/* * 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 <asm/unistd.h> #include "util.h" /** *	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;} /** *	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;		} while (ids->entries->p[lid] == NULL);		ids->max_id = lid;	}	p->deleted = 1;	return p;} /** *	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++;} /** *	ipc_schedule_free	- free ipc + rcu space *  * 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 =		container_of(head, struct ipc_rcu_grace, rcu);	struct ipc_rcu_sched *sched =			container_of(&(grace->data[0]), struct ipc_rcu_sched, data[0]); 	INIT_WORK(&sched->work, vfree, sched);	schedule_work(&sched->work);} /** *	ipc_immediate_free	- free ipc + rcu space * *	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 *	@ipcp: IPC permission set *	@flag: desired permission set. * *	Check user, group, other permissions for access *	to ipc resources. return 0 if allowed */ int ipcperms (struct kern_ipc_perm *ipcp, short flag){	/* flag will most probably be 0 or S_...UGO from <linux/stat.h> */	int requested_mode, granted_mode; 	requested_mode = (flag >> 6) | (flag >> 3) | flag;	granted_mode = ipcp->mode;	if (current->euid == ipcp->cuid || current->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) && 	    !capable(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 old ipc permissions to new *	@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;} /* * So far only shm_get_stat() calls ipc_get() via shm_get(), so ipc_get() * is called with shm_ids.sem locked.  Since grow_ary() is also called with * shm_ids.sem down(for Shared Memory), there is no need to add read  * barriers here to gurantee the writes in grow_ary() are seen in order  * here (for Alpha). * * However ipc_get() itself does not necessary require ipc_ids.sem down. So * if in the future ipc_get() is used by other places without ipc_ids.sem * down, then ipc_get() needs read memery barriers as ipc_lock() does. */struct kern_ipc_perm* ipc_get(struct ipc_ids* ids, int id){	struct kern_ipc_perm* out;	int lid = id % SEQ_MULTIPLIER;	if(lid >= ids->entries->size)		return NULL;	out = ids->entries->p[lid];

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