FreeBSD/Linux Kernel Cross Reference
sys/kern/kern_acct.c
1 /*-
2 * Copyright (c) 1982, 1986, 1989, 1993
3 * The Regents of the University of California. All rights reserved.
4 * (c) UNIX System Laboratories, Inc.
5 * All or some portions of this file are derived from material licensed
6 * to the University of California by American Telephone and Telegraph
7 * Co. or Unix System Laboratories, Inc. and are reproduced herein with
8 * the permission of UNIX System Laboratories, Inc.
9 *
10 * Copyright (c) 1994 Christopher G. Demetriou
11 * Copyright (c) 2005 Robert N. M. Watson
12 *
13 * Redistribution and use in source and binary forms, with or without
14 * modification, are permitted provided that the following conditions
15 * are met:
16 * 1. Redistributions of source code must retain the above copyright
17 * notice, this list of conditions and the following disclaimer.
18 * 2. Redistributions in binary form must reproduce the above copyright
19 * notice, this list of conditions and the following disclaimer in the
20 * documentation and/or other materials provided with the distribution.
21 * 3. All advertising materials mentioning features or use of this software
22 * must display the following acknowledgement:
23 * This product includes software developed by the University of
24 * California, Berkeley and its contributors.
25 * 4. Neither the name of the University nor the names of its contributors
26 * may be used to endorse or promote products derived from this software
27 * without specific prior written permission.
28 *
29 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
30 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
31 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
32 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
33 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
34 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
35 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
36 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
37 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
38 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
39 * SUCH DAMAGE.
40 *
41 * @(#)kern_acct.c 8.1 (Berkeley) 6/14/93
42 */
43
44 #include <sys/cdefs.h>
45 __FBSDID("$FreeBSD$");
46
47 #include "opt_mac.h"
48
49 #include <sys/param.h>
50 #include <sys/systm.h>
51 #include <sys/acct.h>
52 #include <sys/fcntl.h>
53 #include <sys/kernel.h>
54 #include <sys/kthread.h>
55 #include <sys/lock.h>
56 #include <sys/mac.h>
57 #include <sys/mount.h>
58 #include <sys/mutex.h>
59 #include <sys/namei.h>
60 #include <sys/proc.h>
61 #include <sys/resourcevar.h>
62 #include <sys/sched.h>
63 #include <sys/sx.h>
64 #include <sys/sysctl.h>
65 #include <sys/sysent.h>
66 #include <sys/syslog.h>
67 #include <sys/sysproto.h>
68 #include <sys/tty.h>
69 #include <sys/vnode.h>
70
71 /*
72 * The routines implemented in this file are described in:
73 * Leffler, et al.: The Design and Implementation of the 4.3BSD
74 * UNIX Operating System (Addison Welley, 1989)
75 * on pages 62-63.
76 *
77 * Arguably, to simplify accounting operations, this mechanism should
78 * be replaced by one in which an accounting log file (similar to /dev/klog)
79 * is read by a user process, etc. However, that has its own problems.
80 */
81
82 /*
83 * Internal accounting functions.
84 * The former's operation is described in Leffler, et al., and the latter
85 * was provided by UCB with the 4.4BSD-Lite release
86 */
87 static comp_t encode_comp_t(u_long, u_long);
88 static void acctwatch(void);
89 static void acct_thread(void *);
90 static int acct_disable(struct thread *);
91
92 /*
93 * Accounting vnode pointer, saved vnode pointer, and flags for each.
94 * acct_sx protects against changes to the active vnode and credentials
95 * while accounting records are being committed to disk.
96 */
97 static int acct_suspended;
98 static struct vnode *acct_vp;
99 static struct ucred *acct_cred;
100 static int acct_flags;
101 static struct sx acct_sx;
102
103 SX_SYSINIT(acct, &acct_sx, "acct_sx");
104
105 /*
106 * State of the accounting kthread.
107 */
108 static int acct_state;
109
110 #define ACCT_RUNNING 1 /* Accounting kthread is running. */
111 #define ACCT_EXITREQ 2 /* Accounting kthread should exit. */
112
113 /*
114 * Values associated with enabling and disabling accounting
115 */
116 static int acctsuspend = 2; /* stop accounting when < 2% free space left */
117 SYSCTL_INT(_kern, OID_AUTO, acct_suspend, CTLFLAG_RW,
118 &acctsuspend, 0, "percentage of free disk space below which accounting stops");
119
120 static int acctresume = 4; /* resume when free space risen to > 4% */
121 SYSCTL_INT(_kern, OID_AUTO, acct_resume, CTLFLAG_RW,
122 &acctresume, 0, "percentage of free disk space above which accounting resumes");
123
124 static int acctchkfreq = 15; /* frequency (in seconds) to check space */
125
126 static int
127 sysctl_acct_chkfreq(SYSCTL_HANDLER_ARGS)
128 {
129 int error, value;
130
131 /* Write out the old value. */
132 error = SYSCTL_OUT(req, &acctchkfreq, sizeof(int));
133 if (error || req->newptr == NULL)
134 return (error);
135
136 /* Read in and verify the new value. */
137 error = SYSCTL_IN(req, &value, sizeof(int));
138 if (error)
139 return (error);
140 if (value <= 0)
141 return (EINVAL);
142 acctchkfreq = value;
143 return (0);
144 }
145 SYSCTL_PROC(_kern, OID_AUTO, acct_chkfreq, CTLTYPE_INT|CTLFLAG_RW,
146 &acctchkfreq, 0, sysctl_acct_chkfreq, "I",
147 "frequency for checking the free space");
148
149 SYSCTL_INT(_kern, OID_AUTO, acct_suspended, CTLFLAG_RD, &acct_suspended, 0,
150 "Accounting suspended or not");
151
152 /*
153 * Accounting system call. Written based on the specification and
154 * previous implementation done by Mark Tinguely.
155 *
156 * MPSAFE
157 */
158 int
159 acct(struct thread *td, struct acct_args *uap)
160 {
161 struct nameidata nd;
162 int error, flags;
163
164 /* Make sure that the caller is root. */
165 error = suser(td);
166 if (error)
167 return (error);
168
169 /*
170 * If accounting is to be started to a file, open that file for
171 * appending and make sure it's a 'normal'. While we could
172 * conditionally acquire Giant here, we're actually interacting with
173 * vnodes from possibly two file systems, making the logic a bit
174 * complicated. For now, use Giant unconditionally.
175 */
176 mtx_lock(&Giant);
177 if (uap->path != NULL) {
178 NDINIT(&nd, LOOKUP, NOFOLLOW | AUDITVNODE1, UIO_USERSPACE,
179 uap->path, td);
180 flags = FWRITE | O_APPEND;
181 error = vn_open(&nd, &flags, 0, -1);
182 if (error)
183 goto done;
184 NDFREE(&nd, NDF_ONLY_PNBUF);
185 #ifdef MAC
186 error = mac_check_system_acct(td->td_ucred, nd.ni_vp);
187 if (error) {
188 VOP_UNLOCK(nd.ni_vp, 0, td);
189 vn_close(nd.ni_vp, flags, td->td_ucred, td);
190 goto done;
191 }
192 #endif
193 VOP_UNLOCK(nd.ni_vp, 0, td);
194 if (nd.ni_vp->v_type != VREG) {
195 vn_close(nd.ni_vp, flags, td->td_ucred, td);
196 error = EACCES;
197 goto done;
198 }
199 #ifdef MAC
200 } else {
201 error = mac_check_system_acct(td->td_ucred, NULL);
202 if (error)
203 goto done;
204 #endif
205 }
206
207 /*
208 * Disallow concurrent access to the accounting vnode while we swap
209 * it out, in order to prevent access after close.
210 */
211 sx_xlock(&acct_sx);
212
213 /*
214 * If accounting was previously enabled, kill the old space-watcher,
215 * close the file, and (if no new file was specified, leave). Reset
216 * the suspended state regardless of whether accounting remains
217 * enabled.
218 */
219 acct_suspended = 0;
220 if (acct_vp != NULL)
221 error = acct_disable(td);
222 if (uap->path == NULL) {
223 if (acct_state & ACCT_RUNNING) {
224 acct_state |= ACCT_EXITREQ;
225 wakeup(&acct_state);
226 }
227 sx_xunlock(&acct_sx);
228 goto done;
229 }
230
231 /*
232 * Save the new accounting file vnode, and schedule the new
233 * free space watcher.
234 */
235 acct_vp = nd.ni_vp;
236 acct_cred = crhold(td->td_ucred);
237 acct_flags = flags;
238 if (acct_state & ACCT_RUNNING)
239 acct_state &= ~ACCT_EXITREQ;
240 else {
241 /*
242 * Try to start up an accounting kthread. We may start more
243 * than one, but if so the extras will commit suicide as
244 * soon as they start up.
245 */
246 error = kthread_create(acct_thread, NULL, NULL, 0, 0,
247 "accounting");
248 if (error) {
249 (void) vn_close(acct_vp, acct_flags, acct_cred, td);
250 crfree(acct_cred);
251 acct_vp = NULL;
252 acct_cred = NULL;
253 acct_flags = 0;
254 sx_xunlock(&acct_sx);
255 log(LOG_NOTICE, "Unable to start accounting thread\n");
256 goto done;
257 }
258 }
259 sx_xunlock(&acct_sx);
260 log(LOG_NOTICE, "Accounting enabled\n");
261 done:
262 mtx_unlock(&Giant);
263 return (error);
264 }
265
266 /*
267 * Disable currently in-progress accounting by closing the vnode, dropping
268 * our reference to the credential, and clearing the vnode's flags.
269 */
270 static int
271 acct_disable(struct thread *td)
272 {
273 int error;
274
275 sx_assert(&acct_sx, SX_XLOCKED);
276 error = vn_close(acct_vp, acct_flags, acct_cred, td);
277 crfree(acct_cred);
278 acct_vp = NULL;
279 acct_cred = NULL;
280 acct_flags = 0;
281 log(LOG_NOTICE, "Accounting disabled\n");
282 return (error);
283 }
284
285 /*
286 * Write out process accounting information, on process exit.
287 * Data to be written out is specified in Leffler, et al.
288 * and are enumerated below. (They're also noted in the system
289 * "acct.h" header file.)
290 */
291 int
292 acct_process(struct thread *td)
293 {
294 struct acct acct;
295 struct timeval ut, st, tmp;
296 struct plimit *newlim, *oldlim;
297 struct proc *p;
298 struct rusage *r;
299 int t, ret, vfslocked;
300
301 /*
302 * Lockless check of accounting condition before doing the hard
303 * work.
304 */
305 if (acct_vp == NULL || acct_suspended)
306 return (0);
307
308 sx_slock(&acct_sx);
309
310 /*
311 * If accounting isn't enabled, don't bother. Have to check again
312 * once we own the lock in case we raced with disabling of accounting
313 * by another thread.
314 */
315 if (acct_vp == NULL || acct_suspended) {
316 sx_sunlock(&acct_sx);
317 return (0);
318 }
319
320 p = td->td_proc;
321
322 /*
323 * Get process accounting information.
324 */
325
326 PROC_LOCK(p);
327 /* (1) The name of the command that ran */
328 bcopy(p->p_comm, acct.ac_comm, sizeof acct.ac_comm);
329
330 /* (2) The amount of user and system time that was used */
331 calcru(p, &ut, &st);
332 acct.ac_utime = encode_comp_t(ut.tv_sec, ut.tv_usec);
333 acct.ac_stime = encode_comp_t(st.tv_sec, st.tv_usec);
334
335 /* (3) The elapsed time the command ran (and its starting time) */
336 tmp = boottime;
337 timevaladd(&tmp, &p->p_stats->p_start);
338 acct.ac_btime = tmp.tv_sec;
339 microuptime(&tmp);
340 timevalsub(&tmp, &p->p_stats->p_start);
341 acct.ac_etime = encode_comp_t(tmp.tv_sec, tmp.tv_usec);
342
343 /* (4) The average amount of memory used */
344 r = &p->p_stats->p_ru;
345 tmp = ut;
346 timevaladd(&tmp, &st);
347 t = tmp.tv_sec * hz + tmp.tv_usec / tick;
348 if (t)
349 acct.ac_mem = (r->ru_ixrss + r->ru_idrss + r->ru_isrss) / t;
350 else
351 acct.ac_mem = 0;
352
353 /* (5) The number of disk I/O operations done */
354 acct.ac_io = encode_comp_t(r->ru_inblock + r->ru_oublock, 0);
355
356 /* (6) The UID and GID of the process */
357 acct.ac_uid = p->p_ucred->cr_ruid;
358 acct.ac_gid = p->p_ucred->cr_rgid;
359
360 /* (7) The terminal from which the process was started */
361 SESS_LOCK(p->p_session);
362 if ((p->p_flag & P_CONTROLT) && p->p_pgrp->pg_session->s_ttyp)
363 acct.ac_tty = dev2udev(p->p_pgrp->pg_session->s_ttyp->t_dev);
364 else
365 acct.ac_tty = NODEV;
366 SESS_UNLOCK(p->p_session);
367
368 /* (8) The boolean flags that tell how the process terminated, etc. */
369 acct.ac_flag = p->p_acflag;
370 PROC_UNLOCK(p);
371
372 /*
373 * Eliminate any file size rlimit.
374 */
375 newlim = lim_alloc();
376 PROC_LOCK(p);
377 oldlim = p->p_limit;
378 lim_copy(newlim, oldlim);
379 newlim->pl_rlimit[RLIMIT_FSIZE].rlim_cur = RLIM_INFINITY;
380 p->p_limit = newlim;
381 PROC_UNLOCK(p);
382 lim_free(oldlim);
383
384 /*
385 * Write the accounting information to the file.
386 */
387 vfslocked = VFS_LOCK_GIANT(acct_vp->v_mount);
388 VOP_LEASE(acct_vp, td, acct_cred, LEASE_WRITE);
389 ret = vn_rdwr(UIO_WRITE, acct_vp, (caddr_t)&acct, sizeof (acct),
390 (off_t)0, UIO_SYSSPACE, IO_APPEND|IO_UNIT, acct_cred, NOCRED,
391 (int *)0, td);
392 VFS_UNLOCK_GIANT(vfslocked);
393 sx_sunlock(&acct_sx);
394 return (ret);
395 }
396
397 /*
398 * Encode_comp_t converts from ticks in seconds and microseconds
399 * to ticks in 1/AHZ seconds. The encoding is described in
400 * Leffler, et al., on page 63.
401 */
402
403 #define MANTSIZE 13 /* 13 bit mantissa. */
404 #define EXPSIZE 3 /* Base 8 (3 bit) exponent. */
405 #define MAXFRACT ((1 << MANTSIZE) - 1) /* Maximum fractional value. */
406
407 static comp_t
408 encode_comp_t(u_long s, u_long us)
409 {
410 int exp, rnd;
411
412 exp = 0;
413 rnd = 0;
414 s *= AHZ;
415 s += us / (1000000 / AHZ); /* Maximize precision. */
416
417 while (s > MAXFRACT) {
418 rnd = s & (1 << (EXPSIZE - 1)); /* Round up? */
419 s >>= EXPSIZE; /* Base 8 exponent == 3 bit shift. */
420 exp++;
421 }
422
423 /* If we need to round up, do it (and handle overflow correctly). */
424 if (rnd && (++s > MAXFRACT)) {
425 s >>= EXPSIZE;
426 exp++;
427 }
428
429 /* Clean it up and polish it off. */
430 exp <<= MANTSIZE; /* Shift the exponent into place */
431 exp += s; /* and add on the mantissa. */
432 return (exp);
433 }
434
435 /*
436 * Periodically check the filesystem to see if accounting
437 * should be turned on or off. Beware the case where the vnode
438 * has been vgone()'d out from underneath us, e.g. when the file
439 * system containing the accounting file has been forcibly unmounted.
440 */
441 /* ARGSUSED */
442 static void
443 acctwatch(void)
444 {
445 struct statfs sb;
446 int vfslocked;
447
448 sx_assert(&acct_sx, SX_XLOCKED);
449
450 /*
451 * If accounting was disabled before our kthread was scheduled,
452 * then acct_vp might be NULL. If so, just ask our kthread to
453 * exit and return.
454 */
455 if (acct_vp == NULL) {
456 acct_state |= ACCT_EXITREQ;
457 return;
458 }
459
460 /*
461 * If our vnode is no longer valid, tear it down and signal the
462 * accounting thread to die.
463 */
464 vfslocked = VFS_LOCK_GIANT(acct_vp->v_mount);
465 if (acct_vp->v_type == VBAD) {
466 (void) acct_disable(NULL);
467 VFS_UNLOCK_GIANT(vfslocked);
468 acct_state |= ACCT_EXITREQ;
469 return;
470 }
471
472 /*
473 * Stopping here is better than continuing, maybe it will be VBAD
474 * next time around.
475 */
476 if (VFS_STATFS(acct_vp->v_mount, &sb, curthread) < 0) {
477 VFS_UNLOCK_GIANT(vfslocked);
478 return;
479 }
480 VFS_UNLOCK_GIANT(vfslocked);
481 if (acct_suspended) {
482 if (sb.f_bavail > (int64_t)(acctresume * sb.f_blocks /
483 100)) {
484 acct_suspended = 0;
485 log(LOG_NOTICE, "Accounting resumed\n");
486 }
487 } else {
488 if (sb.f_bavail <= (int64_t)(acctsuspend * sb.f_blocks /
489 100)) {
490 acct_suspended = 1;
491 log(LOG_NOTICE, "Accounting suspended\n");
492 }
493 }
494 }
495
496 /*
497 * The main loop for the dedicated kernel thread that periodically calls
498 * acctwatch().
499 */
500 static void
501 acct_thread(void *dummy)
502 {
503 u_char pri;
504
505 /* This is a low-priority kernel thread. */
506 pri = PRI_MAX_KERN;
507 mtx_lock_spin(&sched_lock);
508 sched_prio(curthread, pri);
509 mtx_unlock_spin(&sched_lock);
510
511 /* If another accounting kthread is already running, just die. */
512 sx_xlock(&acct_sx);
513 if (acct_state & ACCT_RUNNING) {
514 sx_xunlock(&acct_sx);
515 kthread_exit(0);
516 }
517 acct_state |= ACCT_RUNNING;
518
519 /* Loop until we are asked to exit. */
520 while (!(acct_state & ACCT_EXITREQ)) {
521
522 /* Perform our periodic checks. */
523 acctwatch();
524
525 /*
526 * We check this flag again before sleeping since the
527 * acctwatch() might have shut down accounting and asked us
528 * to exit.
529 */
530 if (!(acct_state & ACCT_EXITREQ)) {
531 sx_xunlock(&acct_sx);
532 tsleep(&acct_state, pri, "-", acctchkfreq * hz);
533 sx_xlock(&acct_sx);
534 }
535 }
536
537 /*
538 * Acknowledge the exit request and shutdown. We clear both the
539 * exit request and running flags.
540 */
541 acct_state = 0;
542 sx_xunlock(&acct_sx);
543 kthread_exit(0);
544 }
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