[MIPS] sys_mmap2 offset argument should always be shifted 12, not PAGE_SHIFT.

This patch adjusts the offset argument passed into sys_mmap2 to be
always shifted 12, even when the native page size isn't 4K.  This is
what all existing userspace libraries expect.
    
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

---

arch/mips/kernel/linux32.c

@@ -106,6 +106,10 @@ sys32_mmap2(unsigned long addr, unsigned long len, unsigned long prot,
 	unsigned long error;
 
 	error = -EINVAL;
+	if (pgoff & (~PAGE_MASK >> 12))
+		goto out;
+	pgoff >>= PAGE_SHIFT-12;
+
 	if (!(flags & MAP_ANONYMOUS)) {
 		error = -EBADF;
 		file = fget(fd);

arch/mips/kernel/syscall.c

@@ -162,7 +162,10 @@ asmlinkage unsigned long
 sys_mmap2(unsigned long addr, unsigned long len, unsigned long prot,
           unsigned long flags, unsigned long fd, unsigned long pgoff)
 {
-	return do_mmap2(addr, len, prot, flags, fd, pgoff);
+	if (pgoff & (~PAGE_MASK >> 12))
+		return -EINVAL;
+
+	return do_mmap2(addr, len, prot, flags, fd, pgoff >> (PAGE_SHIFT-12));
 }
 
 save_static_function(sys_fork);