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.

1 files changed, 24 insertions, 10 deletions

diff --git a/sys/dev/dcons/dcons_os.c b/sys/dev/dcons/dcons_os.c
index 7eb89aadbae8..5715343e721c 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) {