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, &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    struct pid_namespace *ns;
220    struct bsd_acct_struct *acct = NULL;
221
222    /* Difference from BSD - they don't do O_APPEND */
223    file = filp_open(name, O_WRONLY|O_APPEND|O_LARGEFILE, 0);
224    if (IS_ERR(file))
225        return PTR_ERR(file);
226
227    if (!S_ISREG(file->f_path.dentry->d_inode->i_mode)) {
228        filp_close(file, NULL);
229        return -EACCES;
230    }
231
232    if (!file->f_op->write) {
233        filp_close(file, NULL);
234        return -EIO;
235    }
236
237    ns = task_active_pid_ns(current);
238    if (ns->bacct == NULL) {
239        acct = kzalloc(sizeof(struct bsd_acct_struct), GFP_KERNEL);
240        if (acct == NULL) {
241            filp_close(file, NULL);
242            return -ENOMEM;
243        }
244    }
245
246    spin_lock(&acct_lock);
247    if (ns->bacct == NULL) {
248        ns->bacct = acct;
249        acct = NULL;
250    }
251
252    mnt = file->f_path.mnt;
253    mnt_pin(mnt);
254    acct_file_reopen(ns->bacct, file, ns);
255    spin_unlock(&acct_lock);
256
257    mntput(mnt); /* it's pinned, now give up active reference */
258    kfree(acct);
259
260    return 0;
261}
262
263/**
264 * sys_acct - enable/disable process accounting
265 * @name: file name for accounting records or NULL to shutdown accounting
266 *
267 * Returns 0 for success or negative errno values for failure.
268 *
269 * sys_acct() is the only system call needed to implement process
270 * accounting. It takes the name of the file where accounting records
271 * should be written. If the filename is NULL, accounting will be
272 * shutdown.
273 */
274SYSCALL_DEFINE1(acct, const char __user *, name)
275{
276    int error = 0;
277
278    if (!capable(CAP_SYS_PACCT))
279        return -EPERM;
280
281    if (name) {
282        char *tmp = getname(name);
283        if (IS_ERR(tmp))
284            return (PTR_ERR(tmp));
285        error = acct_on(tmp);
286        putname(tmp);
287    } else {
288        struct bsd_acct_struct *acct;
289
290        acct = task_active_pid_ns(current)->bacct;
291        if (acct == NULL)
292            return 0;
293
294        spin_lock(&acct_lock);
295        acct_file_reopen(acct, NULL, NULL);
296        spin_unlock(&acct_lock);
297    }
298
299    return error;
300}
301
302/**
303 * acct_auto_close - turn off a filesystem's accounting if it is on
304 * @m: vfsmount being shut down
305 *
306 * If the accounting is turned on for a file in the subtree pointed to
307 * to by m, turn accounting off. Done when m is about to die.
308 */
309void acct_auto_close_mnt(struct vfsmount *m)
310{
311    struct bsd_acct_struct *acct;
312
313    spin_lock(&acct_lock);
314restart:
315    list_for_each_entry(acct, &acct_list, list)
316        if (acct->file && acct->file->f_path.mnt == m) {
317            acct_file_reopen(acct, NULL, NULL);
318            goto restart;
319        }
320    spin_unlock(&acct_lock);
321}
322
323/**
324 * acct_auto_close - turn off a filesystem's accounting if it is on
325 * @sb: super block for the filesystem
326 *
327 * If the accounting is turned on for a file in the filesystem pointed
328 * to by sb, turn accounting off.
329 */
330void acct_auto_close(struct super_block *sb)
331{
332    struct bsd_acct_struct *acct;
333
334    spin_lock(&acct_lock);
335restart:
336    list_for_each_entry(acct, &acct_list, list)
337        if (acct->file && acct->file->f_path.mnt->mnt_sb == sb) {
338            acct_file_reopen(acct, NULL, NULL);
339            goto restart;
340        }
341    spin_unlock(&acct_lock);
342}
343
344void acct_exit_ns(struct pid_namespace *ns)
345{
346    struct bsd_acct_struct *acct = ns->bacct;
347
348    if (acct == NULL)
349        return;
350
351    del_timer_sync(&acct->timer);
352    spin_lock(&acct_lock);
353    if (acct->file != NULL)
354        acct_file_reopen(acct, NULL, NULL);
355    spin_unlock(&acct_lock);
356
357    kfree(acct);
358}
359
360/*
361 * encode an unsigned long into a comp_t
362 *
363 * This routine has been adopted from the encode_comp_t() function in
364 * the kern_acct.c file of the FreeBSD operating system. The encoding
365 * is a 13-bit fraction with a 3-bit (base 8) exponent.
366 */
367
368#define MANTSIZE 13 /* 13 bit mantissa. */
369#define EXPSIZE 3 /* Base 8 (3 bit) exponent. */
370#define MAXFRACT ((1 << MANTSIZE) - 1) /* Maximum fractional value. */
371
372static comp_t encode_comp_t(unsigned long value)
373{
374    int exp, rnd;
375
376    exp = rnd = 0;
377    while (value > MAXFRACT) {
378        rnd = value & (1 << (EXPSIZE - 1)); /* Round up? */
379        value >>= EXPSIZE; /* Base 8 exponent == 3 bit shift. */
380        exp++;
381    }
382
383    /*
384     * If we need to round up, do it (and handle overflow correctly).
385     */
386    if (rnd && (++value > MAXFRACT)) {
387        value >>= EXPSIZE;
388        exp++;
389    }
390
391    /*
392     * Clean it up and polish it off.
393     */
394    exp <<= MANTSIZE; /* Shift the exponent into place */
395    exp += value; /* and add on the mantissa. */
396    return exp;
397}
398
399#if ACCT_VERSION==1 || ACCT_VERSION==2
400/*
401 * encode an u64 into a comp2_t (24 bits)
402 *
403 * Format: 5 bit base 2 exponent, 20 bits mantissa.
404 * The leading bit of the mantissa is not stored, but implied for
405 * non-zero exponents.
406 * Largest encodable value is 50 bits.
407 */
408
409#define MANTSIZE2 20 /* 20 bit mantissa. */
410#define EXPSIZE2 5 /* 5 bit base 2 exponent. */
411#define MAXFRACT2 ((1ul << MANTSIZE2) - 1) /* Maximum fractional value. */
412#define MAXEXP2 ((1 <<EXPSIZE2) - 1) /* Maximum exponent. */
413
414static comp2_t encode_comp2_t(u64 value)
415{
416    int exp, rnd;
417
418    exp = (value > (MAXFRACT2>>1));
419    rnd = 0;
420    while (value > MAXFRACT2) {
421        rnd = value & 1;
422        value >>= 1;
423        exp++;
424    }
425
426    /*
427     * If we need to round up, do it (and handle overflow correctly).
428     */
429    if (rnd && (++value > MAXFRACT2)) {
430        value >>= 1;
431        exp++;
432    }
433
434    if (exp > MAXEXP2) {
435        /* Overflow. Return largest representable number instead. */
436        return (1ul << (MANTSIZE2+EXPSIZE2-1)) - 1;
437    } else {
438        return (value & (MAXFRACT2>>1)) | (exp << (MANTSIZE2-1));
439    }
440}
441#endif
442
443#if ACCT_VERSION==3
444/*
445 * encode an u64 into a 32 bit IEEE float
446 */
447static u32 encode_float(u64 value)
448{
449    unsigned exp = 190;
450    unsigned u;
451
452    if (value==0) return 0;
453    while ((s64)value > 0){
454        value <<= 1;
455        exp--;
456    }
457    u = (u32)(value >> 40) & 0x7fffffu;
458    return u | (exp << 23);
459}
460#endif
461
462/*
463 * Write an accounting entry for an exiting process
464 *
465 * The acct_process() call is the workhorse of the process
466 * accounting system. The struct acct is built here and then written
467 * into the accounting file. This function should only be called from
468 * do_exit() or when switching to a different output file.
469 */
470
471/*
472 * do_acct_process does all actual work. Caller holds the reference to file.
473 */
474static void do_acct_process(struct bsd_acct_struct *acct,
475        struct pid_namespace *ns, struct file *file)
476{
477    struct pacct_struct *pacct = &current->signal->pacct;
478    acct_t ac;
479    mm_segment_t fs;
480    unsigned long flim;
481    u64 elapsed;
482    u64 run_time;
483    struct timespec uptime;
484    struct tty_struct *tty;
485    const struct cred *orig_cred;
486
487    /* Perform file operations on behalf of whoever enabled accounting */
488    orig_cred = override_creds(file->f_cred);
489
490    /*
491     * First check to see if there is enough free_space to continue
492     * the process accounting system.
493     */
494    if (!check_free_space(acct, file))
495        goto out;
496
497    /*
498     * Fill the accounting struct with the needed info as recorded
499     * by the different kernel functions.
500     */
501    memset((caddr_t)&ac, 0, sizeof(acct_t));
502
503    ac.ac_version = ACCT_VERSION | ACCT_BYTEORDER;
504    strlcpy(ac.ac_comm, current->comm, sizeof(ac.ac_comm));
505
506    /* calculate run_time in nsec*/
507    do_posix_clock_monotonic_gettime(&uptime);
508    run_time = (u64)uptime.tv_sec*NSEC_PER_SEC + uptime.tv_nsec;
509    run_time -= (u64)current->group_leader->start_time.tv_sec * NSEC_PER_SEC
510               + current->group_leader->start_time.tv_nsec;
511    /* convert nsec -> AHZ */
512    elapsed = nsec_to_AHZ(run_time);
513#if ACCT_VERSION==3
514    ac.ac_etime = encode_float(elapsed);
515#else
516    ac.ac_etime = encode_comp_t(elapsed < (unsigned long) -1l ?
517                           (unsigned long) elapsed : (unsigned long) -1l);
518#endif
519#if ACCT_VERSION==1 || ACCT_VERSION==2
520    {
521        /* new enlarged etime field */
522        comp2_t etime = encode_comp2_t(elapsed);
523        ac.ac_etime_hi = etime >> 16;
524        ac.ac_etime_lo = (u16) etime;
525    }
526#endif
527    do_div(elapsed, AHZ);
528    ac.ac_btime = get_seconds() - elapsed;
529    /* we really need to bite the bullet and change layout */
530    ac.ac_uid = orig_cred->uid;
531    ac.ac_gid = orig_cred->gid;
532#if ACCT_VERSION==2
533    ac.ac_ahz = AHZ;
534#endif
535#if ACCT_VERSION==1 || ACCT_VERSION==2
536    /* backward-compatible 16 bit fields */
537    ac.ac_uid16 = ac.ac_uid;
538    ac.ac_gid16 = ac.ac_gid;
539#endif
540#if ACCT_VERSION==3
541    ac.ac_pid = task_tgid_nr_ns(current, ns);
542    rcu_read_lock();
543    ac.ac_ppid = task_tgid_nr_ns(rcu_dereference(current->real_parent), ns);
544    rcu_read_unlock();
545#endif
546
547    spin_lock_irq(&current->sighand->siglock);
548    tty = current->signal->tty; /* Safe as we hold the siglock */
549    ac.ac_tty = tty ? old_encode_dev(tty_devnum(tty)) : 0;
550    ac.ac_utime = encode_comp_t(jiffies_to_AHZ(cputime_to_jiffies(pacct->ac_utime)));
551    ac.ac_stime = encode_comp_t(jiffies_to_AHZ(cputime_to_jiffies(pacct->ac_stime)));
552    ac.ac_flag = pacct->ac_flag;
553    ac.ac_mem = encode_comp_t(pacct->ac_mem);
554    ac.ac_minflt = encode_comp_t(pacct->ac_minflt);
555    ac.ac_majflt = encode_comp_t(pacct->ac_majflt);
556    ac.ac_exitcode = pacct->ac_exitcode;
557    spin_unlock_irq(&current->sighand->siglock);
558    ac.ac_io = encode_comp_t(0 /* current->io_usage */); /* %% */
559    ac.ac_rw = encode_comp_t(ac.ac_io / 1024);
560    ac.ac_swaps = encode_comp_t(0);
561
562    /*
563     * Kernel segment override to datasegment and write it
564     * to the accounting file.
565     */
566    fs = get_fs();
567    set_fs(KERNEL_DS);
568    /*
569     * Accounting records are not subject to resource limits.
570     */
571    flim = current->signal->rlim[RLIMIT_FSIZE].rlim_cur;
572    current->signal->rlim[RLIMIT_FSIZE].rlim_cur = RLIM_INFINITY;
573    file->f_op->write(file, (char *)&ac,
574                   sizeof(acct_t), &file->f_pos);
575    current->signal->rlim[RLIMIT_FSIZE].rlim_cur = flim;
576    set_fs(fs);
577out:
578    revert_creds(orig_cred);
579}
580
581/**
582 * acct_collect - collect accounting information into pacct_struct
583 * @exitcode: task exit code
584 * @group_dead: not 0, if this thread is the last one in the process.
585 */
586void acct_collect(long exitcode, int group_dead)
587{
588    struct pacct_struct *pacct = &current->signal->pacct;
589    unsigned long vsize = 0;
590
591    if (group_dead && current->mm) {
592        struct vm_area_struct *vma;
593        down_read(&current->mm->mmap_sem);
594        vma = current->mm->mmap;
595        while (vma) {
596            vsize += vma->vm_end - vma->vm_start;
597            vma = vma->vm_next;
598        }
599        up_read(&current->mm->mmap_sem);
600    }
601
602    spin_lock_irq(&current->sighand->siglock);
603    if (group_dead)
604        pacct->ac_mem = vsize / 1024;
605    if (thread_group_leader(current)) {
606        pacct->ac_exitcode = exitcode;
607        if (current->flags & PF_FORKNOEXEC)
608            pacct->ac_flag |= AFORK;
609    }
610    if (current->flags & PF_SUPERPRIV)
611        pacct->ac_flag |= ASU;
612    if (current->flags & PF_DUMPCORE)
613        pacct->ac_flag |= ACORE;
614    if (current->flags & PF_SIGNALED)
615        pacct->ac_flag |= AXSIG;
616    pacct->ac_utime = cputime_add(pacct->ac_utime, current->utime);
617    pacct->ac_stime = cputime_add(pacct->ac_stime, current->stime);
618    pacct->ac_minflt += current->min_flt;
619    pacct->ac_majflt += current->maj_flt;
620    spin_unlock_irq(&current->sighand->siglock);
621}
622
623static void acct_process_in_ns(struct pid_namespace *ns)
624{
625    struct file *file = NULL;
626    struct bsd_acct_struct *acct;
627
628    acct = ns->bacct;
629    /*
630     * accelerate the common fastpath:
631     */
632    if (!acct || !acct->file)
633        return;
634
635    spin_lock(&acct_lock);
636    file = acct->file;
637    if (unlikely(!file)) {
638        spin_unlock(&acct_lock);
639        return;
640    }
641    get_file(file);
642    spin_unlock(&acct_lock);
643
644    do_acct_process(acct, ns, file);
645    fput(file);
646}
647
648/**
649 * acct_process - now just a wrapper around acct_process_in_ns,
650 * which in turn is a wrapper around do_acct_process.
651 *
652 * handles process accounting for an exiting task
653 */
654void acct_process(void)
655{
656    struct pid_namespace *ns;
657
658    /*
659     * This loop is safe lockless, since current is still
660     * alive and holds its namespace, which in turn holds
661     * its parent.
662     */
663    for (ns = task_active_pid_ns(current); ns != NULL; ns = ns->parent)
664        acct_process_in_ns(ns);
665}
666

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