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1 // SPDX-License-Identifier: GPL-2.0
5 * BSD Process Accounting for Linux
7 * Author: Marco van Wieringen <mvw@planets.elm.net>
9 * Some code based on ideas and code from:
10 * Thomas K. Dyas <tdyas@eden.rutgers.edu>
12 * This file implements BSD-style process accounting. Whenever any
13 * process exits, an accounting record of type "struct acct" is
14 * written to the file specified with the acct() system call. It is
15 * up to user-level programs to do useful things with the accounting
16 * log. The kernel just provides the raw accounting information.
18 * (C) Copyright 1995 - 1997 Marco van Wieringen - ELM Consultancy B.V.
20 * Plugged two leaks. 1) It didn't return acct_file into the free_filps if
21 * the file happened to be read-only. 2) If the accounting was suspended
22 * due to the lack of space it happily allowed to reopen it and completely
23 * lost the old acct_file. 3/10/98, Al Viro.
25 * Now we silently close acct_file on attempt to reopen. Cleaned sys_acct().
26 * XTerms and EMACS are manifestations of pure evil. 21/10/98, AV.
28 * Fixed a nasty interaction with with sys_umount(). If the accointing
29 * was suspeneded we failed to stop it on umount(). Messy.
30 * Another one: remount to readonly didn't stop accounting.
31 * Question: what should we do if we have CAP_SYS_ADMIN but not
32 * CAP_SYS_PACCT? Current code does the following: umount returns -EBUSY
33 * unless we are messing with the root. In that case we are getting a
34 * real mess with do_remount_sb(). 9/11/98, AV.
36 * Fixed a bunch of races (and pair of leaks). Probably not the best way,
37 * but this one obviously doesn't introduce deadlocks. Later. BTW, found
38 * one race (and leak) in BSD implementation.
39 * OK, that's better. ANOTHER race and leak in BSD variant. There always
40 * is one more bug... 10/11/98, AV.
42 * Oh, fsck... Oopsable SMP race in do_process_acct() - we must hold
43 * ->mmap_sem to walk the vma list of current->mm. Nasty, since it leaks
44 * a struct file opened for write. Fixed. 2/6/2000, AV.
48 #include <linux/slab.h>
49 #include <linux/acct.h>
50 #include <linux/capability.h>
51 #include <linux/file.h>
52 #include <linux/tty.h>
53 #include <linux/security.h>
54 #include <linux/vfs.h>
55 #include <linux/jiffies.h>
56 #include <linux/times.h>
57 #include <linux/syscalls.h>
58 #include <linux/mount.h>
59 #include <linux/uaccess.h>
60 #include <linux/sched/cputime.h>
62 #include <asm/div64.h>
63 #include <linux/blkdev.h> /* sector_div */
64 #include <linux/pid_namespace.h>
65 #include <linux/fs_pin.h>
68 * These constants control the amount of freespace that suspend and
69 * resume the process accounting system, and the time delay between
71 * Turned into sysctl-controllable parameters. AV, 12/11/98
74 int acct_parm
[3] = {4, 2, 30};
75 #define RESUME (acct_parm[0]) /* >foo% free space - resume */
76 #define SUSPEND (acct_parm[1]) /* <foo% free space - suspend */
77 #define ACCT_TIMEOUT (acct_parm[2]) /* foo second timeout between checks */
80 * External references and all of the globals.
83 struct bsd_acct_struct
{
89 unsigned long needcheck
;
91 struct pid_namespace
*ns
;
92 struct work_struct work
;
93 struct completion done
;
96 static void do_acct_process(struct bsd_acct_struct
*acct
);
99 * Check the amount of free space and suspend/resume accordingly.
101 static int check_free_space(struct bsd_acct_struct
*acct
)
105 if (time_is_before_jiffies(acct
->needcheck
))
109 if (vfs_statfs(&acct
->file
->f_path
, &sbuf
))
113 u64 suspend
= sbuf
.f_blocks
* SUSPEND
;
114 do_div(suspend
, 100);
115 if (sbuf
.f_bavail
<= suspend
) {
117 pr_info("Process accounting paused\n");
120 u64 resume
= sbuf
.f_blocks
* RESUME
;
122 if (sbuf
.f_bavail
>= resume
) {
124 pr_info("Process accounting resumed\n");
128 acct
->needcheck
= jiffies
+ ACCT_TIMEOUT
*HZ
;
133 static void acct_put(struct bsd_acct_struct
*p
)
135 if (atomic_long_dec_and_test(&p
->count
))
139 static inline struct bsd_acct_struct
*to_acct(struct fs_pin
*p
)
141 return p
? container_of(p
, struct bsd_acct_struct
, pin
) : NULL
;
144 static struct bsd_acct_struct
*acct_get(struct pid_namespace
*ns
)
146 struct bsd_acct_struct
*res
;
150 res
= to_acct(READ_ONCE(ns
->bacct
));
155 if (!atomic_long_inc_not_zero(&res
->count
)) {
161 mutex_lock(&res
->lock
);
162 if (res
!= to_acct(READ_ONCE(ns
->bacct
))) {
163 mutex_unlock(&res
->lock
);
170 static void acct_pin_kill(struct fs_pin
*pin
)
172 struct bsd_acct_struct
*acct
= to_acct(pin
);
173 mutex_lock(&acct
->lock
);
174 do_acct_process(acct
);
175 schedule_work(&acct
->work
);
176 wait_for_completion(&acct
->done
);
177 cmpxchg(&acct
->ns
->bacct
, pin
, NULL
);
178 mutex_unlock(&acct
->lock
);
183 static void close_work(struct work_struct
*work
)
185 struct bsd_acct_struct
*acct
= container_of(work
, struct bsd_acct_struct
, work
);
186 struct file
*file
= acct
->file
;
187 if (file
->f_op
->flush
)
188 file
->f_op
->flush(file
, NULL
);
190 complete(&acct
->done
);
193 static int acct_on(struct filename
*pathname
)
196 struct vfsmount
*mnt
, *internal
;
197 struct pid_namespace
*ns
= task_active_pid_ns(current
);
198 struct bsd_acct_struct
*acct
;
202 acct
= kzalloc(sizeof(struct bsd_acct_struct
), GFP_KERNEL
);
206 /* Difference from BSD - they don't do O_APPEND */
207 file
= file_open_name(pathname
, O_WRONLY
|O_APPEND
|O_LARGEFILE
, 0);
210 return PTR_ERR(file
);
213 if (!S_ISREG(file_inode(file
)->i_mode
)) {
215 filp_close(file
, NULL
);
219 if (!(file
->f_mode
& FMODE_CAN_WRITE
)) {
221 filp_close(file
, NULL
);
224 internal
= mnt_clone_internal(&file
->f_path
);
225 if (IS_ERR(internal
)) {
227 filp_close(file
, NULL
);
228 return PTR_ERR(internal
);
230 err
= mnt_want_write(internal
);
234 filp_close(file
, NULL
);
237 mnt
= file
->f_path
.mnt
;
238 file
->f_path
.mnt
= internal
;
240 atomic_long_set(&acct
->count
, 1);
241 init_fs_pin(&acct
->pin
, acct_pin_kill
);
243 acct
->needcheck
= jiffies
;
245 mutex_init(&acct
->lock
);
246 INIT_WORK(&acct
->work
, close_work
);
247 init_completion(&acct
->done
);
248 mutex_lock_nested(&acct
->lock
, 1); /* nobody has seen it yet */
249 pin_insert(&acct
->pin
, mnt
);
252 old
= xchg(&ns
->bacct
, &acct
->pin
);
253 mutex_unlock(&acct
->lock
);
260 static DEFINE_MUTEX(acct_on_mutex
);
263 * sys_acct - enable/disable process accounting
264 * @name: file name for accounting records or NULL to shutdown accounting
266 * Returns 0 for success or negative errno values for failure.
268 * sys_acct() is the only system call needed to implement process
269 * accounting. It takes the name of the file where accounting records
270 * should be written. If the filename is NULL, accounting will be
273 SYSCALL_DEFINE1(acct
, const char __user
*, name
)
277 if (!capable(CAP_SYS_PACCT
))
281 struct filename
*tmp
= getname(name
);
285 mutex_lock(&acct_on_mutex
);
286 error
= acct_on(tmp
);
287 mutex_unlock(&acct_on_mutex
);
291 pin_kill(task_active_pid_ns(current
)->bacct
);
297 void acct_exit_ns(struct pid_namespace
*ns
)
304 * encode an unsigned long into a comp_t
306 * This routine has been adopted from the encode_comp_t() function in
307 * the kern_acct.c file of the FreeBSD operating system. The encoding
308 * is a 13-bit fraction with a 3-bit (base 8) exponent.
311 #define MANTSIZE 13 /* 13 bit mantissa. */
312 #define EXPSIZE 3 /* Base 8 (3 bit) exponent. */
313 #define MAXFRACT ((1 << MANTSIZE) - 1) /* Maximum fractional value. */
315 static comp_t
encode_comp_t(unsigned long value
)
320 while (value
> MAXFRACT
) {
321 rnd
= value
& (1 << (EXPSIZE
- 1)); /* Round up? */
322 value
>>= EXPSIZE
; /* Base 8 exponent == 3 bit shift. */
327 * If we need to round up, do it (and handle overflow correctly).
329 if (rnd
&& (++value
> MAXFRACT
)) {
335 * Clean it up and polish it off.
337 exp
<<= MANTSIZE
; /* Shift the exponent into place */
338 exp
+= value
; /* and add on the mantissa. */
342 #if ACCT_VERSION == 1 || ACCT_VERSION == 2
344 * encode an u64 into a comp2_t (24 bits)
346 * Format: 5 bit base 2 exponent, 20 bits mantissa.
347 * The leading bit of the mantissa is not stored, but implied for
348 * non-zero exponents.
349 * Largest encodable value is 50 bits.
352 #define MANTSIZE2 20 /* 20 bit mantissa. */
353 #define EXPSIZE2 5 /* 5 bit base 2 exponent. */
354 #define MAXFRACT2 ((1ul << MANTSIZE2) - 1) /* Maximum fractional value. */
355 #define MAXEXP2 ((1 << EXPSIZE2) - 1) /* Maximum exponent. */
357 static comp2_t
encode_comp2_t(u64 value
)
361 exp
= (value
> (MAXFRACT2
>>1));
363 while (value
> MAXFRACT2
) {
370 * If we need to round up, do it (and handle overflow correctly).
372 if (rnd
&& (++value
> MAXFRACT2
)) {
378 /* Overflow. Return largest representable number instead. */
379 return (1ul << (MANTSIZE2
+EXPSIZE2
-1)) - 1;
381 return (value
& (MAXFRACT2
>>1)) | (exp
<< (MANTSIZE2
-1));
386 #if ACCT_VERSION == 3
388 * encode an u64 into a 32 bit IEEE float
390 static u32
encode_float(u64 value
)
397 while ((s64
)value
> 0) {
401 u
= (u32
)(value
>> 40) & 0x7fffffu
;
402 return u
| (exp
<< 23);
407 * Write an accounting entry for an exiting process
409 * The acct_process() call is the workhorse of the process
410 * accounting system. The struct acct is built here and then written
411 * into the accounting file. This function should only be called from
412 * do_exit() or when switching to a different output file.
415 static void fill_ac(acct_t
*ac
)
417 struct pacct_struct
*pacct
= ¤t
->signal
->pacct
;
418 u64 elapsed
, run_time
;
419 struct tty_struct
*tty
;
422 * Fill the accounting struct with the needed info as recorded
423 * by the different kernel functions.
425 memset(ac
, 0, sizeof(acct_t
));
427 ac
->ac_version
= ACCT_VERSION
| ACCT_BYTEORDER
;
428 strlcpy(ac
->ac_comm
, current
->comm
, sizeof(ac
->ac_comm
));
430 /* calculate run_time in nsec*/
431 run_time
= ktime_get_ns();
432 run_time
-= current
->group_leader
->start_time
;
433 /* convert nsec -> AHZ */
434 elapsed
= nsec_to_AHZ(run_time
);
435 #if ACCT_VERSION == 3
436 ac
->ac_etime
= encode_float(elapsed
);
438 ac
->ac_etime
= encode_comp_t(elapsed
< (unsigned long) -1l ?
439 (unsigned long) elapsed
: (unsigned long) -1l);
441 #if ACCT_VERSION == 1 || ACCT_VERSION == 2
443 /* new enlarged etime field */
444 comp2_t etime
= encode_comp2_t(elapsed
);
446 ac
->ac_etime_hi
= etime
>> 16;
447 ac
->ac_etime_lo
= (u16
) etime
;
450 do_div(elapsed
, AHZ
);
451 ac
->ac_btime
= get_seconds() - elapsed
;
456 spin_lock_irq(¤t
->sighand
->siglock
);
457 tty
= current
->signal
->tty
; /* Safe as we hold the siglock */
458 ac
->ac_tty
= tty
? old_encode_dev(tty_devnum(tty
)) : 0;
459 ac
->ac_utime
= encode_comp_t(nsec_to_AHZ(pacct
->ac_utime
));
460 ac
->ac_stime
= encode_comp_t(nsec_to_AHZ(pacct
->ac_stime
));
461 ac
->ac_flag
= pacct
->ac_flag
;
462 ac
->ac_mem
= encode_comp_t(pacct
->ac_mem
);
463 ac
->ac_minflt
= encode_comp_t(pacct
->ac_minflt
);
464 ac
->ac_majflt
= encode_comp_t(pacct
->ac_majflt
);
465 ac
->ac_exitcode
= pacct
->ac_exitcode
;
466 spin_unlock_irq(¤t
->sighand
->siglock
);
469 * do_acct_process does all actual work. Caller holds the reference to file.
471 static void do_acct_process(struct bsd_acct_struct
*acct
)
475 const struct cred
*orig_cred
;
476 struct file
*file
= acct
->file
;
479 * Accounting records are not subject to resource limits.
481 flim
= current
->signal
->rlim
[RLIMIT_FSIZE
].rlim_cur
;
482 current
->signal
->rlim
[RLIMIT_FSIZE
].rlim_cur
= RLIM_INFINITY
;
483 /* Perform file operations on behalf of whoever enabled accounting */
484 orig_cred
= override_creds(file
->f_cred
);
487 * First check to see if there is enough free_space to continue
488 * the process accounting system.
490 if (!check_free_space(acct
))
494 /* we really need to bite the bullet and change layout */
495 ac
.ac_uid
= from_kuid_munged(file
->f_cred
->user_ns
, orig_cred
->uid
);
496 ac
.ac_gid
= from_kgid_munged(file
->f_cred
->user_ns
, orig_cred
->gid
);
497 #if ACCT_VERSION == 1 || ACCT_VERSION == 2
498 /* backward-compatible 16 bit fields */
499 ac
.ac_uid16
= ac
.ac_uid
;
500 ac
.ac_gid16
= ac
.ac_gid
;
502 #if ACCT_VERSION == 3
504 struct pid_namespace
*ns
= acct
->ns
;
506 ac
.ac_pid
= task_tgid_nr_ns(current
, ns
);
508 ac
.ac_ppid
= task_tgid_nr_ns(rcu_dereference(current
->real_parent
),
514 * Get freeze protection. If the fs is frozen, just skip the write
515 * as we could deadlock the system otherwise.
517 if (file_start_write_trylock(file
)) {
518 /* it's been opened O_APPEND, so position is irrelevant */
520 __kernel_write(file
, &ac
, sizeof(acct_t
), &pos
);
521 file_end_write(file
);
524 current
->signal
->rlim
[RLIMIT_FSIZE
].rlim_cur
= flim
;
525 revert_creds(orig_cred
);
529 * acct_collect - collect accounting information into pacct_struct
530 * @exitcode: task exit code
531 * @group_dead: not 0, if this thread is the last one in the process.
533 void acct_collect(long exitcode
, int group_dead
)
535 struct pacct_struct
*pacct
= ¤t
->signal
->pacct
;
537 unsigned long vsize
= 0;
539 if (group_dead
&& current
->mm
) {
540 struct vm_area_struct
*vma
;
542 down_read(¤t
->mm
->mmap_sem
);
543 vma
= current
->mm
->mmap
;
545 vsize
+= vma
->vm_end
- vma
->vm_start
;
548 up_read(¤t
->mm
->mmap_sem
);
551 spin_lock_irq(¤t
->sighand
->siglock
);
553 pacct
->ac_mem
= vsize
/ 1024;
554 if (thread_group_leader(current
)) {
555 pacct
->ac_exitcode
= exitcode
;
556 if (current
->flags
& PF_FORKNOEXEC
)
557 pacct
->ac_flag
|= AFORK
;
559 if (current
->flags
& PF_SUPERPRIV
)
560 pacct
->ac_flag
|= ASU
;
561 if (current
->flags
& PF_DUMPCORE
)
562 pacct
->ac_flag
|= ACORE
;
563 if (current
->flags
& PF_SIGNALED
)
564 pacct
->ac_flag
|= AXSIG
;
566 task_cputime(current
, &utime
, &stime
);
567 pacct
->ac_utime
+= utime
;
568 pacct
->ac_stime
+= stime
;
569 pacct
->ac_minflt
+= current
->min_flt
;
570 pacct
->ac_majflt
+= current
->maj_flt
;
571 spin_unlock_irq(¤t
->sighand
->siglock
);
574 static void slow_acct_process(struct pid_namespace
*ns
)
576 for ( ; ns
; ns
= ns
->parent
) {
577 struct bsd_acct_struct
*acct
= acct_get(ns
);
579 do_acct_process(acct
);
580 mutex_unlock(&acct
->lock
);
589 * handles process accounting for an exiting task
591 void acct_process(void)
593 struct pid_namespace
*ns
;
596 * This loop is safe lockless, since current is still
597 * alive and holds its namespace, which in turn holds
600 for (ns
= task_active_pid_ns(current
); ns
!= NULL
; ns
= ns
->parent
) {
605 slow_acct_process(ns
);