FreeBSD/Linux Kernel Cross Reference
sys/kern/kern_acct.c

     /*      $OpenBSD: kern_acct.c,v 1.47 2022/08/14 01:58:27 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);
   }

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