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

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