/*      $NetBSD: putter.c,v 1.39 2021/09/26 01:16:09 thorpej Exp $      */

/*
* Copyright (c) 2006, 2007  Antti Kantee.  All Rights Reserved.
*
* Development of this software was supported by the
* Ulla Tuominen Foundation and the Finnish Cultural Foundation and the
* Research Foundation of Helsinki University of Technology
*
* 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.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 AUTHOR 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.
*/

/*
* Pass-to-Userspace TransporTER: generic kernel-user request-response
* transport interface.
*/

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: putter.c,v 1.39 2021/09/26 01:16:09 thorpej Exp $");

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/conf.h>
#include <sys/file.h>
#include <sys/filedesc.h>
#include <sys/kmem.h>
#include <sys/poll.h>
#include <sys/stat.h>
#include <sys/socketvar.h>
#include <sys/module.h>
#include <sys/kauth.h>

#include <dev/putter/putter_sys.h>

/*
* Device routines.  These are for when /dev/putter is initially
* opened before it has been cloned.
*/

dev_type_open(puttercdopen);
dev_type_close(puttercdclose);
dev_type_ioctl(puttercdioctl);

/* dev */
const struct cdevsw putter_cdevsw = {
       .d_open = puttercdopen,
       .d_close = puttercdclose,
       .d_read = noread,
       .d_write = nowrite,
       .d_ioctl = noioctl,
       .d_stop = nostop,
       .d_tty = notty,
       .d_poll = nopoll,
       .d_mmap = nommap,
       .d_kqfilter = nokqfilter,
       .d_discard = nodiscard,
       .d_flag = D_OTHER
};

/*
* Configuration data.
*
* This is static-size for now.  Will be redone for devfs.
*/

#define PUTTER_CONFSIZE 16

static struct putter_config {
       int     pc_minor;
       int     (*pc_config)(int, int, int);
} putterconf[PUTTER_CONFSIZE];

static int
putter_configure(dev_t dev, int flags, int fmt, int fd)
{
       struct putter_config *pc;

       /* are we the catch-all node? */
       if (minor(dev) == PUTTER_MINOR_WILDCARD
           || minor(dev) == PUTTER_MINOR_COMPAT)
               return 0;

       /* nopes?  try to configure us */
       for (pc = putterconf; pc->pc_config; pc++)
               if (minor(dev) == pc->pc_minor)
                       return pc->pc_config(fd, flags, fmt);
       return ENXIO;
}

int
putter_register(putter_config_fn pcfn, int minor)
{
       int i;

       for (i = 0; i < PUTTER_CONFSIZE; i++)
               if (putterconf[i].pc_config == NULL)
                       break;
       if (i == PUTTER_CONFSIZE)
               return EBUSY;

       putterconf[i].pc_minor = minor;
       putterconf[i].pc_config = pcfn;
       return 0;
}

/*
* putter instance structures.  these are always allocated and freed
* from the context of the transport user.
*/
struct putter_instance {
       pid_t                   pi_pid;
       int                     pi_idx;
       int                     pi_fd;
       struct selinfo          pi_sel;

       void                    *pi_private;
       struct putter_ops       *pi_pop;

       uint8_t                 *pi_curput;
       size_t                  pi_curres;
       void                    *pi_curopaq;
       struct timespec         pi_atime;
       struct timespec         pi_mtime;
       struct timespec         pi_btime;

       TAILQ_ENTRY(putter_instance) pi_entries;
};
#define PUTTER_EMBRYO ((void *)-1)      /* before attach        */
#define PUTTER_DEAD ((void *)-2)        /* after detach         */

static TAILQ_HEAD(, putter_instance) putter_ilist
   = TAILQ_HEAD_INITIALIZER(putter_ilist);

static int get_pi_idx(struct putter_instance *);

#ifdef DEBUG
#ifndef PUTTERDEBUG
#define PUTTERDEBUG
#endif
#endif

#ifdef PUTTERDEBUG
int putterdebug = 0;
#define DPRINTF(x) if (putterdebug > 0) printf x
#define DPRINTF_VERBOSE(x) if (putterdebug > 1) printf x
#else
#define DPRINTF(x)
#define DPRINTF_VERBOSE(x)
#endif

/*
* public init / deinit
*/

/* protects both the list and the contents of the list elements */
static kmutex_t pi_mtx;

void putterattach(void);

void
putterattach(void)
{

       mutex_init(&pi_mtx, MUTEX_DEFAULT, IPL_NONE);
}

#if 0
void
putter_destroy(void)
{

       mutex_destroy(&pi_mtx);
}
#endif

/*
* fd routines, for cloner
*/
static int putter_fop_read(file_t *, off_t *, struct uio *,
                          kauth_cred_t, int);
static int putter_fop_write(file_t *, off_t *, struct uio *,
                           kauth_cred_t, int);
static int putter_fop_ioctl(file_t*, u_long, void *);
static int putter_fop_poll(file_t *, int);
static int putter_fop_stat(file_t *, struct stat *);
static int putter_fop_close(file_t *);
static int putter_fop_kqfilter(file_t *, struct knote *);


static const struct fileops putter_fileops = {
       .fo_name = "putter",
       .fo_read = putter_fop_read,
       .fo_write = putter_fop_write,
       .fo_ioctl = putter_fop_ioctl,
       .fo_fcntl = fnullop_fcntl,
       .fo_poll = putter_fop_poll,
       .fo_stat = putter_fop_stat,
       .fo_close = putter_fop_close,
       .fo_kqfilter = putter_fop_kqfilter,
       .fo_restart = fnullop_restart,
};

static int
putter_fop_read(file_t *fp, off_t *off, struct uio *uio,
       kauth_cred_t cred, int flags)
{
       struct putter_instance *pi = fp->f_data;
       size_t origres, moved;
       int error;

       KERNEL_LOCK(1, NULL);
       getnanotime(&pi->pi_atime);

       if (pi->pi_private == PUTTER_EMBRYO || pi->pi_private == PUTTER_DEAD) {
               printf("putter_fop_read: private %d not inited\n", pi->pi_idx);
               KERNEL_UNLOCK_ONE(NULL);
               return ENOENT;
       }

       if (pi->pi_curput == NULL) {
               error = pi->pi_pop->pop_getout(pi->pi_private, uio->uio_resid,
                   fp->f_flag & O_NONBLOCK, &pi->pi_curput,
                   &pi->pi_curres, &pi->pi_curopaq);
               if (error) {
                       KERNEL_UNLOCK_ONE(NULL);
                       return error;
               }
       }

       origres = uio->uio_resid;
       error = uiomove(pi->pi_curput, pi->pi_curres, uio);
       moved = origres - uio->uio_resid;
       DPRINTF(("putter_fop_read (%p): moved %zu bytes from %p, error %d\n",
           pi, moved, pi->pi_curput, error));

       KASSERT(pi->pi_curres >= moved);
       pi->pi_curres -= moved;
       pi->pi_curput += moved;

       if (pi->pi_curres == 0) {
               pi->pi_pop->pop_releaseout(pi->pi_private,
                   pi->pi_curopaq, error);
               pi->pi_curput = NULL;
       }

       KERNEL_UNLOCK_ONE(NULL);
       return error;
}

static int
putter_fop_write(file_t *fp, off_t *off, struct uio *uio,
       kauth_cred_t cred, int flags)
{
       struct putter_instance *pi = fp->f_data;
       struct putter_hdr pth;
       uint8_t *buf;
       size_t frsize;
       int error;

       KERNEL_LOCK(1, NULL);
       getnanotime(&pi->pi_mtime);

       DPRINTF(("putter_fop_write (%p): writing response, resid %zu\n",
           pi->pi_private, uio->uio_resid));

       if (pi->pi_private == PUTTER_EMBRYO || pi->pi_private == PUTTER_DEAD) {
               printf("putter_fop_write: putter %d not inited\n", pi->pi_idx);
               KERNEL_UNLOCK_ONE(NULL);
               return ENOENT;
       }

       error = uiomove(&pth, sizeof(struct putter_hdr), uio);
       if (error) {
               KERNEL_UNLOCK_ONE(NULL);
               return error;
       }

       /* Sorry mate, the kernel doesn't buffer. */
       frsize = pth.pth_framelen - sizeof(struct putter_hdr);
       if (uio->uio_resid < frsize) {
               KERNEL_UNLOCK_ONE(NULL);
               return EINVAL;
       }

       buf = kmem_alloc(frsize + sizeof(struct putter_hdr), KM_SLEEP);
       memcpy(buf, &pth, sizeof(pth));
       error = uiomove(buf+sizeof(struct putter_hdr), frsize, uio);
       if (error == 0) {
               pi->pi_pop->pop_dispatch(pi->pi_private,
                   (struct putter_hdr *)buf);
       }
       kmem_free(buf, frsize + sizeof(struct putter_hdr));

       KERNEL_UNLOCK_ONE(NULL);
       return error;
}

/*
* Poll query interface.  The question is only if an event
* can be read from us.
*/
#define PUTTERPOLL_EVSET (POLLIN | POLLRDNORM | POLLRDBAND | POLLPRI)
static int
putter_fop_poll(file_t *fp, int events)
{
       struct putter_instance *pi = fp->f_data;
       int revents;

       KERNEL_LOCK(1, NULL);

       if (pi->pi_private == PUTTER_EMBRYO || pi->pi_private == PUTTER_DEAD) {
               printf("putter_fop_ioctl: putter %d not inited\n", pi->pi_idx);
               KERNEL_UNLOCK_ONE(NULL);
               return ENOENT;
       }

       revents = events & (POLLOUT | POLLWRNORM | POLLWRBAND);
       if ((events & PUTTERPOLL_EVSET) == 0) {
               KERNEL_UNLOCK_ONE(NULL);
               return revents;
       }

       /* check queue */
       if (pi->pi_pop->pop_waitcount(pi->pi_private))
               revents |= PUTTERPOLL_EVSET;
       else
               selrecord(curlwp, &pi->pi_sel);

       KERNEL_UNLOCK_ONE(NULL);
       return revents;
}

/*
* device close = forced unmount.
*
* unmounting is a frightfully complex operation to avoid races
*/
static int
putter_fop_close(file_t *fp)
{
       struct putter_instance *pi = fp->f_data;
       int rv;

       DPRINTF(("putter_fop_close: device closed\n"));

       KERNEL_LOCK(1, NULL);

restart:
       mutex_enter(&pi_mtx);
       /*
        * First check if the driver was never born.  In that case
        * remove the instance from the list.  If mount is attempted later,
        * it will simply fail.
        */
       if (pi->pi_private == PUTTER_EMBRYO) {
               TAILQ_REMOVE(&putter_ilist, pi, pi_entries);
               mutex_exit(&pi_mtx);

               DPRINTF(("putter_fop_close: data associated with fp %p was "
                   "embryonic\n", fp));

               goto out;
       }

       /*
        * Next, analyze if unmount was called and the instance is dead.
        * In this case we can just free the structure and go home, it
        * was removed from the list by putter_rmprivate().
        */
       if (pi->pi_private == PUTTER_DEAD) {
               mutex_exit(&pi_mtx);

               DPRINTF(("putter_fop_close: putter associated with fp %p (%d) "
                   "dead, freeing\n", fp, pi->pi_idx));

               goto out;
       }

       /*
        * So we have a reference.  Proceed to unravel the
        * underlying driver.
        */
       mutex_exit(&pi_mtx);

       /* hmm?  suspicious locking? */
       if (pi->pi_curput != NULL) {
               pi->pi_pop->pop_releaseout(pi->pi_private, pi->pi_curopaq,
                   ENXIO);
               pi->pi_curput = NULL;
       }
       while ((rv = pi->pi_pop->pop_close(pi->pi_private)) == ERESTART)
               goto restart;

out:
       KERNEL_UNLOCK_ONE(NULL);
       /*
        * Finally, release the instance information.  It was already
        * removed from the list by putter_rmprivate() and we know it's
        * dead, so no need to lock.
        */
       kmem_free(pi, sizeof(struct putter_instance));

       return 0;
}

static int
putter_fop_stat(file_t *fp, struct stat *st)
{
       struct putter_instance *pi = fp->f_data;

       (void)memset(st, 0, sizeof(*st));
       KERNEL_LOCK(1, NULL);
       st->st_dev = makedev(cdevsw_lookup_major(&putter_cdevsw), pi->pi_idx);
       st->st_atimespec = pi->pi_atime;
       st->st_mtimespec = pi->pi_mtime;
       st->st_ctimespec = st->st_birthtimespec = pi->pi_btime;
       st->st_uid = kauth_cred_geteuid(fp->f_cred);
       st->st_gid = kauth_cred_getegid(fp->f_cred);
       st->st_mode = S_IFCHR;
       KERNEL_UNLOCK_ONE(NULL);
       return 0;
}

static int
putter_fop_ioctl(file_t *fp, u_long cmd, void *data)
{

       /*
        * work already done in sys_ioctl().  skip sanity checks to enable
        * setting non-blocking fd on an embryotic driver.
        */
       if (cmd == FIONBIO)
               return 0;

       return EINVAL;
}

/* kqueue stuff */

static void
filt_putterdetach(struct knote *kn)
{
       struct putter_instance *pi = kn->kn_hook;

       KERNEL_LOCK(1, NULL);
       mutex_enter(&pi_mtx);
       selremove_knote(&pi->pi_sel, kn);
       mutex_exit(&pi_mtx);
       KERNEL_UNLOCK_ONE(NULL);
}

static int
filt_putter(struct knote *kn, long hint)
{
       struct putter_instance *pi = kn->kn_hook;
       int error, rv;

       KERNEL_LOCK(1, NULL);
       error = 0;
       mutex_enter(&pi_mtx);
       if (pi->pi_private == PUTTER_EMBRYO || pi->pi_private == PUTTER_DEAD)
               error = 1;
       mutex_exit(&pi_mtx);
       if (error) {
               KERNEL_UNLOCK_ONE(NULL);
               return 0;
       }

       kn->kn_data = pi->pi_pop->pop_waitcount(pi->pi_private);
       rv = kn->kn_data != 0;
       KERNEL_UNLOCK_ONE(NULL);
       return rv;
}

static const struct filterops putter_filtops = {
       .f_flags = FILTEROP_ISFD,
       .f_attach = NULL,
       .f_detach = filt_putterdetach,
       .f_event = filt_putter,
};

static int
putter_fop_kqfilter(file_t *fp, struct knote *kn)
{
       struct putter_instance *pi = fp->f_data;

       KERNEL_LOCK(1, NULL);

       switch (kn->kn_filter) {
       case EVFILT_READ:
               kn->kn_fop = &putter_filtops;
               kn->kn_hook = pi;

               mutex_enter(&pi_mtx);
               selrecord_knote(&pi->pi_sel, kn);
               mutex_exit(&pi_mtx);

               break;
       case EVFILT_WRITE:
               kn->kn_fop = &seltrue_filtops;
               break;
       default:
               KERNEL_UNLOCK_ONE(NULL);
               return EINVAL;
       }

       KERNEL_UNLOCK_ONE(NULL);
       return 0;
}

int
puttercdopen(dev_t dev, int flags, int fmt, struct lwp *l)
{
       struct putter_instance *pi;
       file_t *fp;
       int error, fd, idx;
       proc_t *p;

       p = curproc;
       pi = kmem_alloc(sizeof(struct putter_instance), KM_SLEEP);
       mutex_enter(&pi_mtx);
       idx = get_pi_idx(pi);

       pi->pi_pid = p->p_pid;
       pi->pi_idx = idx;
       pi->pi_curput = NULL;
       pi->pi_curres = 0;
       pi->pi_curopaq = NULL;
       getnanotime(&pi->pi_btime);
       pi->pi_atime = pi->pi_mtime = pi->pi_btime;
       selinit(&pi->pi_sel);
       mutex_exit(&pi_mtx);

       if ((error = fd_allocfile(&fp, &fd)) != 0)
               goto bad1;

       if ((error = putter_configure(dev, flags, fmt, fd)) != 0)
               goto bad2;

       DPRINTF(("puttercdopen: registered embryonic pmp for pid: %d\n",
           pi->pi_pid));

       error = fd_clone(fp, fd, FREAD|FWRITE, &putter_fileops, pi);
       KASSERT(error == EMOVEFD);
       return error;

bad2:
       fd_abort(p, fp, fd);
bad1:
       putter_detach(pi);
       kmem_free(pi, sizeof(struct putter_instance));
       return error;
}

int
puttercdclose(dev_t dev, int flags, int fmt, struct lwp *l)
{

       panic("puttercdclose impossible\n");

       return 0;
}


/*
* Set the private structure for the file descriptor.  This is
* typically done immediately when the counterpart has knowledge
* about the private structure's address and the file descriptor
* (e.g. vfs mount routine).
*
* We only want to make sure that the caller had the right to open the
* device, we don't so much care about which context it gets in case
* the same process opened multiple (since they are equal at this point).
*/
struct putter_instance *
putter_attach(pid_t pid, int fd, void *ppriv, struct putter_ops *pop)
{
       struct putter_instance *pi = NULL;

       mutex_enter(&pi_mtx);
       TAILQ_FOREACH(pi, &putter_ilist, pi_entries) {
               if (pi->pi_pid == pid && pi->pi_private == PUTTER_EMBRYO) {
                       pi->pi_private = ppriv;
                       pi->pi_fd = fd;
                       pi->pi_pop = pop;
                       break;
                   }
       }
       mutex_exit(&pi_mtx);

       DPRINTF(("putter_setprivate: pi at %p (%d/%d)\n", pi,
           pi ? pi->pi_pid : 0, pi ? pi->pi_fd : 0));

       return pi;
}

/*
* Remove fp <-> private mapping.
*/
void
putter_detach(struct putter_instance *pi)
{

       mutex_enter(&pi_mtx);
       TAILQ_REMOVE(&putter_ilist, pi, pi_entries);
       pi->pi_private = PUTTER_DEAD;
       mutex_exit(&pi_mtx);
       seldestroy(&pi->pi_sel);

       DPRINTF(("putter_nukebypmp: nuked %p\n", pi));
}

void
putter_notify(struct putter_instance *pi)
{

       selnotify(&pi->pi_sel, 0, 0);
}

/* search sorted list of instances for free minor, sorted insert arg */
static int
get_pi_idx(struct putter_instance *pi_i)
{
       struct putter_instance *pi;
       int i;

       KASSERT(mutex_owned(&pi_mtx));

       i = 0;
       TAILQ_FOREACH(pi, &putter_ilist, pi_entries) {
               if (i != pi->pi_idx)
                       break;
               i++;
       }

       pi_i->pi_private = PUTTER_EMBRYO;

       if (pi == NULL)
               TAILQ_INSERT_TAIL(&putter_ilist, pi_i, pi_entries);
       else
               TAILQ_INSERT_BEFORE(pi, pi_i, pi_entries);

       return i;
}

MODULE(MODULE_CLASS_DRIVER, putter, NULL);

static int
putter_modcmd(modcmd_t cmd, void *arg)
{
#ifdef _MODULE
       devmajor_t bmajor = NODEVMAJOR, cmajor = NODEVMAJOR;

       switch (cmd) {
       case MODULE_CMD_INIT:
               putterattach();
               return devsw_attach("putter", NULL, &bmajor,
                   &putter_cdevsw, &cmajor);
       case MODULE_CMD_FINI:
               return ENOTTY; /* XXX: putterdetach */
       default:
               return ENOTTY;
       }
#else
       if (cmd == MODULE_CMD_INIT)
               return 0;
       return ENOTTY;
#endif
}

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