x86/mm/dump_pagetables: Generalize address normalization

Modify normalize_addr to handle different sizes of virtual address
space.

It's preparation for enabling 5-level paging.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-arch@vger.kernel.org
Cc: linux-mm@kvack.org
Link: http://lkml.kernel.org/r/20170716225954.74185-2-kirill.shutemov@linux.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/mm/dump_pagetables.c

@@ -188,11 +188,12 @@ static void printk_prot(struct seq_file *m, pgprot_t prot, int level, bool dmsg)
  */
 static unsigned long normalize_addr(unsigned long u)
 {
-#ifdef CONFIG_X86_64
-	return (signed long)(u << 16) >> 16;
-#else
-	return u;
-#endif
+	int shift;
+	if (!IS_ENABLED(CONFIG_X86_64))
+		return u;
+
+	shift = 64 - (__VIRTUAL_MASK_SHIFT + 1);
+	return (signed long)(u << shift) >> shift;
 }
 
 /*