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
{
83 struct hlist_node s_list
;
84 struct hlist_node m_list
;
87 unsigned long needcheck
;
89 struct pid_namespace
*ns
;
92 static DEFINE_SPINLOCK(acct_lock
);
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 printk(KERN_INFO
"Process accounting paused\n");
116 u64 resume
= sbuf
.f_blocks
* RESUME
;
118 if (sbuf
.f_bavail
>= resume
) {
120 printk(KERN_INFO
"Process accounting resumed\n");
124 acct
->needcheck
= jiffies
+ ACCT_TIMEOUT
*HZ
;
129 static void acct_put(struct bsd_acct_struct
*p
)
131 spin_lock(&acct_lock
);
134 spin_unlock(&acct_lock
);
137 static struct bsd_acct_struct
*__acct_get(struct bsd_acct_struct
*res
)
140 spin_unlock(&acct_lock
);
141 mutex_lock(&res
->lock
);
143 mutex_unlock(&res
->lock
);
144 spin_lock(&acct_lock
);
152 static struct bsd_acct_struct
*acct_get(struct pid_namespace
*ns
)
154 struct bsd_acct_struct
*res
;
155 spin_lock(&acct_lock
);
158 spin_unlock(&acct_lock
);
161 res
= __acct_get(ns
->bacct
);
167 static void acct_kill(struct bsd_acct_struct
*acct
,
168 struct bsd_acct_struct
*new)
171 struct file
*file
= acct
->file
;
172 struct pid_namespace
*ns
= acct
->ns
;
173 spin_lock(&acct_lock
);
174 hlist_del(&acct
->m_list
);
175 hlist_del(&acct
->s_list
);
176 mnt_unpin(file
->f_path
.mnt
);
177 spin_unlock(&acct_lock
);
178 do_acct_process(acct
);
179 filp_close(file
, NULL
);
180 spin_lock(&acct_lock
);
183 struct vfsmount
*m
= new->file
->f_path
.mnt
;
185 hlist_add_head(&new->s_list
, &m
->mnt_sb
->s_pins
);
186 hlist_add_head(&new->m_list
, &real_mount(m
)->mnt_pins
);
189 mutex_unlock(&acct
->lock
);
190 if (!(acct
->count
-= 2))
192 spin_unlock(&acct_lock
);
196 static int acct_on(struct filename
*pathname
)
199 struct vfsmount
*mnt
;
200 struct pid_namespace
*ns
= task_active_pid_ns(current
);
201 struct bsd_acct_struct
*acct
, *old
;
203 acct
= kzalloc(sizeof(struct bsd_acct_struct
), GFP_KERNEL
);
207 /* Difference from BSD - they don't do O_APPEND */
208 file
= file_open_name(pathname
, O_WRONLY
|O_APPEND
|O_LARGEFILE
, 0);
211 return PTR_ERR(file
);
214 if (!S_ISREG(file_inode(file
)->i_mode
)) {
216 filp_close(file
, NULL
);
220 if (!file
->f_op
->write
) {
222 filp_close(file
, NULL
);
228 acct
->needcheck
= jiffies
;
230 mutex_init(&acct
->lock
);
231 mnt
= file
->f_path
.mnt
;
235 acct_kill(old
, acct
);
237 spin_lock(&acct_lock
);
240 hlist_add_head(&acct
->s_list
, &mnt
->mnt_sb
->s_pins
);
241 hlist_add_head(&acct
->m_list
, &real_mount(mnt
)->mnt_pins
);
242 spin_unlock(&acct_lock
);
244 mntput(mnt
); /* it's pinned, now give up active reference */
248 static DEFINE_MUTEX(acct_on_mutex
);
251 * sys_acct - enable/disable process accounting
252 * @name: file name for accounting records or NULL to shutdown accounting
254 * Returns 0 for success or negative errno values for failure.
256 * sys_acct() is the only system call needed to implement process
257 * accounting. It takes the name of the file where accounting records
258 * should be written. If the filename is NULL, accounting will be
261 SYSCALL_DEFINE1(acct
, const char __user
*, name
)
265 if (!capable(CAP_SYS_PACCT
))
269 struct filename
*tmp
= getname(name
);
272 mutex_lock(&acct_on_mutex
);
273 error
= acct_on(tmp
);
274 mutex_unlock(&acct_on_mutex
);
277 acct_kill(acct_get(task_active_pid_ns(current
)), NULL
);
283 void acct_auto_close_mnt(struct hlist_head
*list
)
286 spin_lock(&acct_lock
);
289 acct_kill(__acct_get(hlist_entry(list
->first
,
290 struct bsd_acct_struct
,
293 spin_unlock(&acct_lock
);
296 void acct_auto_close(struct hlist_head
*list
)
299 spin_lock(&acct_lock
);
302 acct_kill(__acct_get(hlist_entry(list
->first
,
303 struct bsd_acct_struct
,
306 spin_unlock(&acct_lock
);
309 void acct_exit_ns(struct pid_namespace
*ns
)
311 acct_kill(acct_get(ns
), NULL
);
315 * encode an unsigned long into a comp_t
317 * This routine has been adopted from the encode_comp_t() function in
318 * the kern_acct.c file of the FreeBSD operating system. The encoding
319 * is a 13-bit fraction with a 3-bit (base 8) exponent.
322 #define MANTSIZE 13 /* 13 bit mantissa. */
323 #define EXPSIZE 3 /* Base 8 (3 bit) exponent. */
324 #define MAXFRACT ((1 << MANTSIZE) - 1) /* Maximum fractional value. */
326 static comp_t
encode_comp_t(unsigned long value
)
331 while (value
> MAXFRACT
) {
332 rnd
= value
& (1 << (EXPSIZE
- 1)); /* Round up? */
333 value
>>= EXPSIZE
; /* Base 8 exponent == 3 bit shift. */
338 * If we need to round up, do it (and handle overflow correctly).
340 if (rnd
&& (++value
> MAXFRACT
)) {
346 * Clean it up and polish it off.
348 exp
<<= MANTSIZE
; /* Shift the exponent into place */
349 exp
+= value
; /* and add on the mantissa. */
353 #if ACCT_VERSION==1 || ACCT_VERSION==2
355 * encode an u64 into a comp2_t (24 bits)
357 * Format: 5 bit base 2 exponent, 20 bits mantissa.
358 * The leading bit of the mantissa is not stored, but implied for
359 * non-zero exponents.
360 * Largest encodable value is 50 bits.
363 #define MANTSIZE2 20 /* 20 bit mantissa. */
364 #define EXPSIZE2 5 /* 5 bit base 2 exponent. */
365 #define MAXFRACT2 ((1ul << MANTSIZE2) - 1) /* Maximum fractional value. */
366 #define MAXEXP2 ((1 <<EXPSIZE2) - 1) /* Maximum exponent. */
368 static comp2_t
encode_comp2_t(u64 value
)
372 exp
= (value
> (MAXFRACT2
>>1));
374 while (value
> MAXFRACT2
) {
381 * If we need to round up, do it (and handle overflow correctly).
383 if (rnd
&& (++value
> MAXFRACT2
)) {
389 /* Overflow. Return largest representable number instead. */
390 return (1ul << (MANTSIZE2
+EXPSIZE2
-1)) - 1;
392 return (value
& (MAXFRACT2
>>1)) | (exp
<< (MANTSIZE2
-1));
399 * encode an u64 into a 32 bit IEEE float
401 static u32
encode_float(u64 value
)
406 if (value
==0) return 0;
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
);
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
);
455 ac
->ac_etime_hi
= etime
>> 16;
456 ac
->ac_etime_lo
= (u16
) etime
;
459 do_div(elapsed
, AHZ
);
460 ac
->ac_btime
= get_seconds() - elapsed
;
465 spin_lock_irq(¤t
->sighand
->siglock
);
466 tty
= current
->signal
->tty
; /* Safe as we hold the siglock */
467 ac
->ac_tty
= tty
? old_encode_dev(tty_devnum(tty
)) : 0;
468 ac
->ac_utime
= encode_comp_t(jiffies_to_AHZ(cputime_to_jiffies(pacct
->ac_utime
)));
469 ac
->ac_stime
= encode_comp_t(jiffies_to_AHZ(cputime_to_jiffies(pacct
->ac_stime
)));
470 ac
->ac_flag
= pacct
->ac_flag
;
471 ac
->ac_mem
= encode_comp_t(pacct
->ac_mem
);
472 ac
->ac_minflt
= encode_comp_t(pacct
->ac_minflt
);
473 ac
->ac_majflt
= encode_comp_t(pacct
->ac_majflt
);
474 ac
->ac_exitcode
= pacct
->ac_exitcode
;
475 spin_unlock_irq(¤t
->sighand
->siglock
);
478 * do_acct_process does all actual work. Caller holds the reference to file.
480 static void do_acct_process(struct bsd_acct_struct
*acct
)
484 const struct cred
*orig_cred
;
485 struct pid_namespace
*ns
= acct
->ns
;
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
;
513 ac
.ac_pid
= task_tgid_nr_ns(current
, ns
);
515 ac
.ac_ppid
= task_tgid_nr_ns(rcu_dereference(current
->real_parent
), ns
);
519 * Get freeze protection. If the fs is frozen, just skip the write
520 * as we could deadlock the system otherwise.
522 if (file_start_write_trylock(file
)) {
523 /* it's been opened O_APPEND, so position is irrelevant */
525 __kernel_write(file
, (char *)&ac
, sizeof(acct_t
), &pos
);
526 file_end_write(file
);
529 current
->signal
->rlim
[RLIMIT_FSIZE
].rlim_cur
= flim
;
530 revert_creds(orig_cred
);
534 * acct_collect - collect accounting information into pacct_struct
535 * @exitcode: task exit code
536 * @group_dead: not 0, if this thread is the last one in the process.
538 void acct_collect(long exitcode
, int group_dead
)
540 struct pacct_struct
*pacct
= ¤t
->signal
->pacct
;
541 cputime_t utime
, stime
;
542 unsigned long vsize
= 0;
544 if (group_dead
&& current
->mm
) {
545 struct vm_area_struct
*vma
;
546 down_read(¤t
->mm
->mmap_sem
);
547 vma
= current
->mm
->mmap
;
549 vsize
+= vma
->vm_end
- vma
->vm_start
;
552 up_read(¤t
->mm
->mmap_sem
);
555 spin_lock_irq(¤t
->sighand
->siglock
);
557 pacct
->ac_mem
= vsize
/ 1024;
558 if (thread_group_leader(current
)) {
559 pacct
->ac_exitcode
= exitcode
;
560 if (current
->flags
& PF_FORKNOEXEC
)
561 pacct
->ac_flag
|= AFORK
;
563 if (current
->flags
& PF_SUPERPRIV
)
564 pacct
->ac_flag
|= ASU
;
565 if (current
->flags
& PF_DUMPCORE
)
566 pacct
->ac_flag
|= ACORE
;
567 if (current
->flags
& PF_SIGNALED
)
568 pacct
->ac_flag
|= AXSIG
;
569 task_cputime(current
, &utime
, &stime
);
570 pacct
->ac_utime
+= utime
;
571 pacct
->ac_stime
+= stime
;
572 pacct
->ac_minflt
+= current
->min_flt
;
573 pacct
->ac_majflt
+= current
->maj_flt
;
574 spin_unlock_irq(¤t
->sighand
->siglock
);
577 static void slow_acct_process(struct pid_namespace
*ns
)
579 for ( ; ns
; ns
= ns
->parent
) {
580 struct bsd_acct_struct
*acct
= acct_get(ns
);
582 do_acct_process(acct
);
583 mutex_unlock(&acct
->lock
);
592 * handles process accounting for an exiting task
594 void acct_process(void)
596 struct pid_namespace
*ns
;
599 * This loop is safe lockless, since current is still
600 * alive and holds its namespace, which in turn holds
603 for (ns
= task_active_pid_ns(current
); ns
!= NULL
; ns
= ns
->parent
) {
608 slow_acct_process(ns
);
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