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

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