4 * BSD Process Accounting for Linux
6 * Author: Marco van Wieringen <mvw@planets.elm.net>
8 * Some code based on ideas and code from:
9 * Thomas K. Dyas <tdyas@eden.rutgers.edu>
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.
17 * (C) Copyright 1995 - 1997 Marco van Wieringen - ELM Consultancy B.V.
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.
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.
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.
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.
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.
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 <asm/div64.h>
60 #include <linux/blkdev.h> /* sector_div */
61 #include <linux/pid_namespace.h>
62 #include <linux/fs_pin.h>
65 * These constants control the amount of freespace that suspend and
66 * resume the process accounting system, and the time delay between
68 * Turned into sysctl-controllable parameters. AV, 12/11/98
71 int acct_parm[3] = {4, 2, 30};
72 #define RESUME (acct_parm[0]) /* >foo% free space - resume */
73 #define SUSPEND (acct_parm[1]) /* <foo% free space - suspend */
74 #define ACCT_TIMEOUT (acct_parm[2]) /* foo second timeout between checks */
77 * External references and all of the globals.
79 static void do_acct_process(struct bsd_acct_struct *acct);
81 struct bsd_acct_struct {
87 unsigned long needcheck;
89 struct pid_namespace *ns;
90 struct work_struct work;
91 struct completion done;
95 * Check the amount of free space and suspend/resume accordingly.
97 static int check_free_space(struct bsd_acct_struct *acct)
101 if (time_is_before_jiffies(acct->needcheck))
105 if (vfs_statfs(&acct->file->f_path, &sbuf))
109 u64 suspend = sbuf.f_blocks * SUSPEND;
110 do_div(suspend, 100);
111 if (sbuf.f_bavail <= suspend) {
113 pr_info("Process accounting paused\n");
116 u64 resume = sbuf.f_blocks * RESUME;
118 if (sbuf.f_bavail >= resume) {
120 pr_info("Process accounting resumed\n");
124 acct->needcheck = jiffies + ACCT_TIMEOUT*HZ;
129 static void acct_put(struct bsd_acct_struct *p)
131 if (atomic_long_dec_and_test(&p->count))
135 static struct bsd_acct_struct *acct_get(struct pid_namespace *ns)
137 struct bsd_acct_struct *res;
141 res = ACCESS_ONCE(ns->bacct);
146 if (!atomic_long_inc_not_zero(&res->count)) {
152 mutex_lock(&res->lock);
154 mutex_unlock(&res->lock);
161 static void close_work(struct work_struct *work)
163 struct bsd_acct_struct *acct = container_of(work, struct bsd_acct_struct, work);
164 struct file *file = acct->file;
165 if (file->f_op->flush)
166 file->f_op->flush(file, NULL);
168 complete(&acct->done);
171 static void acct_kill(struct bsd_acct_struct *acct)
174 struct pid_namespace *ns = acct->ns;
175 do_acct_process(acct);
176 INIT_WORK(&acct->work, close_work);
177 init_completion(&acct->done);
178 schedule_work(&acct->work);
179 wait_for_completion(&acct->done);
180 pin_remove(&acct->pin);
181 cmpxchg(&ns->bacct, acct, NULL);
183 atomic_long_dec(&acct->count);
184 mutex_unlock(&acct->lock);
189 static void acct_pin_kill(struct fs_pin *pin)
191 struct bsd_acct_struct *acct;
192 acct = container_of(pin, struct bsd_acct_struct, pin);
193 if (!atomic_long_inc_not_zero(&acct->count)) {
199 mutex_lock(&acct->lock);
201 mutex_unlock(&acct->lock);
208 static int acct_on(struct filename *pathname)
211 struct vfsmount *mnt, *internal;
212 struct pid_namespace *ns = task_active_pid_ns(current);
213 struct bsd_acct_struct *acct, *old;
216 acct = kzalloc(sizeof(struct bsd_acct_struct), GFP_KERNEL);
220 /* Difference from BSD - they don't do O_APPEND */
221 file = file_open_name(pathname, O_WRONLY|O_APPEND|O_LARGEFILE, 0);
224 return PTR_ERR(file);
227 if (!S_ISREG(file_inode(file)->i_mode)) {
229 filp_close(file, NULL);
233 if (!file->f_op->write) {
235 filp_close(file, NULL);
238 internal = mnt_clone_internal(&file->f_path);
239 if (IS_ERR(internal)) {
241 filp_close(file, NULL);
242 return PTR_ERR(internal);
244 err = mnt_want_write(internal);
248 filp_close(file, NULL);
251 mnt = file->f_path.mnt;
252 file->f_path.mnt = internal;
254 atomic_long_set(&acct->count, 1);
255 acct->pin.kill = acct_pin_kill;
257 acct->needcheck = jiffies;
259 mutex_init(&acct->lock);
260 mutex_lock_nested(&acct->lock, 1); /* nobody has seen it yet */
261 pin_insert(&acct->pin, mnt);
266 mutex_unlock(&acct->lock);
272 static DEFINE_MUTEX(acct_on_mutex);
275 * sys_acct - enable/disable process accounting
276 * @name: file name for accounting records or NULL to shutdown accounting
278 * Returns 0 for success or negative errno values for failure.
280 * sys_acct() is the only system call needed to implement process
281 * accounting. It takes the name of the file where accounting records
282 * should be written. If the filename is NULL, accounting will be
285 SYSCALL_DEFINE1(acct, const char __user *, name)
289 if (!capable(CAP_SYS_PACCT))
293 struct filename *tmp = getname(name);
297 mutex_lock(&acct_on_mutex);
298 error = acct_on(tmp);
299 mutex_unlock(&acct_on_mutex);
302 acct_kill(acct_get(task_active_pid_ns(current)));
308 void acct_exit_ns(struct pid_namespace *ns)
310 acct_kill(acct_get(ns));
314 * encode an unsigned long into a comp_t
316 * This routine has been adopted from the encode_comp_t() function in
317 * the kern_acct.c file of the FreeBSD operating system. The encoding
318 * is a 13-bit fraction with a 3-bit (base 8) exponent.
321 #define MANTSIZE 13 /* 13 bit mantissa. */
322 #define EXPSIZE 3 /* Base 8 (3 bit) exponent. */
323 #define MAXFRACT ((1 << MANTSIZE) - 1) /* Maximum fractional value. */
325 static comp_t encode_comp_t(unsigned long value)
330 while (value > MAXFRACT) {
331 rnd = value & (1 << (EXPSIZE - 1)); /* Round up? */
332 value >>= EXPSIZE; /* Base 8 exponent == 3 bit shift. */
337 * If we need to round up, do it (and handle overflow correctly).
339 if (rnd && (++value > MAXFRACT)) {
345 * Clean it up and polish it off.
347 exp <<= MANTSIZE; /* Shift the exponent into place */
348 exp += value; /* and add on the mantissa. */
352 #if ACCT_VERSION == 1 || ACCT_VERSION == 2
354 * encode an u64 into a comp2_t (24 bits)
356 * Format: 5 bit base 2 exponent, 20 bits mantissa.
357 * The leading bit of the mantissa is not stored, but implied for
358 * non-zero exponents.
359 * Largest encodable value is 50 bits.
362 #define MANTSIZE2 20 /* 20 bit mantissa. */
363 #define EXPSIZE2 5 /* 5 bit base 2 exponent. */
364 #define MAXFRACT2 ((1ul << MANTSIZE2) - 1) /* Maximum fractional value. */
365 #define MAXEXP2 ((1 << EXPSIZE2) - 1) /* Maximum exponent. */
367 static comp2_t encode_comp2_t(u64 value)
371 exp = (value > (MAXFRACT2>>1));
373 while (value > MAXFRACT2) {
380 * If we need to round up, do it (and handle overflow correctly).
382 if (rnd && (++value > MAXFRACT2)) {
388 /* Overflow. Return largest representable number instead. */
389 return (1ul << (MANTSIZE2+EXPSIZE2-1)) - 1;
391 return (value & (MAXFRACT2>>1)) | (exp << (MANTSIZE2-1));
396 #if ACCT_VERSION == 3
398 * encode an u64 into a 32 bit IEEE float
400 static u32 encode_float(u64 value)
407 while ((s64)value > 0) {
411 u = (u32)(value >> 40) & 0x7fffffu;
412 return u | (exp << 23);
417 * Write an accounting entry for an exiting process
419 * The acct_process() call is the workhorse of the process
420 * accounting system. The struct acct is built here and then written
421 * into the accounting file. This function should only be called from
422 * do_exit() or when switching to a different output file.
425 static void fill_ac(acct_t *ac)
427 struct pacct_struct *pacct = ¤t->signal->pacct;
428 u64 elapsed, run_time;
429 struct tty_struct *tty;
432 * Fill the accounting struct with the needed info as recorded
433 * by the different kernel functions.
435 memset(ac, 0, sizeof(acct_t));
437 ac->ac_version = ACCT_VERSION | ACCT_BYTEORDER;
438 strlcpy(ac->ac_comm, current->comm, sizeof(ac->ac_comm));
440 /* calculate run_time in nsec*/
441 run_time = ktime_get_ns();
442 run_time -= current->group_leader->start_time;
443 /* convert nsec -> AHZ */
444 elapsed = nsec_to_AHZ(run_time);
445 #if ACCT_VERSION == 3
446 ac->ac_etime = encode_float(elapsed);
448 ac->ac_etime = encode_comp_t(elapsed < (unsigned long) -1l ?
449 (unsigned long) elapsed : (unsigned long) -1l);
451 #if ACCT_VERSION == 1 || ACCT_VERSION == 2
453 /* new enlarged etime field */
454 comp2_t etime = encode_comp2_t(elapsed);
456 ac->ac_etime_hi = etime >> 16;
457 ac->ac_etime_lo = (u16) etime;
460 do_div(elapsed, AHZ);
461 ac->ac_btime = get_seconds() - elapsed;
466 spin_lock_irq(¤t->sighand->siglock);
467 tty = current->signal->tty; /* Safe as we hold the siglock */
468 ac->ac_tty = tty ? old_encode_dev(tty_devnum(tty)) : 0;
469 ac->ac_utime = encode_comp_t(jiffies_to_AHZ(cputime_to_jiffies(pacct->ac_utime)));
470 ac->ac_stime = encode_comp_t(jiffies_to_AHZ(cputime_to_jiffies(pacct->ac_stime)));
471 ac->ac_flag = pacct->ac_flag;
472 ac->ac_mem = encode_comp_t(pacct->ac_mem);
473 ac->ac_minflt = encode_comp_t(pacct->ac_minflt);
474 ac->ac_majflt = encode_comp_t(pacct->ac_majflt);
475 ac->ac_exitcode = pacct->ac_exitcode;
476 spin_unlock_irq(¤t->sighand->siglock);
479 * do_acct_process does all actual work. Caller holds the reference to file.
481 static void do_acct_process(struct bsd_acct_struct *acct)
485 const struct cred *orig_cred;
486 struct file *file = acct->file;
489 * Accounting records are not subject to resource limits.
491 flim = current->signal->rlim[RLIMIT_FSIZE].rlim_cur;
492 current->signal->rlim[RLIMIT_FSIZE].rlim_cur = RLIM_INFINITY;
493 /* Perform file operations on behalf of whoever enabled accounting */
494 orig_cred = override_creds(file->f_cred);
497 * First check to see if there is enough free_space to continue
498 * the process accounting system.
500 if (!check_free_space(acct))
504 /* we really need to bite the bullet and change layout */
505 ac.ac_uid = from_kuid_munged(file->f_cred->user_ns, orig_cred->uid);
506 ac.ac_gid = from_kgid_munged(file->f_cred->user_ns, orig_cred->gid);
507 #if ACCT_VERSION == 1 || ACCT_VERSION == 2
508 /* backward-compatible 16 bit fields */
509 ac.ac_uid16 = ac.ac_uid;
510 ac.ac_gid16 = ac.ac_gid;
512 #if ACCT_VERSION == 3
514 struct pid_namespace *ns = acct->ns;
516 ac.ac_pid = task_tgid_nr_ns(current, ns);
518 ac.ac_ppid = task_tgid_nr_ns(rcu_dereference(current->real_parent),
524 * Get freeze protection. If the fs is frozen, just skip the write
525 * as we could deadlock the system otherwise.
527 if (file_start_write_trylock(file)) {
528 /* it's been opened O_APPEND, so position is irrelevant */
530 __kernel_write(file, (char *)&ac, sizeof(acct_t), &pos);
531 file_end_write(file);
534 current->signal->rlim[RLIMIT_FSIZE].rlim_cur = flim;
535 revert_creds(orig_cred);
539 * acct_collect - collect accounting information into pacct_struct
540 * @exitcode: task exit code
541 * @group_dead: not 0, if this thread is the last one in the process.
543 void acct_collect(long exitcode, int group_dead)
545 struct pacct_struct *pacct = ¤t->signal->pacct;
546 cputime_t utime, stime;
547 unsigned long vsize = 0;
549 if (group_dead && current->mm) {
550 struct vm_area_struct *vma;
552 down_read(¤t->mm->mmap_sem);
553 vma = current->mm->mmap;
555 vsize += vma->vm_end - vma->vm_start;
558 up_read(¤t->mm->mmap_sem);
561 spin_lock_irq(¤t->sighand->siglock);
563 pacct->ac_mem = vsize / 1024;
564 if (thread_group_leader(current)) {
565 pacct->ac_exitcode = exitcode;
566 if (current->flags & PF_FORKNOEXEC)
567 pacct->ac_flag |= AFORK;
569 if (current->flags & PF_SUPERPRIV)
570 pacct->ac_flag |= ASU;
571 if (current->flags & PF_DUMPCORE)
572 pacct->ac_flag |= ACORE;
573 if (current->flags & PF_SIGNALED)
574 pacct->ac_flag |= AXSIG;
575 task_cputime(current, &utime, &stime);
576 pacct->ac_utime += utime;
577 pacct->ac_stime += stime;
578 pacct->ac_minflt += current->min_flt;
579 pacct->ac_majflt += current->maj_flt;
580 spin_unlock_irq(¤t->sighand->siglock);
583 static void slow_acct_process(struct pid_namespace *ns)
585 for ( ; ns; ns = ns->parent) {
586 struct bsd_acct_struct *acct = acct_get(ns);
588 do_acct_process(acct);
589 mutex_unlock(&acct->lock);
598 * handles process accounting for an exiting task
600 void acct_process(void)
602 struct pid_namespace *ns;
605 * This loop is safe lockless, since current is still
606 * alive and holds its namespace, which in turn holds
609 for (ns = task_active_pid_ns(current); ns != NULL; ns = ns->parent) {
614 slow_acct_process(ns);