xref: /dragonfly/sys/kern/sys_process.c (revision f503b4c4) 
1 /*
2  * Copyright (c) 1994, Sean Eric Fagan
3  * All rights reserved.
4  *
5  * Redistribution and use in source and binary forms, with or without
6  * modification, are permitted provided that the following conditions
7  * are met:
8  * 1. Redistributions of source code must retain the above copyright
9  *    notice, this list of conditions and the following disclaimer.
10  * 2. Redistributions in binary form must reproduce the above copyright
11  *    notice, this list of conditions and the following disclaimer in the
12  *    documentation and/or other materials provided with the distribution.
13  * 3. All advertising materials mentioning features or use of this software
14  *    must display the following acknowledgement:
15  *	This product includes software developed by Sean Eric Fagan.
16  * 4. The name of the author may not be used to endorse or promote products
17  *    derived from this software without specific prior written permission.
18  *
19  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
20  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
21  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
22  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
23  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
24  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
25  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
26  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
27  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
28  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
29  * SUCH DAMAGE.
30  *
31  * $FreeBSD: src/sys/kern/sys_process.c,v 1.51.2.6 2003/01/08 03:06:45 kan Exp $
32  * $DragonFly: src/sys/kern/sys_process.c,v 1.30 2007/02/19 01:14:23 corecode Exp $
33  */
34 
35 #include <sys/param.h>
36 #include <sys/systm.h>
37 #include <sys/sysproto.h>
38 #include <sys/proc.h>
39 #include <sys/priv.h>
40 #include <sys/vnode.h>
41 #include <sys/ptrace.h>
42 #include <sys/reg.h>
43 #include <sys/lock.h>
44 
45 #include <vm/vm.h>
46 #include <vm/pmap.h>
47 #include <vm/vm_map.h>
48 #include <vm/vm_page.h>
49 
50 #include <sys/user.h>
51 #include <vfs/procfs/procfs.h>
52 
53 #include <sys/thread2.h>
54 #include <sys/spinlock2.h>
55 
56 /* use the equivalent procfs code */
57 #if 0
58 static int
59 pread (struct proc *procp, unsigned int addr, unsigned int *retval) {
60 	int		rv;
61 	vm_map_t	map, tmap;
62 	vm_object_t	object;
63 	vm_offset_t	kva = 0;
64 	int		page_offset;	/* offset into page */
65 	vm_offset_t	pageno;		/* page number */
66 	vm_map_entry_t	out_entry;
67 	vm_prot_t	out_prot;
68 	boolean_t	wired;
69 	vm_pindex_t	pindex;
70 
71 	/* Map page into kernel space */
72 
73 	map = &procp->p_vmspace->vm_map;
74 
75 	page_offset = addr - trunc_page(addr);
76 	pageno = trunc_page(addr);
77 
78 	tmap = map;
79 	rv = vm_map_lookup(&tmap, pageno, VM_PROT_READ, &out_entry,
80 			   &object, &pindex, &out_prot, &wired);
81 
82 	if (rv != KERN_SUCCESS)
83 		return EINVAL;
84 
85 	vm_map_lookup_done (tmap, out_entry, 0);
86 
87 	/* Find space in kernel_map for the page we're interested in */
88 	rv = vm_map_find (&kernel_map, object, IDX_TO_OFF(pindex),
89 			  &kva,
90 			  PAGE_SIZE, PAGE_SIZE,
91 			  0, VM_MAPTYPE_NORMAL,
92 			  VM_PROT_ALL, VM_PROT_ALL,
93 			  0);
94 
95 	if (!rv) {
96 		vm_object_reference XXX (object);
97 
98 		rv = vm_map_wire (&kernel_map, kva, kva + PAGE_SIZE, 0);
99 		if (!rv) {
100 			*retval = 0;
101 			bcopy ((caddr_t)kva + page_offset,
102 			       retval, sizeof *retval);
103 		}
104 		vm_map_remove (&kernel_map, kva, kva + PAGE_SIZE);
105 	}
106 
107 	return rv;
108 }
109 
110 static int
111 pwrite (struct proc *procp, unsigned int addr, unsigned int datum) {
112 	int		rv;
113 	vm_map_t	map, tmap;
114 	vm_object_t	object;
115 	vm_offset_t	kva = 0;
116 	int		page_offset;	/* offset into page */
117 	vm_offset_t	pageno;		/* page number */
118 	vm_map_entry_t	out_entry;
119 	vm_prot_t	out_prot;
120 	boolean_t	wired;
121 	vm_pindex_t	pindex;
122 	boolean_t	fix_prot = 0;
123 
124 	/* Map page into kernel space */
125 
126 	map = &procp->p_vmspace->vm_map;
127 
128 	page_offset = addr - trunc_page(addr);
129 	pageno = trunc_page(addr);
130 
131 	/*
132 	 * Check the permissions for the area we're interested in.
133 	 */
134 
135 	if (vm_map_check_protection (map, pageno, pageno + PAGE_SIZE,
136 				     VM_PROT_WRITE, FALSE) == FALSE) {
137 		/*
138 		 * If the page was not writable, we make it so.
139 		 * XXX It is possible a page may *not* be read/executable,
140 		 * if a process changes that!
141 		 */
142 		fix_prot = 1;
143 		/* The page isn't writable, so let's try making it so... */
144 		if ((rv = vm_map_protect (map, pageno, pageno + PAGE_SIZE,
145 			VM_PROT_ALL, 0)) != KERN_SUCCESS)
146 		  return EFAULT;	/* I guess... */
147 	}
148 
149 	/*
150 	 * Now we need to get the page.  out_entry, out_prot, wired, and
151 	 * single_use aren't used.  One would think the vm code would be
152 	 * a *bit* nicer...  We use tmap because vm_map_lookup() can
153 	 * change the map argument.
154 	 */
155 
156 	tmap = map;
157 	rv = vm_map_lookup(&tmap, pageno, VM_PROT_WRITE, &out_entry,
158 			   &object, &pindex, &out_prot, &wired);
159 	if (rv != KERN_SUCCESS)
160 		return EINVAL;
161 
162 	/*
163 	 * Okay, we've got the page.  Let's release tmap.
164 	 */
165 	vm_map_lookup_done (tmap, out_entry, 0);
166 
167 	/*
168 	 * Fault the page in...
169 	 */
170 	rv = vm_fault(map, pageno, VM_PROT_WRITE|VM_PROT_READ, FALSE);
171 	if (rv != KERN_SUCCESS)
172 		return EFAULT;
173 
174 	/* Find space in kernel_map for the page we're interested in */
175 	rv = vm_map_find (&kernel_map, object, IDX_TO_OFF(pindex),
176 			  &kva,
177 			  PAGE_SIZE, PAGE_SIZE,
178 			  0, VM_MAPTYPE_NORMAL,
179 			  VM_PROT_ALL, VM_PROT_ALL,
180 			  0);
181 	if (!rv) {
182 		vm_object_reference XXX (object);
183 
184 		rv = vm_map_wire (&kernel_map, kva, kva + PAGE_SIZE, 0);
185 		if (!rv) {
186 		  bcopy (&datum, (caddr_t)kva + page_offset, sizeof datum);
187 		}
188 		vm_map_remove (&kernel_map, kva, kva + PAGE_SIZE);
189 	}
190 
191 	if (fix_prot)
192 		vm_map_protect (map, pageno, pageno + PAGE_SIZE,
193 			VM_PROT_READ|VM_PROT_EXECUTE, 0);
194 	return rv;
195 }
196 #endif
197 
198 /*
199  * Process debugging system call.
200  *
201  * MPALMOSTSAFE
202  */
203 int
204 sys_ptrace(struct ptrace_args *uap)
205 {
206 	struct proc *p = curproc;
207 
208 	/*
209 	 * XXX this obfuscation is to reduce stack usage, but the register
210 	 * structs may be too large to put on the stack anyway.
211 	 */
212 	union {
213 		struct ptrace_io_desc piod;
214 		struct dbreg dbreg;
215 		struct fpreg fpreg;
216 		struct reg reg;
217 	} r;
218 	void *addr;
219 	int error = 0;
220 
221 	addr = &r;
222 	switch (uap->req) {
223 	case PT_GETREGS:
224 	case PT_GETFPREGS:
225 #ifdef PT_GETDBREGS
226 	case PT_GETDBREGS:
227 #endif
228 		break;
229 	case PT_SETREGS:
230 		error = copyin(uap->addr, &r.reg, sizeof r.reg);
231 		break;
232 	case PT_SETFPREGS:
233 		error = copyin(uap->addr, &r.fpreg, sizeof r.fpreg);
234 		break;
235 #ifdef PT_SETDBREGS
236 	case PT_SETDBREGS:
237 		error = copyin(uap->addr, &r.dbreg, sizeof r.dbreg);
238 		break;
239 #endif
240 	case PT_IO:
241 		error = copyin(uap->addr, &r.piod, sizeof r.piod);
242 		break;
243 	default:
244 		addr = uap->addr;
245 	}
246 	if (error)
247 		return (error);
248 
249 	error = kern_ptrace(p, uap->req, uap->pid, addr, uap->data,
250 			&uap->sysmsg_result);
251 	if (error)
252 		return (error);
253 
254 	switch (uap->req) {
255 	case PT_IO:
256 		(void)copyout(&r.piod, uap->addr, sizeof r.piod);
257 		break;
258 	case PT_GETREGS:
259 		error = copyout(&r.reg, uap->addr, sizeof r.reg);
260 		break;
261 	case PT_GETFPREGS:
262 		error = copyout(&r.fpreg, uap->addr, sizeof r.fpreg);
263 		break;
264 #ifdef PT_GETDBREGS
265 	case PT_GETDBREGS:
266 		error = copyout(&r.dbreg, uap->addr, sizeof r.dbreg);
267 		break;
268 #endif
269 	}
270 
271 	return (error);
272 }
273 
274 int
275 kern_ptrace(struct proc *curp, int req, pid_t pid, void *addr,
276 	    int data, int *res)
277 {
278 	struct proc *p, *pp;
279 	struct lwp *lp;
280 	struct iovec iov;
281 	struct uio uio;
282 	struct ptrace_io_desc *piod;
283 	int error = 0;
284 	int write, tmp;
285 	int t;
286 
287 	write = 0;
288 	if (req == PT_TRACE_ME) {
289 		p = curp;
290 		PHOLD(p);
291 	} else {
292 		if ((p = pfind(pid)) == NULL)
293 			return ESRCH;
294 	}
295 	if (!PRISON_CHECK(curp->p_ucred, p->p_ucred)) {
296 		PRELE(p);
297 		return (ESRCH);
298 	}
299 	if (p->p_flags & P_SYSTEM) {
300 		PRELE(p);
301 		return EINVAL;
302 	}
303 
304 	lwkt_gettoken(&p->p_token);
305 	/* Can't trace a process that's currently exec'ing. */
306 	if ((p->p_flags & P_INEXEC) != 0) {
307 		lwkt_reltoken(&p->p_token);
308 		PRELE(p);
309 		return EAGAIN;
310 	}
311 
312 	/*
313 	 * Permissions check
314 	 */
315 	switch (req) {
316 	case PT_TRACE_ME:
317 		/* Always legal. */
318 		break;
319 
320 	case PT_ATTACH:
321 		/* Self */
322 		if (p->p_pid == curp->p_pid) {
323 			lwkt_reltoken(&p->p_token);
324 			PRELE(p);
325 			return EINVAL;
326 		}
327 
328 		/* Already traced */
329 		if (p->p_flags & P_TRACED) {
330 			lwkt_reltoken(&p->p_token);
331 			PRELE(p);
332 			return EBUSY;
333 		}
334 
335 		if (curp->p_flags & P_TRACED)
336 			for (pp = curp->p_pptr; pp != NULL; pp = pp->p_pptr)
337 				if (pp == p) {
338 					lwkt_reltoken(&p->p_token);
339 					PRELE(p);
340 					return (EINVAL);
341 				}
342 
343 		/* not owned by you, has done setuid (unless you're root) */
344 		if ((p->p_ucred->cr_ruid != curp->p_ucred->cr_ruid) ||
345 		     (p->p_flags & P_SUGID)) {
346 			if ((error = priv_check_cred(curp->p_ucred, PRIV_ROOT, 0)) != 0) {
347 				lwkt_reltoken(&p->p_token);
348 				PRELE(p);
349 				return error;
350 			}
351 		}
352 
353 		/* can't trace init when securelevel > 0 */
354 		if (securelevel > 0 && p->p_pid == 1) {
355 			lwkt_reltoken(&p->p_token);
356 			PRELE(p);
357 			return EPERM;
358 		}
359 
360 		/* OK */
361 		break;
362 
363 	case PT_READ_I:
364 	case PT_READ_D:
365 	case PT_WRITE_I:
366 	case PT_WRITE_D:
367 	case PT_IO:
368 	case PT_CONTINUE:
369 	case PT_KILL:
370 	case PT_STEP:
371 	case PT_DETACH:
372 #ifdef PT_GETREGS
373 	case PT_GETREGS:
374 #endif
375 #ifdef PT_SETREGS
376 	case PT_SETREGS:
377 #endif
378 #ifdef PT_GETFPREGS
379 	case PT_GETFPREGS:
380 #endif
381 #ifdef PT_SETFPREGS
382 	case PT_SETFPREGS:
383 #endif
384 #ifdef PT_GETDBREGS
385 	case PT_GETDBREGS:
386 #endif
387 #ifdef PT_SETDBREGS
388 	case PT_SETDBREGS:
389 #endif
390 		/* not being traced... */
391 		if ((p->p_flags & P_TRACED) == 0) {
392 			lwkt_reltoken(&p->p_token);
393 			PRELE(p);
394 			return EPERM;
395 		}
396 
397 		/* not being traced by YOU */
398 		if (p->p_pptr != curp) {
399 			lwkt_reltoken(&p->p_token);
400 			PRELE(p);
401 			return EBUSY;
402 		}
403 
404 		/* not currently stopped */
405 		if (p->p_stat != SSTOP ||
406 		    (p->p_flags & P_WAITED) == 0) {
407 			lwkt_reltoken(&p->p_token);
408 			PRELE(p);
409 			return EBUSY;
410 		}
411 
412 		/* OK */
413 		break;
414 
415 	default:
416 		lwkt_reltoken(&p->p_token);
417 		PRELE(p);
418 		return EINVAL;
419 	}
420 
421 	/* XXX lwp */
422 	lp = FIRST_LWP_IN_PROC(p);
423 #ifdef FIX_SSTEP
424 	/*
425 	 * Single step fixup ala procfs
426 	 */
427 	FIX_SSTEP(lp);
428 #endif
429 
430 	/*
431 	 * Actually do the requests
432 	 */
433 
434 	*res = 0;
435 
436 	switch (req) {
437 	case PT_TRACE_ME:
438 		/* set my trace flag and "owner" so it can read/write me */
439 		p->p_flags |= P_TRACED;
440 		p->p_oppid = p->p_pptr->p_pid;
441 		lwkt_reltoken(&p->p_token);
442 		PRELE(p);
443 		return 0;
444 
445 	case PT_ATTACH:
446 		/* security check done above */
447 		p->p_flags |= P_TRACED;
448 		p->p_oppid = p->p_pptr->p_pid;
449 		proc_reparent(p, curp);
450 		data = SIGSTOP;
451 		goto sendsig;	/* in PT_CONTINUE below */
452 
453 	case PT_STEP:
454 	case PT_CONTINUE:
455 	case PT_DETACH:
456 		/* Zero means do not send any signal */
457 		if (data < 0 || data > _SIG_MAXSIG) {
458 			lwkt_reltoken(&p->p_token);
459 			PRELE(p);
460 			return EINVAL;
461 		}
462 
463 		LWPHOLD(lp);
464 
465 		if (req == PT_STEP) {
466 			if ((error = ptrace_single_step (lp))) {
467 				LWPRELE(lp);
468 				lwkt_reltoken(&p->p_token);
469 				PRELE(p);
470 				return error;
471 			}
472 		}
473 
474 		if (addr != (void *)1) {
475 			if ((error = ptrace_set_pc (lp,
476 			    (u_long)(uintfptr_t)addr))) {
477 				LWPRELE(lp);
478 				lwkt_reltoken(&p->p_token);
479 				PRELE(p);
480 				return error;
481 			}
482 		}
483 		LWPRELE(lp);
484 
485 		if (req == PT_DETACH) {
486 			/* reset process parent */
487 			if (p->p_oppid != p->p_pptr->p_pid) {
488 				struct proc *pp;
489 
490 				pp = pfind(p->p_oppid);
491 				if (pp) {
492 					proc_reparent(p, pp);
493 					PRELE(pp);
494 				}
495 			}
496 
497 			p->p_flags &= ~(P_TRACED | P_WAITED);
498 			p->p_oppid = 0;
499 
500 			/* should we send SIGCHLD? */
501 		}
502 
503 	sendsig:
504 		/*
505 		 * Deliver or queue signal.  If the process is stopped
506 		 * force it to be SACTIVE again.
507 		 */
508 		crit_enter();
509 		if (p->p_stat == SSTOP) {
510 			p->p_xstat = data;
511 			proc_unstop(p);
512 		} else if (data) {
513 			ksignal(p, data);
514 		}
515 		crit_exit();
516 		lwkt_reltoken(&p->p_token);
517 		PRELE(p);
518 		return 0;
519 
520 	case PT_WRITE_I:
521 	case PT_WRITE_D:
522 		write = 1;
523 		/* fallthrough */
524 	case PT_READ_I:
525 	case PT_READ_D:
526 		/*
527 		 * NOTE! uio_offset represents the offset in the target
528 		 * process.  The iov is in the current process (the guy
529 		 * making the ptrace call) so uio_td must be the current
530 		 * process (though for a SYSSPACE transfer it doesn't
531 		 * really matter).
532 		 */
533 		tmp = 0;
534 		/* write = 0 set above */
535 		iov.iov_base = write ? (caddr_t)&data : (caddr_t)&tmp;
536 		iov.iov_len = sizeof(int);
537 		uio.uio_iov = &iov;
538 		uio.uio_iovcnt = 1;
539 		uio.uio_offset = (off_t)(uintptr_t)addr;
540 		uio.uio_resid = sizeof(int);
541 		uio.uio_segflg = UIO_SYSSPACE;
542 		uio.uio_rw = write ? UIO_WRITE : UIO_READ;
543 		uio.uio_td = curthread;
544 		error = procfs_domem(curp, lp, NULL, &uio);
545 		if (uio.uio_resid != 0) {
546 			/*
547 			 * XXX procfs_domem() doesn't currently return ENOSPC,
548 			 * so I think write() can bogusly return 0.
549 			 * XXX what happens for short writes?  We don't want
550 			 * to write partial data.
551 			 * XXX procfs_domem() returns EPERM for other invalid
552 			 * addresses.  Convert this to EINVAL.  Does this
553 			 * clobber returns of EPERM for other reasons?
554 			 */
555 			if (error == 0 || error == ENOSPC || error == EPERM)
556 				error = EINVAL;	/* EOF */
557 		}
558 		if (!write)
559 			*res = tmp;
560 		lwkt_reltoken(&p->p_token);
561 		PRELE(p);
562 		return (error);
563 
564 	case PT_IO:
565 		/*
566 		 * NOTE! uio_offset represents the offset in the target
567 		 * process.  The iov is in the current process (the guy
568 		 * making the ptrace call) so uio_td must be the current
569 		 * process.
570 		 */
571 		piod = addr;
572 		iov.iov_base = piod->piod_addr;
573 		iov.iov_len = piod->piod_len;
574 		uio.uio_iov = &iov;
575 		uio.uio_iovcnt = 1;
576 		uio.uio_offset = (off_t)(uintptr_t)piod->piod_offs;
577 		uio.uio_resid = piod->piod_len;
578 		uio.uio_segflg = UIO_USERSPACE;
579 		uio.uio_td = curthread;
580 		switch (piod->piod_op) {
581 		case PIOD_READ_D:
582 		case PIOD_READ_I:
583 			uio.uio_rw = UIO_READ;
584 			break;
585 		case PIOD_WRITE_D:
586 		case PIOD_WRITE_I:
587 			uio.uio_rw = UIO_WRITE;
588 			break;
589 		default:
590 			lwkt_reltoken(&p->p_token);
591 			PRELE(p);
592 			return (EINVAL);
593 		}
594 		error = procfs_domem(curp, lp, NULL, &uio);
595 		piod->piod_len -= uio.uio_resid;
596 		lwkt_reltoken(&p->p_token);
597 		PRELE(p);
598 		return (error);
599 
600 	case PT_KILL:
601 		data = SIGKILL;
602 		goto sendsig;	/* in PT_CONTINUE above */
603 
604 #ifdef PT_SETREGS
605 	case PT_SETREGS:
606 		write = 1;
607 		/* fallthrough */
608 #endif /* PT_SETREGS */
609 #ifdef PT_GETREGS
610 	case PT_GETREGS:
611 		/* write = 0 above */
612 #endif /* PT_SETREGS */
613 #if defined(PT_SETREGS) || defined(PT_GETREGS)
614 		if (!procfs_validregs(lp)) {
615 			lwkt_reltoken(&p->p_token);
616 			PRELE(p);
617 			return EINVAL;
618 		} else {
619 			iov.iov_base = addr;
620 			iov.iov_len = sizeof(struct reg);
621 			uio.uio_iov = &iov;
622 			uio.uio_iovcnt = 1;
623 			uio.uio_offset = 0;
624 			uio.uio_resid = sizeof(struct reg);
625 			uio.uio_segflg = UIO_SYSSPACE;
626 			uio.uio_rw = write ? UIO_WRITE : UIO_READ;
627 			uio.uio_td = curthread;
628 			t = procfs_doregs(curp, lp, NULL, &uio);
629 			lwkt_reltoken(&p->p_token);
630 			PRELE(p);
631 			return t;
632 		}
633 #endif /* defined(PT_SETREGS) || defined(PT_GETREGS) */
634 
635 #ifdef PT_SETFPREGS
636 	case PT_SETFPREGS:
637 		write = 1;
638 		/* fallthrough */
639 #endif /* PT_SETFPREGS */
640 #ifdef PT_GETFPREGS
641 	case PT_GETFPREGS:
642 		/* write = 0 above */
643 #endif /* PT_SETFPREGS */
644 #if defined(PT_SETFPREGS) || defined(PT_GETFPREGS)
645 		if (!procfs_validfpregs(lp)) {
646 			lwkt_reltoken(&p->p_token);
647 			PRELE(p);
648 			return EINVAL;
649 		} else {
650 			iov.iov_base = addr;
651 			iov.iov_len = sizeof(struct fpreg);
652 			uio.uio_iov = &iov;
653 			uio.uio_iovcnt = 1;
654 			uio.uio_offset = 0;
655 			uio.uio_resid = sizeof(struct fpreg);
656 			uio.uio_segflg = UIO_SYSSPACE;
657 			uio.uio_rw = write ? UIO_WRITE : UIO_READ;
658 			uio.uio_td = curthread;
659 			t = procfs_dofpregs(curp, lp, NULL, &uio);
660 			lwkt_reltoken(&p->p_token);
661 			PRELE(p);
662 			return t;
663 		}
664 #endif /* defined(PT_SETFPREGS) || defined(PT_GETFPREGS) */
665 
666 #ifdef PT_SETDBREGS
667 	case PT_SETDBREGS:
668 		write = 1;
669 		/* fallthrough */
670 #endif /* PT_SETDBREGS */
671 #ifdef PT_GETDBREGS
672 	case PT_GETDBREGS:
673 		/* write = 0 above */
674 #endif /* PT_SETDBREGS */
675 #if defined(PT_SETDBREGS) || defined(PT_GETDBREGS)
676 		if (!procfs_validdbregs(lp)) {
677 			lwkt_reltoken(&p->p_token);
678 			PRELE(p);
679 			return EINVAL;
680 		} else {
681 			iov.iov_base = addr;
682 			iov.iov_len = sizeof(struct dbreg);
683 			uio.uio_iov = &iov;
684 			uio.uio_iovcnt = 1;
685 			uio.uio_offset = 0;
686 			uio.uio_resid = sizeof(struct dbreg);
687 			uio.uio_segflg = UIO_SYSSPACE;
688 			uio.uio_rw = write ? UIO_WRITE : UIO_READ;
689 			uio.uio_td = curthread;
690 			t = procfs_dodbregs(curp, lp, NULL, &uio);
691 			lwkt_reltoken(&p->p_token);
692 			PRELE(p);
693 			return t;
694 		}
695 #endif /* defined(PT_SETDBREGS) || defined(PT_GETDBREGS) */
696 
697 	default:
698 		break;
699 	}
700 
701 	lwkt_reltoken(&p->p_token);
702 	PRELE(p);
703 
704 	return 0;
705 }
706 
707 int
708 trace_req(struct proc *p)
709 {
710 	return 1;
711 }
712 
713 /*
714  * stopevent()
715  *
716  * Stop a process because of a procfs event.  Stay stopped until p->p_step
717  * is cleared (cleared by PIOCCONT in procfs).
718  *
719  * MPSAFE
720  */
721 void
722 stopevent(struct proc *p, unsigned int event, unsigned int val)
723 {
724 	/*
725 	 * Set event info.  Recheck p_stops in case we are
726 	 * racing a close() on procfs.
727 	 */
728 	spin_lock(&p->p_spin);
729 	if ((p->p_stops & event) == 0) {
730 		spin_unlock(&p->p_spin);
731 		return;
732 	}
733 	p->p_xstat = val;
734 	p->p_stype = event;
735 	p->p_step = 1;
736 	tsleep_interlock(&p->p_step, 0);
737 	spin_unlock(&p->p_spin);
738 
739 	/*
740 	 * Wakeup any PIOCWAITing procs and wait for p_step to
741 	 * be cleared.
742 	 */
743 	for (;;) {
744 		wakeup(&p->p_stype);
745 		tsleep(&p->p_step, PINTERLOCKED, "stopevent", 0);
746 		spin_lock(&p->p_spin);
747 		if (p->p_step == 0) {
748 			spin_unlock(&p->p_spin);
749 			break;
750 		}
751 		tsleep_interlock(&p->p_step, 0);
752 		spin_unlock(&p->p_spin);
753 	}
754 }
755 
756