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procfs_subr.c revision 1.66
      1 /*	$NetBSD: procfs_subr.c,v 1.66 2005/10/01 03:17:37 atatat Exp $	*/
      2 
      3 /*
      4  * Copyright (c) 1993
      5  *	The Regents of the University of California.  All rights reserved.
      6  *
      7  * This code is derived from software contributed to Berkeley by
      8  * Jan-Simon Pendry.
      9  *
     10  * Redistribution and use in source and binary forms, with or without
     11  * modification, are permitted provided that the following conditions
     12  * are met:
     13  * 1. Redistributions of source code must retain the above copyright
     14  *    notice, this list of conditions and the following disclaimer.
     15  * 2. Redistributions in binary form must reproduce the above copyright
     16  *    notice, this list of conditions and the following disclaimer in the
     17  *    documentation and/or other materials provided with the distribution.
     18  * 3. Neither the name of the University nor the names of its contributors
     19  *    may be used to endorse or promote products derived from this software
     20  *    without specific prior written permission.
     21  *
     22  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     23  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     24  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     25  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     26  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     27  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     28  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     29  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     30  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     31  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     32  * SUCH DAMAGE.
     33  *
     34  *	@(#)procfs_subr.c	8.6 (Berkeley) 5/14/95
     35  */
     36 
     37 /*
     38  * Copyright (c) 1994 Christopher G. Demetriou.  All rights reserved.
     39  * Copyright (c) 1993 Jan-Simon Pendry
     40  *
     41  * This code is derived from software contributed to Berkeley by
     42  * Jan-Simon Pendry.
     43  *
     44  * Redistribution and use in source and binary forms, with or without
     45  * modification, are permitted provided that the following conditions
     46  * are met:
     47  * 1. Redistributions of source code must retain the above copyright
     48  *    notice, this list of conditions and the following disclaimer.
     49  * 2. Redistributions in binary form must reproduce the above copyright
     50  *    notice, this list of conditions and the following disclaimer in the
     51  *    documentation and/or other materials provided with the distribution.
     52  * 3. All advertising materials mentioning features or use of this software
     53  *    must display the following acknowledgement:
     54  *	This product includes software developed by the University of
     55  *	California, Berkeley and its contributors.
     56  * 4. Neither the name of the University nor the names of its contributors
     57  *    may be used to endorse or promote products derived from this software
     58  *    without specific prior written permission.
     59  *
     60  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     61  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     62  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     63  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     64  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     65  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     66  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     67  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     68  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     69  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     70  * SUCH DAMAGE.
     71  *
     72  *	@(#)procfs_subr.c	8.6 (Berkeley) 5/14/95
     73  */
     74 
     75 #include <sys/cdefs.h>
     76 __KERNEL_RCSID(0, "$NetBSD: procfs_subr.c,v 1.66 2005/10/01 03:17:37 atatat Exp $");
     77 
     78 #include <sys/param.h>
     79 #include <sys/systm.h>
     80 #include <sys/time.h>
     81 #include <sys/kernel.h>
     82 #include <sys/proc.h>
     83 #include <sys/vnode.h>
     84 #include <sys/malloc.h>
     85 #include <sys/stat.h>
     86 #include <sys/file.h>
     87 #include <sys/filedesc.h>
     88 
     89 #include <miscfs/procfs/procfs.h>
     90 
     91 void procfs_hashins(struct pfsnode *);
     92 void procfs_hashrem(struct pfsnode *);
     93 struct vnode *procfs_hashget(pid_t, pfstype, int, struct mount *);
     94 
     95 LIST_HEAD(pfs_hashhead, pfsnode) *pfs_hashtbl;
     96 u_long	pfs_ihash;	/* size of hash table - 1 */
     97 #define PFSPIDHASH(pid)	((pid) & pfs_ihash)
     98 
     99 struct lock pfs_hashlock;
    100 struct simplelock pfs_hash_slock;
    101 
    102 #define	ISSET(t, f)	((t) & (f))
    103 
    104 /*
    105  * allocate a pfsnode/vnode pair.  the vnode is
    106  * referenced, and locked.
    107  *
    108  * the pid, pfs_type, and mount point uniquely
    109  * identify a pfsnode.  the mount point is needed
    110  * because someone might mount this filesystem
    111  * twice.
    112  *
    113  * all pfsnodes are maintained on a singly-linked
    114  * list.  new nodes are only allocated when they cannot
    115  * be found on this list.  entries on the list are
    116  * removed when the vfs reclaim entry is called.
    117  *
    118  * a single lock is kept for the entire list.  this is
    119  * needed because the getnewvnode() function can block
    120  * waiting for a vnode to become free, in which case there
    121  * may be more than one process trying to get the same
    122  * vnode.  this lock is only taken if we are going to
    123  * call getnewvnode, since the kernel itself is single-threaded.
    124  *
    125  * if an entry is found on the list, then call vget() to
    126  * take a reference.  this is done because there may be
    127  * zero references to it and so it needs to removed from
    128  * the vnode free list.
    129  */
    130 int
    131 procfs_allocvp(mp, vpp, pid, pfs_type, fd)
    132 	struct mount *mp;
    133 	struct vnode **vpp;
    134 	pid_t pid;
    135 	pfstype pfs_type;
    136 	int fd;
    137 {
    138 	struct pfsnode *pfs;
    139 	struct vnode *vp;
    140 	int error;
    141 
    142 	do {
    143 		if ((*vpp = procfs_hashget(pid, pfs_type, fd, mp)) != NULL)
    144 			return (0);
    145 	} while (lockmgr(&pfs_hashlock, LK_EXCLUSIVE|LK_SLEEPFAIL, 0));
    146 
    147 	if ((error = getnewvnode(VT_PROCFS, mp, procfs_vnodeop_p, &vp)) != 0) {
    148 		*vpp = NULL;
    149 		lockmgr(&pfs_hashlock, LK_RELEASE, NULL);
    150 		return (error);
    151 	}
    152 
    153 	MALLOC(pfs, void *, sizeof(struct pfsnode), M_TEMP, M_WAITOK);
    154 	vp->v_data = pfs;
    155 
    156 	pfs->pfs_pid = pid;
    157 	pfs->pfs_type = pfs_type;
    158 	pfs->pfs_vnode = vp;
    159 	pfs->pfs_flags = 0;
    160 	pfs->pfs_fileno = PROCFS_FILENO(pid, pfs_type, fd);
    161 	pfs->pfs_fd = fd;
    162 
    163 	switch (pfs_type) {
    164 	case PFSroot:	/* /proc = dr-xr-xr-x */
    165 		pfs->pfs_mode = S_IRUSR|S_IXUSR|S_IRGRP|S_IXGRP|S_IROTH|S_IXOTH;
    166 		vp->v_type = VDIR;
    167 		vp->v_flag = VROOT;
    168 		break;
    169 
    170 	case PFScurproc:	/* /proc/curproc = lr-xr-xr-x */
    171 	case PFSself:	/* /proc/self    = lr-xr-xr-x */
    172 	case PFScwd:	/* /proc/N/cwd = lr-xr-xr-x */
    173 	case PFSchroot:	/* /proc/N/chroot = lr-xr-xr-x */
    174 		pfs->pfs_mode = S_IRUSR|S_IXUSR|S_IRGRP|S_IXGRP|S_IROTH|S_IXOTH;
    175 		vp->v_type = VLNK;
    176 		break;
    177 
    178 	case PFSproc:	/* /proc/N = dr-xr-xr-x */
    179 	case PFSfd:
    180 		if (fd == -1) {	/* /proc/N/fd = dr-xr-xr-x */
    181 			pfs->pfs_mode = S_IRUSR|S_IXUSR;
    182 			vp->v_type = VDIR;
    183 		} else {	/* /proc/N/fd/M = [ps-]rw------- */
    184 			struct file *fp;
    185 			struct vnode *vxp;
    186 			struct proc *pown;
    187 
    188 			/* XXX can procfs_getfp() ever fail here? */
    189 			if ((error = procfs_getfp(pfs, &pown, &fp)) != 0)
    190 				goto bad;
    191 			FILE_USE(fp);
    192 
    193 			pfs->pfs_mode = S_IRUSR|S_IWUSR;
    194 			switch (fp->f_type) {
    195 			case DTYPE_VNODE:
    196 				vxp = (struct vnode *)fp->f_data;
    197 
    198 				/*
    199 				 * We make symlinks for directories
    200 				 * to avoid cycles.
    201 				 */
    202 				if (vxp->v_type == VDIR)
    203 					goto symlink;
    204 				vp->v_type = vxp->v_type;
    205 				break;
    206 			case DTYPE_PIPE:
    207 				vp->v_type = VFIFO;
    208 				break;
    209 			case DTYPE_SOCKET:
    210 				vp->v_type = VSOCK;
    211 				break;
    212 			case DTYPE_KQUEUE:
    213 			case DTYPE_MISC:
    214 			symlink:
    215 				pfs->pfs_mode = S_IRUSR|S_IXUSR|S_IRGRP|
    216 				    S_IXGRP|S_IROTH|S_IXOTH;
    217 				vp->v_type = VLNK;
    218 				break;
    219 			default:
    220 				error = EOPNOTSUPP;
    221 				FILE_UNUSE(fp, pown);
    222 				goto bad;
    223 			}
    224 			FILE_UNUSE(fp, pown);
    225 		}
    226 		break;
    227 
    228 	case PFSfile:	/* /proc/N/file = -rw------- */
    229 	case PFSmem:	/* /proc/N/mem = -rw------- */
    230 	case PFSregs:	/* /proc/N/regs = -rw------- */
    231 	case PFSfpregs:	/* /proc/N/fpregs = -rw------- */
    232 		pfs->pfs_mode = S_IRUSR|S_IWUSR;
    233 		vp->v_type = VREG;
    234 		break;
    235 
    236 	case PFSctl:	/* /proc/N/ctl = --w------ */
    237 	case PFSnote:	/* /proc/N/note = --w------ */
    238 	case PFSnotepg:	/* /proc/N/notepg = --w------ */
    239 		pfs->pfs_mode = S_IWUSR;
    240 		vp->v_type = VREG;
    241 		break;
    242 
    243 	case PFSmap:	/* /proc/N/map = -r--r--r-- */
    244 	case PFSmaps:	/* /proc/N/maps = -r--r--r-- */
    245 	case PFSstatus:	/* /proc/N/status = -r--r--r-- */
    246 	case PFSstat:	/* /proc/N/stat = -r--r--r-- */
    247 	case PFScmdline:	/* /proc/N/cmdline = -r--r--r-- */
    248 	case PFSmeminfo:	/* /proc/meminfo = -r--r--r-- */
    249 	case PFScpuinfo:	/* /proc/cpuinfo = -r--r--r-- */
    250 	case PFSuptime:	/* /proc/uptime = -r--r--r-- */
    251 	case PFSmounts:	/* /proc/mounts = -r--r--r-- */
    252 		pfs->pfs_mode = S_IRUSR|S_IRGRP|S_IROTH;
    253 		vp->v_type = VREG;
    254 		break;
    255 
    256 #ifdef __HAVE_PROCFS_MACHDEP
    257 	PROCFS_MACHDEP_NODETYPE_CASES
    258 		procfs_machdep_allocvp(vp);
    259 		break;
    260 #endif
    261 
    262 	default:
    263 		panic("procfs_allocvp");
    264 	}
    265 
    266 	procfs_hashins(pfs);
    267 	uvm_vnp_setsize(vp, 0);
    268 	lockmgr(&pfs_hashlock, LK_RELEASE, NULL);
    269 
    270 	*vpp = vp;
    271 	return (0);
    272 
    273  bad:
    274 	lockmgr(&pfs_hashlock, LK_RELEASE, NULL);
    275 	FREE(pfs, M_TEMP);
    276 	ungetnewvnode(vp);
    277 	return (error);
    278 }
    279 
    280 int
    281 procfs_freevp(vp)
    282 	struct vnode *vp;
    283 {
    284 	struct pfsnode *pfs = VTOPFS(vp);
    285 
    286 	procfs_hashrem(pfs);
    287 
    288 	FREE(vp->v_data, M_TEMP);
    289 	vp->v_data = 0;
    290 	return (0);
    291 }
    292 
    293 int
    294 procfs_rw(v)
    295 	void *v;
    296 {
    297 	struct vop_read_args *ap = v;
    298 	struct vnode *vp = ap->a_vp;
    299 	struct uio *uio = ap->a_uio;
    300 	struct proc *curp = uio->uio_procp;
    301 	struct pfsnode *pfs = VTOPFS(vp);
    302 	struct lwp *l;
    303 	struct proc *p;
    304 
    305 	if (uio->uio_offset < 0)
    306 		return EINVAL;
    307 	p = PFIND(pfs->pfs_pid);
    308 	if (p == 0)
    309 		return ESRCH;
    310 	/*
    311 	 * Do not allow init to be modified while in secure mode; it
    312 	 * could be duped into changing the security level.
    313 	 */
    314 	if (uio->uio_rw == UIO_WRITE && p == initproc && securelevel > -1)
    315 		return EPERM;
    316 
    317 	/* XXX NJWLWP
    318 	 * The entire procfs interface needs work to be useful to
    319 	 * a process with multiple LWPs. For the moment, we'll
    320 	 * just kluge this and fail on others.
    321 	 */
    322 	l = proc_representative_lwp(p);
    323 
    324 	switch (pfs->pfs_type) {
    325 	case PFSnote:
    326 	case PFSnotepg:
    327 		return (procfs_donote(curp, p, pfs, uio));
    328 
    329 	case PFSregs:
    330 		return (procfs_doregs(curp, l, pfs, uio));
    331 
    332 	case PFSfpregs:
    333 		return (procfs_dofpregs(curp, l, pfs, uio));
    334 
    335 	case PFSctl:
    336 		return (procfs_doctl(curp, l, pfs, uio));
    337 
    338 	case PFSstatus:
    339 		return (procfs_dostatus(curp, l, pfs, uio));
    340 
    341 	case PFSstat:
    342 		return (procfs_do_pid_stat(curp, l, pfs, uio));
    343 
    344 	case PFSmap:
    345 		return (procfs_domap(curp, p, pfs, uio, 0));
    346 
    347 	case PFSmaps:
    348 		return (procfs_domap(curp, p, pfs, uio, 1));
    349 
    350 	case PFSmem:
    351 		return (procfs_domem(curp, p, pfs, uio));
    352 
    353 	case PFScmdline:
    354 		return (procfs_docmdline(curp, p, pfs, uio));
    355 
    356 	case PFSmeminfo:
    357 		return (procfs_domeminfo(curp, p, pfs, uio));
    358 
    359 	case PFScpuinfo:
    360 		return (procfs_docpuinfo(curp, p, pfs, uio));
    361 
    362 	case PFSfd:
    363 		return (procfs_dofd(curp, p, pfs, uio));
    364 
    365 	case PFSuptime:
    366 		return (procfs_douptime(curp, p, pfs, uio));
    367 
    368 	case PFSmounts:
    369 		return (procfs_domounts(curp, p, pfs, uio));
    370 
    371 #ifdef __HAVE_PROCFS_MACHDEP
    372 	PROCFS_MACHDEP_NODETYPE_CASES
    373 		return (procfs_machdep_rw(curp, l, pfs, uio));
    374 #endif
    375 
    376 	default:
    377 		return (EOPNOTSUPP);
    378 	}
    379 }
    380 
    381 /*
    382  * Get a string from userland into (bf).  Strip a trailing
    383  * nl character (to allow easy access from the shell).
    384  * The buffer should be *buflenp + 1 chars long.  vfs_getuserstr
    385  * will automatically add a nul char at the end.
    386  *
    387  * Returns 0 on success or the following errors
    388  *
    389  * EINVAL:    file offset is non-zero.
    390  * EMSGSIZE:  message is longer than kernel buffer
    391  * EFAULT:    user i/o buffer is not addressable
    392  */
    393 int
    394 vfs_getuserstr(uio, bf, buflenp)
    395 	struct uio *uio;
    396 	char *bf;
    397 	int *buflenp;
    398 {
    399 	int xlen;
    400 	int error;
    401 
    402 	if (uio->uio_offset != 0)
    403 		return (EINVAL);
    404 
    405 	xlen = *buflenp;
    406 
    407 	/* must be able to read the whole string in one go */
    408 	if (xlen < uio->uio_resid)
    409 		return (EMSGSIZE);
    410 	xlen = uio->uio_resid;
    411 
    412 	if ((error = uiomove(bf, xlen, uio)) != 0)
    413 		return (error);
    414 
    415 	/* allow multiple writes without seeks */
    416 	uio->uio_offset = 0;
    417 
    418 	/* cleanup string and remove trailing newline */
    419 	bf[xlen] = '\0';
    420 	xlen = strlen(bf);
    421 	if (xlen > 0 && bf[xlen-1] == '\n')
    422 		bf[--xlen] = '\0';
    423 	*buflenp = xlen;
    424 
    425 	return (0);
    426 }
    427 
    428 const vfs_namemap_t *
    429 vfs_findname(nm, bf, buflen)
    430 	const vfs_namemap_t *nm;
    431 	const char *bf;
    432 	int buflen;
    433 {
    434 
    435 	for (; nm->nm_name; nm++)
    436 		if (memcmp(bf, nm->nm_name, buflen+1) == 0)
    437 			return (nm);
    438 
    439 	return (0);
    440 }
    441 
    442 /*
    443  * Initialize pfsnode hash table.
    444  */
    445 void
    446 procfs_hashinit()
    447 {
    448 	lockinit(&pfs_hashlock, PINOD, "pfs_hashlock", 0, 0);
    449 	pfs_hashtbl = hashinit(desiredvnodes / 4, HASH_LIST, M_UFSMNT,
    450 	    M_WAITOK, &pfs_ihash);
    451 	simple_lock_init(&pfs_hash_slock);
    452 }
    453 
    454 void
    455 procfs_hashreinit()
    456 {
    457 	struct pfsnode *pp;
    458 	struct pfs_hashhead *oldhash, *hash;
    459 	u_long i, oldmask, mask, val;
    460 
    461 	hash = hashinit(desiredvnodes / 4, HASH_LIST, M_UFSMNT, M_WAITOK,
    462 	    &mask);
    463 
    464 	simple_lock(&pfs_hash_slock);
    465 	oldhash = pfs_hashtbl;
    466 	oldmask = pfs_ihash;
    467 	pfs_hashtbl = hash;
    468 	pfs_ihash = mask;
    469 	for (i = 0; i <= oldmask; i++) {
    470 		while ((pp = LIST_FIRST(&oldhash[i])) != NULL) {
    471 			LIST_REMOVE(pp, pfs_hash);
    472 			val = PFSPIDHASH(pp->pfs_pid);
    473 			LIST_INSERT_HEAD(&hash[val], pp, pfs_hash);
    474 		}
    475 	}
    476 	simple_unlock(&pfs_hash_slock);
    477 	hashdone(oldhash, M_UFSMNT);
    478 }
    479 
    480 /*
    481  * Free pfsnode hash table.
    482  */
    483 void
    484 procfs_hashdone()
    485 {
    486 	hashdone(pfs_hashtbl, M_UFSMNT);
    487 }
    488 
    489 struct vnode *
    490 procfs_hashget(pid, type, fd, mp)
    491 	pid_t pid;
    492 	pfstype type;
    493 	int fd;
    494 	struct mount *mp;
    495 {
    496 	struct pfs_hashhead *ppp;
    497 	struct pfsnode *pp;
    498 	struct vnode *vp;
    499 
    500 loop:
    501 	simple_lock(&pfs_hash_slock);
    502 	ppp = &pfs_hashtbl[PFSPIDHASH(pid)];
    503 	LIST_FOREACH(pp, ppp, pfs_hash) {
    504 		vp = PFSTOV(pp);
    505 		if (pid == pp->pfs_pid && pp->pfs_type == type &&
    506 		    pp->pfs_fd == fd && vp->v_mount == mp) {
    507 			simple_lock(&vp->v_interlock);
    508 			simple_unlock(&pfs_hash_slock);
    509 			if (vget(vp, LK_EXCLUSIVE | LK_INTERLOCK))
    510 				goto loop;
    511 			return (vp);
    512 		}
    513 	}
    514 	simple_unlock(&pfs_hash_slock);
    515 	return (NULL);
    516 }
    517 
    518 /*
    519  * Insert the pfsnode into the hash table and lock it.
    520  */
    521 void
    522 procfs_hashins(pp)
    523 	struct pfsnode *pp;
    524 {
    525 	struct pfs_hashhead *ppp;
    526 
    527 	/* lock the pfsnode, then put it on the appropriate hash list */
    528 	lockmgr(&pp->pfs_vnode->v_lock, LK_EXCLUSIVE, (struct simplelock *)0);
    529 
    530 	simple_lock(&pfs_hash_slock);
    531 	ppp = &pfs_hashtbl[PFSPIDHASH(pp->pfs_pid)];
    532 	LIST_INSERT_HEAD(ppp, pp, pfs_hash);
    533 	simple_unlock(&pfs_hash_slock);
    534 }
    535 
    536 /*
    537  * Remove the pfsnode from the hash table.
    538  */
    539 void
    540 procfs_hashrem(pp)
    541 	struct pfsnode *pp;
    542 {
    543 	simple_lock(&pfs_hash_slock);
    544 	LIST_REMOVE(pp, pfs_hash);
    545 	simple_unlock(&pfs_hash_slock);
    546 }
    547 
    548 void
    549 procfs_revoke_vnodes(p, arg)
    550 	struct proc *p;
    551 	void *arg;
    552 {
    553 	struct pfsnode *pfs, *pnext;
    554 	struct vnode *vp;
    555 	struct mount *mp = (struct mount *)arg;
    556 	struct pfs_hashhead *ppp;
    557 
    558 	if (!(p->p_flag & P_SUGID))
    559 		return;
    560 
    561 	ppp = &pfs_hashtbl[PFSPIDHASH(p->p_pid)];
    562 	for (pfs = LIST_FIRST(ppp); pfs; pfs = pnext) {
    563 		vp = PFSTOV(pfs);
    564 		pnext = LIST_NEXT(pfs, pfs_hash);
    565 		if (vp->v_usecount > 0 && pfs->pfs_pid == p->p_pid &&
    566 		    vp->v_mount == mp)
    567 			VOP_REVOKE(vp, REVOKEALL);
    568 	}
    569 }
    570 
    571 int
    572 procfs_getfp(pfs, pown, fp)
    573 	struct pfsnode *pfs;
    574 	struct proc **pown;
    575 	struct file **fp;
    576 {
    577 	struct proc *p = PFIND(pfs->pfs_pid);
    578 
    579 	if (p == NULL)
    580 		return ESRCH;
    581 
    582 	if (pfs->pfs_fd == -1)
    583 		return EINVAL;
    584 
    585 	if ((*fp = fd_getfile(p->p_fd, pfs->pfs_fd)) == NULL)
    586 		return EBADF;
    587 
    588 	*pown = p;
    589 	return 0;
    590 }
    591