libs/libc:Support gdb rsp protocol

you can debug nuttx through any transport layer (serial port, network etc.),
currently supports the following functions:
1. Read and write registers
2. Read and write memory
3. Switch thread and read stack information

Future support plans:
1. Support breakpoint, watch point (requires architecture support).

related information:
https://sourceware.org/gdb/onlinedocs/gdb/Remote-Protocol.html

Signed-off-by: anjiahao <anjiahao@xiaomi.com>

include/nuttx/gdbstub.h

@@ -0,0 +1,113 @@
+/****************************************************************************
+ * include/nuttx/gdbstub.h
+ *
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.  The
+ * ASF licenses this file to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance with the
+ * License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
+ * License for the specific language governing permissions and limitations
+ * under the License.
+ *
+ ****************************************************************************/
+
+#ifndef __INCLUDE_NUTTX_GDBSTUB_H
+#define __INCLUDE_NUTTX_GDBSTUB_H
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <stdlib.h>
+
+/****************************************************************************
+ * Type Definitions
+ ****************************************************************************/
+
+struct gdb_state_s;
+typedef CODE ssize_t (*gdb_send_func_t)(FAR void *priv, FAR void *buf,
+                                        size_t len);
+typedef CODE ssize_t (*gdb_recv_func_t)(FAR void *priv, FAR void *buf,
+                                        size_t len);
+
+typedef CODE int (*gdb_monitor_func_t)(FAR struct gdb_state_s *state,
+                                       FAR const char *cmd);
+
+/****************************************************************************
+ * Name: gdb_state_init
+ *
+ * Description:
+ *   Initialize the GDB state structure.
+ *
+ * Input Parameters:
+ *   send    - The pointer to the send function.
+ *   recv    - The pointer to the receive function.
+ *   monitor - The pointer to the monitor function.
+ *   priv    - The pointer to the private data.
+ *
+ * Returned Value:
+ *   The pointer to the GDB state structure on success.
+ *   NULL on failure.
+ *
+ ****************************************************************************/
+
+FAR struct gdb_state_s *gdb_state_init(gdb_send_func_t send,
+                                       gdb_recv_func_t recv,
+                                       gdb_monitor_func_t monitor,
+                                       FAR void *priv);
+
+/****************************************************************************
+ * Name: gdb_state_uninit
+ *
+ * Description:
+ *   Uninitialize the GDB state structure.
+ *
+ * Input Parameters:
+ *   state   - The pointer to the GDB state structure.
+ *
+ ****************************************************************************/
+
+void gdb_state_uninit(FAR struct gdb_state_s *state);
+
+/****************************************************************************
+ * Name: gdb_console_message
+ *
+ * Description:
+ *   Send a message to the GDB console (via O XX... packet).
+ *
+ * Input Parameters:
+ *   state   - The pointer to the GDB state structure.
+ *
+ * Returned Value:
+ *    Zero on success.
+ *    Negative value on error.
+ *
+ ****************************************************************************/
+
+int gdb_console_message(FAR struct gdb_state_s *state, FAR const char *msg);
+
+/****************************************************************************
+ * Name: gdb_process
+ *
+ * Description:
+ *   Main debug loop. Handles commands.
+ *
+ * Input Parameters:
+ *   state   - The pointer to the GDB state structure.
+ *
+ * Returned Value:
+ *   Zero if successful.
+ *   Negative value on error.
+ *
+ ****************************************************************************/
+
+int gdb_process(FAR struct gdb_state_s *state);
+
+#endif /* __INCLUDE_NUTTX_GDBSTUB_H */

libs/libc/Kconfig

@@ -14,6 +14,7 @@ source "libs/libc/string/Kconfig"
 source "libs/libc/pthread/Kconfig"
 source "libs/libc/dlfcn/Kconfig"
 source "libs/libc/modlib/Kconfig"
+source "libs/libc/gdbstub/Kconfig"
 source "libs/libc/grp/Kconfig"
 source "libs/libc/pwd/Kconfig"
 source "libs/libc/locale/Kconfig"

libs/libc/Makefile

@@ -30,6 +30,7 @@ include dlfcn/Make.defs
 include errno/Make.defs
 include eventfd/Make.defs
 include fixedmath/Make.defs
+include gdbstub/Make.defs
 include grp/Make.defs
 include hex2bin/Make.defs
 include inttypes/Make.defs

libs/libc/gdbstub/Kconfig

@@ -0,0 +1,20 @@
+#
+# For a description of the syntax of this configuration file,
+# see the file kconfig-language.txt in the NuttX tools repository.
+#
+
+config LIB_GDBSTUB
+	tristate "GDBSTUB"
+	depends on DEBUG_TCBINFO
+	---help---
+		Enable support for gdbstub.
+
+if LIB_GDBSTUB
+
+config LIB_GDBSTUB_DEBUG
+	bool "Gdbstub Debug Info"
+	default n
+	---help---
+		Add debug info to gdbstub
+
+endif

libs/libc/gdbstub/Make.defs

@@ -0,0 +1,32 @@
+############################################################################
+# libs/libc/gdbstub/Make.defs
+#
+# Licensed to the Apache Software Foundation (ASF) under one or more
+# contributor license agreements.  See the NOTICE file distributed with
+# this work for additional information regarding copyright ownership.  The
+# ASF licenses this file to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance with the
+# License.  You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
+# License for the specific language governing permissions and limitations
+# under the License.
+#
+############################################################################
+
+ifeq ($(CONFIG_LIB_GDBSTUB),y)
+
+# Add the internal C files to the build
+
+CSRCS += lib_gdbstub.c
+
+# Add the userfs directory to the build
+
+DEPPATH += --dep-path gdbstub
+VPATH += :gdbstub
+
+endif