Reimplement the /dev/console device node.

One of the pieces of code that I had left alone during the development
of the MPSAFE TTY layer, was tty_cons.c. This file actually has two
different functions:

- It contains low-level console input/output routines (cnputc(), etc).

- It creates /dev/console and wraps all its cdevsw calls to the
  appropriate TTY.

This commit reimplements the second set of functions by moving it
directly into the TTY layer. /dev/console is now a character device node
that's basically a regular TTY, but does a lookup of `si_drv1' each time
you open it. d_write has also been changed to call log_console().
d_close() is not present, because we must make sure we don't revoke the
TTY after writing a log message to it.

Even though I'm not convinced this is in line with the future directions
of our console code, it is a good move for now. It removes recursive
locking from the top half of the TTY layer. The previous implementation
called into the TTY layer with Giant held.

I'm renaming tty_cons.c to kern_cons.c now. The code hardly contains any
TTY related bits, so we'd better give it a less misleading name.

Tested by:	Andrzej Tobola <ato iem pw edu pl>,
		Carlos A.M. dos Santos <unixmania gmail com>,
		Eygene Ryabinkin <rea-fbsd codelabs ru>

1 files changed, 566 insertions, 0 deletions

diff --git a/sys/kern/kern_cons.c b/sys/kern/kern_cons.c
new file mode 100644
index 0000000..3930f59
--- /dev/null
+++ b/sys/kern/kern_cons.c
@@ -0,0 +1,566 @@
+/*-
+ * Copyright (c) 1988 University of Utah.
+ * Copyright (c) 1991 The Regents of the University of California.
+ * All rights reserved.
+ *
+ * This code is derived from software contributed to Berkeley by
+ * the Systems Programming Group of the University of Utah Computer
+ * Science Department.
+ *
+ * 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.
+ * 4. 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.
+ *
+ *	from: @(#)cons.c	7.2 (Berkeley) 5/9/91
+ */
+
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+#include "opt_ddb.h"
+
+#include <sys/param.h>
+#include <sys/systm.h>
+#include <sys/lock.h>
+#include <sys/mutex.h>
+#include <sys/conf.h>
+#include <sys/cons.h>
+#include <sys/fcntl.h>
+#include <sys/kdb.h>
+#include <sys/kernel.h>
+#include <sys/malloc.h>
+#include <sys/msgbuf.h>
+#include <sys/namei.h>
+#include <sys/priv.h>
+#include <sys/proc.h>
+#include <sys/queue.h>
+#include <sys/reboot.h>
+#include <sys/sysctl.h>
+#include <sys/sbuf.h>
+#include <sys/tty.h>
+#include <sys/uio.h>
+#include <sys/vnode.h>
+
+#include <ddb/ddb.h>
+
+#include <machine/cpu.h>
+#include <machine/clock.h>
+
+static MALLOC_DEFINE(M_TTYCONS, "tty console", "tty console handling");
+
+struct cn_device {
+	STAILQ_ENTRY(cn_device) cnd_next;
+	struct		consdev *cnd_cn;
+};
+
+#define CNDEVPATHMAX	32
+#define CNDEVTAB_SIZE	4
+static struct cn_device cn_devtab[CNDEVTAB_SIZE];
+static STAILQ_HEAD(, cn_device) cn_devlist =
+    STAILQ_HEAD_INITIALIZER(cn_devlist);
+
+int	cons_avail_mask = 0;	/* Bit mask. Each registered low level console
+				 * which is currently unavailable for inpit
+				 * (i.e., if it is in graphics mode) will have
+				 * this bit cleared.
+				 */
+static int cn_mute;
+static char *consbuf;			/* buffer used by `consmsgbuf' */
+static struct callout conscallout;	/* callout for outputting to constty */
+struct msgbuf consmsgbuf;		/* message buffer for console tty */
+static u_char console_pausing;		/* pause after each line during probe */
+static char *console_pausestr=
+"<pause; press any key to proceed to next line or '.' to end pause mode>";
+struct tty *constty;			/* pointer to console "window" tty */
+static struct mtx cnputs_mtx;		/* Mutex for cnputs(). */
+static int use_cnputs_mtx = 0;		/* != 0 if cnputs_mtx locking reqd. */
+
+static void constty_timeout(void *arg);
+
+static struct consdev cons_consdev;
+DATA_SET(cons_set, cons_consdev);
+SET_DECLARE(cons_set, struct consdev);
+
+void
+cninit(void)
+{
+	struct consdev *best_cn, *cn, **list;
+
+	/*
+	 * Check if we should mute the console (for security reasons perhaps)
+	 * It can be changes dynamically using sysctl kern.consmute
+	 * once we are up and going.
+	 * 
+	 */
+        cn_mute = ((boothowto & (RB_MUTE
+			|RB_SINGLE
+			|RB_VERBOSE
+			|RB_ASKNAME)) == RB_MUTE);
+
+	/*
+	 * Find the first console with the highest priority.
+	 */
+	best_cn = NULL;
+	SET_FOREACH(list, cons_set) {
+		cn = *list;
+		cnremove(cn);
+		if (cn->cn_probe == NULL)
+			continue;
+		cn->cn_probe(cn);
+		if (cn->cn_pri == CN_DEAD)
+			continue;
+		if (best_cn == NULL || cn->cn_pri > best_cn->cn_pri)
+			best_cn = cn;
+		if (boothowto & RB_MULTIPLE) {
+			/*
+			 * Initialize console, and attach to it.
+			 */
+			cn->cn_init(cn);
+			cnadd(cn);
+		}
+	}
+	if (best_cn == NULL)
+		return;
+	if ((boothowto & RB_MULTIPLE) == 0) {
+		best_cn->cn_init(best_cn);
+		cnadd(best_cn);
+	}
+	if (boothowto & RB_PAUSE)
+		console_pausing = 1;
+	/*
+	 * Make the best console the preferred console.
+	 */
+	cnselect(best_cn);
+}
+
+void
+cninit_finish()
+{
+	console_pausing = 0;
+} 
+
+/* add a new physical console to back the virtual console */
+int
+cnadd(struct consdev *cn)
+{
+	struct cn_device *cnd;
+	int i;
+
+	STAILQ_FOREACH(cnd, &cn_devlist, cnd_next)
+		if (cnd->cnd_cn == cn)
+			return (0);
+	for (i = 0; i < CNDEVTAB_SIZE; i++) {
+		cnd = &cn_devtab[i];
+		if (cnd->cnd_cn == NULL)
+			break;
+	}
+	if (cnd->cnd_cn != NULL)
+		return (ENOMEM);
+	cnd->cnd_cn = cn;
+	if (cn->cn_name[0] == '\0') {
+		/* XXX: it is unclear if/where this print might output */
+		printf("WARNING: console at %p has no name\n", cn);
+	}
+	STAILQ_INSERT_TAIL(&cn_devlist, cnd, cnd_next);
+	if (STAILQ_FIRST(&cn_devlist) == cnd)
+		ttyconsdev_select(cnd->cnd_cn->cn_name);
+
+	/* Add device to the active mask. */
+	cnavailable(cn, (cn->cn_flags & CN_FLAG_NOAVAIL) == 0);
+
+	return (0);
+}
+
+void
+cnremove(struct consdev *cn)
+{
+	struct cn_device *cnd;
+	int i;
+
+	STAILQ_FOREACH(cnd, &cn_devlist, cnd_next) {
+		if (cnd->cnd_cn != cn)
+			continue;
+		if (STAILQ_FIRST(&cn_devlist) == cnd)
+			ttyconsdev_select(NULL);
+		STAILQ_REMOVE(&cn_devlist, cnd, cn_device, cnd_next);
+		cnd->cnd_cn = NULL;
+
+		/* Remove this device from available mask. */
+		for (i = 0; i < CNDEVTAB_SIZE; i++) 
+			if (cnd == &cn_devtab[i]) {
+				cons_avail_mask &= ~(1 << i);
+				break;
+			}
+#if 0
+		/*
+		 * XXX
+		 * syscons gets really confused if console resources are
+		 * freed after the system has initialized.
+		 */
+		if (cn->cn_term != NULL)
+			cn->cn_term(cn);
+#endif
+		return;
+	}
+}
+
+void
+cnselect(struct consdev *cn)
+{
+	struct cn_device *cnd;
+
+	STAILQ_FOREACH(cnd, &cn_devlist, cnd_next) {
+		if (cnd->cnd_cn != cn)
+			continue;
+		if (cnd == STAILQ_FIRST(&cn_devlist))
+			return;
+		STAILQ_REMOVE(&cn_devlist, cnd, cn_device, cnd_next);
+		STAILQ_INSERT_HEAD(&cn_devlist, cnd, cnd_next);
+		ttyconsdev_select(cnd->cnd_cn->cn_name);
+		return;
+	}
+}
+
+void
+cnavailable(struct consdev *cn, int available)
+{
+	int i;
+
+	for (i = 0; i < CNDEVTAB_SIZE; i++) {
+		if (cn_devtab[i].cnd_cn == cn)
+			break;
+	}
+	if (available) {
+		if (i < CNDEVTAB_SIZE)
+			cons_avail_mask |= (1 << i); 
+		cn->cn_flags &= ~CN_FLAG_NOAVAIL;
+	} else {
+		if (i < CNDEVTAB_SIZE)
+			cons_avail_mask &= ~(1 << i);
+		cn->cn_flags |= CN_FLAG_NOAVAIL;
+	}
+}
+
+int
+cnunavailable(void)
+{
+
+	return (cons_avail_mask == 0);
+}
+
+/*
+ * sysctl_kern_console() provides output parseable in conscontrol(1).
+ */
+static int
+sysctl_kern_console(SYSCTL_HANDLER_ARGS)
+{
+	struct cn_device *cnd;
+	struct consdev *cp, **list;
+	char *p;
+	int delete, error;
+	struct sbuf *sb;
+
+	sb = sbuf_new(NULL, NULL, CNDEVPATHMAX * 2, SBUF_AUTOEXTEND);
+	if (sb == NULL)
+		return (ENOMEM);
+	sbuf_clear(sb);
+	STAILQ_FOREACH(cnd, &cn_devlist, cnd_next)
+		sbuf_printf(sb, "%s,", cnd->cnd_cn->cn_name);
+	sbuf_printf(sb, "/");
+	SET_FOREACH(list, cons_set) {
+		cp = *list;
+		if (cp->cn_name[0] != '\0')
+			sbuf_printf(sb, "%s,", cp->cn_name);
+	}
+	sbuf_finish(sb);
+	error = sysctl_handle_string(oidp, sbuf_data(sb), sbuf_len(sb), req);
+	if (error == 0 && req->newptr != NULL) {
+		p = sbuf_data(sb);
+		error = ENXIO;
+		delete = 0;
+		if (*p == '-') {
+			delete = 1;
+			p++;
+		}
+		SET_FOREACH(list, cons_set) {
+			cp = *list;
+			if (strcmp(p, cp->cn_name) != 0)
+				continue;
+			if (delete) {
+				cnremove(cp);
+				error = 0;
+			} else {
+				error = cnadd(cp);
+				if (error == 0)
+					cnselect(cp);
+			}
+			break;
+		}
+	}
+	sbuf_delete(sb);
+	return (error);
+}
+
+SYSCTL_PROC(_kern, OID_AUTO, console, CTLTYPE_STRING|CTLFLAG_RW,
+	0, 0, sysctl_kern_console, "A", "Console device control");
+
+/*
+ * User has changed the state of the console muting.
+ * This may require us to open or close the device in question.
+ */
+static int
+sysctl_kern_consmute(SYSCTL_HANDLER_ARGS)
+{
+	int error;
+	int ocn_mute;
+
+	ocn_mute = cn_mute;
+	error = sysctl_handle_int(oidp, &cn_mute, 0, req);
+	if (error != 0 || req->newptr == NULL)
+		return (error);
+	return (error);
+}
+
+SYSCTL_PROC(_kern, OID_AUTO, consmute, CTLTYPE_INT|CTLFLAG_RW,
+	0, sizeof(cn_mute), sysctl_kern_consmute, "I", "");
+
+/*
+ * Low level console routines.
+ */
+int
+cngetc(void)
+{
+	int c;
+
+	if (cn_mute)
+		return (-1);
+	while ((c = cncheckc()) == -1)
+		;
+	if (c == '\r')
+		c = '\n';		/* console input is always ICRNL */
+	return (c);
+}
+
+int
+cncheckc(void)
+{
+	struct cn_device *cnd;
+	struct consdev *cn;
+	int c;
+
+	if (cn_mute)
+		return (-1);
+	STAILQ_FOREACH(cnd, &cn_devlist, cnd_next) {
+		cn = cnd->cnd_cn;
+		if (!kdb_active || !(cn->cn_flags & CN_FLAG_NODEBUG)) {
+			if (cn->cn_checkc != NULL)
+				c = cn->cn_checkc(cn);
+			else
+				c = cn->cn_getc(cn);
+			if (c != -1) {
+				return (c);
+			}
+		}
+	}
+	return (-1);
+}
+
+void
+cnputc(int c)
+{
+	struct cn_device *cnd;
+	struct consdev *cn;
+	char *cp;
+
+	if (cn_mute || c == '\0')
+		return;
+	STAILQ_FOREACH(cnd, &cn_devlist, cnd_next) {
+		cn = cnd->cnd_cn;
+		if (!kdb_active || !(cn->cn_flags & CN_FLAG_NODEBUG)) {
+			if (c == '\n')
+				cn->cn_putc(cn, '\r');
+			cn->cn_putc(cn, c);
+		}
+	}
+	if (console_pausing && c == '\n' && !kdb_active) {
+		for (cp = console_pausestr; *cp != '\0'; cp++)
+			cnputc(*cp);
+		if (cngetc() == '.')
+			console_pausing = 0;
+		cnputc('\r');
+		for (cp = console_pausestr; *cp != '\0'; cp++)
+			cnputc(' ');
+		cnputc('\r');
+	}
+}
+
+void
+cnputs(char *p)
+{
+	int c;
+	int unlock_reqd = 0;
+
+	if (use_cnputs_mtx) {
+		mtx_lock_spin(&cnputs_mtx);
+		unlock_reqd = 1;
+	}
+
+	while ((c = *p++) != '\0')
+		cnputc(c);
+
+	if (unlock_reqd)
+		mtx_unlock_spin(&cnputs_mtx);
+}
+
+static int consmsgbuf_size = 8192;
+SYSCTL_INT(_kern, OID_AUTO, consmsgbuf_size, CTLFLAG_RW, &consmsgbuf_size, 0,
+    "");
+
+/*
+ * Redirect console output to a tty.
+ */
+void
+constty_set(struct tty *tp)
+{
+	int size;
+
+	KASSERT(tp != NULL, ("constty_set: NULL tp"));
+	if (consbuf == NULL) {
+		size = consmsgbuf_size;
+		consbuf = malloc(size, M_TTYCONS, M_WAITOK);
+		msgbuf_init(&consmsgbuf, consbuf, size);
+		callout_init(&conscallout, 0);
+	}
+	constty = tp;
+	constty_timeout(NULL);
+}
+
+/*
+ * Disable console redirection to a tty.
+ */
+void
+constty_clear(void)
+{
+	int c;
+
+	constty = NULL;
+	if (consbuf == NULL)
+		return;
+	callout_stop(&conscallout);
+	while ((c = msgbuf_getchar(&consmsgbuf)) != -1)
+		cnputc(c);
+	free(consbuf, M_TTYCONS);
+	consbuf = NULL;
+}
+
+/* Times per second to check for pending console tty messages. */
+static int constty_wakeups_per_second = 5;
+SYSCTL_INT(_kern, OID_AUTO, constty_wakeups_per_second, CTLFLAG_RW,
+    &constty_wakeups_per_second, 0, "");
+
+static void
+constty_timeout(void *arg)
+{
+	int c;
+
+	if (constty != NULL) {
+		tty_lock(constty);
+		while ((c = msgbuf_getchar(&consmsgbuf)) != -1) {
+			if (tty_putchar(constty, c) < 0) {
+				tty_unlock(constty);
+				constty = NULL;
+				break;
+			}
+		}
+
+		if (constty != NULL)
+			tty_unlock(constty);
+	}
+	if (constty != NULL) {
+		callout_reset(&conscallout, hz / constty_wakeups_per_second,
+		    constty_timeout, NULL);
+	} else {
+		/* Deallocate the constty buffer memory. */
+		constty_clear();
+	}
+}
+
+static void
+cn_drvinit(void *unused)
+{
+
+	mtx_init(&cnputs_mtx, "cnputs_mtx", NULL, MTX_SPIN | MTX_NOWITNESS);
+	use_cnputs_mtx = 1;
+}
+
+SYSINIT(cndev, SI_SUB_DRIVERS, SI_ORDER_MIDDLE, cn_drvinit, NULL);
+
+/*
+ * Sysbeep(), if we have hardware for it
+ */
+
+#ifdef HAS_TIMER_SPKR
+
+static int beeping;
+
+static void
+sysbeepstop(void *chan)
+{
+
+	timer_spkr_release();
+	beeping = 0;
+}
+
+int
+sysbeep(int pitch, int period)
+{
+
+	if (timer_spkr_acquire()) {
+		if (!beeping) {
+			/* Something else owns it. */
+			return (EBUSY);
+		}
+	}
+	timer_spkr_setfreq(pitch);
+	if (!beeping) {
+		beeping = period;
+		timeout(sysbeepstop, (void *)NULL, period);
+	}
+	return (0);
+}
+
+#else
+
+/*
+ * No hardware, no sound
+ */
+
+int
+sysbeep(int pitch __unused, int period __unused)
+{
+
+	return (ENODEV);
+}
+
+#endif
+