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, 9 insertions, 2 deletions

diff --git a/include/linux/kgdb.h b/include/linux/kgdb.h
index 4830142ec339..5b37df00000d 100644
--- a/include/linux/kgdb.h
+++ b/include/linux/kgdb.h
@@ -16,10 +16,12 @@
 #include <linux/serial_8250.h>
 #include <linux/linkage.h>
 #include <linux/init.h>
-
 #include <asm/atomic.h>
+#ifdef CONFIG_HAVE_ARCH_KGDB
 #include <asm/kgdb.h>
+#endif
 
+#ifdef CONFIG_KGDB
 struct pt_regs;
 
 /**
@@ -262,6 +264,7 @@ extern struct kgdb_arch		arch_kgdb_ops;
 
 extern unsigned long __weak kgdb_arch_pc(int exception, struct pt_regs *regs);
 
+extern void kgdb_arch_set_pc(struct pt_regs *regs, unsigned long pc);
 extern int kgdb_register_io_module(struct kgdb_io *local_kgdb_io_ops);
 extern void kgdb_unregister_io_module(struct kgdb_io *local_kgdb_io_ops);
 extern struct kgdb_io *dbg_io_ops;
@@ -279,5 +282,9 @@ extern int kgdb_nmicallback(int cpu, void *regs);
 
 extern int                      kgdb_single_step;
 extern atomic_t                 kgdb_active;
-
+#define in_dbg_master() \
+        (raw_smp_processor_id() == atomic_read(&kgdb_active))
+#else /* ! CONFIG_KGDB */
+#define in_dbg_master() (0)
+#endif /* ! CONFIG_KGDB */
 #endif /* _KGDB_H_ */