path: root/ipc/util.c

/*
 * 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/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 *);
};

struct ipc_namespace init_ipc_ns = {
	.kref = {
		.refcount	= ATOMIC_INIT(2),
	},
};

/**
 *	ipc_init	-	initialise IPC subsystem
 *
 *	The various system5 IPC resources (semaphores, messages and shared
 *	memory) are initialised
 */
 
static int __init ipc_init(void)
{
	sem_init();
	msg_init();
	shm_init();
	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 = create_proc_entry(path,
				S_IRUGO,        /* world readable */
				NULL            /* parent dir */);
	if (pde) {
		pde->data = iface;
		pde->proc_fops = &sysvipc_proc_fops;
	} else {
		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