Ignore machine-check MSRs

[freebsd-src/fkvm-freebsd.git] / lib / libkvm / kvm_proc.c

/*-
 * Copyright (c) 1989, 1992, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software developed by the Computer Systems
 * Engineering group at Lawrence Berkeley Laboratory under DARPA contract
 * BG 91-66 and contributed to Berkeley.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#if 0
#if defined(LIBC_SCCS) && !defined(lint)
static char sccsid[] = "@(#)kvm_proc.c  8.3 (Berkeley) 9/23/93";
#endif /* LIBC_SCCS and not lint */
#endif

#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");

/*
 * Proc traversal interface for kvm.  ps and w are (probably) the exclusive
 * users of this code, so we've factored it out into a separate module.
 * Thus, we keep this grunge out of the other kvm applications (i.e.,
 * most other applications are interested only in open/close/read/nlist).
 */

#include <sys/param.h>
#define _WANT_UCRED     /* make ucred.h give us 'struct ucred' */
#include <sys/ucred.h>
#include <sys/queue.h>
#include <sys/_lock.h>
#include <sys/_mutex.h>
#include <sys/_task.h>
#define _WANT_PRISON    /* make jail.h give us 'struct prison' */
#include <sys/jail.h>
#include <sys/user.h>
#include <sys/proc.h>
#include <sys/exec.h>
#include <sys/stat.h>
#include <sys/sysent.h>
#include <sys/ioctl.h>
#include <sys/tty.h>
#include <sys/file.h>
#include <sys/conf.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <nlist.h>
#include <kvm.h>

#include <vm/vm.h>
#include <vm/vm_param.h>

#include <sys/sysctl.h>

#include <limits.h>
#include <memory.h>
#include <paths.h>

#include "kvm_private.h"

#define KREAD(kd, addr, obj) \
        (kvm_read(kd, addr, (char *)(obj), sizeof(*obj)) != sizeof(*obj))

static int ticks;
static int hz;

/*
 * Read proc's from memory file into buffer bp, which has space to hold
 * at most maxcnt procs.
 */
static int
kvm_proclist(kd, what, arg, p, bp, maxcnt)
        kvm_t *kd;
        int what, arg;
        struct proc *p;
        struct kinfo_proc *bp;
        int maxcnt;
{
        int cnt = 0;
        struct kinfo_proc kinfo_proc, *kp;
        struct pgrp pgrp;
        struct session sess;
        struct cdev t_cdev;
        struct tty tty;
        struct vmspace vmspace;
        struct sigacts sigacts;
        struct pstats pstats;
        struct ucred ucred;
        struct prison pr;
        struct thread mtd;
        struct proc proc;
        struct proc pproc;
        struct timeval tv;
        struct sysentvec sysent;
        char svname[KI_EMULNAMELEN];

        kp = &kinfo_proc;
        kp->ki_structsize = sizeof(kinfo_proc);
        /*
         * Loop on the processes. this is completely broken because we need to be
         * able to loop on the threads and merge the ones that are the same process some how.
         */
        for (; cnt < maxcnt && p != NULL; p = LIST_NEXT(&proc, p_list)) {
                memset(kp, 0, sizeof *kp);
                if (KREAD(kd, (u_long)p, &proc)) {
                        _kvm_err(kd, kd->program, "can't read proc at %x", p);
                        return (-1);
                }
                if (proc.p_state != PRS_ZOMBIE) {
                        if (KREAD(kd, (u_long)TAILQ_FIRST(&proc.p_threads),
                            &mtd)) {
                                _kvm_err(kd, kd->program,
                                    "can't read thread at %x",
                                    TAILQ_FIRST(&proc.p_threads));
                                return (-1);
                        }
                }
                if (KREAD(kd, (u_long)proc.p_ucred, &ucred) == 0) {
                        kp->ki_ruid = ucred.cr_ruid;
                        kp->ki_svuid = ucred.cr_svuid;
                        kp->ki_rgid = ucred.cr_rgid;
                        kp->ki_svgid = ucred.cr_svgid;
                        kp->ki_ngroups = ucred.cr_ngroups;
                        bcopy(ucred.cr_groups, kp->ki_groups,
                            NGROUPS * sizeof(gid_t));
                        kp->ki_uid = ucred.cr_uid;
                        if (ucred.cr_prison != NULL) {
                                if (KREAD(kd, (u_long)ucred.cr_prison, &pr)) {
                                        _kvm_err(kd, kd->program,
                                            "can't read prison at %x",
                                            ucred.cr_prison);
                                        return (-1);
                                }
                                kp->ki_jid = pr.pr_id;
                        }
                }

                switch(what & ~KERN_PROC_INC_THREAD) {

                case KERN_PROC_GID:
                        if (kp->ki_groups[0] != (gid_t)arg)
                                continue;
                        break;

                case KERN_PROC_PID:
                        if (proc.p_pid != (pid_t)arg)
                                continue;
                        break;

                case KERN_PROC_RGID:
                        if (kp->ki_rgid != (gid_t)arg)
                                continue;
                        break;

                case KERN_PROC_UID:
                        if (kp->ki_uid != (uid_t)arg)
                                continue;
                        break;

                case KERN_PROC_RUID:
                        if (kp->ki_ruid != (uid_t)arg)
                                continue;
                        break;
                }
                /*
                 * We're going to add another proc to the set.  If this
                 * will overflow the buffer, assume the reason is because
                 * nprocs (or the proc list) is corrupt and declare an error.
                 */
                if (cnt >= maxcnt) {
                        _kvm_err(kd, kd->program, "nprocs corrupt");
                        return (-1);
                }
                /*
                 * gather kinfo_proc
                 */
                kp->ki_paddr = p;
                kp->ki_addr = 0;        /* XXX uarea */
                /* kp->ki_kstack = proc.p_thread.td_kstack; XXXKSE */
                kp->ki_args = proc.p_args;
                kp->ki_tracep = proc.p_tracevp;
                kp->ki_textvp = proc.p_textvp;
                kp->ki_fd = proc.p_fd;
                kp->ki_vmspace = proc.p_vmspace;
                if (proc.p_sigacts != NULL) {
                        if (KREAD(kd, (u_long)proc.p_sigacts, &sigacts)) {
                                _kvm_err(kd, kd->program,
                                    "can't read sigacts at %x", proc.p_sigacts);
                                return (-1);
                        }
                        kp->ki_sigignore = sigacts.ps_sigignore;
                        kp->ki_sigcatch = sigacts.ps_sigcatch;
                }
#if 0
                if ((proc.p_flag & P_INMEM) && proc.p_stats != NULL) {
                        if (KREAD(kd, (u_long)proc.p_stats, &pstats)) {
                                _kvm_err(kd, kd->program,
                                    "can't read stats at %x", proc.p_stats);
                                return (-1);
                        }
                        kp->ki_start = pstats.p_start;

                        /*
                         * XXX: The times here are probably zero and need
                         * to be calculated from the raw data in p_rux and
                         * p_crux.
                         */
                        kp->ki_rusage = pstats.p_ru;
                        kp->ki_childstime = pstats.p_cru.ru_stime;
                        kp->ki_childutime = pstats.p_cru.ru_utime;
                        /* Some callers want child-times in a single value */
                        timeradd(&kp->ki_childstime, &kp->ki_childutime,
                            &kp->ki_childtime);
                }
#endif
                if (proc.p_oppid)
                        kp->ki_ppid = proc.p_oppid;
                else if (proc.p_pptr) {
                        if (KREAD(kd, (u_long)proc.p_pptr, &pproc)) {
                                _kvm_err(kd, kd->program,
                                    "can't read pproc at %x", proc.p_pptr);
                                return (-1);
                        }
                        kp->ki_ppid = pproc.p_pid;
                } else 
                        kp->ki_ppid = 0;
                if (proc.p_pgrp == NULL)
                        goto nopgrp;
                if (KREAD(kd, (u_long)proc.p_pgrp, &pgrp)) {
                        _kvm_err(kd, kd->program, "can't read pgrp at %x",
                                 proc.p_pgrp);
                        return (-1);
                }
                kp->ki_pgid = pgrp.pg_id;
                kp->ki_jobc = pgrp.pg_jobc;
                if (KREAD(kd, (u_long)pgrp.pg_session, &sess)) {
                        _kvm_err(kd, kd->program, "can't read session at %x",
                                pgrp.pg_session);
                        return (-1);
                }
                kp->ki_sid = sess.s_sid;
                (void)memcpy(kp->ki_login, sess.s_login,
                                                sizeof(kp->ki_login));
                kp->ki_kiflag = sess.s_ttyvp ? KI_CTTY : 0;
                if (sess.s_leader == p)
                        kp->ki_kiflag |= KI_SLEADER;
                if ((proc.p_flag & P_CONTROLT) && sess.s_ttyp != NULL) {
                        if (KREAD(kd, (u_long)sess.s_ttyp, &tty)) {
                                _kvm_err(kd, kd->program,
                                         "can't read tty at %x", sess.s_ttyp);
                                return (-1);
                        }
                        if (tty.t_dev != NULL) {
                                if (KREAD(kd, (u_long)tty.t_dev, &t_cdev)) {
                                        _kvm_err(kd, kd->program,
                                                 "can't read cdev at %x",
                                                tty.t_dev);
                                        return (-1);
                                }
#if 0
                                kp->ki_tdev = t_cdev.si_udev;
#else
                                kp->ki_tdev = NODEV;
#endif
                        }
                        if (tty.t_pgrp != NULL) {
                                if (KREAD(kd, (u_long)tty.t_pgrp, &pgrp)) {
                                        _kvm_err(kd, kd->program,
                                                 "can't read tpgrp at %x",
                                                tty.t_pgrp);
                                        return (-1);
                                }
                                kp->ki_tpgid = pgrp.pg_id;
                        } else
                                kp->ki_tpgid = -1;
                        if (tty.t_session != NULL) {
                                if (KREAD(kd, (u_long)tty.t_session, &sess)) {
                                        _kvm_err(kd, kd->program,
                                            "can't read session at %x",
                                            tty.t_session);
                                        return (-1);
                                }
                                kp->ki_tsid = sess.s_sid;
                        }
                } else {
nopgrp:
                        kp->ki_tdev = NODEV;
                }
                if ((proc.p_state != PRS_ZOMBIE) && mtd.td_wmesg)
                        (void)kvm_read(kd, (u_long)mtd.td_wmesg,
                            kp->ki_wmesg, WMESGLEN);

                (void)kvm_read(kd, (u_long)proc.p_vmspace,
                    (char *)&vmspace, sizeof(vmspace));
                kp->ki_size = vmspace.vm_map.size;
                kp->ki_rssize = vmspace.vm_swrss; /* XXX */
                kp->ki_swrss = vmspace.vm_swrss;
                kp->ki_tsize = vmspace.vm_tsize;
                kp->ki_dsize = vmspace.vm_dsize;
                kp->ki_ssize = vmspace.vm_ssize;

                switch (what & ~KERN_PROC_INC_THREAD) {

                case KERN_PROC_PGRP:
                        if (kp->ki_pgid != (pid_t)arg)
                                continue;
                        break;

                case KERN_PROC_SESSION:
                        if (kp->ki_sid != (pid_t)arg)
                                continue;
                        break;

                case KERN_PROC_TTY:
                        if ((proc.p_flag & P_CONTROLT) == 0 ||
                             kp->ki_tdev != (dev_t)arg)
                                continue;
                        break;
                }
                if (proc.p_comm[0] != 0)
                        strlcpy(kp->ki_comm, proc.p_comm, MAXCOMLEN);
                (void)kvm_read(kd, (u_long)proc.p_sysent, (char *)&sysent,
                    sizeof(sysent));
                (void)kvm_read(kd, (u_long)sysent.sv_name, (char *)&svname,
                    sizeof(svname));
                if (svname[0] != 0)
                        strlcpy(kp->ki_emul, svname, KI_EMULNAMELEN);
                if ((proc.p_state != PRS_ZOMBIE) &&
                    (mtd.td_blocked != 0)) {
                        kp->ki_kiflag |= KI_LOCKBLOCK;
                        if (mtd.td_lockname)
                                (void)kvm_read(kd,
                                    (u_long)mtd.td_lockname,
                                    kp->ki_lockname, LOCKNAMELEN);
                        kp->ki_lockname[LOCKNAMELEN] = 0;
                }
                /*
                 * XXX: This is plain wrong, rux_runtime has nothing
                 * to do with struct bintime, rux_runtime is just a 64-bit
                 * integer counter of cputicks.  What we need here is a way
                 * to convert cputicks to usecs.  The kernel does it in
                 * kern/kern_tc.c, but the function can't be just copied.
                 */
                bintime2timeval(&proc.p_rux.rux_runtime, &tv);
                kp->ki_runtime = (u_int64_t)tv.tv_sec * 1000000 + tv.tv_usec;
                kp->ki_pid = proc.p_pid;
                kp->ki_siglist = proc.p_siglist;
                SIGSETOR(kp->ki_siglist, mtd.td_siglist);
                kp->ki_sigmask = mtd.td_sigmask;
                kp->ki_xstat = proc.p_xstat;
                kp->ki_acflag = proc.p_acflag;
                kp->ki_lock = proc.p_lock;
                if (proc.p_state != PRS_ZOMBIE) {
                        kp->ki_swtime = (ticks - proc.p_swtick) / hz;
                        kp->ki_flag = proc.p_flag;
                        kp->ki_sflag = 0;
                        kp->ki_nice = proc.p_nice;
                        kp->ki_traceflag = proc.p_traceflag;
                        if (proc.p_state == PRS_NORMAL) { 
                                if (TD_ON_RUNQ(&mtd) ||
                                    TD_CAN_RUN(&mtd) ||
                                    TD_IS_RUNNING(&mtd)) {
                                        kp->ki_stat = SRUN;
                                } else if (mtd.td_state == 
                                    TDS_INHIBITED) {
                                        if (P_SHOULDSTOP(&proc)) {
                                                kp->ki_stat = SSTOP;
                                        } else if (
                                            TD_IS_SLEEPING(&mtd)) {
                                                kp->ki_stat = SSLEEP;
                                        } else if (TD_ON_LOCK(&mtd)) {
                                                kp->ki_stat = SLOCK;
                                        } else {
                                                kp->ki_stat = SWAIT;
                                        }
                                }
                        } else {
                                kp->ki_stat = SIDL;
                        }
                        /* Stuff from the thread */
                        kp->ki_pri.pri_level = mtd.td_priority;
                        kp->ki_pri.pri_native = mtd.td_base_pri;
                        kp->ki_lastcpu = mtd.td_lastcpu;
                        kp->ki_wchan = mtd.td_wchan;
                        if (mtd.td_name[0] != 0)
                                strlcpy(kp->ki_ocomm, mtd.td_name, MAXCOMLEN);
                        kp->ki_oncpu = mtd.td_oncpu;
                        if (mtd.td_name[0] != '\0')
                                strlcpy(kp->ki_ocomm, mtd.td_name, sizeof(kp->ki_ocomm));
                        kp->ki_pctcpu = 0;
                        kp->ki_rqindex = 0;
                } else {
                        kp->ki_stat = SZOMB;
                }
                bcopy(&kinfo_proc, bp, sizeof(kinfo_proc));
                ++bp;
                ++cnt;
        }
        return (cnt);
}

/*
 * Build proc info array by reading in proc list from a crash dump.
 * Return number of procs read.  maxcnt is the max we will read.
 */
static int
kvm_deadprocs(kd, what, arg, a_allproc, a_zombproc, maxcnt)
        kvm_t *kd;
        int what, arg;
        u_long a_allproc;
        u_long a_zombproc;
        int maxcnt;
{
        struct kinfo_proc *bp = kd->procbase;
        int acnt, zcnt;
        struct proc *p;

        if (KREAD(kd, a_allproc, &p)) {
                _kvm_err(kd, kd->program, "cannot read allproc");
                return (-1);
        }
        acnt = kvm_proclist(kd, what, arg, p, bp, maxcnt);
        if (acnt < 0)
                return (acnt);

        if (KREAD(kd, a_zombproc, &p)) {
                _kvm_err(kd, kd->program, "cannot read zombproc");
                return (-1);
        }
        zcnt = kvm_proclist(kd, what, arg, p, bp + acnt, maxcnt - acnt);
        if (zcnt < 0)
                zcnt = 0;

        return (acnt + zcnt);
}

struct kinfo_proc *
kvm_getprocs(kd, op, arg, cnt)
        kvm_t *kd;
        int op, arg;
        int *cnt;
{
        int mib[4], st, nprocs;
        size_t size;
        int temp_op;

        if (kd->procbase != 0) {
                free((void *)kd->procbase);
                /*
                 * Clear this pointer in case this call fails.  Otherwise,
                 * kvm_close() will free it again.
                 */
                kd->procbase = 0;
        }
        if (ISALIVE(kd)) {
                size = 0;
                mib[0] = CTL_KERN;
                mib[1] = KERN_PROC;
                mib[2] = op;
                mib[3] = arg;
                temp_op = op & ~KERN_PROC_INC_THREAD;
                st = sysctl(mib,
                    temp_op == KERN_PROC_ALL || temp_op == KERN_PROC_PROC ?
                    3 : 4, NULL, &size, NULL, 0);
                if (st == -1) {
                        _kvm_syserr(kd, kd->program, "kvm_getprocs");
                        return (0);
                }
                /*
                 * We can't continue with a size of 0 because we pass
                 * it to realloc() (via _kvm_realloc()), and passing 0
                 * to realloc() results in undefined behavior.
                 */
                if (size == 0) {
                        /*
                         * XXX: We should probably return an invalid,
                         * but non-NULL, pointer here so any client
                         * program trying to dereference it will
                         * crash.  However, _kvm_freeprocs() calls
                         * free() on kd->procbase if it isn't NULL,
                         * and free()'ing a junk pointer isn't good.
                         * Then again, _kvm_freeprocs() isn't used
                         * anywhere . . .
                         */
                        kd->procbase = _kvm_malloc(kd, 1);
                        goto liveout;
                }
                do {
                        size += size / 10;
                        kd->procbase = (struct kinfo_proc *)
                            _kvm_realloc(kd, kd->procbase, size);
                        if (kd->procbase == 0)
                                return (0);
                        st = sysctl(mib, temp_op == KERN_PROC_ALL ||
                            temp_op == KERN_PROC_PROC ? 3 : 4,
                            kd->procbase, &size, NULL, 0);
                } while (st == -1 && errno == ENOMEM);
                if (st == -1) {
                        _kvm_syserr(kd, kd->program, "kvm_getprocs");
                        return (0);
                }
                /*
                 * We have to check the size again because sysctl()
                 * may "round up" oldlenp if oldp is NULL; hence it
                 * might've told us that there was data to get when
                 * there really isn't any.
                 */
                if (size > 0 &&
                    kd->procbase->ki_structsize != sizeof(struct kinfo_proc)) {
                        _kvm_err(kd, kd->program,
                            "kinfo_proc size mismatch (expected %d, got %d)",
                            sizeof(struct kinfo_proc),
                            kd->procbase->ki_structsize);
                        return (0);
                }
liveout:
                nprocs = size == 0 ? 0 : size / kd->procbase->ki_structsize;
        } else {
                struct nlist nl[6], *p;

                nl[0].n_name = "_nprocs";
                nl[1].n_name = "_allproc";
                nl[2].n_name = "_zombproc";
                nl[3].n_name = "_ticks";
                nl[4].n_name = "_hz";
                nl[5].n_name = 0;

                if (kvm_nlist(kd, nl) != 0) {
                        for (p = nl; p->n_type != 0; ++p)
                                ;
                        _kvm_err(kd, kd->program,
                                 "%s: no such symbol", p->n_name);
                        return (0);
                }
                if (KREAD(kd, nl[0].n_value, &nprocs)) {
                        _kvm_err(kd, kd->program, "can't read nprocs");
                        return (0);
                }
                if (KREAD(kd, nl[3].n_value, &ticks)) {
                        _kvm_err(kd, kd->program, "can't read ticks");
                        return (0);
                }
                if (KREAD(kd, nl[4].n_value, &hz)) {
                        _kvm_err(kd, kd->program, "can't read hz");
                        return (0);
                }
                size = nprocs * sizeof(struct kinfo_proc);
                kd->procbase = (struct kinfo_proc *)_kvm_malloc(kd, size);
                if (kd->procbase == 0)
                        return (0);

                nprocs = kvm_deadprocs(kd, op, arg, nl[1].n_value,
                                      nl[2].n_value, nprocs);
#ifdef notdef
                size = nprocs * sizeof(struct kinfo_proc);
                (void)realloc(kd->procbase, size);
#endif
        }
        *cnt = nprocs;
        return (kd->procbase);
}

void
_kvm_freeprocs(kd)
        kvm_t *kd;
{
        if (kd->procbase) {
                free(kd->procbase);
                kd->procbase = 0;
        }
}

void *
_kvm_realloc(kd, p, n)
        kvm_t *kd;
        void *p;
        size_t n;
{
        void *np = (void *)realloc(p, n);

        if (np == 0) {
                free(p);
                _kvm_err(kd, kd->program, "out of memory");
        }
        return (np);
}

#ifndef MAX
#define MAX(a, b) ((a) > (b) ? (a) : (b))
#endif

/*
 * Read in an argument vector from the user address space of process kp.
 * addr if the user-space base address of narg null-terminated contiguous
 * strings.  This is used to read in both the command arguments and
 * environment strings.  Read at most maxcnt characters of strings.
 */
static char **
kvm_argv(kd, kp, addr, narg, maxcnt)
        kvm_t *kd;
        struct kinfo_proc *kp;
        u_long addr;
        int narg;
        int maxcnt;
{
        char *np, *cp, *ep, *ap;
        u_long oaddr = -1;
        int len, cc;
        char **argv;

        /*
         * Check that there aren't an unreasonable number of agruments,
         * and that the address is in user space.
         */
        if (narg > 512 || addr < VM_MIN_ADDRESS || addr >= VM_MAXUSER_ADDRESS)
                return (0);

        /*
         * kd->argv : work space for fetching the strings from the target 
         *            process's space, and is converted for returning to caller
         */
        if (kd->argv == 0) {
                /*
                 * Try to avoid reallocs.
                 */
                kd->argc = MAX(narg + 1, 32);
                kd->argv = (char **)_kvm_malloc(kd, kd->argc *
                                                sizeof(*kd->argv));
                if (kd->argv == 0)
                        return (0);
        } else if (narg + 1 > kd->argc) {
                kd->argc = MAX(2 * kd->argc, narg + 1);
                kd->argv = (char **)_kvm_realloc(kd, kd->argv, kd->argc *
                                                sizeof(*kd->argv));
                if (kd->argv == 0)
                        return (0);
        }
        /*
         * kd->argspc : returned to user, this is where the kd->argv
         *              arrays are left pointing to the collected strings.
         */
        if (kd->argspc == 0) {
                kd->argspc = (char *)_kvm_malloc(kd, PAGE_SIZE);
                if (kd->argspc == 0)
                        return (0);
                kd->arglen = PAGE_SIZE;
        }
        /*
         * kd->argbuf : used to pull in pages from the target process.
         *              the strings are copied out of here.
         */
        if (kd->argbuf == 0) {
                kd->argbuf = (char *)_kvm_malloc(kd, PAGE_SIZE);
                if (kd->argbuf == 0)
                        return (0);
        }

        /* Pull in the target process'es argv vector */
        cc = sizeof(char *) * narg;
        if (kvm_uread(kd, kp, addr, (char *)kd->argv, cc) != cc)
                return (0);
        /*
         * ap : saved start address of string we're working on in kd->argspc
         * np : pointer to next place to write in kd->argspc
         * len: length of data in kd->argspc
         * argv: pointer to the argv vector that we are hunting around the
         *       target process space for, and converting to addresses in
         *       our address space (kd->argspc).
         */
        ap = np = kd->argspc;
        argv = kd->argv;
        len = 0;
        /*
         * Loop over pages, filling in the argument vector.
         * Note that the argv strings could be pointing *anywhere* in
         * the user address space and are no longer contiguous.
         * Note that *argv is modified when we are going to fetch a string
         * that crosses a page boundary.  We copy the next part of the string
         * into to "np" and eventually convert the pointer.
         */
        while (argv < kd->argv + narg && *argv != 0) {

                /* get the address that the current argv string is on */
                addr = (u_long)*argv & ~(PAGE_SIZE - 1);

                /* is it the same page as the last one? */
                if (addr != oaddr) {
                        if (kvm_uread(kd, kp, addr, kd->argbuf, PAGE_SIZE) !=
                            PAGE_SIZE)
                                return (0);
                        oaddr = addr;
                }

                /* offset within the page... kd->argbuf */
                addr = (u_long)*argv & (PAGE_SIZE - 1);

                /* cp = start of string, cc = count of chars in this chunk */
                cp = kd->argbuf + addr;
                cc = PAGE_SIZE - addr;

                /* dont get more than asked for by user process */
                if (maxcnt > 0 && cc > maxcnt - len)
                        cc = maxcnt - len;

                /* pointer to end of string if we found it in this page */
                ep = memchr(cp, '\0', cc);
                if (ep != 0)
                        cc = ep - cp + 1;
                /*
                 * at this point, cc is the count of the chars that we are
                 * going to retrieve this time. we may or may not have found
                 * the end of it.  (ep points to the null if the end is known)
                 */

                /* will we exceed the malloc/realloced buffer? */
                if (len + cc > kd->arglen) {
                        int off;
                        char **pp;
                        char *op = kd->argspc;

                        kd->arglen *= 2;
                        kd->argspc = (char *)_kvm_realloc(kd, kd->argspc,
                                                          kd->arglen);
                        if (kd->argspc == 0)
                                return (0);
                        /*
                         * Adjust argv pointers in case realloc moved
                         * the string space.
                         */
                        off = kd->argspc - op;
                        for (pp = kd->argv; pp < argv; pp++)
                                *pp += off;
                        ap += off;
                        np += off;
                }
                /* np = where to put the next part of the string in kd->argspc*/
                /* np is kinda redundant.. could use "kd->argspc + len" */
                memcpy(np, cp, cc);
                np += cc;       /* inc counters */
                len += cc;

                /*
                 * if end of string found, set the *argv pointer to the
                 * saved beginning of string, and advance. argv points to
                 * somewhere in kd->argv..  This is initially relative
                 * to the target process, but when we close it off, we set
                 * it to point in our address space.
                 */
                if (ep != 0) {
                        *argv++ = ap;
                        ap = np;
                } else {
                        /* update the address relative to the target process */
                        *argv += cc;
                }

                if (maxcnt > 0 && len >= maxcnt) {
                        /*
                         * We're stopping prematurely.  Terminate the
                         * current string.
                         */
                        if (ep == 0) {
                                *np = '\0';
                                *argv++ = ap;
                        }
                        break;
                }
        }
        /* Make sure argv is terminated. */
        *argv = 0;
        return (kd->argv);
}

static void
ps_str_a(p, addr, n)
        struct ps_strings *p;
        u_long *addr;
        int *n;
{
        *addr = (u_long)p->ps_argvstr;
        *n = p->ps_nargvstr;
}

static void
ps_str_e(p, addr, n)
        struct ps_strings *p;
        u_long *addr;
        int *n;
{
        *addr = (u_long)p->ps_envstr;
        *n = p->ps_nenvstr;
}

/*
 * Determine if the proc indicated by p is still active.
 * This test is not 100% foolproof in theory, but chances of
 * being wrong are very low.
 */
static int
proc_verify(curkp)
        struct kinfo_proc *curkp;
{
        struct kinfo_proc newkp;
        int mib[4];
        size_t len;

        mib[0] = CTL_KERN;
        mib[1] = KERN_PROC;
        mib[2] = KERN_PROC_PID;
        mib[3] = curkp->ki_pid;
        len = sizeof(newkp);
        if (sysctl(mib, 4, &newkp, &len, NULL, 0) == -1)
                return (0);
        return (curkp->ki_pid == newkp.ki_pid &&
            (newkp.ki_stat != SZOMB || curkp->ki_stat == SZOMB));
}

static char **
kvm_doargv(kd, kp, nchr, info)
        kvm_t *kd;
        struct kinfo_proc *kp;
        int nchr;
        void (*info)(struct ps_strings *, u_long *, int *);
{
        char **ap;
        u_long addr;
        int cnt;
        static struct ps_strings arginfo;
        static u_long ps_strings;
        size_t len;

        if (ps_strings == 0) {
                len = sizeof(ps_strings);
                if (sysctlbyname("kern.ps_strings", &ps_strings, &len, NULL,
                    0) == -1)
                        ps_strings = PS_STRINGS;
        }

        /*
         * Pointers are stored at the top of the user stack.
         */
        if (kp->ki_stat == SZOMB ||
            kvm_uread(kd, kp, ps_strings, (char *)&arginfo,
                      sizeof(arginfo)) != sizeof(arginfo))
                return (0);

        (*info)(&arginfo, &addr, &cnt);
        if (cnt == 0)
                return (0);
        ap = kvm_argv(kd, kp, addr, cnt, nchr);
        /*
         * For live kernels, make sure this process didn't go away.
         */
        if (ap != 0 && ISALIVE(kd) && !proc_verify(kp))
                ap = 0;
        return (ap);
}

/*
 * Get the command args.  This code is now machine independent.
 */
char **
kvm_getargv(kd, kp, nchr)
        kvm_t *kd;
        const struct kinfo_proc *kp;
        int nchr;
{
        int oid[4];
        int i;
        size_t bufsz;
        static unsigned long buflen;
        static char *buf, *p;
        static char **bufp;
        static int argc;

        if (!ISALIVE(kd)) {
                _kvm_err(kd, kd->program,
                    "cannot read user space from dead kernel");
                return (0);
        }

        if (!buflen) {
                bufsz = sizeof(buflen);
                i = sysctlbyname("kern.ps_arg_cache_limit", 
                    &buflen, &bufsz, NULL, 0);
                if (i == -1) {
                        buflen = 0;
                } else {
                        buf = malloc(buflen);
                        if (buf == NULL)
                                buflen = 0;
                        argc = 32;
                        bufp = malloc(sizeof(char *) * argc);
                }
        }
        if (buf != NULL) {
                oid[0] = CTL_KERN;
                oid[1] = KERN_PROC;
                oid[2] = KERN_PROC_ARGS;
                oid[3] = kp->ki_pid;
                bufsz = buflen;
                i = sysctl(oid, 4, buf, &bufsz, 0, 0);
                if (i == 0 && bufsz > 0) {
                        i = 0;
                        p = buf;
                        do {
                                bufp[i++] = p;
                                p += strlen(p) + 1;
                                if (i >= argc) {
                                        argc += argc;
                                        bufp = realloc(bufp,
                                            sizeof(char *) * argc);
                                }
                        } while (p < buf + bufsz);
                        bufp[i++] = 0;
                        return (bufp);
                }
        }
        if (kp->ki_flag & P_SYSTEM)
                return (NULL);
        return (kvm_doargv(kd, kp, nchr, ps_str_a));
}

char **
kvm_getenvv(kd, kp, nchr)
        kvm_t *kd;
        const struct kinfo_proc *kp;
        int nchr;
{
        return (kvm_doargv(kd, kp, nchr, ps_str_e));
}

/*
 * Read from user space.  The user context is given by p.
 */
ssize_t
kvm_uread(kd, kp, uva, buf, len)
        kvm_t *kd;
        struct kinfo_proc *kp;
        u_long uva;
        char *buf;
        size_t len;
{
        char *cp;
        char procfile[MAXPATHLEN];
        ssize_t amount;
        int fd;

        if (!ISALIVE(kd)) {
                _kvm_err(kd, kd->program,
                    "cannot read user space from dead kernel");
                return (0);
        }

        sprintf(procfile, "/proc/%d/mem", kp->ki_pid);
        fd = open(procfile, O_RDONLY, 0);
        if (fd < 0) {
                _kvm_err(kd, kd->program, "cannot open %s", procfile);
                return (0);
        }

        cp = buf;
        while (len > 0) {
                errno = 0;
                if (lseek(fd, (off_t)uva, 0) == -1 && errno != 0) {
                        _kvm_err(kd, kd->program, "invalid address (%x) in %s",
                            uva, procfile);
                        break;
                }
                amount = read(fd, cp, len);
                if (amount < 0) {
                        _kvm_syserr(kd, kd->program, "error reading %s",
                            procfile);
                        break;
                }
                if (amount == 0) {
                        _kvm_err(kd, kd->program, "EOF reading %s", procfile);
                        break;
                }
                cp += amount;
                uva += amount;
                len -= amount;
        }

        close(fd);
        return ((ssize_t)(cp - buf));
}