src/sys/kern/kern_acct.c

/*	$OpenBSD: kern_acct.c,v 1.48 2024/04/13 23:44:11 jsg Exp $	*/
/*	$NetBSD: kern_acct.c,v 1.42 1996/02/04 02:15:12 christos Exp $	*/

/*-
 * Copyright (c) 1994 Christopher G. Demetriou
 * Copyright (c) 1982, 1986, 1989, 1993
 *	The Regents of the University of California.  All rights reserved.
 * (c) UNIX System Laboratories, Inc.
 * All or some portions of this file are derived from material licensed
 * to the University of California by American Telephone and Telegraph
 * Co. or Unix System Laboratories, Inc. and are reproduced herein with
 * the permission of UNIX System Laboratories, Inc.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *	@(#)kern_acct.c	8.1 (Berkeley) 6/14/93
 */

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/proc.h>
#include <sys/mount.h>
#include <sys/vnode.h>
#include <sys/fcntl.h>
#include <sys/syslog.h>
#include <sys/kernel.h>
#include <sys/namei.h>
#include <sys/errno.h>
#include <sys/acct.h>
#include <sys/resourcevar.h>
#include <sys/tty.h>
#include <sys/kthread.h>
#include <sys/rwlock.h>

#include <sys/syscallargs.h>

/*
 * The routines implemented in this file are described in:
 *      Leffler, et al.: The Design and Implementation of the 4.3BSD
 *	    UNIX Operating System (Addison Welley, 1989)
 * on pages 62-63.
 *
 * Arguably, to simplify accounting operations, this mechanism should
 * be replaced by one in which an accounting log file (similar to /dev/klog)
 * is read by a user process, etc.  However, that has its own problems.
 */

/*
 * Internal accounting functions.
 */
comp_t	encode_comp_t(u_long, u_long);
int	acct_start(void);
void	acct_thread(void *);
void	acct_shutdown(void);

/*
 * Accounting vnode pointer, and saved vnode pointer.
 */
struct	vnode *acctp;
struct	vnode *savacctp;

/*
 * Lock protecting acctp and savacctp.
 */
struct	rwlock acct_lock = RWLOCK_INITIALIZER("acctlk");

/*
 * Values associated with enabling and disabling accounting
 */
int	acctsuspend = 2;	/* stop accounting when < 2% free space left */
int	acctresume = 4;		/* resume when free space risen to > 4% */
int	acctrate = 15;		/* delay (in seconds) between space checks */

struct proc *acct_proc;

/*
 * Accounting system call.  Written based on the specification and
 * previous implementation done by Mark Tinguely.
 */
int
sys_acct(struct proc *p, void *v, register_t *retval)
{
	struct sys_acct_args /* {
		syscallarg(const char *) path;
	} */ *uap = v;
	struct nameidata nd;
	int error;

	/* Make sure that the caller is root. */
	if ((error = suser(p)) != 0)
		return (error);

	/*
	 * If accounting is to be started to a file, open that file for
	 * writing and make sure it's 'normal'.
	 */
	if (SCARG(uap, path) != NULL) {
		NDINIT(&nd, 0, 0, UIO_USERSPACE, SCARG(uap, path), p);
		if ((error = vn_open(&nd, FWRITE|O_APPEND, 0)) != 0)
			return (error);
		VOP_UNLOCK(nd.ni_vp);
		if (nd.ni_vp->v_type != VREG) {
			vn_close(nd.ni_vp, FWRITE, p->p_ucred, p);
			return (EACCES);
		}
	}

	rw_enter_write(&acct_lock);

	/*
	 * If accounting was previously enabled, kill the old space-watcher,
	 * close the file, and (if no new file was specified, leave).
	 */
	if (acctp != NULL || savacctp != NULL) {
		wakeup(&acct_proc);
		(void)vn_close((acctp != NULL ? acctp : savacctp), FWRITE,
		    p->p_ucred, p);
		acctp = savacctp = NULL;
	}
	if (SCARG(uap, path) == NULL)
		goto out;

	/*
	 * Save the new accounting file vnode, and schedule the new
	 * free space watcher.
	 */
	acctp = nd.ni_vp;
	if ((error = acct_start()) != 0) {
		acctp = NULL;
		(void)vn_close(nd.ni_vp, FWRITE, p->p_ucred, p);
	}

out:
	rw_exit_write(&acct_lock);
	return (error);
}

/*
 * Write out process accounting information, on process exit.
 * Data to be written out is specified in Leffler, et al.
 * and are enumerated below.  (They're also noted in the system
 * "acct.h" header file.)
 */
int
acct_process(struct proc *p)
{
	struct acct acct;
	struct process *pr = p->p_p;
	struct rusage *r;
	struct timespec booted, elapsed, realstart, st, tmp, uptime, ut;
	int t;
	struct vnode *vp;
	int error = 0;

	/* If accounting isn't enabled, don't bother */
	if (acctp == NULL)
		return (0);

	rw_enter_read(&acct_lock);

	/*
	 * Check the vnode again in case accounting got disabled while waiting
	 * for the lock.
	 */
	vp = acctp;
	if (vp == NULL)
		goto out;

	/*
	 * Get process accounting information.
	 */

	/* (1) The name of the command that ran */
	memcpy(acct.ac_comm, pr->ps_comm, sizeof acct.ac_comm);

	/* (2) The amount of user and system time that was used */
	calctsru(&pr->ps_tu, &ut, &st, NULL);
	acct.ac_utime = encode_comp_t(ut.tv_sec, ut.tv_nsec);
	acct.ac_stime = encode_comp_t(st.tv_sec, st.tv_nsec);

	/* (3) The elapsed time the command ran (and its starting time) */
	nanouptime(&uptime);
	nanoboottime(&booted);
	timespecadd(&booted, &pr->ps_start, &realstart);
	acct.ac_btime = realstart.tv_sec;
	timespecsub(&uptime, &pr->ps_start, &elapsed);
	acct.ac_etime = encode_comp_t(elapsed.tv_sec, elapsed.tv_nsec);

	/* (4) The average amount of memory used */
	r = &p->p_ru;
	timespecadd(&ut, &st, &tmp);
	t = tmp.tv_sec * hz + tmp.tv_nsec / (1000 * tick);
	if (t)
		acct.ac_mem = (r->ru_ixrss + r->ru_idrss + r->ru_isrss) / t;
	else
		acct.ac_mem = 0;

	/* (5) The number of disk I/O operations done */
	acct.ac_io = encode_comp_t(r->ru_inblock + r->ru_oublock, 0);

	/* (6) The UID and GID of the process */
	acct.ac_uid = pr->ps_ucred->cr_ruid;
	acct.ac_gid = pr->ps_ucred->cr_rgid;

	/* (7) The terminal from which the process was started */
	if ((pr->ps_flags & PS_CONTROLT) &&
	    pr->ps_pgrp->pg_session->s_ttyp)
		acct.ac_tty = pr->ps_pgrp->pg_session->s_ttyp->t_dev;
	else
		acct.ac_tty = -1;

	/* (8) The boolean flags that tell how process terminated or misbehaved. */
	acct.ac_flag = pr->ps_acflag;

	/* Extensions */
	acct.ac_pid = pr->ps_pid;

	/*
	 * Now, just write the accounting information to the file.
	 */
	error = vn_rdwr(UIO_WRITE, vp, (caddr_t)&acct, sizeof (acct),
	    (off_t)0, UIO_SYSSPACE, IO_APPEND|IO_UNIT|IO_NOLIMIT,
	    p->p_ucred, NULL, p);

out:
	rw_exit_read(&acct_lock);
	return (error);
}

/*
 * Encode_comp_t converts from ticks in seconds and microseconds
 * to ticks in 1/AHZ seconds.  The encoding is described in
 * Leffler, et al., on page 63.
 */

#define	MANTSIZE	13			/* 13 bit mantissa. */
#define	EXPSIZE		3			/* Base 8 (3 bit) exponent. */
#define	MAXFRACT	((1 << MANTSIZE) - 1)	/* Maximum fractional value. */

comp_t
encode_comp_t(u_long s, u_long ns)
{
	int exp, rnd;

	exp = 0;
	rnd = 0;
	s *= AHZ;
	s += ns / (1000000000 / AHZ);	/* Maximize precision. */

	while (s > MAXFRACT) {
		rnd = s & (1 << (EXPSIZE - 1));	/* Round up? */
		s >>= EXPSIZE;		/* Base 8 exponent == 3 bit shift. */
		exp++;
	}

	/* If we need to round up, do it (and handle overflow correctly). */
	if (rnd && (++s > MAXFRACT)) {
		s >>= EXPSIZE;
		exp++;
	}

	/* Clean it up and polish it off. */
	exp <<= MANTSIZE;		/* Shift the exponent into place */
	exp += s;			/* and add on the mantissa. */
	return (exp);
}

int
acct_start(void)
{
	/* Already running. */
	if (acct_proc != NULL)
		return (0);

	return (kthread_create(acct_thread, NULL, &acct_proc, "acct"));
}

/*
 * Periodically check the file system to see if accounting
 * should be turned on or off.  Beware the case where the vnode
 * has been vgone()'d out from underneath us, e.g. when the file
 * system containing the accounting file has been forcibly unmounted.
 */
void
acct_thread(void *arg)
{
	struct statfs sb;
	struct proc *p = curproc;

	rw_enter_write(&acct_lock);
	for (;;) {
		if (savacctp != NULL) {
			if (savacctp->v_type == VBAD) {
				(void) vn_close(savacctp, FWRITE, NOCRED, p);
				savacctp = NULL;
				break;
			}
			(void)VFS_STATFS(savacctp->v_mount, &sb, NULL);
			if (sb.f_bavail > acctresume * sb.f_blocks / 100) {
				acctp = savacctp;
				savacctp = NULL;
				log(LOG_NOTICE, "Accounting resumed\n");
			}
		} else if (acctp != NULL) {
			if (acctp->v_type == VBAD) {
				(void) vn_close(acctp, FWRITE, NOCRED, p);
				acctp = NULL;
				break;
			}
			(void)VFS_STATFS(acctp->v_mount, &sb, NULL);
			if (sb.f_bavail <= acctsuspend * sb.f_blocks / 100) {
				savacctp = acctp;
				acctp = NULL;
				log(LOG_NOTICE, "Accounting suspended\n");
			}
		} else {
			break;
		}
		rwsleep_nsec(&acct_proc, &acct_lock, PPAUSE, "acct",
		    SEC_TO_NSEC(acctrate));
	}
	acct_proc = NULL;
	rw_exit_write(&acct_lock);
	kthread_exit(0);
}

void
acct_shutdown(void)
{

	struct proc *p = curproc;

	rw_enter_write(&acct_lock);
	if (acctp != NULL || savacctp != NULL) {
		vn_close((acctp != NULL ? acctp : savacctp), FWRITE,
		    NOCRED, p);
		acctp = savacctp = NULL;
	}
	rw_exit_write(&acct_lock);
}