xref: /freebsd/lib/libkvm/kvm_proc.c (revision c17d43407fe04133a94055b0dbc7ea8965654a9f)
1 /*-
2  * Copyright (c) 1989, 1992, 1993
3  *	The Regents of the University of California.  All rights reserved.
4  *
5  * This code is derived from software developed by the Computer Systems
6  * Engineering group at Lawrence Berkeley Laboratory under DARPA contract
7  * BG 91-66 and contributed to Berkeley.
8  *
9  * Redistribution and use in source and binary forms, with or without
10  * modification, are permitted provided that the following conditions
11  * are met:
12  * 1. Redistributions of source code must retain the above copyright
13  *    notice, this list of conditions and the following disclaimer.
14  * 2. Redistributions in binary form must reproduce the above copyright
15  *    notice, this list of conditions and the following disclaimer in the
16  *    documentation and/or other materials provided with the distribution.
17  * 3. All advertising materials mentioning features or use of this software
18  *    must display the following acknowledgement:
19  *	This product includes software developed by the University of
20  *	California, Berkeley and its contributors.
21  * 4. Neither the name of the University nor the names of its contributors
22  *    may be used to endorse or promote products derived from this software
23  *    without specific prior written permission.
24  *
25  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
26  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
27  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
28  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
29  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
30  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
31  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
32  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
33  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
34  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
35  * SUCH DAMAGE.
36  *
37  * $FreeBSD$
38  */
39 
40 #include <sys/cdefs.h>
41 __FBSDID("$FreeBSD$");
42 
43 #if defined(LIBC_SCCS) && !defined(lint)
44 static char sccsid[] = "@(#)kvm_proc.c	8.3 (Berkeley) 9/23/93";
45 #endif /* LIBC_SCCS and not lint */
46 
47 /*
48  * Proc traversal interface for kvm.  ps and w are (probably) the exclusive
49  * users of this code, so we've factored it out into a separate module.
50  * Thus, we keep this grunge out of the other kvm applications (i.e.,
51  * most other applications are interested only in open/close/read/nlist).
52  */
53 
54 #include <sys/param.h>
55 #include <sys/user.h>
56 #include <sys/proc.h>
57 #include <sys/exec.h>
58 #include <sys/stat.h>
59 #include <sys/ioctl.h>
60 #include <sys/tty.h>
61 #include <sys/file.h>
62 #include <stdio.h>
63 #include <stdlib.h>
64 #include <unistd.h>
65 #include <nlist.h>
66 #include <kvm.h>
67 
68 #include <vm/vm.h>
69 #include <vm/vm_param.h>
70 #include <vm/swap_pager.h>
71 
72 #include <sys/sysctl.h>
73 
74 #include <limits.h>
75 #include <memory.h>
76 #include <paths.h>
77 
78 #include "kvm_private.h"
79 
80 #if used
81 static char *
82 kvm_readswap(kd, p, va, cnt)
83 	kvm_t *kd;
84 	const struct proc *p;
85 	u_long va;
86 	u_long *cnt;
87 {
88 #ifdef __FreeBSD__
89 	/* XXX Stubbed out, our vm system is differnet */
90 	_kvm_err(kd, kd->program, "kvm_readswap not implemented");
91 	return(0);
92 #endif	/* __FreeBSD__ */
93 }
94 #endif
95 
96 #define KREAD(kd, addr, obj) \
97 	(kvm_read(kd, addr, (char *)(obj), sizeof(*obj)) != sizeof(*obj))
98 
99 /*
100  * Read proc's from memory file into buffer bp, which has space to hold
101  * at most maxcnt procs.
102  */
103 static int
104 kvm_proclist(kd, what, arg, p, bp, maxcnt)
105 	kvm_t *kd;
106 	int what, arg;
107 	struct proc *p;
108 	struct kinfo_proc *bp;
109 	int maxcnt;
110 {
111 	int cnt = 0;
112 	struct kinfo_proc kinfo_proc, *kp;
113 	struct pgrp pgrp;
114 	struct session sess;
115 	struct tty tty;
116 	struct vmspace vmspace;
117 	struct procsig procsig;
118 	struct pstats pstats;
119 	struct ucred ucred;
120 	struct thread mainthread;
121 	struct proc proc;
122 	struct proc pproc;
123 	struct timeval tv;
124 
125 	kp = &kinfo_proc;
126 	kp->ki_structsize = sizeof(kinfo_proc);
127 	for (; cnt < maxcnt && p != NULL; p = LIST_NEXT(&proc, p_list)) {
128 		memset(kp, 0, sizeof *kp);
129 		if (KREAD(kd, (u_long)p, &proc)) {
130 			_kvm_err(kd, kd->program, "can't read proc at %x", p);
131 			return (-1);
132 		}
133 		if (KREAD(kd, (u_long)TAILQ_FIRST(&proc.p_threads),
134 		    &mainthread)) {
135 			_kvm_err(kd, kd->program, "can't read thread at %x",
136 			    TAILQ_FIRST(&proc.p_threads));
137 			return (-1);
138 		}
139 		if (KREAD(kd, (u_long)proc.p_ucred, &ucred) == 0) {
140 			kp->ki_ruid = ucred.cr_ruid;
141 			kp->ki_svuid = ucred.cr_svuid;
142 			kp->ki_rgid = ucred.cr_rgid;
143 			kp->ki_svgid = ucred.cr_svgid;
144 			kp->ki_ngroups = ucred.cr_ngroups;
145 			bcopy(ucred.cr_groups, kp->ki_groups,
146 			    NGROUPS * sizeof(gid_t));
147 			kp->ki_uid = ucred.cr_uid;
148 		}
149 
150 		switch(what) {
151 
152 		case KERN_PROC_PID:
153 			if (proc.p_pid != (pid_t)arg)
154 				continue;
155 			break;
156 
157 		case KERN_PROC_UID:
158 			if (kp->ki_uid != (uid_t)arg)
159 				continue;
160 			break;
161 
162 		case KERN_PROC_RUID:
163 			if (kp->ki_ruid != (uid_t)arg)
164 				continue;
165 			break;
166 		}
167 		/*
168 		 * We're going to add another proc to the set.  If this
169 		 * will overflow the buffer, assume the reason is because
170 		 * nprocs (or the proc list) is corrupt and declare an error.
171 		 */
172 		if (cnt >= maxcnt) {
173 			_kvm_err(kd, kd->program, "nprocs corrupt");
174 			return (-1);
175 		}
176 		/*
177 		 * gather kinfo_proc
178 		 */
179 		kp->ki_paddr = p;
180 		kp->ki_addr = proc.p_uarea;
181 		/* kp->ki_kstack = proc.p_thread.td_kstack; XXXKSE */
182 		kp->ki_args = proc.p_args;
183 		kp->ki_tracep = proc.p_tracep;
184 		kp->ki_textvp = proc.p_textvp;
185 		kp->ki_fd = proc.p_fd;
186 		kp->ki_vmspace = proc.p_vmspace;
187 		if (proc.p_procsig != NULL) {
188 			if (KREAD(kd, (u_long)proc.p_procsig, &procsig)) {
189 				_kvm_err(kd, kd->program,
190 				    "can't read procsig at %x", proc.p_procsig);
191 				return (-1);
192 			}
193 			kp->ki_sigignore = procsig.ps_sigignore;
194 			kp->ki_sigcatch = procsig.ps_sigcatch;
195 		}
196 		if ((proc.p_sflag & PS_INMEM) && proc.p_stats != NULL) {
197 			if (KREAD(kd, (u_long)proc.p_stats, &pstats)) {
198 				_kvm_err(kd, kd->program,
199 				    "can't read stats at %x", proc.p_stats);
200 				return (-1);
201 			}
202 			kp->ki_start = pstats.p_start;
203 			kp->ki_rusage = pstats.p_ru;
204 			kp->ki_childtime.tv_sec = pstats.p_cru.ru_utime.tv_sec +
205 			    pstats.p_cru.ru_stime.tv_sec;
206 			kp->ki_childtime.tv_usec =
207 			    pstats.p_cru.ru_utime.tv_usec +
208 			    pstats.p_cru.ru_stime.tv_usec;
209 		}
210 		if (proc.p_oppid)
211 			kp->ki_ppid = proc.p_oppid;
212 		else if (proc.p_pptr) {
213 			if (KREAD(kd, (u_long)proc.p_pptr, &pproc)) {
214 				_kvm_err(kd, kd->program,
215 				    "can't read pproc at %x", proc.p_pptr);
216 				return (-1);
217 			}
218 			kp->ki_ppid = pproc.p_pid;
219 		} else
220 			kp->ki_ppid = 0;
221 		if (proc.p_pgrp == NULL)
222 			goto nopgrp;
223 		if (KREAD(kd, (u_long)proc.p_pgrp, &pgrp)) {
224 			_kvm_err(kd, kd->program, "can't read pgrp at %x",
225 				 proc.p_pgrp);
226 			return (-1);
227 		}
228 		kp->ki_pgid = pgrp.pg_id;
229 		kp->ki_jobc = pgrp.pg_jobc;
230 		if (KREAD(kd, (u_long)pgrp.pg_session, &sess)) {
231 			_kvm_err(kd, kd->program, "can't read session at %x",
232 				pgrp.pg_session);
233 			return (-1);
234 		}
235 		kp->ki_sid = sess.s_sid;
236 		(void)memcpy(kp->ki_login, sess.s_login,
237 						sizeof(kp->ki_login));
238 		kp->ki_kiflag = sess.s_ttyvp ? KI_CTTY : 0;
239 		if (sess.s_leader == p)
240 			kp->ki_kiflag |= KI_SLEADER;
241 		if ((proc.p_flag & P_CONTROLT) && sess.s_ttyp != NULL) {
242 			if (KREAD(kd, (u_long)sess.s_ttyp, &tty)) {
243 				_kvm_err(kd, kd->program,
244 					 "can't read tty at %x", sess.s_ttyp);
245 				return (-1);
246 			}
247 			kp->ki_tdev = tty.t_dev;
248 			if (tty.t_pgrp != NULL) {
249 				if (KREAD(kd, (u_long)tty.t_pgrp, &pgrp)) {
250 					_kvm_err(kd, kd->program,
251 						 "can't read tpgrp at &x",
252 						tty.t_pgrp);
253 					return (-1);
254 				}
255 				kp->ki_tpgid = pgrp.pg_id;
256 			} else
257 				kp->ki_tpgid = -1;
258 			if (tty.t_session != NULL) {
259 				if (KREAD(kd, (u_long)tty.t_session, &sess)) {
260 					_kvm_err(kd, kd->program,
261 					    "can't read session at %x",
262 					    tty.t_session);
263 					return (-1);
264 				}
265 				kp->ki_tsid = sess.s_sid;
266 			}
267 		} else {
268 nopgrp:
269 			kp->ki_tdev = NODEV;
270 		}
271 		if (mainthread.td_wmesg)	/* XXXKSE */
272 			(void)kvm_read(kd, (u_long)mainthread.td_wmesg,
273 			    kp->ki_wmesg, WMESGLEN);
274 
275 #ifdef sparc
276 		(void)kvm_read(kd, (u_long)&proc.p_vmspace->vm_rssize,
277 		    (char *)&kp->ki_rssize,
278 		    sizeof(kp->ki_rssize));
279 		(void)kvm_read(kd, (u_long)&proc.p_vmspace->vm_tsize,
280 		    (char *)&kp->ki_tsize,
281 		    3 * sizeof(kp->ki_rssize));	/* XXX */
282 #else
283 		(void)kvm_read(kd, (u_long)proc.p_vmspace,
284 		    (char *)&vmspace, sizeof(vmspace));
285 		kp->ki_size = vmspace.vm_map.size;
286 		kp->ki_rssize = vmspace.vm_swrss; /* XXX */
287 		kp->ki_swrss = vmspace.vm_swrss;
288 		kp->ki_tsize = vmspace.vm_tsize;
289 		kp->ki_dsize = vmspace.vm_dsize;
290 		kp->ki_ssize = vmspace.vm_ssize;
291 #endif
292 
293 		switch (what) {
294 
295 		case KERN_PROC_PGRP:
296 			if (kp->ki_pgid != (pid_t)arg)
297 				continue;
298 			break;
299 
300 		case KERN_PROC_TTY:
301 			if ((proc.p_flag & P_CONTROLT) == 0 ||
302 			     kp->ki_tdev != (dev_t)arg)
303 				continue;
304 			break;
305 		}
306 		if (proc.p_comm[0] != 0) {
307 			strncpy(kp->ki_comm, proc.p_comm, MAXCOMLEN);
308 			kp->ki_comm[MAXCOMLEN] = 0;
309 		}
310 		if (mainthread.td_blocked != 0) {	/* XXXKSE */
311 			kp->ki_kiflag |= KI_MTXBLOCK;
312 			if (mainthread.td_mtxname)	/* XXXKSE */
313 				(void)kvm_read(kd, (u_long)mainthread.td_mtxname,
314 				    kp->ki_mtxname, MTXNAMELEN);
315 			kp->ki_mtxname[MTXNAMELEN] = 0;
316 		}
317 		bintime2timeval(&proc.p_runtime, &tv);
318 		kp->ki_runtime = (u_int64_t)tv.tv_sec * 1000000 + tv.tv_usec;
319 		kp->ki_pid = proc.p_pid;
320 		kp->ki_siglist = proc.p_siglist;
321 		kp->ki_sigmask = proc.p_sigmask;
322 		kp->ki_xstat = proc.p_xstat;
323 		kp->ki_acflag = proc.p_acflag;
324 		kp->ki_pctcpu = proc.p_kse.ke_pctcpu;		/* XXXKSE */
325 		kp->ki_estcpu = proc.p_ksegrp.kg_estcpu;	/* XXXKSE */
326 		kp->ki_slptime = proc.p_kse.ke_slptime;		/* XXXKSE */
327 		kp->ki_swtime = proc.p_swtime;
328 		kp->ki_flag = proc.p_flag;
329 		kp->ki_sflag = proc.p_sflag;
330 		kp->ki_wchan = mainthread.td_wchan;		/* XXXKSE */
331 		kp->ki_traceflag = proc.p_traceflag;
332 		kp->ki_stat = proc.p_stat;
333 		kp->ki_pri.pri_class = proc.p_ksegrp.kg_pri_class; /* XXXKSE */
334 		kp->ki_pri.pri_user = proc.p_ksegrp.kg_user_pri; /* XXXKSE */
335 		kp->ki_pri.pri_level = mainthread.td_priority;	/* XXXKSE */
336 		kp->ki_pri.pri_native = mainthread.td_base_pri; /* XXXKSE */
337 		kp->ki_nice = proc.p_ksegrp.kg_nice;		/* XXXKSE */
338 		kp->ki_lock = proc.p_lock;
339 		kp->ki_rqindex = proc.p_kse.ke_rqindex;		/* XXXKSE */
340 		kp->ki_oncpu = proc.p_kse.ke_oncpu;		/* XXXKSE */
341 		kp->ki_lastcpu = mainthread.td_lastcpu;	/* XXXKSE */
342 		bcopy(&kinfo_proc, bp, sizeof(kinfo_proc));
343 		++bp;
344 		++cnt;
345 	}
346 	return (cnt);
347 }
348 
349 /*
350  * Build proc info array by reading in proc list from a crash dump.
351  * Return number of procs read.  maxcnt is the max we will read.
352  */
353 static int
354 kvm_deadprocs(kd, what, arg, a_allproc, a_zombproc, maxcnt)
355 	kvm_t *kd;
356 	int what, arg;
357 	u_long a_allproc;
358 	u_long a_zombproc;
359 	int maxcnt;
360 {
361 	struct kinfo_proc *bp = kd->procbase;
362 	int acnt, zcnt;
363 	struct proc *p;
364 
365 	if (KREAD(kd, a_allproc, &p)) {
366 		_kvm_err(kd, kd->program, "cannot read allproc");
367 		return (-1);
368 	}
369 	acnt = kvm_proclist(kd, what, arg, p, bp, maxcnt);
370 	if (acnt < 0)
371 		return (acnt);
372 
373 	if (KREAD(kd, a_zombproc, &p)) {
374 		_kvm_err(kd, kd->program, "cannot read zombproc");
375 		return (-1);
376 	}
377 	zcnt = kvm_proclist(kd, what, arg, p, bp + acnt, maxcnt - acnt);
378 	if (zcnt < 0)
379 		zcnt = 0;
380 
381 	return (acnt + zcnt);
382 }
383 
384 struct kinfo_proc *
385 kvm_getprocs(kd, op, arg, cnt)
386 	kvm_t *kd;
387 	int op, arg;
388 	int *cnt;
389 {
390 	int mib[4], st, nprocs;
391 	size_t size;
392 
393 	if (kd->procbase != 0) {
394 		free((void *)kd->procbase);
395 		/*
396 		 * Clear this pointer in case this call fails.  Otherwise,
397 		 * kvm_close() will free it again.
398 		 */
399 		kd->procbase = 0;
400 	}
401 	if (ISALIVE(kd)) {
402 		size = 0;
403 		mib[0] = CTL_KERN;
404 		mib[1] = KERN_PROC;
405 		mib[2] = op;
406 		mib[3] = arg;
407 		st = sysctl(mib, op == KERN_PROC_ALL ? 3 : 4, NULL, &size, NULL, 0);
408 		if (st == -1) {
409 			_kvm_syserr(kd, kd->program, "kvm_getprocs");
410 			return (0);
411 		}
412 		do {
413 			size += size / 10;
414 			kd->procbase = (struct kinfo_proc *)
415 			    _kvm_realloc(kd, kd->procbase, size);
416 			if (kd->procbase == 0)
417 				return (0);
418 			st = sysctl(mib, op == KERN_PROC_ALL ? 3 : 4,
419 			    kd->procbase, &size, NULL, 0);
420 		} while (st == -1 && errno == ENOMEM);
421 		if (st == -1) {
422 			_kvm_syserr(kd, kd->program, "kvm_getprocs");
423 			return (0);
424 		}
425 		if (size > 0 &&
426 		    kd->procbase->ki_structsize != sizeof(struct kinfo_proc)) {
427 			_kvm_err(kd, kd->program,
428 			    "kinfo_proc size mismatch (expected %d, got %d)",
429 			    sizeof(struct kinfo_proc),
430 			    kd->procbase->ki_structsize);
431 			return (0);
432 		}
433 		nprocs = size == 0 ? 0 : size / kd->procbase->ki_structsize;
434 	} else {
435 		struct nlist nl[4], *p;
436 
437 		nl[0].n_name = "_nprocs";
438 		nl[1].n_name = "_allproc";
439 		nl[2].n_name = "_zombproc";
440 		nl[3].n_name = 0;
441 
442 		if (kvm_nlist(kd, nl) != 0) {
443 			for (p = nl; p->n_type != 0; ++p)
444 				;
445 			_kvm_err(kd, kd->program,
446 				 "%s: no such symbol", p->n_name);
447 			return (0);
448 		}
449 		if (KREAD(kd, nl[0].n_value, &nprocs)) {
450 			_kvm_err(kd, kd->program, "can't read nprocs");
451 			return (0);
452 		}
453 		size = nprocs * sizeof(struct kinfo_proc);
454 		kd->procbase = (struct kinfo_proc *)_kvm_malloc(kd, size);
455 		if (kd->procbase == 0)
456 			return (0);
457 
458 		nprocs = kvm_deadprocs(kd, op, arg, nl[1].n_value,
459 				      nl[2].n_value, nprocs);
460 #ifdef notdef
461 		size = nprocs * sizeof(struct kinfo_proc);
462 		(void)realloc(kd->procbase, size);
463 #endif
464 	}
465 	*cnt = nprocs;
466 	return (kd->procbase);
467 }
468 
469 void
470 _kvm_freeprocs(kd)
471 	kvm_t *kd;
472 {
473 	if (kd->procbase) {
474 		free(kd->procbase);
475 		kd->procbase = 0;
476 	}
477 }
478 
479 void *
480 _kvm_realloc(kd, p, n)
481 	kvm_t *kd;
482 	void *p;
483 	size_t n;
484 {
485 	void *np = (void *)realloc(p, n);
486 
487 	if (np == 0) {
488 		free(p);
489 		_kvm_err(kd, kd->program, "out of memory");
490 	}
491 	return (np);
492 }
493 
494 #ifndef MAX
495 #define MAX(a, b) ((a) > (b) ? (a) : (b))
496 #endif
497 
498 /*
499  * Read in an argument vector from the user address space of process kp.
500  * addr if the user-space base address of narg null-terminated contiguous
501  * strings.  This is used to read in both the command arguments and
502  * environment strings.  Read at most maxcnt characters of strings.
503  */
504 static char **
505 kvm_argv(kd, kp, addr, narg, maxcnt)
506 	kvm_t *kd;
507 	struct kinfo_proc *kp;
508 	u_long addr;
509 	int narg;
510 	int maxcnt;
511 {
512 	char *np, *cp, *ep, *ap;
513 	u_long oaddr = -1;
514 	int len, cc;
515 	char **argv;
516 
517 	/*
518 	 * Check that there aren't an unreasonable number of agruments,
519 	 * and that the address is in user space.
520 	 */
521 	if (narg > 512 || addr < VM_MIN_ADDRESS || addr >= VM_MAXUSER_ADDRESS)
522 		return (0);
523 
524 	/*
525 	 * kd->argv : work space for fetching the strings from the target
526 	 *            process's space, and is converted for returning to caller
527 	 */
528 	if (kd->argv == 0) {
529 		/*
530 		 * Try to avoid reallocs.
531 		 */
532 		kd->argc = MAX(narg + 1, 32);
533 		kd->argv = (char **)_kvm_malloc(kd, kd->argc *
534 						sizeof(*kd->argv));
535 		if (kd->argv == 0)
536 			return (0);
537 	} else if (narg + 1 > kd->argc) {
538 		kd->argc = MAX(2 * kd->argc, narg + 1);
539 		kd->argv = (char **)_kvm_realloc(kd, kd->argv, kd->argc *
540 						sizeof(*kd->argv));
541 		if (kd->argv == 0)
542 			return (0);
543 	}
544 	/*
545 	 * kd->argspc : returned to user, this is where the kd->argv
546 	 *              arrays are left pointing to the collected strings.
547 	 */
548 	if (kd->argspc == 0) {
549 		kd->argspc = (char *)_kvm_malloc(kd, PAGE_SIZE);
550 		if (kd->argspc == 0)
551 			return (0);
552 		kd->arglen = PAGE_SIZE;
553 	}
554 	/*
555 	 * kd->argbuf : used to pull in pages from the target process.
556 	 *              the strings are copied out of here.
557 	 */
558 	if (kd->argbuf == 0) {
559 		kd->argbuf = (char *)_kvm_malloc(kd, PAGE_SIZE);
560 		if (kd->argbuf == 0)
561 			return (0);
562 	}
563 
564 	/* Pull in the target process'es argv vector */
565 	cc = sizeof(char *) * narg;
566 	if (kvm_uread(kd, kp, addr, (char *)kd->argv, cc) != cc)
567 		return (0);
568 	/*
569 	 * ap : saved start address of string we're working on in kd->argspc
570 	 * np : pointer to next place to write in kd->argspc
571 	 * len: length of data in kd->argspc
572 	 * argv: pointer to the argv vector that we are hunting around the
573 	 *       target process space for, and converting to addresses in
574 	 *       our address space (kd->argspc).
575 	 */
576 	ap = np = kd->argspc;
577 	argv = kd->argv;
578 	len = 0;
579 	/*
580 	 * Loop over pages, filling in the argument vector.
581 	 * Note that the argv strings could be pointing *anywhere* in
582 	 * the user address space and are no longer contiguous.
583 	 * Note that *argv is modified when we are going to fetch a string
584 	 * that crosses a page boundary.  We copy the next part of the string
585 	 * into to "np" and eventually convert the pointer.
586 	 */
587 	while (argv < kd->argv + narg && *argv != 0) {
588 
589 		/* get the address that the current argv string is on */
590 		addr = (u_long)*argv & ~(PAGE_SIZE - 1);
591 
592 		/* is it the same page as the last one? */
593 		if (addr != oaddr) {
594 			if (kvm_uread(kd, kp, addr, kd->argbuf, PAGE_SIZE) !=
595 			    PAGE_SIZE)
596 				return (0);
597 			oaddr = addr;
598 		}
599 
600 		/* offset within the page... kd->argbuf */
601 		addr = (u_long)*argv & (PAGE_SIZE - 1);
602 
603 		/* cp = start of string, cc = count of chars in this chunk */
604 		cp = kd->argbuf + addr;
605 		cc = PAGE_SIZE - addr;
606 
607 		/* dont get more than asked for by user process */
608 		if (maxcnt > 0 && cc > maxcnt - len)
609 			cc = maxcnt - len;
610 
611 		/* pointer to end of string if we found it in this page */
612 		ep = memchr(cp, '\0', cc);
613 		if (ep != 0)
614 			cc = ep - cp + 1;
615 		/*
616 		 * at this point, cc is the count of the chars that we are
617 		 * going to retrieve this time. we may or may not have found
618 		 * the end of it.  (ep points to the null if the end is known)
619 		 */
620 
621 		/* will we exceed the malloc/realloced buffer? */
622 		if (len + cc > kd->arglen) {
623 			int off;
624 			char **pp;
625 			char *op = kd->argspc;
626 
627 			kd->arglen *= 2;
628 			kd->argspc = (char *)_kvm_realloc(kd, kd->argspc,
629 							  kd->arglen);
630 			if (kd->argspc == 0)
631 				return (0);
632 			/*
633 			 * Adjust argv pointers in case realloc moved
634 			 * the string space.
635 			 */
636 			off = kd->argspc - op;
637 			for (pp = kd->argv; pp < argv; pp++)
638 				*pp += off;
639 			ap += off;
640 			np += off;
641 		}
642 		/* np = where to put the next part of the string in kd->argspc*/
643 		/* np is kinda redundant.. could use "kd->argspc + len" */
644 		memcpy(np, cp, cc);
645 		np += cc;	/* inc counters */
646 		len += cc;
647 
648 		/*
649 		 * if end of string found, set the *argv pointer to the
650 		 * saved beginning of string, and advance. argv points to
651 		 * somewhere in kd->argv..  This is initially relative
652 		 * to the target process, but when we close it off, we set
653 		 * it to point in our address space.
654 		 */
655 		if (ep != 0) {
656 			*argv++ = ap;
657 			ap = np;
658 		} else {
659 			/* update the address relative to the target process */
660 			*argv += cc;
661 		}
662 
663 		if (maxcnt > 0 && len >= maxcnt) {
664 			/*
665 			 * We're stopping prematurely.  Terminate the
666 			 * current string.
667 			 */
668 			if (ep == 0) {
669 				*np = '\0';
670 				*argv++ = ap;
671 			}
672 			break;
673 		}
674 	}
675 	/* Make sure argv is terminated. */
676 	*argv = 0;
677 	return (kd->argv);
678 }
679 
680 static void
681 ps_str_a(p, addr, n)
682 	struct ps_strings *p;
683 	u_long *addr;
684 	int *n;
685 {
686 	*addr = (u_long)p->ps_argvstr;
687 	*n = p->ps_nargvstr;
688 }
689 
690 static void
691 ps_str_e(p, addr, n)
692 	struct ps_strings *p;
693 	u_long *addr;
694 	int *n;
695 {
696 	*addr = (u_long)p->ps_envstr;
697 	*n = p->ps_nenvstr;
698 }
699 
700 /*
701  * Determine if the proc indicated by p is still active.
702  * This test is not 100% foolproof in theory, but chances of
703  * being wrong are very low.
704  */
705 static int
706 proc_verify(curkp)
707 	struct kinfo_proc *curkp;
708 {
709 	struct kinfo_proc newkp;
710 	int mib[4];
711 	size_t len;
712 
713 	mib[0] = CTL_KERN;
714 	mib[1] = KERN_PROC;
715 	mib[2] = KERN_PROC_PID;
716 	mib[3] = curkp->ki_pid;
717 	len = sizeof(newkp);
718 	if (sysctl(mib, 4, &newkp, &len, NULL, 0) == -1)
719 		return (0);
720 	return (curkp->ki_pid == newkp.ki_pid &&
721 	    (newkp.ki_stat != SZOMB || curkp->ki_stat == SZOMB));
722 }
723 
724 static char **
725 kvm_doargv(kd, kp, nchr, info)
726 	kvm_t *kd;
727 	struct kinfo_proc *kp;
728 	int nchr;
729 	void (*info)(struct ps_strings *, u_long *, int *);
730 {
731 	char **ap;
732 	u_long addr;
733 	int cnt;
734 	static struct ps_strings arginfo;
735 	static u_long ps_strings;
736 	size_t len;
737 
738 	if (ps_strings == NULL) {
739 		len = sizeof(ps_strings);
740 		if (sysctlbyname("kern.ps_strings", &ps_strings, &len, NULL,
741 		    0) == -1)
742 			ps_strings = PS_STRINGS;
743 	}
744 
745 	/*
746 	 * Pointers are stored at the top of the user stack.
747 	 */
748 	if (kp->ki_stat == SZOMB ||
749 	    kvm_uread(kd, kp, ps_strings, (char *)&arginfo,
750 		      sizeof(arginfo)) != sizeof(arginfo))
751 		return (0);
752 
753 	(*info)(&arginfo, &addr, &cnt);
754 	if (cnt == 0)
755 		return (0);
756 	ap = kvm_argv(kd, kp, addr, cnt, nchr);
757 	/*
758 	 * For live kernels, make sure this process didn't go away.
759 	 */
760 	if (ap != 0 && ISALIVE(kd) && !proc_verify(kp))
761 		ap = 0;
762 	return (ap);
763 }
764 
765 /*
766  * Get the command args.  This code is now machine independent.
767  */
768 char **
769 kvm_getargv(kd, kp, nchr)
770 	kvm_t *kd;
771 	const struct kinfo_proc *kp;
772 	int nchr;
773 {
774 	int oid[4];
775 	int i;
776 	size_t bufsz;
777 	static unsigned long buflen;
778 	static char *buf, *p;
779 	static char **bufp;
780 	static int argc;
781 
782 	if (!ISALIVE(kd)) {
783 		_kvm_err(kd, kd->program,
784 		    "cannot read user space from dead kernel");
785 		return (0);
786 	}
787 
788 	if (!buflen) {
789 		bufsz = sizeof(buflen);
790 		i = sysctlbyname("kern.ps_arg_cache_limit",
791 		    &buflen, &bufsz, NULL, 0);
792 		if (i == -1) {
793 			buflen = 0;
794 		} else {
795 			buf = malloc(buflen);
796 			if (buf == NULL)
797 				buflen = 0;
798 			argc = 32;
799 			bufp = malloc(sizeof(char *) * argc);
800 		}
801 	}
802 	if (buf != NULL) {
803 		oid[0] = CTL_KERN;
804 		oid[1] = KERN_PROC;
805 		oid[2] = KERN_PROC_ARGS;
806 		oid[3] = kp->ki_pid;
807 		bufsz = buflen;
808 		i = sysctl(oid, 4, buf, &bufsz, 0, 0);
809 		if (i == 0 && bufsz > 0) {
810 			i = 0;
811 			p = buf;
812 			do {
813 				bufp[i++] = p;
814 				p += strlen(p) + 1;
815 				if (i >= argc) {
816 					argc += argc;
817 					bufp = realloc(bufp,
818 					    sizeof(char *) * argc);
819 				}
820 			} while (p < buf + bufsz);
821 			bufp[i++] = 0;
822 			return (bufp);
823 		}
824 	}
825 	if (kp->ki_flag & P_SYSTEM)
826 		return (NULL);
827 	return (kvm_doargv(kd, kp, nchr, ps_str_a));
828 }
829 
830 char **
831 kvm_getenvv(kd, kp, nchr)
832 	kvm_t *kd;
833 	const struct kinfo_proc *kp;
834 	int nchr;
835 {
836 	return (kvm_doargv(kd, kp, nchr, ps_str_e));
837 }
838 
839 /*
840  * Read from user space.  The user context is given by p.
841  */
842 ssize_t
843 kvm_uread(kd, kp, uva, buf, len)
844 	kvm_t *kd;
845 	struct kinfo_proc *kp;
846 	u_long uva;
847 	char *buf;
848 	size_t len;
849 {
850 	char *cp;
851 	char procfile[MAXPATHLEN];
852 	ssize_t amount;
853 	int fd;
854 
855 	if (!ISALIVE(kd)) {
856 		_kvm_err(kd, kd->program,
857 		    "cannot read user space from dead kernel");
858 		return (0);
859 	}
860 
861 	sprintf(procfile, "/proc/%d/mem", kp->ki_pid);
862 	fd = open(procfile, O_RDONLY, 0);
863 	if (fd < 0) {
864 		_kvm_err(kd, kd->program, "cannot open %s", procfile);
865 		close(fd);
866 		return (0);
867 	}
868 
869 	cp = buf;
870 	while (len > 0) {
871 		errno = 0;
872 		if (lseek(fd, (off_t)uva, 0) == -1 && errno != 0) {
873 			_kvm_err(kd, kd->program, "invalid address (%x) in %s",
874 			    uva, procfile);
875 			break;
876 		}
877 		amount = read(fd, cp, len);
878 		if (amount < 0) {
879 			_kvm_syserr(kd, kd->program, "error reading %s",
880 			    procfile);
881 			break;
882 		}
883 		if (amount == 0) {
884 			_kvm_err(kd, kd->program, "EOF reading %s", procfile);
885 			break;
886 		}
887 		cp += amount;
888 		uva += amount;
889 		len -= amount;
890 	}
891 
892 	close(fd);
893 	return ((ssize_t)(cp - buf));
894 }
895