snp.c

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    1 /*-
    2  * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
    3  *
    4  * Copyright (c) 2008 Ed Schouten <ed@FreeBSD.org>
    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 AUTHOR AND CONTRIBUTORS ``AS IS'' AND
   17  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   18  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   19  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
   20  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   21  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   22  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   23  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   24  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   25  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   26  * SUCH DAMAGE.
   27  */
   28 
   29 #include <sys/cdefs.h>
   30 __FBSDID("$FreeBSD$");
   31 
   32 #include <sys/param.h>
   33 #include <sys/conf.h>
   34 #include <sys/fcntl.h>
   35 #include <sys/filio.h>
   36 #include <sys/kernel.h>
   37 #include <sys/malloc.h>
   38 #include <sys/module.h>
   39 #include <sys/poll.h>
   40 #include <sys/proc.h>
   41 #include <sys/snoop.h>
   42 #include <sys/sx.h>
   43 #include <sys/systm.h>
   44 #include <sys/tty.h>
   45 #include <sys/uio.h>
   46 
   47 static struct cdev      *snp_dev;
   48 static MALLOC_DEFINE(M_SNP, "snp", "tty snoop device");
   49 
   50 /* XXX: should be mtx, but TTY can be locked by Giant. */
   51 #if 0
   52 static struct mtx       snp_register_lock;
   53 MTX_SYSINIT(snp_register_lock, &snp_register_lock,
   54     "tty snoop registration", MTX_DEF);
   55 #define SNP_LOCK()      mtx_lock(&snp_register_lock)
   56 #define SNP_UNLOCK()    mtx_unlock(&snp_register_lock)
   57 #else
   58 static struct sx        snp_register_lock;
   59 SX_SYSINIT(snp_register_lock, &snp_register_lock,
   60     "tty snoop registration");
   61 #define SNP_LOCK()      sx_xlock(&snp_register_lock)
   62 #define SNP_UNLOCK()    sx_xunlock(&snp_register_lock)
   63 #endif
   64 
   65 #define SNPGTYY_32DEV   _IOR('T', 89, uint32_t)
   66 
   67 /*
   68  * There is no need to have a big input buffer. In most typical setups,
   69  * we won't inject much data into the TTY, because users can't type
   70  * really fast.
   71  */
   72 #define SNP_INPUT_BUFSIZE       16
   73 /*
   74  * The output buffer has to be really big. Right now we don't support
   75  * any form of flow control, which means we lost any data we can't
   76  * accept. We set the output buffer size to about twice the size of a
   77  * pseudo-terminal/virtual console's output buffer.
   78  */
   79 #define SNP_OUTPUT_BUFSIZE      16384
   80 
   81 static d_open_t         snp_open;
   82 static d_read_t         snp_read;
   83 static d_write_t        snp_write;
   84 static d_ioctl_t        snp_ioctl;
   85 static d_poll_t         snp_poll;
   86 
   87 static struct cdevsw snp_cdevsw = {
   88         .d_version      = D_VERSION,
   89         .d_open         = snp_open,
   90         .d_read         = snp_read,
   91         .d_write        = snp_write,
   92         .d_ioctl        = snp_ioctl,
   93         .d_poll         = snp_poll,
   94         .d_name         = "snp",
   95 };
   96 
   97 static th_getc_capture_t        snp_getc_capture;
   98 
   99 static struct ttyhook snp_hook = {
  100         .th_getc_capture        = snp_getc_capture,
  101 };
  102 
  103 /*
  104  * Per-instance structure.
  105  *
  106  * List of locks
  107  * (r)  locked by snp_register_lock on assignment
  108  * (t)  locked by tty_lock
  109  */
  110 struct snp_softc {
  111         struct tty      *snp_tty;       /* (r) TTY we're snooping. */
  112         struct ttyoutq  snp_outq;       /* (t) Output queue. */
  113         struct cv       snp_outwait;    /* (t) Output wait queue. */
  114         struct selinfo  snp_outpoll;    /* (t) Output polling. */
  115 };
  116 
  117 static void
  118 snp_dtor(void *data)
  119 {
  120         struct snp_softc *ss = data;
  121         struct tty *tp;
  122 
  123         tp = ss->snp_tty;
  124         if (tp != NULL) {
  125                 tty_lock(tp);
  126                 ttyoutq_free(&ss->snp_outq);
  127                 ttyhook_unregister(tp);
  128         }
  129 
  130         cv_destroy(&ss->snp_outwait);
  131         free(ss, M_SNP);
  132 }
  133 
  134 /*
  135  * Snoop device node routines.
  136  */
  137 
  138 static int
  139 snp_open(struct cdev *dev, int flag, int mode, struct thread *td)
  140 {
  141         struct snp_softc *ss;
  142 
  143         /* Allocate per-snoop data. */
  144         ss = malloc(sizeof(struct snp_softc), M_SNP, M_WAITOK|M_ZERO);
  145         cv_init(&ss->snp_outwait, "snp out");
  146 
  147         devfs_set_cdevpriv(ss, snp_dtor);
  148 
  149         return (0);
  150 }
  151 
  152 static int
  153 snp_read(struct cdev *dev, struct uio *uio, int flag)
  154 {
  155         int error, oresid = uio->uio_resid;
  156         struct snp_softc *ss;
  157         struct tty *tp;
  158 
  159         if (uio->uio_resid == 0)
  160                 return (0);
  161 
  162         error = devfs_get_cdevpriv((void **)&ss);
  163         if (error != 0)
  164                 return (error);
  165 
  166         tp = ss->snp_tty;
  167         if (tp == NULL || tty_gone(tp))
  168                 return (EIO);
  169 
  170         tty_lock(tp);
  171         for (;;) {
  172                 error = ttyoutq_read_uio(&ss->snp_outq, tp, uio);
  173                 if (error != 0 || uio->uio_resid != oresid)
  174                         break;
  175 
  176                 /* Wait for more data. */
  177                 if (flag & O_NONBLOCK) {
  178                         error = EWOULDBLOCK;
  179                         break;
  180                 }
  181                 error = cv_wait_sig(&ss->snp_outwait, tty_getlock(tp));
  182                 if (error != 0)
  183                         break;
  184                 if (tty_gone(tp)) {
  185                         error = EIO;
  186                         break;
  187                 }
  188         }
  189         tty_unlock(tp);
  190 
  191         return (error);
  192 }
  193 
  194 static int
  195 snp_write(struct cdev *dev, struct uio *uio, int flag)
  196 {
  197         struct snp_softc *ss;
  198         struct tty *tp;
  199         int error, len;
  200         char in[SNP_INPUT_BUFSIZE];
  201 
  202         error = devfs_get_cdevpriv((void **)&ss);
  203         if (error != 0)
  204                 return (error);
  205 
  206         tp = ss->snp_tty;
  207         if (tp == NULL || tty_gone(tp))
  208                 return (EIO);
  209 
  210         while (uio->uio_resid > 0) {
  211                 /* Read new data. */
  212                 len = imin(uio->uio_resid, sizeof in);
  213                 error = uiomove(in, len, uio);
  214                 if (error != 0)
  215                         return (error);
  216 
  217                 tty_lock(tp);
  218 
  219                 /* Driver could have abandoned the TTY in the mean time. */
  220                 if (tty_gone(tp)) {
  221                         tty_unlock(tp);
  222                         return (ENXIO);
  223                 }
  224 
  225                 /*
  226                  * Deliver data to the TTY. Ignore errors for now,
  227                  * because we shouldn't bail out when we're running
  228                  * close to the watermarks.
  229                  */
  230                 ttydisc_rint_simple(tp, in, len);
  231                 ttydisc_rint_done(tp);
  232 
  233                 tty_unlock(tp);
  234         }
  235 
  236         return (0);
  237 }
  238 
  239 static int
  240 snp_ioctl(struct cdev *dev, u_long cmd, caddr_t data, int flags,
  241     struct thread *td)
  242 {
  243         struct snp_softc *ss;
  244         struct tty *tp;
  245         int error;
  246 
  247         error = devfs_get_cdevpriv((void **)&ss);
  248         if (error != 0)
  249                 return (error);
  250 
  251         switch (cmd) {
  252         case SNPSTTY:
  253                 /* Bind TTY to snoop instance. */
  254                 SNP_LOCK();
  255                 if (ss->snp_tty != NULL) {
  256                         SNP_UNLOCK();
  257                         return (EBUSY);
  258                 }
  259                 /*
  260                  * XXXRW / XXXJA: no capability check here.
  261                  */
  262                 error = ttyhook_register(&ss->snp_tty, td->td_proc,
  263                     *(int *)data, &snp_hook, ss);
  264                 SNP_UNLOCK();
  265                 if (error != 0)
  266                         return (error);
  267 
  268                 /* Now that went okay, allocate a buffer for the queue. */
  269                 tp = ss->snp_tty;
  270                 tty_lock(tp);
  271                 ttyoutq_setsize(&ss->snp_outq, tp, SNP_OUTPUT_BUFSIZE);
  272                 tty_unlock(tp);
  273 
  274                 return (0);
  275         case SNPGTTY:
  276                 /* Obtain device number of associated TTY. */
  277                 if (ss->snp_tty == NULL)
  278                         *(dev_t *)data = NODEV;
  279                 else
  280                         *(dev_t *)data = tty_udev(ss->snp_tty);
  281                 return (0);
  282         case SNPGTYY_32DEV:
  283                 if (ss->snp_tty == NULL)
  284                         *(uint32_t *)data = -1;
  285                 else
  286                         *(uint32_t *)data = tty_udev(ss->snp_tty); /* trunc */
  287                 return (0);
  288         case FIONREAD:
  289                 tp = ss->snp_tty;
  290                 if (tp != NULL) {
  291                         tty_lock(tp);
  292                         *(int *)data = ttyoutq_bytesused(&ss->snp_outq);
  293                         tty_unlock(tp);
  294                 } else {
  295                         *(int *)data = 0;
  296                 }
  297                 return (0);
  298         default:
  299                 return (ENOTTY);
  300         }
  301 }
  302 
  303 static int
  304 snp_poll(struct cdev *dev, int events, struct thread *td)
  305 {
  306         struct snp_softc *ss;
  307         struct tty *tp;
  308         int revents;
  309 
  310         if (devfs_get_cdevpriv((void **)&ss) != 0)
  311                 return (events &
  312                     (POLLHUP|POLLIN|POLLRDNORM|POLLOUT|POLLWRNORM));
  313 
  314         revents = 0;
  315 
  316         if (events & (POLLIN | POLLRDNORM)) {
  317                 tp = ss->snp_tty;
  318                 if (tp != NULL) {
  319                         tty_lock(tp);
  320                         if (ttyoutq_bytesused(&ss->snp_outq) > 0)
  321                                 revents |= events & (POLLIN | POLLRDNORM);
  322                         tty_unlock(tp);
  323                 }
  324         }
  325 
  326         if (revents == 0)
  327                 selrecord(td, &ss->snp_outpoll);
  328 
  329         return (revents);
  330 }
  331 
  332 /*
  333  * TTY hook events.
  334  */
  335 
  336 static int
  337 snp_modevent(module_t mod, int type, void *data)
  338 {
  339 
  340         switch (type) {
  341         case MOD_LOAD:
  342                 snp_dev = make_dev(&snp_cdevsw, 0,
  343                     UID_ROOT, GID_WHEEL, 0600, "snp");
  344                 return (0);
  345         case MOD_UNLOAD:
  346                 /* XXX: Make existing users leave. */
  347                 destroy_dev(snp_dev);
  348                 return (0);
  349         default:
  350                 return (EOPNOTSUPP);
  351         }
  352 }
  353 
  354 static void
  355 snp_getc_capture(struct tty *tp, const void *buf, size_t len)
  356 {
  357         struct snp_softc *ss = ttyhook_softc(tp);
  358 
  359         ttyoutq_write(&ss->snp_outq, buf, len);
  360 
  361         cv_broadcast(&ss->snp_outwait);
  362         selwakeup(&ss->snp_outpoll);
  363 }
  364 
  365 static moduledata_t snp_mod = {
  366         "snp",
  367         snp_modevent,
  368         NULL
  369 };
  370 
  371 DECLARE_MODULE(snp, snp_mod, SI_SUB_DRIVERS, SI_ORDER_MIDDLE);
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FreeBSD/Linux Kernel Cross Reference sys/dev/snp/snp.c

FreeBSD/Linux Kernel Cross Reference
sys/dev/snp/snp.c
