/*	$NetBSD: kern_acct.c,v 1.49 2000/05/08 19:06:36 thorpej 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. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *	This product includes software developed by the University of
 *	California, Berkeley and its contributors.
 * 4. 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	8.8 (Berkeley) 5/14/95
 */

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/proc.h>
#include <sys/mount.h>
#include <sys/vnode.h>
#include <sys/file.h>
#include <sys/syslog.h>
#include <sys/kernel.h>
#include <sys/kthread.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/namei.h>
#include <sys/errno.h>
#include <sys/acct.h>
#include <sys/resourcevar.h>
#include <sys/ioctl.h>
#include <sys/tty.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.
 */

/*
 * The global accounting state and related data.  Gain the lock before
 * accessing these variables.
 */
enum {
	ACCT_STOP,
	ACCT_ACTIVE,
	ACCT_SUSPENDED
} acct_state;				/* The current accounting state. */
struct vnode *acct_vp;			/* Accounting vnode pointer. */
struct ucred *acct_ucred;		/* Credential of accounting file
					   owner (i.e root).  Used when
 					   accounting file i/o.  */
struct proc *acct_dkwatcher;		/* Free disk space checker. */

/*
 * Lock to serialize system calls and kernel threads.
 */
struct	lock acct_lock;
#define	ACCT_LOCK()						\
do {								\
	(void) lockmgr(&acct_lock, LK_EXCLUSIVE, NULL);		\
} while (/* CONSTCOND */0)
#define	ACCT_UNLOCK()						\
do {								\
	(void) lockmgr(&acct_lock, LK_RELEASE, NULL);		\
} while (/* CONSTCOND */0)

/*
 * 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
 */
comp_t	encode_comp_t __P((u_long, u_long));
void	acctwatch __P((void *));
void	acct_stop __P((void));
int	acct_chkfree __P((void));

/*
 * 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	acctchkfreq = 15;	/* frequency (in seconds) to check space */

void
acct_init()
{

	acct_state = ACCT_STOP;
	acct_vp = NULLVP;
	acct_ucred = NULL;
	lockinit(&acct_lock, PWAIT, "acctlk", 0, 0);
}

void
acct_stop()
{
	int error;

	if (acct_vp != NULLVP && acct_vp->v_type != VBAD) {
		error = vn_close(acct_vp, FWRITE, acct_ucred, NULL);
#ifdef DIAGNOSTIC
		if (error != 0)
			printf("acct_stop: failed to close, errno = %d\n",
			    error);
#endif
		acct_vp = NULLVP;
	}
	if (acct_ucred != NULL) {
		crfree(acct_ucred);
		acct_ucred = NULL;
	}
	acct_state = ACCT_STOP;
}

int
acct_chkfree()
{
	int error;
	struct statfs sb;

	error = VFS_STATFS(acct_vp->v_mount, &sb, NULL);
	if (error != 0)
		return (error);

	switch (acct_state) {
	case ACCT_SUSPENDED:
		if (sb.f_bavail > acctresume * sb.f_blocks / 100) {
			acct_state = ACCT_ACTIVE;
			log(LOG_NOTICE, "Accounting resumed\n");
		}
		break;
	case ACCT_ACTIVE:
		if (sb.f_bavail <= acctsuspend * sb.f_blocks / 100) {
			acct_state = ACCT_SUSPENDED;
			log(LOG_NOTICE, "Accounting suspended\n");
		}
		break;
	case ACCT_STOP:
		break;
	}
	return (0);
}

/*
 * Accounting system call.  Written based on the specification and
 * previous implementation done by Mark Tinguely.
 */
int
sys_acct(p, v, retval)
	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->p_ucred, &p->p_acflag)) != 0)
		return (error);

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

	ACCT_LOCK();

	/*
	 * If accounting was previously enabled, kill the old space-watcher,
	 * free credential for accounting file i/o,
	 * ... (and, if no new file was specified, leave).
	 */
	acct_stop();
	if (SCARG(uap, path) == NULL)
		goto out;

	/*
	 * Save the new accounting file vnode and credential,
	 * and schedule the new free space watcher.
	 */
	acct_state = ACCT_ACTIVE;
	acct_vp = nd.ni_vp;
	acct_ucred = p->p_ucred;
	crhold(acct_ucred);

	error = acct_chkfree();		/* Initial guess. */
	if (error != 0) {
		acct_stop();
		goto out;
	}

	if (acct_dkwatcher == NULL) {
		error = kthread_create1(acctwatch, NULL, &acct_dkwatcher,
		    "acctwatch");
		if (error != 0)
			acct_stop();
	}

 out:
	ACCT_UNLOCK();
	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(p)
	struct proc *p;
{
	struct acct acct;
	struct rusage *r;
	struct timeval ut, st, tmp;
	int s, t, error = 0;
	struct plimit *oplim = NULL;

	ACCT_LOCK();

	/* If accounting isn't enabled, don't bother */
	if (acct_state != ACCT_ACTIVE)
		goto out;

	/*
	 * Raise the file limit so that accounting can't be stopped by
	 * the user.
	 *
	 * XXX We should think about the CPU limit, too.
	 */
	if (p->p_limit->p_refcnt > 1) {
		oplim = p->p_limit;
		p->p_limit = limcopy(p->p_limit);
	}
	p->p_rlimit[RLIMIT_FSIZE].rlim_cur = RLIM_INFINITY;

	/*
	 * Get process accounting information.
	 */

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

	/* (2) The amount of user and system time that was used */
	calcru(p, &ut, &st, NULL);
	acct.ac_utime = encode_comp_t(ut.tv_sec, ut.tv_usec);
	acct.ac_stime = encode_comp_t(st.tv_sec, st.tv_usec);

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

	/* (4) The average amount of memory used */
	r = &p->p_stats->p_ru;
	timeradd(&ut, &st, &tmp);
	t = tmp.tv_sec * hz + tmp.tv_usec / 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 = p->p_cred->p_ruid;
	acct.ac_gid = p->p_cred->p_rgid;

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

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

	/*
	 * Now, just write the accounting information to the file.
	 */
	VOP_LEASE(acct_vp, p, p->p_ucred, LEASE_WRITE);
	error = vn_rdwr(UIO_WRITE, acct_vp, (caddr_t)&acct,
	    sizeof(acct), (off_t)0, UIO_SYSSPACE, IO_APPEND|IO_UNIT,
	    acct_ucred, NULL, p);
	if (error != 0)
		log(LOG_ERR, "Accounting: write failed %d\n", error);

	if (oplim) {
		limfree(p->p_limit);
		p->p_limit = oplim;
	}

 out:
	ACCT_UNLOCK();
	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(s, us)
	u_long s, 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.
 */
void
acctwatch(arg)
	void *arg;
{
	int error;

	log(LOG_NOTICE, "Accounting started\n");
	ACCT_LOCK();
	while (acct_state != ACCT_STOP) {
		if (acct_vp->v_type == VBAD) {
			log(LOG_NOTICE, "Accounting terminated\n");
			acct_stop();
			continue;
		}

		error = acct_chkfree();
#ifdef DIAGNOSTIC
		if (error != 0)
			printf("acctwatch: failed to statfs, error = %d\n",
			    error);
#endif

		ACCT_UNLOCK();
		error = tsleep(acctwatch, PSWP, "actwat", acctchkfreq * hz);
		ACCT_LOCK();
#ifdef DIAGNOSTIC
		if (error != 0 && error != EWOULDBLOCK)
			printf("acctwatch: sleep error %d\n", error);
#endif
	}
	acct_dkwatcher = NULL;
	ACCT_UNLOCK();

	kthread_exit(0);
}