ARM: 5794/1: Flush the D-cache during copy_user_highpage()

The I and D caches for copy-on-write pages on processors with
write-allocate caches become incoherent causing problems on application
relying on CoW for text pages (dynamic linker relocating symbols in a
text page). This patch flushes the D-cache for such pages.

Cc: Nicolas Pitre <nico@fluxnic.net>
Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

arch/arm/mm/copypage-v6.c

@@ -41,6 +41,14 @@ static void v6_copy_user_highpage_nonaliasing(struct page *to,
 	kfrom = kmap_atomic(from, KM_USER0);
 	kto = kmap_atomic(to, KM_USER1);
 	copy_page(kto, kfrom);
+#ifdef CONFIG_HIGHMEM
+	/*
+	 * kmap_atomic() doesn't set the page virtual address, and
+	 * kunmap_atomic() takes care of cache flushing already.
+	 */
+	if (page_address(to) != NULL)
+#endif
+		__cpuc_flush_dcache_page(kto);
 	kunmap_atomic(kto, KM_USER1);
 	kunmap_atomic(kfrom, KM_USER0);
 }