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                 ss->snp_tty = NULL;
  129         }
  130 
  131         cv_destroy(&ss->snp_outwait);
  132         free(ss, M_SNP);
  133 }
  134 
  135 /*
  136  * Snoop device node routines.
  137  */
  138 
  139 static int
  140 snp_open(struct cdev *dev, int flag, int mode, struct thread *td)
  141 {
  142         struct snp_softc *ss;
  143 
  144         /* Allocate per-snoop data. */
  145         ss = malloc(sizeof(struct snp_softc), M_SNP, M_WAITOK|M_ZERO);
  146         cv_init(&ss->snp_outwait, "snp out");
  147 
  148         devfs_set_cdevpriv(ss, snp_dtor);
  149 
  150         return (0);
  151 }
  152 
  153 static int
  154 snp_read(struct cdev *dev, struct uio *uio, int flag)
  155 {
  156         int error, oresid = uio->uio_resid;
  157         struct snp_softc *ss;
  158         struct tty *tp;
  159 
  160         if (uio->uio_resid == 0)
  161                 return (0);
  162 
  163         error = devfs_get_cdevpriv((void **)&ss);
  164         if (error != 0)
  165                 return (error);
  166 
  167         tp = ss->snp_tty;
  168         if (tp == NULL || tty_gone(tp))
  169                 return (EIO);
  170 
  171         tty_lock(tp);
  172         for (;;) {
  173                 error = ttyoutq_read_uio(&ss->snp_outq, tp, uio);
  174                 if (error != 0 || uio->uio_resid != oresid)
  175                         break;
  176 
  177                 /* Wait for more data. */
  178                 if (flag & O_NONBLOCK) {
  179                         error = EWOULDBLOCK;
  180                         break;
  181                 }
  182                 error = cv_wait_sig(&ss->snp_outwait, tty_getlock(tp));
  183                 if (error != 0)
  184                         break;
  185                 if (tty_gone(tp)) {
  186                         error = EIO;
  187                         break;
  188                 }
  189         }
  190         tty_unlock(tp);
  191 
  192         return (error);
  193 }
  194 
  195 static int
  196 snp_write(struct cdev *dev, struct uio *uio, int flag)
  197 {
  198         struct snp_softc *ss;
  199         struct tty *tp;
  200         int error, len;
  201         char in[SNP_INPUT_BUFSIZE];
  202 
  203         error = devfs_get_cdevpriv((void **)&ss);
  204         if (error != 0)
  205                 return (error);
  206 
  207         tp = ss->snp_tty;
  208         if (tp == NULL || tty_gone(tp))
  209                 return (EIO);
  210 
  211         while (uio->uio_resid > 0) {
  212                 /* Read new data. */
  213                 len = imin(uio->uio_resid, sizeof in);
  214                 error = uiomove(in, len, uio);
  215                 if (error != 0)
  216                         return (error);
  217 
  218                 tty_lock(tp);
  219 
  220                 /* Driver could have abandoned the TTY in the mean time. */
  221                 if (tty_gone(tp)) {
  222                         tty_unlock(tp);
  223                         return (ENXIO);
  224                 }
  225 
  226                 /*
  227                  * Deliver data to the TTY. Ignore errors for now,
  228                  * because we shouldn't bail out when we're running
  229                  * close to the watermarks.
  230                  */
  231                 ttydisc_rint_simple(tp, in, len);
  232                 ttydisc_rint_done(tp);
  233 
  234                 tty_unlock(tp);
  235         }
  236 
  237         return (0);
  238 }
  239 
  240 static int
  241 snp_ioctl(struct cdev *dev, u_long cmd, caddr_t data, int flags,
  242     struct thread *td)
  243 {
  244         struct snp_softc *ss;
  245         struct tty *tp;
  246         int error;
  247 
  248         error = devfs_get_cdevpriv((void **)&ss);
  249         if (error != 0)
  250                 return (error);
  251 
  252         switch (cmd) {
  253         case SNPSTTY:
  254                 /* Bind TTY to snoop instance. */
  255                 SNP_LOCK();
  256                 tp = ss->snp_tty;
  257                 if (tp != NULL) {
  258                         if (*(int *)data == -1) {
  259                                 tty_lock(tp);
  260                                 ss->snp_tty = NULL;
  261                                 ttyoutq_free(&ss->snp_outq);
  262                                 ttyhook_unregister(tp);
  263                                 error = 0;
  264                         } else {
  265                                 error = EBUSY;
  266                         }
  267                         SNP_UNLOCK();
  268                         return (error);
  269                 }
  270                 /*
  271                  * XXXRW / XXXJA: no capability check here.
  272                  */
  273                 error = ttyhook_register(&ss->snp_tty, td->td_proc,
  274                     *(int *)data, &snp_hook, ss);
  275                 SNP_UNLOCK();
  276                 if (error != 0)
  277                         return (error);
  278 
  279                 /* Now that went okay, allocate a buffer for the queue. */
  280                 tp = ss->snp_tty;
  281                 tty_lock(tp);
  282                 ttyoutq_setsize(&ss->snp_outq, tp, SNP_OUTPUT_BUFSIZE);
  283                 tty_unlock(tp);
  284 
  285                 return (0);
  286         case SNPGTTY:
  287                 /* Obtain device number of associated TTY. */
  288                 if (ss->snp_tty == NULL)
  289                         *(dev_t *)data = NODEV;
  290                 else
  291                         *(dev_t *)data = tty_udev(ss->snp_tty);
  292                 return (0);
  293         case SNPGTYY_32DEV:
  294                 if (ss->snp_tty == NULL)
  295                         *(uint32_t *)data = -1;
  296                 else
  297                         *(uint32_t *)data = tty_udev(ss->snp_tty); /* trunc */
  298                 return (0);
  299         case FIONREAD:
  300                 tp = ss->snp_tty;
  301                 if (tp != NULL) {
  302                         tty_lock(tp);
  303                         if (tty_gone(tp))
  304                                 *(int *)data = SNP_TTYCLOSE;
  305                         else
  306                                 *(int *)data = ttyoutq_bytesused(&ss->snp_outq);
  307                         tty_unlock(tp);
  308                 } else {
  309                         *(int *)data = SNP_DETACH;
  310                 }
  311                 return (0);
  312         default:
  313                 return (ENOTTY);
  314         }
  315 }
  316 
  317 static int
  318 snp_poll(struct cdev *dev, int events, struct thread *td)
  319 {
  320         struct snp_softc *ss;
  321         struct tty *tp;
  322         int revents;
  323 
  324         if (devfs_get_cdevpriv((void **)&ss) != 0)
  325                 return (events &
  326                     (POLLHUP|POLLIN|POLLRDNORM|POLLOUT|POLLWRNORM));
  327 
  328         revents = 0;
  329 
  330         if (events & (POLLIN | POLLRDNORM)) {
  331                 tp = ss->snp_tty;
  332                 if (tp != NULL) {
  333                         tty_lock(tp);
  334                         if (ttyoutq_bytesused(&ss->snp_outq) > 0)
  335                                 revents |= events & (POLLIN | POLLRDNORM);
  336                         tty_unlock(tp);
  337                 }
  338         }
  339 
  340         if (revents == 0)
  341                 selrecord(td, &ss->snp_outpoll);
  342 
  343         return (revents);
  344 }
  345 
  346 /*
  347  * TTY hook events.
  348  */
  349 
  350 static int
  351 snp_modevent(module_t mod, int type, void *data)
  352 {
  353 
  354         switch (type) {
  355         case MOD_LOAD:
  356                 snp_dev = make_dev(&snp_cdevsw, 0,
  357                     UID_ROOT, GID_WHEEL, 0600, "snp");
  358                 return (0);
  359         case MOD_UNLOAD:
  360                 /* XXX: Make existing users leave. */
  361                 destroy_dev(snp_dev);
  362                 return (0);
  363         default:
  364                 return (EOPNOTSUPP);
  365         }
  366 }
  367 
  368 static void
  369 snp_getc_capture(struct tty *tp, const void *buf, size_t len)
  370 {
  371         struct snp_softc *ss = ttyhook_softc(tp);
  372 
  373         ttyoutq_write(&ss->snp_outq, buf, len);
  374 
  375         cv_broadcast(&ss->snp_outwait);
  376         selwakeup(&ss->snp_outpoll);
  377 }
  378 
  379 static moduledata_t snp_mod = {
  380         "snp",
  381         snp_modevent,
  382         NULL
  383 };
  384 
  385 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
