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 62 /* 63 * These constants control the amount of freespace that suspend and 64 * resume the process accounting system, and the time delay between 65 * each check. 66 * Turned into sysctl-controllable parameters. AV, 12/11/98 67 */ 68 69 int acct_parm[3] = {4, 2, 30}; 70 #define RESUME (acct_parm[0]) /* >foo% free space - resume */ 71 #define SUSPEND (acct_parm[1]) /* <foo% free space - suspend */ 72 #define ACCT_TIMEOUT (acct_parm[2]) /* foo second timeout between checks */ 73 74 /* 75 * External references and all of the globals. 76 */ 77 static void do_acct_process(struct file *); 78 79 /* 80 * This structure is used so that all the data protected by lock 81 * can be placed in the same cache line as the lock. This primes 82 * the cache line to have the data after getting the lock. 83 */ 84 struct acct_glbs { 85 spinlock_t lock; 86 volatile int active; 87 volatile int needcheck; 88 struct file *file; 89 struct timer_list timer; 90 }; 91 92 static struct acct_glbs acct_globals __cacheline_aligned = 93 {__SPIN_LOCK_UNLOCKED(acct_globals.lock)}; 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_path.dentry, &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_path.mnt); 198 spin_unlock(&acct_globals.lock); 199 do_acct_process(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_path.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_path.mnt); 233 acct_file_reopen(file); 234 spin_unlock(&acct_globals.lock); 235 236 mntput(file->f_path.mnt); /* 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_path.mnt == 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_path.mnt->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(struct file *file) 423 { 424 struct pacct_struct *pacct = ¤t->signal->pacct; 425 acct_t ac; 426 mm_segment_t fs; 427 unsigned long flim; 428 u64 elapsed; 429 u64 run_time; 430 struct timespec uptime; 431 struct tty_struct *tty; 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->group_leader->start_time.tv_sec * NSEC_PER_SEC 453 + current->group_leader->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 /* we really need to bite the bullet and change layout */ 473 ac.ac_uid = current->uid; 474 ac.ac_gid = current->gid; 475 #if ACCT_VERSION==2 476 ac.ac_ahz = AHZ; 477 #endif 478 #if ACCT_VERSION==1 || ACCT_VERSION==2 479 /* backward-compatible 16 bit fields */ 480 ac.ac_uid16 = current->uid; 481 ac.ac_gid16 = current->gid; 482 #endif 483 #if ACCT_VERSION==3 484 ac.ac_pid = current->tgid; 485 ac.ac_ppid = current->parent->tgid; 486 #endif 487 488 spin_lock_irq(¤t->sighand->siglock); 489 tty = current->signal->tty; 490 ac.ac_tty = tty ? old_encode_dev(tty_devnum(tty)) : 0; 491 ac.ac_utime = encode_comp_t(jiffies_to_AHZ(cputime_to_jiffies(pacct->ac_utime))); 492 ac.ac_stime = encode_comp_t(jiffies_to_AHZ(cputime_to_jiffies(pacct->ac_stime))); 493 ac.ac_flag = pacct->ac_flag; 494 ac.ac_mem = encode_comp_t(pacct->ac_mem); 495 ac.ac_minflt = encode_comp_t(pacct->ac_minflt); 496 ac.ac_majflt = encode_comp_t(pacct->ac_majflt); 497 ac.ac_exitcode = pacct->ac_exitcode; 498 spin_unlock_irq(¤t->sighand->siglock); 499 ac.ac_io = encode_comp_t(0 /* current->io_usage */); /* %% */ 500 ac.ac_rw = encode_comp_t(ac.ac_io / 1024); 501 ac.ac_swaps = encode_comp_t(0); 502 503 /* 504 * Kernel segment override to datasegment and write it 505 * to the accounting file. 506 */ 507 fs = get_fs(); 508 set_fs(KERNEL_DS); 509 /* 510 * Accounting records are not subject to resource limits. 511 */ 512 flim = current->signal->rlim[RLIMIT_FSIZE].rlim_cur; 513 current->signal->rlim[RLIMIT_FSIZE].rlim_cur = RLIM_INFINITY; 514 file->f_op->write(file, (char *)&ac, 515 sizeof(acct_t), &file->f_pos); 516 current->signal->rlim[RLIMIT_FSIZE].rlim_cur = flim; 517 set_fs(fs); 518 } 519 520 /** 521 * acct_init_pacct - initialize a new pacct_struct 522 * @pacct: per-process accounting info struct to initialize 523 */ 524 void acct_init_pacct(struct pacct_struct *pacct) 525 { 526 memset(pacct, 0, sizeof(struct pacct_struct)); 527 pacct->ac_utime = pacct->ac_stime = cputime_zero; 528 } 529 530 /** 531 * acct_collect - collect accounting information into pacct_struct 532 * @exitcode: task exit code 533 * @group_dead: not 0, if this thread is the last one in the process. 534 */ 535 void acct_collect(long exitcode, int group_dead) 536 { 537 struct pacct_struct *pacct = ¤t->signal->pacct; 538 unsigned long vsize = 0; 539 540 if (group_dead && current->mm) { 541 struct vm_area_struct *vma; 542 down_read(¤t->mm->mmap_sem); 543 vma = current->mm->mmap; 544 while (vma) { 545 vsize += vma->vm_end - vma->vm_start; 546 vma = vma->vm_next; 547 } 548 up_read(¤t->mm->mmap_sem); 549 } 550 551 spin_lock_irq(¤t->sighand->siglock); 552 if (group_dead) 553 pacct->ac_mem = vsize / 1024; 554 if (thread_group_leader(current)) { 555 pacct->ac_exitcode = exitcode; 556 if (current->flags & PF_FORKNOEXEC) 557 pacct->ac_flag |= AFORK; 558 } 559 if (current->flags & PF_SUPERPRIV) 560 pacct->ac_flag |= ASU; 561 if (current->flags & PF_DUMPCORE) 562 pacct->ac_flag |= ACORE; 563 if (current->flags & PF_SIGNALED) 564 pacct->ac_flag |= AXSIG; 565 pacct->ac_utime = cputime_add(pacct->ac_utime, current->utime); 566 pacct->ac_stime = cputime_add(pacct->ac_stime, current->stime); 567 pacct->ac_minflt += current->min_flt; 568 pacct->ac_majflt += current->maj_flt; 569 spin_unlock_irq(¤t->sighand->siglock); 570 } 571 572 /** 573 * acct_process - now just a wrapper around do_acct_process 574 * @exitcode: task exit code 575 * 576 * handles process accounting for an exiting task 577 */ 578 void acct_process(void) 579 { 580 struct file *file = NULL; 581 582 /* 583 * accelerate the common fastpath: 584 */ 585 if (!acct_globals.file) 586 return; 587 588 spin_lock(&acct_globals.lock); 589 file = acct_globals.file; 590 if (unlikely(!file)) { 591 spin_unlock(&acct_globals.lock); 592 return; 593 } 594 get_file(file); 595 spin_unlock(&acct_globals.lock); 596 597 do_acct_process(file); 598 fput(file); 599 } 600