kgdb: core changes to support kdb

These are the minimum changes to the kgdb core in order to enable an
API to connect a new front end (kdb) to the debug core.

This patch introduces the dbg_kdb_mode variable controls where the
user level I/O is routed.  It will be routed to the gdbstub (kgdb) or
to the kdb front end which is a simple shell available over the kgdboc
connection.

You can switch back and forth between kdb or the gdb stub mode of
operation dynamically.  From gdb stub mode you can blindly type
"$3#33", or from the kdb mode you can enter "kgdb" to switch to the
gdb stub.

The logic in the debug core depends on kdb to look for the typical gdb
connection sequences and return immediately with KGDB_PASS_EVENT if a
gdb serial command sequence is detected.  That should allow a
reasonably seamless transition between kdb -> gdb without leaving the
kernel exception state.  The two gdb serial queries that kdb is
responsible for detecting are the "?" and "qSupported" packets.

CC: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
Acked-by: Martin Hicks <mort@sgi.com>

1 files changed, 7 insertions, 1 deletions

diff --git a/lib/Kconfig.kgdb b/lib/Kconfig.kgdb
index 9b5d1d7f2ef..78de43a5e90 100644
--- a/lib/Kconfig.kgdb
+++ b/lib/Kconfig.kgdb
@@ -3,7 +3,7 @@ config HAVE_ARCH_KGDB
         bool
 
 menuconfig KGDB
-        bool "KGDB: kernel debugging with remote gdb"
+        bool "KGDB: kernel debugger"
         depends on HAVE_ARCH_KGDB
         depends on DEBUG_KERNEL && EXPERIMENTAL
         help
@@ -57,4 +57,10 @@ config KGDB_TESTS_BOOT_STRING
           information about other strings you could use beyond the
           default of V1F100.
 
+config KGDB_KDB
+        bool "KGDB_KDB: include kdb frontend for kgdb"
+        default n
+        help
+          KDB frontend for kernel
+
 endif # KGDB