sh: Fix mmap2 for handling differing PAGE_SIZEs.

mmap2 uses a fixed page shift of 12, regardless of the PAGE_SIZE setting.
Fix up the mmap2 code to add some sanity checks on the mapping, and to
update pgoff accordingly.

Error handling bits based on 4280e312
("frv: fix mmap2 error handling").
Signed-off-by: Toshinobu Sugioka <sugioka@itonet.co.jp>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>

arch/sh/kernel/sys_sh.c

@@ -63,6 +63,15 @@ asmlinkage long sys_mmap2(unsigned long addr, unsigned long len,
 	unsigned long prot, unsigned long flags,
 	unsigned long fd, unsigned long pgoff)
 {
+	/*
+	 * The shift for mmap2 is constant, regardless of PAGE_SIZE
+	 * setting.
+	 */
+	if (pgoff & ((1 << (PAGE_SHIFT - 12)) - 1))
+		return -EINVAL;
+
+	pgoff >>= PAGE_SHIFT - 12;
+
 	return do_mmap2(addr, len, prot, flags, fd, pgoff);
 }