kernel/acct.c

   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/config.h>
  47 #include <linux/mm.h>
  48 #include <linux/slab.h>
  49 #include <linux/acct.h>
  50 #include <linux/capability.h>
  51 #include <linux/file.h>
  52 #include <linux/tty.h>
  53 #include <linux/security.h>
  54 #include <linux/vfs.h>
  55 #include <linux/jiffies.h>
  56 #include <linux/times.h>
  57 #include <linux/syscalls.h>
  58 #include <linux/mount.h>
  59 #include <asm/uaccess.h>
  60 #include <asm/div64.h>
  61 #include <linux/blkdev.h> /* sector_div */
  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
  70 int 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  */
  78 static void do_acct_process(long, struct file *);
  79
  80 /*
  81  * This structure is used so that all the data protected by lock
  82  * can be placed in the same cache line as the lock.  This primes
  83  * the cache line to have the data after getting the lock.
  84  */
  85 struct acct_glbs {
  86         spinlock_t              lock;
  87         volatile int            active;
  88         volatile int            needcheck;
  89         struct file             *file;
  90         struct timer_list       timer;
  91 };
  92
  93 static struct acct_glbs acct_globals __cacheline_aligned = {SPIN_LOCK_UNLOCKED};
  94
  95 /*
  96  * Called whenever the timer says to check the free space.
  97  */
  98 static void acct_timeout(unsigned long unused)
  99 {
 100         acct_globals.needcheck = 1;
 101 }
 102
 103 /*
 104  * Check the amount of free space and suspend/resume accordingly.
 105  */
 106 static int check_free_space(struct file *file)
 107 {
 108         struct kstatfs sbuf;
 109         int res;
 110         int act;
 111         sector_t resume;
 112         sector_t suspend;
 113
 114         spin_lock(&acct_globals.lock);
 115         res = acct_globals.active;
 116         if (!file || !acct_globals.needcheck)
 117                 goto out;
 118         spin_unlock(&acct_globals.lock);
 119
 120         /* May block */
 121         if (vfs_statfs(file->f_dentry->d_inode->i_sb, &sbuf))
 122                 return res;
 123         suspend = sbuf.f_blocks * SUSPEND;
 124         resume = sbuf.f_blocks * RESUME;
 125
 126         sector_div(suspend, 100);
 127         sector_div(resume, 100);
 128
 129         if (sbuf.f_bavail <= suspend)
 130                 act = -1;
 131         else if (sbuf.f_bavail >= resume)
 132                 act = 1;
 133         else
 134                 act = 0;
 135
 136         /*
 137          * If some joker switched acct_globals.file under us we'ld better be
 138          * silent and _not_ touch anything.
 139          */
 140         spin_lock(&acct_globals.lock);
 141         if (file != acct_globals.file) {
 142                 if (act)
 143                         res = act>0;
 144                 goto out;
 145         }
 146
 147         if (acct_globals.active) {
 148                 if (act < 0) {
 149                         acct_globals.active = 0;
 150                         printk(KERN_INFO "Process accounting paused\n");
 151                 }
 152         } else {
 153                 if (act > 0) {
 154                         acct_globals.active = 1;
 155                         printk(KERN_INFO "Process accounting resumed\n");
 156                 }
 157         }
 158
 159         del_timer(&acct_globals.timer);
 160         acct_globals.needcheck = 0;
 161         acct_globals.timer.expires = jiffies + ACCT_TIMEOUT*HZ;
 162         add_timer(&acct_globals.timer);
 163         res = acct_globals.active;
 164 out:
 165         spin_unlock(&acct_globals.lock);
 166         return res;
 167 }
 168
 169 /*
 170  * Close the old accounting file (if currently open) and then replace
 171  * it with file (if non-NULL).
 172  *
 173  * NOTE: acct_globals.lock MUST be held on entry and exit.
 174  */
 175 static void acct_file_reopen(struct file *file)
 176 {
 177         struct file *old_acct = NULL;
 178
 179         if (acct_globals.file) {
 180                 old_acct = acct_globals.file;
 181                 del_timer(&acct_globals.timer);
 182                 acct_globals.active = 0;
 183                 acct_globals.needcheck = 0;
 184                 acct_globals.file = NULL;
 185         }
 186         if (file) {
 187                 acct_globals.file = file;
 188                 acct_globals.needcheck = 0;
 189                 acct_globals.active = 1;
 190                 /* It's been deleted if it was used before so this is safe */
 191                 init_timer(&acct_globals.timer);
 192                 acct_globals.timer.function = acct_timeout;
 193                 acct_globals.timer.expires = jiffies + ACCT_TIMEOUT*HZ;
 194                 add_timer(&acct_globals.timer);
 195         }
 196         if (old_acct) {
 197                 mnt_unpin(old_acct->f_vfsmnt);
 198                 spin_unlock(&acct_globals.lock);
 199                 do_acct_process(0, old_acct);
 200                 filp_close(old_acct, NULL);
 201                 spin_lock(&acct_globals.lock);
 202         }
 203 }
 204
 205 static int acct_on(char *name)
 206 {
 207         struct file *file;
 208         int error;
 209
 210         /* Difference from BSD - they don't do O_APPEND */
 211         file = filp_open(name, O_WRONLY|O_APPEND|O_LARGEFILE, 0);
 212         if (IS_ERR(file))
 213                 return PTR_ERR(file);
 214
 215         if (!S_ISREG(file->f_dentry->d_inode->i_mode)) {
 216                 filp_close(file, NULL);
 217                 return -EACCES;
 218         }
 219
 220         if (!file->f_op->write) {
 221                 filp_close(file, NULL);
 222                 return -EIO;
 223         }
 224
 225         error = security_acct(file);
 226         if (error) {
 227                 filp_close(file, NULL);
 228                 return error;
 229         }
 230
 231         spin_lock(&acct_globals.lock);
 232         mnt_pin(file->f_vfsmnt);
 233         acct_file_reopen(file);
 234         spin_unlock(&acct_globals.lock);
 235
 236         mntput(file->f_vfsmnt); /* it's pinned, now give up active reference */
 237
 238         return 0;
 239 }
 240
 241 /**
 242  * sys_acct - enable/disable process accounting
 243  * @name: file name for accounting records or NULL to shutdown accounting
 244  *
 245  * Returns 0 for success or negative errno values for failure.
 246  *
 247  * sys_acct() is the only system call needed to implement process
 248  * accounting. It takes the name of the file where accounting records
 249  * should be written. If the filename is NULL, accounting will be
 250  * shutdown.
 251  */
 252 asmlinkage long sys_acct(const char __user *name)
 253 {
 254         int error;
 255
 256         if (!capable(CAP_SYS_PACCT))
 257                 return -EPERM;
 258
 259         if (name) {
 260                 char *tmp = getname(name);
 261                 if (IS_ERR(tmp))
 262                         return (PTR_ERR(tmp));
 263                 error = acct_on(tmp);
 264                 putname(tmp);
 265         } else {
 266                 error = security_acct(NULL);
 267                 if (!error) {
 268                         spin_lock(&acct_globals.lock);
 269                         acct_file_reopen(NULL);
 270                         spin_unlock(&acct_globals.lock);
 271                 }
 272         }
 273         return error;
 274 }
 275
 276 /**
 277  * acct_auto_close - turn off a filesystem's accounting if it is on
 278  * @m: vfsmount being shut down
 279  *
 280  * If the accounting is turned on for a file in the subtree pointed to
 281  * to by m, turn accounting off.  Done when m is about to die.
 282  */
 283 void acct_auto_close_mnt(struct vfsmount *m)
 284 {
 285         spin_lock(&acct_globals.lock);
 286         if (acct_globals.file && acct_globals.file->f_vfsmnt == m)
 287                 acct_file_reopen(NULL);
 288         spin_unlock(&acct_globals.lock);
 289 }
 290
 291 /**
 292  * acct_auto_close - turn off a filesystem's accounting if it is on
 293  * @sb: super block for the filesystem
 294  *
 295  * If the accounting is turned on for a file in the filesystem pointed
 296  * to by sb, turn accounting off.
 297  */
 298 void acct_auto_close(struct super_block *sb)
 299 {
 300         spin_lock(&acct_globals.lock);
 301         if (acct_globals.file &&
 302             acct_globals.file->f_vfsmnt->mnt_sb == sb) {
 303                 acct_file_reopen(NULL);
 304         }
 305         spin_unlock(&acct_globals.lock);
 306 }
 307
 308 /*
 309  *  encode an unsigned long into a comp_t
 310  *
 311  *  This routine has been adopted from the encode_comp_t() function in
 312  *  the kern_acct.c file of the FreeBSD operating system. The encoding
 313  *  is a 13-bit fraction with a 3-bit (base 8) exponent.
 314  */
 315
 316 #define MANTSIZE        13                      /* 13 bit mantissa. */
 317 #define EXPSIZE         3                       /* Base 8 (3 bit) exponent. */
 318 #define MAXFRACT        ((1 << MANTSIZE) - 1)   /* Maximum fractional value. */
 319
 320 static comp_t encode_comp_t(unsigned long value)
 321 {
 322         int exp, rnd;
 323
 324         exp = rnd = 0;
 325         while (value > MAXFRACT) {
 326                 rnd = value & (1 << (EXPSIZE - 1));     /* Round up? */
 327                 value >>= EXPSIZE;      /* Base 8 exponent == 3 bit shift. */
 328                 exp++;
 329         }
 330
 331         /*
 332          * If we need to round up, do it (and handle overflow correctly).
 333          */
 334         if (rnd && (++value > MAXFRACT)) {
 335                 value >>= EXPSIZE;
 336                 exp++;
 337         }
 338
 339         /*
 340          * Clean it up and polish it off.
 341          */
 342         exp <<= MANTSIZE;               /* Shift the exponent into place */
 343         exp += value;                   /* and add on the mantissa. */
 344         return exp;
 345 }
 346
 347 #if ACCT_VERSION==1 || ACCT_VERSION==2
 348 /*
 349  * encode an u64 into a comp2_t (24 bits)
 350  *
 351  * Format: 5 bit base 2 exponent, 20 bits mantissa.
 352  * The leading bit of the mantissa is not stored, but implied for
 353  * non-zero exponents.
 354  * Largest encodable value is 50 bits.
 355  */
 356
 357 #define MANTSIZE2       20                      /* 20 bit mantissa. */
 358 #define EXPSIZE2        5                       /* 5 bit base 2 exponent. */
 359 #define MAXFRACT2       ((1ul << MANTSIZE2) - 1) /* Maximum fractional value. */
 360 #define MAXEXP2         ((1 <<EXPSIZE2) - 1)    /* Maximum exponent. */
 361
 362 static comp2_t encode_comp2_t(u64 value)
 363 {
 364         int exp, rnd;
 365
 366         exp = (value > (MAXFRACT2>>1));
 367         rnd = 0;
 368         while (value > MAXFRACT2) {
 369                 rnd = value & 1;
 370                 value >>= 1;
 371                 exp++;
 372         }
 373
 374         /*
 375          * If we need to round up, do it (and handle overflow correctly).
 376          */
 377         if (rnd && (++value > MAXFRACT2)) {
 378                 value >>= 1;
 379                 exp++;
 380         }
 381
 382         if (exp > MAXEXP2) {
 383                 /* Overflow. Return largest representable number instead. */
 384                 return (1ul << (MANTSIZE2+EXPSIZE2-1)) - 1;
 385         } else {
 386                 return (value & (MAXFRACT2>>1)) | (exp << (MANTSIZE2-1));
 387         }
 388 }
 389 #endif
 390
 391 #if ACCT_VERSION==3
 392 /*
 393  * encode an u64 into a 32 bit IEEE float
 394  */
 395 static u32 encode_float(u64 value)
 396 {
 397         unsigned exp = 190;
 398         unsigned u;
 399
 400         if (value==0) return 0;
 401         while ((s64)value > 0){
 402                 value <<= 1;
 403                 exp--;
 404         }
 405         u = (u32)(value >> 40) & 0x7fffffu;
 406         return u | (exp << 23);
 407 }
 408 #endif
 409
 410 /*
 411  *  Write an accounting entry for an exiting process
 412  *
 413  *  The acct_process() call is the workhorse of the process
 414  *  accounting system. The struct acct is built here and then written
 415  *  into the accounting file. This function should only be called from
 416  *  do_exit().
 417  */
 418
 419 /*
 420  *  do_acct_process does all actual work. Caller holds the reference to file.
 421  */
 422 static void do_acct_process(long exitcode, struct file *file)
 423 {
 424         acct_t ac;
 425         mm_segment_t fs;
 426         unsigned long vsize;
 427         unsigned long flim;
 428         u64 elapsed;
 429         u64 run_time;
 430         struct timespec uptime;
 431         unsigned long jiffies;
 432
 433         /*
 434          * First check to see if there is enough free_space to continue
 435          * the process accounting system.
 436          */
 437         if (!check_free_space(file))
 438                 return;
 439
 440         /*
 441          * Fill the accounting struct with the needed info as recorded
 442          * by the different kernel functions.
 443          */
 444         memset((caddr_t)&ac, 0, sizeof(acct_t));
 445
 446         ac.ac_version = ACCT_VERSION | ACCT_BYTEORDER;
 447         strlcpy(ac.ac_comm, current->comm, sizeof(ac.ac_comm));
 448
 449         /* calculate run_time in nsec*/
 450         do_posix_clock_monotonic_gettime(&uptime);
 451         run_time = (u64)uptime.tv_sec*NSEC_PER_SEC + uptime.tv_nsec;
 452         run_time -= (u64)current->start_time.tv_sec*NSEC_PER_SEC
 453                                         + current->start_time.tv_nsec;
 454         /* convert nsec -> AHZ */
 455         elapsed = nsec_to_AHZ(run_time);
 456 #if ACCT_VERSION==3
 457         ac.ac_etime = encode_float(elapsed);
 458 #else
 459         ac.ac_etime = encode_comp_t(elapsed < (unsigned long) -1l ?
 460                                (unsigned long) elapsed : (unsigned long) -1l);
 461 #endif
 462 #if ACCT_VERSION==1 || ACCT_VERSION==2
 463         {
 464                 /* new enlarged etime field */
 465                 comp2_t etime = encode_comp2_t(elapsed);
 466                 ac.ac_etime_hi = etime >> 16;
 467                 ac.ac_etime_lo = (u16) etime;
 468         }
 469 #endif
 470         do_div(elapsed, AHZ);
 471         ac.ac_btime = xtime.tv_sec - elapsed;
 472         jiffies = cputime_to_jiffies(cputime_add(current->group_leader->utime,
 473                                                  current->signal->utime));
 474         ac.ac_utime = encode_comp_t(jiffies_to_AHZ(jiffies));
 475         jiffies = cputime_to_jiffies(cputime_add(current->group_leader->stime,
 476                                                  current->signal->stime));
 477         ac.ac_stime = encode_comp_t(jiffies_to_AHZ(jiffies));
 478         /* we really need to bite the bullet and change layout */
 479         ac.ac_uid = current->uid;
 480         ac.ac_gid = current->gid;
 481 #if ACCT_VERSION==2
 482         ac.ac_ahz = AHZ;
 483 #endif
 484 #if ACCT_VERSION==1 || ACCT_VERSION==2
 485         /* backward-compatible 16 bit fields */
 486         ac.ac_uid16 = current->uid;
 487         ac.ac_gid16 = current->gid;
 488 #endif
 489 #if ACCT_VERSION==3
 490         ac.ac_pid = current->tgid;
 491         ac.ac_ppid = current->parent->tgid;
 492 #endif
 493
 494         read_lock(&tasklist_lock);      /* pin current->signal */
 495         ac.ac_tty = current->signal->tty ?
 496                 old_encode_dev(tty_devnum(current->signal->tty)) : 0;
 497         read_unlock(&tasklist_lock);
 498
 499         ac.ac_flag = 0;
 500         if (current->flags & PF_FORKNOEXEC)
 501                 ac.ac_flag |= AFORK;
 502         if (current->flags & PF_SUPERPRIV)
 503                 ac.ac_flag |= ASU;
 504         if (current->flags & PF_DUMPCORE)
 505                 ac.ac_flag |= ACORE;
 506         if (current->flags & PF_SIGNALED)
 507                 ac.ac_flag |= AXSIG;
 508
 509         vsize = 0;
 510         if (current->mm) {
 511                 struct vm_area_struct *vma;
 512                 down_read(&current->mm->mmap_sem);
 513                 vma = current->mm->mmap;
 514                 while (vma) {
 515                         vsize += vma->vm_end - vma->vm_start;
 516                         vma = vma->vm_next;
 517                 }
 518                 up_read(&current->mm->mmap_sem);
 519         }
 520         vsize = vsize / 1024;
 521         ac.ac_mem = encode_comp_t(vsize);
 522         ac.ac_io = encode_comp_t(0 /* current->io_usage */);    /* %% */
 523         ac.ac_rw = encode_comp_t(ac.ac_io / 1024);
 524         ac.ac_minflt = encode_comp_t(current->signal->min_flt +
 525                                      current->group_leader->min_flt);
 526         ac.ac_majflt = encode_comp_t(current->signal->maj_flt +
 527                                      current->group_leader->maj_flt);
 528         ac.ac_swaps = encode_comp_t(0);
 529         ac.ac_exitcode = exitcode;
 530
 531         /*
 532          * Kernel segment override to datasegment and write it
 533          * to the accounting file.
 534          */
 535         fs = get_fs();
 536         set_fs(KERNEL_DS);
 537         /*
 538          * Accounting records are not subject to resource limits.
 539          */
 540         flim = current->signal->rlim[RLIMIT_FSIZE].rlim_cur;
 541         current->signal->rlim[RLIMIT_FSIZE].rlim_cur = RLIM_INFINITY;
 542         file->f_op->write(file, (char *)&ac,
 543                                sizeof(acct_t), &file->f_pos);
 544         current->signal->rlim[RLIMIT_FSIZE].rlim_cur = flim;
 545         set_fs(fs);
 546 }
 547
 548 /**
 549  * acct_process - now just a wrapper around do_acct_process
 550  * @exitcode: task exit code
 551  *
 552  * handles process accounting for an exiting task
 553  */
 554 void acct_process(long exitcode)
 555 {
 556         struct file *file = NULL;
 557
 558         /*
 559          * accelerate the common fastpath:
 560          */
 561         if (!acct_globals.file)
 562                 return;
 563
 564         spin_lock(&acct_globals.lock);
 565         file = acct_globals.file;
 566         if (unlikely(!file)) {
 567                 spin_unlock(&acct_globals.lock);
 568                 return;
 569         }
 570         get_file(file);
 571         spin_unlock(&acct_globals.lock);
 572
 573         do_acct_process(exitcode, file);
 574         fput(file);
 575 }
 576
 577
 578 /**
 579  * acct_update_integrals - update mm integral fields in task_struct
 580  * @tsk: task_struct for accounting
 581  */
 582 void acct_update_integrals(struct task_struct *tsk)
 583 {
 584         if (likely(tsk->mm)) {
 585                 long delta =
 586                         cputime_to_jiffies(tsk->stime) - tsk->acct_stimexpd;
 587
 588                 if (delta == 0)
 589                         return;
 590                 tsk->acct_stimexpd = tsk->stime;
 591                 tsk->acct_rss_mem1 += delta * get_mm_rss(tsk->mm);
 592                 tsk->acct_vm_mem1 += delta * tsk->mm->total_vm;
 593         }
 594 }
 595
 596 /**
 597  * acct_clear_integrals - clear the mm integral fields in task_struct
 598  * @tsk: task_struct whose accounting fields are cleared
 599  */
 600 void acct_clear_integrals(struct task_struct *tsk)
 601 {
 602         if (tsk) {
 603                 tsk->acct_stimexpd = 0;
 604                 tsk->acct_rss_mem1 = 0;
 605                 tsk->acct_vm_mem1 = 0;
 606         }
 607 }