Commit 4aad8f51 authored by Jason Wessel's avatar Jason Wessel

kdb: Add kdb kernel module sample

Add an example of how to add a dynamic kdb shell command via a kernel
Signed-off-by: default avatarJason Wessel <>
parent 12ba8d1e
......@@ -710,7 +710,18 @@ Task Addr Pid Parent [*] cpu State Thread Command
<listitem><para>A simple shell</para></listitem>
<listitem><para>The kdb core command set</para></listitem>
<listitem><para>A registration API to register additional kdb shell commands.</para>
<para>A good example of a self-contained kdb module is the "ftdump" command for dumping the ftrace buffer. See: kernel/trace/trace_kdb.c</para></listitem>
<listitem><para>A good example of a self-contained kdb module
is the "ftdump" command for dumping the ftrace buffer. See:
<listitem><para>For an example of how to dynamically register
a new kdb command you can build the kdb_hello.ko kernel module
from samples/kdb/kdb_hello.c. To build this example you can
set CONFIG_SAMPLES=y and CONFIG_SAMPLE_KDB=m in your kernel
config. Later run "modprobe kdb_hello" and the next time you
enter the kdb shell, you can run the "hello"
<listitem><para>The implementation for kdb_printf() which
emits messages directly to I/O drivers, bypassing the kernel
......@@ -54,4 +54,11 @@ config SAMPLE_KFIFO
If in doubt, say "N" here.
tristate "Build kdb command exmaple -- loadable modules only"
depends on KGDB_KDB && m
Build an example of how to dynamically add the hello
command to the kdb shell.
endif # SAMPLES
# Makefile for Linux samples code
obj-$(CONFIG_SAMPLES) += kobject/ kprobes/ tracepoints/ trace_events/ \
hw_breakpoint/ kfifo/
hw_breakpoint/ kfifo/ kdb/
obj-$(CONFIG_SAMPLE_KDB) += kdb_hello.o
* Created by: Jason Wessel <>
* Copyright (c) 2010 Wind River Systems, Inc. All Rights Reserved.
* This file is licensed under the terms of the GNU General Public
* License version 2. This program is licensed "as is" without any
* warranty of any kind, whether express or implied.
#include <linux/module.h>
#include <linux/kdb.h>
* All kdb shell command call backs receive argc and argv, where
* argv[0] is the command the end user typed
static int kdb_hello_cmd(int argc, const char **argv)
if (argc > 1)
if (argc)
kdb_printf("Hello %s.\n", argv[1]);
kdb_printf("Hello world!\n");
return 0;
static int __init kdb_hello_cmd_init(void)
* Registration of a dynamically added kdb command is done with
* kdb_register() with the arguments being:
* 1: The name of the shell command
* 2: The function that processes the command
* 3: Description of the usage of any arguments
* 4: Descriptive text when you run help
* 5: Number of characters to complete the command
* 0 == type the whole command
* 1 == match both "g" and "go" for example
kdb_register("hello", kdb_hello_cmd, "[string]",
"Say Hello World or Hello [string]", 0);
return 0;
static void __exit kdb_hello_cmd_exit(void)
MODULE_DESCRIPTION("KDB example to add a hello command");
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