msg.c 17.8 KB
Newer Older
Linus Torvalds's avatar
Linus Torvalds committed
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
/*
 * linux/ipc/msg.c
 * Copyright (C) 1992 Krishna Balasubramanian 
 *
 * Removed all the remaining kerneld mess
 * Catch the -EFAULT stuff properly
 * Use GFP_KERNEL for messages as in 1.2
 * Fixed up the unchecked user space derefs
 * Copyright (C) 1998 Alan Cox & Andi Kleen
 *
 * /proc/sysvipc/msg support (c) 1999 Dragos Acostachioaie <dragos@iname.com>
 *
 * mostly rewritten, threaded and wake-one semantics added
 * MSGMAX limit removed, sysctl's added
 * (c) 1999 Manfred Spraul <manfreds@colorfullife.com>
 */

#include <linux/config.h>
Linus Torvalds's avatar
Linus Torvalds committed
19
#include <linux/slab.h>
Linus Torvalds's avatar
Linus Torvalds committed
20 21 22 23 24
#include <linux/msg.h>
#include <linux/spinlock.h>
#include <linux/init.h>
#include <linux/proc_fs.h>
#include <linux/list.h>
25
#include <linux/security.h>
26 27
#include <linux/sched.h>
#include <asm/current.h>
Linus Torvalds's avatar
Linus Torvalds committed
28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64
#include <asm/uaccess.h>
#include "util.h"

/* sysctl: */
int msg_ctlmax = MSGMAX;
int msg_ctlmnb = MSGMNB;
int msg_ctlmni = MSGMNI;

/* one msg_receiver structure for each sleeping receiver */
struct msg_receiver {
	struct list_head r_list;
	struct task_struct* r_tsk;

	int r_mode;
	long r_msgtype;
	long r_maxsize;

	struct msg_msg* volatile r_msg;
};

/* one msg_sender for each sleeping sender */
struct msg_sender {
	struct list_head list;
	struct task_struct* tsk;
};

#define SEARCH_ANY		1
#define SEARCH_EQUAL		2
#define SEARCH_NOTEQUAL		3
#define SEARCH_LESSEQUAL	4

static atomic_t msg_bytes = ATOMIC_INIT(0);
static atomic_t msg_hdrs = ATOMIC_INIT(0);

static struct ipc_ids msg_ids;

#define msg_lock(id)	((struct msg_queue*)ipc_lock(&msg_ids,id))
65
#define msg_unlock(msq)	ipc_unlock(&(msq)->q_perm)
Linus Torvalds's avatar
Linus Torvalds committed
66 67 68 69 70 71
#define msg_rmid(id)	((struct msg_queue*)ipc_rmid(&msg_ids,id))
#define msg_checkid(msq, msgid)	\
	ipc_checkid(&msg_ids,&msq->q_perm,msgid)
#define msg_buildid(id, seq) \
	ipc_buildid(&msg_ids, id, seq)

Andrew Morton's avatar
Andrew Morton committed
72
static void freeque (struct msg_queue *msq, int id);
Linus Torvalds's avatar
Linus Torvalds committed
73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89
static int newque (key_t key, int msgflg);
#ifdef CONFIG_PROC_FS
static int sysvipc_msg_read_proc(char *buffer, char **start, off_t offset, int length, int *eof, void *data);
#endif

void __init msg_init (void)
{
	ipc_init_ids(&msg_ids,msg_ctlmni);

#ifdef CONFIG_PROC_FS
	create_proc_read_entry("sysvipc/msg", 0, 0, sysvipc_msg_read_proc, NULL);
#endif
}

static int newque (key_t key, int msgflg)
{
	int id;
90
	int retval;
Linus Torvalds's avatar
Linus Torvalds committed
91 92
	struct msg_queue *msq;

93
	msq  = ipc_rcu_alloc(sizeof(*msq));
Linus Torvalds's avatar
Linus Torvalds committed
94 95
	if (!msq) 
		return -ENOMEM;
96 97 98 99

	msq->q_perm.mode = (msgflg & S_IRWXUGO);
	msq->q_perm.key = key;

100
	msq->q_perm.security = NULL;
101 102
	retval = security_msg_queue_alloc(msq);
	if (retval) {
103
		ipc_rcu_free(msq, sizeof(*msq));
104 105 106
		return retval;
	}

Linus Torvalds's avatar
Linus Torvalds committed
107 108
	id = ipc_addid(&msg_ids, &msq->q_perm, msg_ctlmni);
	if(id == -1) {
109
		security_msg_queue_free(msq);
110
		ipc_rcu_free(msq, sizeof(*msq));
Linus Torvalds's avatar
Linus Torvalds committed
111 112 113 114
		return -ENOSPC;
	}

	msq->q_stime = msq->q_rtime = 0;
115
	msq->q_ctime = get_seconds();
Linus Torvalds's avatar
Linus Torvalds committed
116 117 118 119 120 121
	msq->q_cbytes = msq->q_qnum = 0;
	msq->q_qbytes = msg_ctlmnb;
	msq->q_lspid = msq->q_lrpid = 0;
	INIT_LIST_HEAD(&msq->q_messages);
	INIT_LIST_HEAD(&msq->q_receivers);
	INIT_LIST_HEAD(&msq->q_senders);
122
	msg_unlock(msq);
Linus Torvalds's avatar
Linus Torvalds committed
123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169

	return msg_buildid(id,msq->q_perm.seq);
}

static inline void ss_add(struct msg_queue* msq, struct msg_sender* mss)
{
	mss->tsk=current;
	current->state=TASK_INTERRUPTIBLE;
	list_add_tail(&mss->list,&msq->q_senders);
}

static inline void ss_del(struct msg_sender* mss)
{
	if(mss->list.next != NULL)
		list_del(&mss->list);
}

static void ss_wakeup(struct list_head* h, int kill)
{
	struct list_head *tmp;

	tmp = h->next;
	while (tmp != h) {
		struct msg_sender* mss;
		
		mss = list_entry(tmp,struct msg_sender,list);
		tmp = tmp->next;
		if(kill)
			mss->list.next=NULL;
		wake_up_process(mss->tsk);
	}
}

static void expunge_all(struct msg_queue* msq, int res)
{
	struct list_head *tmp;

	tmp = msq->q_receivers.next;
	while (tmp != &msq->q_receivers) {
		struct msg_receiver* msr;
		
		msr = list_entry(tmp,struct msg_receiver,r_list);
		tmp = tmp->next;
		msr->r_msg = ERR_PTR(res);
		wake_up_process(msr->r_tsk);
	}
}
Andrew Morton's avatar
Andrew Morton committed
170 171 172 173 174 175 176 177 178
/* 
 * freeque() wakes up waiters on the sender and receiver waiting queue, 
 * removes the message queue from message queue ID 
 * array, and cleans up all the messages associated with this queue.
 *
 * msg_ids.sem and the spinlock for this message queue is hold
 * before freeque() is called. msg_ids.sem remains locked on exit.
 */
static void freeque (struct msg_queue *msq, int id)
Linus Torvalds's avatar
Linus Torvalds committed
179 180 181 182 183
{
	struct list_head *tmp;

	expunge_all(msq,-EIDRM);
	ss_wakeup(&msq->q_senders,1);
Andrew Morton's avatar
Andrew Morton committed
184
	msq = msg_rmid(id);
185
	msg_unlock(msq);
Linus Torvalds's avatar
Linus Torvalds committed
186 187 188 189 190 191 192 193 194
		
	tmp = msq->q_messages.next;
	while(tmp != &msq->q_messages) {
		struct msg_msg* msg = list_entry(tmp,struct msg_msg,m_list);
		tmp = tmp->next;
		atomic_dec(&msg_hdrs);
		free_msg(msg);
	}
	atomic_sub(msq->q_cbytes, &msg_bytes);
195
	security_msg_queue_free(msq);
196
	ipc_rcu_free(msq, sizeof(struct msg_queue));
Linus Torvalds's avatar
Linus Torvalds committed
197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219
}

asmlinkage long sys_msgget (key_t key, int msgflg)
{
	int id, ret = -EPERM;
	struct msg_queue *msq;
	
	down(&msg_ids.sem);
	if (key == IPC_PRIVATE) 
		ret = newque(key, msgflg);
	else if ((id = ipc_findkey(&msg_ids, key)) == -1) { /* key not used */
		if (!(msgflg & IPC_CREAT))
			ret = -ENOENT;
		else
			ret = newque(key, msgflg);
	} else if (msgflg & IPC_CREAT && msgflg & IPC_EXCL) {
		ret = -EEXIST;
	} else {
		msq = msg_lock(id);
		if(msq==NULL)
			BUG();
		if (ipcperms(&msq->q_perm, msgflg))
			ret = -EACCES;
220 221 222 223 224 225
		else {
			int qid = msg_buildid(id, msq->q_perm.seq);
		    	ret = security_msg_queue_associate(msq, msgflg);
			if (!ret)
				ret = qid;
		}
226
		msg_unlock(msq);
Linus Torvalds's avatar
Linus Torvalds committed
227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346
	}
	up(&msg_ids.sem);
	return ret;
}

static inline unsigned long copy_msqid_to_user(void *buf, struct msqid64_ds *in, int version)
{
	switch(version) {
	case IPC_64:
		return copy_to_user (buf, in, sizeof(*in));
	case IPC_OLD:
	    {
		struct msqid_ds out;

		memset(&out,0,sizeof(out));

		ipc64_perm_to_ipc_perm(&in->msg_perm, &out.msg_perm);

		out.msg_stime		= in->msg_stime;
		out.msg_rtime		= in->msg_rtime;
		out.msg_ctime		= in->msg_ctime;

		if(in->msg_cbytes > USHRT_MAX)
			out.msg_cbytes	= USHRT_MAX;
		else
			out.msg_cbytes	= in->msg_cbytes;
		out.msg_lcbytes		= in->msg_cbytes;

		if(in->msg_qnum > USHRT_MAX)
			out.msg_qnum	= USHRT_MAX;
		else
			out.msg_qnum	= in->msg_qnum;

		if(in->msg_qbytes > USHRT_MAX)
			out.msg_qbytes	= USHRT_MAX;
		else
			out.msg_qbytes	= in->msg_qbytes;
		out.msg_lqbytes		= in->msg_qbytes;

		out.msg_lspid		= in->msg_lspid;
		out.msg_lrpid		= in->msg_lrpid;

		return copy_to_user (buf, &out, sizeof(out));
	    }
	default:
		return -EINVAL;
	}
}

struct msq_setbuf {
	unsigned long	qbytes;
	uid_t		uid;
	gid_t		gid;
	mode_t		mode;
};

static inline unsigned long copy_msqid_from_user(struct msq_setbuf *out, void *buf, int version)
{
	switch(version) {
	case IPC_64:
	    {
		struct msqid64_ds tbuf;

		if (copy_from_user (&tbuf, buf, sizeof (tbuf)))
			return -EFAULT;

		out->qbytes		= tbuf.msg_qbytes;
		out->uid		= tbuf.msg_perm.uid;
		out->gid		= tbuf.msg_perm.gid;
		out->mode		= tbuf.msg_perm.mode;

		return 0;
	    }
	case IPC_OLD:
	    {
		struct msqid_ds tbuf_old;

		if (copy_from_user (&tbuf_old, buf, sizeof (tbuf_old)))
			return -EFAULT;

		out->uid		= tbuf_old.msg_perm.uid;
		out->gid		= tbuf_old.msg_perm.gid;
		out->mode		= tbuf_old.msg_perm.mode;

		if(tbuf_old.msg_qbytes == 0)
			out->qbytes	= tbuf_old.msg_lqbytes;
		else
			out->qbytes	= tbuf_old.msg_qbytes;

		return 0;
	    }
	default:
		return -EINVAL;
	}
}

asmlinkage long sys_msgctl (int msqid, int cmd, struct msqid_ds *buf)
{
	int err, version;
	struct msg_queue *msq;
	struct msq_setbuf setbuf;
	struct kern_ipc_perm *ipcp;
	
	if (msqid < 0 || cmd < 0)
		return -EINVAL;

	version = ipc_parse_version(&cmd);

	switch (cmd) {
	case IPC_INFO: 
	case MSG_INFO: 
	{ 
		struct msginfo msginfo;
		int max_id;
		if (!buf)
			return -EFAULT;
		/* We must not return kernel stack data.
		 * due to padding, it's not enough
		 * to set all member fields.
		 */
347 348 349 350 351

		err = security_msg_queue_msgctl(NULL, cmd);
		if (err)
			return err;

Linus Torvalds's avatar
Linus Torvalds committed
352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380
		memset(&msginfo,0,sizeof(msginfo));	
		msginfo.msgmni = msg_ctlmni;
		msginfo.msgmax = msg_ctlmax;
		msginfo.msgmnb = msg_ctlmnb;
		msginfo.msgssz = MSGSSZ;
		msginfo.msgseg = MSGSEG;
		down(&msg_ids.sem);
		if (cmd == MSG_INFO) {
			msginfo.msgpool = msg_ids.in_use;
			msginfo.msgmap = atomic_read(&msg_hdrs);
			msginfo.msgtql = atomic_read(&msg_bytes);
		} else {
			msginfo.msgmap = MSGMAP;
			msginfo.msgpool = MSGPOOL;
			msginfo.msgtql = MSGTQL;
		}
		max_id = msg_ids.max_id;
		up(&msg_ids.sem);
		if (copy_to_user (buf, &msginfo, sizeof(struct msginfo)))
			return -EFAULT;
		return (max_id < 0) ? 0: max_id;
	}
	case MSG_STAT:
	case IPC_STAT:
	{
		struct msqid64_ds tbuf;
		int success_return;
		if (!buf)
			return -EFAULT;
Linus Torvalds's avatar
Linus Torvalds committed
381
		if(cmd == MSG_STAT && msqid >= msg_ids.size)
Linus Torvalds's avatar
Linus Torvalds committed
382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401
			return -EINVAL;

		memset(&tbuf,0,sizeof(tbuf));

		msq = msg_lock(msqid);
		if (msq == NULL)
			return -EINVAL;

		if(cmd == MSG_STAT) {
			success_return = msg_buildid(msqid, msq->q_perm.seq);
		} else {
			err = -EIDRM;
			if (msg_checkid(msq,msqid))
				goto out_unlock;
			success_return = 0;
		}
		err = -EACCES;
		if (ipcperms (&msq->q_perm, S_IRUGO))
			goto out_unlock;

402 403 404 405
		err = security_msg_queue_msgctl(msq, cmd);
		if (err)
			goto out_unlock;

Linus Torvalds's avatar
Linus Torvalds committed
406 407 408 409 410 411 412 413 414
		kernel_to_ipc64_perm(&msq->q_perm, &tbuf.msg_perm);
		tbuf.msg_stime  = msq->q_stime;
		tbuf.msg_rtime  = msq->q_rtime;
		tbuf.msg_ctime  = msq->q_ctime;
		tbuf.msg_cbytes = msq->q_cbytes;
		tbuf.msg_qnum   = msq->q_qnum;
		tbuf.msg_qbytes = msq->q_qbytes;
		tbuf.msg_lspid  = msq->q_lspid;
		tbuf.msg_lrpid  = msq->q_lrpid;
415
		msg_unlock(msq);
Linus Torvalds's avatar
Linus Torvalds committed
416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447
		if (copy_msqid_to_user(buf, &tbuf, version))
			return -EFAULT;
		return success_return;
	}
	case IPC_SET:
		if (!buf)
			return -EFAULT;
		if (copy_msqid_from_user (&setbuf, buf, version))
			return -EFAULT;
		break;
	case IPC_RMID:
		break;
	default:
		return  -EINVAL;
	}

	down(&msg_ids.sem);
	msq = msg_lock(msqid);
	err=-EINVAL;
	if (msq == NULL)
		goto out_up;

	err = -EIDRM;
	if (msg_checkid(msq,msqid))
		goto out_unlock_up;
	ipcp = &msq->q_perm;
	err = -EPERM;
	if (current->euid != ipcp->cuid && 
	    current->euid != ipcp->uid && !capable(CAP_SYS_ADMIN))
	    /* We _could_ check for CAP_CHOWN above, but we don't */
		goto out_unlock_up;

448 449 450 451
	err = security_msg_queue_msgctl(msq, cmd);
	if (err)
		goto out_unlock_up;

Linus Torvalds's avatar
Linus Torvalds committed
452 453 454
	switch (cmd) {
	case IPC_SET:
	{
455
		err = -EPERM;
Linus Torvalds's avatar
Linus Torvalds committed
456 457
		if (setbuf.qbytes > msg_ctlmnb && !capable(CAP_SYS_RESOURCE))
			goto out_unlock_up;
458

Linus Torvalds's avatar
Linus Torvalds committed
459 460 461 462 463 464
		msq->q_qbytes = setbuf.qbytes;

		ipcp->uid = setbuf.uid;
		ipcp->gid = setbuf.gid;
		ipcp->mode = (ipcp->mode & ~S_IRWXUGO) | 
			(S_IRWXUGO & setbuf.mode);
465
		msq->q_ctime = get_seconds();
Linus Torvalds's avatar
Linus Torvalds committed
466 467 468 469 470 471 472 473
		/* sleeping receivers might be excluded by
		 * stricter permissions.
		 */
		expunge_all(msq,-EAGAIN);
		/* sleeping senders might be able to send
		 * due to a larger queue size.
		 */
		ss_wakeup(&msq->q_senders,0);
474
		msg_unlock(msq);
Linus Torvalds's avatar
Linus Torvalds committed
475 476 477
		break;
	}
	case IPC_RMID:
Andrew Morton's avatar
Andrew Morton committed
478
		freeque (msq, msqid); 
Linus Torvalds's avatar
Linus Torvalds committed
479 480 481 482 483 484 485
		break;
	}
	err = 0;
out_up:
	up(&msg_ids.sem);
	return err;
out_unlock_up:
486
	msg_unlock(msq);
Linus Torvalds's avatar
Linus Torvalds committed
487 488
	goto out_up;
out_unlock:
489
	msg_unlock(msq);
Linus Torvalds's avatar
Linus Torvalds committed
490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514
	return err;
}

static int testmsg(struct msg_msg* msg,long type,int mode)
{
	switch(mode)
	{
		case SEARCH_ANY:
			return 1;
		case SEARCH_LESSEQUAL:
			if(msg->m_type <=type)
				return 1;
			break;
		case SEARCH_EQUAL:
			if(msg->m_type == type)
				return 1;
			break;
		case SEARCH_NOTEQUAL:
			if(msg->m_type != type)
				return 1;
			break;
	}
	return 0;
}

515
static inline int pipelined_send(struct msg_queue* msq, struct msg_msg* msg)
Linus Torvalds's avatar
Linus Torvalds committed
516 517 518 519 520 521 522 523
{
	struct list_head* tmp;

	tmp = msq->q_receivers.next;
	while (tmp != &msq->q_receivers) {
		struct msg_receiver* msr;
		msr = list_entry(tmp,struct msg_receiver,r_list);
		tmp = tmp->next;
524 525
		if(testmsg(msg,msr->r_msgtype,msr->r_mode) &&
		   !security_msg_queue_msgrcv(msq, msg, msr->r_tsk, msr->r_msgtype, msr->r_mode)) {
Linus Torvalds's avatar
Linus Torvalds committed
526 527 528 529 530 531
			list_del(&msr->r_list);
			if(msr->r_maxsize < msg->m_ts) {
				msr->r_msg = ERR_PTR(-E2BIG);
				wake_up_process(msr->r_tsk);
			} else {
				msr->r_msg = msg;
Linus Torvalds's avatar
Linus Torvalds committed
532
				msq->q_lrpid = msr->r_tsk->pid;
533
				msq->q_rtime = get_seconds();
Linus Torvalds's avatar
Linus Torvalds committed
534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575
				wake_up_process(msr->r_tsk);
				return 1;
			}
		}
	}
	return 0;
}

asmlinkage long sys_msgsnd (int msqid, struct msgbuf *msgp, size_t msgsz, int msgflg)
{
	struct msg_queue *msq;
	struct msg_msg *msg;
	long mtype;
	int err;
	
	if (msgsz > msg_ctlmax || (long) msgsz < 0 || msqid < 0)
		return -EINVAL;
	if (get_user(mtype, &msgp->mtype))
		return -EFAULT; 
	if (mtype < 1)
		return -EINVAL;

	msg = load_msg(msgp->mtext, msgsz);
	if(IS_ERR(msg))
		return PTR_ERR(msg);

	msg->m_type = mtype;
	msg->m_ts = msgsz;

	msq = msg_lock(msqid);
	err=-EINVAL;
	if(msq==NULL)
		goto out_free;
retry:
	err= -EIDRM;
	if (msg_checkid(msq,msqid))
		goto out_unlock_free;

	err=-EACCES;
	if (ipcperms(&msq->q_perm, S_IWUGO)) 
		goto out_unlock_free;

576 577 578 579
	err = security_msg_queue_msgsnd(msq, msg, msgflg);
	if (err)
		goto out_unlock_free;

Linus Torvalds's avatar
Linus Torvalds committed
580 581 582 583 584 585 586 587 588
	if(msgsz + msq->q_cbytes > msq->q_qbytes ||
		1 + msq->q_qnum > msq->q_qbytes) {
		struct msg_sender s;

		if(msgflg&IPC_NOWAIT) {
			err=-EAGAIN;
			goto out_unlock_free;
		}
		ss_add(msq, &s);
589
		msg_unlock(msq);
Linus Torvalds's avatar
Linus Torvalds committed
590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605
		schedule();
		current->state= TASK_RUNNING;

		msq = msg_lock(msqid);
		err = -EIDRM;
		if(msq==NULL)
			goto out_free;
		ss_del(&s);
		
		if (signal_pending(current)) {
			err=-EINTR;
			goto out_unlock_free;
		}
		goto retry;
	}

606
	msq->q_lspid = current->tgid;
607
	msq->q_stime = get_seconds();
Linus Torvalds's avatar
Linus Torvalds committed
608

Linus Torvalds's avatar
Linus Torvalds committed
609 610 611 612 613 614 615 616 617 618 619 620 621
	if(!pipelined_send(msq,msg)) {
		/* noone is waiting for this message, enqueue it */
		list_add_tail(&msg->m_list,&msq->q_messages);
		msq->q_cbytes += msgsz;
		msq->q_qnum++;
		atomic_add(msgsz,&msg_bytes);
		atomic_inc(&msg_hdrs);
	}
	
	err = 0;
	msg = NULL;

out_unlock_free:
622
	msg_unlock(msq);
Linus Torvalds's avatar
Linus Torvalds committed
623 624 625 626 627 628
out_free:
	if(msg!=NULL)
		free_msg(msg);
	return err;
}

629
static inline int convert_mode(long* msgtyp, int msgflg)
Linus Torvalds's avatar
Linus Torvalds committed
630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665
{
	/* 
	 *  find message of correct type.
	 *  msgtyp = 0 => get first.
	 *  msgtyp > 0 => get first message of matching type.
	 *  msgtyp < 0 => get message with least type must be < abs(msgtype).  
	 */
	if(*msgtyp==0)
		return SEARCH_ANY;
	if(*msgtyp<0) {
		*msgtyp=-(*msgtyp);
		return SEARCH_LESSEQUAL;
	}
	if(msgflg & MSG_EXCEPT)
		return SEARCH_NOTEQUAL;
	return SEARCH_EQUAL;
}

asmlinkage long sys_msgrcv (int msqid, struct msgbuf *msgp, size_t msgsz,
			    long msgtyp, int msgflg)
{
	struct msg_queue *msq;
	struct msg_receiver msr_d;
	struct list_head* tmp;
	struct msg_msg* msg, *found_msg;
	int err;
	int mode;

	if (msqid < 0 || (long) msgsz < 0)
		return -EINVAL;
	mode = convert_mode(&msgtyp,msgflg);

	msq = msg_lock(msqid);
	if(msq==NULL)
		return -EINVAL;
retry:
Linus Torvalds's avatar
Linus Torvalds committed
666 667 668 669
	err = -EIDRM;
	if (msg_checkid(msq,msqid))
		goto out_unlock;

Linus Torvalds's avatar
Linus Torvalds committed
670 671 672 673 674 675 676 677
	err=-EACCES;
	if (ipcperms (&msq->q_perm, S_IRUGO))
		goto out_unlock;

	tmp = msq->q_messages.next;
	found_msg=NULL;
	while (tmp != &msq->q_messages) {
		msg = list_entry(tmp,struct msg_msg,m_list);
678 679
		if(testmsg(msg,msgtyp,mode) &&
		   !security_msg_queue_msgrcv(msq, msg, current, msgtyp, mode)) {
Linus Torvalds's avatar
Linus Torvalds committed
680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698
			found_msg = msg;
			if(mode == SEARCH_LESSEQUAL && msg->m_type != 1) {
				found_msg=msg;
				msgtyp=msg->m_type-1;
			} else {
				found_msg=msg;
				break;
			}
		}
		tmp = tmp->next;
	}
	if(found_msg) {
		msg=found_msg;
		if ((msgsz < msg->m_ts) && !(msgflg & MSG_NOERROR)) {
			err=-E2BIG;
			goto out_unlock;
		}
		list_del(&msg->m_list);
		msq->q_qnum--;
699
		msq->q_rtime = get_seconds();
700
		msq->q_lrpid = current->tgid;
Linus Torvalds's avatar
Linus Torvalds committed
701 702 703 704
		msq->q_cbytes -= msg->m_ts;
		atomic_sub(msg->m_ts,&msg_bytes);
		atomic_dec(&msg_hdrs);
		ss_wakeup(&msq->q_senders,0);
705
		msg_unlock(msq);
Linus Torvalds's avatar
Linus Torvalds committed
706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732
out_success:
		msgsz = (msgsz > msg->m_ts) ? msg->m_ts : msgsz;
		if (put_user (msg->m_type, &msgp->mtype) ||
		    store_msg(msgp->mtext, msg, msgsz)) {
			    msgsz = -EFAULT;
		}
		free_msg(msg);
		return msgsz;
	} else
	{
		/* no message waiting. Prepare for pipelined
		 * receive.
		 */
		if (msgflg & IPC_NOWAIT) {
			err=-ENOMSG;
			goto out_unlock;
		}
		list_add_tail(&msr_d.r_list,&msq->q_receivers);
		msr_d.r_tsk = current;
		msr_d.r_msgtype = msgtyp;
		msr_d.r_mode = mode;
		if(msgflg & MSG_NOERROR)
			msr_d.r_maxsize = INT_MAX;
		 else
		 	msr_d.r_maxsize = msgsz;
		msr_d.r_msg = ERR_PTR(-EAGAIN);
		current->state = TASK_INTERRUPTIBLE;
733
		msg_unlock(msq);
Linus Torvalds's avatar
Linus Torvalds committed
734 735 736

		schedule();

Andrew Morton's avatar
Andrew Morton committed
737 738 739 740 741 742 743 744 745
		/*
		 * The below optimisation is buggy.  A sleeping thread that is
		 * woken up checks if it got a message and if so, copies it to
		 * userspace and just returns without taking any locks.
		 * But this return to user space can be faster than the message
		 * send, and if the receiver immediately exits the
		 * wake_up_process performed by the sender will oops.
		 */
#if 0
Linus Torvalds's avatar
Linus Torvalds committed
746 747 748
		msg = (struct msg_msg*) msr_d.r_msg;
		if(!IS_ERR(msg)) 
			goto out_success;
Andrew Morton's avatar
Andrew Morton committed
749
#endif
Linus Torvalds's avatar
Linus Torvalds committed
750

751
		msq = msg_lock(msqid);
Linus Torvalds's avatar
Linus Torvalds committed
752 753 754 755 756
		msg = (struct msg_msg*)msr_d.r_msg;
		if(!IS_ERR(msg)) {
			/* our message arived while we waited for
			 * the spinlock. Process it.
			 */
757 758
			if(msq)
				msg_unlock(msq);
Linus Torvalds's avatar
Linus Torvalds committed
759 760 761 762
			goto out_success;
		}
		err = PTR_ERR(msg);
		if(err == -EAGAIN) {
763
			if(!msq)
Linus Torvalds's avatar
Linus Torvalds committed
764 765 766 767 768 769 770 771 772
				BUG();
			list_del(&msr_d.r_list);
			if (signal_pending(current))
				err=-EINTR;
			 else
				goto retry;
		}
	}
out_unlock:
773 774
	if(msq)
		msg_unlock(msq);
Linus Torvalds's avatar
Linus Torvalds committed
775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806
	return err;
}

#ifdef CONFIG_PROC_FS
static int sysvipc_msg_read_proc(char *buffer, char **start, off_t offset, int length, int *eof, void *data)
{
	off_t pos = 0;
	off_t begin = 0;
	int i, len = 0;

	down(&msg_ids.sem);
	len += sprintf(buffer, "       key      msqid perms      cbytes       qnum lspid lrpid   uid   gid  cuid  cgid      stime      rtime      ctime\n");

	for(i = 0; i <= msg_ids.max_id; i++) {
		struct msg_queue * msq;
		msq = msg_lock(i);
		if(msq != NULL) {
			len += sprintf(buffer + len, "%10d %10d  %4o  %10lu %10lu %5u %5u %5u %5u %5u %5u %10lu %10lu %10lu\n",
				msq->q_perm.key,
				msg_buildid(i,msq->q_perm.seq),
				msq->q_perm.mode,
				msq->q_cbytes,
				msq->q_qnum,
				msq->q_lspid,
				msq->q_lrpid,
				msq->q_perm.uid,
				msq->q_perm.gid,
				msq->q_perm.cuid,
				msq->q_perm.cgid,
				msq->q_stime,
				msq->q_rtime,
				msq->q_ctime);
807
			msg_unlock(msq);
Linus Torvalds's avatar
Linus Torvalds committed
808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830

			pos += len;
			if(pos < offset) {
				len = 0;
				begin = pos;
			}
			if(pos > offset + length)
				goto done;
		}

	}
	*eof = 1;
done:
	up(&msg_ids.sem);
	*start = buffer + (offset - begin);
	len -= (offset - begin);
	if(len > length)
		len = length;
	if(len < 0)
		len = 0;
	return len;
}
#endif