tty_ptm.c

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    1 /*      $NetBSD: tty_ptm.c,v 1.45 2022/09/29 12:18:27 christos Exp $    */
    2 
    3 /*-
    4  * Copyright (c) 2004, 2020 The NetBSD Foundation, Inc.
    5  * All rights reserved.
    6  *
    7  * Redistribution and use in source and binary forms, with or without
    8  * modification, are permitted provided that the following conditions
    9  * are met:
   10  * 1. Redistributions of source code must retain the above copyright
   11  *    notice, this list of conditions and the following disclaimer.
   12  * 2. Redistributions in binary form must reproduce the above copyright
   13  *    notice, this list of conditions and the following disclaimer in the
   14  *    documentation and/or other materials provided with the distribution.
   15  *
   16  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
   17  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
   18  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
   19  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
   20  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
   21  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
   22  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
   23  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
   24  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
   25  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
   26  * POSSIBILITY OF SUCH DAMAGE.
   27  */
   28 
   29 #include <sys/cdefs.h>
   30 __KERNEL_RCSID(0, "$NetBSD: tty_ptm.c,v 1.45 2022/09/29 12:18:27 christos Exp $");
   31 
   32 #ifdef _KERNEL_OPT
   33 #include "opt_compat_netbsd.h"
   34 #include "opt_ptm.h"
   35 #endif
   36 
   37 /* pty multiplexor driver /dev/ptm{,x} */
   38 
   39 #include <sys/param.h>
   40 #include <sys/systm.h>
   41 #include <sys/ioctl.h>
   42 #include <sys/proc.h>
   43 #include <sys/tty.h>
   44 #include <sys/stat.h>
   45 #include <sys/file.h>
   46 #include <sys/uio.h>
   47 #include <sys/kernel.h>
   48 #include <sys/vnode.h>
   49 #include <sys/namei.h>
   50 #include <sys/signalvar.h>
   51 #include <sys/filedesc.h>
   52 #include <sys/conf.h>
   53 #include <sys/poll.h>
   54 #include <sys/pty.h>
   55 #include <sys/kauth.h>
   56 #include <sys/compat_stub.h>
   57 
   58 #include <miscfs/specfs/specdev.h>
   59 
   60 #include <compat/sys/ttycom.h>
   61 
   62 #include "ioconf.h"
   63 
   64 #ifdef DEBUG_PTM
   65 #define DPRINTF(a)      printf a
   66 #else
   67 #define DPRINTF(a)
   68 #endif
   69 
   70 #ifdef NO_DEV_PTM
   71 const struct cdevsw ptm_cdevsw = {
   72         .d_open = noopen,
   73         .d_close = noclose,
   74         .d_read = noread,
   75         .d_write = nowrite,
   76         .d_ioctl = noioctl,
   77         .d_stop = nostop,
   78         .d_tty = notty,
   79         .d_poll = nopoll,
   80         .d_mmap = nommap,
   81         .d_kqfilter = nokqfilter,
   82         .d_discard = nodiscard,
   83         .d_flag = D_TTY
   84 };
   85 #else
   86 
   87 int pts_major, ptc_major;
   88 
   89 static dev_t pty_getfree(void);
   90 static int pty_alloc_master(struct lwp *, int *, dev_t *, struct mount *, int);
   91 static int pty_alloc_slave(struct lwp *, int *, dev_t, struct mount *);
   92 static int pty_vn_open(struct vnode *, struct lwp *);
   93 
   94 int
   95 pty_getmp(struct lwp *l, struct mount **mpp)
   96 {
   97         if (ptm == NULL)
   98                 return EOPNOTSUPP;
   99 
  100         return (*ptm->getmp)(l, mpp);
  101 }
  102 
  103 dev_t
  104 pty_makedev(char ms, int minor)
  105 {
  106         return makedev(ms == 't' ? pts_major : ptc_major, minor);
  107 }
  108 
  109 
  110 static dev_t
  111 pty_getfree(void)
  112 {
  113         extern kmutex_t pt_softc_mutex;
  114         int i;
  115 
  116         mutex_enter(&pt_softc_mutex);
  117         for (i = 0; i < npty; i++) {
  118                 if (pty_isfree(i, 0))
  119                         break;
  120         }
  121         mutex_exit(&pt_softc_mutex);
  122         return pty_makedev('t', i);
  123 }
  124 
  125 /*
  126  * Hacked up version of vn_open. We _only_ handle ptys and only open
  127  * them with FREAD|FWRITE and never deal with creat or stuff like that.
  128  *
  129  * We need it because we have to fake up root credentials to open the pty.
  130  */
  131 int
  132 pty_vn_open(struct vnode *vp, struct lwp *l)
  133 {
  134         int error;
  135 
  136         if (vp->v_type != VCHR) {
  137                 vput(vp);
  138                 return EINVAL;
  139         }
  140 
  141         error = VOP_OPEN(vp, FREAD|FWRITE, lwp0.l_cred);
  142 
  143         if (error) {
  144                 /* only ptys mean we can't get these */
  145                 KASSERT(error != EDUPFD && error != EMOVEFD);
  146                 vput(vp);
  147                 return error;
  148         }
  149 
  150         mutex_enter(vp->v_interlock);
  151         vp->v_writecount++;
  152         mutex_exit(vp->v_interlock);
  153 
  154         return 0;
  155 }
  156 
  157 static int
  158 pty_alloc_master(struct lwp *l, int *fd, dev_t *dev, struct mount *mp,
  159     int flags)
  160 {
  161         int error;
  162         struct file *fp;
  163         struct vnode *vp;
  164         int md;
  165 
  166         if ((error = fd_allocfile(&fp, fd)) != 0) {
  167                 DPRINTF(("fd_allocfile %d\n", error));
  168                 return error;
  169         }
  170 retry:
  171         /* Find and open a free master pty. */
  172         *dev = pty_getfree();
  173         md = minor(*dev);
  174         if ((error = pty_check(md)) != 0) {
  175                 DPRINTF(("pty_check %d\n", error));
  176                 goto bad;
  177         }
  178         if (ptm == NULL) {
  179                 DPRINTF(("no ptm\n"));
  180                 error = EOPNOTSUPP;
  181                 goto bad;
  182         }
  183         if ((error = (*ptm->allocvp)(mp, l, &vp, *dev, 'p')) != 0) {
  184                 DPRINTF(("pty_allocvp %d\n", error));
  185                 goto bad;
  186         }
  187 
  188         if ((error = pty_vn_open(vp, l)) != 0) {
  189                 DPRINTF(("pty_vn_open %d\n", error));
  190                 /*
  191                  * Check if the master open failed because we lost
  192                  * the race to grab it.
  193                  */
  194                 if (error != EIO)
  195                         goto bad;
  196                 error = !pty_isfree(md, 1);
  197                 DPRINTF(("pty_isfree %d\n", error));
  198                 if (error)
  199                         goto retry;
  200                 else
  201                         goto bad;
  202         }
  203         fp->f_flag = FREAD|FWRITE|(flags&FMASK);
  204         fp->f_type = DTYPE_VNODE;
  205         fp->f_ops = &vnops;
  206         fp->f_vnode = vp;
  207 
  208         VOP_UNLOCK(vp);
  209         fd_set_exclose(l, *fd, (flags & O_CLOEXEC) != 0);
  210         fd_affix(curproc, fp, *fd);
  211         return 0;
  212 bad:
  213         fd_abort(curproc, fp, *fd);
  214         return error;
  215 }
  216 
  217 int
  218 pty_grant_slave(struct lwp *l, dev_t dev, struct mount *mp)
  219 {
  220         int error;
  221         struct vnode *vp;
  222 
  223         /*
  224          * Open the slave.
  225          * namei -> setattr -> unlock -> revoke -> vrele ->
  226          * namei -> open -> unlock
  227          * Three stage rocket:
  228          * 1. Change the owner and permissions on the slave.
  229          * 2. Revoke all the users of the slave.
  230          * 3. open the slave.
  231          */
  232         if (ptm == NULL)
  233                 return EOPNOTSUPP;
  234         if ((error = (*ptm->allocvp)(mp, l, &vp, dev, 't')) != 0)
  235                 return error;
  236 
  237         if ((vp->v_mount->mnt_flag & MNT_RDONLY) == 0) {
  238                 struct vattr vattr;
  239                 (*ptm->getvattr)(mp, l, &vattr);
  240                 /* Do the VOP_SETATTR() as root. */
  241                 error = VOP_SETATTR(vp, &vattr, lwp0.l_cred);
  242                 if (error) {
  243                         DPRINTF(("setattr %d\n", error));
  244                         vput(vp);
  245                         return error;
  246                 }
  247         }
  248         VOP_UNLOCK(vp);
  249         VOP_REVOKE(vp, REVOKEALL);
  250 
  251         /*
  252          * The vnode is useless after the revoke, we need to get it again.
  253          */
  254         vrele(vp);
  255         return 0;
  256 }
  257 
  258 static int
  259 pty_alloc_slave(struct lwp *l, int *fd, dev_t dev, struct mount *mp)
  260 {
  261         int error;
  262         struct file *fp;
  263         struct vnode *vp;
  264 
  265         /* Grab a filedescriptor for the slave */
  266         if ((error = fd_allocfile(&fp, fd)) != 0) {
  267                 DPRINTF(("fd_allocfile %d\n", error));
  268                 return error;
  269         }
  270 
  271         if (ptm == NULL) {
  272                 error = EOPNOTSUPP;
  273                 goto bad;
  274         }
  275 
  276         if ((error = (*ptm->allocvp)(mp, l, &vp, dev, 't')) != 0)
  277                 goto bad;
  278         if ((error = pty_vn_open(vp, l)) != 0)
  279                 goto bad;
  280 
  281         fp->f_flag = FREAD|FWRITE;
  282         fp->f_type = DTYPE_VNODE;
  283         fp->f_ops = &vnops;
  284         fp->f_vnode = vp;
  285         VOP_UNLOCK(vp);
  286         fd_affix(curproc, fp, *fd);
  287         return 0;
  288 bad:
  289         fd_abort(curproc, fp, *fd);
  290         return error;
  291 }
  292 
  293 struct ptm_pty *
  294 pty_sethandler(struct ptm_pty *nptm)
  295 {
  296         struct ptm_pty *optm = ptm;
  297         ptm = nptm;
  298         return optm;
  299 }
  300 
  301 int
  302 pty_fill_ptmget(struct lwp *l, dev_t dev, int cfd, int sfd, void *data, struct mount *mp)
  303 {
  304         struct ptmget *ptmg = data;
  305         int error;
  306 
  307         if (ptm == NULL)
  308                 return EOPNOTSUPP;
  309 
  310         ptmg->cfd = cfd == -1 ? minor(dev) : cfd;
  311         ptmg->sfd = sfd == -1 ? minor(dev) : sfd;
  312 
  313         error = (*ptm->makename)(mp, l, ptmg->cn, sizeof(ptmg->cn), dev, 'p');
  314         if (error)
  315                 return error;
  316 
  317         return (*ptm->makename)(mp, l, ptmg->sn, sizeof(ptmg->sn), dev, 't');
  318 }
  319 
  320 void
  321 /*ARGSUSED*/
  322 ptmattach(int n)
  323 {
  324         extern const struct cdevsw pts_cdevsw, ptc_cdevsw;
  325         /* find the major and minor of the pty devices */
  326         if ((pts_major = cdevsw_lookup_major(&pts_cdevsw)) == -1)
  327                 panic("%s: Can't find pty slave in cdevsw", __func__);
  328         if ((ptc_major = cdevsw_lookup_major(&ptc_cdevsw)) == -1)
  329                 panic("%s: Can't find pty master in cdevsw", __func__);
  330 #ifdef COMPAT_BSDPTY
  331         ptm = &ptm_bsdpty;
  332 #endif
  333 }
  334 
  335 static int
  336 /*ARGSUSED*/
  337 ptmopen(dev_t dev, int flag, int mode, struct lwp *l)
  338 {
  339         int error;
  340         int fd;
  341         dev_t ttydev;
  342         struct mount *mp;
  343 
  344         switch(minor(dev)) {
  345         case 0:         /* /dev/ptmx */
  346         case 2:         /* /emul/linux/dev/ptmx */
  347                 if ((error = pty_getmp(l, &mp)) != 0)
  348                         return error;
  349                 if ((error = pty_alloc_master(l, &fd, &ttydev, mp, flag)) != 0)
  350                         return error;
  351                 if (minor(dev) == 2) {
  352                         /*
  353                          * Linux ptyfs grants the pty right here.
  354                          * Handle this case here, instead of writing
  355                          * a new linux module.
  356                          */
  357                         if ((error = pty_grant_slave(l, ttydev, mp)) != 0) {
  358                                 file_t *fp = fd_getfile(fd);
  359                                 if (fp != NULL) {
  360                                         fd_close(fd);
  361                                 }
  362                                 return error;
  363                         }
  364                 }
  365                 curlwp->l_dupfd = fd;
  366                 return EMOVEFD;
  367         case 1:         /* /dev/ptm */
  368                 return 0;
  369         default:
  370                 return ENODEV;
  371         }
  372 }
  373 
  374 static int
  375 /*ARGSUSED*/
  376 ptmclose(dev_t dev, int flag, int mode, struct lwp *l)
  377 {
  378 
  379         return (0);
  380 }
  381 
  382 static int
  383 /*ARGSUSED*/
  384 ptmioctl(dev_t dev, u_long cmd, void *data, int flag, struct lwp *l)
  385 {
  386         int error;
  387         dev_t newdev;
  388         int cfd, sfd;
  389         file_t *fp;
  390         struct mount *mp;
  391 
  392         error = 0;
  393         switch (cmd) {
  394         case TIOCPTMGET:
  395                 if ((error = pty_getmp(l, &mp)) != 0)
  396                         return error;
  397 
  398                 if ((error = pty_alloc_master(l, &cfd, &newdev, mp, 0)) != 0)
  399                         return error;
  400 
  401                 if ((error = pty_grant_slave(l, newdev, mp)) != 0)
  402                         goto bad;
  403 
  404                 if ((error = pty_alloc_slave(l, &sfd, newdev, mp)) != 0)
  405                         goto bad;
  406 
  407                 /* now, put the indices and names into struct ptmget */
  408                 if ((error = pty_fill_ptmget(l, newdev, cfd, sfd, data, mp)) != 0)
  409                         goto bad2;
  410                 return 0;
  411         default:
  412                 MODULE_HOOK_CALL(tty_ptmioctl_60_hook,
  413                     (dev, cmd, data, flag, l), EPASSTHROUGH, error);
  414                 if (error != EPASSTHROUGH)
  415                         return error;
  416                 DPRINTF(("ptmioctl EINVAL\n"));
  417                 return EINVAL;
  418         }
  419 bad2:
  420         fp = fd_getfile(sfd);
  421         if (fp != NULL) {
  422                 fd_close(sfd);
  423         }
  424  bad:
  425         fp = fd_getfile(cfd);
  426         if (fp != NULL) {
  427                 fd_close(cfd);
  428         }
  429         return error;
  430 }
  431 
  432 const struct cdevsw ptm_cdevsw = {
  433         .d_open = ptmopen,
  434         .d_close = ptmclose,
  435         .d_read = noread,
  436         .d_write = nowrite,
  437         .d_ioctl = ptmioctl,
  438         .d_stop = nullstop,
  439         .d_tty = notty,
  440         .d_poll = nopoll,
  441         .d_mmap = nommap,
  442         .d_kqfilter = nokqfilter,
  443         .d_discard = nodiscard,
  444         .d_flag = D_TTY
  445 };
  446 #endif
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FreeBSD/Linux Kernel Cross Reference sys/kern/tty_ptm.c

FreeBSD/Linux Kernel Cross Reference
sys/kern/tty_ptm.c
