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 <../fs/mount.h> /* will go away when we refactor */
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 {
85 struct hlist_node s_list;
86 struct hlist_node m_list;
92 unsigned long needcheck;
94 struct pid_namespace *ns;
95 struct work_struct work;
96 struct completion done;
99 static void acct_free_rcu(struct rcu_head *head)
101 kfree(container_of(head, struct bsd_acct_struct, rcu));
104 static DEFINE_SPINLOCK(acct_lock);
107 * Check the amount of free space and suspend/resume accordingly.
109 static int check_free_space(struct bsd_acct_struct *acct)
113 if (time_is_before_jiffies(acct->needcheck))
117 if (vfs_statfs(&acct->file->f_path, &sbuf))
121 u64 suspend = sbuf.f_blocks * SUSPEND;
122 do_div(suspend, 100);
123 if (sbuf.f_bavail <= suspend) {
125 printk(KERN_INFO "Process accounting paused\n");
128 u64 resume = sbuf.f_blocks * RESUME;
130 if (sbuf.f_bavail >= resume) {
132 printk(KERN_INFO "Process accounting resumed\n");
136 acct->needcheck = jiffies + ACCT_TIMEOUT*HZ;
141 static void acct_put(struct bsd_acct_struct *p)
143 if (atomic_long_dec_and_test(&p->count))
144 call_rcu(&p->rcu, acct_free_rcu);
147 static struct bsd_acct_struct *__acct_get(struct bsd_acct_struct *res)
149 if (!atomic_long_inc_not_zero(&res->count)) {
155 mutex_lock(&res->lock);
157 mutex_unlock(&res->lock);
164 static struct bsd_acct_struct *acct_get(struct pid_namespace *ns)
166 struct bsd_acct_struct *res;
170 res = ACCESS_ONCE(ns->bacct);
175 res = __acct_get(res);
181 static void close_work(struct work_struct *work)
183 struct bsd_acct_struct *acct = container_of(work, struct bsd_acct_struct, work);
184 struct file *file = acct->file;
185 mnt_unpin(file->f_path.mnt);
186 if (file->f_op->flush)
187 file->f_op->flush(file, NULL);
189 complete(&acct->done);
192 static void acct_kill(struct bsd_acct_struct *acct,
193 struct bsd_acct_struct *new)
196 struct pid_namespace *ns = acct->ns;
197 do_acct_process(acct);
198 INIT_WORK(&acct->work, close_work);
199 init_completion(&acct->done);
200 schedule_work(&acct->work);
201 wait_for_completion(&acct->done);
202 spin_lock(&acct_lock);
203 hlist_del(&acct->m_list);
204 hlist_del(&acct->s_list);
205 spin_unlock(&acct_lock);
208 struct vfsmount *m = new->file->f_path.mnt;
209 spin_lock(&acct_lock);
210 hlist_add_head(&new->s_list, &m->mnt_sb->s_pins);
211 hlist_add_head(&new->m_list, &real_mount(m)->mnt_pins);
212 spin_unlock(&acct_lock);
213 mutex_unlock(&new->lock);
216 atomic_long_dec(&acct->count);
217 mutex_unlock(&acct->lock);
222 static int acct_on(struct filename *pathname)
225 struct vfsmount *mnt;
226 struct pid_namespace *ns = task_active_pid_ns(current);
227 struct bsd_acct_struct *acct, *old;
229 acct = kzalloc(sizeof(struct bsd_acct_struct), GFP_KERNEL);
233 /* Difference from BSD - they don't do O_APPEND */
234 file = file_open_name(pathname, O_WRONLY|O_APPEND|O_LARGEFILE, 0);
237 return PTR_ERR(file);
240 if (!S_ISREG(file_inode(file)->i_mode)) {
242 filp_close(file, NULL);
246 if (!file->f_op->write) {
248 filp_close(file, NULL);
252 atomic_long_set(&acct->count, 1);
254 acct->needcheck = jiffies;
256 mutex_init(&acct->lock);
257 mnt = file->f_path.mnt;
261 mutex_lock_nested(&acct->lock, 1); /* nobody has seen it yet */
263 acct_kill(old, acct);
266 spin_lock(&acct_lock);
267 hlist_add_head(&acct->s_list, &mnt->mnt_sb->s_pins);
268 hlist_add_head(&acct->m_list, &real_mount(mnt)->mnt_pins);
269 spin_unlock(&acct_lock);
270 mutex_unlock(&acct->lock);
272 mntput(mnt); /* it's pinned, now give up active reference */
276 static DEFINE_MUTEX(acct_on_mutex);
279 * sys_acct - enable/disable process accounting
280 * @name: file name for accounting records or NULL to shutdown accounting
282 * Returns 0 for success or negative errno values for failure.
284 * sys_acct() is the only system call needed to implement process
285 * accounting. It takes the name of the file where accounting records
286 * should be written. If the filename is NULL, accounting will be
289 SYSCALL_DEFINE1(acct, const char __user *, name)
293 if (!capable(CAP_SYS_PACCT))
297 struct filename *tmp = getname(name);
300 mutex_lock(&acct_on_mutex);
301 error = acct_on(tmp);
302 mutex_unlock(&acct_on_mutex);
305 acct_kill(acct_get(task_active_pid_ns(current)), NULL);
311 void acct_auto_close_mnt(struct hlist_head *list)
315 struct hlist_node *p = ACCESS_ONCE(list->first);
318 acct_kill(__acct_get(hlist_entry(p,
319 struct bsd_acct_struct,
326 void acct_auto_close(struct hlist_head *list)
330 struct hlist_node *p = ACCESS_ONCE(list->first);
333 acct_kill(__acct_get(hlist_entry(p,
334 struct bsd_acct_struct,
341 void acct_exit_ns(struct pid_namespace *ns)
343 acct_kill(acct_get(ns), NULL);
347 * encode an unsigned long into a comp_t
349 * This routine has been adopted from the encode_comp_t() function in
350 * the kern_acct.c file of the FreeBSD operating system. The encoding
351 * is a 13-bit fraction with a 3-bit (base 8) exponent.
354 #define MANTSIZE 13 /* 13 bit mantissa. */
355 #define EXPSIZE 3 /* Base 8 (3 bit) exponent. */
356 #define MAXFRACT ((1 << MANTSIZE) - 1) /* Maximum fractional value. */
358 static comp_t encode_comp_t(unsigned long value)
363 while (value > MAXFRACT) {
364 rnd = value & (1 << (EXPSIZE - 1)); /* Round up? */
365 value >>= EXPSIZE; /* Base 8 exponent == 3 bit shift. */
370 * If we need to round up, do it (and handle overflow correctly).
372 if (rnd && (++value > MAXFRACT)) {
378 * Clean it up and polish it off.
380 exp <<= MANTSIZE; /* Shift the exponent into place */
381 exp += value; /* and add on the mantissa. */
385 #if ACCT_VERSION==1 || ACCT_VERSION==2
387 * encode an u64 into a comp2_t (24 bits)
389 * Format: 5 bit base 2 exponent, 20 bits mantissa.
390 * The leading bit of the mantissa is not stored, but implied for
391 * non-zero exponents.
392 * Largest encodable value is 50 bits.
395 #define MANTSIZE2 20 /* 20 bit mantissa. */
396 #define EXPSIZE2 5 /* 5 bit base 2 exponent. */
397 #define MAXFRACT2 ((1ul << MANTSIZE2) - 1) /* Maximum fractional value. */
398 #define MAXEXP2 ((1 <<EXPSIZE2) - 1) /* Maximum exponent. */
400 static comp2_t encode_comp2_t(u64 value)
404 exp = (value > (MAXFRACT2>>1));
406 while (value > MAXFRACT2) {
413 * If we need to round up, do it (and handle overflow correctly).
415 if (rnd && (++value > MAXFRACT2)) {
421 /* Overflow. Return largest representable number instead. */
422 return (1ul << (MANTSIZE2+EXPSIZE2-1)) - 1;
424 return (value & (MAXFRACT2>>1)) | (exp << (MANTSIZE2-1));
431 * encode an u64 into a 32 bit IEEE float
433 static u32 encode_float(u64 value)
438 if (value==0) return 0;
439 while ((s64)value > 0){
443 u = (u32)(value >> 40) & 0x7fffffu;
444 return u | (exp << 23);
449 * Write an accounting entry for an exiting process
451 * The acct_process() call is the workhorse of the process
452 * accounting system. The struct acct is built here and then written
453 * into the accounting file. This function should only be called from
454 * do_exit() or when switching to a different output file.
457 static void fill_ac(acct_t *ac)
459 struct pacct_struct *pacct = ¤t->signal->pacct;
460 u64 elapsed, run_time;
461 struct tty_struct *tty;
464 * Fill the accounting struct with the needed info as recorded
465 * by the different kernel functions.
467 memset(ac, 0, sizeof(acct_t));
469 ac->ac_version = ACCT_VERSION | ACCT_BYTEORDER;
470 strlcpy(ac->ac_comm, current->comm, sizeof(ac->ac_comm));
472 /* calculate run_time in nsec*/
473 run_time = ktime_get_ns();
474 run_time -= current->group_leader->start_time;
475 /* convert nsec -> AHZ */
476 elapsed = nsec_to_AHZ(run_time);
478 ac->ac_etime = encode_float(elapsed);
480 ac->ac_etime = encode_comp_t(elapsed < (unsigned long) -1l ?
481 (unsigned long) elapsed : (unsigned long) -1l);
483 #if ACCT_VERSION==1 || ACCT_VERSION==2
485 /* new enlarged etime field */
486 comp2_t etime = encode_comp2_t(elapsed);
487 ac->ac_etime_hi = etime >> 16;
488 ac->ac_etime_lo = (u16) etime;
491 do_div(elapsed, AHZ);
492 ac->ac_btime = get_seconds() - elapsed;
497 spin_lock_irq(¤t->sighand->siglock);
498 tty = current->signal->tty; /* Safe as we hold the siglock */
499 ac->ac_tty = tty ? old_encode_dev(tty_devnum(tty)) : 0;
500 ac->ac_utime = encode_comp_t(jiffies_to_AHZ(cputime_to_jiffies(pacct->ac_utime)));
501 ac->ac_stime = encode_comp_t(jiffies_to_AHZ(cputime_to_jiffies(pacct->ac_stime)));
502 ac->ac_flag = pacct->ac_flag;
503 ac->ac_mem = encode_comp_t(pacct->ac_mem);
504 ac->ac_minflt = encode_comp_t(pacct->ac_minflt);
505 ac->ac_majflt = encode_comp_t(pacct->ac_majflt);
506 ac->ac_exitcode = pacct->ac_exitcode;
507 spin_unlock_irq(¤t->sighand->siglock);
510 * do_acct_process does all actual work. Caller holds the reference to file.
512 static void do_acct_process(struct bsd_acct_struct *acct)
516 const struct cred *orig_cred;
517 struct pid_namespace *ns = acct->ns;
518 struct file *file = acct->file;
521 * Accounting records are not subject to resource limits.
523 flim = current->signal->rlim[RLIMIT_FSIZE].rlim_cur;
524 current->signal->rlim[RLIMIT_FSIZE].rlim_cur = RLIM_INFINITY;
525 /* Perform file operations on behalf of whoever enabled accounting */
526 orig_cred = override_creds(file->f_cred);
529 * First check to see if there is enough free_space to continue
530 * the process accounting system.
532 if (!check_free_space(acct))
536 /* we really need to bite the bullet and change layout */
537 ac.ac_uid = from_kuid_munged(file->f_cred->user_ns, orig_cred->uid);
538 ac.ac_gid = from_kgid_munged(file->f_cred->user_ns, orig_cred->gid);
539 #if ACCT_VERSION==1 || ACCT_VERSION==2
540 /* backward-compatible 16 bit fields */
541 ac.ac_uid16 = ac.ac_uid;
542 ac.ac_gid16 = ac.ac_gid;
545 ac.ac_pid = task_tgid_nr_ns(current, ns);
547 ac.ac_ppid = task_tgid_nr_ns(rcu_dereference(current->real_parent), ns);
551 * Get freeze protection. If the fs is frozen, just skip the write
552 * as we could deadlock the system otherwise.
554 if (file_start_write_trylock(file)) {
555 /* it's been opened O_APPEND, so position is irrelevant */
557 __kernel_write(file, (char *)&ac, sizeof(acct_t), &pos);
558 file_end_write(file);
561 current->signal->rlim[RLIMIT_FSIZE].rlim_cur = flim;
562 revert_creds(orig_cred);
566 * acct_collect - collect accounting information into pacct_struct
567 * @exitcode: task exit code
568 * @group_dead: not 0, if this thread is the last one in the process.
570 void acct_collect(long exitcode, int group_dead)
572 struct pacct_struct *pacct = ¤t->signal->pacct;
573 cputime_t utime, stime;
574 unsigned long vsize = 0;
576 if (group_dead && current->mm) {
577 struct vm_area_struct *vma;
578 down_read(¤t->mm->mmap_sem);
579 vma = current->mm->mmap;
581 vsize += vma->vm_end - vma->vm_start;
584 up_read(¤t->mm->mmap_sem);
587 spin_lock_irq(¤t->sighand->siglock);
589 pacct->ac_mem = vsize / 1024;
590 if (thread_group_leader(current)) {
591 pacct->ac_exitcode = exitcode;
592 if (current->flags & PF_FORKNOEXEC)
593 pacct->ac_flag |= AFORK;
595 if (current->flags & PF_SUPERPRIV)
596 pacct->ac_flag |= ASU;
597 if (current->flags & PF_DUMPCORE)
598 pacct->ac_flag |= ACORE;
599 if (current->flags & PF_SIGNALED)
600 pacct->ac_flag |= AXSIG;
601 task_cputime(current, &utime, &stime);
602 pacct->ac_utime += utime;
603 pacct->ac_stime += stime;
604 pacct->ac_minflt += current->min_flt;
605 pacct->ac_majflt += current->maj_flt;
606 spin_unlock_irq(¤t->sighand->siglock);
609 static void slow_acct_process(struct pid_namespace *ns)
611 for ( ; ns; ns = ns->parent) {
612 struct bsd_acct_struct *acct = acct_get(ns);
614 do_acct_process(acct);
615 mutex_unlock(&acct->lock);
624 * handles process accounting for an exiting task
626 void acct_process(void)
628 struct pid_namespace *ns;
631 * This loop is safe lockless, since current is still
632 * alive and holds its namespace, which in turn holds
635 for (ns = task_active_pid_ns(current); ns != NULL; ns = ns->parent) {
640 slow_acct_process(ns);