s390/chsc: make headers usable

Make sure that exported headers are save to be included by userspace
exploiting /dev/chsc.
Reported-by: NMichael Holzheu <holzheu@linux.vnet.ibm.com>
Signed-off-by: NSebastian Ott <sebott@linux.vnet.ibm.com>
Signed-off-by: NMartin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/include/asm/chpid.h

 /*
- *    Copyright IBM Corp. 2007
+ *    Copyright IBM Corp. 2007, 2012
  *    Author(s): Peter Oberparleiter <peter.oberparleiter@de.ibm.com>
  */
 
@@ -12,10 +12,10 @@
 #define __MAX_CHPID 255
 
 struct chp_id {
-	u8 reserved1;
-	u8 cssid;
-	u8 reserved2;
-	u8 id;
+	__u8 reserved1;
+	__u8 cssid;
+	__u8 reserved2;
+	__u8 id;
 } __attribute__((packed));
 
 #ifdef __KERNEL__

arch/s390/include/asm/chsc.h

 /*
  * ioctl interface for /dev/chsc
  *
- * Copyright IBM Corp. 2008
+ * Copyright IBM Corp. 2008, 2012
  * Author(s): Cornelia Huck <cornelia.huck@de.ibm.com>
  */
 
@@ -9,9 +9,12 @@
 #define _ASM_CHSC_H
 
 #include <linux/types.h>
+#include <linux/ioctl.h>
 #include <asm/chpid.h>
 #include <asm/schid.h>
 
+#define CHSC_SIZE 0x1000
+
 struct chsc_async_header {
 	__u16 length;
 	__u16 code;
@@ -23,15 +26,14 @@ struct chsc_async_header {
 
 struct chsc_async_area {
 	struct chsc_async_header header;
-	__u8 data[PAGE_SIZE - 16 /* size of chsc_async_header */];
+	__u8 data[CHSC_SIZE - sizeof(struct chsc_async_header)];
 } __attribute__ ((packed));
 
-
 struct chsc_response_struct {
 	__u16 length;
 	__u16 code;
 	__u32 parms;
-	__u8 data[PAGE_SIZE - 8];
+	__u8 data[CHSC_SIZE - 2 * sizeof(__u16) - sizeof(__u32)];
 } __attribute__ ((packed));
 
 struct chsc_chp_cd {