Modify kdb_trap() so that it re-calls the dbbe_trap function as long as

the debugger back-end has changed.  This means that switching from ddb
to gdb no longer requires a "step" which can be dangerous on an
already-crashed kernel.

Also add a capability to get from the gdb back-end back to ddb, by
typing ^C in the console window.

While here, simplify kdb_sysctl_available() by using
sbuf_new_for_sysctl(), and use strlcpy() instead of strncpy() since the
strlcpy semantic is desired.

MFC after:	1 month

1 files changed, 12 insertions, 0 deletions

diff --git a/sys/gdb/gdb_packet.c b/sys/gdb/gdb_packet.c
index d3e5a0a..a62cc8d 100644
--- a/sys/gdb/gdb_packet.c
+++ b/sys/gdb/gdb_packet.c
@@ -31,6 +31,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/systm.h>
 #include <sys/ctype.h>
 #include <sys/kdb.h>
+#include <sys/ttydefaults.h>
 
 #include <machine/gdb_machdep.h>
 #include <machine/kdb.h>
@@ -60,6 +61,17 @@ gdb_getc(void)
 	do
 		c = gdb_cur->gdb_getc();
 	while (c == -1);
+
+	if (c == CTRL('C')) {
+		printf("Received ^C; trying to switch back to ddb.\n");
+
+		if (kdb_dbbe_select("ddb") != 0)
+			printf("The ddb backend could not be selected.\n");
+		else {
+			printf("using longjmp, hope it works!\n");
+			kdb_reenter();
+		}
+	}
 	return (c);
 }