/*
 * Copyright (c) 1993, 1995 Jan-Simon Pendry
 * Copyright (c) 1993, 1995
 *      The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Jan-Simon Pendry.
 *
 * 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.
 * 3. 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.
 *
 *      @(#)procfs_vnops.c      8.18 (Berkeley) 5/21/95
 *
 * $FreeBSD: src/sys/miscfs/procfs/procfs_vnops.c,v 1.76.2.7 2002/01/22 17:22:59 nectar Exp $
 */

/*
 * procfs vnode interface
 */

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/time.h>
#include <sys/kernel.h>
#include <sys/lock.h>
#include <sys/fcntl.h>
#include <sys/proc.h>
#include <sys/caps.h>
#include <sys/signalvar.h>
#include <sys/vnode.h>
#include <sys/uio.h>
#include <sys/mount.h>
#include <sys/namei.h>
#include <sys/dirent.h>
#include <sys/malloc.h>
#include <sys/reg.h>
#include <vm/vm_zone.h>
#include <vfs/procfs/procfs.h>
#include <sys/pioctl.h>

#include <sys/spinlock2.h>

#include <machine/limits.h>

static int      procfs_access (struct vop_access_args *);
static int      procfs_badop (struct vop_generic_args *);
static int      procfs_bmap (struct vop_bmap_args *);
static int      procfs_close (struct vop_close_args *);
static int      procfs_getattr (struct vop_getattr_args *);
static int      procfs_inactive (struct vop_inactive_args *);
static int      procfs_ioctl (struct vop_ioctl_args *);
static int      procfs_kqfilter (struct vop_kqfilter_args *);
static int      procfs_lookup (struct vop_old_lookup_args *);
static int      procfs_open (struct vop_open_args *);
static int      procfs_print (struct vop_print_args *);
static int      procfs_readdir (struct vop_readdir_args *);
static int      procfs_readlink (struct vop_readlink_args *);
static int      procfs_reclaim (struct vop_reclaim_args *);
static int      procfs_setattr (struct vop_setattr_args *);

static int      procfs_readdir_proc(struct vop_readdir_args *);
static int      procfs_readdir_root(struct vop_readdir_args *);

/*
 * procfs vnode operations.
 */
struct vop_ops procfs_vnode_vops = {
        .vop_default =          vop_defaultop,
        .vop_access =           procfs_access,
        .vop_advlock =          (void *)procfs_badop,
        .vop_bmap =             procfs_bmap,
        .vop_close =            procfs_close,
        .vop_old_create =       (void *)procfs_badop,
        .vop_getattr =          procfs_getattr,
        .vop_inactive =         procfs_inactive,
        .vop_old_link =         (void *)procfs_badop,
        .vop_old_lookup =       procfs_lookup,
        .vop_old_mkdir =        (void *)procfs_badop,
        .vop_old_mknod =        (void *)procfs_badop,
        .vop_open =             procfs_open,
        .vop_pathconf =         vop_stdpathconf,
        .vop_print =            procfs_print,
        .vop_read =             procfs_rw,
        .vop_readdir =          procfs_readdir,
        .vop_readlink =         procfs_readlink,
        .vop_reclaim =          procfs_reclaim,
        .vop_old_remove =       (void *)procfs_badop,
        .vop_old_rename =       (void *)procfs_badop,
        .vop_old_rmdir =        (void *)procfs_badop,
        .vop_setattr =          procfs_setattr,
        .vop_old_symlink =      (void *)procfs_badop,
        .vop_write =            (void *)procfs_rw,
        .vop_ioctl =            procfs_ioctl,
        .vop_kqfilter =         procfs_kqfilter,
};


/*
 * This is a list of the valid names in the
 * process-specific sub-directories.  It is
 * used in procfs_lookup and procfs_readdir
 */
static struct proc_target {
        u_char  pt_type;
        u_char  pt_namlen;
        char    *pt_name;
        pfstype pt_pfstype;
        int     (*pt_valid) (struct lwp *p);
} proc_targets[] = {
#define N(s) sizeof(s)-1, s
        /*        name          type            validp */
        { DT_DIR, N("."),       Pproc,          NULL },
        { DT_DIR, N(".."),      Proot,          NULL },
        { DT_REG, N("mem"),     Pmem,           NULL },
        { DT_REG, N("regs"),    Pregs,          procfs_validregs },
        { DT_REG, N("fpregs"),  Pfpregs,        procfs_validfpregs },
        { DT_REG, N("dbregs"),  Pdbregs,        procfs_validdbregs },
        { DT_REG, N("ctl"),     Pctl,           NULL },
        { DT_REG, N("status"),  Pstatus,        NULL },
        { DT_REG, N("note"),    Pnote,          NULL },
        { DT_REG, N("notepg"),  Pnotepg,        NULL },
        { DT_REG, N("map"),     Pmap,           procfs_validmap },
        { DT_REG, N("etype"),   Ptype,          procfs_validtype },
        { DT_REG, N("cmdline"), Pcmdline,       NULL },
        { DT_REG, N("rlimit"),  Prlimit,        NULL },
        { DT_LNK, N("file"),    Pfile,          NULL },
        { DT_LNK, N("exe"),     Pfile,          NULL },
#undef N
};
static const int nproc_targets = NELEM(proc_targets);

static pid_t atopid (const char *, u_int);

/*
 * set things up for doing i/o on
 * the pfsnode (vp).  (vp) is locked
 * on entry, and should be left locked
 * on exit.
 *
 * for procfs we don't need to do anything
 * in particular for i/o.  all that is done
 * is to support exclusive open on process
 * memory images.
 *
 * procfs_open(struct vnode *a_vp, int a_mode, struct ucred *a_cred,
 *             struct file *a_fp)
 */
static int
procfs_open(struct vop_open_args *ap)
{
        struct pfsnode *pfs = VTOPFS(ap->a_vp);
        struct proc *p1, *p2;
        int error;

        p2 = pfs_pfind(pfs->pfs_pid);
        if (p2 == NULL)
                return (ENOENT);
        if (pfs->pfs_pid && !PRISON_CHECK(ap->a_cred, p2->p_ucred)) {
                error = ENOENT;
                goto done;
        }

        switch (pfs->pfs_type) {
        case Pmem:
                if (((pfs->pfs_flags & FWRITE) && (ap->a_mode & O_EXCL)) ||
                    ((pfs->pfs_flags & O_EXCL) && (ap->a_mode & FWRITE))) {
                        error = EBUSY;
                        goto done;
                }

                p1 = curproc;
                KKASSERT(p1);
                /* Can't trace a process that's currently exec'ing. */
                if ((p2->p_flags & P_INEXEC) != 0) {
                        error = EAGAIN;
                        goto done;
                }
                if (!CHECKIO(p1, p2) || p_trespass(ap->a_cred, p2->p_ucred)) {
                        error = EPERM;
                        goto done;
                }

                if (ap->a_mode & FWRITE)
                        pfs->pfs_flags = ap->a_mode & (FWRITE|O_EXCL);

                break;

        default:
                break;
        }
        error = vop_stdopen(ap);
done:
        pfs_pdone(p2);
        return error;
}

/*
 * close the pfsnode (vp) after doing i/o.
 * (vp) is not locked on entry or exit.
 *
 * nothing to do for procfs other than undo
 * any exclusive open flag (see _open above).
 *
 * procfs_close(struct vnode *a_vp, int a_fflag, struct ucred *a_cred)
 */
static int
procfs_close(struct vop_close_args *ap)
{
        struct pfsnode *pfs = VTOPFS(ap->a_vp);
        struct proc *p;

        /*
         * Make sure the lock is exclusive for opencount tests
         */
        vn_lock(ap->a_vp, LK_UPGRADE | LK_RETRY);

        switch (pfs->pfs_type) {
        case Pmem:
                if ((ap->a_fflag & FWRITE) && (pfs->pfs_flags & O_EXCL))
                        pfs->pfs_flags &= ~(FWRITE|O_EXCL);
                /*
                 * v_opencount determines the last real close on the vnode.
                 *
                 * If this is the last close, then it checks to see if
                 * the target process has PF_LINGER set in p_pfsflags,
                 * if this is *not* the case, then the process' stop flags
                 * are cleared, and the process is woken up.  This is
                 * to help prevent the case where a process has been
                 * told to stop on an event, but then the requesting process
                 * has gone away or forgotten about it.
                 */
                p = NULL;
                if ((ap->a_vp->v_opencount < 2)
                    && ((p = pfs_pfind(pfs->pfs_pid)) != NULL ||
                        (p = pfs_zpfind(pfs->pfs_pid)) != NULL)
                    && !(p->p_pfsflags & PF_LINGER)) {
                        spin_lock(&p->p_spin);
                        p->p_stops = 0;
                        p->p_step = 0;
                        spin_unlock(&p->p_spin);
                        wakeup(&p->p_stype);
                        wakeup(&p->p_step);
                }
                pfs_pdone(p);
                break;
        default:
                break;
        }

        return (vop_stdclose(ap));
}

/*
 * do an ioctl operation on a pfsnode (vp).
 * (vp) is not locked on entry or exit.
 */
static int
procfs_ioctl(struct vop_ioctl_args *ap)
{
        struct pfsnode *pfs = VTOPFS(ap->a_vp);
        struct proc *procp;
        struct proc *p;
        int error;
        int signo;
        struct procfs_status *psp;
        unsigned char flags;

        procp = pfs_pfind(pfs->pfs_pid);
        if (procp == NULL)
                return ENOTTY;
        p = curproc;
        if (p == NULL) {
                error = EINVAL;
                goto done;
        }

        /* Can't trace a process that's currently exec'ing. */
        if ((procp->p_flags & P_INEXEC) != 0) {
                error = EAGAIN;
                goto done;
        }
        if (!CHECKIO(p, procp) || p_trespass(ap->a_cred, procp->p_ucred)) {
                error = EPERM;
                goto done;
        }

        switch (ap->a_command) {
        case PIOCBIS:
                spin_lock(&procp->p_spin);
                procp->p_stops |= *(unsigned int*)ap->a_data;
                spin_unlock(&procp->p_spin);
                break;
        case PIOCBIC:
                spin_lock(&procp->p_spin);
                procp->p_stops &= ~*(unsigned int*)ap->a_data;
                spin_unlock(&procp->p_spin);
                break;
        case PIOCSFL:
                /*
                * NFLAGS is "non-suser_xxx flags" -- currently, only
                * PFS_ISUGID ("ignore set u/g id");
                */
#define NFLAGS  (PF_ISUGID)
                flags = (unsigned char)*(unsigned int*)ap->a_data;
                if (flags & NFLAGS &&
                    (error = caps_priv_check(ap->a_cred,
                                             SYSCAP_RESTRICTEDROOT))) {
                        goto done;
                }
                procp->p_pfsflags = flags;
                break;
        case PIOCGFL:
                *(unsigned int*)ap->a_data = (unsigned int)procp->p_pfsflags;
                break;
        case PIOCSTATUS:
                /*
                * NOTE: syscall entry deals with stopevents and may run
                *       without the MP lock.
                */
                psp = (struct procfs_status *)ap->a_data;
                psp->flags = procp->p_pfsflags;
                psp->events = procp->p_stops;
                spin_lock(&procp->p_spin);
                if (procp->p_step) {
                        psp->state = 0;
                        psp->why = procp->p_stype;
                        psp->val = procp->p_xstat;
                        spin_unlock(&procp->p_spin);
                } else {
                        psp->state = 1;
                        spin_unlock(&procp->p_spin);
                        psp->why = 0;   /* Not defined values */
                        psp->val = 0;   /* Not defined values */
                }
                break;
        case PIOCWAIT:
                /*
                * NOTE: syscall entry deals with stopevents and may run
                *       without the MP lock.
                */
                psp = (struct procfs_status *)ap->a_data;
                spin_lock(&procp->p_spin);
                while (procp->p_step == 0) {
                        tsleep_interlock(&procp->p_stype, PCATCH);
                        spin_unlock(&procp->p_spin);
                        if (procp->p_stops == 0) {
                                error = 0;
                                goto done;
                        }
                        if (procp->p_flags & P_POSTEXIT) {
                                error = EINVAL;
                                goto done;
                        }
                        if (procp->p_flags & P_INEXEC) {
                                error = EAGAIN;
                                goto done;
                        }
                        error = tsleep(&procp->p_stype, PCATCH | PINTERLOCKED,
                                       "piocwait", 0);
                        if (error)
                                goto done;
                        spin_lock(&procp->p_spin);
                }
                spin_unlock(&procp->p_spin);
                psp->state = 1; /* It stopped */
                psp->flags = procp->p_pfsflags;
                psp->events = procp->p_stops;
                psp->why = procp->p_stype;      /* why it stopped */
                psp->val = procp->p_xstat;      /* any extra info */
                break;
        case PIOCCONT:  /* Restart a proc */
                /*
                * NOTE: syscall entry deals with stopevents and may run
                *       without the MP lock.  However, the caller is
                *       presumably interlocked by having waited.
                */
                if (procp->p_step == 0) {
                        error = EINVAL; /* Can only start a stopped process */
                        goto done;
                }
                if ((signo = *(int*)ap->a_data) != 0) {
                        if (signo >= NSIG || signo <= 0) {
                                error = EINVAL;
                                goto done;
                        }
                        ksignal(procp, signo);
                }
                procp->p_step = 0;
                wakeup(&procp->p_step);
                break;
        default:
                error = ENOTTY;
                goto done;
        }
        error = 0;
done:
        pfs_pdone(procp);
        return error;
}

/*
 * do block mapping for pfsnode (vp).
 * since we don't use the buffer cache
 * for procfs this function should never
 * be called.  in any case, it's not clear
 * what part of the kernel ever makes use
 * of this function.  for sanity, this is the
 * usual no-op bmap, although returning
 * (EIO) would be a reasonable alternative.
 *
 * XXX mmap assumes buffer cache operation
 *
 * procfs_bmap(struct vnode *a_vp, off_t a_loffset,
 *              off_t *a_doffsetp, int *a_runp, int *a_runb)
 */
static int
procfs_bmap(struct vop_bmap_args *ap)
{
        if (ap->a_doffsetp != NULL)
                *ap->a_doffsetp = ap->a_loffset;
        if (ap->a_runp != NULL)
                *ap->a_runp = 0;
        if (ap->a_runb != NULL)
                *ap->a_runb = 0;
        return (0);
}

/*
 * procfs_inactive is called when the pfsnode
 * is vrele'd and the reference count goes
 * to zero.  (vp) will be on the vnode free
 * list, so to get it back vget() must be
 * used.
 *
 * (vp) is locked on entry, but must be unlocked on exit.
 *
 * procfs_inactive(struct vnode *a_vp)
 */
static int
procfs_inactive(struct vop_inactive_args *ap)
{
        struct pfsnode *pfs = VTOPFS(ap->a_vp);

        if (pfs->pfs_pid & PFS_DEAD)
                vrecycle(ap->a_vp);
        return (0);
}

/*
 * _reclaim is called when getnewvnode()
 * wants to make use of an entry on the vnode
 * free list.  at this time the filesystem needs
 * to free any private data and remove the node
 * from any private lists.
 *
 * procfs_reclaim(struct vnode *a_vp)
 */
static int
procfs_reclaim(struct vop_reclaim_args *ap)
{
        return (procfs_freevp(ap->a_vp));
}

/*
 * _print is used for debugging.
 * just print a readable description
 * of (vp).
 *
 * procfs_print(struct vnode *a_vp)
 */
static int
procfs_print(struct vop_print_args *ap)
{
        struct pfsnode *pfs = VTOPFS(ap->a_vp);

        kprintf("tag VT_PROCFS, type %d, pid %ld, mode %x, flags %lx\n",
            pfs->pfs_type, (long)pfs->pfs_pid, pfs->pfs_mode, pfs->pfs_flags);
        return (0);
}

/*
 * generic entry point for unsupported operations
 */
static int
procfs_badop(struct vop_generic_args *ap)
{
        return (EIO);
}

/*
 * Invent attributes for pfsnode (vp) and store
 * them in (vap).
 * Directories lengths are returned as zero since
 * any real length would require the genuine size
 * to be computed, and nothing cares anyway.
 *
 * this is relatively minimal for procfs.
 *
 * procfs_getattr(struct vnode *a_vp, struct vattr *a_vap)
 */
static int
procfs_getattr(struct vop_getattr_args *ap)
{
        struct pfsnode *pfs = VTOPFS(ap->a_vp);
        struct vattr *vap = ap->a_vap;
        struct proc *procp;
        int error;

        /*
         * First make sure that the process and its credentials
         * still exist.
         */
        switch (pfs->pfs_type) {
        case Proot:
        case Pcurproc:
                procp = NULL;
                break;
        default:
                procp = pfs_pfind(pfs->pfs_pid);
                if (procp == NULL || procp->p_ucred == NULL) {
                        error = ENOENT;
                        goto done;
                }
                break;
        }

        error = 0;

        /* start by zeroing out the attributes */
        VATTR_NULL(vap);

        /* next do all the common fields */
        vap->va_type = ap->a_vp->v_type;
        vap->va_mode = pfs->pfs_mode;
        vap->va_fileid = pfs->pfs_fileno;
        vap->va_flags = 0;
        vap->va_blocksize = PAGE_SIZE;
        vap->va_bytes = vap->va_size = 0;
        vap->va_fsid = ap->a_vp->v_mount->mnt_stat.f_fsid.val[0];

        /*
         * Make all times be current TOD.
         * It would be possible to get the process start
         * time from the p_stat structure, but there's
         * no "file creation" time stamp anyway, and the
         * p_stat structure is not addressible if u. gets
         * swapped out for that process.
         */
        vfs_timestamp(&vap->va_ctime);
        vap->va_atime = vap->va_mtime = vap->va_ctime;

        /*
         * If the process has exercised some setuid or setgid
         * privilege, then rip away read/write permission so
         * that only root can gain access.
         */
        switch (pfs->pfs_type) {
        case Pctl:
        case Pregs:
        case Pfpregs:
        case Pdbregs:
        case Pmem:
                if (procp->p_flags & P_SUGID) {
                        vap->va_mode &= ~((VREAD|VWRITE)|
                                          ((VREAD|VWRITE)>>3)|
                                          ((VREAD|VWRITE)>>6));
                }
                break;
        default:
                break;
        }

        /*
         * now do the object specific fields
         *
         * The size could be set from struct reg, but it's hardly
         * worth the trouble, and it puts some (potentially) machine
         * dependent data into this machine-independent code.  If it
         * becomes important then this function should break out into
         * a per-file stat function in the corresponding .c file.
         */

        vap->va_nlink = 1;
        if (procp) {
                if (procp->p_ucred) {
                        vap->va_uid = procp->p_ucred->cr_uid;
                        vap->va_gid = procp->p_ucred->cr_gid;
                } else {
                        vap->va_uid = -1;
                        vap->va_gid = -1;
                }
        }

        switch (pfs->pfs_type) {
        case Proot:
                /*
                 * Set nlink to 1 to tell fts(3) we don't actually know.
                 */
                vap->va_nlink = 1;
                vap->va_uid = 0;
                vap->va_gid = 0;
                vap->va_size = vap->va_bytes = DEV_BSIZE;
                break;

        case Pcurproc: {
                char buf[16];           /* should be enough */

                vap->va_uid = 0;
                vap->va_gid = 0;
                vap->va_size = ksnprintf(buf, sizeof(buf),
                                         "%ld", (long)curproc->p_pid);
                vap->va_bytes = vap->va_size;
                break;
        }

        case Pproc:
                vap->va_nlink = nproc_targets;
                vap->va_size = vap->va_bytes = DEV_BSIZE;
                break;

        case Pfile: {
                char *fullpath, *freepath;

                if (procp->p_textnch.ncp) {
                        struct nchandle nch;

                        cache_copy(&procp->p_textnch, &nch);
                        error = cache_fullpath(procp, &nch, NULL,
                                               &fullpath, &freepath, 0);
                        cache_drop(&nch);
                } else {
                        error = EINVAL;
                }

                if (error == 0) {
                        vap->va_size = strlen(fullpath);
                        kfree(freepath, M_TEMP);
                } else {
                        vap->va_size = sizeof("unknown") - 1;
                        error = 0;
                }
                vap->va_bytes = vap->va_size;
                break;
        }

        case Pmem:
                /*
                 * If we denied owner access earlier, then we have to
                 * change the owner to root - otherwise 'ps' and friends
                 * will break even though they are setgid kmem. *SIGH*
                 */
                if (procp->p_flags & P_SUGID)
                        vap->va_uid = 0;
                else if (procp->p_ucred)
                        vap->va_uid = procp->p_ucred->cr_uid;
                else
                        vap->va_uid = -1;
                break;

        case Pregs:
                vap->va_bytes = vap->va_size = sizeof(struct reg);
                break;

        case Pfpregs:
                vap->va_bytes = vap->va_size = sizeof(struct fpreg);
                break;

        case Pdbregs:
                vap->va_bytes = vap->va_size = sizeof(struct dbreg);
                break;

        case Ptype:
        case Pmap:
        case Pctl:
        case Pstatus:
        case Pnote:
        case Pnotepg:
        case Pcmdline:
        case Prlimit:
                break;

        default:
                panic("procfs_getattr");
        }
done:
        pfs_pdone(procp);
        return (error);
}

/*
 * procfs_setattr(struct vnode *a_vp, struct vattr *a_vap,
 *                struct ucred *a_cred)
 */
static int
procfs_setattr(struct vop_setattr_args *ap)
{
        if (ap->a_vap->va_flags != VNOVAL)
                return (EOPNOTSUPP);

        /*
         * just fake out attribute setting
         * it's not good to generate an error
         * return, otherwise things like creat()
         * will fail when they try to set the
         * file length to 0.  worse, this means
         * that echo $note > /proc/$pid/note will fail.
         */

        return (0);
}

/*
 * implement access checking.
 *
 * procfs_access(struct vnode *a_vp, int a_mode, struct ucred *a_cred)
 */
static int
procfs_access(struct vop_access_args *ap)
{
        struct vattr vattr;
        int error;

        error = VOP_GETATTR(ap->a_vp, &vattr);
        if (!error)
                error = vop_helper_access(ap, vattr.va_uid, vattr.va_gid,
                                          vattr.va_mode, 0);
        return (error);
}

/*
 * lookup.  this is incredibly complicated in the general case, however
 * for most pseudo-filesystems very little needs to be done.
 *
 * procfs_lookup(struct vnode *a_dvp, struct vnode **a_vpp,
 *               struct componentname *a_cnp)
 */
static int
procfs_lookup(struct vop_old_lookup_args *ap)
{
        struct componentname *cnp = ap->a_cnp;
        struct vnode **vpp = ap->a_vpp;
        struct vnode *dvp = ap->a_dvp;
        char *pname = cnp->cn_nameptr;
        /* struct proc *curp = cnp->cn_proc; */
        struct proc_target *pt;
        pid_t pid;
        struct pfsnode *pfs;
        struct proc *p;
        struct lwp *lp;
        int i;
        int error;

        *vpp = NULL;

        if (cnp->cn_nameiop == NAMEI_DELETE || cnp->cn_nameiop == NAMEI_RENAME)
                return (EROFS);

        p = NULL;
        error = 0;
        if (cnp->cn_namelen == 1 && *pname == '.') {
                *vpp = dvp;
                vref(*vpp);
                goto out;
        }

        pfs = VTOPFS(dvp);
        switch (pfs->pfs_type) {
        case Proot:
                if (cnp->cn_flags & CNP_ISDOTDOT)
                        return (EIO);

                if (CNEQ(cnp, "curproc", 7) || CNEQ(cnp, "self", 4)) {
                        error = procfs_allocvp(dvp->v_mount, vpp, 0, Pcurproc);
                        goto out;
                }

                pid = atopid(pname, cnp->cn_namelen);
                if (pid == NO_PID)
                        break;

                p = pfs_pfind(pid);
                if (p == NULL)
                        break;

                if (!PRISON_CHECK(ap->a_cnp->cn_cred, p->p_ucred))
                        break;

                if (ps_showallprocs == 0 && ap->a_cnp->cn_cred->cr_uid != 0 &&
                    ap->a_cnp->cn_cred->cr_uid != p->p_ucred->cr_uid)
                        break;

                error = procfs_allocvp(dvp->v_mount, vpp, pid, Pproc);
                goto out;

        case Pproc:
                if (cnp->cn_flags & CNP_ISDOTDOT) {
                        error = procfs_root(dvp->v_mount, vpp);
                        goto out;
                }

                p = pfs_pfind(pfs->pfs_pid);
                if (p == NULL)
                        break;
                /* XXX lwp */
                lp = FIRST_LWP_IN_PROC(p);
                if (lp == NULL)
                        break;

                if (!PRISON_CHECK(ap->a_cnp->cn_cred, p->p_ucred))
                        break;

                if (ps_showallprocs == 0 && ap->a_cnp->cn_cred->cr_uid != 0 &&
                    ap->a_cnp->cn_cred->cr_uid != p->p_ucred->cr_uid)
                        break;

                for (pt = proc_targets, i = 0; i < nproc_targets; pt++, i++) {
                        if (cnp->cn_namelen == pt->pt_namlen &&
                            bcmp(pt->pt_name, pname, cnp->cn_namelen) == 0 &&
                            (pt->pt_valid == NULL || (*pt->pt_valid)(lp)))
                                goto found;
                }
                break;
        found:
                error = procfs_allocvp(dvp->v_mount, vpp, pfs->pfs_pid,
                                       pt->pt_pfstype);
                goto out;

        default:
                error = ENOTDIR;
                goto out;
        }
        if (cnp->cn_nameiop == NAMEI_LOOKUP)
                error = ENOENT;
        else
                error = EROFS;
        /*
         * If no error occured *vpp will hold a referenced locked vnode.
         * dvp was passed to us locked and *vpp must be returned locked.
         * If *vpp != dvp then we should unlock dvp if (1) this is not the
         * last component or (2) CNP_LOCKPARENT is not set.
         */
out:
        if (error == 0 && *vpp != dvp) {
                if ((cnp->cn_flags & CNP_LOCKPARENT) == 0) {
                        cnp->cn_flags |= CNP_PDIRUNLOCK;
                        vn_unlock(dvp);
                }
        }
        pfs_pdone(p);
        return (error);
}

/*
 * Does this process have a text file?
 */
int
procfs_validfile(struct lwp *lp)
{
        return (procfs_findtextvp(lp->lwp_proc) != NULLVP);
}

/*
 * readdir() returns directory entries from pfsnode (vp).
 *
 * We generate just one directory entry at a time, as it would probably
 * not pay off to buffer several entries locally to save uiomove calls.
 *
 * procfs_readdir(struct vnode *a_vp, struct uio *a_uio, struct ucred *a_cred,
 *                int *a_eofflag, int *a_ncookies, off_t **a_cookies)
 */
static int
procfs_readdir(struct vop_readdir_args *ap)
{
        struct pfsnode *pfs;
        int error;

        if (ap->a_uio->uio_offset < 0 || ap->a_uio->uio_offset > INT_MAX)
                return (EINVAL);
        error = vn_lock(ap->a_vp, LK_EXCLUSIVE | LK_RETRY | LK_FAILRECLAIM);
        if (error)
                return (error);

        pfs = VTOPFS(ap->a_vp);
        switch (pfs->pfs_type) {
        case Pproc:
                /*
                 * this is for the process-specific sub-directories.
                 * all that is needed to is copy out all the entries
                 * from the procent[] table (top of this file).
                 */
                error = procfs_readdir_proc(ap);
                break;
        case Proot:
                /*
                 * this is for the root of the procfs filesystem
                 * what is needed is a special entry for "curproc"
                 * followed by an entry for each process on allproc
                 */
                error = procfs_readdir_root(ap);
                break;
        default:
                error = ENOTDIR;
                break;
        }

        vn_unlock(ap->a_vp);
        return (error);
}

static int
procfs_readdir_proc(struct vop_readdir_args *ap)
{
        struct pfsnode *pfs;
        int error, i, retval;
        struct proc *p;
        struct lwp *lp;
        struct proc_target *pt;
        struct uio *uio = ap->a_uio;

        pfs = VTOPFS(ap->a_vp);
        p = pfs_pfind(pfs->pfs_pid);
        if (p == NULL)
                return(0);
        if (!PRISON_CHECK(ap->a_cred, p->p_ucred)) {
                error = 0;
                goto done;
        }
        /* XXX lwp, not MPSAFE */
        lp = FIRST_LWP_IN_PROC(p);
        if (lp == NULL) {
                error = EINVAL;
                goto done;
        }

        error = 0;
        i = (int)uio->uio_offset;
        if (i < 0) {
                error = EINVAL;
                goto done;
        }

        for (pt = &proc_targets[i];
             !error && uio->uio_resid > 0 && i < nproc_targets; pt++, i++) {
                if (pt->pt_valid && (*pt->pt_valid)(lp) == 0)
                        continue;

                retval = vop_write_dirent(&error, uio,
                    PROCFS_FILENO(pfs->pfs_pid, pt->pt_pfstype), pt->pt_type,
                    pt->pt_namlen, pt->pt_name);
                if (retval)
                        break;
        }

        uio->uio_offset = (off_t)i;
        error = 0;
done:
        pfs_pdone(p);
        return error;
}

struct procfs_readdir_root_info {
        int error;
        int i;
        int pcnt;
        struct uio *uio;
        struct ucred *cred;
};

static int procfs_readdir_root_callback(struct proc *p, void *data);

static int
procfs_readdir_root(struct vop_readdir_args *ap)
{
        struct procfs_readdir_root_info info;
        struct uio *uio = ap->a_uio;
        int res;

        res = 0;
        info.error = 0;
        info.i = (int)uio->uio_offset;

        if (info.i < 0)
                return (EINVAL);

        info.pcnt = 0;
        info.uio = uio;
        info.cred = ap->a_cred;
        while (info.pcnt < 4) {
                res = procfs_readdir_root_callback(NULL, &info);
                if (res < 0)
                        break;
        }
        if (res >= 0)
                allproc_scan(procfs_readdir_root_callback, &info, 0);
        uio->uio_offset = (off_t)info.i;

        return (info.error);
}

static int
procfs_readdir_root_callback(struct proc *p, void *data)
{
        struct procfs_readdir_root_info *info = data;
        struct uio *uio;
        int retval;
        ino_t d_ino;
        const char *d_name;
        char d_name_pid[20];
        size_t d_namlen;
        uint8_t d_type;

        uio = info->uio;

        if (uio->uio_resid <= 0 || info->error)
                return(-1);

        switch (info->pcnt) {
        case 0:         /* `.' */
                d_ino = PROCFS_FILENO(0, Proot);
                d_name = ".";
                d_namlen = 1;
                d_type = DT_DIR;
                break;
        case 1:         /* `..' */
                d_ino = PROCFS_FILENO(0, Proot);
                d_name = "..";
                d_namlen = 2;
                d_type = DT_DIR;
                break;

        case 2:
                d_ino = PROCFS_FILENO(0, Pcurproc);
                d_namlen = 7;
                d_name = "curproc";
                d_type = DT_LNK;
                break;

        case 3:
                d_ino = PROCFS_FILENO(0, Pcurproc);
                d_namlen = 4;
                d_name = "self";
                d_type = DT_LNK;
                break;

        default:
                if (!PRISON_CHECK(info->cred, p->p_ucred))
                        return(0);
                if (ps_showallprocs == 0 &&
                    info->cred->cr_uid != 0 &&
                    info->cred->cr_uid != p->p_ucred->cr_uid) {
                        return(0);
                }

                /*
                 * Skip entries we have already returned (optimization)
                 */
                if (info->pcnt < info->i) {
                        ++info->pcnt;
                        return(0);
                }

                d_ino = PROCFS_FILENO(p->p_pid, Pproc);
                d_namlen = ksnprintf(d_name_pid, sizeof(d_name_pid),
                                     "%ld", (long)p->p_pid);
                d_name = d_name_pid;
                d_type = DT_DIR;
                break;
        }

        /*
         * Skip entries we have already returned (optimization)
         */
        if (info->pcnt < info->i) {
                ++info->pcnt;
                return(0);
        }

        retval = vop_write_dirent(&info->error, uio,
                                  d_ino, d_type, d_namlen, d_name);
        if (retval)
                return(-1);
        ++info->pcnt;
        ++info->i;
        return(0);
}

/*
 * readlink reads the link of `curproc' or `file'
 */
static int
procfs_readlink(struct vop_readlink_args *ap)
{
        char buf[16];           /* should be enough */
        struct proc *procp;
        struct vnode *vp = ap->a_vp;
        struct pfsnode *pfs = VTOPFS(vp);
        char *fullpath, *freepath;
        int error, len;

        switch (pfs->pfs_type) {
        case Pcurproc:
                if (pfs->pfs_fileno != PROCFS_FILENO(0, Pcurproc))
                        return (EINVAL);

                len = ksnprintf(buf, sizeof(buf), "%ld", (long)curproc->p_pid);
                return (uiomove(buf, len, ap->a_uio));
        case Pfile:
                /*
                 * procfs's directory topology is somewhat asynchronous from
                 * reality so it is possible for pid requests to race exiting
                 * processes.  In this situation, bit 31 is set in
                 * pfs->pfs_pid which guarantees that pfs_pfind() will return
                 * NULL.
                 *
                 * It is also possible to catch a process in the middle of
                 * an exit sequence so various fields might wind up being
                 * NULL that are not normally NULL.
                 */
                procp = pfs_pfind(pfs->pfs_pid);
                if (procp == NULL || procp->p_ucred == NULL) {
                        pfs_pdone(procp);
                        return (uiomove("unknown", sizeof("unknown") - 1,
                                        ap->a_uio));
                }
                if (procp->p_textnch.ncp) {
                        struct nchandle nch;

                        cache_copy(&procp->p_textnch, &nch);
                        error = cache_fullpath(procp, &nch, NULL,
                                               &fullpath, &freepath, 0);
                        cache_drop(&nch);
                } else {
                        error = EINVAL;
                }

                if (error != 0) {
                        pfs_pdone(procp);
                        return (uiomove("unknown", sizeof("unknown") - 1,
                                        ap->a_uio));
                }
                error = uiomove(fullpath, strlen(fullpath), ap->a_uio);
                kfree(freepath, M_TEMP);
                pfs_pdone(procp);
                return (error);
        default:
                return (EINVAL);
        }
}

/*
 * convert decimal ascii to pid_t
 */
static pid_t
atopid(const char *b, u_int len)
{
        pid_t p = 0;

        while (len--) {
                char c = *b++;
                if (c < '0' || c > '9')
                        return (NO_PID);
                p = 10 * p + (c - '0');
                if (p > PID_MAX)
                        return (NO_PID);
        }

        return (p);
}

/*
 * kqfilter operations
 */
static void
procfs_filt_detach(struct knote *kn)
{
        struct vnode *vp = (void *)kn->kn_hook;

        knote_remove(&vp->v_pollinfo.vpi_kqinfo.ki_note, kn);
}

static int
procfs_filt_read(struct knote *kn, long hint)
{
        if (hint == NOTE_REVOKE) {
                kn->kn_flags |= (EV_EOF | EV_NODATA | EV_ONESHOT);
                return (1);
        }

        /* Files on procfs have a size of 0. */
        kn->kn_data = 0;
        if (kn->kn_sfflags & NOTE_OLDAPI)
                return (1);
        return (kn->kn_data != 0);
}

static int
procfs_filt_write(struct knote *kn, long hint)
{
        if (hint == NOTE_REVOKE)
                kn->kn_flags |= (EV_EOF | EV_NODATA | EV_ONESHOT);
        kn->kn_data = 0;
        return (1);
}

static int
procfs_filt_vnode(struct knote *kn, long hint)
{
        if (kn->kn_sfflags & hint)
                kn->kn_fflags |= hint;
        if (hint == NOTE_REVOKE) {
                kn->kn_flags |= (EV_EOF | EV_NODATA);
                return (1);
        }
        return (kn->kn_fflags != 0);
}

static struct filterops procfs_read_filtops = {
        FILTEROP_ISFD | FILTEROP_MPSAFE, NULL,
        procfs_filt_detach, procfs_filt_read,
};
static struct filterops procfs_write_filtops = {
        FILTEROP_ISFD | FILTEROP_MPSAFE, NULL,
        procfs_filt_detach, procfs_filt_write,
};
static struct filterops procfs_vnode_filtops = {
        FILTEROP_ISFD | FILTEROP_MPSAFE, NULL,
        procfs_filt_detach, procfs_filt_vnode,
};

static int
procfs_kqfilter(struct vop_kqfilter_args *ap)
{
        struct vnode *vp = ap->a_vp;
        struct knote *kn = ap->a_kn;

        switch (kn->kn_filter) {
        case EVFILT_READ:
                kn->kn_fop = &procfs_read_filtops;
                break;
        case EVFILT_WRITE:
                kn->kn_fop = &procfs_write_filtops;
                break;
        case EVFILT_VNODE:
                kn->kn_fop = &procfs_vnode_filtops;
                break;
        default:
                return (EOPNOTSUPP);
        }

        kn->kn_hook = (caddr_t)vp;
        knote_insert(&vp->v_pollinfo.vpi_kqinfo.ki_note, kn);

        return (0);
}