FreeBSD/Linux Kernel Cross Reference
sys/kernel/acct.c

     /*
      *  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/config.h>
    #include <linux/errno.h>
    #include <linux/kernel.h>
    
    #ifdef CONFIG_BSD_PROCESS_ACCT
    #include <linux/mm.h>
    #include <linux/slab.h>
    #include <linux/acct.h>
    #include <linux/smp_lock.h>
    #include <linux/file.h>
    #include <linux/tty.h>
    
    #include <asm/uaccess.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 volatile int acct_active;
    static volatile int acct_needcheck;
    static struct file *acct_file;
    static struct timer_list acct_timer;
    static void do_acct_process(long, struct file *);
    
    /*
     * Called whenever the timer says to check the free space.
     */
    static void acct_timeout(unsigned long unused)
    {
            acct_needcheck = 1;
    }
    
    /*
     * Check the amount of free space and suspend/resume accordingly.
     */
    static int check_free_space(struct file *file)
    {
            struct statfs sbuf;
            int res;
            int act;
    
            lock_kernel();
           res = acct_active;
           if (!file || !acct_needcheck)
                   goto out;
           unlock_kernel();
   
           /* May block */
           if (vfs_statfs(file->f_dentry->d_inode->i_sb, &sbuf))
                   return res;
   
           if (sbuf.f_bavail <= SUSPEND * sbuf.f_blocks / 100)
                   act = -1;
           else if (sbuf.f_bavail >= RESUME * sbuf.f_blocks / 100)
                   act = 1;
           else
                   act = 0;
   
           /*
            * If some joker switched acct_file under us we'ld better be
            * silent and _not_ touch anything.
            */
           lock_kernel();
           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\n");
                   }
           } else {
                   if (act > 0) {
                           acct_active = 1;
                           printk(KERN_INFO "Process accounting resumed\n");
                   }
           }
   
           del_timer(&acct_timer);
           acct_needcheck = 0;
           acct_timer.expires = jiffies + ACCT_TIMEOUT*HZ;
           add_timer(&acct_timer);
           res = acct_active;
   out:
           unlock_kernel();
           return res;
   }
   
   /*
    *  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.
    */
   asmlinkage long sys_acct(const char *name)
   {
           struct file *file = NULL, *old_acct = NULL;
           char *tmp;
           int error;
   
           if (!capable(CAP_SYS_PACCT))
                   return -EPERM;
   
           if (name) {
                   tmp = getname(name);
                   error = PTR_ERR(tmp);
                   if (IS_ERR(tmp))
                           goto out;
                   /* Difference from BSD - they don't do O_APPEND */
                   file = filp_open(tmp, O_WRONLY|O_APPEND, 0);
                   putname(tmp);
                   if (IS_ERR(file)) {
                           error = PTR_ERR(file);
                           goto out;
                   }
                   error = -EACCES;
                   if (!S_ISREG(file->f_dentry->d_inode->i_mode)) 
                           goto out_err;
   
                   error = -EIO;
                   if (!file->f_op->write) 
                           goto out_err;
           }
   
           error = 0;
           lock_kernel();
           if (acct_file) {
                   old_acct = acct_file;
                   del_timer(&acct_timer);
                   acct_active = 0;
                   acct_needcheck = 0;
                   acct_file = NULL;
           }
           if (name) {
                   acct_file = file;
                   acct_needcheck = 0;
                   acct_active = 1;
                   /* It's been deleted if it was used before so this is safe */
                   init_timer(&acct_timer);
                   acct_timer.function = acct_timeout;
                   acct_timer.expires = jiffies + ACCT_TIMEOUT*HZ;
                   add_timer(&acct_timer);
           }
           unlock_kernel();
           if (old_acct) {
                   do_acct_process(0,old_acct);
                   filp_close(old_acct, NULL);
           }
   out:
           return error;
   out_err:
           filp_close(file, NULL);
           goto out;
   }
   
   void acct_auto_close(kdev_t dev)
   {
           lock_kernel();
           if (acct_file && acct_file->f_dentry->d_inode->i_dev == dev)
                   sys_acct(NULL);
           unlock_kernel();
   }
   
   /*
    *  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;
   }
   
   /*
    *  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().
    */
   
   /*
    *  do_acct_process does all actual work. Caller holds the reference to file.
    */
   static void do_acct_process(long exitcode, struct file *file)
   {
           struct acct ac;
           mm_segment_t fs;
           unsigned long vsize;
           unsigned long flim;
   
           /*
            * First check to see if there is enough free_space to continue
            * the process accounting system.
            */
           if (!check_free_space(file))
                   return;
   
           /*
            * Fill the accounting struct with the needed info as recorded
            * by the different kernel functions.
            */
           memset((caddr_t)&ac, 0, sizeof(struct acct));
   
           strncpy(ac.ac_comm, current->comm, ACCT_COMM);
           ac.ac_comm[ACCT_COMM - 1] = '\0';
   
           ac.ac_btime = CT_TO_SECS(current->start_time) + (xtime.tv_sec - (jiffies / HZ));
           ac.ac_etime = encode_comp_t(jiffies - current->start_time);
           ac.ac_utime = encode_comp_t(current->times.tms_utime);
           ac.ac_stime = encode_comp_t(current->times.tms_stime);
           ac.ac_uid = current->uid;
           ac.ac_gid = current->gid;
           ac.ac_tty = (current->tty) ? kdev_t_to_nr(current->tty->device) : 0;
   
           ac.ac_flag = 0;
           if (current->flags & PF_FORKNOEXEC)
                   ac.ac_flag |= AFORK;
           if (current->flags & PF_SUPERPRIV)
                   ac.ac_flag |= ASU;
           if (current->flags & PF_DUMPCORE)
                   ac.ac_flag |= ACORE;
           if (current->flags & PF_SIGNALED)
                   ac.ac_flag |= AXSIG;
   
           vsize = 0;
           if (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);
           }
           vsize = vsize / 1024;
           ac.ac_mem = encode_comp_t(vsize);
           ac.ac_io = encode_comp_t(0 /* current->io_usage */);    /* %% */
           ac.ac_rw = encode_comp_t(ac.ac_io / 1024);
           ac.ac_minflt = encode_comp_t(current->min_flt);
           ac.ac_majflt = encode_comp_t(current->maj_flt);
           ac.ac_swaps = encode_comp_t(current->nswap);
           ac.ac_exitcode = exitcode;
   
           /*
            * 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->rlim[RLIMIT_FSIZE].rlim_cur;
           current->rlim[RLIMIT_FSIZE].rlim_cur = RLIM_INFINITY;
           file->f_op->write(file, (char *)&ac,
                                  sizeof(struct acct), &file->f_pos);
           current->rlim[RLIMIT_FSIZE].rlim_cur = flim;
           set_fs(fs);
   }
   
   /*
    * acct_process - now just a wrapper around do_acct_process
    */
   int acct_process(long exitcode)
   {
           struct file *file = NULL;
           lock_kernel();
           if (acct_file) {
                   file = acct_file;
                   get_file(file);
                   unlock_kernel();
                   do_acct_process(exitcode, file);
                   fput(file);
           } else
                   unlock_kernel();
           return 0;
   }
   
   #else
   /*
    * Dummy system call when BSD process accounting is not configured
    * into the kernel.
    */
   
   asmlinkage long sys_acct(const char * filename)
   {
           return -ENOSYS;
   }
   #endif

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