/*
   *  linux/kernel/acct.c
   *
   *  BSD Process Accounting for Linux
   *
   *  Author: Marco van Wieringen <mvw@planets.elm.net>
   *
   *  Some code based on ideas and code from:
   *  Thomas K. Dyas <tdyas@eden.rutgers.edu>
   *
   *  This file implements BSD-style process accounting. Whenever any
   *  process exits, an accounting record of type "struct acct" is
   *  written to the file specified with the acct() system call. It is
   *  up to user-level programs to do useful things with the accounting
   *  log. The kernel just provides the raw accounting information.
   *
   * (C) Copyright 1995 - 1997 Marco van Wieringen - ELM Consultancy B.V.
   *
   *  Plugged two leaks. 1) It didn't return acct_file into the free_filps if
   *  the file happened to be read-only. 2) If the accounting was suspended
   *  due to the lack of space it happily allowed to reopen it and completely
   *  lost the old acct_file. 3/10/98, Al Viro.
   *
   *  Now we silently close acct_file on attempt to reopen. Cleaned sys_acct().
   *  XTerms and EMACS are manifestations of pure evil. 21/10/98, AV.
   *
   *  Fixed a nasty interaction with with sys_umount(). If the accointing
   *  was suspeneded we failed to stop it on umount(). Messy.
   *  Another one: remount to readonly didn't stop accounting.
   *	Question: what should we do if we have CAP_SYS_ADMIN but not
   *  CAP_SYS_PACCT? Current code does the following: umount returns -EBUSY
   *  unless we are messing with the root. In that case we are getting a
   *  real mess with do_remount_sb(). 9/11/98, AV.
   *
   *  Fixed a bunch of races (and pair of leaks). Probably not the best way,
   *  but this one obviously doesn't introduce deadlocks. Later. BTW, found
   *  one race (and leak) in BSD implementation.
   *  OK, that's better. ANOTHER race and leak in BSD variant. There always
   *  is one more bug... 10/11/98, AV.
   *
   *	Oh, fsck... Oopsable SMP race in do_process_acct() - we must hold
   * ->mmap_sem to walk the vma list of current->mm. Nasty, since it leaks
   * a struct file opened for write. Fixed. 2/6/2000, AV.
   */

  #include <linux/mm.h>
  #include <linux/slab.h>
  #include <linux/acct.h>

  #include <linux/capability.h>

  #include <linux/file.h>
  #include <linux/tty.h>
  #include <linux/security.h>
  #include <linux/vfs.h>
  #include <linux/jiffies.h>
  #include <linux/times.h>
  #include <linux/syscalls.h>

  #include <linux/mount.h>

  #include <asm/uaccess.h>
  #include <asm/div64.h>
  #include <linux/blkdev.h> /* sector_div */

  #include <linux/pid_namespace.h>

  
  /*
   * These constants control the amount of freespace that suspend and
   * resume the process accounting system, and the time delay between
   * each check.
   * Turned into sysctl-controllable parameters. AV, 12/11/98
   */
  
  int acct_parm[3] = {4, 2, 30};
  #define RESUME		(acct_parm[0])	/* >foo% free space - resume */
  #define SUSPEND		(acct_parm[1])	/* <foo% free space - suspend */
  #define ACCT_TIMEOUT	(acct_parm[2])	/* foo second timeout between checks */
  
  /*
   * External references and all of the globals.
   */

  static void do_acct_process(struct bsd_acct_struct *acct,
  		struct pid_namespace *ns, struct file *);

  
  /*
   * This structure is used so that all the data protected by lock
   * can be placed in the same cache line as the lock.  This primes
   * the cache line to have the data after getting the lock.
   */

  struct bsd_acct_struct {

  	int			active;
  	unsigned long		needcheck;

  	struct file		*file;

  	struct pid_namespace	*ns;

  	struct list_head	list;

  };

  static DEFINE_SPINLOCK(acct_lock);

  static LIST_HEAD(acct_list);

  /*

   * Check the amount of free space and suspend/resume accordingly.
   */

  static int check_free_space(struct bsd_acct_struct *acct, struct file *file)

  {
  	struct kstatfs sbuf;
  	int res;
  	int act;

  	u64 resume;
  	u64 suspend;

  	spin_lock(&acct_lock);

  	res = acct->active;

  	if (!file || time_is_before_jiffies(acct->needcheck))

  		goto out;

  	spin_unlock(&acct_lock);

  
  	/* May block */

  	if (vfs_statfs(&file->f_path, &sbuf))

  		return res;
  	suspend = sbuf.f_blocks * SUSPEND;
  	resume = sbuf.f_blocks * RESUME;

  	do_div(suspend, 100);
  	do_div(resume, 100);

  
  	if (sbuf.f_bavail <= suspend)
  		act = -1;
  	else if (sbuf.f_bavail >= resume)
  		act = 1;
  	else
  		act = 0;
  
  	/*

  	 * If some joker switched acct->file under us we'ld better be

  	 * silent and _not_ touch anything.
  	 */

  	spin_lock(&acct_lock);

  	if (file != acct->file) {

  		if (act)
  			res = act>0;
  		goto out;
  	}

  	if (acct->active) {

  		if (act < 0) {

  			acct->active = 0;

  			printk(KERN_INFO "Process accounting paused
  ");
  		}
  	} else {
  		if (act > 0) {

  			acct->active = 1;

  			printk(KERN_INFO "Process accounting resumed
  ");
  		}
  	}

  	acct->needcheck = jiffies + ACCT_TIMEOUT*HZ;

  	res = acct->active;

  out:

  	spin_unlock(&acct_lock);

  	return res;
  }
  
  /*

   * Close the old accounting file (if currently open) and then replace

   * it with file (if non-NULL).
   *

   * NOTE: acct_lock MUST be held on entry and exit.

   */

  static void acct_file_reopen(struct bsd_acct_struct *acct, struct file *file,
  		struct pid_namespace *ns)

  {
  	struct file *old_acct = NULL;

  	struct pid_namespace *old_ns = NULL;

  	if (acct->file) {
  		old_acct = acct->file;
  		old_ns = acct->ns;

  		acct->active = 0;

  		acct->file = NULL;

  		acct->ns = NULL;

  		list_del(&acct->list);

  	}
  	if (file) {

  		acct->file = file;

  		acct->ns = ns;

  		acct->needcheck = jiffies + ACCT_TIMEOUT*HZ;

  		acct->active = 1;

  		list_add(&acct->list, &acct_list);

  	}
  	if (old_acct) {

  		mnt_unpin(old_acct->f_path.mnt);

  		spin_unlock(&acct_lock);

  		do_acct_process(acct, old_ns, old_acct);

  		filp_close(old_acct, NULL);

  		spin_lock(&acct_lock);

  	}
  }

  static int acct_on(char *name)
  {
  	struct file *file;

  	struct vfsmount *mnt;

  	struct pid_namespace *ns;
  	struct bsd_acct_struct *acct = NULL;

  
  	/* Difference from BSD - they don't do O_APPEND */
  	file = filp_open(name, O_WRONLY|O_APPEND|O_LARGEFILE, 0);
  	if (IS_ERR(file))
  		return PTR_ERR(file);

  	if (!S_ISREG(file->f_path.dentry->d_inode->i_mode)) {

  		filp_close(file, NULL);
  		return -EACCES;
  	}
  
  	if (!file->f_op->write) {
  		filp_close(file, NULL);
  		return -EIO;
  	}

  	ns = task_active_pid_ns(current);
  	if (ns->bacct == NULL) {
  		acct = kzalloc(sizeof(struct bsd_acct_struct), GFP_KERNEL);
  		if (acct == NULL) {
  			filp_close(file, NULL);
  			return -ENOMEM;
  		}
  	}

  	spin_lock(&acct_lock);

  	if (ns->bacct == NULL) {
  		ns->bacct = acct;
  		acct = NULL;
  	}

  	mnt = file->f_path.mnt;
  	mnt_pin(mnt);

  	acct_file_reopen(ns->bacct, file, ns);

  	spin_unlock(&acct_lock);

  	mntput(mnt); /* it's pinned, now give up active reference */

  	kfree(acct);

  
  	return 0;
  }

  /**
   * sys_acct - enable/disable process accounting
   * @name: file name for accounting records or NULL to shutdown accounting
   *
   * Returns 0 for success or negative errno values for failure.
   *
   * sys_acct() is the only system call needed to implement process
   * accounting. It takes the name of the file where accounting records
   * should be written. If the filename is NULL, accounting will be
   * shutdown.

   */

  SYSCALL_DEFINE1(acct, const char __user *, name)

  {

  	int error = 0;

  
  	if (!capable(CAP_SYS_PACCT))
  		return -EPERM;
  
  	if (name) {

  		char *tmp = getname(name);
  		if (IS_ERR(tmp))

  			return (PTR_ERR(tmp));

  		error = acct_on(tmp);

  		putname(tmp);

  	} else {

  		struct bsd_acct_struct *acct;
  
  		acct = task_active_pid_ns(current)->bacct;
  		if (acct == NULL)
  			return 0;

  		spin_lock(&acct_lock);
  		acct_file_reopen(acct, NULL, NULL);
  		spin_unlock(&acct_lock);

  	}

  	return error;
  }

  /**
   * acct_auto_close - turn off a filesystem's accounting if it is on
   * @m: vfsmount being shut down
   *
   * If the accounting is turned on for a file in the subtree pointed to
   * to by m, turn accounting off.  Done when m is about to die.
   */
  void acct_auto_close_mnt(struct vfsmount *m)
  {

  	struct bsd_acct_struct *acct;

  	spin_lock(&acct_lock);

  restart:
  	list_for_each_entry(acct, &acct_list, list)
  		if (acct->file && acct->file->f_path.mnt == m) {
  			acct_file_reopen(acct, NULL, NULL);
  			goto restart;
  		}

  	spin_unlock(&acct_lock);

  }

  /**
   * acct_auto_close - turn off a filesystem's accounting if it is on
   * @sb: super block for the filesystem
   *
   * If the accounting is turned on for a file in the filesystem pointed
   * to by sb, turn accounting off.

   */
  void acct_auto_close(struct super_block *sb)
  {

  	struct bsd_acct_struct *acct;

  	spin_lock(&acct_lock);

  restart:
  	list_for_each_entry(acct, &acct_list, list)

  		if (acct->file && acct->file->f_path.dentry->d_sb == sb) {

  			acct_file_reopen(acct, NULL, NULL);
  			goto restart;
  		}

  	spin_unlock(&acct_lock);
  }
  
  void acct_exit_ns(struct pid_namespace *ns)
  {

  	struct bsd_acct_struct *acct = ns->bacct;

  	if (acct == NULL)
  		return;

  	spin_lock(&acct_lock);
  	if (acct->file != NULL)
  		acct_file_reopen(acct, NULL, NULL);

  	spin_unlock(&acct_lock);

  
  	kfree(acct);

  }
  
  /*
   *  encode an unsigned long into a comp_t
   *
   *  This routine has been adopted from the encode_comp_t() function in
   *  the kern_acct.c file of the FreeBSD operating system. The encoding
   *  is a 13-bit fraction with a 3-bit (base 8) exponent.
   */
  
  #define	MANTSIZE	13			/* 13 bit mantissa. */
  #define	EXPSIZE		3			/* Base 8 (3 bit) exponent. */
  #define	MAXFRACT	((1 << MANTSIZE) - 1)	/* Maximum fractional value. */
  
  static comp_t encode_comp_t(unsigned long value)
  {
  	int exp, rnd;
  
  	exp = rnd = 0;
  	while (value > MAXFRACT) {
  		rnd = value & (1 << (EXPSIZE - 1));	/* Round up? */
  		value >>= EXPSIZE;	/* Base 8 exponent == 3 bit shift. */
  		exp++;
  	}
  
  	/*

  	 * If we need to round up, do it (and handle overflow correctly).
  	 */

  	if (rnd && (++value > MAXFRACT)) {
  		value >>= EXPSIZE;
  		exp++;
  	}
  
  	/*

  	 * Clean it up and polish it off.
  	 */

  	exp <<= MANTSIZE;		/* Shift the exponent into place */
  	exp += value;			/* and add on the mantissa. */
  	return exp;
  }
  
  #if ACCT_VERSION==1 || ACCT_VERSION==2
  /*
   * encode an u64 into a comp2_t (24 bits)
   *
   * Format: 5 bit base 2 exponent, 20 bits mantissa.
   * The leading bit of the mantissa is not stored, but implied for
   * non-zero exponents.
   * Largest encodable value is 50 bits.
   */
  
  #define MANTSIZE2       20                      /* 20 bit mantissa. */
  #define EXPSIZE2        5                       /* 5 bit base 2 exponent. */
  #define MAXFRACT2       ((1ul << MANTSIZE2) - 1) /* Maximum fractional value. */
  #define MAXEXP2         ((1 <<EXPSIZE2) - 1)    /* Maximum exponent. */
  
  static comp2_t encode_comp2_t(u64 value)
  {

  	int exp, rnd;
  
  	exp = (value > (MAXFRACT2>>1));
  	rnd = 0;
  	while (value > MAXFRACT2) {
  		rnd = value & 1;
  		value >>= 1;
  		exp++;
  	}
  
  	/*
  	 * If we need to round up, do it (and handle overflow correctly).
  	 */
  	if (rnd && (++value > MAXFRACT2)) {
  		value >>= 1;
  		exp++;
  	}
  
  	if (exp > MAXEXP2) {
  		/* Overflow. Return largest representable number instead. */
  		return (1ul << (MANTSIZE2+EXPSIZE2-1)) - 1;
  	} else {
  		return (value & (MAXFRACT2>>1)) | (exp << (MANTSIZE2-1));
  	}

  }
  #endif
  
  #if ACCT_VERSION==3
  /*
   * encode an u64 into a 32 bit IEEE float
   */
  static u32 encode_float(u64 value)
  {
  	unsigned exp = 190;
  	unsigned u;
  
  	if (value==0) return 0;
  	while ((s64)value > 0){
  		value <<= 1;
  		exp--;
  	}
  	u = (u32)(value >> 40) & 0x7fffffu;
  	return u | (exp << 23);
  }
  #endif
  
  /*
   *  Write an accounting entry for an exiting process
   *
   *  The acct_process() call is the workhorse of the process
   *  accounting system. The struct acct is built here and then written
   *  into the accounting file. This function should only be called from

   *  do_exit() or when switching to a different output file.

   */
  
  /*
   *  do_acct_process does all actual work. Caller holds the reference to file.
   */

  static void do_acct_process(struct bsd_acct_struct *acct,
  		struct pid_namespace *ns, struct file *file)

  {

  	struct pacct_struct *pacct = &current->signal->pacct;

  	acct_t ac;
  	mm_segment_t fs;

  	unsigned long flim;
  	u64 elapsed;
  	u64 run_time;
  	struct timespec uptime;

  	struct tty_struct *tty;

  	const struct cred *orig_cred;
  
  	/* Perform file operations on behalf of whoever enabled accounting */
  	orig_cred = override_creds(file->f_cred);

  
  	/*
  	 * First check to see if there is enough free_space to continue
  	 * the process accounting system.
  	 */

  	if (!check_free_space(acct, file))

  		goto out;

  
  	/*
  	 * Fill the accounting struct with the needed info as recorded
  	 * by the different kernel functions.
  	 */

  	memset(&ac, 0, sizeof(acct_t));

  
  	ac.ac_version = ACCT_VERSION | ACCT_BYTEORDER;
  	strlcpy(ac.ac_comm, current->comm, sizeof(ac.ac_comm));
  
  	/* calculate run_time in nsec*/
  	do_posix_clock_monotonic_gettime(&uptime);
  	run_time = (u64)uptime.tv_sec*NSEC_PER_SEC + uptime.tv_nsec;

  	run_time -= (u64)current->group_leader->start_time.tv_sec * NSEC_PER_SEC
  		       + current->group_leader->start_time.tv_nsec;

  	/* convert nsec -> AHZ */
  	elapsed = nsec_to_AHZ(run_time);
  #if ACCT_VERSION==3
  	ac.ac_etime = encode_float(elapsed);
  #else
  	ac.ac_etime = encode_comp_t(elapsed < (unsigned long) -1l ?
  	                       (unsigned long) elapsed : (unsigned long) -1l);
  #endif
  #if ACCT_VERSION==1 || ACCT_VERSION==2
  	{
  		/* new enlarged etime field */
  		comp2_t etime = encode_comp2_t(elapsed);
  		ac.ac_etime_hi = etime >> 16;
  		ac.ac_etime_lo = (u16) etime;
  	}
  #endif
  	do_div(elapsed, AHZ);

  	ac.ac_btime = get_seconds() - elapsed;

  	/* we really need to bite the bullet and change layout */

  	ac.ac_uid = orig_cred->uid;
  	ac.ac_gid = orig_cred->gid;

  #if ACCT_VERSION==2
  	ac.ac_ahz = AHZ;
  #endif
  #if ACCT_VERSION==1 || ACCT_VERSION==2
  	/* backward-compatible 16 bit fields */

  	ac.ac_uid16 = ac.ac_uid;
  	ac.ac_gid16 = ac.ac_gid;

  #endif
  #if ACCT_VERSION==3

  	ac.ac_pid = task_tgid_nr_ns(current, ns);

  	rcu_read_lock();

  	ac.ac_ppid = task_tgid_nr_ns(rcu_dereference(current->real_parent), ns);

  	rcu_read_unlock();

  #endif

  	spin_lock_irq(&current->sighand->siglock);

  	tty = current->signal->tty;	/* Safe as we hold the siglock */

  	ac.ac_tty = tty ? old_encode_dev(tty_devnum(tty)) : 0;

  	ac.ac_utime = encode_comp_t(jiffies_to_AHZ(cputime_to_jiffies(pacct->ac_utime)));
  	ac.ac_stime = encode_comp_t(jiffies_to_AHZ(cputime_to_jiffies(pacct->ac_stime)));

  	ac.ac_flag = pacct->ac_flag;

  	ac.ac_mem = encode_comp_t(pacct->ac_mem);

  	ac.ac_minflt = encode_comp_t(pacct->ac_minflt);
  	ac.ac_majflt = encode_comp_t(pacct->ac_majflt);

  	ac.ac_exitcode = pacct->ac_exitcode;

  	spin_unlock_irq(&current->sighand->siglock);

  	ac.ac_io = encode_comp_t(0 /* current->io_usage */);	/* %% */
  	ac.ac_rw = encode_comp_t(ac.ac_io / 1024);

  	ac.ac_swaps = encode_comp_t(0);

  
  	/*

  	 * Kernel segment override to datasegment and write it
  	 * to the accounting file.
  	 */

  	fs = get_fs();
  	set_fs(KERNEL_DS);
  	/*

  	 * Accounting records are not subject to resource limits.
  	 */

  	flim = current->signal->rlim[RLIMIT_FSIZE].rlim_cur;
  	current->signal->rlim[RLIMIT_FSIZE].rlim_cur = RLIM_INFINITY;
  	file->f_op->write(file, (char *)&ac,
  			       sizeof(acct_t), &file->f_pos);
  	current->signal->rlim[RLIMIT_FSIZE].rlim_cur = flim;
  	set_fs(fs);

  out:
  	revert_creds(orig_cred);

  }

  /**

   * acct_collect - collect accounting information into pacct_struct

   * @exitcode: task exit code
   * @group_dead: not 0, if this thread is the last one in the process.

   */

  void acct_collect(long exitcode, int group_dead)

  {
  	struct pacct_struct *pacct = &current->signal->pacct;
  	unsigned long vsize = 0;

  	if (group_dead && current->mm) {

  		struct vm_area_struct *vma;
  		down_read(&current->mm->mmap_sem);
  		vma = current->mm->mmap;
  		while (vma) {
  			vsize += vma->vm_end - vma->vm_start;
  			vma = vma->vm_next;
  		}
  		up_read(&current->mm->mmap_sem);
  	}

  	spin_lock_irq(&current->sighand->siglock);

  	if (group_dead)
  		pacct->ac_mem = vsize / 1024;
  	if (thread_group_leader(current)) {
  		pacct->ac_exitcode = exitcode;
  		if (current->flags & PF_FORKNOEXEC)
  			pacct->ac_flag |= AFORK;
  	}
  	if (current->flags & PF_SUPERPRIV)
  		pacct->ac_flag |= ASU;
  	if (current->flags & PF_DUMPCORE)
  		pacct->ac_flag |= ACORE;
  	if (current->flags & PF_SIGNALED)
  		pacct->ac_flag |= AXSIG;

  	pacct->ac_utime += current->utime;
  	pacct->ac_stime += current->stime;

  	pacct->ac_minflt += current->min_flt;
  	pacct->ac_majflt += current->maj_flt;
  	spin_unlock_irq(&current->sighand->siglock);

  }

  static void acct_process_in_ns(struct pid_namespace *ns)

  {
  	struct file *file = NULL;

  	struct bsd_acct_struct *acct;

  	acct = ns->bacct;

  	/*
  	 * accelerate the common fastpath:
  	 */

  	if (!acct || !acct->file)

  		return;

  	spin_lock(&acct_lock);

  	file = acct->file;

  	if (unlikely(!file)) {

  		spin_unlock(&acct_lock);

  		return;
  	}
  	get_file(file);

  	spin_unlock(&acct_lock);

  	do_acct_process(acct, ns, file);

  	fput(file);
  }

  
  /**

   * acct_process - now just a wrapper around acct_process_in_ns,
   * which in turn is a wrapper around do_acct_process.

   *
   * handles process accounting for an exiting task
   */
  void acct_process(void)
  {
  	struct pid_namespace *ns;

  	/*
  	 * This loop is safe lockless, since current is still
  	 * alive and holds its namespace, which in turn holds
  	 * its parent.
  	 */

  	for (ns = task_active_pid_ns(current); ns != NULL; ns = ns->parent)
  		acct_process_in_ns(ns);
  }