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 <linux/uaccess.h> 59 #include <linux/sched/cputime.h> 60 61 #include <asm/div64.h> 62 #include <linux/blkdev.h> /* sector_div */ 63 #include <linux/pid_namespace.h> 64 #include <linux/fs_pin.h> 65 66 /* 67 * These constants control the amount of freespace that suspend and 68 * resume the process accounting system, and the time delay between 69 * each check. 70 * Turned into sysctl-controllable parameters. AV, 12/11/98 71 */ 72 73 int acct_parm[3] = {4, 2, 30}; 74 #define RESUME (acct_parm[0]) /* >foo% free space - resume */ 75 #define SUSPEND (acct_parm[1]) /* <foo% free space - suspend */ 76 #define ACCT_TIMEOUT (acct_parm[2]) /* foo second timeout between checks */ 77 78 /* 79 * External references and all of the globals. 80 */ 81 82 struct bsd_acct_struct { 83 struct fs_pin pin; 84 atomic_long_t count; 85 struct rcu_head rcu; 86 struct mutex lock; 87 int active; 88 unsigned long needcheck; 89 struct file *file; 90 struct pid_namespace *ns; 91 struct work_struct work; 92 struct completion done; 93 }; 94 95 static void do_acct_process(struct bsd_acct_struct *acct); 96 97 /* 98 * Check the amount of free space and suspend/resume accordingly. 99 */ 100 static int check_free_space(struct bsd_acct_struct *acct) 101 { 102 struct kstatfs sbuf; 103 104 if (time_is_before_jiffies(acct->needcheck)) 105 goto out; 106 107 /* May block */ 108 if (vfs_statfs(&acct->file->f_path, &sbuf)) 109 goto out; 110 111 if (acct->active) { 112 u64 suspend = sbuf.f_blocks * SUSPEND; 113 do_div(suspend, 100); 114 if (sbuf.f_bavail <= suspend) { 115 acct->active = 0; 116 pr_info("Process accounting paused\n"); 117 } 118 } else { 119 u64 resume = sbuf.f_blocks * RESUME; 120 do_div(resume, 100); 121 if (sbuf.f_bavail >= resume) { 122 acct->active = 1; 123 pr_info("Process accounting resumed\n"); 124 } 125 } 126 127 acct->needcheck = jiffies + ACCT_TIMEOUT*HZ; 128 out: 129 return acct->active; 130 } 131 132 static void acct_put(struct bsd_acct_struct *p) 133 { 134 if (atomic_long_dec_and_test(&p->count)) 135 kfree_rcu(p, rcu); 136 } 137 138 static inline struct bsd_acct_struct *to_acct(struct fs_pin *p) 139 { 140 return p ? container_of(p, struct bsd_acct_struct, pin) : NULL; 141 } 142 143 static struct bsd_acct_struct *acct_get(struct pid_namespace *ns) 144 { 145 struct bsd_acct_struct *res; 146 again: 147 smp_rmb(); 148 rcu_read_lock(); 149 res = to_acct(READ_ONCE(ns->bacct)); 150 if (!res) { 151 rcu_read_unlock(); 152 return NULL; 153 } 154 if (!atomic_long_inc_not_zero(&res->count)) { 155 rcu_read_unlock(); 156 cpu_relax(); 157 goto again; 158 } 159 rcu_read_unlock(); 160 mutex_lock(&res->lock); 161 if (res != to_acct(READ_ONCE(ns->bacct))) { 162 mutex_unlock(&res->lock); 163 acct_put(res); 164 goto again; 165 } 166 return res; 167 } 168 169 static void acct_pin_kill(struct fs_pin *pin) 170 { 171 struct bsd_acct_struct *acct = to_acct(pin); 172 mutex_lock(&acct->lock); 173 do_acct_process(acct); 174 schedule_work(&acct->work); 175 wait_for_completion(&acct->done); 176 cmpxchg(&acct->ns->bacct, pin, NULL); 177 mutex_unlock(&acct->lock); 178 pin_remove(pin); 179 acct_put(acct); 180 } 181 182 static void close_work(struct work_struct *work) 183 { 184 struct bsd_acct_struct *acct = container_of(work, struct bsd_acct_struct, work); 185 struct file *file = acct->file; 186 if (file->f_op->flush) 187 file->f_op->flush(file, NULL); 188 __fput_sync(file); 189 complete(&acct->done); 190 } 191 192 static int acct_on(struct filename *pathname) 193 { 194 struct file *file; 195 struct vfsmount *mnt, *internal; 196 struct pid_namespace *ns = task_active_pid_ns(current); 197 struct bsd_acct_struct *acct; 198 struct fs_pin *old; 199 int err; 200 201 acct = kzalloc(sizeof(struct bsd_acct_struct), GFP_KERNEL); 202 if (!acct) 203 return -ENOMEM; 204 205 /* Difference from BSD - they don't do O_APPEND */ 206 file = file_open_name(pathname, O_WRONLY|O_APPEND|O_LARGEFILE, 0); 207 if (IS_ERR(file)) { 208 kfree(acct); 209 return PTR_ERR(file); 210 } 211 212 if (!S_ISREG(file_inode(file)->i_mode)) { 213 kfree(acct); 214 filp_close(file, NULL); 215 return -EACCES; 216 } 217 218 if (!(file->f_mode & FMODE_CAN_WRITE)) { 219 kfree(acct); 220 filp_close(file, NULL); 221 return -EIO; 222 } 223 internal = mnt_clone_internal(&file->f_path); 224 if (IS_ERR(internal)) { 225 kfree(acct); 226 filp_close(file, NULL); 227 return PTR_ERR(internal); 228 } 229 err = mnt_want_write(internal); 230 if (err) { 231 mntput(internal); 232 kfree(acct); 233 filp_close(file, NULL); 234 return err; 235 } 236 mnt = file->f_path.mnt; 237 file->f_path.mnt = internal; 238 239 atomic_long_set(&acct->count, 1); 240 init_fs_pin(&acct->pin, acct_pin_kill); 241 acct->file = file; 242 acct->needcheck = jiffies; 243 acct->ns = ns; 244 mutex_init(&acct->lock); 245 INIT_WORK(&acct->work, close_work); 246 init_completion(&acct->done); 247 mutex_lock_nested(&acct->lock, 1); /* nobody has seen it yet */ 248 pin_insert(&acct->pin, mnt); 249 250 rcu_read_lock(); 251 old = xchg(&ns->bacct, &acct->pin); 252 mutex_unlock(&acct->lock); 253 pin_kill(old); 254 mnt_drop_write(mnt); 255 mntput(mnt); 256 return 0; 257 } 258 259 static DEFINE_MUTEX(acct_on_mutex); 260 261 /** 262 * sys_acct - enable/disable process accounting 263 * @name: file name for accounting records or NULL to shutdown accounting 264 * 265 * Returns 0 for success or negative errno values for failure. 266 * 267 * sys_acct() is the only system call needed to implement process 268 * accounting. It takes the name of the file where accounting records 269 * should be written. If the filename is NULL, accounting will be 270 * shutdown. 271 */ 272 SYSCALL_DEFINE1(acct, const char __user *, name) 273 { 274 int error = 0; 275 276 if (!capable(CAP_SYS_PACCT)) 277 return -EPERM; 278 279 if (name) { 280 struct filename *tmp = getname(name); 281 282 if (IS_ERR(tmp)) 283 return PTR_ERR(tmp); 284 mutex_lock(&acct_on_mutex); 285 error = acct_on(tmp); 286 mutex_unlock(&acct_on_mutex); 287 putname(tmp); 288 } else { 289 rcu_read_lock(); 290 pin_kill(task_active_pid_ns(current)->bacct); 291 } 292 293 return error; 294 } 295 296 void acct_exit_ns(struct pid_namespace *ns) 297 { 298 rcu_read_lock(); 299 pin_kill(ns->bacct); 300 } 301 302 /* 303 * encode an unsigned long into a comp_t 304 * 305 * This routine has been adopted from the encode_comp_t() function in 306 * the kern_acct.c file of the FreeBSD operating system. The encoding 307 * is a 13-bit fraction with a 3-bit (base 8) exponent. 308 */ 309 310 #define MANTSIZE 13 /* 13 bit mantissa. */ 311 #define EXPSIZE 3 /* Base 8 (3 bit) exponent. */ 312 #define MAXFRACT ((1 << MANTSIZE) - 1) /* Maximum fractional value. */ 313 314 static comp_t encode_comp_t(unsigned long value) 315 { 316 int exp, rnd; 317 318 exp = rnd = 0; 319 while (value > MAXFRACT) { 320 rnd = value & (1 << (EXPSIZE - 1)); /* Round up? */ 321 value >>= EXPSIZE; /* Base 8 exponent == 3 bit shift. */ 322 exp++; 323 } 324 325 /* 326 * If we need to round up, do it (and handle overflow correctly). 327 */ 328 if (rnd && (++value > MAXFRACT)) { 329 value >>= EXPSIZE; 330 exp++; 331 } 332 333 /* 334 * Clean it up and polish it off. 335 */ 336 exp <<= MANTSIZE; /* Shift the exponent into place */ 337 exp += value; /* and add on the mantissa. */ 338 return exp; 339 } 340 341 #if ACCT_VERSION == 1 || ACCT_VERSION == 2 342 /* 343 * encode an u64 into a comp2_t (24 bits) 344 * 345 * Format: 5 bit base 2 exponent, 20 bits mantissa. 346 * The leading bit of the mantissa is not stored, but implied for 347 * non-zero exponents. 348 * Largest encodable value is 50 bits. 349 */ 350 351 #define MANTSIZE2 20 /* 20 bit mantissa. */ 352 #define EXPSIZE2 5 /* 5 bit base 2 exponent. */ 353 #define MAXFRACT2 ((1ul << MANTSIZE2) - 1) /* Maximum fractional value. */ 354 #define MAXEXP2 ((1 << EXPSIZE2) - 1) /* Maximum exponent. */ 355 356 static comp2_t encode_comp2_t(u64 value) 357 { 358 int exp, rnd; 359 360 exp = (value > (MAXFRACT2>>1)); 361 rnd = 0; 362 while (value > MAXFRACT2) { 363 rnd = value & 1; 364 value >>= 1; 365 exp++; 366 } 367 368 /* 369 * If we need to round up, do it (and handle overflow correctly). 370 */ 371 if (rnd && (++value > MAXFRACT2)) { 372 value >>= 1; 373 exp++; 374 } 375 376 if (exp > MAXEXP2) { 377 /* Overflow. Return largest representable number instead. */ 378 return (1ul << (MANTSIZE2+EXPSIZE2-1)) - 1; 379 } else { 380 return (value & (MAXFRACT2>>1)) | (exp << (MANTSIZE2-1)); 381 } 382 } 383 #endif 384 385 #if ACCT_VERSION == 3 386 /* 387 * encode an u64 into a 32 bit IEEE float 388 */ 389 static u32 encode_float(u64 value) 390 { 391 unsigned exp = 190; 392 unsigned u; 393 394 if (value == 0) 395 return 0; 396 while ((s64)value > 0) { 397 value <<= 1; 398 exp--; 399 } 400 u = (u32)(value >> 40) & 0x7fffffu; 401 return u | (exp << 23); 402 } 403 #endif 404 405 /* 406 * Write an accounting entry for an exiting process 407 * 408 * The acct_process() call is the workhorse of the process 409 * accounting system. The struct acct is built here and then written 410 * into the accounting file. This function should only be called from 411 * do_exit() or when switching to a different output file. 412 */ 413 414 static void fill_ac(acct_t *ac) 415 { 416 struct pacct_struct *pacct = ¤t->signal->pacct; 417 u64 elapsed, run_time; 418 struct tty_struct *tty; 419 420 /* 421 * Fill the accounting struct with the needed info as recorded 422 * by the different kernel functions. 423 */ 424 memset(ac, 0, sizeof(acct_t)); 425 426 ac->ac_version = ACCT_VERSION | ACCT_BYTEORDER; 427 strlcpy(ac->ac_comm, current->comm, sizeof(ac->ac_comm)); 428 429 /* calculate run_time in nsec*/ 430 run_time = ktime_get_ns(); 431 run_time -= current->group_leader->start_time; 432 /* convert nsec -> AHZ */ 433 elapsed = nsec_to_AHZ(run_time); 434 #if ACCT_VERSION == 3 435 ac->ac_etime = encode_float(elapsed); 436 #else 437 ac->ac_etime = encode_comp_t(elapsed < (unsigned long) -1l ? 438 (unsigned long) elapsed : (unsigned long) -1l); 439 #endif 440 #if ACCT_VERSION == 1 || ACCT_VERSION == 2 441 { 442 /* new enlarged etime field */ 443 comp2_t etime = encode_comp2_t(elapsed); 444 445 ac->ac_etime_hi = etime >> 16; 446 ac->ac_etime_lo = (u16) etime; 447 } 448 #endif 449 do_div(elapsed, AHZ); 450 ac->ac_btime = get_seconds() - elapsed; 451 #if ACCT_VERSION==2 452 ac->ac_ahz = AHZ; 453 #endif 454 455 spin_lock_irq(¤t->sighand->siglock); 456 tty = current->signal->tty; /* Safe as we hold the siglock */ 457 ac->ac_tty = tty ? old_encode_dev(tty_devnum(tty)) : 0; 458 ac->ac_utime = encode_comp_t(nsec_to_AHZ(pacct->ac_utime)); 459 ac->ac_stime = encode_comp_t(nsec_to_AHZ(pacct->ac_stime)); 460 ac->ac_flag = pacct->ac_flag; 461 ac->ac_mem = encode_comp_t(pacct->ac_mem); 462 ac->ac_minflt = encode_comp_t(pacct->ac_minflt); 463 ac->ac_majflt = encode_comp_t(pacct->ac_majflt); 464 ac->ac_exitcode = pacct->ac_exitcode; 465 spin_unlock_irq(¤t->sighand->siglock); 466 } 467 /* 468 * do_acct_process does all actual work. Caller holds the reference to file. 469 */ 470 static void do_acct_process(struct bsd_acct_struct *acct) 471 { 472 acct_t ac; 473 unsigned long flim; 474 const struct cred *orig_cred; 475 struct file *file = acct->file; 476 477 /* 478 * Accounting records are not subject to resource limits. 479 */ 480 flim = current->signal->rlim[RLIMIT_FSIZE].rlim_cur; 481 current->signal->rlim[RLIMIT_FSIZE].rlim_cur = RLIM_INFINITY; 482 /* Perform file operations on behalf of whoever enabled accounting */ 483 orig_cred = override_creds(file->f_cred); 484 485 /* 486 * First check to see if there is enough free_space to continue 487 * the process accounting system. 488 */ 489 if (!check_free_space(acct)) 490 goto out; 491 492 fill_ac(&ac); 493 /* we really need to bite the bullet and change layout */ 494 ac.ac_uid = from_kuid_munged(file->f_cred->user_ns, orig_cred->uid); 495 ac.ac_gid = from_kgid_munged(file->f_cred->user_ns, orig_cred->gid); 496 #if ACCT_VERSION == 1 || ACCT_VERSION == 2 497 /* backward-compatible 16 bit fields */ 498 ac.ac_uid16 = ac.ac_uid; 499 ac.ac_gid16 = ac.ac_gid; 500 #endif 501 #if ACCT_VERSION == 3 502 { 503 struct pid_namespace *ns = acct->ns; 504 505 ac.ac_pid = task_tgid_nr_ns(current, ns); 506 rcu_read_lock(); 507 ac.ac_ppid = task_tgid_nr_ns(rcu_dereference(current->real_parent), 508 ns); 509 rcu_read_unlock(); 510 } 511 #endif 512 /* 513 * Get freeze protection. If the fs is frozen, just skip the write 514 * as we could deadlock the system otherwise. 515 */ 516 if (file_start_write_trylock(file)) { 517 /* it's been opened O_APPEND, so position is irrelevant */ 518 loff_t pos = 0; 519 __kernel_write(file, &ac, sizeof(acct_t), &pos); 520 file_end_write(file); 521 } 522 out: 523 current->signal->rlim[RLIMIT_FSIZE].rlim_cur = flim; 524 revert_creds(orig_cred); 525 } 526 527 /** 528 * acct_collect - collect accounting information into pacct_struct 529 * @exitcode: task exit code 530 * @group_dead: not 0, if this thread is the last one in the process. 531 */ 532 void acct_collect(long exitcode, int group_dead) 533 { 534 struct pacct_struct *pacct = ¤t->signal->pacct; 535 u64 utime, stime; 536 unsigned long vsize = 0; 537 538 if (group_dead && current->mm) { 539 struct vm_area_struct *vma; 540 541 down_read(¤t->mm->mmap_sem); 542 vma = current->mm->mmap; 543 while (vma) { 544 vsize += vma->vm_end - vma->vm_start; 545 vma = vma->vm_next; 546 } 547 up_read(¤t->mm->mmap_sem); 548 } 549 550 spin_lock_irq(¤t->sighand->siglock); 551 if (group_dead) 552 pacct->ac_mem = vsize / 1024; 553 if (thread_group_leader(current)) { 554 pacct->ac_exitcode = exitcode; 555 if (current->flags & PF_FORKNOEXEC) 556 pacct->ac_flag |= AFORK; 557 } 558 if (current->flags & PF_SUPERPRIV) 559 pacct->ac_flag |= ASU; 560 if (current->flags & PF_DUMPCORE) 561 pacct->ac_flag |= ACORE; 562 if (current->flags & PF_SIGNALED) 563 pacct->ac_flag |= AXSIG; 564 565 task_cputime(current, &utime, &stime); 566 pacct->ac_utime += utime; 567 pacct->ac_stime += stime; 568 pacct->ac_minflt += current->min_flt; 569 pacct->ac_majflt += current->maj_flt; 570 spin_unlock_irq(¤t->sighand->siglock); 571 } 572 573 static void slow_acct_process(struct pid_namespace *ns) 574 { 575 for ( ; ns; ns = ns->parent) { 576 struct bsd_acct_struct *acct = acct_get(ns); 577 if (acct) { 578 do_acct_process(acct); 579 mutex_unlock(&acct->lock); 580 acct_put(acct); 581 } 582 } 583 } 584 585 /** 586 * acct_process 587 * 588 * handles process accounting for an exiting task 589 */ 590 void acct_process(void) 591 { 592 struct pid_namespace *ns; 593 594 /* 595 * This loop is safe lockless, since current is still 596 * alive and holds its namespace, which in turn holds 597 * its parent. 598 */ 599 for (ns = task_active_pid_ns(current); ns != NULL; ns = ns->parent) { 600 if (ns->bacct) 601 break; 602 } 603 if (unlikely(ns)) 604 slow_acct_process(ns); 605 } 606