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/*

 *  linux/kernel/acct.c

 *

 *  BSD Process Accounting for Linux

 *

 *  Author: Marco van Wieringen <mvw@planets.elm.net>

 *

 *  Some code based on ideas and code from:

 *  Thomas K. Dyas <tdyas@eden.rutgers.edu>

 *

 *  This file implements BSD-style process accounting. Whenever any

 *  process exits, an accounting record of type "struct acct" is

 *  written to the file specified with the acct() system call. It is

 *  up to user-level programs to do useful things with the accounting

 *  log. The kernel just provides the raw accounting information.

 *

 * (C) Copyright 1995 - 1997 Marco van Wieringen - ELM Consultancy B.V.

 *

 *  Plugged two leaks. 1) It didn't return acct_file into the free_filps if

 *  the file happened to be read-only. 2) If the accounting was suspended

 *  due to the lack of space it happily allowed to reopen it and completely

 *  lost the old acct_file. 3/10/98, Al Viro.

 *

 *  Now we silently close acct_file on attempt to reopen. Cleaned sys_acct().

 *  XTerms and EMACS are manifestations of pure evil. 21/10/98, AV.

 *

 *  Fixed a nasty interaction with with sys_umount(). If the accointing

 *  was suspeneded we failed to stop it on umount(). Messy.

 *  Another one: remount to readonly didn't stop accounting.

 *      Question: what should we do if we have CAP_SYS_ADMIN but not

 *  CAP_SYS_PACCT? Current code does the following: umount returns -EBUSY

 *  unless we are messing with the root. In that case we are getting a

 *  real mess with do_remount_sb(). 9/11/98, AV.

 *

 *  Fixed a bunch of races (and pair of leaks). Probably not the best way,

 *  but this one obviously doesn't introduce deadlocks. Later. BTW, found

 *  one race (and leak) in BSD implementation.

 *  OK, that's better. ANOTHER race and leak in BSD variant. There always

 *  is one more bug... 10/11/98, AV.

 *

 *      Oh, fsck... Oopsable SMP race in do_process_acct() - we must hold

 * ->mmap_sem to walk the vma list of current->mm. Nasty, since it leaks

 * a struct file opened for write. Fixed. 2/6/2000, AV.

 */

#include <linux/config.h>

#include <linux/errno.h>

#include <linux/kernel.h>

#ifdef CONFIG_BSD_PROCESS_ACCT

#include <linux/mm.h>

#include <linux/slab.h>

#include <linux/acct.h>

#include <linux/smp_lock.h>

#include <linux/file.h>

#include <linux/tty.h>

#include <asm/uaccess.h>

/*

 * These constants control the amount of freespace that suspend and

 * resume the process accounting system, and the time delay between

 * each check.

 * Turned into sysctl-controllable parameters. AV, 12/11/98

 */

int acct_parm[3] = {4, 2, 30};

#define RESUME          (acct_parm[0])  /* >foo% free space - resume */

#define SUSPEND         (acct_parm[1])  /* <foo% free space - suspend */

#define ACCT_TIMEOUT    (acct_parm[2])  /* foo second timeout between checks */

/*

 * External references and all of the globals.

 */

static volatile int acct_active;

static volatile int acct_needcheck;

static struct file *acct_file;

static struct timer_list acct_timer;

static void do_acct_process(long, struct file *);

/*

 * Called whenever the timer says to check the free space.

 */

static void acct_timeout(unsigned long unused)

{

        acct_needcheck = 1;

}

/*

 * Check the amount of free space and suspend/resume accordingly.

 */

static int check_free_space(struct file *file)

{

        struct statfs sbuf;

        int res;

        int act;

        lock_kernel();

        res = acct_active;

        if (!file || !acct_needcheck)

                goto out;

        unlock_kernel();

        /* May block */

        if (vfs_statfs(file->f_dentry->d_inode->i_sb, &sbuf))

                return res;

        if (sbuf.f_bavail <= SUSPEND * sbuf.f_blocks / 100)

                act = -1;

        else if (sbuf.f_bavail >= RESUME * sbuf.f_blocks / 100)

                act = 1;

        else

                act = 0;

        /*

         * If some joker switched acct_file under us we'ld better be

         * silent and _not_ touch anything.

         */

        lock_kernel();

        if (file != acct_file) {

                if (act)

                        res = act>0;

                goto out;

        }

        if (acct_active) {

                if (act < 0) {

                        acct_active = 0;

                        printk(KERN_INFO "Process accounting paused\n");

                }

        } else {

                if (act > 0) {

                        acct_active = 1;

                        printk(KERN_INFO "Process accounting resumed\n");

                }

        }

        del_timer(&acct_timer);

        acct_needcheck = 0;

        acct_timer.expires = jiffies + ACCT_TIMEOUT*HZ;

        add_timer(&acct_timer);

        res = acct_active;

out:

        unlock_kernel();

        return res;

}

/*

 *  sys_acct() is the only system call needed to implement process

 *  accounting. It takes the name of the file where accounting records

 *  should be written. If the filename is NULL, accounting will be

 *  shutdown.

 */

asmlinkage long sys_acct(const char *name)

{

        struct file *file = NULL, *old_acct = NULL;

        char *tmp;

        int error;

        if (!capable(CAP_SYS_PACCT))

                return -EPERM;

        if (name) {

                tmp = getname(name);

                error = PTR_ERR(tmp);

                if (IS_ERR(tmp))

                        goto out;

                /* Difference from BSD - they don't do O_APPEND */

                file = filp_open(tmp, O_WRONLY|O_APPEND, 0);

                putname(tmp);

                if (IS_ERR(file)) {

                        error = PTR_ERR(file);

                        goto out;

                }

                error = -EACCES;

                if (!S_ISREG(file->f_dentry->d_inode->i_mode))

                        goto out_err;

                error = -EIO;

                if (!file->f_op->write)

                        goto out_err;

        }

        error = 0;

        lock_kernel();

        if (acct_file) {

                old_acct = acct_file;

                del_timer(&acct_timer);

                acct_active = 0;

                acct_needcheck = 0;

                acct_file = NULL;

        }

        if (name) {

                acct_file = file;

                acct_needcheck = 0;

                acct_active = 1;

                /* It's been deleted if it was used before so this is safe */

                init_timer(&acct_timer);

                acct_timer.function = acct_timeout;

                acct_timer.expires = jiffies + ACCT_TIMEOUT*HZ;

                add_timer(&acct_timer);

        }

        unlock_kernel();

        if (old_acct) {

                do_acct_process(0,old_acct);

                filp_close(old_acct, NULL);

        }

out:

        return error;

out_err:

        filp_close(file, NULL);

        goto out;

}

void acct_auto_close(kdev_t dev)

{

        lock_kernel();

        if (acct_file && acct_file->f_dentry->d_inode->i_dev == dev)

                sys_acct(NULL);

        unlock_kernel();

}

/*

 *  encode an unsigned long into a comp_t

 *

 *  This routine has been adopted from the encode_comp_t() function in

 *  the kern_acct.c file of the FreeBSD operating system. The encoding

 *  is a 13-bit fraction with a 3-bit (base 8) exponent.

 */

#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(unsigned long value)

{

        int exp, rnd;

        exp = rnd = 0;

        while (value > MAXFRACT) {

                rnd = value & (1 << (EXPSIZE - 1));     /* Round up? */

                value >>= EXPSIZE;      /* Base 8 exponent == 3 bit shift. */

                exp++;

        }

        /*

         * If we need to round up, do it (and handle overflow correctly).

         */

        if (rnd && (++value > MAXFRACT)) {

                value >>= EXPSIZE;

                exp++;

        }

        /*

         * Clean it up and polish it off.

         */

        exp <<= MANTSIZE;               /* Shift the exponent into place */

        exp += value;                   /* and add on the mantissa. */

        return exp;

}

/*

 *  Write an accounting entry for an exiting process

 *

 *  The acct_process() call is the workhorse of the process

 *  accounting system. The struct acct is built here and then written

 *  into the accounting file. This function should only be called from

 *  do_exit().

 */

/*

 *  do_acct_process does all actual work. Caller holds the reference to file.

 */

static void do_acct_process(long exitcode, struct file *file)

{

        struct acct ac;

        mm_segment_t fs;

        unsigned long vsize;

        unsigned long flim;

        /*

         * First check to see if there is enough free_space to continue

         * the process accounting system.

         */

        if (!check_free_space(file))

                return;

        /*

         * Fill the accounting struct with the needed info as recorded

         * by the different kernel functions.

         */

        memset((caddr_t)&ac, 0, sizeof(struct acct));

        strncpy(ac.ac_comm, current->comm, ACCT_COMM);

        ac.ac_comm[ACCT_COMM - 1] = '\0';

        ac.ac_btime = CT_TO_SECS(current->start_time) + (xtime.tv_sec - (jiffies / HZ));

        ac.ac_etime = encode_comp_t(jiffies - current->start_time);

        ac.ac_utime = encode_comp_t(current->times.tms_utime);

        ac.ac_stime = encode_comp_t(current->times.tms_stime);

        ac.ac_uid = current->uid;

        ac.ac_gid = current->gid;

        ac.ac_tty = (current->tty) ? kdev_t_to_nr(current->tty->device) : 0;

        ac.ac_flag = 0;

        if (current->flags & PF_FORKNOEXEC)

                ac.ac_flag |= AFORK;

        if (current->flags & PF_SUPERPRIV)

                ac.ac_flag |= ASU;

        if (current->flags & PF_DUMPCORE)

                ac.ac_flag |= ACORE;

        if (current->flags & PF_SIGNALED)

                ac.ac_flag |= AXSIG;

        vsize = 0;

        if (current->mm) {

                struct vm_area_struct *vma;

                down_read(&current->mm->mmap_sem);

                vma = current->mm->mmap;

                while (vma) {

                        vsize += vma->vm_end - vma->vm_start;

                        vma = vma->vm_next;

                }

                up_read(&current->mm->mmap_sem);

        }

        vsize = vsize / 1024;

        ac.ac_mem = encode_comp_t(vsize);

        ac.ac_io = encode_comp_t(0 /* current->io_usage */);     /* %% */

        ac.ac_rw = encode_comp_t(ac.ac_io / 1024);

        ac.ac_minflt = encode_comp_t(current->min_flt);

        ac.ac_majflt = encode_comp_t(current->maj_flt);

        ac.ac_swaps = encode_comp_t(current->nswap);

        ac.ac_exitcode = exitcode;

        /*

         * Kernel segment override to datasegment and write it

         * to the accounting file.

         */

        fs = get_fs();

        set_fs(KERNEL_DS);

        /*

         * Accounting records are not subject to resource limits.

         */

        flim = current->rlim[RLIMIT_FSIZE].rlim_cur;

        current->rlim[RLIMIT_FSIZE].rlim_cur = RLIM_INFINITY;

        file->f_op->write(file, (char *)&ac,

                               sizeof(struct acct), &file->f_pos);

        current->rlim[RLIMIT_FSIZE].rlim_cur = flim;

        set_fs(fs);

}

/*

 * acct_process - now just a wrapper around do_acct_process

 */

int acct_process(long exitcode)

{

        struct file *file = NULL;

        lock_kernel();

        if (acct_file) {

                file = acct_file;

                get_file(file);

                unlock_kernel();

                do_acct_process(exitcode, file);

                fput(file);

        } else

                unlock_kernel();

        return 0;

}

#else

/*

 * Dummy system call when BSD process accounting is not configured

 * into the kernel.

 */

asmlinkage long sys_acct(const char * filename)

{

        return -ENOSYS;

}

#endif