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kdb: Add kdb kernel module sample
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Add an example of how to add a dynamic kdb shell command via a kernel
module.

Signed-off-by: Jason Wessel <[email protected]>
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jwessel committed Oct 29, 2010
1 parent 12ba8d1 commit 4aad8f5
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13 changes: 12 additions & 1 deletion Documentation/DocBook/kgdb.tmpl
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Expand Up @@ -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>
<itemizedlist>
<listitem><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>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"
command.</para></listitem>
</itemizedlist></listitem>
<listitem><para>The implementation for kdb_printf() which
emits messages directly to I/O drivers, bypassing the kernel
log.</para></listitem>
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7 changes: 7 additions & 0 deletions samples/Kconfig
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Expand Up @@ -54,4 +54,11 @@ config SAMPLE_KFIFO

If in doubt, say "N" here.

config SAMPLE_KDB
tristate "Build kdb command exmaple -- loadable modules only"
depends on KGDB_KDB && m
help
Build an example of how to dynamically add the hello
command to the kdb shell.

endif # SAMPLES
2 changes: 1 addition & 1 deletion samples/Makefile
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@@ -1,4 +1,4 @@
# Makefile for Linux samples code

obj-$(CONFIG_SAMPLES) += kobject/ kprobes/ tracepoints/ trace_events/ \
hw_breakpoint/ kfifo/
hw_breakpoint/ kfifo/ kdb/
1 change: 1 addition & 0 deletions samples/kdb/Makefile
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obj-$(CONFIG_SAMPLE_KDB) += kdb_hello.o
60 changes: 60 additions & 0 deletions samples/kdb/kdb_hello.c
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/*
* Created by: Jason Wessel <[email protected]>
*
* 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)
return KDB_ARGCOUNT;

if (argc)
kdb_printf("Hello %s.\n", argv[1]);
else
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)
{
kdb_unregister("hello");
}

module_init(kdb_hello_cmd_init);
module_exit(kdb_hello_cmd_exit);

MODULE_AUTHOR("WindRiver");
MODULE_DESCRIPTION("KDB example to add a hello command");
MODULE_LICENSE("GPL");

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