initial_commit

1 files changed, 1001 insertions, 0 deletions

diff --git a/ipc/util.c b/ipc/util.c
new file mode 100644
index 00000000..5c0d2892
--- /dev/null
+++ b/ipc/util.c
@@ -0,0 +1,1001 @@
+/*
+ * linux/ipc/util.c
+ * Copyright (C) 1992 Krishna Balasubramanian
+ *
+ * Sep 1997 - Call suser() last after "normal" permission checks so we
+ *            get BSD style process accounting right.
+ *            Occurs in several places in the IPC code.
+ *            Chris Evans, <chris@ferret.lmh.ox.ac.uk>
+ * Nov 1999 - ipc helper functions, unified SMP locking
+ *	      Manfred Spraul <manfred@colorfullife.com>
+ * Oct 2002 - One lock per IPC id. RCU ipc_free for lock-free grow_ary().
+ *            Mingming Cao <cmm@us.ibm.com>
+ * Mar 2006 - support for audit of ipc object properties
+ *            Dustin Kirkland <dustin.kirkland@us.ibm.com>
+ * Jun 2006 - namespaces ssupport
+ *            OpenVZ, SWsoft Inc.
+ *            Pavel Emelianov <xemul@openvz.org>
+ */
+
+#include <linux/mm.h>
+#include <linux/shm.h>
+#include <linux/init.h>
+#include <linux/msg.h>
+#include <linux/vmalloc.h>
+#include <linux/slab.h>
+#include <linux/capability.h>
+#include <linux/highuid.h>
+#include <linux/security.h>
+#include <linux/rcupdate.h>
+#include <linux/workqueue.h>
+#include <linux/seq_file.h>
+#include <linux/proc_fs.h>
+#include <linux/audit.h>
+#include <linux/nsproxy.h>
+#include <linux/rwsem.h>
+#include <linux/memory.h>
+#include <linux/ipc_namespace.h>
+
+#include <asm/unistd.h>
+
+#include "util.h"
+
+struct ipc_proc_iface {
+	const char *path;
+	const char *header;
+	int ids;
+	int (*show)(struct seq_file *, void *);
+};
+
+#ifdef CONFIG_MEMORY_HOTPLUG
+
+static void ipc_memory_notifier(struct work_struct *work)
+{
+	ipcns_notify(IPCNS_MEMCHANGED);
+}
+
+static DECLARE_WORK(ipc_memory_wq, ipc_memory_notifier);
+
+
+static int ipc_memory_callback(struct notifier_block *self,
+				unsigned long action, void *arg)
+{
+	switch (action) {
+	case MEM_ONLINE:    /* memory successfully brought online */
+	case MEM_OFFLINE:   /* or offline: it's time to recompute msgmni */
+		/*
+		 * This is done by invoking the ipcns notifier chain with the
+		 * IPC_MEMCHANGED event.
+		 * In order not to keep the lock on the hotplug memory chain
+		 * for too long, queue a work item that will, when waken up,
+		 * activate the ipcns notification chain.
+		 * No need to keep several ipc work items on the queue.
+		 */
+		if (!work_pending(&ipc_memory_wq))
+			schedule_work(&ipc_memory_wq);
+		break;
+	case MEM_GOING_ONLINE:
+	case MEM_GOING_OFFLINE:
+	case MEM_CANCEL_ONLINE:
+	case MEM_CANCEL_OFFLINE:
+	default:
+		break;
+	}
+
+	return NOTIFY_OK;
+}
+
+#endif /* CONFIG_MEMORY_HOTPLUG */
+
+/**
+ *	ipc_init	-	initialise IPC subsystem
+ *
+ *	The various system5 IPC resources (semaphores, messages and shared
+ *	memory) are initialised
+ *	A callback routine is registered into the memory hotplug notifier
+ *	chain: since msgmni scales to lowmem this callback routine will be
+ *	called upon successful memory add / remove to recompute msmgni.
+ */
+ 
+static int __init ipc_init(void)
+{
+	sem_init();
+	msg_init();
+	shm_init();
+	hotplug_memory_notifier(ipc_memory_callback, IPC_CALLBACK_PRI);
+	register_ipcns_notifier(&init_ipc_ns);
+	return 0;
+}
+__initcall(ipc_init);
+
+/**
+ *	ipc_init_ids		-	initialise IPC identifiers
+ *	@ids: Identifier set
+ *
+ *	Set up the sequence range to use for the ipc identifier range (limited
+ *	below IPCMNI) then initialise the ids idr.
+ */
+ 
+void ipc_init_ids(struct ipc_ids *ids)
+{
+	init_rwsem(&ids->rw_mutex);
+
+	ids->in_use = 0;
+	ids->seq = 0;
+	{
+		int seq_limit = INT_MAX/SEQ_MULTIPLIER;
+		if (seq_limit > USHRT_MAX)
+			ids->seq_max = USHRT_MAX;
+		 else
+		 	ids->seq_max = seq_limit;
+	}
+
+	idr_init(&ids->ipcs_idr);
+}
+
+#ifdef CONFIG_PROC_FS
+static const struct file_operations sysvipc_proc_fops;
+/**
+ *	ipc_init_proc_interface	-  Create a proc interface for sysipc types using a seq_file interface.
+ *	@path: Path in procfs
+ *	@header: Banner to be printed at the beginning of the file.
+ *	@ids: ipc id table to iterate.
+ *	@show: show routine.
+ */
+void __init ipc_init_proc_interface(const char *path, const char *header,
+		int ids, int (*show)(struct seq_file *, void *))
+{
+	struct proc_dir_entry *pde;
+	struct ipc_proc_iface *iface;
+
+	iface = kmalloc(sizeof(*iface), GFP_KERNEL);
+	if (!iface)
+		return;
+	iface->path	= path;
+	iface->header	= header;
+	iface->ids	= ids;
+	iface->show	= show;
+
+	pde = proc_create_data(path,
+			       S_IRUGO,        /* world readable */
+			       NULL,           /* parent dir */
+			       &sysvipc_proc_fops,
+			       iface);
+	if (!pde) {
+		kfree(iface);
+	}
+}
+#endif
+
+/**
+ *	ipc_findkey	-	find a key in an ipc identifier set	
+ *	@ids: Identifier set
+ *	@key: The key to find
+ *	
+ *	Requires ipc_ids.rw_mutex locked.
+ *	Returns the LOCKED pointer to the ipc structure if found or NULL
+ *	if not.
+ *	If key is found ipc points to the owning ipc structure
+ */
+ 
+static struct kern_ipc_perm *ipc_findkey(struct ipc_ids *ids, key_t key)
+{
+	struct kern_ipc_perm *ipc;
+	int next_id;
+	int total;
+
+	for (total = 0, next_id = 0; total < ids->in_use; next_id++) {
+		ipc = idr_find(&ids->ipcs_idr, next_id);
+
+		if (ipc == NULL)
+			continue;
+
+		if (ipc->key != key) {
+			total++;
+			continue;
+		}
+
+		ipc_lock_by_ptr(ipc);
+		return ipc;
+	}
+
+	return NULL;
+}
+
+/**
+ *	ipc_get_maxid 	-	get the last assigned id
+ *	@ids: IPC identifier set
+ *
+ *	Called with ipc_ids.rw_mutex held.
+ */
+
+int ipc_get_maxid(struct ipc_ids *ids)
+{
+	struct kern_ipc_perm *ipc;
+	int max_id = -1;
+	int total, id;
+
+	if (ids->in_use == 0)
+		return -1;
+
+	if (ids->in_use == IPCMNI)
+		return IPCMNI - 1;
+
+	/* Look for the last assigned id */
+	total = 0;
+	for (id = 0; id < IPCMNI && total < ids->in_use; id++) {
+		ipc = idr_find(&ids->ipcs_idr, id);
+		if (ipc != NULL) {
+			max_id = id;
+			total++;
+		}
+	}
+	return max_id;
+}
+
+/**
+ *	ipc_addid 	-	add an IPC identifier
+ *	@ids: IPC identifier set
+ *	@new: new IPC permission set
+ *	@size: limit for the number of used ids
+ *
+ *	Add an entry 'new' to the IPC ids idr. The permissions object is
+ *	initialised and the first free entry is set up and the id assigned
+ *	is returned. The 'new' entry is returned in a locked state on success.
+ *	On failure the entry is not locked and a negative err-code is returned.
+ *
+ *	Called with ipc_ids.rw_mutex held as a writer.
+ */
+ 
+int ipc_addid(struct ipc_ids* ids, struct kern_ipc_perm* new, int size)
+{
+	uid_t euid;
+	gid_t egid;
+	int id, err;
+
+	if (size > IPCMNI)
+		size = IPCMNI;
+
+	if (ids->in_use >= size)
+		return -ENOSPC;
+
+	spin_lock_init(&new->lock);
+	new->deleted = 0;
+	rcu_read_lock();
+	spin_lock(&new->lock);
+
+	err = idr_get_new(&ids->ipcs_idr, new, &id);
+	if (err) {
+		spin_unlock(&new->lock);
+		rcu_read_unlock();
+		return err;
+	}
+
+	ids->in_use++;
+
+	current_euid_egid(&euid, &egid);
+	new->cuid = new->uid = euid;
+	new->gid = new->cgid = egid;
+
+	new->seq = ids->seq++;
+	if(ids->seq > ids->seq_max)
+		ids->seq = 0;
+
+	new->id = ipc_buildid(id, new->seq);
+	return id;
+}
+
+/**
+ *	ipcget_new	-	create a new ipc object
+ *	@ns: namespace
+ *	@ids: IPC identifer set
+ *	@ops: the actual creation routine to call
+ *	@params: its parameters
+ *
+ *	This routine is called by sys_msgget, sys_semget() and sys_shmget()
+ *	when the key is IPC_PRIVATE.
+ */
+static int ipcget_new(struct ipc_namespace *ns, struct ipc_ids *ids,
+		struct ipc_ops *ops, struct ipc_params *params)
+{
+	int err;
+retry:
+	err = idr_pre_get(&ids->ipcs_idr, GFP_KERNEL);
+
+	if (!err)
+		return -ENOMEM;
+
+	down_write(&ids->rw_mutex);
+	err = ops->getnew(ns, params);
+	up_write(&ids->rw_mutex);
+
+	if (err == -EAGAIN)
+		goto retry;
+
+	return err;
+}
+
+/**
+ *	ipc_check_perms	-	check security and permissions for an IPC
+ *	@ns: IPC namespace
+ *	@ipcp: ipc permission set
+ *	@ops: the actual security routine to call
+ *	@params: its parameters
+ *
+ *	This routine is called by sys_msgget(), sys_semget() and sys_shmget()
+ *      when the key is not IPC_PRIVATE and that key already exists in the
+ *      ids IDR.
+ *
+ *	On success, the IPC id is returned.
+ *
+ *	It is called with ipc_ids.rw_mutex and ipcp->lock held.
+ */
+static int ipc_check_perms(struct ipc_namespace *ns,
+			   struct kern_ipc_perm *ipcp,
+			   struct ipc_ops *ops,
+			   struct ipc_params *params)
+{
+	int err;
+
+	if (ipcperms(ns, ipcp, params->flg))
+		err = -EACCES;
+	else {
+		err = ops->associate(ipcp, params->flg);
+		if (!err)
+			err = ipcp->id;
+	}
+
+	return err;
+}
+
+/**
+ *	ipcget_public	-	get an ipc object or create a new one
+ *	@ns: namespace
+ *	@ids: IPC identifer set
+ *	@ops: the actual creation routine to call
+ *	@params: its parameters
+ *
+ *	This routine is called by sys_msgget, sys_semget() and sys_shmget()
+ *	when the key is not IPC_PRIVATE.
+ *	It adds a new entry if the key is not found and does some permission
+ *      / security checkings if the key is found.
+ *
+ *	On success, the ipc id is returned.
+ */
+static int ipcget_public(struct ipc_namespace *ns, struct ipc_ids *ids,
+		struct ipc_ops *ops, struct ipc_params *params)
+{
+	struct kern_ipc_perm *ipcp;
+	int flg = params->flg;
+	int err;
+retry:
+	err = idr_pre_get(&ids->ipcs_idr, GFP_KERNEL);
+
+	/*
+	 * Take the lock as a writer since we are potentially going to add
+	 * a new entry + read locks are not "upgradable"
+	 */
+	down_write(&ids->rw_mutex);
+	ipcp = ipc_findkey(ids, params->key);
+	if (ipcp == NULL) {
+		/* key not used */
+		if (!(flg & IPC_CREAT))
+			err = -ENOENT;
+		else if (!err)
+			err = -ENOMEM;
+		else
+			err = ops->getnew(ns, params);
+	} else {
+		/* ipc object has been locked by ipc_findkey() */
+
+		if (flg & IPC_CREAT && flg & IPC_EXCL)
+			err = -EEXIST;
+		else {
+			err = 0;
+			if (ops->more_checks)
+				err = ops->more_checks(ipcp, params);
+			if (!err)
+				/*
+				 * ipc_check_perms returns the IPC id on
+				 * success
+				 */
+				err = ipc_check_perms(ns, ipcp, ops, params);
+		}
+		ipc_unlock(ipcp);
+	}
+	up_write(&ids->rw_mutex);
+
+	if (err == -EAGAIN)
+		goto retry;
+
+	return err;
+}
+
+
+/**
+ *	ipc_rmid	-	remove an IPC identifier
+ *	@ids: IPC identifier set
+ *	@ipcp: ipc perm structure containing the identifier to remove
+ *
+ *	ipc_ids.rw_mutex (as a writer) and the spinlock for this ID are held
+ *	before this function is called, and remain locked on the exit.
+ */
+ 
+void ipc_rmid(struct ipc_ids *ids, struct kern_ipc_perm *ipcp)
+{
+	int lid = ipcid_to_idx(ipcp->id);
+
+	idr_remove(&ids->ipcs_idr, lid);
+
+	ids->in_use--;
+
+	ipcp->deleted = 1;
+
+	return;
+}
+
+/**
+ *	ipc_alloc	-	allocate ipc space
+ *	@size: size desired
+ *
+ *	Allocate memory from the appropriate pools and return a pointer to it.
+ *	NULL is returned if the allocation fails
+ */
+ 
+void* ipc_alloc(int size)
+{
+	void* out;
+	if(size > PAGE_SIZE)
+		out = vmalloc(size);
+	else
+		out = kmalloc(size, GFP_KERNEL);
+	return out;
+}
+
+/**
+ *	ipc_free        -       free ipc space
+ *	@ptr: pointer returned by ipc_alloc
+ *	@size: size of block
+ *
+ *	Free a block created with ipc_alloc(). The caller must know the size
+ *	used in the allocation call.
+ */
+
+void ipc_free(void* ptr, int size)
+{
+	if(size > PAGE_SIZE)
+		vfree(ptr);
+	else
+		kfree(ptr);
+}
+
+/*
+ * rcu allocations:
+ * There are three headers that are prepended to the actual allocation:
+ * - during use: ipc_rcu_hdr.
+ * - during the rcu grace period: ipc_rcu_grace.
+ * - [only if vmalloc]: ipc_rcu_sched.
+ * Their lifetime doesn't overlap, thus the headers share the same memory.
+ * Unlike a normal union, they are right-aligned, thus some container_of
+ * forward/backward casting is necessary:
+ */
+struct ipc_rcu_hdr
+{
+	int refcount;
+	int is_vmalloc;
+	void *data[0];
+};
+
+
+struct ipc_rcu_grace
+{
+	struct rcu_head rcu;
+	/* "void *" makes sure alignment of following data is sane. */
+	void *data[0];
+};
+
+struct ipc_rcu_sched
+{
+	struct work_struct work;
+	/* "void *" makes sure alignment of following data is sane. */
+	void *data[0];
+};
+
+#define HDRLEN_KMALLOC		(sizeof(struct ipc_rcu_grace) > sizeof(struct ipc_rcu_hdr) ? \
+					sizeof(struct ipc_rcu_grace) : sizeof(struct ipc_rcu_hdr))
+#define HDRLEN_VMALLOC		(sizeof(struct ipc_rcu_sched) > HDRLEN_KMALLOC ? \
+					sizeof(struct ipc_rcu_sched) : HDRLEN_KMALLOC)
+
+static inline int rcu_use_vmalloc(int size)
+{
+	/* Too big for a single page? */
+	if (HDRLEN_KMALLOC + size > PAGE_SIZE)
+		return 1;
+	return 0;
+}
+
+/**
+ *	ipc_rcu_alloc	-	allocate ipc and rcu space 
+ *	@size: size desired
+ *
+ *	Allocate memory for the rcu header structure +  the object.
+ *	Returns the pointer to the object.
+ *	NULL is returned if the allocation fails. 
+ */
+ 
+void* ipc_rcu_alloc(int size)
+{
+	void* out;
+	/* 
+	 * We prepend the allocation with the rcu struct, and
+	 * workqueue if necessary (for vmalloc). 
+	 */
+	if (rcu_use_vmalloc(size)) {
+		out = vmalloc(HDRLEN_VMALLOC + size);
+		if (out) {
+			out += HDRLEN_VMALLOC;
+			container_of(out, struct ipc_rcu_hdr, data)->is_vmalloc = 1;
+			container_of(out, struct ipc_rcu_hdr, data)->refcount = 1;
+		}
+	} else {
+		out = kmalloc(HDRLEN_KMALLOC + size, GFP_KERNEL);
+		if (out) {
+			out += HDRLEN_KMALLOC;
+			container_of(out, struct ipc_rcu_hdr, data)->is_vmalloc = 0;
+			container_of(out, struct ipc_rcu_hdr, data)->refcount = 1;
+		}
+	}
+
+	return out;
+}
+
+void ipc_rcu_getref(void *ptr)
+{
+	container_of(ptr, struct ipc_rcu_hdr, data)->refcount++;
+}
+
+static void ipc_do_vfree(struct work_struct *work)
+{
+	vfree(container_of(work, struct ipc_rcu_sched, work));
+}
+
+/**
+ * ipc_schedule_free - free ipc + rcu space
+ * @head: RCU callback structure for queued work
+ * 
+ * Since RCU callback function is called in bh,
+ * we need to defer the vfree to schedule_work().
+ */
+static void ipc_schedule_free(struct rcu_head *head)
+{
+	struct ipc_rcu_grace *grace;
+	struct ipc_rcu_sched *sched;
+
+	grace = container_of(head, struct ipc_rcu_grace, rcu);
+	sched = container_of(&(grace->data[0]), struct ipc_rcu_sched,
+				data[0]);
+
+	INIT_WORK(&sched->work, ipc_do_vfree);
+	schedule_work(&sched->work);
+}
+
+/**
+ * ipc_immediate_free - free ipc + rcu space
+ * @head: RCU callback structure that contains pointer to be freed
+ *
+ * Free from the RCU callback context.
+ */
+static void ipc_immediate_free(struct rcu_head *head)
+{
+	struct ipc_rcu_grace *free =
+		container_of(head, struct ipc_rcu_grace, rcu);
+	kfree(free);
+}
+
+void ipc_rcu_putref(void *ptr)
+{
+	if (--container_of(ptr, struct ipc_rcu_hdr, data)->refcount > 0)
+		return;
+
+	if (container_of(ptr, struct ipc_rcu_hdr, data)->is_vmalloc) {
+		call_rcu(&container_of(ptr, struct ipc_rcu_grace, data)->rcu,
+				ipc_schedule_free);
+	} else {
+		call_rcu(&container_of(ptr, struct ipc_rcu_grace, data)->rcu,
+				ipc_immediate_free);
+	}
+}
+
+/**
+ *	ipcperms	-	check IPC permissions
+ *	@ns: IPC namespace
+ *	@ipcp: IPC permission set
+ *	@flag: desired permission set.
+ *
+ *	Check user, group, other permissions for access
+ *	to ipc resources. return 0 if allowed
+ *
+ * 	@flag will most probably be 0 or S_...UGO from <linux/stat.h>
+ */
+ 
+int ipcperms(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp, short flag)
+{
+	uid_t euid = current_euid();
+	int requested_mode, granted_mode;
+
+	audit_ipc_obj(ipcp);
+	requested_mode = (flag >> 6) | (flag >> 3) | flag;
+	granted_mode = ipcp->mode;
+	if (euid == ipcp->cuid ||
+	    euid == ipcp->uid)
+		granted_mode >>= 6;
+	else if (in_group_p(ipcp->cgid) || in_group_p(ipcp->gid))
+		granted_mode >>= 3;
+	/* is there some bit set in requested_mode but not in granted_mode? */
+	if ((requested_mode & ~granted_mode & 0007) && 
+	    !ns_capable(ns->user_ns, CAP_IPC_OWNER))
+		return -1;
+
+	return security_ipc_permission(ipcp, flag);
+}
+
+/*
+ * Functions to convert between the kern_ipc_perm structure and the
+ * old/new ipc_perm structures
+ */
+
+/**
+ *	kernel_to_ipc64_perm	-	convert kernel ipc permissions to user
+ *	@in: kernel permissions
+ *	@out: new style IPC permissions
+ *
+ *	Turn the kernel object @in into a set of permissions descriptions
+ *	for returning to userspace (@out).
+ */
+ 
+
+void kernel_to_ipc64_perm (struct kern_ipc_perm *in, struct ipc64_perm *out)
+{
+	out->key	= in->key;
+	out->uid	= in->uid;
+	out->gid	= in->gid;
+	out->cuid	= in->cuid;
+	out->cgid	= in->cgid;
+	out->mode	= in->mode;
+	out->seq	= in->seq;
+}
+
+/**
+ *	ipc64_perm_to_ipc_perm	-	convert new ipc permissions to old
+ *	@in: new style IPC permissions
+ *	@out: old style IPC permissions
+ *
+ *	Turn the new style permissions object @in into a compatibility
+ *	object and store it into the @out pointer.
+ */
+ 
+void ipc64_perm_to_ipc_perm (struct ipc64_perm *in, struct ipc_perm *out)
+{
+	out->key	= in->key;
+	SET_UID(out->uid, in->uid);
+	SET_GID(out->gid, in->gid);
+	SET_UID(out->cuid, in->cuid);
+	SET_GID(out->cgid, in->cgid);
+	out->mode	= in->mode;
+	out->seq	= in->seq;
+}
+
+/**
+ * ipc_lock - Lock an ipc structure without rw_mutex held
+ * @ids: IPC identifier set
+ * @id: ipc id to look for
+ *
+ * Look for an id in the ipc ids idr and lock the associated ipc object.
+ *
+ * The ipc object is locked on exit.
+ */
+
+struct kern_ipc_perm *ipc_lock(struct ipc_ids *ids, int id)
+{
+	struct kern_ipc_perm *out;
+	int lid = ipcid_to_idx(id);
+
+	rcu_read_lock();
+	out = idr_find(&ids->ipcs_idr, lid);
+	if (out == NULL) {
+		rcu_read_unlock();
+		return ERR_PTR(-EINVAL);
+	}
+
+	spin_lock(&out->lock);
+	
+	/* ipc_rmid() may have already freed the ID while ipc_lock
+	 * was spinning: here verify that the structure is still valid
+	 */
+	if (out->deleted) {
+		spin_unlock(&out->lock);
+		rcu_read_unlock();
+		return ERR_PTR(-EINVAL);
+	}
+
+	return out;
+}
+
+struct kern_ipc_perm *ipc_lock_check(struct ipc_ids *ids, int id)
+{
+	struct kern_ipc_perm *out;
+
+	out = ipc_lock(ids, id);
+	if (IS_ERR(out))
+		return out;
+
+	if (ipc_checkid(out, id)) {
+		ipc_unlock(out);
+		return ERR_PTR(-EIDRM);
+	}
+
+	return out;
+}
+
+/**
+ * ipcget - Common sys_*get() code
+ * @ns : namsepace
+ * @ids : IPC identifier set
+ * @ops : operations to be called on ipc object creation, permission checks
+ *        and further checks
+ * @params : the parameters needed by the previous operations.
+ *
+ * Common routine called by sys_msgget(), sys_semget() and sys_shmget().
+ */
+int ipcget(struct ipc_namespace *ns, struct ipc_ids *ids,
+			struct ipc_ops *ops, struct ipc_params *params)
+{
+	if (params->key == IPC_PRIVATE)
+		return ipcget_new(ns, ids, ops, params);
+	else
+		return ipcget_public(ns, ids, ops, params);
+}
+
+/**
+ * ipc_update_perm - update the permissions of an IPC.
+ * @in:  the permission given as input.
+ * @out: the permission of the ipc to set.
+ */
+void ipc_update_perm(struct ipc64_perm *in, struct kern_ipc_perm *out)
+{
+	out->uid = in->uid;
+	out->gid = in->gid;
+	out->mode = (out->mode & ~S_IRWXUGO)
+		| (in->mode & S_IRWXUGO);
+}
+
+/**
+ * ipcctl_pre_down - retrieve an ipc and check permissions for some IPC_XXX cmd
+ * @ns:  the ipc namespace
+ * @ids:  the table of ids where to look for the ipc
+ * @id:   the id of the ipc to retrieve
+ * @cmd:  the cmd to check
+ * @perm: the permission to set
+ * @extra_perm: one extra permission parameter used by msq
+ *
+ * This function does some common audit and permissions check for some IPC_XXX
+ * cmd and is called from semctl_down, shmctl_down and msgctl_down.
+ * It must be called without any lock held and
+ *  - retrieves the ipc with the given id in the given table.
+ *  - performs some audit and permission check, depending on the given cmd
+ *  - returns the ipc with both ipc and rw_mutex locks held in case of success
+ *    or an err-code without any lock held otherwise.
+ */
+struct kern_ipc_perm *ipcctl_pre_down(struct ipc_namespace *ns,
+				      struct ipc_ids *ids, int id, int cmd,
+				      struct ipc64_perm *perm, int extra_perm)
+{
+	struct kern_ipc_perm *ipcp;
+	uid_t euid;
+	int err;
+
+	down_write(&ids->rw_mutex);
+	ipcp = ipc_lock_check(ids, id);
+	if (IS_ERR(ipcp)) {
+		err = PTR_ERR(ipcp);
+		goto out_up;
+	}
+
+	audit_ipc_obj(ipcp);
+	if (cmd == IPC_SET)
+		audit_ipc_set_perm(extra_perm, perm->uid,
+					 perm->gid, perm->mode);
+
+	euid = current_euid();
+	if (euid == ipcp->cuid || euid == ipcp->uid  ||
+	    ns_capable(ns->user_ns, CAP_SYS_ADMIN))
+		return ipcp;
+
+	err = -EPERM;
+	ipc_unlock(ipcp);
+out_up:
+	up_write(&ids->rw_mutex);
+	return ERR_PTR(err);
+}
+
+#ifdef __ARCH_WANT_IPC_PARSE_VERSION
+
+
+/**
+ *	ipc_parse_version	-	IPC call version
+ *	@cmd: pointer to command
+ *
+ *	Return IPC_64 for new style IPC and IPC_OLD for old style IPC. 
+ *	The @cmd value is turned from an encoding command and version into
+ *	just the command code.
+ */
+ 
+int ipc_parse_version (int *cmd)
+{
+	if (*cmd & IPC_64) {
+		*cmd ^= IPC_64;
+		return IPC_64;
+	} else {
+		return IPC_OLD;
+	}
+}
+
+#endif /* __ARCH_WANT_IPC_PARSE_VERSION */
+
+#ifdef CONFIG_PROC_FS
+struct ipc_proc_iter {
+	struct ipc_namespace *ns;
+	struct ipc_proc_iface *iface;
+};
+
+/*
+ * This routine locks the ipc structure found at least at position pos.
+ */
+static struct kern_ipc_perm *sysvipc_find_ipc(struct ipc_ids *ids, loff_t pos,
+					      loff_t *new_pos)
+{
+	struct kern_ipc_perm *ipc;
+	int total, id;
+
+	total = 0;
+	for (id = 0; id < pos && total < ids->in_use; id++) {
+		ipc = idr_find(&ids->ipcs_idr, id);
+		if (ipc != NULL)
+			total++;
+	}
+
+	if (total >= ids->in_use)
+		return NULL;
+
+	for ( ; pos < IPCMNI; pos++) {
+		ipc = idr_find(&ids->ipcs_idr, pos);
+		if (ipc != NULL) {
+			*new_pos = pos + 1;
+			ipc_lock_by_ptr(ipc);
+			return ipc;
+		}
+	}
+
+	/* Out of range - return NULL to terminate iteration */
+	return NULL;
+}
+
+static void *sysvipc_proc_next(struct seq_file *s, void *it, loff_t *pos)
+{
+	struct ipc_proc_iter *iter = s->private;
+	struct ipc_proc_iface *iface = iter->iface;
+	struct kern_ipc_perm *ipc = it;
+
+	/* If we had an ipc id locked before, unlock it */
+	if (ipc && ipc != SEQ_START_TOKEN)
+		ipc_unlock(ipc);
+
+	return sysvipc_find_ipc(&iter->ns->ids[iface->ids], *pos, pos);
+}
+
+/*
+ * File positions: pos 0 -> header, pos n -> ipc id = n - 1.
+ * SeqFile iterator: iterator value locked ipc pointer or SEQ_TOKEN_START.
+ */
+static void *sysvipc_proc_start(struct seq_file *s, loff_t *pos)
+{
+	struct ipc_proc_iter *iter = s->private;
+	struct ipc_proc_iface *iface = iter->iface;
+	struct ipc_ids *ids;
+
+	ids = &iter->ns->ids[iface->ids];
+
+	/*
+	 * Take the lock - this will be released by the corresponding
+	 * call to stop().
+	 */
+	down_read(&ids->rw_mutex);
+
+	/* pos < 0 is invalid */
+	if (*pos < 0)
+		return NULL;
+
+	/* pos == 0 means header */
+	if (*pos == 0)
+		return SEQ_START_TOKEN;
+
+	/* Find the (pos-1)th ipc */
+	return sysvipc_find_ipc(ids, *pos - 1, pos);
+}
+
+static void sysvipc_proc_stop(struct seq_file *s, void *it)
+{
+	struct kern_ipc_perm *ipc = it;
+	struct ipc_proc_iter *iter = s->private;
+	struct ipc_proc_iface *iface = iter->iface;
+	struct ipc_ids *ids;
+
+	/* If we had a locked structure, release it */
+	if (ipc && ipc != SEQ_START_TOKEN)
+		ipc_unlock(ipc);
+
+	ids = &iter->ns->ids[iface->ids];
+	/* Release the lock we took in start() */
+	up_read(&ids->rw_mutex);
+}
+
+static int sysvipc_proc_show(struct seq_file *s, void *it)
+{
+	struct ipc_proc_iter *iter = s->private;
+	struct ipc_proc_iface *iface = iter->iface;
+
+	if (it == SEQ_START_TOKEN)
+		return seq_puts(s, iface->header);
+
+	return iface->show(s, it);
+}
+
+static const struct seq_operations sysvipc_proc_seqops = {
+	.start = sysvipc_proc_start,
+	.stop  = sysvipc_proc_stop,
+	.next  = sysvipc_proc_next,
+	.show  = sysvipc_proc_show,
+};
+
+static int sysvipc_proc_open(struct inode *inode, struct file *file)
+{
+	int ret;
+	struct seq_file *seq;
+	struct ipc_proc_iter *iter;
+
+	ret = -ENOMEM;
+	iter = kmalloc(sizeof(*iter), GFP_KERNEL);
+	if (!iter)
+		goto out;
+
+	ret = seq_open(file, &sysvipc_proc_seqops);
+	if (ret)
+		goto out_kfree;
+
+	seq = file->private_data;
+	seq->private = iter;
+
+	iter->iface = PDE(inode)->data;
+	iter->ns    = get_ipc_ns(current->nsproxy->ipc_ns);
+out:
+	return ret;
+out_kfree:
+	kfree(iter);
+	goto out;
+}
+
+static int sysvipc_proc_release(struct inode *inode, struct file *file)
+{
+	struct seq_file *seq = file->private_data;
+	struct ipc_proc_iter *iter = seq->private;
+	put_ipc_ns(iter->ns);
+	return seq_release_private(inode, file);
+}
+
+static const struct file_operations sysvipc_proc_fops = {
+	.open    = sysvipc_proc_open,
+	.read    = seq_read,
+	.llseek  = seq_lseek,
+	.release = sysvipc_proc_release,
+};
+#endif /* CONFIG_PROC_FS */