/*
 * Copyright (c) 1993 Jan-Simon Pendry
 * Copyright (c) 1993
 *      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_subr.c       8.6 (Berkeley) 5/14/95
 *
 * $FreeBSD: src/sys/miscfs/procfs/procfs_subr.c,v 1.26.2.3 2002/02/18 21:28:04 des Exp $
 */

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/sysctl.h>
#include <sys/uio.h>
#include <sys/proc.h>
#include <sys/mount.h>
#include <sys/vnode.h>
#include <sys/malloc.h>
#include <sys/spinlock.h>

#include <sys/spinlock2.h>

#include <vfs/procfs/procfs.h>

#define PFS_HSIZE       1031

struct pfshead {
        struct spinlock spin;
        struct pfsnode  *first;
} __cachealign;

static struct pfshead   pfshead[PFS_HSIZE];
static struct lock      procfslk = LOCK_INITIALIZER("pvplk", 0, 0);

MALLOC_DEFINE(M_PROCFS, "procfs", "procfs v_data");

#define PFSHASH(pid)    &pfshead[((pid) & ~PFS_DEAD) % PFS_HSIZE]

/*
 * Allocate a pfsnode/vnode pair.  If no error occurs the returned vnode
 * will be referenced and exclusively locked.
 *
 * The pid, pfs_type, and mount point uniquely identify a pfsnode.
 * The mount point is needed because someone might mount this filesystem
 * twice.
 *
 * All pfsnodes are maintained on a singly-linked list.  new nodes are
 * only allocated when they cannot be found on this list.  entries on
 * the list are removed when the vfs reclaim entry is called.
 *
 * A single lock is kept for the entire list.  this is needed because the
 * getnewvnode() function can block waiting for a vnode to become free,
 * in which case there may be more than one process trying to get the same
 * vnode.  this lock is only taken if we are going to call getnewvnode,
 * since the kernel itself is single-threaded.
 *
 * If an entry is found on the list, then call vget() to take a reference
 * and obtain the lock.  This will properly re-reference the vnode if it
 * had gotten onto the free list.
 */
int
procfs_allocvp(struct mount *mp, struct vnode **vpp, long pid, pfstype pfs_type)
{
        struct pfsnode *pfs;
        struct vnode *vp;
        struct pfshead *ph;
        int error;

        ph = PFSHASH(pid);
loop:
        spin_lock(&ph->spin);
        for (pfs = ph->first; pfs; pfs = pfs->pfs_next) {
                if (pfs->pfs_pid == pid && pfs->pfs_type == pfs_type &&
                    PFSTOV(pfs)->v_mount == mp) {
                        vp = PFSTOV(pfs);
                        vhold(vp);
                        spin_unlock(&ph->spin);
                        if (vget(vp, LK_EXCLUSIVE)) {
                                vdrop(vp);
                                goto loop;
                        }
                        vdrop(vp);

                        /*
                         * Make sure the vnode is still in the cache after
                         * getting the interlock to avoid racing a free.
                         */
                        spin_lock(&ph->spin);
                        for (pfs = ph->first; pfs; pfs = pfs->pfs_next) {
                                if (PFSTOV(pfs) == vp &&
                                    pfs->pfs_pid == pid &&
                                    pfs->pfs_type == pfs_type &&
                                    PFSTOV(pfs)->v_mount == mp) {
                                        break;
                                }
                        }
                        if (pfs == NULL || PFSTOV(pfs) != vp) {
                                spin_unlock(&ph->spin);
                                vput(vp);
                                goto loop;

                        }
                        spin_unlock(&ph->spin);
                        *vpp = vp;
                        return (0);
                }
        }
        spin_unlock(&ph->spin);

        /*
         * otherwise lock the vp list while we call getnewvnode
         * since that can block.
         */
        if (lockmgr(&procfslk, LK_EXCLUSIVE|LK_SLEEPFAIL))
                goto loop;

        /*
         * Do the MALLOC before the getnewvnode since doing so afterward
         * might cause a bogus v_data pointer to get dereferenced
         * elsewhere if MALLOC should block.
         *
         * XXX this may not matter anymore since getnewvnode now returns
         * a VX locked vnode.
         */
        pfs = kmalloc(sizeof(struct pfsnode), M_PROCFS, M_WAITOK);

        error = getnewvnode(VT_PROCFS, mp, vpp, 0, 0);
        if (error) {
                kfree(pfs, M_PROCFS);
                goto out;
        }
        vp = *vpp;

        vp->v_data = pfs;

        pfs->pfs_next = 0;
        pfs->pfs_pid = (pid_t) pid;
        pfs->pfs_type = pfs_type;
        pfs->pfs_vnode = vp;
        pfs->pfs_flags = 0;
        pfs->pfs_fileno = PROCFS_FILENO(pid, pfs_type);
        lockinit(&pfs->pfs_lock, "pfslk", 0, 0);

        switch (pfs_type) {
        case Proot:     /* /proc = dr-xr-xr-x */
                pfs->pfs_mode = (VREAD|VEXEC) |
                                (VREAD|VEXEC) >> 3 |
                                (VREAD|VEXEC) >> 6;
                vp->v_type = VDIR;
                vp->v_flag = VROOT;
                break;

        case Pcurproc:  /* /proc/curproc = lr--r--r-- */
                pfs->pfs_mode = (VREAD) |
                                (VREAD >> 3) |
                                (VREAD >> 6);
                vp->v_type = VLNK;
                break;

        case Pproc:
                pfs->pfs_mode = (VREAD|VEXEC) |
                                (VREAD|VEXEC) >> 3 |
                                (VREAD|VEXEC) >> 6;
                vp->v_type = VDIR;
                break;

        case Pfile:
                pfs->pfs_mode = (VREAD|VEXEC) |
                                (VREAD|VEXEC) >> 3 |
                                (VREAD|VEXEC) >> 6;
                vp->v_type = VLNK;
                break;

        case Pmem:
                pfs->pfs_mode = (VREAD|VWRITE);
                vp->v_type = VREG;
                break;

        case Pregs:
        case Pfpregs:
        case Pdbregs:
                pfs->pfs_mode = (VREAD|VWRITE);
                vp->v_type = VREG;
                break;

        case Pctl:
        case Pnote:
        case Pnotepg:
                pfs->pfs_mode = (VWRITE);
                vp->v_type = VREG;
                break;

        case Ptype:
        case Pmap:
        case Pstatus:
        case Pcmdline:
        case Prlimit:
                pfs->pfs_mode = (VREAD) |
                                (VREAD >> 3) |
                                (VREAD >> 6);
                vp->v_type = VREG;
                break;

        default:
                panic("procfs_allocvp");
        }

        /* add to procfs vnode list */
        spin_lock(&ph->spin);
        pfs->pfs_next = ph->first;
        ph->first = pfs;
        spin_unlock(&ph->spin);
        vx_downgrade(vp);

out:
        lockmgr(&procfslk, LK_RELEASE);

        return (error);
}

int
procfs_freevp(struct vnode *vp)
{
        struct pfshead *ph;
        struct pfsnode **pp;
        struct pfsnode *pfs;

        pfs = VTOPFS(vp);
        vp->v_data = NULL;
        ph = PFSHASH(pfs->pfs_pid);

        spin_lock(&ph->spin);
        pp = &ph->first;
        while (*pp != pfs) {
                KKASSERT(*pp != NULL);
                pp = &(*pp)->pfs_next;
        }
        *pp = pfs->pfs_next;
        spin_unlock(&ph->spin);

        pfs->pfs_next = NULL;
        pfs->pfs_vnode = NULL;
        kfree(pfs, M_PROCFS);

        return (0);
}

/*
 * Try to find the calling pid. Note that pfind()
 * now references the proc structure to be returned
 * and needs to be released later with PRELE().
 */
struct proc *
pfs_pfind(pid_t pfs_pid)
{
        struct proc *p = NULL;

        if (pfs_pid == 0) {
                p = &proc0;
                PHOLD(p);
        } else {
                p = pfind(pfs_pid);
        }

        /*
         * Make sure the process is not in the middle of exiting (where
         * a lot of its structural members may wind up being NULL).  If it
         * is we give up on it.
         */
        if (p) {
                lwkt_gettoken(&p->p_token);
                if (p->p_flags & P_POSTEXIT) {
                        lwkt_reltoken(&p->p_token);
                        PRELE(p);
                        p = NULL;
                }
        }
        return p;
}

struct proc *
pfs_zpfind(pid_t pfs_pid)
{
        struct proc *p = NULL;

        if (pfs_pid == 0) {
                p = &proc0;
                PHOLD(p);
        } else {
                p = zpfind(pfs_pid);
        }

        /*
         * Make sure the process is not in the middle of exiting (where
         * a lot of its structural members may wind up being NULL).  If it
         * is we give up on it.
         */
        if (p) {
                lwkt_gettoken(&p->p_token);
                if (p->p_flags & P_POSTEXIT) {
                        lwkt_reltoken(&p->p_token);
                        PRELE(p);
                        p = NULL;
                }
        }
        return p;
}

void
pfs_pdone(struct proc *p)
{
        if (p) {
                lwkt_reltoken(&p->p_token);
                PRELE(p);
        }
}

int
procfs_rw(struct vop_read_args *ap)
{
        struct vnode *vp = ap->a_vp;
        struct uio *uio = ap->a_uio;
        struct thread *curtd = uio->uio_td;
        struct proc *curp;
        struct pfsnode *pfs = VTOPFS(vp);
        struct proc *p;
        struct lwp *lp;
        int rtval;

        if (curtd == NULL)
                return (EINVAL);
        if ((curp = curtd->td_proc) == NULL)    /* XXX */
                return (EINVAL);

        p = pfs_pfind(pfs->pfs_pid);
        if (p == NULL) {
                rtval = EINVAL;
                goto out;
        }
        if (p->p_pid == 1 && securelevel > 0 && uio->uio_rw == UIO_WRITE) {
                rtval = EACCES;
                goto out;
        }

        /*
         * XXX lwp
         */
        lp = FIRST_LWP_IN_PROC(p);
        if (lp == NULL) {
                rtval = EINVAL;
                goto out;
        }
        LWPHOLD(lp);

        lockmgr(&pfs->pfs_lock, LK_EXCLUSIVE);

        switch (pfs->pfs_type) {
        case Pnote:
        case Pnotepg:
                rtval = procfs_donote(curp, lp, pfs, uio);
                break;

        case Pregs:
                rtval = procfs_doregs(curp, lp, pfs, uio);
                break;

        case Pfpregs:
                rtval = procfs_dofpregs(curp, lp, pfs, uio);
                break;

        case Pdbregs:
                rtval = procfs_dodbregs(curp, lp, pfs, uio);
                break;

        case Pctl:
                rtval = procfs_doctl(curp, lp, pfs, uio);
                break;

        case Pstatus:
                rtval = procfs_dostatus(curp, lp, pfs, uio);
                break;

        case Pmap:
                rtval = procfs_domap(curp, lp, pfs, uio);
                break;

        case Pmem:
                rtval = procfs_domem(curp, lp, pfs, uio);
                break;

        case Ptype:
                rtval = procfs_dotype(curp, lp, pfs, uio);
                break;

        case Pcmdline:
                rtval = procfs_docmdline(curp, lp, pfs, uio);
                break;

        case Prlimit:
                rtval = procfs_dorlimit(curp, lp, pfs, uio);
                break;

        default:
                rtval = EOPNOTSUPP;
                break;
        }
        LWPRELE(lp);

        lockmgr(&pfs->pfs_lock, LK_RELEASE);

        if (uio->uio_rw == UIO_WRITE && rtval == 0)
                KNOTE(&PFSTOV(pfs)->v_pollinfo.vpi_kqinfo.ki_note, NOTE_WRITE);

out:
        pfs_pdone(p);

        return rtval;
}

/*
 * Get a string from userland into (buf).  Strip a trailing
 * nl character (to allow easy access from the shell).
 * The buffer should be *buflenp + 1 chars long.  vfs_getuserstr
 * will automatically add a nul char at the end.
 *
 * Returns 0 on success or the following errors
 *
 * EINVAL:    file offset is non-zero.
 * EMSGSIZE:  message is longer than kernel buffer
 * EFAULT:    user i/o buffer is not addressable
 */
int
vfs_getuserstr(struct uio *uio, char *buf, int *buflenp)
{
        int xlen;
        int error;

        if (uio->uio_offset != 0)
                return (EINVAL);

        xlen = *buflenp;

        /* must be able to read the whole string in one go */
        if (xlen < uio->uio_resid)
                return (EMSGSIZE);
        xlen = uio->uio_resid;

        if ((error = uiomove(buf, xlen, uio)) != 0)
                return (error);

        /* allow multiple writes without seeks */
        uio->uio_offset = 0;

        /* cleanup string and remove trailing newline */
        buf[xlen] = '\0';
        xlen = strlen(buf);
        if (xlen > 0 && buf[xlen-1] == '\n')
                buf[--xlen] = '\0';
        *buflenp = xlen;

        return (0);
}

vfs_namemap_t *
vfs_findname(vfs_namemap_t *nm, char *buf, int buflen)
{

        for (; nm->nm_name; nm++)
                if (bcmp(buf, nm->nm_name, buflen+1) == 0)
                        return (nm);

        return (0);
}

void
procfs_exit(struct thread *td)
{
        struct pfshead *ph;
        struct pfsnode *pfs;
        struct vnode *vp;
        pid_t pid;

        KKASSERT(td->td_proc);
        pid = td->td_proc->p_pid;

        /*
         * NOTE: We can't just vgone() the vnode any more, not while
         *       it may potentially still be active.  This will clean
         *       the vp and clear the mount and cause the new VOP subsystem
         *       to assert or panic when someone tries to do an operation
         *       on an open (exited) procfs descriptor.
         *
         * Prevent further operations on this pid by setting pfs_pid to -1.
         * Note that a pfs_pid of 0 is used for nodes which do not track
         * any particular pid.
         *
         * Use vx_get() to properly ref/lock a vp which may not have any
         * refs and which may or may not already be reclaimed.  vx_put()
         * will then properly deactivate it and cause it to be recycled.
         *
         * The hash table can also get ripped out from under us when
         * we block so take the easy way out and restart the scan.
         */
        for (;;) {
                ph = PFSHASH(pid);
                spin_lock(&ph->spin);
                for (pfs = ph->first; pfs; pfs = pfs->pfs_next) {
                        if (pfs->pfs_pid == pid)
                                break;
                }
                if (pfs == NULL) {
                        spin_unlock(&ph->spin);
                        break;
                }
                vp = PFSTOV(pfs);
                vhold(vp);
                spin_unlock(&ph->spin);
                vx_get(vp);
                pfs->pfs_pid |= PFS_DEAD; /* does not effect hash */
                vx_put(vp);
                vdrop(vp);
        }
}