sys/kern/subr_kdb.c:

	Modify the "alternate break sequence" detecting state
	machine so that only a contiguous invocation of the
	break sequence is accepted.  The old implementation
	did not reset the state machine when detecting an
	unexpected character.

	While here, use an enum for the states of the machine
	instead of magic numbers.bmitted by:

Sponsored by:	Spectra Logic Corporation

1 files changed, 23 insertions, 8 deletions

diff --git a/sys/kern/subr_kdb.c b/sys/kern/subr_kdb.c
index 1d67864b1533..c2f6e99531d0 100644
--- a/sys/kern/subr_kdb.c
+++ b/sys/kern/subr_kdb.c
@@ -244,29 +244,44 @@ kdb_reboot(void)
 #define	KEY_CRTLP	16	/* ^P */
 #define	KEY_CRTLR	18	/* ^R */
 
+/* States of th KDB "alternate break sequence" detecting state machine. */
+enum {
+	KDB_ALT_BREAK_SEEN_NONE,
+	KDB_ALT_BREAK_SEEN_CR,
+	KDB_ALT_BREAK_SEEN_CR_TILDE,
+};
+
 int
 kdb_alt_break(int key, int *state)
 {
 	int brk;
 
+	/* All states transition to KDB_ALT_BREAK_SEEN_CR on a CR. */
+	if (key == KEY_CR) {
+		*state = KDB_ALT_BREAK_SEEN_CR;
+		return (0);
+	}
+
 	brk = 0;
 	switch (*state) {
-	case 0:
-		if (key == KEY_CR)
-			*state = 1;
-		break;
-	case 1:
+	case KDB_ALT_BREAK_SEEN_CR:
+		*state = KDB_ALT_BREAK_SEEN_NONE;
 		if (key == KEY_TILDE)
-			*state = 2;
+			*state = KDB_ALT_BREAK_SEEN_CR_TILDE;
 		break;
-	case 2:
+	case KDB_ALT_BREAK_SEEN_CR_TILDE:
+		*state = KDB_ALT_BREAK_SEEN_NONE;
 		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;
+	case KDB_ALT_BREAK_SEEN_NONE:
+	default:
+		*state = KDB_ALT_BREAK_SEEN_NONE;
+		break;
 	}
 	return (brk);
 }