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

     /*-
      * SPDX-License-Identifier: BSD-4-Clause
      *
      * Copyright (c) 1982, 1986, 1989, 1993
      *      The Regents of the University of California.  All rights reserved.
      * (c) UNIX System Laboratories, Inc.
      * Copyright (c) 2005 Robert N. M. Watson
      * All rights reserved.
      *
     * 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.
     *
     * Copyright (c) 1994 Christopher G. Demetriou
     *
     * 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 8.1 (Berkeley) 6/14/93
     */
    
    #include <sys/cdefs.h>
    __FBSDID("$FreeBSD: releng/12.0/sys/kern/kern_acct.c 325966 2017-11-18 14:26:50Z pfg $");
    
    #include <sys/param.h>
    #include <sys/systm.h>
    #include <sys/acct.h>
    #include <sys/fcntl.h>
    #include <sys/kernel.h>
    #include <sys/kthread.h>
    #include <sys/limits.h>
    #include <sys/lock.h>
    #include <sys/malloc.h>
    #include <sys/mount.h>
    #include <sys/mutex.h>
    #include <sys/namei.h>
    #include <sys/priv.h>
    #include <sys/proc.h>
    #include <sys/resourcevar.h>
    #include <sys/sched.h>
    #include <sys/sx.h>
    #include <sys/sysctl.h>
    #include <sys/sysent.h>
    #include <sys/syslog.h>
    #include <sys/sysproto.h>
    #include <sys/tty.h>
    #include <sys/vnode.h>
    
    #include <security/mac/mac_framework.h>
   
   _Static_assert(sizeof(struct acctv3) - offsetof(struct acctv3, ac_trailer) ==
       sizeof(struct acctv2) - offsetof(struct acctv2, ac_trailer), "trailer");
   _Static_assert(sizeof(struct acctv3) - offsetof(struct acctv3, ac_len2) ==
       sizeof(struct acctv2) - offsetof(struct acctv2, ac_len2), "len2");
   
   /*
    * 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.
    * On May 2007 the historic 3 bits base 8 exponent, 13 bit fraction
    * compt_t representation described in the above reference was replaced
    * with that of IEEE-754 floats.
    *
    * 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.
    */
   
   /* Floating point definitions from <float.h>. */
   #define FLT_MANT_DIG    24              /* p */
   #define FLT_MAX_EXP     128             /* emax */
   
   /*
    * 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 uint32_t encode_timeval(struct timeval);
   static uint32_t encode_long(long);
   static void     acctwatch(void);
   static void     acct_thread(void *);
   static int      acct_disable(struct thread *, int);
   
   /*
    * Accounting vnode pointer, saved vnode pointer, and flags for each.
    * acct_sx protects against changes to the active vnode and credentials
    * while accounting records are being committed to disk.
    */
   static int               acct_configured;
   static int               acct_suspended;
   static struct vnode     *acct_vp;
   static struct ucred     *acct_cred;
   static struct plimit    *acct_limit;
   static int               acct_flags;
   static struct sx         acct_sx;
   
   SX_SYSINIT(acct, &acct_sx, "acct_sx");
   
   /*
    * State of the accounting kthread.
    */
   static int               acct_state;
   
   #define ACCT_RUNNING    1       /* Accounting kthread is running. */
   #define ACCT_EXITREQ    2       /* Accounting kthread should exit. */
   
   /*
    * 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 stops");
   
   static int acctresume = 4;      /* resume when free space risen to > 4% */
   SYSCTL_INT(_kern, OID_AUTO, acct_resume, CTLFLAG_RW,
           &acctresume, 0, "percentage of free disk space above which accounting resumes");
   
   static int acctchkfreq = 15;    /* frequency (in seconds) to check space */
   
   static int
   sysctl_acct_chkfreq(SYSCTL_HANDLER_ARGS)
   {
           int error, value;
   
           /* Write out the old value. */
           error = SYSCTL_OUT(req, &acctchkfreq, sizeof(int));
           if (error || req->newptr == NULL)
                   return (error);
   
           /* Read in and verify the new value. */
           error = SYSCTL_IN(req, &value, sizeof(int));
           if (error)
                   return (error);
           if (value <= 0)
                   return (EINVAL);
           acctchkfreq = value;
           return (0);
   }
   SYSCTL_PROC(_kern, OID_AUTO, acct_chkfreq, CTLTYPE_INT|CTLFLAG_RW,
       &acctchkfreq, 0, sysctl_acct_chkfreq, "I",
       "frequency for checking the free space");
   
   SYSCTL_INT(_kern, OID_AUTO, acct_configured, CTLFLAG_RD, &acct_configured, 0,
           "Accounting configured or not");
   
   SYSCTL_INT(_kern, OID_AUTO, acct_suspended, CTLFLAG_RD, &acct_suspended, 0,
           "Accounting suspended or not");
   
   /*
    * Accounting system call.  Written based on the specification and previous
    * implementation done by Mark Tinguely.
    */
   int
   sys_acct(struct thread *td, struct acct_args *uap)
   {
           struct nameidata nd;
           int error, flags, i, replacing;
   
           error = priv_check(td, PRIV_ACCT);
           if (error)
                   return (error);
   
           /*
            * 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) {
                   NDINIT(&nd, LOOKUP, NOFOLLOW | AUDITVNODE1,
                       UIO_USERSPACE, uap->path, td);
                   flags = FWRITE | O_APPEND;
                   error = vn_open(&nd, &flags, 0, NULL);
                   if (error)
                           return (error);
                   NDFREE(&nd, NDF_ONLY_PNBUF);
   #ifdef MAC
                   error = mac_system_check_acct(td->td_ucred, nd.ni_vp);
                   if (error) {
                           VOP_UNLOCK(nd.ni_vp, 0);
                           vn_close(nd.ni_vp, flags, td->td_ucred, td);
                           return (error);
                   }
   #endif
                   VOP_UNLOCK(nd.ni_vp, 0);
                   if (nd.ni_vp->v_type != VREG) {
                           vn_close(nd.ni_vp, flags, td->td_ucred, td);
                           return (EACCES);
                   }
   #ifdef MAC
           } else {
                   error = mac_system_check_acct(td->td_ucred, NULL);
                   if (error)
                           return (error);
   #endif
           }
   
           /*
            * Disallow concurrent access to the accounting vnode while we swap
            * it out, in order to prevent access after close.
            */
           sx_xlock(&acct_sx);
   
           /*
            * Don't log spurious disable/enable messages if we are
            * switching from one accounting file to another due to log
            * rotation.
            */
           replacing = (acct_vp != NULL && uap->path != NULL);
   
           /*
            * If accounting was previously enabled, kill the old space-watcher,
            * close the file, and (if no new file was specified, leave).  Reset
            * the suspended state regardless of whether accounting remains
            * enabled.
            */
           acct_suspended = 0;
           if (acct_vp != NULL)
                   error = acct_disable(td, !replacing);
           if (uap->path == NULL) {
                   if (acct_state & ACCT_RUNNING) {
                           acct_state |= ACCT_EXITREQ;
                           wakeup(&acct_state);
                   }
                   sx_xunlock(&acct_sx);
                   return (error);
           }
   
           /*
            * Create our own plimit object without limits. It will be assigned
            * to exiting processes.
            */
           acct_limit = lim_alloc();
           for (i = 0; i < RLIM_NLIMITS; i++)
                   acct_limit->pl_rlimit[i].rlim_cur =
                       acct_limit->pl_rlimit[i].rlim_max = RLIM_INFINITY;
   
           /*
            * Save the new accounting file vnode, and schedule the new
            * free space watcher.
            */
           acct_vp = nd.ni_vp;
           acct_cred = crhold(td->td_ucred);
           acct_flags = flags;
           if (acct_state & ACCT_RUNNING)
                   acct_state &= ~ACCT_EXITREQ;
           else {
                   /*
                    * Try to start up an accounting kthread.  We may start more
                    * than one, but if so the extras will commit suicide as
                    * soon as they start up.
                    */
                   error = kproc_create(acct_thread, NULL, NULL, 0, 0,
                       "accounting");
                   if (error) {
                           (void) acct_disable(td, 0);
                           sx_xunlock(&acct_sx);
                           log(LOG_NOTICE, "Unable to start accounting thread\n");
                           return (error);
                   }
           }
           acct_configured = 1;
           sx_xunlock(&acct_sx);
           if (!replacing)
                   log(LOG_NOTICE, "Accounting enabled\n");
           return (error);
   }
   
   /*
    * Disable currently in-progress accounting by closing the vnode, dropping
    * our reference to the credential, and clearing the vnode's flags.
    */
   static int
   acct_disable(struct thread *td, int logging)
   {
           int error;
   
           sx_assert(&acct_sx, SX_XLOCKED);
           error = vn_close(acct_vp, acct_flags, acct_cred, td);
           crfree(acct_cred);
           lim_free(acct_limit);
           acct_configured = 0;
           acct_vp = NULL;
           acct_cred = NULL;
           acct_flags = 0;
           if (logging)
                   log(LOG_NOTICE, "Accounting disabled\n");
           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 thread *td)
   {
           struct acctv3 acct;
           struct timeval ut, st, tmp;
           struct plimit *oldlim;
           struct proc *p;
           struct rusage ru;
           int t, ret;
   
           /*
            * Lockless check of accounting condition before doing the hard
            * work.
            */
           if (acct_vp == NULL || acct_suspended)
                   return (0);
   
           sx_slock(&acct_sx);
   
           /*
            * If accounting isn't enabled, don't bother.  Have to check again
            * once we own the lock in case we raced with disabling of accounting
            * by another thread.
            */
           if (acct_vp == NULL || acct_suspended) {
                   sx_sunlock(&acct_sx);
                   return (0);
           }
   
           p = td->td_proc;
   
           /*
            * Get process accounting information.
            */
   
           sx_slock(&proctree_lock);
           PROC_LOCK(p);
   
           /* (1) The terminal from which the process was started */
           if ((p->p_flag & P_CONTROLT) && p->p_pgrp->pg_session->s_ttyp)
                   acct.ac_tty = tty_udev(p->p_pgrp->pg_session->s_ttyp);
           else
                   acct.ac_tty = NODEV;
           sx_sunlock(&proctree_lock);
   
           /* (2) The name of the command that ran */
           bcopy(p->p_comm, acct.ac_comm, sizeof acct.ac_comm);
   
           /* (3) The amount of user and system time that was used */
           rufetchcalc(p, &ru, &ut, &st);
           acct.ac_utime = encode_timeval(ut);
           acct.ac_stime = encode_timeval(st);
   
           /* (4) The elapsed time the command ran (and its starting time) */
           getboottime(&tmp);
           timevaladd(&tmp, &p->p_stats->p_start);
           acct.ac_btime = tmp.tv_sec;
           microuptime(&tmp);
           timevalsub(&tmp, &p->p_stats->p_start);
           acct.ac_etime = encode_timeval(tmp);
   
           /* (5) The average amount of memory used */
           tmp = ut;
           timevaladd(&tmp, &st);
           /* Convert tmp (i.e. u + s) into hz units to match ru_i*. */
           t = tmp.tv_sec * hz + tmp.tv_usec / tick;
           if (t)
                   acct.ac_mem = encode_long((ru.ru_ixrss + ru.ru_idrss +
                       + ru.ru_isrss) / t);
           else
                   acct.ac_mem = 0;
   
           /* (6) The number of disk I/O operations done */
           acct.ac_io = encode_long(ru.ru_inblock + ru.ru_oublock);
   
           /* (7) The UID and GID of the process */
           acct.ac_uid = p->p_ucred->cr_ruid;
           acct.ac_gid = p->p_ucred->cr_rgid;
   
           /* (8) The boolean flags that tell how the process terminated, etc. */
           acct.ac_flagx = p->p_acflag;
   
           /* Setup ancillary structure fields. */
           acct.ac_flagx |= ANVER;
           acct.ac_zero = 0;
           acct.ac_version = 3;
           acct.ac_len = acct.ac_len2 = sizeof(acct);
   
           /*
            * Eliminate rlimits (file size limit in particular).
            */
           oldlim = p->p_limit;
           p->p_limit = lim_hold(acct_limit);
           PROC_UNLOCK(p);
           lim_free(oldlim);
   
           /*
            * Write the accounting information to the file.
            */
           ret = vn_rdwr(UIO_WRITE, acct_vp, (caddr_t)&acct, sizeof (acct),
               (off_t)0, UIO_SYSSPACE, IO_APPEND|IO_UNIT, acct_cred, NOCRED,
               NULL, td);
           sx_sunlock(&acct_sx);
           return (ret);
   }
   
   /* FLOAT_CONVERSION_START (Regression testing; don't remove this line.) */
   
   /* Convert timevals and longs into IEEE-754 bit patterns. */
   
   /* Mantissa mask (MSB is implied, so subtract 1). */
   #define MANT_MASK ((1 << (FLT_MANT_DIG - 1)) - 1)
   
   /*
    * We calculate integer values to a precision of approximately
    * 28 bits.
    * This is high-enough precision to fill the 24 float bits
    * and low-enough to avoid overflowing the 32 int bits.
    */
   #define CALC_BITS 28
   
   /* log_2(1000000). */
   #define LOG2_1M 20
   
   /*
    * Convert the elements of a timeval into a 32-bit word holding
    * the bits of a IEEE-754 float.
    * The float value represents the timeval's value in microsecond units.
    */
   static uint32_t
   encode_timeval(struct timeval tv)
   {
           int log2_s;
           int val, exp;   /* Unnormalized value and exponent */
           int norm_exp;   /* Normalized exponent */
           int shift;
   
           /*
            * First calculate value and exponent to about CALC_BITS precision.
            * Note that the following conditionals have been ordered so that
            * the most common cases appear first.
            */
           if (tv.tv_sec == 0) {
                   if (tv.tv_usec == 0)
                           return (0);
                   exp = 0;
                   val = tv.tv_usec;
           } else {
                   /*
                    * Calculate the value to a precision of approximately
                    * CALC_BITS.
                    */
                   log2_s = fls(tv.tv_sec) - 1;
                   if (log2_s + LOG2_1M < CALC_BITS) {
                           exp = 0;
                           val = 1000000 * tv.tv_sec + tv.tv_usec;
                   } else {
                           exp = log2_s + LOG2_1M - CALC_BITS;
                           val = (unsigned int)(((uint64_t)1000000 * tv.tv_sec +
                               tv.tv_usec) >> exp);
                   }
           }
           /* Now normalize and pack the value into an IEEE-754 float. */
           norm_exp = fls(val) - 1;
           shift = FLT_MANT_DIG - norm_exp - 1;
   #ifdef ACCT_DEBUG
           printf("val=%d exp=%d shift=%d log2(val)=%d\n",
               val, exp, shift, norm_exp);
           printf("exp=%x mant=%x\n", FLT_MAX_EXP - 1 + exp + norm_exp,
               ((shift > 0 ? (val << shift) : (val >> -shift)) & MANT_MASK));
   #endif
           return (((FLT_MAX_EXP - 1 + exp + norm_exp) << (FLT_MANT_DIG - 1)) |
               ((shift > 0 ? val << shift : val >> -shift) & MANT_MASK));
   }
   
   /*
    * Convert a non-negative long value into the bit pattern of
    * an IEEE-754 float value.
    */
   static uint32_t
   encode_long(long val)
   {
           int norm_exp;   /* Normalized exponent */
           int shift;
   
           if (val == 0)
                   return (0);
           if (val < 0) {
                   log(LOG_NOTICE,
                       "encode_long: negative value %ld in accounting record\n",
                       val);
                   val = LONG_MAX;
           }
           norm_exp = fls(val) - 1;
           shift = FLT_MANT_DIG - norm_exp - 1;
   #ifdef ACCT_DEBUG
           printf("val=%d shift=%d log2(val)=%d\n",
               val, shift, norm_exp);
           printf("exp=%x mant=%x\n", FLT_MAX_EXP - 1 + exp + norm_exp,
               ((shift > 0 ? (val << shift) : (val >> -shift)) & MANT_MASK));
   #endif
           return (((FLT_MAX_EXP - 1 + norm_exp) << (FLT_MANT_DIG - 1)) |
               ((shift > 0 ? val << shift : val >> -shift) & MANT_MASK));
   }
   
   /* FLOAT_CONVERSION_END (Regression testing; don't remove this line.) */
   
   /*
    * Periodically check the filesystem 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)
   {
           struct statfs *sp;
   
           sx_assert(&acct_sx, SX_XLOCKED);
   
           /*
            * If accounting was disabled before our kthread was scheduled,
            * then acct_vp might be NULL.  If so, just ask our kthread to
            * exit and return.
            */
           if (acct_vp == NULL) {
                   acct_state |= ACCT_EXITREQ;
                   return;
           }
   
           /*
            * If our vnode is no longer valid, tear it down and signal the
            * accounting thread to die.
            */
           if (acct_vp->v_type == VBAD) {
                   (void) acct_disable(NULL, 1);
                   acct_state |= ACCT_EXITREQ;
                   return;
           }
   
           /*
            * Stopping here is better than continuing, maybe it will be VBAD
            * next time around.
            */
           sp = malloc(sizeof(struct statfs), M_STATFS, M_WAITOK);
           if (VFS_STATFS(acct_vp->v_mount, sp) < 0) {
                   free(sp, M_STATFS);
                   return;
           }
           if (acct_suspended) {
                   if (sp->f_bavail > (int64_t)(acctresume * sp->f_blocks /
                       100)) {
                           acct_suspended = 0;
                           log(LOG_NOTICE, "Accounting resumed\n");
                   }
           } else {
                   if (sp->f_bavail <= (int64_t)(acctsuspend * sp->f_blocks /
                       100)) {
                           acct_suspended = 1;
                           log(LOG_NOTICE, "Accounting suspended\n");
                   }
           }
           free(sp, M_STATFS);
   }
   
   /*
    * The main loop for the dedicated kernel thread that periodically calls
    * acctwatch().
    */
   static void
   acct_thread(void *dummy)
   {
           u_char pri;
   
           /* This is a low-priority kernel thread. */
           pri = PRI_MAX_KERN;
           thread_lock(curthread);
           sched_prio(curthread, pri);
           thread_unlock(curthread);
   
           /* If another accounting kthread is already running, just die. */
           sx_xlock(&acct_sx);
           if (acct_state & ACCT_RUNNING) {
                   sx_xunlock(&acct_sx);
                   kproc_exit(0);
           }
           acct_state |= ACCT_RUNNING;
   
           /* Loop until we are asked to exit. */
           while (!(acct_state & ACCT_EXITREQ)) {
   
                   /* Perform our periodic checks. */
                   acctwatch();
   
                   /*
                    * We check this flag again before sleeping since the
                    * acctwatch() might have shut down accounting and asked us
                    * to exit.
                    */
                   if (!(acct_state & ACCT_EXITREQ)) {
                           sx_sleep(&acct_state, &acct_sx, 0, "-",
                               acctchkfreq * hz);
                   }
           }
   
           /*
            * Acknowledge the exit request and shutdown.  We clear both the
            * exit request and running flags.
            */
           acct_state = 0;
           sx_xunlock(&acct_sx);
           kproc_exit(0);
   }

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