Add a new 'why' argument to kdb_enter(), and a set of constants to use

for that argument.  This will allow DDB to detect the broad category of
reason why the debugger has been entered, which it can use for the
purposes of deciding which DDB script to run.

Assign approximate why values to all current consumers of the
kdb_enter() interface.

33 files changed, 95 insertions, 48 deletions

diff --git a/sys/amd64/amd64/machdep.c b/sys/amd64/amd64/machdep.c
index 24226f7..24e9ec8 100644
--- a/sys/amd64/amd64/machdep.c
+++ b/sys/amd64/amd64/machdep.c
@@ -1277,7 +1277,8 @@ hammer_time(u_int64_t modulep, u_int64_t physfree)
 
 #ifdef KDB
 	if (boothowto & RB_KDB)
-		kdb_enter("Boot flags requested debugger");
+		kdb_enter(KDB_WHY_BOOTFLAGS,
+		    "Boot flags requested debugger");
 #endif
 
 	identify_cpu();		/* Final stage of CPU initialization */
diff --git a/sys/amd64/amd64/mp_watchdog.c b/sys/amd64/amd64/mp_watchdog.c
index b6ac777..1803270 100644
--- a/sys/amd64/amd64/mp_watchdog.c
+++ b/sys/amd64/amd64/mp_watchdog.c
@@ -203,7 +203,7 @@ ap_watchdog(u_int cpuid)
 			if (watchdog_nmi)
 				watchdog_ipi_nmi();
 			else
-				kdb_enter("mp_watchdog");
+				kdb_enter(KDB_WHY_WATCHDOG, "mp_watchdog");
 		}
 	}
 	bcopy(old_pcomm, p->p_comm, MAXCOMLEN + 1);
diff --git a/sys/arm/at91/uart_dev_at91usart.c b/sys/arm/at91/uart_dev_at91usart.c
index 8862589..f87dcaa 100644
--- a/sys/arm/at91/uart_dev_at91usart.c
+++ b/sys/arm/at91/uart_dev_at91usart.c
@@ -508,7 +508,7 @@ at91_rx_put(struct uart_softc *sc, int key)
 #if defined(KDB) && defined(ALT_BREAK_TO_DEBUGGER)
 	if (sc->sc_sysdev != NULL && sc->sc_sysdev->type == UART_DEV_CONSOLE) {
 		if (kdb_alt_break(key, &sc->sc_altbrk))
-			kdb_enter("Break sequence to console");
+			kdb_enter(KDB_WHY_BREAK, "Break sequence to console");
 	}
 #endif
 	uart_rx_put(sc, key);	
diff --git a/sys/cam/scsi/scsi_low.h b/sys/cam/scsi/scsi_low.h
index 4dfa602..8d6dbed 100644
--- a/sys/cam/scsi/scsi_low.h
+++ b/sys/cam/scsi/scsi_low.h
@@ -87,7 +87,7 @@
 
 #ifdef	__FreeBSD__
 #undef	MSG_IDENTIFY
-#define	SCSI_LOW_DEBUGGER(dev)	kdb_enter(dev)
+#define	SCSI_LOW_DEBUGGER(dev)	kdb_enter(KDB_WHY_CAM, dev)
 #define	SCSI_LOW_DELAY(mu)	DELAY((mu))
 #define	SCSI_LOW_SPLSCSI	splcam
 #define	SCSI_LOW_BZERO(pt, size)	bzero((pt), (size))
diff --git a/sys/compat/ndis/subr_ntoskrnl.c b/sys/compat/ndis/subr_ntoskrnl.c
index 367d9f6..dd76d25 100644
--- a/sys/compat/ndis/subr_ntoskrnl.c
+++ b/sys/compat/ndis/subr_ntoskrnl.c
@@ -3632,7 +3632,7 @@ DbgBreakPoint(void)
 #if __FreeBSD_version < 502113
 	Debugger("DbgBreakPoint(): breakpoint");
 #else
-	kdb_enter("DbgBreakPoint(): breakpoint");
+	kdb_enter(KDB_WHY_NDIS, "DbgBreakPoint(): breakpoint");
 #endif
 }
 
diff --git a/sys/dev/acpica/Osd/OsdDebug.c b/sys/dev/acpica/Osd/OsdDebug.c
index b127181..27b94a0 100644
--- a/sys/dev/acpica/Osd/OsdDebug.c
+++ b/sys/dev/acpica/Osd/OsdDebug.c
@@ -73,13 +73,13 @@ AcpiOsSignal(UINT32 Function, void *Info)
 	printf("ACPI fatal signal, type 0x%x code 0x%x argument 0x%x",
 	      fatal->Type, fatal->Code, fatal->Argument);
 #ifdef ACPI_DEBUG
-	kdb_enter("AcpiOsSignal");
+	kdb_enter(KDB_WHY_ACPI, "AcpiOsSignal");
 #endif
 	break;
 
     case ACPI_SIGNAL_BREAKPOINT:
 #ifdef ACPI_DEBUG
-	kdb_enter((char *)Info);
+	kdb_enter(KDB_WHY_ACPI, (char *)Info);
 #endif
 	break;
 
diff --git a/sys/dev/dcons/dcons_os.c b/sys/dev/dcons/dcons_os.c
index d47515c..7eb89aa 100644
--- a/sys/dev/dcons/dcons_os.c
+++ b/sys/dev/dcons/dcons_os.c
@@ -207,11 +207,13 @@ dcons_check_break(struct dcons_softc *dc, int c)
 #ifdef GDB
 			if (gdb_cur == &dcons_gdb_dbgport) {
 				kdb_dbbe_select("gdb");
-				kdb_enter("Break sequence on dcons gdb port");
+				kdb_enter(KDB_WHY_BREAK,
+				    "Break sequence on dcons gdb port");
 			}
 #endif
 		} else
-			kdb_enter("Break sequence on dcons console port");
+			kdb_enter(KDB_WHY_BREAK,
+			    "Break sequence on dcons console port");
 	}
 #else
 	switch (dc->brk_state) {
diff --git a/sys/dev/ofw/ofw_console.c b/sys/dev/ofw/ofw_console.c
index 0d1133f..7d6f5eb 100644
--- a/sys/dev/ofw/ofw_console.c
+++ b/sys/dev/ofw/ofw_console.c
@@ -282,7 +282,7 @@ 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("Break sequence on console");
+			kdb_enter(KDB_WHY_BREAK, "Break sequence on console");
 #endif
 		return (ch);
 	}
diff --git a/sys/dev/sio/sio.c b/sys/dev/sio/sio.c
index 3db7f59..a62b411 100644
--- a/sys/dev/sio/sio.c
+++ b/sys/dev/sio/sio.c
@@ -1502,7 +1502,8 @@ siointr1(com)
 #ifdef ALT_BREAK_TO_DEBUGGER
 			if (com->unit == comconsole &&
 			    kdb_alt_break(recv_data, &com->alt_brk_state) != 0)
-				kdb_enter("Break sequence on console");
+				kdb_enter(KDB_WHY_BREAK,
+				    "Break sequence on console");
 #endif /* ALT_BREAK_TO_DEBUGGER */
 #endif /* KDB */
 			if (line_status & (LSR_BI | LSR_FE | LSR_PE)) {
@@ -1521,7 +1522,8 @@ siointr1(com)
 				if (line_status & LSR_BI) {
 #if defined(KDB) && defined(BREAK_TO_DEBUGGER)
 					if (com->unit == comconsole) {
-						kdb_enter("Line break on console");
+						kdb_enter(KDB_WHY_BREAK,
+						    "Line break on console");
 						goto cont;
 					}
 #endif
diff --git a/sys/dev/syscons/syscons.c b/sys/dev/syscons/syscons.c
index 04ad041..b749895 100644
--- a/sys/dev/syscons/syscons.c
+++ b/sys/dev/syscons/syscons.c
@@ -3373,7 +3373,7 @@ next_code:
 	    case DBG:
 #ifndef SC_DISABLE_KDBKEY
 		if (enable_kdbkey)
-			kdb_enter("manual escape to debugger");
+			kdb_enter(KDB_WHY_BREAK, "manual escape to debugger");
 #endif
 		break;
 
diff --git a/sys/dev/uart/uart_core.c b/sys/dev/uart/uart_core.c
index f991278..b4730418 100644
--- a/sys/dev/uart/uart_core.c
+++ b/sys/dev/uart/uart_core.c
@@ -122,7 +122,7 @@ uart_intr_break(void *arg)
 
 #if defined(KDB) && defined(BREAK_TO_DEBUGGER)
 	if (sc->sc_sysdev != NULL && sc->sc_sysdev->type == UART_DEV_CONSOLE) {
-		kdb_enter("Line break on console");
+		kdb_enter(KDB_WHY_BREAK, "Line break on console");
 		return (0);
 	}
 #endif
@@ -176,7 +176,8 @@ uart_intr_rxready(void *arg)
 	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("Break sequence on console");
+				kdb_enter(KDB_WHY_BREAK,
+				    "Break sequence on console");
 			if (rxp == sc->sc_rxbufsz)
 				rxp = 0;
 		}
diff --git a/sys/fs/unionfs/union_subr.c b/sys/fs/unionfs/union_subr.c
index 05dd077..4ff6308 100644
--- a/sys/fs/unionfs/union_subr.c
+++ b/sys/fs/unionfs/union_subr.c
@@ -1062,7 +1062,8 @@ unionfs_checkuppervp(struct vnode *vp, char *fil, int lno)
 	if (vp->v_op != unionfs_vnodeop_p) {
 		printf("unionfs_checkuppervp: on non-unionfs-node.\n");
 #ifdef KDB
-		kdb_enter("unionfs_checkuppervp: on non-unionfs-node.\n");
+		kdb_enter(KDB_WHY_UNIONFS,
+		    "unionfs_checkuppervp: on non-unionfs-node.\n");
 #endif
 		panic("unionfs_checkuppervp");
 	};
@@ -1081,7 +1082,8 @@ unionfs_checklowervp(struct vnode *vp, char *fil, int lno)
 	if (vp->v_op != unionfs_vnodeop_p) {
 		printf("unionfs_checklowervp: on non-unionfs-node.\n");
 #ifdef KDB
-		kdb_enter("unionfs_checklowervp: on non-unionfs-node.\n");
+		kdb_enter(KDB_WHY_UNIONFS,
+		    "unionfs_checklowervp: on non-unionfs-node.\n");
 #endif
 		panic("unionfs_checklowervp");
 	};
diff --git a/sys/i386/i386/machdep.c b/sys/i386/i386/machdep.c
index 01fbf1c..202e2a9 100644
--- a/sys/i386/i386/machdep.c
+++ b/sys/i386/i386/machdep.c
@@ -2275,7 +2275,7 @@ init386(first)
 
 #ifdef KDB
 	if (boothowto & RB_KDB)
-		kdb_enter("Boot flags requested debugger");
+		kdb_enter(KDB_WHY_BOOTFLAGS, "Boot flags requested debugger");
 #endif
 
 	finishidentcpu();	/* Final stage of CPU initialization */
diff --git a/sys/i386/i386/mp_watchdog.c b/sys/i386/i386/mp_watchdog.c
index b6ac777..1803270 100644
--- a/sys/i386/i386/mp_watchdog.c
+++ b/sys/i386/i386/mp_watchdog.c
@@ -203,7 +203,7 @@ ap_watchdog(u_int cpuid)
 			if (watchdog_nmi)
 				watchdog_ipi_nmi();
 			else
-				kdb_enter("mp_watchdog");
+				kdb_enter(KDB_WHY_WATCHDOG, "mp_watchdog");
 		}
 	}
 	bcopy(old_pcomm, p->p_comm, MAXCOMLEN + 1);
diff --git a/sys/ia64/ia64/machdep.c b/sys/ia64/ia64/machdep.c
index 3c44b2e..e6e5d7f 100644
--- a/sys/ia64/ia64/machdep.c
+++ b/sys/ia64/ia64/machdep.c
@@ -824,7 +824,8 @@ ia64_init(void)
 
 #ifdef KDB
 	if (boothowto & RB_KDB)
-		kdb_enter("Boot flags requested debugger\n");
+		kdb_enter(KDB_WHY_BOOTFLAGS,
+		    "Boot flags requested debugger\n");
 #endif
 
 	ia64_set_tpr(0);
diff --git a/sys/kern/kern_clock.c b/sys/kern/kern_clock.c
index 217e2ef..fb0ca7e 100644
--- a/sys/kern/kern_clock.c
+++ b/sys/kern/kern_clock.c
@@ -637,7 +637,7 @@ watchdog_fire(void)
 
 #if defined(KDB) && !defined(KDB_UNATTENDED)
 	kdb_backtrace();
-	kdb_enter("watchdog timeout");
+	kdb_enter(KDB_WHY_WATCHDOG, "watchdog timeout");
 #else
 	panic("watchdog timeout");
 #endif
diff --git a/sys/kern/kern_shutdown.c b/sys/kern/kern_shutdown.c
index 088e781..baeed23 100644
--- a/sys/kern/kern_shutdown.c
+++ b/sys/kern/kern_shutdown.c
@@ -544,7 +544,7 @@ panic(const char *fmt, ...)
 	if (newpanic && trace_on_panic)
 		kdb_backtrace();
 	if (debugger_on_panic)
-		kdb_enter("panic");
+		kdb_enter(KDB_WHY_PANIC, "panic");
 #ifdef RESTARTABLE_PANICS
 	/* See if the user aborted the panic, in which case we continue. */
 	if (panicstr == NULL) {
diff --git a/sys/kern/subr_kdb.c b/sys/kern/subr_kdb.c
index 0ab79fb..8b66a58 100644
--- a/sys/kern/subr_kdb.c
+++ b/sys/kern/subr_kdb.c
@@ -97,6 +97,11 @@ SYSCTL_INT(_debug_kdb, OID_AUTO, stop_cpus, CTLTYPE_INT | CTLFLAG_RW,
 TUNABLE_INT("debug.kdb.stop_cpus", &kdb_stop_cpus);
 #endif
 
+/*
+ * Flag to indicate to debuggers why the debugger was entered.
+ */
+const char * volatile kdb_why = KDB_WHY_UNSET;
+
 static int
 kdb_sysctl_available(SYSCTL_HANDLER_ARGS)
 {
@@ -163,7 +168,7 @@ kdb_sysctl_enter(SYSCTL_HANDLER_ARGS)
 		return (error);
 	if (kdb_active)
 		return (EBUSY);
-	kdb_enter("sysctl debug.kdb.enter");
+	kdb_enter(KDB_WHY_SYSCTL, "sysctl debug.kdb.enter");
 	return (0);
 }
 
@@ -295,17 +300,20 @@ kdb_dbbe_select(const char *name)
  * Enter the currently selected debugger. If a message has been provided,
  * it is printed first. If the debugger does not support the enter method,
  * it is entered by using breakpoint(), which enters the debugger through
- * kdb_trap().
+ * kdb_trap().  The 'why' argument will contain a more mechanically usable
+ * string than 'msg', and is relied upon by DDB scripting to identify the
+ * reason for entering the debugger so that the right script can be run.
  */
-
 void
-kdb_enter(const char *msg)
+kdb_enter(const char *why, const char *msg)
 {
 
 	if (kdb_dbbe != NULL && kdb_active == 0) {
 		if (msg != NULL)
 			printf("KDB: enter: %s\n", msg);
+		kdb_why = why;
 		breakpoint();
+		kdb_why = KDB_WHY_UNSET;
 	}
 }
 
diff --git a/sys/kern/subr_witness.c b/sys/kern/subr_witness.c
index 3019a7a..c5402c7 100644
--- a/sys/kern/subr_witness.c
+++ b/sys/kern/subr_witness.c
@@ -1123,7 +1123,7 @@ debugger:
 	if (witness_trace)
 		kdb_backtrace();
 	if (witness_kdb)
-		kdb_enter(__func__);
+		kdb_enter(KDB_WHY_WITNESS, __func__);
 #endif
 }
 
@@ -1396,7 +1396,7 @@ witness_warn(int flags, struct lock_object *lock, const char *fmt, ...)
 		panic("witness_warn");
 #ifdef KDB
 	else if (witness_kdb && n)
-		kdb_enter(__func__);
+		kdb_enter(KDB_WHY_WITNESS, __func__);
 	else if (witness_trace && n)
 		kdb_backtrace();
 #endif
diff --git a/sys/kern/vfs_subr.c b/sys/kern/vfs_subr.c
index 0e3a0ac..e912006 100644
--- a/sys/kern/vfs_subr.c
+++ b/sys/kern/vfs_subr.c
@@ -3456,7 +3456,7 @@ vfs_badlock(const char *msg, const char *str, struct vnode *vp)
 	if (vfs_badlock_print)
 		printf("%s: %p %s\n", str, (void *)vp, msg);
 	if (vfs_badlock_ddb)
-		kdb_enter("lock violation");
+		kdb_enter(KDB_WHY_VFSLOCK, "lock violation");
 }
 
 void
@@ -3576,7 +3576,7 @@ vop_strategy_pre(void *ap)
 			printf(
 			    "VOP_STRATEGY: bp is not locked but should be\n");
 		if (vfs_badlock_ddb)
-			kdb_enter("lock violation");
+			kdb_enter(KDB_WHY_VFSLOCK, "lock violation");
 	}
 #endif
 }
diff --git a/sys/netgraph/ng_base.c b/sys/netgraph/ng_base.c
index ad0bec6..47fde60 100644
--- a/sys/netgraph/ng_base.c
+++ b/sys/netgraph/ng_base.c
@@ -3465,12 +3465,12 @@ ng_setisr(node_p node)
 	do {								\
 		if (NGI_NODE(item) ) {					\
 			printf("item already has node");		\
-			kdb_enter("has node");				\
+			kdb_enter(KDB_WHY_NETGRAPH, "has node");	\
 			NGI_CLR_NODE(item);				\
 		}							\
 		if (NGI_HOOK(item) ) {					\
 			printf("item already has hook");		\
-			kdb_enter("has hook");				\
+			kdb_enter(KDB_WHY_NETGRAPH, "has hook");	\
 			NGI_CLR_HOOK(item);				\
 		}							\
 	} while (0)
diff --git a/sys/pc98/cbus/sio.c b/sys/pc98/cbus/sio.c
index 648cb04..6533a53 100644
--- a/sys/pc98/cbus/sio.c
+++ b/sys/pc98/cbus/sio.c
@@ -2369,7 +2369,8 @@ more_intr:
 #ifdef ALT_BREAK_TO_DEBUGGER
 			if (com->unit == comconsole &&
 			    kdb_alt_break(recv_data, &com->alt_brk_state) != 0)
-				kdb_enter("Break sequence on console");
+				kdb_enter(KDB_WHY_BREAK,
+				    "Break sequence on console");
 #endif /* ALT_BREAK_TO_DEBUGGER */
 #endif /* KDB */
 			if (line_status & (LSR_BI | LSR_FE | LSR_PE)) {
@@ -2388,7 +2389,8 @@ more_intr:
 				if (line_status & LSR_BI) {
 #if defined(KDB) && defined(BREAK_TO_DEBUGGER)
 					if (com->unit == comconsole) {
-						kdb_enter("Line break on console");
+						kdb_enter(KDB_WHY_BREAK,
+						    "Line break on console");
 						goto cont;
 					}
 #endif
diff --git a/sys/pc98/pc98/machdep.c b/sys/pc98/pc98/machdep.c
index 1472af0..62d313f 100644
--- a/sys/pc98/pc98/machdep.c
+++ b/sys/pc98/pc98/machdep.c
@@ -2061,7 +2061,7 @@ init386(first)
 
 #ifdef KDB
 	if (boothowto & RB_KDB)
-		kdb_enter("Boot flags requested debugger");
+		kdb_enter(KDB_WHY_BOOTFLAGS, "Boot flags requested debugger");
 #endif
 
 	finishidentcpu();	/* Final stage of CPU initialization */
diff --git a/sys/powerpc/aim/machdep.c b/sys/powerpc/aim/machdep.c
index 7cea2c0..16da70e 100644
--- a/sys/powerpc/aim/machdep.c
+++ b/sys/powerpc/aim/machdep.c
@@ -398,7 +398,8 @@ powerpc_init(u_int startkernel, u_int endkernel, u_int basekernel, void *mdp)
 
 #ifdef KDB
 	if (boothowto & RB_KDB)
-		kdb_enter("Boot flags requested debugger");
+		kdb_enter(KDB_WHY_BOOTFLAGS,
+		    "Boot flags requested debugger");
 #endif
 }
 
diff --git a/sys/powerpc/powermac/pswitch.c b/sys/powerpc/powermac/pswitch.c
index 62777eb..c437392 100644
--- a/sys/powerpc/powermac/pswitch.c
+++ b/sys/powerpc/powermac/pswitch.c
@@ -139,6 +139,6 @@ pswitch_intr(void *arg)
 
 	dev = (device_t)arg;
 
-	kdb_enter(device_get_nameunit(dev));
+	kdb_enter(KDB_WHY_POWERPC, device_get_nameunit(dev));
 	return (FILTER_HANDLED);
 }
diff --git a/sys/security/mac_test/mac_test.c b/sys/security/mac_test/mac_test.c
index 32042e6..e28e4c3 100644
--- a/sys/security/mac_test/mac_test.c
+++ b/sys/security/mac_test/mac_test.c
@@ -117,7 +117,7 @@ SYSCTL_NODE(_security_mac_test, OID_AUTO, counter, CTLFLAG_RW, 0,
 #define	COUNTER_INC(variable)	atomic_add_int(&counter_##variable, 1)
 
 #ifdef KDB
-#define	DEBUGGER(func, string)	kdb_enter((string))
+#define	DEBUGGER(func, string)	kdb_enter(KDB_WHY_MAC, (string))
 #else
 #define	DEBUGGER(func, string)	printf("mac_test: %s: %s\n", (func), (string))
 #endif
diff --git a/sys/sparc64/pci/psycho.c b/sys/sparc64/pci/psycho.c
index 9f5632f..846afdd 100644
--- a/sys/sparc64/pci/psycho.c
+++ b/sys/sparc64/pci/psycho.c
@@ -850,7 +850,7 @@ psycho_powerfail(void *arg)
 #ifdef DEBUGGER_ON_POWERFAIL
 	struct psycho_softc *sc = arg;
 
-	kdb_enter("powerfail");
+	kdb_enter(KDB_WHY_POWERFAIL, "powerfail");
 #else
 	static int shutdown;
 
diff --git a/sys/sparc64/sparc64/machdep.c b/sys/sparc64/sparc64/machdep.c
index 2e6d05e..7d1aa02 100644
--- a/sys/sparc64/sparc64/machdep.c
+++ b/sys/sparc64/sparc64/machdep.c
@@ -448,7 +448,7 @@ sparc64_init(caddr_t mdp, u_long o1, u_long o2, u_long o3, ofw_vec_t *vec)
 
 #ifdef KDB
 	if (boothowto & RB_KDB)
-		kdb_enter("Boot flags requested debugger");
+		kdb_enter(KDB_WHY_BOOTFLAGS, "Boot flags requested debugger");
 #endif
 }
 
diff --git a/sys/sparc64/sparc64/trap.c b/sys/sparc64/sparc64/trap.c
index 8d0ea35..e9e3c40 100644
--- a/sys/sparc64/sparc64/trap.c
+++ b/sys/sparc64/sparc64/trap.c
@@ -289,7 +289,7 @@ trap(struct trapframe *tf)
 			}
 			if (debugger_on_signal &&
 			    (sig == 4 || sig == 10 || sig == 11))
-				kdb_enter("trapsig");
+				kdb_enter(KDB_WHY_TRAPSIG, "trapsig");
 			ksiginfo_init_trap(&ksi);
 			ksi.ksi_signo = sig;
 			ksi.ksi_code = (int)tf->tf_type; /* XXX not POSIX */
diff --git a/sys/sun4v/sun4v/hvcons.c b/sys/sun4v/sun4v/hvcons.c
index 201b22c..3329d05 100644
--- a/sys/sun4v/sun4v/hvcons.c
+++ b/sys/sun4v/sun4v/hvcons.c
@@ -224,10 +224,10 @@ hvcn_cngetc(struct consdev *cp)
 	while ((l = hv_cons_getchar(&ch)) != H_EOK) {
 #if defined(KDB)
 		if (l == H_BREAK || l ==  H_HUP)
-			kdb_enter("Break sequence on console");
+			kdb_enter(KDB_WHY_BREAK, "Break sequence on console");
 
 	if (kdb_alt_break(ch, &alt_break_state))
-		kdb_enter("Break sequence on console");
+		kdb_enter(KDB_WHY_BREAK, "Break sequence on console");
 #endif
 		if (l != -2 && l != 0) {
 			return (-1);
@@ -248,9 +248,9 @@ hvcn_cncheckc(struct consdev *cp)
 	if ((l = hv_cons_getchar(&ch)) == H_EOK) {
 #if defined(KDB)
 		if (l == H_BREAK || l ==  H_HUP)
-			kdb_enter("Break sequence on console");
+			kdb_enter(KDB_WHY_BREAK, "Break sequence on console");
 		if (kdb_alt_break(ch, &alt_break_state))
-			kdb_enter("Break sequence on console");
+			kdb_enter(KDB_WHY_BREAK, "Break sequence on console");
 #endif
 		return (ch);
 	}
diff --git a/sys/sun4v/sun4v/machdep.c b/sys/sun4v/sun4v/machdep.c
index 16a508a..1d0bf66 100644
--- a/sys/sun4v/sun4v/machdep.c
+++ b/sys/sun4v/sun4v/machdep.c
@@ -510,7 +510,7 @@ sparc64_init(caddr_t mdp, u_long o1, u_long o2, u_long o3, ofw_vec_t *vec)
 
 #ifdef KDB
 	if (boothowto & RB_KDB)
-		kdb_enter("Boot flags requested debugger");
+		kdb_enter(KDB_WHY_BOOTFLAGS, "Boot flags requested debugger");
 #endif
 	BVPRINTF("sparc64_init done\n");
 }
diff --git a/sys/sun4v/sun4v/trap.c b/sys/sun4v/sun4v/trap.c
index 75d5ce0..f04c424 100644
--- a/sys/sun4v/sun4v/trap.c
+++ b/sys/sun4v/sun4v/trap.c
@@ -366,7 +366,7 @@ trap(struct trapframe *tf, int64_t type, uint64_t data)
 			}
 			if (debugger_on_signal &&
 			    (sig == 4 || sig == 10 || sig == 11))
-				kdb_enter("trapsig");
+				kdb_enter(KDB_WHY_TRAPSIG, "trapsig");
 #ifdef VERBOSE
 			if (sig == 4 || sig == 10 || sig == 11)
 				printf("trap: %ld:%s: 0x%lx at 0x%lx on cpu=%d sig=%d proc=%s\n", 
diff --git a/sys/sys/kdb.h b/sys/sys/kdb.h
index ece16fc..0f989f5 100644
--- a/sys/sys/kdb.h
+++ b/sys/sys/kdb.h
@@ -66,7 +66,7 @@ extern struct thread *kdb_thread;	/* Current thread. */
 int	kdb_alt_break(int, int *);
 void	kdb_backtrace(void);
 int	kdb_dbbe_select(const char *);
-void	kdb_enter(const char *);
+void	kdb_enter(const char *, const char *);
 void	kdb_init(void);
 void *	kdb_jmpbuf(jmp_buf);
 void	kdb_reenter(void);
@@ -78,4 +78,31 @@ struct thread *kdb_thr_next(struct thread *);
 int	kdb_thr_select(struct thread *);
 int	kdb_trap(int, int, struct trapframe *);
 
+/*
+ * KDB enters the debugger via breakpoint(), which leaves the debugger without
+ * a lot of information about why it was entered.  This simple enumerated set
+ * captures some basic information.
+ *
+ * It is recommended that values here be short (<16 character) alpha-numeric
+ * strings, as they will be used to construct DDB(4) script names.
+ */
+extern const char * volatile kdb_why;
+#define	KDB_WHY_UNSET		NULL		/* No reason set. */
+#define	KDB_WHY_PANIC		"panic"		/* panic() was called. */
+#define	KDB_WHY_SYSCTL		"sysctl"	/* Sysctl entered debugger. */
+#define	KDB_WHY_BOOTFLAGS	"bootflags"	/* Boot flags were set. */
+#define	KDB_WHY_WITNESS		"witness"	/* Witness entered debugger. */
+#define	KDB_WHY_VFSLOCK		"vfslock"	/* VFS detected lock problem. */
+#define	KDB_WHY_NETGRAPH	"netgraph"	/* Netgraph entered debugger. */
+#define	KDB_WHY_BREAK		"break"		/* Console or serial break. */
+#define	KDB_WHY_WATCHDOG	"watchdog"	/* Watchdog entered debugger. */
+#define	KDB_WHY_CAM		"cam"		/* CAM has entered debugger. */
+#define	KDB_WHY_NDIS		"ndis"		/* NDIS entered debugger. */
+#define	KDB_WHY_ACPI		"acpi"		/* ACPI entered debugger. */
+#define	KDB_WHY_TRAPSIG		"trapsig"	/* Sun4v/Sparc fault. */
+#define	KDB_WHY_POWERFAIL	"powerfail"	/* Powerfail NMI. */
+#define	KDB_WHY_MAC		"mac"		/* MAC Framework. */
+#define	KDB_WHY_POWERPC		"powerpc"	/* Unhandled powerpc intr. */
+#define	KDB_WHY_UNIONFS		"unionfs"	/* Unionfs bug. */
+
 #endif /* !_SYS_KDB_H_ */