Root/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 <asm/uaccess.h>
59#include <asm/div64.h>
60#include <linux/blkdev.h> /* sector_div */
61#include <linux/pid_namespace.h>
62
63/*
64 * These constants control the amount of freespace that suspend and
65 * resume the process accounting system, and the time delay between
66 * each check.
67 * Turned into sysctl-controllable parameters. AV, 12/11/98
68 */
69
70int acct_parm[3] = {4, 2, 30};
71#define RESUME (acct_parm[0]) /* >foo% free space - resume */
72#define SUSPEND (acct_parm[1]) /* <foo% free space - suspend */
73#define ACCT_TIMEOUT (acct_parm[2]) /* foo second timeout between checks */
74
75/*
76 * External references and all of the globals.
77 */
78static void do_acct_process(struct bsd_acct_struct *acct,
79        struct pid_namespace *ns, struct file *);
80
81/*
82 * This structure is used so that all the data protected by lock
83 * can be placed in the same cache line as the lock. This primes
84 * the cache line to have the data after getting the lock.
85 */
86struct bsd_acct_struct {
87    volatile int active;
88    volatile int needcheck;
89    struct file *file;
90    struct pid_namespace *ns;
91    struct timer_list timer;
92    struct list_head list;
93};
94
95static DEFINE_SPINLOCK(acct_lock);
96static LIST_HEAD(acct_list);
97
98/*
99 * Called whenever the timer says to check the free space.
100 */
101static void acct_timeout(unsigned long x)
102{
103    struct bsd_acct_struct *acct = (struct bsd_acct_struct *)x;
104    acct->needcheck = 1;
105}
106
107/*
108 * Check the amount of free space and suspend/resume accordingly.
109 */
110static int check_free_space(struct bsd_acct_struct *acct, struct file *file)
111{
112    struct kstatfs sbuf;
113    int res;
114    int act;
115    sector_t resume;
116    sector_t suspend;
117
118    spin_lock(&acct_lock);
119    res = acct->active;
120    if (!file || !acct->needcheck)
121        goto out;
122    spin_unlock(&acct_lock);
123
124    /* May block */
125    if (vfs_statfs(file->f_path.dentry, &sbuf))
126        return res;
127    suspend = sbuf.f_blocks * SUSPEND;
128    resume = sbuf.f_blocks * RESUME;
129
130    sector_div(suspend, 100);
131    sector_div(resume, 100);
132
133    if (sbuf.f_bavail <= suspend)
134        act = -1;
135    else if (sbuf.f_bavail >= resume)
136        act = 1;
137    else
138        act = 0;
139
140    /*
141     * If some joker switched acct->file under us we'ld better be
142     * silent and _not_ touch anything.
143     */
144    spin_lock(&acct_lock);
145    if (file != acct->file) {
146        if (act)
147            res = act>0;
148        goto out;
149    }
150
151    if (acct->active) {
152        if (act < 0) {
153            acct->active = 0;
154            printk(KERN_INFO "Process accounting paused\n");
155        }
156    } else {
157        if (act > 0) {
158            acct->active = 1;
159            printk(KERN_INFO "Process accounting resumed\n");
160        }
161    }
162
163    del_timer(&acct->timer);
164    acct->needcheck = 0;
165    acct->timer.expires = jiffies + ACCT_TIMEOUT*HZ;
166    add_timer(&acct->timer);
167    res = acct->active;
168out:
169    spin_unlock(&acct_lock);
170    return res;
171}
172
173/*
174 * Close the old accounting file (if currently open) and then replace
175 * it with file (if non-NULL).
176 *
177 * NOTE: acct_lock MUST be held on entry and exit.
178 */
179static void acct_file_reopen(struct bsd_acct_struct *acct, struct file *file,
180        struct pid_namespace *ns)
181{
182    struct file *old_acct = NULL;
183    struct pid_namespace *old_ns = NULL;
184
185    if (acct->file) {
186        old_acct = acct->file;
187        old_ns = acct->ns;
188        del_timer(&acct->timer);
189        acct->active = 0;
190        acct->needcheck = 0;
191        acct->file = NULL;
192        acct->ns = NULL;
193        list_del(&acct->list);
194    }
195    if (file) {
196        acct->file = file;
197        acct->ns = ns;
198        acct->needcheck = 0;
199        acct->active = 1;
200        list_add(&acct->list, &acct_list);
201        /* It's been deleted if it was used before so this is safe */
202        setup_timer(&acct->timer, acct_timeout, (unsigned long)acct);
203        acct->timer.expires = jiffies + ACCT_TIMEOUT*HZ;
204        add_timer(&acct->timer);
205    }
206    if (old_acct) {
207        mnt_unpin(old_acct->f_path.mnt);
208        spin_unlock(&acct_lock);
209        do_acct_process(acct, old_ns, old_acct);
210        filp_close(old_acct, NULL);
211        spin_lock(&acct_lock);
212    }
213}
214
215static int acct_on(char *name)
216{
217    struct file *file;
218    struct vfsmount *mnt;
219    int error;
220    struct pid_namespace *ns;
221    struct bsd_acct_struct *acct = NULL;
222
223    /* Difference from BSD - they don't do O_APPEND */
224    file = filp_open(name, O_WRONLY|O_APPEND|O_LARGEFILE, 0);
225    if (IS_ERR(file))
226        return PTR_ERR(file);
227
228    if (!S_ISREG(file->f_path.dentry->d_inode->i_mode)) {
229        filp_close(file, NULL);
230        return -EACCES;
231    }
232
233    if (!file->f_op->write) {
234        filp_close(file, NULL);
235        return -EIO;
236    }
237
238    ns = task_active_pid_ns(current);
239    if (ns->bacct == NULL) {
240        acct = kzalloc(sizeof(struct bsd_acct_struct), GFP_KERNEL);
241        if (acct == NULL) {
242            filp_close(file, NULL);
243            return -ENOMEM;
244        }
245    }
246
247    error = security_acct(file);
248    if (error) {
249        kfree(acct);
250        filp_close(file, NULL);
251        return error;
252    }
253
254    spin_lock(&acct_lock);
255    if (ns->bacct == NULL) {
256        ns->bacct = acct;
257        acct = NULL;
258    }
259
260    mnt = file->f_path.mnt;
261    mnt_pin(mnt);
262    acct_file_reopen(ns->bacct, file, ns);
263    spin_unlock(&acct_lock);
264
265    mntput(mnt); /* it's pinned, now give up active reference */
266    kfree(acct);
267
268    return 0;
269}
270
271/**
272 * sys_acct - enable/disable process accounting
273 * @name: file name for accounting records or NULL to shutdown accounting
274 *
275 * Returns 0 for success or negative errno values for failure.
276 *
277 * sys_acct() is the only system call needed to implement process
278 * accounting. It takes the name of the file where accounting records
279 * should be written. If the filename is NULL, accounting will be
280 * shutdown.
281 */
282SYSCALL_DEFINE1(acct, const char __user *, name)
283{
284    int error;
285
286    if (!capable(CAP_SYS_PACCT))
287        return -EPERM;
288
289    if (name) {
290        char *tmp = getname(name);
291        if (IS_ERR(tmp))
292            return (PTR_ERR(tmp));
293        error = acct_on(tmp);
294        putname(tmp);
295    } else {
296        struct bsd_acct_struct *acct;
297
298        acct = task_active_pid_ns(current)->bacct;
299        if (acct == NULL)
300            return 0;
301
302        error = security_acct(NULL);
303        if (!error) {
304            spin_lock(&acct_lock);
305            acct_file_reopen(acct, NULL, NULL);
306            spin_unlock(&acct_lock);
307        }
308    }
309    return error;
310}
311
312/**
313 * acct_auto_close - turn off a filesystem's accounting if it is on
314 * @m: vfsmount being shut down
315 *
316 * If the accounting is turned on for a file in the subtree pointed to
317 * to by m, turn accounting off. Done when m is about to die.
318 */
319void acct_auto_close_mnt(struct vfsmount *m)
320{
321    struct bsd_acct_struct *acct;
322
323    spin_lock(&acct_lock);
324restart:
325    list_for_each_entry(acct, &acct_list, list)
326        if (acct->file && acct->file->f_path.mnt == m) {
327            acct_file_reopen(acct, NULL, NULL);
328            goto restart;
329        }
330    spin_unlock(&acct_lock);
331}
332
333/**
334 * acct_auto_close - turn off a filesystem's accounting if it is on
335 * @sb: super block for the filesystem
336 *
337 * If the accounting is turned on for a file in the filesystem pointed
338 * to by sb, turn accounting off.
339 */
340void acct_auto_close(struct super_block *sb)
341{
342    struct bsd_acct_struct *acct;
343
344    spin_lock(&acct_lock);
345restart:
346    list_for_each_entry(acct, &acct_list, list)
347        if (acct->file && acct->file->f_path.mnt->mnt_sb == sb) {
348            acct_file_reopen(acct, NULL, NULL);
349            goto restart;
350        }
351    spin_unlock(&acct_lock);
352}
353
354void acct_exit_ns(struct pid_namespace *ns)
355{
356    struct bsd_acct_struct *acct;
357
358    spin_lock(&acct_lock);
359    acct = ns->bacct;
360    if (acct != NULL) {
361        if (acct->file != NULL)
362            acct_file_reopen(acct, NULL, NULL);
363
364        kfree(acct);
365    }
366    spin_unlock(&acct_lock);
367}
368
369/*
370 * encode an unsigned long into a comp_t
371 *
372 * This routine has been adopted from the encode_comp_t() function in
373 * the kern_acct.c file of the FreeBSD operating system. The encoding
374 * is a 13-bit fraction with a 3-bit (base 8) exponent.
375 */
376
377#define MANTSIZE 13 /* 13 bit mantissa. */
378#define EXPSIZE 3 /* Base 8 (3 bit) exponent. */
379#define MAXFRACT ((1 << MANTSIZE) - 1) /* Maximum fractional value. */
380
381static comp_t encode_comp_t(unsigned long value)
382{
383    int exp, rnd;
384
385    exp = rnd = 0;
386    while (value > MAXFRACT) {
387        rnd = value & (1 << (EXPSIZE - 1)); /* Round up? */
388        value >>= EXPSIZE; /* Base 8 exponent == 3 bit shift. */
389        exp++;
390    }
391
392    /*
393     * If we need to round up, do it (and handle overflow correctly).
394     */
395    if (rnd && (++value > MAXFRACT)) {
396        value >>= EXPSIZE;
397        exp++;
398    }
399
400    /*
401     * Clean it up and polish it off.
402     */
403    exp <<= MANTSIZE; /* Shift the exponent into place */
404    exp += value; /* and add on the mantissa. */
405    return exp;
406}
407
408#if ACCT_VERSION==1 || ACCT_VERSION==2
409/*
410 * encode an u64 into a comp2_t (24 bits)
411 *
412 * Format: 5 bit base 2 exponent, 20 bits mantissa.
413 * The leading bit of the mantissa is not stored, but implied for
414 * non-zero exponents.
415 * Largest encodable value is 50 bits.
416 */
417
418#define MANTSIZE2 20 /* 20 bit mantissa. */
419#define EXPSIZE2 5 /* 5 bit base 2 exponent. */
420#define MAXFRACT2 ((1ul << MANTSIZE2) - 1) /* Maximum fractional value. */
421#define MAXEXP2 ((1 <<EXPSIZE2) - 1) /* Maximum exponent. */
422
423static comp2_t encode_comp2_t(u64 value)
424{
425    int exp, rnd;
426
427    exp = (value > (MAXFRACT2>>1));
428    rnd = 0;
429    while (value > MAXFRACT2) {
430        rnd = value & 1;
431        value >>= 1;
432        exp++;
433    }
434
435    /*
436     * If we need to round up, do it (and handle overflow correctly).
437     */
438    if (rnd && (++value > MAXFRACT2)) {
439        value >>= 1;
440        exp++;
441    }
442
443    if (exp > MAXEXP2) {
444        /* Overflow. Return largest representable number instead. */
445        return (1ul << (MANTSIZE2+EXPSIZE2-1)) - 1;
446    } else {
447        return (value & (MAXFRACT2>>1)) | (exp << (MANTSIZE2-1));
448    }
449}
450#endif
451
452#if ACCT_VERSION==3
453/*
454 * encode an u64 into a 32 bit IEEE float
455 */
456static u32 encode_float(u64 value)
457{
458    unsigned exp = 190;
459    unsigned u;
460
461    if (value==0) return 0;
462    while ((s64)value > 0){
463        value <<= 1;
464        exp--;
465    }
466    u = (u32)(value >> 40) & 0x7fffffu;
467    return u | (exp << 23);
468}
469#endif
470
471/*
472 * Write an accounting entry for an exiting process
473 *
474 * The acct_process() call is the workhorse of the process
475 * accounting system. The struct acct is built here and then written
476 * into the accounting file. This function should only be called from
477 * do_exit() or when switching to a different output file.
478 */
479
480/*
481 * do_acct_process does all actual work. Caller holds the reference to file.
482 */
483static void do_acct_process(struct bsd_acct_struct *acct,
484        struct pid_namespace *ns, struct file *file)
485{
486    struct pacct_struct *pacct = &current->signal->pacct;
487    acct_t ac;
488    mm_segment_t fs;
489    unsigned long flim;
490    u64 elapsed;
491    u64 run_time;
492    struct timespec uptime;
493    struct tty_struct *tty;
494    const struct cred *orig_cred;
495
496    /* Perform file operations on behalf of whoever enabled accounting */
497    orig_cred = override_creds(file->f_cred);
498
499    /*
500     * First check to see if there is enough free_space to continue
501     * the process accounting system.
502     */
503    if (!check_free_space(acct, file))
504        goto out;
505
506    /*
507     * Fill the accounting struct with the needed info as recorded
508     * by the different kernel functions.
509     */
510    memset((caddr_t)&ac, 0, sizeof(acct_t));
511
512    ac.ac_version = ACCT_VERSION | ACCT_BYTEORDER;
513    strlcpy(ac.ac_comm, current->comm, sizeof(ac.ac_comm));
514
515    /* calculate run_time in nsec*/
516    do_posix_clock_monotonic_gettime(&uptime);
517    run_time = (u64)uptime.tv_sec*NSEC_PER_SEC + uptime.tv_nsec;
518    run_time -= (u64)current->group_leader->start_time.tv_sec * NSEC_PER_SEC
519               + current->group_leader->start_time.tv_nsec;
520    /* convert nsec -> AHZ */
521    elapsed = nsec_to_AHZ(run_time);
522#if ACCT_VERSION==3
523    ac.ac_etime = encode_float(elapsed);
524#else
525    ac.ac_etime = encode_comp_t(elapsed < (unsigned long) -1l ?
526                           (unsigned long) elapsed : (unsigned long) -1l);
527#endif
528#if ACCT_VERSION==1 || ACCT_VERSION==2
529    {
530        /* new enlarged etime field */
531        comp2_t etime = encode_comp2_t(elapsed);
532        ac.ac_etime_hi = etime >> 16;
533        ac.ac_etime_lo = (u16) etime;
534    }
535#endif
536    do_div(elapsed, AHZ);
537    ac.ac_btime = get_seconds() - elapsed;
538    /* we really need to bite the bullet and change layout */
539    ac.ac_uid = orig_cred->uid;
540    ac.ac_gid = orig_cred->gid;
541#if ACCT_VERSION==2
542    ac.ac_ahz = AHZ;
543#endif
544#if ACCT_VERSION==1 || ACCT_VERSION==2
545    /* backward-compatible 16 bit fields */
546    ac.ac_uid16 = ac.ac_uid;
547    ac.ac_gid16 = ac.ac_gid;
548#endif
549#if ACCT_VERSION==3
550    ac.ac_pid = task_tgid_nr_ns(current, ns);
551    rcu_read_lock();
552    ac.ac_ppid = task_tgid_nr_ns(rcu_dereference(current->real_parent), ns);
553    rcu_read_unlock();
554#endif
555
556    spin_lock_irq(&current->sighand->siglock);
557    tty = current->signal->tty; /* Safe as we hold the siglock */
558    ac.ac_tty = tty ? old_encode_dev(tty_devnum(tty)) : 0;
559    ac.ac_utime = encode_comp_t(jiffies_to_AHZ(cputime_to_jiffies(pacct->ac_utime)));
560    ac.ac_stime = encode_comp_t(jiffies_to_AHZ(cputime_to_jiffies(pacct->ac_stime)));
561    ac.ac_flag = pacct->ac_flag;
562    ac.ac_mem = encode_comp_t(pacct->ac_mem);
563    ac.ac_minflt = encode_comp_t(pacct->ac_minflt);
564    ac.ac_majflt = encode_comp_t(pacct->ac_majflt);
565    ac.ac_exitcode = pacct->ac_exitcode;
566    spin_unlock_irq(&current->sighand->siglock);
567    ac.ac_io = encode_comp_t(0 /* current->io_usage */); /* %% */
568    ac.ac_rw = encode_comp_t(ac.ac_io / 1024);
569    ac.ac_swaps = encode_comp_t(0);
570
571    /*
572     * Kernel segment override to datasegment and write it
573     * to the accounting file.
574     */
575    fs = get_fs();
576    set_fs(KERNEL_DS);
577    /*
578     * Accounting records are not subject to resource limits.
579     */
580    flim = current->signal->rlim[RLIMIT_FSIZE].rlim_cur;
581    current->signal->rlim[RLIMIT_FSIZE].rlim_cur = RLIM_INFINITY;
582    file->f_op->write(file, (char *)&ac,
583                   sizeof(acct_t), &file->f_pos);
584    current->signal->rlim[RLIMIT_FSIZE].rlim_cur = flim;
585    set_fs(fs);
586out:
587    revert_creds(orig_cred);
588}
589
590/**
591 * acct_init_pacct - initialize a new pacct_struct
592 * @pacct: per-process accounting info struct to initialize
593 */
594void acct_init_pacct(struct pacct_struct *pacct)
595{
596    memset(pacct, 0, sizeof(struct pacct_struct));
597    pacct->ac_utime = pacct->ac_stime = cputime_zero;
598}
599
600/**
601 * acct_collect - collect accounting information into pacct_struct
602 * @exitcode: task exit code
603 * @group_dead: not 0, if this thread is the last one in the process.
604 */
605void acct_collect(long exitcode, int group_dead)
606{
607    struct pacct_struct *pacct = &current->signal->pacct;
608    unsigned long vsize = 0;
609
610    if (group_dead && current->mm) {
611        struct vm_area_struct *vma;
612        down_read(&current->mm->mmap_sem);
613        vma = current->mm->mmap;
614        while (vma) {
615            vsize += vma->vm_end - vma->vm_start;
616            vma = vma->vm_next;
617        }
618        up_read(&current->mm->mmap_sem);
619    }
620
621    spin_lock_irq(&current->sighand->siglock);
622    if (group_dead)
623        pacct->ac_mem = vsize / 1024;
624    if (thread_group_leader(current)) {
625        pacct->ac_exitcode = exitcode;
626        if (current->flags & PF_FORKNOEXEC)
627            pacct->ac_flag |= AFORK;
628    }
629    if (current->flags & PF_SUPERPRIV)
630        pacct->ac_flag |= ASU;
631    if (current->flags & PF_DUMPCORE)
632        pacct->ac_flag |= ACORE;
633    if (current->flags & PF_SIGNALED)
634        pacct->ac_flag |= AXSIG;
635    pacct->ac_utime = cputime_add(pacct->ac_utime, current->utime);
636    pacct->ac_stime = cputime_add(pacct->ac_stime, current->stime);
637    pacct->ac_minflt += current->min_flt;
638    pacct->ac_majflt += current->maj_flt;
639    spin_unlock_irq(&current->sighand->siglock);
640}
641
642static void acct_process_in_ns(struct pid_namespace *ns)
643{
644    struct file *file = NULL;
645    struct bsd_acct_struct *acct;
646
647    acct = ns->bacct;
648    /*
649     * accelerate the common fastpath:
650     */
651    if (!acct || !acct->file)
652        return;
653
654    spin_lock(&acct_lock);
655    file = acct->file;
656    if (unlikely(!file)) {
657        spin_unlock(&acct_lock);
658        return;
659    }
660    get_file(file);
661    spin_unlock(&acct_lock);
662
663    do_acct_process(acct, ns, file);
664    fput(file);
665}
666
667/**
668 * acct_process - now just a wrapper around acct_process_in_ns,
669 * which in turn is a wrapper around do_acct_process.
670 *
671 * handles process accounting for an exiting task
672 */
673void acct_process(void)
674{
675    struct pid_namespace *ns;
676
677    /*
678     * This loop is safe lockless, since current is still
679     * alive and holds its namespace, which in turn holds
680     * its parent.
681     */
682    for (ns = task_active_pid_ns(current); ns != NULL; ns = ns->parent)
683        acct_process_in_ns(ns);
684}
685

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