source: trunk/third/top/machine/m_ultrix4.c @ 16185

/*
 * top - a top users display for Unix
 *
 * SYNOPSIS:  any DEC running ULTRIX V4.2 or later
 *
 * DESCRIPTION:
 * This is the machine-dependent module for ULTRIX V4.x
 * It should work on any DEC (mips or VAX) running V4.0 or later.
 *
 * LIBS: 
 *
 * CFLAGS: -DORDER
 *
 * AUTHOR:  David S. Comay <dsc@seismo.css.gov>
 * patches: Alex A. Sergejew <aas@swin.oz.au>
 *          Jeff White <jwhite@isdpvbds1.isd.csc.com>
 *          Rainer Orth <ro@TechFak.Uni-Bielefeld.DE>
 */

#include <sys/types.h>
#include <sys/signal.h>
#include <sys/param.h>

#include <stdio.h>
#include <nlist.h>
#include <math.h>
#include <sys/dir.h>
#include <sys/user.h>
#include <sys/proc.h>
#include <sys/dk.h>
#include <sys/vm.h>
#include <sys/file.h>
#include <sys/time.h>
#include <machine/pte.h>
#ifdef _SIZE_T_
#include <sys/cpudata.h>
#endif

/* #define DOSWAP */

#include "top.h"
#include "machine.h"

extern int errno, sys_nerr;
extern char *sys_errlist[];
#define strerror(e) (((e) >= 0 && (e) < sys_nerr) ? sys_errlist[(e)] : "Unknown error")

#define VMUNIX  "/vmunix"
#define KMEM    "/dev/kmem"
#define MEM     "/dev/mem"
#ifdef DOSWAP
#define SWAP    "/dev/drum"
#endif

/* get_process_info passes back a handle.  This is what it looks like: */

struct handle
{
    struct proc **next_proc;    /* points to next valid proc pointer */
    int remaining;              /* number of pointers remaining */
};

/* declarations for load_avg */
#include "loadavg.h"

/* define what weighted cpu is.  */
#define weighted_cpu(pct, pp) ((pp)->p_time == 0 ? 0.0 : \
                         ((pct) / (1.0 - exp((pp)->p_time * logcpu))))

/* process time is only available in u area, so retrieve it from u.u_ru and
   store a copy in unused (by top) p_ref field of struct proc
   struct timeval field tv_sec is a long, p_ref is an int, but both are the
   same size on VAX and MIPS, so this is safe */
#define PROCTIME(pp) ((pp)->p_ref)

/* what we consider to be process size: */
#define PROCSIZE(pp) ((pp)->p_tsize + (pp)->p_dsize + (pp)->p_ssize)

/* definitions for indices in the nlist array */
#define X_AVENRUN       0
#define X_CCPU          1
#define X_NPROC         2
#define X_PROC          3
#define X_TOTAL         4
#define X_CPUDATA       5
#define X_MPID          6
#define X_HZ            7
#define X_LOWCPU        8
#define X_HIGHCPU       9

static struct nlist nlst[] = {
    { "_avenrun" },             /* 0 */
    { "_ccpu" },                /* 1 */
    { "_nproc" },               /* 2 */
    { "_proc" },                /* 3 */
    { "_total" },               /* 4 */
    { "_cpudata" },             /* 5 */
    { "_mpid" },                /* 6 */
    { "_hz" },                  /* 7 */
    { "_lowcpu" },              /* 8 */
    { "_highcpu" },             /* 9 */
    { 0 }
};

/*
 *  These definitions control the format of the per-process area
 */

static char header[] =
  "  PID X        PRI NICE  SIZE   RES STATE   TIME   WCPU    CPU COMMAND";
/* 0123456   -- field to fill in starts at header+6 */
#define UNAME_START 6

#define Proc_format \
        "%5d %-8.8s %3d %4d %5s %5s %-5s %6s %5.2f%% %5.2f%% %.16s"


/* process state names for the "STATE" column of the display */
/* the extra nulls in the string "run" are for adding a slash and
   the processor number when needed */

char *state_abbrev[] =
{
    "", "sleep", "WAIT", "run\0\0\0", "start", "zomb", "stop"
};


static int kmem, mem;
#ifdef DOSWAP
static int swap;
#endif

/* values that we stash away in _init and use in later routines */

static double logcpu;

/* these are retrieved from the kernel in _init */

static unsigned long proc;
static          int  nproc;
static          long hz;
static load_avg  ccpu;
static          int  lowcpu = 0;
static          int  highcpu = 0;

/* these are offsets obtained via nlist and used in the get_ functions */

static unsigned long avenrun_offset;
static unsigned long mpid_offset;
static unsigned long total_offset;
static unsigned long cpudata_offset;

/* these are for calculating cpu state percentages */

static long cp_time[CPUSTATES];
static long cp_old[CPUSTATES];
static long cp_diff[CPUSTATES];
static struct cpudata *cpudata[MAXCPU];

/* these are for detailing the process states */

int process_states[7];
char *procstatenames[] = {
    "", " sleeping, ", " ABANDONED, ", " running, ", " starting, ",
    " zombie, ", " stopped, ",
    NULL
};

/* these are for detailing the cpu states */

int cpu_states[4];
char *cpustatenames[] = {
    "user", "nice", "system", "idle", NULL
};

/* these are for detailing the memory statistics */

int memory_stats[8];
char *memorynames[] = {
    "Real: ", "K/", "K act/tot  ", "Virtual: ", "K/",
    "K act/tot  ", "Free: ", "K", NULL
};

/* these are names given to allowed sorting orders -- first is default */
char *ordernames[] = {
      "cpu", "size", "res", "time", NULL
};

/* forward definitions for comparison functions */
int compare_cpu();
int compare_size();
int compare_res();
int compare_time();

int (*proc_compares[])() = {
      compare_cpu,
      compare_size,
      compare_res,
      compare_time,
      NULL
};

/* these are for keeping track of the proc array */

static int bytes;
static int pref_len;
static struct proc *pbase;
static struct proc **pref;

/* these are for getting the memory statistics */

static int pageshift;           /* log base 2 of the pagesize */

/* define pagetok in terms of pageshift */

#define pagetok(size) ((size) << pageshift)

/* useful externals */
extern int errno;
extern char *sys_errlist[];

long lseek();
long percentages();

machine_init(statics)

struct statics *statics;

{
    int i = 0;
    int pagesize;

    if ((kmem = open(KMEM, O_RDONLY)) == -1) {
        perror(KMEM);
        return(-1);
    }
    if ((mem = open(MEM, O_RDONLY)) == -1) {
        perror(MEM);
        return(-1);
    }

#ifdef DOSWAP
    if ((swap = open(SWAP, O_RDONLY)) == -1) {
        perror(SWAP);
        return(-1);
    }
#endif

    /* get the list of symbols we want to access in the kernel */
    (void) nlist(VMUNIX, nlst);
    if (nlst[0].n_type == 0)
    {
        fprintf(stderr, "top: nlist failed\n");
        return(-1);
    }

    /* make sure they were all found */
    if (i > 0 && check_nlist(nlst) > 0)
    {
        return(-1);
    }

    /* get the symbol values out of kmem */
    (void) getkval(nlst[X_PROC].n_value,   (int *)(&proc),      sizeof(proc),
            nlst[X_PROC].n_name);
    (void) getkval(nlst[X_NPROC].n_value,  &nproc,              sizeof(nproc),
            nlst[X_NPROC].n_name);
    (void) getkval(nlst[X_HZ].n_value,     (int *)(&hz),        sizeof(hz),
            nlst[X_HZ].n_name);
    (void) getkval(nlst[X_CCPU].n_value,   (int *)(&ccpu),      sizeof(ccpu),
            nlst[X_CCPU].n_name);
    (void) getkval(nlst[X_LOWCPU].n_value,   (int *)(&lowcpu),  sizeof(lowcpu),
            nlst[X_LOWCPU].n_name);
    (void) getkval(nlst[X_HIGHCPU].n_value,   (int *)(&highcpu),        sizeof(highcpu),
            nlst[X_HIGHCPU].n_name);

    /* stash away certain offsets for later use */
    mpid_offset = nlst[X_MPID].n_value;
    avenrun_offset = nlst[X_AVENRUN].n_value;
    total_offset = nlst[X_TOTAL].n_value;
    cpudata_offset = nlst[X_CPUDATA].n_value;

    /* this is used in calculating WCPU -- calculate it ahead of time */
    logcpu = log(loaddouble(ccpu));

    /* allocate space for proc structure array and array of pointers */
    bytes = nproc * sizeof(struct proc);
    pbase = (struct proc *)malloc(bytes);
    pref  = (struct proc **)malloc(nproc * sizeof(struct proc *));

    /* Just in case ... */
    if (pbase == (struct proc *)NULL || pref == (struct proc **)NULL)
    {
        fprintf(stderr, "top: can't allocate sufficient memory\n");
        return(-1);
    }

    /* get the page size with "getpagesize" and calculate pageshift from it */
    pagesize = getpagesize();
    pageshift = 0;
    while (pagesize > 1)
    {
        pageshift++;
        pagesize >>= 1;
    }

    /* we only need the amount of log(2)1024 for our conversion */
    pageshift -= LOG1024;

    /* fill in the statics information */
    statics->procstate_names = procstatenames;
    statics->cpustate_names = cpustatenames;
    statics->memory_names = memorynames;
    statics->order_names = ordernames;

    /* all done! */
    return(0);
}

char *format_header(uname_field)

char *uname_field;

{
    char *ptr;

    ptr = header + UNAME_START;
    while (*uname_field != '\0')
    {
        *ptr++ = *uname_field++;
    }

    return(header);
}

get_system_info(si)

struct system_info *si;

{
    load_avg avenrun[3];
    long total;
    int i;
    int ncpu;
    struct cpudata cpu;

    for (i = 0; i < CPUSTATES; ++i)
    {
        cp_time[i] = 0;
    }
    (void) getkval(cpudata_offset, cpudata, sizeof(cpudata), "_cpudata");
    for (ncpu = lowcpu; ncpu <= highcpu; ++ncpu)
    {
        if (cpudata[ncpu] != NULL) {
                (void) getkval(cpudata[ncpu], &cpu, sizeof(cpu), "???");
                if (cpu.cpu_state & CPU_RUN)
                {
                    for (i = 0; i < CPUSTATES; ++i)
                    {
                        cp_time[i] += cpu.cpu_cptime[i];
                    }
                }
        }
    }

    /* get load average array */
    (void) getkval(avenrun_offset, (int *)avenrun, sizeof(avenrun),
                   "_avenrun");

    /* get mpid -- process id of last process */
    (void) getkval(mpid_offset, &(si->last_pid), sizeof(si->last_pid),
                   "_mpid");

    /* convert load averages to doubles */
    {
        int i;
        double *infoloadp;
        load_avg *sysloadp;

        infoloadp = si->load_avg;
        sysloadp = avenrun;
        for (i = 0; i < 3; i++)
        {
            *infoloadp++ = loaddouble(*sysloadp++);
        }
    }

    /* convert cp_time counts to percentages */
    total = percentages(CPUSTATES, cpu_states, cp_time, cp_old, cp_diff);

    /* sum memory statistics */
    {
        struct vmtotal total;

        /* get total -- systemwide main memory usage structure */
        (void) getkval(total_offset, (int *)(&total), sizeof(total),
                       "_total");
        /* convert memory stats to Kbytes */
        memory_stats[0] = -1;
        memory_stats[1] = pagetok(total.t_arm);
        memory_stats[2] = pagetok(total.t_rm);
        memory_stats[3] = -1;
        memory_stats[4] = pagetok(total.t_avm);
        memory_stats[5] = pagetok(total.t_vm);
        memory_stats[6] = -1;
        memory_stats[7] = pagetok(total.t_free);
    }

    /* set arrays and strings */
    si->cpustates = cpu_states;
    si->memory = memory_stats;
}

static struct handle handle;

caddr_t get_process_info(si, sel, compare)

struct system_info *si;
struct process_select *sel;
int (*compare)();

{
    int i;
    int total_procs;
    int active_procs;
    struct proc **prefp;
    struct proc *pp;
    struct user u;

    /* these are copied out of sel for speed */
    int show_idle;
    int show_system;
    int show_uid;
    int show_command;

    /* read all the proc structures in one fell swoop */
    (void) getkval(proc, (int *)pbase, bytes, "proc array");

    /* get a pointer to the states summary array */
    si->procstates = process_states;

    /* set up flags which define what we are going to select */
    show_idle = sel->idle;
    show_system = sel->system;
    show_uid = sel->uid != -1;
    show_command = sel->command != NULL;

    /* count up process states and get pointers to interesting procs */
    total_procs = 0;
    active_procs = 0;
    memset((char *)process_states, 0, sizeof(process_states));
    prefp = pref;
    for (pp = pbase, i = 0; i < nproc; pp++, i++)
    {
        /*
         *  Place pointers to each valid proc structure in pref[].
         *  Process slots that are actually in use have a non-zero
         *  status field.  Processes with SSYS set are system
         *  processes---these get ignored unless show_sysprocs is set.
         */
        if (pp->p_stat != 0 && pp->p_stat != SIDL &&
            (show_system || ((pp->p_type & SSYS) == 0)))
        {
#ifdef vax
#define PCTCPU_NONZERO (pp->p_pctcpu != 0.0)
#else
#define PCTCPU_NONZERO (pp->p_pctcpu != 0)
#endif
            total_procs++;
            process_states[pp->p_stat]++;
            if ((pp->p_stat != SZOMB) &&
                (pp->p_stat != SIDL) &&
                (show_idle || PCTCPU_NONZERO || (pp->p_stat == SRUN)) &&
                (!show_uid || pp->p_uid == (uid_t)sel->uid))
            {
                *prefp++ = pp;
                active_procs++;

                if (getu(pp, &u) == -1)
                {
                    PROCTIME(pp) = 0;
                }
                else
                {
                    PROCTIME(pp) = u.u_ru.ru_utime.tv_sec +
                        u.u_ru.ru_stime.tv_sec;
                }
            }
        }
    }

    /* if requested, sort the "interesting" processes */
    if (compare != NULL)
    {
        qsort((char *)pref, active_procs, sizeof(struct proc *), compare);
    }

    /* remember active and total counts */
    si->p_total = total_procs;
    si->p_active = pref_len = active_procs;

    /* pass back a handle */
    handle.next_proc = pref;
    handle.remaining = active_procs;
    return((caddr_t)&handle);
}

char fmt[MAX_COLS];             /* static area where result is built */

char *format_next_process(handle, get_userid)

caddr_t handle;
char *(*get_userid)();

{
    struct proc *pp;
    double pct;
    int where;
    struct user u;
    struct handle *hp;

    /* find and remember the next proc structure */
    hp = (struct handle *)handle;
    pp = *(hp->next_proc++);
    hp->remaining--;
    
    /* get the process's user struct */
    where = getu(pp, &u);
    if (where == -1)
    {
        (void) strcpy(u.u_comm, "<swapped>");
    }
    else
    {
        /* set u_comm for system processes */
        if (u.u_comm[0] == '\0')
        {
            if (pp->p_pid == 0)
            {
                (void) strcpy(u.u_comm, "Swapper");
            }
            else if (pp->p_pid == 2)
            {
                (void) strcpy(u.u_comm, "Pager");
            }
        }
        if (where == 1) {
            /*
             * Print swapped processes as <pname>
             */
            char buf[sizeof(u.u_comm)];
            (void) strncpy(buf, u.u_comm, sizeof(u.u_comm));
            u.u_comm[0] = '<';
            (void) strncpy(&u.u_comm[1], buf, sizeof(u.u_comm) - 2);
            u.u_comm[sizeof(u.u_comm) - 2] = '\0';
            (void) strncat(u.u_comm, ">", sizeof(u.u_comm) - 1);
            u.u_comm[sizeof(u.u_comm) - 1] = '\0';
        }
    }

    /* calculate the base for cpu percentages */
    pct = pctdouble(pp->p_pctcpu);

    /* format this entry */
    sprintf(fmt,
            Proc_format,
            pp->p_pid,
            (*get_userid)(pp->p_uid),
            pp->p_pri - PZERO,
            pp->p_nice - NZERO,
            format_k(pagetok(PROCSIZE(pp))),
            format_k(pagetok(pp->p_rssize)),
            state_abbrev[pp->p_stat],
            format_time(PROCTIME(pp)),
            100.0 * weighted_cpu(pct, pp),
            100.0 * pct,
            printable(u.u_comm));

    /* return the result */
    return(fmt);
}

/*
 *  getu(p, u) - get the user structure for the process whose proc structure
 *      is pointed to by p.  The user structure is put in the buffer pointed
 *      to by u.  Return 0 if successful, -1 on failure (such as the process
 *      being swapped out).
 */

#ifdef ibm032
static struct alignuser {
    char userfill[UPAGES*NBPG-sizeof (struct user)];
    struct user user;
} au;
# define USERSIZE sizeof(struct alignuser)
# define GETUSER(b)     (&au)
# define SETUSER(b)     *(b) = au.user
#else
# define USERSIZE sizeof(struct user)
# define GETUSER(b)     (b)
# define SETUSER(b)     /* Nothing */
#endif

getu(p, u)

struct proc *p;
struct user *u;

{
    struct pte uptes[UPAGES];
    caddr_t upage;
    struct pte *pte;
    int nbytes, n;

    /*
     *  Check if the process is currently loaded or swapped out.  The way we
     *  get the u area is totally different for the two cases.  For this
     *  application, we just don't bother if the process is swapped out.
     */
    if ((p->p_sched & SLOAD) == 0) {
#ifdef DOSWAP
        if (lseek(swap, (long)dtob(p->p_swaddr), 0) == -1) {
            perror("lseek(swap)");
            return(-1);
        }
        if (read(swap, (char *) GETUSER(u), USERSIZE) != USERSIZE)  {
            perror("read(swap)");
            return(-1);
        }
        SETUSER(u);
        return (1);
#else
        return(-1);
#endif
    }

    /*
     *  Process is currently in memory, we hope!
     */
    if (!getkval((unsigned long)p->p_addr, (int *)uptes, sizeof(uptes),
                "!p->p_addr"))
    {
#ifdef DEBUG
        perror("getkval(uptes)");
#endif
        /* we can't seem to get to it, so pretend it's swapped out */
        return(-1);
    } 
    upage = (caddr_t) GETUSER(u);
    pte = uptes;
    for (nbytes = USERSIZE; nbytes > 0; nbytes -= NBPG) {
        (void) lseek(mem, (long)(pte++->pg_pfnum * NBPG), 0);
#ifdef DEBUG
        perror("lseek(mem)");
#endif
        n = MIN(nbytes, NBPG);
        if (read(mem, upage, n) != n) {
#ifdef DEBUG
        perror("read(mem)");
#endif
            /* we can't seem to get to it, so pretend it's swapped out */
            return(-1);
        }
        upage += n;
    }
    SETUSER(u);
    return(0);
}

/*
 * check_nlist(nlst) - checks the nlist to see if any symbols were not
 *              found.  For every symbol that was not found, a one-line
 *              message is printed to stderr.  The routine returns the
 *              number of symbols NOT found.
 */

int check_nlist(nlst)

struct nlist *nlst;

{
    int i;

    /* check to see if we got ALL the symbols we requested */
    /* this will write one line to stderr for every symbol not found */

    i = 0;
    while (nlst->n_name != NULL)
    {
        if (nlst->n_type == 0)
        {
            /* this one wasn't found */
            fprintf(stderr, "kernel: no symbol named `%s'\n", nlst->n_name);
            i = 1;
        }
        nlst++;
    }

    return(i);
}


/*
 *  getkval(offset, ptr, size, refstr) - get a value out of the kernel.
 *      "offset" is the byte offset into the kernel for the desired value,
 *      "ptr" points to a buffer into which the value is retrieved,
 *      "size" is the size of the buffer (and the object to retrieve),
 *      "refstr" is a reference string used when printing error meessages,
 *          if "refstr" starts with a '!', then a failure on read will not
 *          be fatal (this may seem like a silly way to do things, but I
 *          really didn't want the overhead of another argument).
 *      
 */

getkval(offset, ptr, size, refstr)

unsigned long offset;
int *ptr;
int size;
char *refstr;

{
    if (lseek(kmem, (long)offset, L_SET) == -1) {
        if (*refstr == '!')
            refstr++;
        (void) fprintf(stderr, "%s: lseek to %s: %s\n", KMEM, 
                       refstr, strerror(errno));
        quit(23);
    }
    if (read(kmem, (char *) ptr, size) == -1) {
        if (*refstr == '!') 
            return(0);
        else {
            (void) fprintf(stderr, "%s: reading %s: %s\n", KMEM, 
                           refstr, strerror(errno));
            quit(23);
        }
    }
    return(1);
}
    
/* comparison routines for qsort */

/*
 * There are currently four possible comparison routines.  main selects
 * one of these by indexing in to the array proc_compares.
 *
 * Possible keys are defined as macros below.  Currently these keys are
 * defined:  percent cpu, cpu ticks, process state, resident set size,
 * total virtual memory usage.  The process states are ordered as follows
 * (from least to most important):  WAIT, zombie, sleep, stop, start, run.
 * The array declaration below maps a process state index into a number
 * that reflects this ordering.
 */

/* First, the possible comparison keys.  These are defined in such a way
   that they can be merely listed in the source code to define the actual
   desired ordering.
 */

#define ORDERKEY_PCTCPU  if (lresult = p2->p_pctcpu - p1->p_pctcpu,\
                           (result = lresult > 0 ? 1 : lresult < 0 ? -1 : 0) == 0)
#define ORDERKEY_CPTICKS if ((result = PROCTIME(p2) - PROCTIME(p1)) == 0)
#define ORDERKEY_STATE   if ((result = sorted_state[p2->p_stat] - \
                            sorted_state[p1->p_stat])  == 0)
#define ORDERKEY_PRIO    if ((result = p2->p_pri - p1->p_pri) == 0)
#define ORDERKEY_RSSIZE  if ((result = p2->p_rssize - p1->p_rssize) == 0)
#define ORDERKEY_MEM     if ((result = PROCSIZE(p2) - PROCSIZE(p1)) == 0)

/* Now the array that maps process state to a weight */

static unsigned char sorted_state[] =
{
    0,  /* not used             */
    3,  /* sleep                */
    1,  /* ABANDONED (WAIT)     */
    6,  /* run                  */
    5,  /* start                */
    2,  /* zombie               */
    4   /* stop                 */
};
 
/* compare_cpu - the comparison function for sorting by cpu percentage */

compare_cpu(pp1, pp2)

struct proc **pp1;
struct proc **pp2;

{
    register struct proc *p1;
    register struct proc *p2;
    register int result;
    register pctcpu lresult;

    /* remove one level of indirection */
    p1 = *pp1;
    p2 = *pp2;

    ORDERKEY_PCTCPU
    ORDERKEY_CPTICKS
    ORDERKEY_STATE
    ORDERKEY_PRIO
    ORDERKEY_RSSIZE
    ORDERKEY_MEM
    ;

    return(result);
}

/* compare_size - the comparison function for sorting by total memory usage */

compare_size(pp1, pp2)

struct proc **pp1;
struct proc **pp2;

{
    register struct proc *p1;
    register struct proc *p2;
    register int result;
    register pctcpu lresult;

    /* remove one level of indirection */
    p1 = *pp1;
    p2 = *pp2;

    ORDERKEY_MEM
    ORDERKEY_RSSIZE
    ORDERKEY_PCTCPU
    ORDERKEY_CPTICKS
    ORDERKEY_STATE
    ORDERKEY_PRIO
    ;

    return(result);
}

/* compare_res - the comparison function for sorting by resident set size */

compare_res(pp1, pp2)

struct proc **pp1;
struct proc **pp2;

{
    register struct proc *p1;
    register struct proc *p2;
    register int result;
    register pctcpu lresult;

    /* remove one level of indirection */
    p1 = *pp1;
    p2 = *pp2;

    ORDERKEY_RSSIZE
    ORDERKEY_MEM
    ORDERKEY_PCTCPU
    ORDERKEY_CPTICKS
    ORDERKEY_STATE
    ORDERKEY_PRIO
    ;

    return(result);
}

/* compare_time - the comparison function for sorting by total cpu time */

compare_time(pp1, pp2)

struct proc **pp1;
struct proc **pp2;

{
    register struct proc *p1;
    register struct proc *p2;
    register int result;
    register pctcpu lresult;

    /* remove one level of indirection */
    p1 = *pp1;
    p2 = *pp2;

    ORDERKEY_CPTICKS
    ORDERKEY_PCTCPU
    ORDERKEY_STATE
    ORDERKEY_PRIO
    ORDERKEY_RSSIZE
    ORDERKEY_MEM
    ;
  
    return(result);
}

/*
 * proc_owner(pid) - returns the uid that owns process "pid", or -1 if
 *              the process does not exist.
 *              It is EXTREMLY IMPORTANT that this function work correctly.
 *              If top runs setuid root (as in SVR4), then this function
 *              is the only thing that stands in the way of a serious
 *              security problem.  It validates requests for the "kill"
 *              and "renice" commands.
 */

int proc_owner(pid)

int pid;

{
    int cnt;
    struct proc **prefp;
    struct proc *pp;

    prefp = pref;
    cnt = pref_len;
    while (--cnt >= 0)
    {
        if ((pp = *prefp++)->p_pid == (pid_t)pid)
        {
            return((int)pp->p_uid);
        }
    }
    return(-1);
}