[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>

---
diff --git a/arch/mips/kernel/linux32.c b/arch/mips/kernel/linux32.c
index 1e8d248..013bc93 100644
--- a/arch/mips/kernel/linux32.c
+++ b/arch/mips/kernel/linux32.c
@@ -106,6 +106,10 @@
 	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);