xref: /original-bsd/sys/kern/kern_proc.c (revision a13d7ea1) 
1 /*	kern_proc.c	4.24	82/03/27	*/
2 
3 #include "../h/param.h"
4 #include "../h/systm.h"
5 #include "../h/map.h"
6 #include "../h/mtpr.h"
7 #include "../h/dir.h"
8 #include "../h/user.h"
9 #include "../h/proc.h"
10 #include "../h/buf.h"
11 #include "../h/reg.h"
12 #include "../h/inode.h"
13 #include "../h/seg.h"
14 #include "../h/acct.h"
15 #include "/usr/include/wait.h"
16 #include "../h/pte.h"
17 #include "../h/vm.h"
18 #include "../h/text.h"
19 #include "../h/psl.h"
20 #include "../h/vlimit.h"
21 #include "../h/file.h"
22 
23 /*
24  * exec system call, with and without environments.
25  */
26 struct execa {
27 	char	*fname;
28 	char	**argp;
29 	char	**envp;
30 };
31 
32 exec()
33 {
34 	((struct execa *)u.u_ap)->envp = NULL;
35 	exece();
36 }
37 
38 exece()
39 {
40 	register nc;
41 	register char *cp;
42 	register struct buf *bp;
43 	register struct execa *uap;
44 	int na, ne, ucp, ap, c;
45 	int indir, uid, gid;
46 	char *sharg;
47 	struct inode *ip;
48 	swblk_t bno;
49 	char cfname[DIRSIZ];
50 	char cfarg[SHSIZE];
51 
52 	if ((ip = namei(uchar, 0, 1)) == NULL)
53 		return;
54 	bno = 0;
55 	bp = 0;
56 	indir = 0;
57 	uid = u.u_uid;
58 	gid = u.u_gid;
59 	if (ip->i_mode & ISUID)
60 		uid = ip->i_uid;
61 	if (ip->i_mode & ISGID)
62 		gid = ip->i_gid;
63 
64   again:
65 	if (access(ip, IEXEC))
66 		goto bad;
67 	if ((u.u_procp->p_flag&STRC) && access(ip, IREAD))
68 		goto bad;
69 	if ((ip->i_mode & IFMT) != IFREG ||
70 	   (ip->i_mode & (IEXEC|(IEXEC>>3)|(IEXEC>>6))) == 0) {
71 		u.u_error = EACCES;
72 		goto bad;
73 	}
74 
75 	/*
76 	 * Read in first few bytes of file for segment sizes, ux_mag:
77 	 *	407 = plain executable
78 	 *	410 = RO text
79 	 *	413 = demand paged RO text
80 	 * Also an ASCII line beginning with #! is
81 	 * the file name of a ``shell'' and arguments may be prepended
82 	 * to the argument list if given here.
83 	 *
84 	 * SHELL NAMES ARE LIMITED IN LENGTH.
85 	 *
86 	 * ONLY ONE ARGUMENT MAY BE PASSED TO THE SHELL FROM
87 	 * THE ASCII LINE.
88 	 */
89 	u.u_base = (caddr_t)&u.u_exdata;
90 	u.u_count = sizeof(u.u_exdata);
91 	u.u_offset = 0;
92 	u.u_segflg = 1;
93 	readi(ip);
94 	u.u_segflg = 0;
95 	if (u.u_error)
96 		goto bad;
97 	if (u.u_count > sizeof(u.u_exdata) - sizeof(u.u_exdata.Ux_A) &&
98 	    u.u_exdata.ux_shell[0] != '#') {
99 		u.u_error = ENOEXEC;
100 		goto bad;
101 	}
102 	switch (u.u_exdata.ux_mag) {
103 
104 	case 0407:
105 		u.u_exdata.ux_dsize += u.u_exdata.ux_tsize;
106 		u.u_exdata.ux_tsize = 0;
107 		break;
108 
109 	case 0413:
110 	case 0410:
111 		if (u.u_exdata.ux_tsize == 0) {
112 			u.u_error = ENOEXEC;
113 			goto bad;
114 		}
115 		break;
116 
117 	default:
118 		if (u.u_exdata.ux_shell[0] != '#' ||
119 		    u.u_exdata.ux_shell[1] != '!' ||
120 		    indir) {
121 			u.u_error = ENOEXEC;
122 			goto bad;
123 		}
124 		cp = &u.u_exdata.ux_shell[2];		/* skip "#!" */
125 		while (cp < &u.u_exdata.ux_shell[SHSIZE]) {
126 			if (*cp == '\t')
127 				*cp = ' ';
128 			else if (*cp == '\n') {
129 				*cp = '\0';
130 				break;
131 			}
132 			cp++;
133 		}
134 		if (*cp != '\0') {
135 			u.u_error = ENOEXEC;
136 			goto bad;
137 		}
138 		cp = &u.u_exdata.ux_shell[2];
139 		while (*cp == ' ')
140 			cp++;
141 		u.u_dirp = cp;
142 		while (*cp && *cp != ' ')
143 			cp++;
144 		sharg = NULL;
145 		if (*cp) {
146 			*cp++ = '\0';
147 			while (*cp == ' ')
148 				cp++;
149 			if (*cp) {
150 				bcopy((caddr_t)cp, (caddr_t)cfarg, SHSIZE);
151 				sharg = cfarg;
152 			}
153 		}
154 		bcopy((caddr_t)u.u_dbuf, (caddr_t)cfname, DIRSIZ);
155 		indir = 1;
156 		iput(ip);
157 		ip = namei(schar, 0, 1);
158 		if (ip == NULL)
159 			return;
160 		goto again;
161 	}
162 
163 	/*
164 	 * Collect arguments on "file" in swap space.
165 	 */
166 	na = 0;
167 	ne = 0;
168 	nc = 0;
169 	uap = (struct execa *)u.u_ap;
170 	if ((bno = rmalloc(argmap, ctod(clrnd((int) btoc(NCARGS))))) == 0) {
171 		swkill(u.u_procp, "exece");
172 		goto bad;
173 	}
174 	if (bno % CLSIZE)
175 		panic("execa rmalloc");
176 	if (uap->argp) for (;;) {
177 		ap = NULL;
178 		if (indir && (na == 1 || na == 2 && sharg))
179 			ap = (int)uap->fname;
180 		else if (uap->argp) {
181 			ap = fuword((caddr_t)uap->argp);
182 			uap->argp++;
183 		}
184 		if (ap==NULL && uap->envp) {
185 			uap->argp = NULL;
186 			if ((ap = fuword((caddr_t)uap->envp)) == NULL)
187 				break;
188 			uap->envp++;
189 			ne++;
190 		}
191 		if (ap==NULL)
192 			break;
193 		na++;
194 		if (ap == -1)
195 			u.u_error = EFAULT;
196 		do {
197 			if (nc >= NCARGS-1)
198 				u.u_error = E2BIG;
199 			if (indir && na == 2 && sharg != NULL)
200 				c = *sharg++ & 0377;
201 			else if ((c = fubyte((caddr_t)ap++)) < 0)
202 				u.u_error = EFAULT;
203 			if (u.u_error) {
204 				if (bp)
205 					brelse(bp);
206 				bp = 0;
207 				goto badarg;
208 			}
209 			if ((nc&BMASK) == 0) {
210 				if (bp)
211 					bdwrite(bp);
212 				bp = getblk(argdev,
213 				    (daddr_t)(dbtofsb(bno)+(nc>>BSHIFT)));
214 				cp = bp->b_un.b_addr;
215 			}
216 			nc++;
217 			*cp++ = c;
218 		} while (c>0);
219 	}
220 	if (bp)
221 		bdwrite(bp);
222 	bp = 0;
223 	nc = (nc + NBPW-1) & ~(NBPW-1);
224 	if (indir)
225 		bcopy((caddr_t)cfname, (caddr_t)u.u_dbuf, DIRSIZ);
226 	getxfile(ip, nc + (na+4)*NBPW, uid, gid);
227 	if (u.u_error) {
228 badarg:
229 		for (c = 0; c < nc; c += BSIZE)
230 			if (bp = baddr(argdev, dbtofsb(bno)+(c>>BSHIFT))) {
231 				bp->b_flags |= B_AGE;		/* throw away */
232 				bp->b_flags &= ~B_DELWRI;	/* cancel io */
233 				brelse(bp);
234 				bp = 0;
235 			}
236 		goto bad;
237 	}
238 
239 	/*
240 	 * copy back arglist
241 	 */
242 	ucp = USRSTACK - nc - NBPW;
243 	ap = ucp - na*NBPW - 3*NBPW;
244 	u.u_ar0[SP] = ap;
245 	(void) suword((caddr_t)ap, na-ne);
246 	nc = 0;
247 	for (;;) {
248 		ap += NBPW;
249 		if (na==ne) {
250 			(void) suword((caddr_t)ap, 0);
251 			ap += NBPW;
252 		}
253 		if (--na < 0)
254 			break;
255 		(void) suword((caddr_t)ap, ucp);
256 		do {
257 			if ((nc&BMASK) == 0) {
258 				if (bp)
259 					brelse(bp);
260 				bp = bread(argdev,
261 				    (daddr_t)(dbtofsb(bno)+(nc>>BSHIFT)));
262 				bp->b_flags |= B_AGE;		/* throw away */
263 				bp->b_flags &= ~B_DELWRI;	/* cancel io */
264 				cp = bp->b_un.b_addr;
265 			}
266 			(void) subyte((caddr_t)ucp++, (c = *cp++));
267 			nc++;
268 		} while(c&0377);
269 	}
270 	(void) suword((caddr_t)ap, 0);
271 	(void) suword((caddr_t)ucp, 0);
272 	setregs();
273 bad:
274 	if (bp)
275 		brelse(bp);
276 	if (bno)
277 		rmfree(argmap, ctod(clrnd((int) btoc(NCARGS))), bno);
278 	iput(ip);
279 }
280 
281 /*
282  * Read in and set up memory for executed file.
283  */
284 getxfile(ip, nargc, uid, gid)
285 register struct inode *ip;
286 {
287 	register size_t ts, ds, ss;
288 	int pagi;
289 
290 	if (u.u_exdata.ux_mag == 0413)
291 		pagi = SPAGI;
292 	else
293 		pagi = 0;
294 	if (u.u_exdata.ux_tsize!=0 && (ip->i_flag&ITEXT)==0 &&
295 	    ip->i_count!=1) {
296 		register struct file *fp;
297 
298 		for (fp = file; fp < fileNFILE; fp++) {
299 			if (fp->f_flag & FSOCKET)
300 				continue;
301 			if (fp->f_inode == ip && (fp->f_flag&FWRITE)) {
302 				u.u_error = ETXTBSY;
303 				goto bad;
304 			}
305 		}
306 	}
307 
308 	/*
309 	 * Compute text and data sizes and make sure not too large.
310 	 */
311 	ts = clrnd(btoc(u.u_exdata.ux_tsize));
312 	ds = clrnd(btoc((u.u_exdata.ux_dsize+u.u_exdata.ux_bsize)));
313 	ss = clrnd(SSIZE + btoc(nargc));
314 	if (chksize(ts, ds, ss))
315 		goto bad;
316 
317 	/*
318 	 * Make sure enough space to start process.
319 	 */
320 	u.u_cdmap = zdmap;
321 	u.u_csmap = zdmap;
322 	if (swpexpand(ds, ss, &u.u_cdmap, &u.u_csmap) == NULL)
323 		goto bad;
324 
325 	/*
326 	 * At this point, committed to the new image!
327 	 * Release virtual memory resources of old process, and
328 	 * initialize the virtual memory of the new process.
329 	 * If we resulted from vfork(), instead wakeup our
330 	 * parent who will set SVFDONE when he has taken back
331 	 * our resources.
332 	 */
333 	u.u_prof.pr_scale = 0;
334 	if ((u.u_procp->p_flag & SVFORK) == 0)
335 		vrelvm();
336 	else {
337 		u.u_procp->p_flag &= ~SVFORK;
338 		u.u_procp->p_flag |= SKEEP;
339 		wakeup((caddr_t)u.u_procp);
340 		while ((u.u_procp->p_flag & SVFDONE) == 0)
341 			sleep((caddr_t)u.u_procp, PZERO - 1);
342 		u.u_procp->p_flag &= ~(SVFDONE|SKEEP);
343 	}
344 	u.u_procp->p_flag &= ~(SPAGI|SSEQL|SUANOM|SNUSIG);
345 	u.u_procp->p_flag |= pagi;
346 	u.u_dmap = u.u_cdmap;
347 	u.u_smap = u.u_csmap;
348 	vgetvm(ts, ds, ss);
349 
350 	if (pagi == 0) {
351 		/*
352 		 * Read in data segment.
353 		 */
354 		u.u_base = (char *)ctob(ts);
355 		u.u_offset = sizeof(u.u_exdata)+u.u_exdata.ux_tsize;
356 		u.u_count = u.u_exdata.ux_dsize;
357 		readi(ip);
358 	}
359 	xalloc(ip, pagi);
360 	if (pagi && u.u_procp->p_textp)
361 		vinifod((struct fpte *)dptopte(u.u_procp, 0),
362 		    PG_FTEXT, u.u_procp->p_textp->x_iptr,
363 		    1 + ts/CLSIZE, (int)btoc(u.u_exdata.ux_dsize));
364 
365 	/* THIS SHOULD BE DONE AT A LOWER LEVEL, IF AT ALL */
366 	mtpr(TBIA, 0);
367 
368 	/*
369 	 * set SUID/SGID protections, if no tracing
370 	 */
371 	if ((u.u_procp->p_flag&STRC)==0) {
372 		u.u_uid = uid;
373 		u.u_procp->p_uid = uid;
374 		u.u_gid = gid;
375 		u.u_grps[gid/(sizeof(int)*8)] |= 1 << (gid%(sizeof(int)*8));
376 	} else
377 		psignal(u.u_procp, SIGTRAP);
378 	u.u_tsize = ts;
379 	u.u_dsize = ds;
380 	u.u_ssize = ss;
381 bad:
382 	return;
383 }
384 
385 /*
386  * Clear registers on exec
387  */
388 setregs()
389 {
390 	register int (**rp)();
391 	register i;
392 	long sigmask;
393 
394 	for (rp = &u.u_signal[0], sigmask = 1L; rp < &u.u_signal[NSIG];
395 	    sigmask <<= 1, rp++) {
396 		switch (*rp) {
397 
398 		case SIG_IGN:
399 		case SIG_DFL:
400 		case SIG_HOLD:
401 			continue;
402 
403 		default:
404 			/*
405 			 * Normal or deferring catch; revert to default.
406 			 */
407 			(void) spl6();
408 			*rp = SIG_DFL;
409 			if ((int)*rp & 1)
410 				u.u_procp->p_siga0 |= sigmask;
411 			else
412 				u.u_procp->p_siga0 &= ~sigmask;
413 			if ((int)*rp & 2)
414 				u.u_procp->p_siga1 |= sigmask;
415 			else
416 				u.u_procp->p_siga1 &= ~sigmask;
417 			(void) spl0();
418 			continue;
419 		}
420 	}
421 /*
422 	for (rp = &u.u_ar0[0]; rp < &u.u_ar0[16];)
423 		*rp++ = 0;
424 */
425 	u.u_ar0[PC] = u.u_exdata.ux_entloc + 2; /* skip over entry mask */
426 	for (i=0; i<NOFILE; i++) {
427 		if (u.u_pofile[i]&EXCLOSE) {
428 			closef(u.u_ofile[i], 1);
429 			u.u_ofile[i] = NULL;
430 			u.u_pofile[i] &= ~EXCLOSE;
431 		}
432 	}
433 
434 	/*
435 	 * Remember file name for accounting.
436 	 */
437 	u.u_acflag &= ~AFORK;
438 	bcopy((caddr_t)u.u_dbuf, (caddr_t)u.u_comm, DIRSIZ);
439 }
440 
441 /*
442  * Exit system call: pass back caller's arg
443  */
444 rexit()
445 {
446 	register struct a {
447 		int	rval;
448 	} *uap;
449 
450 	uap = (struct a *)u.u_ap;
451 	exit((uap->rval & 0377) << 8);
452 }
453 
454 /*
455  * Release resources.
456  * Save u. area for parent to look at.
457  * Enter zombie state.
458  * Wake up parent and init processes,
459  * and dispose of children.
460  */
461 exit(rv)
462 {
463 	register int i;
464 	register struct proc *p, *q;
465 	register struct file *f;
466 	register int x;
467 
468 #ifdef PGINPROF
469 	vmsizmon();
470 #endif
471 	p = u.u_procp;
472 	p->p_flag &= ~(STRC|SULOCK);
473 	p->p_flag |= SWEXIT;
474 	p->p_clktim = 0;
475 	(void) spl6();
476 	if ((int)SIG_IGN & 1)
477 		p->p_siga0 = ~0;
478 	else
479 		p->p_siga0 = 0;
480 	if ((int)SIG_IGN & 2)
481 		p->p_siga1 = ~0;
482 	else
483 		p->p_siga1 = 0;
484 	(void) spl0();
485 	p->p_cpticks = 0;
486 	p->p_pctcpu = 0;
487 	for (i=0; i<NSIG; i++)
488 		u.u_signal[i] = SIG_IGN;
489 	/*
490 	 * Release virtual memory.  If we resulted from
491 	 * a vfork(), instead give the resources back to
492 	 * the parent.
493 	 */
494 	if ((p->p_flag & SVFORK) == 0)
495 		vrelvm();
496 	else {
497 		p->p_flag &= ~SVFORK;
498 		wakeup((caddr_t)p);
499 		while ((p->p_flag & SVFDONE) == 0)
500 			sleep((caddr_t)p, PZERO - 1);
501 		p->p_flag &= ~SVFDONE;
502 	}
503 	for (i=0; i<NOFILE; i++) {
504 		f = u.u_ofile[i];
505 		u.u_ofile[i] = NULL;
506 		closef(f, 1);
507 	}
508 	ilock(u.u_cdir);
509 	iput(u.u_cdir);
510 	if (u.u_rdir) {
511 		ilock(u.u_rdir);
512 		iput(u.u_rdir);
513 	}
514 	u.u_limit[LIM_FSIZE] = INFINITY;
515 	acct();
516 	vrelpt(u.u_procp);
517 	vrelu(u.u_procp, 0);
518 	(void) spl5();		/* hack for mem alloc race XXX */
519 	multprog--;
520 	p->p_stat = SZOMB;
521 	noproc = 1;
522 	i = PIDHASH(p->p_pid);
523 	x = p - proc;
524 	if (pidhash[i] == x)
525 		pidhash[i] = p->p_idhash;
526 	else {
527 		for (i = pidhash[i]; i != 0; i = proc[i].p_idhash)
528 			if (proc[i].p_idhash == x) {
529 				proc[i].p_idhash = p->p_idhash;
530 				goto done;
531 			}
532 		panic("exit");
533 	}
534 	if (p->p_pid == 1)
535 		panic("init died");
536 done:
537 	((struct xproc *)p)->xp_xstat = rv;		/* overlay */
538 	((struct xproc *)p)->xp_vm = u.u_vm;		/* overlay */
539 	vmsadd(&((struct xproc *)p)->xp_vm, &u.u_cvm);
540 	for (q = proc; q < procNPROC; q++)
541 		if (q->p_pptr == p) {
542 			q->p_pptr = &proc[1];
543 			q->p_ppid = 1;
544 			wakeup((caddr_t)&proc[1]);
545 			/*
546 			 * Traced processes are killed
547 			 * since their existence means someone is screwing up.
548 			 * Stopped processes are sent a hangup and a continue.
549 			 * This is designed to be ``safe'' for setuid
550 			 * processes since they must be willing to tolerate
551 			 * hangups anyways.
552 			 */
553 			if (q->p_flag&STRC) {
554 				q->p_flag &= ~STRC;
555 				psignal(q, SIGKILL);
556 			} else if (q->p_stat == SSTOP) {
557 				psignal(q, SIGHUP);
558 				psignal(q, SIGCONT);
559 			}
560 			/*
561 			 * Protect this process from future
562 			 * tty signals, clear TSTP/TTIN/TTOU if pending.
563 			 */
564 			(void) spgrp(q, -1);
565 		}
566 	wakeup((caddr_t)p->p_pptr);
567 	psignal(p->p_pptr, SIGCHLD);
568 	swtch();
569 }
570 
571 wait()
572 {
573 	struct vtimes vm;
574 	struct vtimes *vp;
575 
576 	if ((u.u_ar0[PS] & PSL_ALLCC) != PSL_ALLCC) {
577 		wait1(0, (struct vtimes *)0);
578 		return;
579 	}
580 	vp = (struct vtimes *)u.u_ar0[R1];
581 	wait1(u.u_ar0[R0], &vm);
582 	if (u.u_error)
583 		return;
584 	(void) copyout((caddr_t)&vm, (caddr_t)vp, sizeof (struct vtimes));
585 }
586 
587 /*
588  * Wait system call.
589  * Search for a terminated (zombie) child,
590  * finally lay it to rest, and collect its status.
591  * Look also for stopped (traced) children,
592  * and pass back status from them.
593  */
594 wait1(options, vp)
595 	register options;
596 	struct vtimes *vp;
597 {
598 	register f;
599 	register struct proc *p;
600 
601 	f = 0;
602 loop:
603 	for (p = proc; p < procNPROC; p++)
604 	if (p->p_pptr == u.u_procp) {
605 		f++;
606 		if (p->p_stat == SZOMB) {
607 			u.u_r.r_val1 = p->p_pid;
608 			u.u_r.r_val2 = ((struct xproc *)p)->xp_xstat;
609 			((struct xproc *)p)->xp_xstat = 0;
610 			if (vp)
611 				*vp = ((struct xproc *)p)->xp_vm;
612 			vmsadd(&u.u_cvm, &((struct xproc *)p)->xp_vm);
613 			((struct xproc *)p)->xp_vm = zvms;
614 			p->p_stat = NULL;
615 			p->p_pid = 0;
616 			p->p_ppid = 0;
617 			p->p_pptr = 0;
618 			p->p_sig = 0;
619 			p->p_siga0 = 0;
620 			p->p_siga1 = 0;
621 			p->p_pgrp = 0;
622 			p->p_flag = 0;
623 			p->p_wchan = 0;
624 			p->p_cursig = 0;
625 			return;
626 		}
627 		if (p->p_stat == SSTOP && (p->p_flag&SWTED)==0 &&
628 		    (p->p_flag&STRC || options&WUNTRACED)) {
629 			p->p_flag |= SWTED;
630 			u.u_r.r_val1 = p->p_pid;
631 			u.u_r.r_val2 = (p->p_cursig<<8) | WSTOPPED;
632 			return;
633 		}
634 	}
635 	if (f==0) {
636 		u.u_error = ECHILD;
637 		return;
638 	}
639 	if (options&WNOHANG) {
640 		u.u_r.r_val1 = 0;
641 		return;
642 	}
643 	if ((u.u_procp->p_flag&SNUSIG) && setjmp(u.u_qsav)) {
644 		u.u_eosys = RESTARTSYS;
645 		return;
646 	}
647 	sleep((caddr_t)u.u_procp, PWAIT);
648 	goto loop;
649 }
650 
651 /*
652  * fork system call.
653  */
654 fork()
655 {
656 
657 	u.u_cdmap = zdmap;
658 	u.u_csmap = zdmap;
659 	if (swpexpand(u.u_dsize, u.u_ssize, &u.u_cdmap, &u.u_csmap) == 0) {
660 		u.u_r.r_val2 = 0;
661 		return;
662 	}
663 	fork1(0);
664 }
665 
666 fork1(isvfork)
667 {
668 	register struct proc *p1, *p2;
669 	register a;
670 
671 	a = 0;
672 	p2 = NULL;
673 	for (p1 = proc; p1 < procNPROC; p1++) {
674 		if (p1->p_stat==NULL && p2==NULL)
675 			p2 = p1;
676 		else {
677 			if (p1->p_uid==u.u_uid && p1->p_stat!=NULL)
678 				a++;
679 		}
680 	}
681 	/*
682 	 * Disallow if
683 	 *  No processes at all;
684 	 *  not su and too many procs owned; or
685 	 *  not su and would take last slot.
686 	 */
687 	if (p2==NULL)
688 		tablefull("proc");
689 	if (p2==NULL || (u.u_uid!=0 && (p2==procNPROC-1 || a>MAXUPRC))) {
690 		u.u_error = EAGAIN;
691 		if (!isvfork) {
692 			(void) vsexpand(0, &u.u_cdmap, 1);
693 			(void) vsexpand(0, &u.u_csmap, 1);
694 		}
695 		goto out;
696 	}
697 	p1 = u.u_procp;
698 	if (newproc(isvfork)) {
699 		u.u_r.r_val1 = p1->p_pid;
700 		u.u_r.r_val2 = 1;  /* child */
701 		u.u_start = time;
702 		u.u_acflag = AFORK;
703 		return;
704 	}
705 	u.u_r.r_val1 = p2->p_pid;
706 
707 out:
708 	u.u_r.r_val2 = 0;
709 }
710 
711 /*
712  * break system call.
713  *  -- bad planning: "break" is a dirty word in C.
714  */
715 sbreak()
716 {
717 	struct a {
718 		char	*nsiz;
719 	};
720 	register int n, d;
721 
722 	/*
723 	 * set n to new data size
724 	 * set d to new-old
725 	 */
726 
727 	n = btoc(((struct a *)u.u_ap)->nsiz);
728 	if (!u.u_sep)
729 		n -= ctos(u.u_tsize) * stoc(1);
730 	if (n < 0)
731 		n = 0;
732 	d = clrnd(n - u.u_dsize);
733 	if (ctob(u.u_dsize+d) > u.u_limit[LIM_DATA]) {
734 		u.u_error = ENOMEM;
735 		return;
736 	}
737 	if (chksize(u.u_tsize, u.u_dsize+d, u.u_ssize))
738 		return;
739 	if (swpexpand(u.u_dsize+d, u.u_ssize, &u.u_dmap, &u.u_smap)==0)
740 		return;
741 	expand(d, P0BR);
742 }
743