Expand kdb_alt_break a little, most commonly used with the option

ALT_BREAK_TO_DEBUGGER.  In addition to "Enter ~ ctrl-B" (to enter the
debugger), there is now "Enter ~ ctrl-P" (force panic) and
"Enter ~ ctrl-R" (request clean reboot, ala ctrl-alt-del on syscons).

We've used variations of this at work.  The force panic sequence is
best used with KDB_UNATTENDED for when you just want it to dump and
get on with it.

The reboot request is a safer way of getting into single user than
a power cycle.  eg: you've hosed the ability to log in (pam, rtld, etc).
It gives init the reboot signal, which causes an orderly reboot.

I've taken my best guess at what the !x86 and non-sio code changes
should be.

This also makes sio release its spinlock before calling KDB/DDB.

9 files changed, 175 insertions, 37 deletions

diff --git a/sys/arm/at91/uart_dev_at91usart.c b/sys/arm/at91/uart_dev_at91usart.c
index f87dcaa..8a7644f 100644
--- a/sys/arm/at91/uart_dev_at91usart.c
+++ b/sys/arm/at91/uart_dev_at91usart.c
@@ -506,9 +506,20 @@ static __inline void
 at91_rx_put(struct uart_softc *sc, int key)
 {
 #if defined(KDB) && defined(ALT_BREAK_TO_DEBUGGER)
+	int kdb_brk;
+
 	if (sc->sc_sysdev != NULL && sc->sc_sysdev->type == UART_DEV_CONSOLE) {
-		if (kdb_alt_break(key, &sc->sc_altbrk))
-			kdb_enter(KDB_WHY_BREAK, "Break sequence to console");
+		if ((kdb_brk = kdb_alt_break(key, &sc->sc_altbrk)) != 0) {
+		case KDB_REQ_DEBUGGER:
+			kdb_enter(KDB_WHY_BREAK, "Break sequence on console");
+			break;
+		case KDB_REQ_PANIC:
+			kdb_panic("Panic sequence on console");
+			break;
+		case KDB_REQ_REBOOT:
+			kdb_reboot();
+			break;
+		}
 	}
 #endif
 	uart_rx_put(sc, key);	
diff --git a/sys/dev/dcons/dcons_os.c b/sys/dev/dcons/dcons_os.c
index 7eb89aa..5715343 100644
--- a/sys/dev/dcons/dcons_os.c
+++ b/sys/dev/dcons/dcons_os.c
@@ -198,22 +198,36 @@ extern struct gdb_dbgport *gdb_cur;
 static int
 dcons_check_break(struct dcons_softc *dc, int c)
 {
+#if __FreeBSD_version >= 502122
+	int kdb_brk;
+#endif
 	if (c < 0)
 		return (c);
 
 #if __FreeBSD_version >= 502122
-	if (kdb_alt_break(c, &dc->brk_state)) {
-		if ((dc->flags & DC_GDB) != 0) {
+	if ((kdb_brk = kdb_alt_break(c, &dc->brk_state)) != 0) {
+		switch (kdb_brk) {
+		case KDB_REQ_DEBUGGER:
+		
+			if ((dc->flags & DC_GDB) != 0) {
 #ifdef GDB
-			if (gdb_cur == &dcons_gdb_dbgport) {
-				kdb_dbbe_select("gdb");
-				kdb_enter(KDB_WHY_BREAK,
-				    "Break sequence on dcons gdb port");
-			}
+				if (gdb_cur == &dcons_gdb_dbgport) {
+					kdb_dbbe_select("gdb");
+					kdb_enter(KDB_WHY_BREAK,
+					    "Break sequence on dcons gdb port");
+				}
 #endif
-		} else
-			kdb_enter(KDB_WHY_BREAK,
-			    "Break sequence on dcons console port");
+			} else
+				kdb_enter(KDB_WHY_BREAK,
+				    "Break sequence on dcons console port");
+			break;
+		case KDB_REQ_PANIC:
+			kdb_panic("Panic sequence on dcons console port");
+			break;
+		case KDB_REQ_BREAK:
+			kdb_reboot();
+			break;
+		}
 	}
 #else
 	switch (dc->brk_state) {
diff --git a/sys/dev/ofw/ofw_console.c b/sys/dev/ofw/ofw_console.c
index 154bcc5..156f121 100644
--- a/sys/dev/ofw/ofw_console.c
+++ b/sys/dev/ofw/ofw_console.c
@@ -281,8 +281,23 @@ ofw_cngetc(struct consdev *cp)
 
 	if (OF_read(stdin, &ch, 1) > 0) {
 #if defined(KDB) && defined(ALT_BREAK_TO_DEBUGGER)
-		if (kdb_alt_break(ch, &alt_break_state))
-			kdb_enter(KDB_WHY_BREAK, "Break sequence on console");
+		int kdb_brk;
+
+		if ((kdb_brk = kdb_alt_break(ch, &alt_break_state)) != 0) {
+			switch (kdb_brk) {
+			case KDB_REQ_DEBUGGER:
+				kdb_enter(KDB_WHY_BREAK,
+				    "Break sequence on console");
+				break;
+			case KDB_REQ_PANIC:
+				kdb_panic("Panic sequence on console");
+				break;
+			case KDB_REQ_REBOOT:
+				kdb_reboot();
+				break;
+
+			}
+		}
 #endif
 		return (ch);
 	}
diff --git a/sys/dev/sio/sio.c b/sys/dev/sio/sio.c
index a62b411..a4cca4d 100644
--- a/sys/dev/sio/sio.c
+++ b/sys/dev/sio/sio.c
@@ -1469,6 +1469,11 @@ siointr1(com)
 	u_char	modem_status;
 	u_char	*ioptr;
 	u_char	recv_data;
+#if defined(KDB) && defined(ALT_BREAK_TO_DEBUGGER)
+	int	kdb_brk;
+
+again:
+#endif
 
 	if (COM_IIR_TXRDYBUG(com->flags)) {
 		int_ctl = inb(com->int_ctl_port);
@@ -1501,9 +1506,24 @@ siointr1(com)
 #ifdef KDB
 #ifdef ALT_BREAK_TO_DEBUGGER
 			if (com->unit == comconsole &&
-			    kdb_alt_break(recv_data, &com->alt_brk_state) != 0)
-				kdb_enter(KDB_WHY_BREAK,
-				    "Break sequence on console");
+			    (kdb_brk = kdb_alt_break(recv_data,
+					&com->alt_brk_state)) != 0) {
+				mtx_unlock_spin(&sio_lock);
+				switch (kdb_brk) {
+				case KDB_REQ_DEBUGGER:
+					kdb_enter(KDB_WHY_BREAK,
+					    "Break sequence on console");
+					break;
+				case KDB_REQ_PANIC:
+					kdb_panic("panic on console");
+					break;
+				case KDB_REQ_REBOOT:
+					kdb_reboot();
+					break;
+				}
+				mtx_lock_spin(&sio_lock);
+				goto again;
+			}
 #endif /* ALT_BREAK_TO_DEBUGGER */
 #endif /* KDB */
 			if (line_status & (LSR_BI | LSR_FE | LSR_PE)) {
diff --git a/sys/dev/uart/uart_core.c b/sys/dev/uart/uart_core.c
index b4730418..3b0d64c 100644
--- a/sys/dev/uart/uart_core.c
+++ b/sys/dev/uart/uart_core.c
@@ -175,9 +175,23 @@ uart_intr_rxready(void *arg)
 #if defined(KDB) && defined(ALT_BREAK_TO_DEBUGGER)
 	if (sc->sc_sysdev != NULL && sc->sc_sysdev->type == UART_DEV_CONSOLE) {
 		while (rxp != sc->sc_rxput) {
-			if (kdb_alt_break(sc->sc_rxbuf[rxp++], &sc->sc_altbrk))
-				kdb_enter(KDB_WHY_BREAK,
-				    "Break sequence on console");
+			int kdb_brk;
+
+			if ((kdb_brk = kdb_alt_break(sc->sc_rxbuf[rxp++],
+			    &sc->sc_altbrk)) != 0) {
+				switch (kdb_brk) {
+				case KDB_REQ_DEBUGGER:
+					kdb_enter(KDB_WHY_BREAK,
+					    "Break sequence on console");
+					break;
+				case KDB_REQ_PANIC:
+					kdb_panic("Panic sequence on console");
+					break;
+				case KDB_REQ_REBOOT:
+					kdb_reboot();
+					break;
+				}
+			}
 			if (rxp == sc->sc_rxbufsz)
 				rxp = 0;
 		}
diff --git a/sys/kern/subr_kdb.c b/sys/kern/subr_kdb.c
index 8b66a58..602093b 100644
--- a/sys/kern/subr_kdb.c
+++ b/sys/kern/subr_kdb.c
@@ -221,6 +221,25 @@ kdb_sysctl_trap_code(SYSCTL_HANDLER_ARGS)
 	return (0);
 }
 
+void
+kdb_panic(const char *msg)
+{
+	
+#ifdef SMP
+	stop_cpus(PCPU_GET(other_cpus));
+#endif
+	printf("KDB: panic\n");
+	panic(msg);
+}
+
+void
+kdb_reboot(void)
+{
+
+	printf("KDB: reboot requested\n");
+	shutdown_nice(0);
+}
+
 /*
  * Solaris implements a new BREAK which is initiated by a character sequence
  * CR ~ ^b which is similar to a familiar pattern used on Sun servers by the
@@ -235,6 +254,8 @@ kdb_sysctl_trap_code(SYSCTL_HANDLER_ARGS)
 #define	KEY_CR		13	/* CR '\r' */
 #define	KEY_TILDE	126	/* ~ */
 #define	KEY_CRTLB	2	/* ^B */
+#define	KEY_CRTLP	16	/* ^P */
+#define	KEY_CRTLR	18	/* ^R */
 
 int
 kdb_alt_break(int key, int *state)
@@ -242,20 +263,23 @@ kdb_alt_break(int key, int *state)
 	int brk;
 
 	brk = 0;
-	switch (key) {
-	case KEY_CR:
-		*state = KEY_TILDE;
+	switch (*state) {
+	case 0:
+		if (key == KEY_CR)
+			*state = 1;
 		break;
-	case KEY_TILDE:
-		*state = (*state == KEY_TILDE) ? KEY_CRTLB : 0;
+	case 1:
+		if (key == KEY_TILDE)
+			*state = 2;
 		break;
-	case KEY_CRTLB:
-		if (*state == KEY_CRTLB)
-			brk = 1;
-		/* FALLTHROUGH */
-	default:
+	case 2:
+		if (key == KEY_CRTLB)
+			brk = KDB_REQ_DEBUGGER;
+		else if (key == KEY_CRTLP)
+			brk = KDB_REQ_PANIC;
+		else if (key == KEY_CRTLR)
+			brk = KDB_REQ_REBOOT;
 		*state = 0;
-		break;
 	}
 	return (brk);
 }
diff --git a/sys/pc98/cbus/sio.c b/sys/pc98/cbus/sio.c
index d0173af..7089578 100644
--- a/sys/pc98/cbus/sio.c
+++ b/sys/pc98/cbus/sio.c
@@ -2268,12 +2268,16 @@ siointr1(com)
 	u_char	modem_status;
 	u_char	*ioptr;
 	u_char	recv_data;
-
 #ifdef PC98
 	u_char	tmp = 0;
 	u_char	rsa_buf_status = 0;
 	int	rsa_tx_fifo_size = 0;
 #endif /* PC98 */
+#if defined(KDB) && defined(ALT_BREAK_TO_DEBUGGER)
+	int	kdb_brk;
+
+again:
+#endif
 
 	if (COM_IIR_TXRDYBUG(com->flags)) {
 		int_ctl = inb(com->int_ctl_port);
@@ -2368,9 +2372,24 @@ more_intr:
 #ifdef KDB
 #ifdef ALT_BREAK_TO_DEBUGGER
 			if (com->unit == comconsole &&
-			    kdb_alt_break(recv_data, &com->alt_brk_state) != 0)
-				kdb_enter(KDB_WHY_BREAK,
-				    "Break sequence on console");
+			    (kdb_brk = kdb_alt_break(recv_data,
+					&com->alt_brk_state)) != 0) {
+				mtx_unlock_spin(&sio_lock);
+				switch (kdb_brk) {
+				case KDB_REQ_DEBUGGER:
+					kdb_enter(KDB_WHY_BREAK,
+					    "Break sequence on console");
+					break;
+				case KDB_REQ_PANIC:
+					kdb_panic("panic on console");
+					break;
+				case KDB_REQ_REBOOT:
+					kdb_reboot();
+					break;
+				}
+				mtx_lock_spin(&sio_lock);
+				goto again;
+			}
 #endif /* ALT_BREAK_TO_DEBUGGER */
 #endif /* KDB */
 			if (line_status & (LSR_BI | LSR_FE | LSR_PE)) {
diff --git a/sys/sun4v/sun4v/hvcons.c b/sys/sun4v/sun4v/hvcons.c
index 3329d05..0217a85 100644
--- a/sys/sun4v/sun4v/hvcons.c
+++ b/sys/sun4v/sun4v/hvcons.c
@@ -223,11 +223,25 @@ hvcn_cngetc(struct consdev *cp)
 
 	while ((l = hv_cons_getchar(&ch)) != H_EOK) {
 #if defined(KDB)
+		int kdb_brk;
+
 		if (l == H_BREAK || l ==  H_HUP)
 			kdb_enter(KDB_WHY_BREAK, "Break sequence on console");
 
-	if (kdb_alt_break(ch, &alt_break_state))
-		kdb_enter(KDB_WHY_BREAK, "Break sequence on console");
+		if ((kdb_brk = kdb_alt_break(ch, &alt_break_state)) != 0) {
+			switch (kdb_brk) {
+			case KDB_REQ_DEBUGGER:
+				kdb_enter(KDB_WHY_BREAK,
+				    "Break sequence on console");
+				break;
+			case KDB_REQ_PANIC:
+				kdb_panic("Panic sequence on console");
+				break;
+			case KDB_REQ_REBOOT:
+				kdb_reboot();
+				break;
+			}
+		}
 #endif
 		if (l != -2 && l != 0) {
 			return (-1);
diff --git a/sys/sys/kdb.h b/sys/sys/kdb.h
index 0f989f5..c162852 100644
--- a/sys/sys/kdb.h
+++ b/sys/sys/kdb.h
@@ -69,6 +69,8 @@ int	kdb_dbbe_select(const char *);
 void	kdb_enter(const char *, const char *);
 void	kdb_init(void);
 void *	kdb_jmpbuf(jmp_buf);
+void	kdb_panic(const char *);
+void	kdb_reboot(void);
 void	kdb_reenter(void);
 struct pcb *kdb_thr_ctx(struct thread *);
 struct thread *kdb_thr_first(void);
@@ -105,4 +107,9 @@ extern const char * volatile kdb_why;
 #define	KDB_WHY_POWERPC		"powerpc"	/* Unhandled powerpc intr. */
 #define	KDB_WHY_UNIONFS		"unionfs"	/* Unionfs bug. */
 
+/* Return values for kdb_alt_break */
+#define	KDB_REQ_DEBUGGER	1	/* User requested Debugger */
+#define	KDB_REQ_PANIC		2	/* User requested a panic */
+#define	KDB_REQ_REBOOT		3	/* User requested a clean reboot */
+
 #endif /* !_SYS_KDB_H_ */