First of several commits to allow kernel System V IPC data structures

to be modified and extended without breaking the user space ABI:

Define _kernel wrapper data structures for the user-exposed data
structures that current server as the internal data structures for
the implementation:

- struct msqid_kernel wraps struct msqid_ds.
- struct semid_kernel wraps truct semid_ds.
- struct shmid_kernel wraps struct shmid_ds.
- Don't expose extern definition 'shmsegs' outside of sysv_shm.c.

Submitted by:	Dandekar Hrishikesh <rishi_dandekar at sbcglobal dot net>
Obtained from:	TrustedBSD Project
Sponsored by:	DARPA, SPAWAR, McAfee Research

sys/sys/msg.h

@@ -120,6 +120,20 @@ struct msginfo {
 };
 extern struct msginfo	msginfo;
 
+/*
+ * Kernel wrapper for the user-level structure.
+ */
+struct msqid_kernel {
+	/*
+	 * Data structure exposed to user space.
+	 */
+	struct	msqid_ds u;
+
+	/*
+	 * Kernel-private components of the message queue.
+	 */
+};
+
 #else /* !_KERNEL */
 
 __BEGIN_DECLS

sys/sys/sem.h

@@ -84,6 +84,13 @@ struct seminfo {
 };
 extern struct seminfo	seminfo;
 
+/*
+ * Kernel wrapper for the user-level structure
+ */
+struct semid_kernel {
+	struct	semid_ds u;
+};
+
 /* internal "mode" bits */
 #define	SEM_ALLOC	01000	/* semaphore is allocated */
 #define	SEM_DEST	02000	/* semaphore will be destroyed on last detach */

sys/sys/shm.h

@@ -83,8 +83,16 @@ struct shminfo {
 		shmseg,		/* max shared memory segments per process */
 		shmall;		/* max amount of shared memory (pages) */
 };
+
+/* 
+ * Add a kernel wrapper to the shmid_ds struct so that private info (like the
+ * MAC label) can be added to it, without changing the user interface.
+ */
+struct shmid_kernel {
+	struct shmid_ds u;
+};
+
 extern struct shminfo	shminfo;
-extern struct shmid_ds	*shmsegs;
 
 struct shm_info {
 	int used_ids;