[ARM] Fix copy/clear user page functions for VIPT aliasing caches.

This fixes the copy and clear user page functions for ARMv6 aliasing
caches.  When we copy data into a page destined for user space, we
must make sure that there are no dirty cache lines associated with
the kernel space mapping of this page.

arch/arm/mm/copypage-v6.c

@@ -31,14 +31,46 @@ static spinlock_t v6_lock = SPIN_LOCK_UNLOCKED;
 
 #define DCACHE_COLOUR(vaddr) ((vaddr & (SHMLBA - 1)) >> PAGE_SHIFT)
 
+/*
+ * Copy the user page.  No aliasing to deal with so we can just
+ * attack the kernel's existing mapping of these pages.
+ */
+void v6_copy_user_page_nonaliasing(void *kto, const void *kfrom, unsigned long vaddr)
+{
+	copy_page(kto, kfrom);
+}
+
+/*
+ * Clear the user page.  No aliasing to deal with so we can just
+ * attack the kernel's existing mapping of this page.
+ */
+void v6_clear_user_page_nonaliasing(void *kaddr, unsigned long vaddr)
+{
+	clear_page(kaddr);
+}
+
 /*
  * Copy the page, taking account of the cache colour.
  */
-void v6_copy_user_page(void *kto, const void *kfrom, unsigned long vaddr)
+void v6_copy_user_page_aliasing(void *kto, const void *kfrom, unsigned long vaddr)
 {
 	unsigned int offset = DCACHE_COLOUR(vaddr);
 	unsigned long from, to;
 
+	/*
+	 * Discard data in the kernel mapping for the new page.
+	 * FIXME: needs this MCRR to be supported.
+	 */
+	__asm__("mcrr	p15, 0, %1, %0, c6	@ 0xec401f06"
+	   :
+	   : "r" (kto),
+	     "r" ((unsigned long)kto + PAGE_SIZE - L1_CACHE_BYTES)
+	   : "cc");
+
+	/*
+	 * Now copy the page using the same cache colour as the
+	 * pages ultimate destination.
+	 */
 	spin_lock(&v6_lock);
 
 	set_pte(from_pte + offset, pfn_pte(__pa(kfrom) >> PAGE_SHIFT, from_pgprot));
@@ -55,11 +87,30 @@ void v6_copy_user_page(void *kto, const void *kfrom, unsigned long vaddr)
 	spin_unlock(&v6_lock);
 }
 
-void v6_clear_user_page(void *kaddr, unsigned long vaddr)
+/*
+ * Clear the user page.  We need to deal with the aliasing issues,
+ * so remap the kernel page into the same cache colour as the user
+ * page.
+ */
+void v6_clear_user_page_aliasing(void *kaddr, unsigned long vaddr)
 {
 	unsigned int offset = DCACHE_COLOUR(vaddr);
 	unsigned long to = to_address + (offset << PAGE_SHIFT);
 
+	/*
+	 * Discard data in the kernel mapping for the new page
+	 * FIXME: needs this MCRR to be supported.
+	 */
+	__asm__("mcrr	p15, 0, %1, %0, c6	@ 0xec401f06"
+	   :
+	   : "r" (kaddr),
+	     "r" ((unsigned long)kaddr + PAGE_SIZE - L1_CACHE_BYTES)
+	   : "cc");
+
+	/*
+	 * Now clear the page using the same cache colour as
+	 * the pages ultimate destination.
+	 */
 	spin_lock(&v6_lock);
 
 	set_pte(to_pte + offset, pfn_pte(__pa(kaddr) >> PAGE_SHIFT, to_pgprot));
@@ -70,26 +121,31 @@ void v6_clear_user_page(void *kaddr, unsigned long vaddr)
 }
 
 struct cpu_user_fns v6_user_fns __initdata = {
-	.cpu_clear_user_page	= v6_clear_user_page,
-	.cpu_copy_user_page	= v6_copy_user_page,
+	.cpu_clear_user_page	= v6_clear_user_page_nonaliasing,
+	.cpu_copy_user_page	= v6_copy_user_page_nonaliasing,
 };
 
 static int __init v6_userpage_init(void)
 {
-	pgd_t *pgd;
-	pmd_t *pmd;
-
-	pgd = pgd_offset_k(from_address);
-	pmd = pmd_alloc(&init_mm, pgd, from_address);
-	if (!pmd)
-		BUG();
-	from_pte = pte_alloc_kernel(&init_mm, pmd, from_address);
-	if (!from_pte)
-		BUG();
-
-	to_pte = pte_alloc_kernel(&init_mm, pmd, to_address);
-	if (!to_pte)
-		BUG();
+	if (cache_is_vipt_aliasing()) {
+		pgd_t *pgd;
+		pmd_t *pmd;
+
+		pgd = pgd_offset_k(from_address);
+		pmd = pmd_alloc(&init_mm, pgd, from_address);
+		if (!pmd)
+			BUG();
+		from_pte = pte_alloc_kernel(&init_mm, pmd, from_address);
+		if (!from_pte)
+			BUG();
+
+		to_pte = pte_alloc_kernel(&init_mm, pmd, to_address);
+		if (!to_pte)
+			BUG();
+
+		v6_user_fns.cpu_clear_user_page = v6_clear_user_page_aliasing;
+		v6_user_fns.cpu_copy_user_page = v6_copy_user_page_aliasing;
+	}
 
 	return 0;
 }