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/*
 * 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 <manfreds@colorfullife.com>
 * Oct 2002 - One lock per IPC id. RCU ipc_free for lock-free grow_ary().
 *            Mingming Cao <cmm@us.ibm.com>
 */

#include <linux/config.h>
#include <linux/mm.h>
#include <linux/shm.h>
#include <linux/init.h>
#include <linux/msg.h>
#include <linux/smp_lock.h>
#include <linux/vmalloc.h>
#include <linux/slab.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 <asm/unistd.h>

#include "util.h"

struct ipc_proc_iface {
	const char *path;
	const char *header;
	struct ipc_ids *ids;
	int (*show)(struct seq_file *, void *);
};

/**
 *	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
 *	@size: Number of identifiers
 *
 *	Given a size for the ipc identifier range (limited below IPCMNI)
 *	set up the sequence range to use then allocate and initialise the
 *	array itself. 
 */
 
void __init ipc_init_ids(struct ipc_ids* ids, int size)
{
	int i;
	sema_init(&ids->sem,1);

	if(size > IPCMNI)
		size = IPCMNI;
	ids->in_use = 0;
	ids->max_id = -1;
	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;
	}

	ids->entries = ipc_rcu_alloc(sizeof(struct kern_ipc_perm *)*size +
				     sizeof(struct ipc_id_ary));

	if(ids->entries == NULL) {
		printk(KERN_ERR "ipc_init_ids() failed, ipc service disabled.\n");
		size = 0;
		ids->entries = &ids->nullentry;
	}
	ids->entries->size = size;
	for(i=0;i<size;i++)
		ids->entries->p[i] = NULL;
}

#ifdef CONFIG_PROC_FS
static 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,
				    struct ipc_ids *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.sem locked.
 *	Returns the identifier if found or -1 if not.
 */
 
int ipc_findkey(struct ipc_ids* ids, key_t key)
{
	int id;
	struct kern_ipc_perm* p;
	int max_id = ids->max_id;

	/*
	 * rcu_dereference() is not needed here
	 * since ipc_ids.sem is held
	 */
	for (id = 0; id <= max_id; id++) {
		p = ids->entries->p[id];
		if(p==NULL)
			continue;
		if (key == p->key)
			return id;
	}
	return -1;
}

/*
 * Requires ipc_ids.sem locked
 */
static int grow_ary(struct ipc_ids* ids, int newsize)
{
	struct ipc_id_ary* new;
	struct ipc_id_ary* old;
	int i;
	int size = ids->entries->size;

	if(newsize > IPCMNI)
		newsize = IPCMNI;
	if(newsize <= size)
		return newsize;

	new = ipc_rcu_alloc(sizeof(struct kern_ipc_perm *)*newsize +
			    sizeof(struct ipc_id_ary));
	if(new == NULL)
		return size;
	new->size = newsize;
	memcpy(new->p, ids->entries->p, sizeof(struct kern_ipc_perm *)*size +
					sizeof(struct ipc_id_ary));
	for(i=size;i<newsize;i++) {
		new->p[i] = NULL;
	}
	old = ids->entries;

	/*
	 * Use rcu_assign_pointer() to make sure the memcpyed contents
	 * of the new array are visible before the new array becomes visible.
	 */
	rcu_assign_pointer(ids->entries, new);

	ipc_rcu_putref(old);
	return newsize;
}

/**
 *	ipc_addid 	-	add an IPC identifier
 *	@ids: IPC identifier set
 *	@new: new IPC permission set
 *	@size: new size limit for the id array
 *
 *	Add an entry 'new' to the IPC arrays. The permissions object is
 *	initialised and the first free entry is set up and the id assigned
 *	is returned. The list is returned in a locked state on success.
 *	On failure the list is not locked and -1 is returned.
 *
 *	Called with ipc_ids.sem held.
 */
 
int ipc_addid(struct ipc_ids* ids, struct kern_ipc_perm* new, int size)
{
	int id;

	size = grow_ary(ids,size);

	/*
	 * rcu_dereference()() is not needed here since
	 * ipc_ids.sem is held
	 */
	for (id = 0; id < size; id++) {
		if(ids->entries->p[id] == NULL)
			goto found;
	}
	return -1;
found:
	ids->in_use++;
	if (id > ids->max_id)
		ids->max_id = id;

	new->cuid = new->uid = current->euid;
	new->gid = new->cgid = current->egid;

	new->seq = ids->seq++;
	if(ids->seq > ids->seq_max)
		ids->seq = 0;

	spin_lock_init(&new->lock);
	new->deleted = 0;
	rcu_read_lock();
	spin_lock(&new->lock);
	ids->entries->p[id] = new;
	return id;
}

/**
 *	ipc_rmid	-	remove an IPC identifier
 *	@ids: identifier set
 *	@id: Identifier to remove
 *
 *	The identifier must be valid, and in use. The kernel will panic if
 *	fed an invalid identifier. The entry is removed and internal
 *	variables recomputed. The object associated with the identifier
 *	is returned.
 *	ipc_ids.sem and the spinlock for this ID is hold before this function
 *	is called, and remain locked on the exit.
 */
 
struct kern_ipc_perm* ipc_rmid(struct ipc_ids* ids, int id)
{
	struct kern_ipc_perm* p;
	int lid = id % SEQ_MULTIPLIER;
	if(lid >= ids->entries->size)
		BUG();

	/* 
	 * do not need a rcu_dereference()() here to force ordering
	 * on Alpha, since the ipc_ids.sem is held.
	 */	
	p = ids->entries->p[lid];
	ids->entries->p[lid] = NULL;
	if(p==NULL)
		BUG();
	ids->in_use--;

	if (lid == ids->max_id) {
		do {
			lid--;
			if(lid == -1)
				break;