding the move_pte()
macro.  Set things up so that other platforms can cleanly
override the move_pte() macro too.

Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/asm-sparc64/pgtable.h b/include/asm-sparc64/pgtable.h
index c44e746..cd464f4 100644
--- a/include/asm-sparc64/pgtable.h
+++ b/include/asm-sparc64/pgtable.h
@@ -689,6 +689,23 @@
 #define pte_clear(mm,addr,ptep)		\
 	set_pte_at((mm), (addr), (ptep), __pte(0UL))
 
+#ifdef DCACHE_ALIASING_POSSIBLE
+#define __HAVE_ARCH_MOVE_PTE
+#define move_pte(pte, prot, old_addr, new_addr)				\
+({									\
+ 	pte_t newpte = (pte);						\
+	if (tlb_type != hypervisor && pte_present(pte)) {		\
+		unsigned long this_pfn = pte_pfn(pte);			\
+									\
+		if (pfn_valid(this_pfn) &&				\
+		    (((old_addr) ^ (new_addr)) & (1 << 13)))		\
+			flush_dcache_page_all(current->mm,		\
+					      pfn_to_page(this_pfn));	\
+	}								\
+	newpte;								\
+})
+#endif
+
 extern pgd_t swapper_pg_dir[2048];
 extern pmd_t swapper_low_pmd_dir[2048];