3  * linux/ipc/util.c
8  *            Occurs in several places in the IPC code.
10  * Nov 1999 - ipc helper functions, unified SMP locking
12  * Oct 2002 - One lock per IPC id. RCU ipc_free for lock-free grow_ary().
14  * Mar 2006 - support for audit of ipc object properties
20  * General sysv ipc locking scheme:
22  *          obtain the ipc object (kern_ipc_perm) by looking up the id in an idr
28  *	      acquire the ipc lock (kern_ipc_perm.lock) through
35  *	    drop the ipc lock, through ipc_unlock_object().
39  *	- creating, removing and iterating the existing entries in ipc
81  * ipc_init - initialise ipc subsystem
83  * The various sysv ipc resources (semaphores, messages and shared
109  * ipc_init_ids	- initialise ipc identifiers
110  * @ids: ipc identifier set
112  * Set up the sequence range to use for the ipc identifier range (limited
135  * @ids: ipc id table to iterate.
163  * ipc_findkey	- find a key in an ipc identifier set
164  * @ids: ipc identifier set
167  * Returns the locked pointer to the ipc structure if found or NULL
168  * otherwise. If key is found ipc points to the owning ipc structure
187  * Insert new IPC object into idr tree, and set sequence number and id
214 	 * and the lockless preparations for ipc operations can start.  in ipc_idr_alloc()
264  * ipc_addid - add an ipc identifier
265  * @ids: ipc identifier set
266  * @new: new ipc permission set
269  * Add an entry 'new' to the ipc ids idr. The permissions object is
330  * ipcget_new -	create a new ipc object
331  * @ns: ipc namespace
332  * @ids: ipc identifier set
351  * ipc_check_perms - check security and permissions for an ipc object
352  * @ns: ipc namespace
353  * @ipcp: ipc permission set
361  * On success, the ipc id is returned.
384  * ipcget_public - get an ipc object or create a new one
385  * @ns: ipc namespace
386  * @ids: ipc identifier set
395  * On success, the ipc id is returned.
417 		/* ipc object has been locked by ipc_findkey() */  in ipcget_public()
427 				 * ipc_check_perms returns the IPC id on  in ipcget_public()
440  * ipc_kht_remove - remove an ipc from the key hashtable
441  * @ids: ipc identifier set
442  * @ipcp: ipc perm structure containing the key to remove
456  * @ids: ipc identifier set
461  * Updating ids->max_idx is necessary when the current highest index ipc
463  * If no ipc object is allocated, then -1 is returned.
490  * ipc_rmid - remove an ipc identifier
491  * @ids: ipc identifier set
492  * @ipcp: ipc perm structure containing the identifier to remove
515  * ipc_set_key_private - switch the key of an existing ipc to IPC_PRIVATE
516  * @ids: ipc identifier set
517  * @ipcp: ipc perm structure containing the key to modify
543  * ipcperms - check ipc permissions
544  * @ns: ipc namespace
545  * @ipcp: ipc permission set
549  * to ipc resources. return 0 if allowed
580  * kernel_to_ipc64_perm	- convert kernel ipc permissions to user
582  * @out: new style ipc permissions
599  * ipc64_perm_to_ipc_perm - convert new ipc permissions to old
600  * @in: new style ipc permissions
601  * @out: old style ipc permissions
619  * @ids: ipc identifier set
620  * @id: ipc id to look for
622  * Look for an id in the ipc ids idr and return associated ipc object.
625  * The ipc object is *not* locked on exit.
641  * @ids: ipc identifier set
642  * @id: ipc id to look for
644  * Similar to ipc_obtain_object_idr() but also checks the ipc object
648  * The ipc object is *not* locked on exit.
666  * @ids: ipc identifier set
667  * @ops: operations to be called on ipc object creation, permission checks
683  * ipc_update_perm - update the permissions of an ipc object
685  * @out: the permission of the ipc to set.
703  * ipcctl_obtain_check - retrieve an ipc object and check permissions
704  * @ns:  ipc namespace
705  * @ids:  the table of ids where to look for the ipc
706  * @id:   the id of the ipc to retrieve
715  *   - retrieves the ipc object with the given id in the given table.
717  *   - returns a pointer to the ipc object or otherwise, the corresponding
753  * ipc_parse_version - ipc call version
756  * Return IPC_64 for new style IPC and IPC_OLD for old style IPC.
786  * sysvipc_find_ipc - Find and lock the ipc structure based on seq pos
787  * @ids: ipc identifier set
790  * The function finds an ipc structure, based on the sequence file
791  * position @pos. If there is no ipc structure at position @pos, then
795  * the found ipc structure.
798  * The function returns the found ipc structure, or NULL at EOF.
803 	struct kern_ipc_perm *ipc;  in sysvipc_find_ipc()  local
808 	ipc = idr_get_next(&ids->ipcs_idr, &tmpidx);  in sysvipc_find_ipc()
809 	if (ipc != NULL) {  in sysvipc_find_ipc()
811 		ipc_lock_object(ipc);  in sysvipc_find_ipc()
816 	return ipc;  in sysvipc_find_ipc()
823 	struct kern_ipc_perm *ipc = it;  in sysvipc_proc_next()  local
825 	/* If we had an ipc id locked before, unlock it */  in sysvipc_proc_next()
826 	if (ipc && ipc != SEQ_START_TOKEN)  in sysvipc_proc_next()
827 		ipc_unlock(ipc);  in sysvipc_proc_next()
835  * File positions: pos 0 -> header, pos n -> ipc idx = n - 1.
836  * SeqFile iterator: iterator value locked ipc pointer or SEQ_TOKEN_START.
860 	/* Otherwise return the correct ipc structure */  in sysvipc_proc_start()
866 	struct kern_ipc_perm *ipc = it;  in sysvipc_proc_stop()  local
872 	if (ipc && ipc != SEQ_START_TOKEN)  in sysvipc_proc_stop()
873 		ipc_unlock(ipc);  in sysvipc_proc_stop()