/*-
 * 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
 * $FreeBSD: src/sys/kern/kern_acct.c,v 1.23.2.1 2002/07/24 18:33:55 johan Exp $
 */

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/sysmsg.h>
#include <sys/proc.h>
#include <sys/caps.h>
#include <sys/mount.h>
#include <sys/vnode.h>
#include <sys/fcntl.h>
#include <sys/syslog.h>
#include <sys/kernel.h>
#include <sys/sysent.h>
#include <sys/sysctl.h>
#include <sys/nlookup.h>
#include <sys/acct.h>
#include <sys/resourcevar.h>
#include <sys/tty.h>

#include <vm/vm_zone.h>

static struct lock acct_lock = LOCK_INITIALIZER("acct_lock", 0, 0);

/*
 * 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.
 * The former's operation is described in Leffler, et al., and the latter
 * was provided by UCB with the 4.4BSD-Lite release
 */
static comp_t	encode_comp_t (u_long, u_long);
static void	acctwatch (void *);

/*
 * Accounting callout handle used for periodic scheduling of
 * acctwatch.
 */
static struct	callout acctwatch_handle;

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

/*
 * Values associated with enabling and disabling accounting
 */
static int acctsuspend = 2;	/* stop accounting when < 2% free space left */
SYSCTL_INT(_kern, OID_AUTO, acct_suspend, CTLFLAG_RW,
	&acctsuspend, 0, "Percentage of free disk space below which accounting will be suspended");

static int acctresume = 4;	/* resume when free space risen to > 4% */
SYSCTL_INT(_kern, OID_AUTO, acct_resume, CTLFLAG_RW,
	&acctresume, 0, "Minimum percentage of free disk space needed to resume accounting");

static int acctchkfreq = 15;	/* frequency (in seconds) to check space */
SYSCTL_INT(_kern, OID_AUTO, acct_chkfreq, CTLFLAG_RW,
	&acctchkfreq, 0, "Frequency (in seconds) of free disk space checking");

static void
acct_init(void *arg __unused)
{
	callout_init_lk(&acctwatch_handle, &acct_lock);
}
SYSINIT(acct, SI_SUB_DRIVERS, SI_ORDER_ANY, acct_init, NULL);

/*
 * Accounting system call.  Written based on the specification and
 * previous implementation done by Mark Tinguely.
 *
 * acct(char *path)
 *
 * MPALMOSTSAFE
 */
int
sys_acct(struct sysmsg *sysmsg, const struct acct_args *uap)
{
	struct nlookupdata nd;
	struct vnode *vp;
	int error;

	error = caps_priv_check_self(SYSCAP_NOACCT);
	if (error)
		return (error);

	lockmgr(&acct_lock, LK_EXCLUSIVE);

	/*
	 * If accounting is to be started to a file, open that file for
	 * appending and make sure it's a 'normal'.
	 */
	if (uap->path != NULL) {
		error = nlookup_init(&nd, uap->path, UIO_USERSPACE,
					NLC_LOCKVP);
		if (error == 0)
			error = vn_open(&nd, NULL, FWRITE | O_APPEND, 0);
		if (error == 0 && nd.nl_open_vp->v_type != VREG) 
			error = EACCES;
		if (error) {
			nlookup_done(&nd);
			goto done;
		}
		vp = nd.nl_open_vp;
		nd.nl_open_vp = NULL;
		nlookup_done(&nd);

		vn_unlock(vp);
	} else {
		vp = NULL;
	}

	/*
	 * If accounting was previously enabled, kill the old space-watcher,
	 * close the file.
	 */
	if (acctp != NULLVP || savacctp != NULLVP) {
		callout_stop(&acctwatch_handle);
		error = vn_close((acctp != NULLVP ? acctp : savacctp),
				FWRITE | O_APPEND, NULL);
		acctp = savacctp = NULLVP;
	}

	/*
	 * If no new file opened then leave.  We never did an nlookup so
	 * don't try cleaning it up.
	 */
	if (uap->path == NULL)
		goto done;

	/*
	 * Save the new accounting file vnode, and schedule the new
	 * free space watcher.
	 */
	acctp = vp;
	acctwatch(NULL);
done:
	lockmgr(&acct_lock, LK_RELEASE);

	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 rusage *r;
	struct rusage ru;
	struct timeval tmp;
	struct rlimit rlim;
	int t;
	int error;
	struct vnode *vp;

	/*
	 * If accounting isn't enabled, don't bother.  Lock acct_lock
	 * make sure.
	 */
	if (acctp == NULLVP)
		return 0;
	lockmgr(&acct_lock, LK_SHARED);
	vp = acctp;
	if (vp == NULLVP) {
		lockmgr(&acct_lock, LK_RELEASE);
		return 0;
	}

	/*
	 * Get process accounting information.
	 */

	/* (1) The name of the command that ran */
	bcopy(p->p_comm, acct.ac_comm, sizeof acct.ac_comm);

	/* (2) The amount of user and system time that was used */
	calcru_proc(p, &ru);
	acct.ac_utime = encode_comp_t(ru.ru_utime.tv_sec, ru.ru_utime.tv_usec);
	acct.ac_stime = encode_comp_t(ru.ru_stime.tv_sec, ru.ru_stime.tv_usec);

	/* (3) The elapsed time the commmand ran (and its starting time) */
	acct.ac_btime = p->p_start.tv_sec;
	microtime(&tmp);
	timevalsub(&tmp, &p->p_start);
	acct.ac_etime = encode_comp_t(tmp.tv_sec, tmp.tv_usec);

	/* (4) The average amount of memory used */
	r = &p->p_ru;
	tmp = ru.ru_utime;
	timevaladd(&tmp, &ru.ru_stime);
	t = tmp.tv_sec * hz + tmp.tv_usec / ustick;
	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 = p->p_ucred->cr_ruid;
	acct.ac_gid = p->p_ucred->cr_rgid;

	/* (7) The terminal from which the process was started */
	if ((p->p_flags & P_CONTROLT) && p->p_pgrp->pg_session->s_ttyp) {
		acct.ac_tty =
		    devid_from_dev(p->p_pgrp->pg_session->s_ttyp->t_dev);
	} else {
		acct.ac_tty = NOUDEV;
	}

	/* (8) The boolean flags that tell how the process terminated, etc. */
	acct.ac_flag = p->p_acflag;

	/*
	 * Eliminate any file size rlimit.
	 */
	rlim.rlim_cur = RLIM_INFINITY;
	rlim.rlim_max = RLIM_INFINITY;
	plimit_modify(p, RLIMIT_FSIZE, &rlim);

	/*
	 * 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, p->p_ucred,
			NULL);
	lockmgr(&acct_lock, LK_RELEASE);

	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. */

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

	exp = 0;
	rnd = 0;
	s *= AHZ;
	s += us / (1000000 / 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);
}

/*
 * 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.
 */
/* ARGSUSED */
static void
acctwatch(void *a)
{
	struct statfs sb;

	if (savacctp != NULLVP) {
		if (savacctp->v_type == VBAD) {
			(void) vn_close(savacctp, FWRITE | O_APPEND, NULL);
			savacctp = NULLVP;
			return;
		}
		(void)VFS_STATFS(savacctp->v_mount, &sb, proc0.p_ucred);
		if (sb.f_bavail > acctresume * sb.f_blocks / 100) {
			acctp = savacctp;
			savacctp = NULLVP;
			log(LOG_NOTICE, "Accounting resumed\n");
		}
	} else {
		if (acctp == NULLVP)
			return;
		if (acctp->v_type == VBAD) {
			(void) vn_close(acctp, FWRITE | O_APPEND, NULL);
			acctp = NULLVP;
			return;
		}
		(void)VFS_STATFS(acctp->v_mount, &sb, proc0.p_ucred);
		if (sb.f_bavail <= acctsuspend * sb.f_blocks / 100) {
			savacctp = acctp;
			acctp = NULLVP;
			log(LOG_NOTICE, "Accounting suspended\n");
		}
	}
	callout_reset(&acctwatch_handle, acctchkfreq * hz, acctwatch, NULL);
}