linux/kernel/acct.c
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   1/*
   2 *  linux/kernel/acct.c
   3 *
   4 *  BSD Process Accounting for Linux
   5 *
   6 *  Author: Marco van Wieringen <mvw@planets.elm.net>
   7 *
   8 *  Some code based on ideas and code from:
   9 *  Thomas K. Dyas <tdyas@eden.rutgers.edu>
  10 *
  11 *  This file implements BSD-style process accounting. Whenever any
  12 *  process exits, an accounting record of type "struct acct" is
  13 *  written to the file specified with the acct() system call. It is
  14 *  up to user-level programs to do useful things with the accounting
  15 *  log. The kernel just provides the raw accounting information.
  16 *
  17 * (C) Copyright 1995 - 1997 Marco van Wieringen - ELM Consultancy B.V.
  18 *
  19 *  Plugged two leaks. 1) It didn't return acct_file into the free_filps if
  20 *  the file happened to be read-only. 2) If the accounting was suspended
  21 *  due to the lack of space it happily allowed to reopen it and completely
  22 *  lost the old acct_file. 3/10/98, Al Viro.
  23 *
  24 *  Now we silently close acct_file on attempt to reopen. Cleaned sys_acct().
  25 *  XTerms and EMACS are manifestations of pure evil. 21/10/98, AV.
  26 *
  27 *  Fixed a nasty interaction with with sys_umount(). If the accointing
  28 *  was suspeneded we failed to stop it on umount(). Messy.
  29 *  Another one: remount to readonly didn't stop accounting.
  30 *      Question: what should we do if we have CAP_SYS_ADMIN but not
  31 *  CAP_SYS_PACCT? Current code does the following: umount returns -EBUSY
  32 *  unless we are messing with the root. In that case we are getting a
  33 *  real mess with do_remount_sb(). 9/11/98, AV.
  34 *
  35 *  Fixed a bunch of races (and pair of leaks). Probably not the best way,
  36 *  but this one obviously doesn't introduce deadlocks. Later. BTW, found
  37 *  one race (and leak) in BSD implementation.
  38 *  OK, that's better. ANOTHER race and leak in BSD variant. There always
  39 *  is one more bug... 10/11/98, AV.
  40 *
  41 *      Oh, fsck... Oopsable SMP race in do_process_acct() - we must hold
  42 * ->mmap_sem to walk the vma list of current->mm. Nasty, since it leaks
  43 * a struct file opened for write. Fixed. 2/6/2000, AV.
  44 */
  45
  46#include <linux/mm.h>
  47#include <linux/slab.h>
  48#include <linux/acct.h>
  49#include <linux/capability.h>
  50#include <linux/file.h>
  51#include <linux/tty.h>
  52#include <linux/security.h>
  53#include <linux/vfs.h>
  54#include <linux/jiffies.h>
  55#include <linux/times.h>
  56#include <linux/syscalls.h>
  57#include <linux/mount.h>
  58#include <asm/uaccess.h>
  59#include <asm/div64.h>
  60#include <linux/blkdev.h> /* sector_div */
  61#include <linux/pid_namespace.h>
  62
  63/*
  64 * These constants control the amount of freespace that suspend and
  65 * resume the process accounting system, and the time delay between
  66 * each check.
  67 * Turned into sysctl-controllable parameters. AV, 12/11/98
  68 */
  69
  70int acct_parm[3] = {4, 2, 30};
  71#define RESUME          (acct_parm[0])  /* >foo% free space - resume */
  72#define SUSPEND         (acct_parm[1])  /* <foo% free space - suspend */
  73#define ACCT_TIMEOUT    (acct_parm[2])  /* foo second timeout between checks */
  74
  75/*
  76 * External references and all of the globals.
  77 */
  78static void do_acct_process(struct bsd_acct_struct *acct,
  79                struct pid_namespace *ns, struct file *);
  80
  81/*
  82 * This structure is used so that all the data protected by lock
  83 * can be placed in the same cache line as the lock.  This primes
  84 * the cache line to have the data after getting the lock.
  85 */
  86struct bsd_acct_struct {
  87        int                     active;
  88        unsigned long           needcheck;
  89        struct file             *file;
  90        struct pid_namespace    *ns;
  91        struct list_head        list;
  92};
  93
  94static DEFINE_SPINLOCK(acct_lock);
  95static LIST_HEAD(acct_list);
  96
  97/*
  98 * Check the amount of free space and suspend/resume accordingly.
  99 */
 100static int check_free_space(struct bsd_acct_struct *acct, struct file *file)
 101{
 102        struct kstatfs sbuf;
 103        int res;
 104        int act;
 105        u64 resume;
 106        u64 suspend;
 107
 108        spin_lock(&acct_lock);
 109        res = acct->active;
 110        if (!file || time_is_before_jiffies(acct->needcheck))
 111                goto out;
 112        spin_unlock(&acct_lock);
 113
 114        /* May block */
 115        if (vfs_statfs(&file->f_path, &sbuf))
 116                return res;
 117        suspend = sbuf.f_blocks * SUSPEND;
 118        resume = sbuf.f_blocks * RESUME;
 119
 120        do_div(suspend, 100);
 121        do_div(resume, 100);
 122
 123        if (sbuf.f_bavail <= suspend)
 124                act = -1;
 125        else if (sbuf.f_bavail >= resume)
 126                act = 1;
 127        else
 128                act = 0;
 129
 130        /*
 131         * If some joker switched acct->file under us we'ld better be
 132         * silent and _not_ touch anything.
 133         */
 134        spin_lock(&acct_lock);
 135        if (file != acct->file) {
 136                if (act)
 137                        res = act>0;
 138                goto out;
 139        }
 140
 141        if (acct->active) {
 142                if (act < 0) {
 143                        acct->active = 0;
 144                        printk(KERN_INFO "Process accounting paused\n");
 145                }
 146        } else {
 147                if (act > 0) {
 148                        acct->active = 1;
 149                        printk(KERN_INFO "Process accounting resumed\n");
 150                }
 151        }
 152
 153        acct->needcheck = jiffies + ACCT_TIMEOUT*HZ;
 154        res = acct->active;
 155out:
 156        spin_unlock(&acct_lock);
 157        return res;
 158}
 159
 160/*
 161 * Close the old accounting file (if currently open) and then replace
 162 * it with file (if non-NULL).
 163 *
 164 * NOTE: acct_lock MUST be held on entry and exit.
 165 */
 166static void acct_file_reopen(struct bsd_acct_struct *acct, struct file *file,
 167                struct pid_namespace *ns)
 168{
 169        struct file *old_acct = NULL;
 170        struct pid_namespace *old_ns = NULL;
 171
 172        if (acct->file) {
 173                old_acct = acct->file;
 174                old_ns = acct->ns;
 175                acct->active = 0;
 176                acct->file = NULL;
 177                acct->ns = NULL;
 178                list_del(&acct->list);
 179        }
 180        if (file) {
 181                acct->file = file;
 182                acct->ns = ns;
 183                acct->needcheck = jiffies + ACCT_TIMEOUT*HZ;
 184                acct->active = 1;
 185                list_add(&acct->list, &acct_list);
 186        }
 187        if (old_acct) {
 188                mnt_unpin(old_acct->f_path.mnt);
 189                spin_unlock(&acct_lock);
 190                do_acct_process(acct, old_ns, old_acct);
 191                filp_close(old_acct, NULL);
 192                spin_lock(&acct_lock);
 193        }
 194}
 195
 196static int acct_on(char *name)
 197{
 198        struct file *file;
 199        struct vfsmount *mnt;
 200        struct pid_namespace *ns;
 201        struct bsd_acct_struct *acct = NULL;
 202
 203        /* Difference from BSD - they don't do O_APPEND */
 204        file = filp_open(name, O_WRONLY|O_APPEND|O_LARGEFILE, 0);
 205        if (IS_ERR(file))
 206                return PTR_ERR(file);
 207
 208        if (!S_ISREG(file->f_path.dentry->d_inode->i_mode)) {
 209                filp_close(file, NULL);
 210                return -EACCES;
 211        }
 212
 213        if (!file->f_op->write) {
 214                filp_close(file, NULL);
 215                return -EIO;
 216        }
 217
 218        ns = task_active_pid_ns(current);
 219        if (ns->bacct == NULL) {
 220                acct = kzalloc(sizeof(struct bsd_acct_struct), GFP_KERNEL);
 221                if (acct == NULL) {
 222                        filp_close(file, NULL);
 223                        return -ENOMEM;
 224                }
 225        }
 226
 227        spin_lock(&acct_lock);
 228        if (ns->bacct == NULL) {
 229                ns->bacct = acct;
 230                acct = NULL;
 231        }
 232
 233        mnt = file->f_path.mnt;
 234        mnt_pin(mnt);
 235        acct_file_reopen(ns->bacct, file, ns);
 236        spin_unlock(&acct_lock);
 237
 238        mntput(mnt); /* it's pinned, now give up active reference */
 239        kfree(acct);
 240
 241        return 0;
 242}
 243
 244/**
 245 * sys_acct - enable/disable process accounting
 246 * @name: file name for accounting records or NULL to shutdown accounting
 247 *
 248 * Returns 0 for success or negative errno values for failure.
 249 *
 250 * sys_acct() is the only system call needed to implement process
 251 * accounting. It takes the name of the file where accounting records
 252 * should be written. If the filename is NULL, accounting will be
 253 * shutdown.
 254 */
 255SYSCALL_DEFINE1(acct, const char __user *, name)
 256{
 257        int error = 0;
 258
 259        if (!capable(CAP_SYS_PACCT))
 260                return -EPERM;
 261
 262        if (name) {
 263                char *tmp = getname(name);
 264                if (IS_ERR(tmp))
 265                        return (PTR_ERR(tmp));
 266                error = acct_on(tmp);
 267                putname(tmp);
 268        } else {
 269                struct bsd_acct_struct *acct;
 270
 271                acct = task_active_pid_ns(current)->bacct;
 272                if (acct == NULL)
 273                        return 0;
 274
 275                spin_lock(&acct_lock);
 276                acct_file_reopen(acct, NULL, NULL);
 277                spin_unlock(&acct_lock);
 278        }
 279
 280        return error;
 281}
 282
 283/**
 284 * acct_auto_close - turn off a filesystem's accounting if it is on
 285 * @m: vfsmount being shut down
 286 *
 287 * If the accounting is turned on for a file in the subtree pointed to
 288 * to by m, turn accounting off.  Done when m is about to die.
 289 */
 290void acct_auto_close_mnt(struct vfsmount *m)
 291{
 292        struct bsd_acct_struct *acct;
 293
 294        spin_lock(&acct_lock);
 295restart:
 296        list_for_each_entry(acct, &acct_list, list)
 297                if (acct->file && acct->file->f_path.mnt == m) {
 298                        acct_file_reopen(acct, NULL, NULL);
 299                        goto restart;
 300                }
 301        spin_unlock(&acct_lock);
 302}
 303
 304/**
 305 * acct_auto_close - turn off a filesystem's accounting if it is on
 306 * @sb: super block for the filesystem
 307 *
 308 * If the accounting is turned on for a file in the filesystem pointed
 309 * to by sb, turn accounting off.
 310 */
 311void acct_auto_close(struct super_block *sb)
 312{
 313        struct bsd_acct_struct *acct;
 314
 315        spin_lock(&acct_lock);
 316restart:
 317        list_for_each_entry(acct, &acct_list, list)
 318                if (acct->file && acct->file->f_path.dentry->d_sb == sb) {
 319                        acct_file_reopen(acct, NULL, NULL);
 320                        goto restart;
 321                }
 322        spin_unlock(&acct_lock);
 323}
 324
 325void acct_exit_ns(struct pid_namespace *ns)
 326{
 327        struct bsd_acct_struct *acct = ns->bacct;
 328
 329        if (acct == NULL)
 330                return;
 331
 332        spin_lock(&acct_lock);
 333        if (acct->file != NULL)
 334                acct_file_reopen(acct, NULL, NULL);
 335        spin_unlock(&acct_lock);
 336
 337        kfree(acct);
 338}
 339
 340/*
 341 *  encode an unsigned long into a comp_t
 342 *
 343 *  This routine has been adopted from the encode_comp_t() function in
 344 *  the kern_acct.c file of the FreeBSD operating system. The encoding
 345 *  is a 13-bit fraction with a 3-bit (base 8) exponent.
 346 */
 347
 348#define MANTSIZE        13                      /* 13 bit mantissa. */
 349#define EXPSIZE         3                       /* Base 8 (3 bit) exponent. */
 350#define MAXFRACT        ((1 << MANTSIZE) - 1)   /* Maximum fractional value. */
 351
 352static comp_t encode_comp_t(unsigned long value)
 353{
 354        int exp, rnd;
 355
 356        exp = rnd = 0;
 357        while (value > MAXFRACT) {
 358                rnd = value & (1 << (EXPSIZE - 1));     /* Round up? */
 359                value >>= EXPSIZE;      /* Base 8 exponent == 3 bit shift. */
 360                exp++;
 361        }
 362
 363        /*
 364         * If we need to round up, do it (and handle overflow correctly).
 365         */
 366        if (rnd && (++value > MAXFRACT)) {
 367                value >>= EXPSIZE;
 368                exp++;
 369        }
 370
 371        /*
 372         * Clean it up and polish it off.
 373         */
 374        exp <<= MANTSIZE;               /* Shift the exponent into place */
 375        exp += value;                   /* and add on the mantissa. */
 376        return exp;
 377}
 378
 379#if ACCT_VERSION==1 || ACCT_VERSION==2
 380/*
 381 * encode an u64 into a comp2_t (24 bits)
 382 *
 383 * Format: 5 bit base 2 exponent, 20 bits mantissa.
 384 * The leading bit of the mantissa is not stored, but implied for
 385 * non-zero exponents.
 386 * Largest encodable value is 50 bits.
 387 */
 388
 389#define MANTSIZE2       20                      /* 20 bit mantissa. */
 390#define EXPSIZE2        5                       /* 5 bit base 2 exponent. */
 391#define MAXFRACT2       ((1ul << MANTSIZE2) - 1) /* Maximum fractional value. */
 392#define MAXEXP2         ((1 <<EXPSIZE2) - 1)    /* Maximum exponent. */
 393
 394static comp2_t encode_comp2_t(u64 value)
 395{
 396        int exp, rnd;
 397
 398        exp = (value > (MAXFRACT2>>1));
 399        rnd = 0;
 400        while (value > MAXFRACT2) {
 401                rnd = value & 1;
 402                value >>= 1;
 403                exp++;
 404        }
 405
 406        /*
 407         * If we need to round up, do it (and handle overflow correctly).
 408         */
 409        if (rnd && (++value > MAXFRACT2)) {
 410                value >>= 1;
 411                exp++;
 412        }
 413
 414        if (exp > MAXEXP2) {
 415                /* Overflow. Return largest representable number instead. */
 416                return (1ul << (MANTSIZE2+EXPSIZE2-1)) - 1;
 417        } else {
 418                return (value & (MAXFRACT2>>1)) | (exp << (MANTSIZE2-1));
 419        }
 420}
 421#endif
 422
 423#if ACCT_VERSION==3
 424/*
 425 * encode an u64 into a 32 bit IEEE float
 426 */
 427static u32 encode_float(u64 value)
 428{
 429        unsigned exp = 190;
 430        unsigned u;
 431
 432        if (value==0) return 0;
 433        while ((s64)value > 0){
 434                value <<= 1;
 435                exp--;
 436        }
 437        u = (u32)(value >> 40) & 0x7fffffu;
 438        return u | (exp << 23);
 439}
 440#endif
 441
 442/*
 443 *  Write an accounting entry for an exiting process
 444 *
 445 *  The acct_process() call is the workhorse of the process
 446 *  accounting system. The struct acct is built here and then written
 447 *  into the accounting file. This function should only be called from
 448 *  do_exit() or when switching to a different output file.
 449 */
 450
 451/*
 452 *  do_acct_process does all actual work. Caller holds the reference to file.
 453 */
 454static void do_acct_process(struct bsd_acct_struct *acct,
 455                struct pid_namespace *ns, struct file *file)
 456{
 457        struct pacct_struct *pacct = &current->signal->pacct;
 458        acct_t ac;
 459        mm_segment_t fs;
 460        unsigned long flim;
 461        u64 elapsed;
 462        u64 run_time;
 463        struct timespec uptime;
 464        struct tty_struct *tty;
 465        const struct cred *orig_cred;
 466
 467        /* Perform file operations on behalf of whoever enabled accounting */
 468        orig_cred = override_creds(file->f_cred);
 469
 470        /*
 471         * First check to see if there is enough free_space to continue
 472         * the process accounting system.
 473         */
 474        if (!check_free_space(acct, file))
 475                goto out;
 476
 477        /*
 478         * Fill the accounting struct with the needed info as recorded
 479         * by the different kernel functions.
 480         */
 481        memset(&ac, 0, sizeof(acct_t));
 482
 483        ac.ac_version = ACCT_VERSION | ACCT_BYTEORDER;
 484        strlcpy(ac.ac_comm, current->comm, sizeof(ac.ac_comm));
 485
 486        /* calculate run_time in nsec*/
 487        do_posix_clock_monotonic_gettime(&uptime);
 488        run_time = (u64)uptime.tv_sec*NSEC_PER_SEC + uptime.tv_nsec;
 489        run_time -= (u64)current->group_leader->start_time.tv_sec * NSEC_PER_SEC
 490                       + current->group_leader->start_time.tv_nsec;
 491        /* convert nsec -> AHZ */
 492        elapsed = nsec_to_AHZ(run_time);
 493#if ACCT_VERSION==3
 494        ac.ac_etime = encode_float(elapsed);
 495#else
 496        ac.ac_etime = encode_comp_t(elapsed < (unsigned long) -1l ?
 497                               (unsigned long) elapsed : (unsigned long) -1l);
 498#endif
 499#if ACCT_VERSION==1 || ACCT_VERSION==2
 500        {
 501                /* new enlarged etime field */
 502                comp2_t etime = encode_comp2_t(elapsed);
 503                ac.ac_etime_hi = etime >> 16;
 504                ac.ac_etime_lo = (u16) etime;
 505        }
 506#endif
 507        do_div(elapsed, AHZ);
 508        ac.ac_btime = get_seconds() - elapsed;
 509        /* we really need to bite the bullet and change layout */
 510        ac.ac_uid = orig_cred->uid;
 511        ac.ac_gid = orig_cred->gid;
 512#if ACCT_VERSION==2
 513        ac.ac_ahz = AHZ;
 514#endif
 515#if ACCT_VERSION==1 || ACCT_VERSION==2
 516        /* backward-compatible 16 bit fields */
 517        ac.ac_uid16 = ac.ac_uid;
 518        ac.ac_gid16 = ac.ac_gid;
 519#endif
 520#if ACCT_VERSION==3
 521        ac.ac_pid = task_tgid_nr_ns(current, ns);
 522        rcu_read_lock();
 523        ac.ac_ppid = task_tgid_nr_ns(rcu_dereference(current->real_parent), ns);
 524        rcu_read_unlock();
 525#endif
 526
 527        spin_lock_irq(&current->sighand->siglock);
 528        tty = current->signal->tty;     /* Safe as we hold the siglock */
 529        ac.ac_tty = tty ? old_encode_dev(tty_devnum(tty)) : 0;
 530        ac.ac_utime = encode_comp_t(jiffies_to_AHZ(cputime_to_jiffies(pacct->ac_utime)));
 531        ac.ac_stime = encode_comp_t(jiffies_to_AHZ(cputime_to_jiffies(pacct->ac_stime)));
 532        ac.ac_flag = pacct->ac_flag;
 533        ac.ac_mem = encode_comp_t(pacct->ac_mem);
 534        ac.ac_minflt = encode_comp_t(pacct->ac_minflt);
 535        ac.ac_majflt = encode_comp_t(pacct->ac_majflt);
 536        ac.ac_exitcode = pacct->ac_exitcode;
 537        spin_unlock_irq(&current->sighand->siglock);
 538        ac.ac_io = encode_comp_t(0 /* current->io_usage */);    /* %% */
 539        ac.ac_rw = encode_comp_t(ac.ac_io / 1024);
 540        ac.ac_swaps = encode_comp_t(0);
 541
 542        /*
 543         * Kernel segment override to datasegment and write it
 544         * to the accounting file.
 545         */
 546        fs = get_fs();
 547        set_fs(KERNEL_DS);
 548        /*
 549         * Accounting records are not subject to resource limits.
 550         */
 551        flim = current->signal->rlim[RLIMIT_FSIZE].rlim_cur;
 552        current->signal->rlim[RLIMIT_FSIZE].rlim_cur = RLIM_INFINITY;
 553        file->f_op->write(file, (char *)&ac,
 554                               sizeof(acct_t), &file->f_pos);
 555        current->signal->rlim[RLIMIT_FSIZE].rlim_cur = flim;
 556        set_fs(fs);
 557out:
 558        revert_creds(orig_cred);
 559}
 560
 561/**
 562 * acct_collect - collect accounting information into pacct_struct
 563 * @exitcode: task exit code
 564 * @group_dead: not 0, if this thread is the last one in the process.
 565 */
 566void acct_collect(long exitcode, int group_dead)
 567{
 568        struct pacct_struct *pacct = &current->signal->pacct;
 569        unsigned long vsize = 0;
 570
 571        if (group_dead && current->mm) {
 572                struct vm_area_struct *vma;
 573                down_read(&current->mm->mmap_sem);
 574                vma = current->mm->mmap;
 575                while (vma) {
 576                        vsize += vma->vm_end - vma->vm_start;
 577                        vma = vma->vm_next;
 578                }
 579                up_read(&current->mm->mmap_sem);
 580        }
 581
 582        spin_lock_irq(&current->sighand->siglock);
 583        if (group_dead)
 584                pacct->ac_mem = vsize / 1024;
 585        if (thread_group_leader(current)) {
 586                pacct->ac_exitcode = exitcode;
 587                if (current->flags & PF_FORKNOEXEC)
 588                        pacct->ac_flag |= AFORK;
 589        }
 590        if (current->flags & PF_SUPERPRIV)
 591                pacct->ac_flag |= ASU;
 592        if (current->flags & PF_DUMPCORE)
 593                pacct->ac_flag |= ACORE;
 594        if (current->flags & PF_SIGNALED)
 595                pacct->ac_flag |= AXSIG;
 596        pacct->ac_utime += current->utime;
 597        pacct->ac_stime += current->stime;
 598        pacct->ac_minflt += current->min_flt;
 599        pacct->ac_majflt += current->maj_flt;
 600        spin_unlock_irq(&current->sighand->siglock);
 601}
 602
 603static void acct_process_in_ns(struct pid_namespace *ns)
 604{
 605        struct file *file = NULL;
 606        struct bsd_acct_struct *acct;
 607
 608        acct = ns->bacct;
 609        /*
 610         * accelerate the common fastpath:
 611         */
 612        if (!acct || !acct->file)
 613                return;
 614
 615        spin_lock(&acct_lock);
 616        file = acct->file;
 617        if (unlikely(!file)) {
 618                spin_unlock(&acct_lock);
 619                return;
 620        }
 621        get_file(file);
 622        spin_unlock(&acct_lock);
 623
 624        do_acct_process(acct, ns, file);
 625        fput(file);
 626}
 627
 628/**
 629 * acct_process - now just a wrapper around acct_process_in_ns,
 630 * which in turn is a wrapper around do_acct_process.
 631 *
 632 * handles process accounting for an exiting task
 633 */
 634void acct_process(void)
 635{
 636        struct pid_namespace *ns;
 637
 638        /*
 639         * This loop is safe lockless, since current is still
 640         * alive and holds its namespace, which in turn holds
 641         * its parent.
 642         */
 643        for (ns = task_active_pid_ns(current); ns != NULL; ns = ns->parent)
 644                acct_process_in_ns(ns);
 645}
 646
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