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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/mm.h>

#include <linux/slab.h>

#include <linux/acct.h>

#include <linux/capability.h>

#include <linux/file.h>

#include <linux/tty.h>

#include <linux/security.h>

#include <linux/vfs.h>

#include <linux/jiffies.h>

#include <linux/times.h>

#include <linux/syscalls.h>

#include <linux/mount.h>

#include <asm/uaccess.h>

#include <asm/div64.h>

#include <linux/blkdev.h> /* sector_div */

/*

 * 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 void do_acct_process(struct file *);

/*

 * This structure is used so that all the data protected by lock

 * can be placed in the same cache line as the lock.  This primes

 * the cache line to have the data after getting the lock.

 */

struct acct_glbs {

        spinlock_t              lock;

        volatile int            active;

        volatile int            needcheck;

        struct file             *file;

        struct timer_list       timer;

};

static struct acct_glbs acct_globals __cacheline_aligned =

        {__SPIN_LOCK_UNLOCKED(acct_globals.lock)};

/*

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

 */

static void acct_timeout(unsigned long unused)

{

        acct_globals.needcheck = 1;

}

/*

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

 */

static int check_free_space(struct file *file)

{

        struct kstatfs sbuf;

        int res;

        int act;

        sector_t resume;

        sector_t suspend;

        spin_lock(&acct_globals.lock);

        res = acct_globals.active;

        if (!file || !acct_globals.needcheck)

                goto out;

        spin_unlock(&acct_globals.lock);

        /* May block */

        if (vfs_statfs(file->f_path.dentry, &sbuf))

                return res;

        suspend = sbuf.f_blocks * SUSPEND;

        resume = sbuf.f_blocks * RESUME;

        sector_div(suspend, 100);

        sector_div(resume, 100);

        if (sbuf.f_bavail <= suspend)

                act = -1;

        else if (sbuf.f_bavail >= resume)

                act = 1;

        else

                act = 0;

        /*

         * If some joker switched acct_globals.file under us we'ld better be

         * silent and _not_ touch anything.

         */

        spin_lock(&acct_globals.lock);

        if (file != acct_globals.file) {

                if (act)

                        res = act>0;

                goto out;

        }

        if (acct_globals.active) {

                if (act < 0) {

                        acct_globals.active = 0;

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

                }

        } else {

                if (act > 0) {

                        acct_globals.active = 1;

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

                }

        }

        del_timer(&acct_globals.timer);

        acct_globals.needcheck = 0;

        acct_globals.timer.expires = jiffies + ACCT_TIMEOUT*HZ;

        add_timer(&acct_globals.timer);

        res = acct_globals.active;

out:

        spin_unlock(&acct_globals.lock);

        return res;

}

/*

 * Close the old accounting file (if currently open) and then replace

 * it with file (if non-NULL).

 *

 * NOTE: acct_globals.lock MUST be held on entry and exit.

 */

static void acct_file_reopen(struct file *file)

{

        struct file *old_acct = NULL;

        if (acct_globals.file) {

                old_acct = acct_globals.file;

                del_timer(&acct_globals.timer);

                acct_globals.active = 0;

                acct_globals.needcheck = 0;

                acct_globals.file = NULL;

        }

        if (file) {

                acct_globals.file = file;

                acct_globals.needcheck = 0;

                acct_globals.active = 1;

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

                init_timer(&acct_globals.timer);

                acct_globals.timer.function = acct_timeout;

                acct_globals.timer.expires = jiffies + ACCT_TIMEOUT*HZ;

                add_timer(&acct_globals.timer);

        }

        if (old_acct) {

                mnt_unpin(old_acct->f_path.mnt);

                spin_unlock(&acct_globals.lock);

                do_acct_process(old_acct);

                filp_close(old_acct, NULL);

                spin_lock(&acct_globals.lock);

        }

}

static int acct_on(char *name)

{

        struct file *file;

        int error;

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

        file = filp_open(name, O_WRONLY|O_APPEND|O_LARGEFILE, 0);

        if (IS_ERR(file))

                return PTR_ERR(file);

        if (!S_ISREG(file->f_path.dentry->d_inode->i_mode)) {

                filp_close(file, NULL);

                return -EACCES;

        }

        if (!file->f_op->write) {

                filp_close(file, NULL);

                return -EIO;

        }

        error = security_acct(file);

        if (error) {

                filp_close(file, NULL);

                return error;

        }

        spin_lock(&acct_globals.lock);

        mnt_pin(file->f_path.mnt);

        acct_file_reopen(file);

        spin_unlock(&acct_globals.lock);

        mntput(file->f_path.mnt); /* it's pinned, now give up active reference */

        return 0;

}

/**

 * sys_acct - enable/disable process accounting

 * @name: file name for accounting records or NULL to shutdown accounting

 *

 * Returns 0 for success or negative errno values for failure.

 *

 * 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 __user *name)

{

        int error;

        if (!capable(CAP_SYS_PACCT))

                return -EPERM;

        if (name) {

                char *tmp = getname(name);

                if (IS_ERR(tmp))

                        return (PTR_ERR(tmp));

                error = acct_on(tmp);

                putname(tmp);

        } else {

                error = security_acct(NULL);

                if (!error) {

                        spin_lock(&acct_globals.lock);

                        acct_file_reopen(NULL);

                        spin_unlock(&acct_globals.lock);

                }

        }

        return error;

}

/**

 * acct_auto_close - turn off a filesystem's accounting if it is on

 * @m: vfsmount being shut down

 *

 * If the accounting is turned on for a file in the subtree pointed to

 * to by m, turn accounting off.  Done when m is about to die.

 */

void acct_auto_close_mnt(struct vfsmount *m)

{

        spin_lock(&acct_globals.lock);

        if (acct_globals.file && acct_globals.file->f_path.mnt == m)

                acct_file_reopen(NULL);

        spin_unlock(&acct_globals.lock);

}

/**

 * acct_auto_close - turn off a filesystem's accounting if it is on

 * @sb: super block for the filesystem

 *

 * If the accounting is turned on for a file in the filesystem pointed

 * to by sb, turn accounting off.

 */

void acct_auto_close(struct super_block *sb)

{

        spin_lock(&acct_globals.lock);

        if (acct_globals.file &&

            acct_globals.file->f_path.mnt->mnt_sb == sb) {

                acct_file_reopen(NULL);

        }

        spin_unlock(&acct_globals.lock);

}

/*

 *  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;

}

#if ACCT_VERSION==1 || ACCT_VERSION==2

/*

 * encode an u64 into a comp2_t (24 bits)

 *

 * Format: 5 bit base 2 exponent, 20 bits mantissa.

 * The leading bit of the mantissa is not stored, but implied for

 * non-zero exponents.

 * Largest encodable value is 50 bits.

 */

#define MANTSIZE2       20                      /* 20 bit mantissa. */

#define EXPSIZE2        5                       /* 5 bit base 2 exponent. */

#define MAXFRACT2       ((1ul << MANTSIZE2) - 1) /* Maximum fractional value. */

#define MAXEXP2         ((1 <<EXPSIZE2) - 1)    /* Maximum exponent. */

static comp2_t encode_comp2_t(u64 value)

{

        int exp, rnd;

        exp = (value > (MAXFRACT2>>1));

        rnd = 0;

        while (value > MAXFRACT2) {

                rnd = value & 1;

                value >>= 1;

                exp++;

        }

        /*

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

         */

        if (rnd && (++value > MAXFRACT2)) {

                value >>= 1;

                exp++;

        }

        if (exp > MAXEXP2) {

                /* Overflow. Return largest representable number instead. */

                return (1ul << (MANTSIZE2+EXPSIZE2-1)) - 1;

        } else {

                return (value & (MAXFRACT2>>1)) | (exp << (MANTSIZE2-1));

        }

}

#endif

#if ACCT_VERSION==3

/*

 * encode an u64 into a 32 bit IEEE float

 */

static u32 encode_float(u64 value)

{

        unsigned exp = 190;

        unsigned u;

        if (value==0) return 0;

        while ((s64)value > 0){

                value <<= 1;

                exp--;

        }

        u = (u32)(value >> 40) & 0x7fffffu;

        return u | (exp << 23);

}

#endif

/*

 *  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() or when switching to a different output file.

 */

/*

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

 */

static void do_acct_process(struct file *file)

{

        struct pacct_struct *pacct = &current->signal->pacct;

        acct_t ac;

        mm_segment_t fs;

        unsigned long flim;

        u64 elapsed;

        u64 run_time;

        struct timespec uptime;

        struct tty_struct *tty;

        /*

         * 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(acct_t));

        ac.ac_version = ACCT_VERSION | ACCT_BYTEORDER;

        strlcpy(ac.ac_comm, current->comm, sizeof(ac.ac_comm));

        /* calculate run_time in nsec*/

        do_posix_clock_monotonic_gettime(&uptime);

        run_time = (u64)uptime.tv_sec*NSEC_PER_SEC + uptime.tv_nsec;

        run_time -= (u64)current->group_leader->start_time.tv_sec * NSEC_PER_SEC

                       + current->group_leader->start_time.tv_nsec;

        /* convert nsec -> AHZ */

        elapsed = nsec_to_AHZ(run_time);

#if ACCT_VERSION==3

        ac.ac_etime = encode_float(elapsed);

#else

        ac.ac_etime = encode_comp_t(elapsed < (unsigned long) -1l ?

                               (unsigned long) elapsed : (unsigned long) -1l);

#endif

#if ACCT_VERSION==1 || ACCT_VERSION==2

        {

                /* new enlarged etime field */

                comp2_t etime = encode_comp2_t(elapsed);

                ac.ac_etime_hi = etime >> 16;

                ac.ac_etime_lo = (u16) etime;

        }

#endif

        do_div(elapsed, AHZ);

        ac.ac_btime = get_seconds() - elapsed;

        /* we really need to bite the bullet and change layout */

        ac.ac_uid = current->uid;

        ac.ac_gid = current->gid;

#if ACCT_VERSION==2

        ac.ac_ahz = AHZ;

#endif

#if ACCT_VERSION==1 || ACCT_VERSION==2

        /* backward-compatible 16 bit fields */

        ac.ac_uid16 = current->uid;

        ac.ac_gid16 = current->gid;

#endif

#if ACCT_VERSION==3

        ac.ac_pid = current->tgid;

        ac.ac_ppid = current->real_parent->tgid;

#endif

        spin_lock_irq(&current->sighand->siglock);

        tty = current->signal->tty;

        ac.ac_tty = tty ? old_encode_dev(tty_devnum(tty)) : 0;

        ac.ac_utime = encode_comp_t(jiffies_to_AHZ(cputime_to_jiffies(pacct->ac_utime)));

        ac.ac_stime = encode_comp_t(jiffies_to_AHZ(cputime_to_jiffies(pacct->ac_stime)));

        ac.ac_flag = pacct->ac_flag;

        ac.ac_mem = encode_comp_t(pacct->ac_mem);

        ac.ac_minflt = encode_comp_t(pacct->ac_minflt);

        ac.ac_majflt = encode_comp_t(pacct->ac_majflt);

        ac.ac_exitcode = pacct->ac_exitcode;

        spin_unlock_irq(&current->sighand->siglock);

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

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

        ac.ac_swaps = encode_comp_t(0);

        /*

         * 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->signal->rlim[RLIMIT_FSIZE].rlim_cur;

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

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

                               sizeof(acct_t), &file->f_pos);

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

        set_fs(fs);

}

/**

 * acct_init_pacct - initialize a new pacct_struct

 * @pacct: per-process accounting info struct to initialize

 */

void acct_init_pacct(struct pacct_struct *pacct)

{

        memset(pacct, 0, sizeof(struct pacct_struct));

        pacct->ac_utime = pacct->ac_stime = cputime_zero;

}

/**

 * acct_collect - collect accounting information into pacct_struct

 * @exitcode: task exit code

 * @group_dead: not 0, if this thread is the last one in the process.

 */

void acct_collect(long exitcode, int group_dead)

{

        struct pacct_struct *pacct = &current->signal->pacct;

        unsigned long vsize = 0;

        if (group_dead && 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);

        }

        spin_lock_irq(&current->sighand->siglock);

        if (group_dead)

                pacct->ac_mem = vsize / 1024;

        if (thread_group_leader(current)) {

                pacct->ac_exitcode = exitcode;

                if (current->flags & PF_FORKNOEXEC)

                        pacct->ac_flag |= AFORK;

        }

        if (current->flags & PF_SUPERPRIV)

                pacct->ac_flag |= ASU;

        if (current->flags & PF_DUMPCORE)

                pacct->ac_flag |= ACORE;

        if (current->flags & PF_SIGNALED)

                pacct->ac_flag |= AXSIG;

        pacct->ac_utime = cputime_add(pacct->ac_utime, current->utime);

        pacct->ac_stime = cputime_add(pacct->ac_stime, current->stime);

        pacct->ac_minflt += current->min_flt;

        pacct->ac_majflt += current->maj_flt;

        spin_unlock_irq(&current->sighand->siglock);

}

/**

 * acct_process - now just a wrapper around do_acct_process

 * @exitcode: task exit code

 *

 * handles process accounting for an exiting task

 */

void acct_process(void)

{

        struct file *file = NULL;

        /*

         * accelerate the common fastpath:

         */

        if (!acct_globals.file)

                return;

        spin_lock(&acct_globals.lock);

        file = acct_globals.file;

        if (unlikely(!file)) {

                spin_unlock(&acct_globals.lock);

                return;

        }

        get_file(file);

        spin_unlock(&acct_globals.lock);

        do_acct_process(file);

        fput(file);

}