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-rw-r--r--Documentation/DocBook/kgdb.tmpl104
1 files changed, 58 insertions, 46 deletions
diff --git a/Documentation/DocBook/kgdb.tmpl b/Documentation/DocBook/kgdb.tmpl
index 95e5f84cbf5..97618bed4d6 100644
--- a/Documentation/DocBook/kgdb.tmpl
+++ b/Documentation/DocBook/kgdb.tmpl
@@ -152,9 +152,10 @@
<para>
The kgdboc driver was originally an abbreviation meant to stand for
"kgdb over console". Kgdboc is designed to work with a single
- serial port as example, and it was meant to cover the circumstance
+ serial port. It was meant to cover the circumstance
where you wanted to use a serial console as your primary console as
- well as using it to perform kernel debugging.
+ well as using it to perform kernel debugging. Of course you can
+ also use kgdboc without assigning a console to the same port.
</para>
<sect2 id="UsingKgdboc">
<title>Using kgdboc</title>
@@ -195,37 +196,6 @@
unmodified gdb to do the debugging.
</para>
</sect2>
- <sect2 id="kgdbocDesign">
- <title>kgdboc internals</title>
- <para>
- The kgdboc driver is actually a very thin driver that relies on the
- underlying low level to the hardware driver having "polling hooks"
- which the to which the tty driver is attached. In the initial
- implementation of kgdboc it the serial_core was changed to expose a
- low level uart hook for doing polled mode reading and writing of a
- single character while in an atomic context. When kgdb makes an I/O
- request to the debugger, kgdboc invokes a call back in the serial
- core which in turn uses the call back in the uart driver. It is
- certainly possible to extend kgdboc to work with non-uart based
- consoles in the future.
- </para>
- <para>
- When using kgdboc with a uart, the uart driver must implement two callbacks in the <constant>struct uart_ops</constant>. Example from drivers/8250.c:<programlisting>
-#ifdef CONFIG_CONSOLE_POLL
- .poll_get_char = serial8250_get_poll_char,
- .poll_put_char = serial8250_put_poll_char,
-#endif
- </programlisting>
- Any implementation specifics around creating a polling driver use the
- <constant>#ifdef CONFIG_CONSOLE_POLL</constant>, as shown above.
- Keep in mind that polling hooks have to be implemented in such a way
- that they can be called from an atomic context and have to restore
- the state of the uart chip on return such that the system can return
- to normal when the debugger detaches. You need to be very careful
- with any kind of lock you consider, because failing here is most
- going to mean pressing the reset button.
- </para>
- </sect2>
</sect1>
<sect1 id="kgdbcon">
<title>Kernel parameter: kgdbcon</title>
@@ -327,6 +297,8 @@
</para>
</chapter>
<chapter id="CommonBackEndReq">
+ <title>KGDB Internals</title>
+ <sect1 id="kgdbArchitecture">
<title>Architecture Specifics</title>
<para>
Kgdb is organized into three basic components:
@@ -365,18 +337,23 @@
</listitem>
<listitem><para>kgdb I/O driver</para>
<para>
- Each kgdb I/O driver has to provide an configuration
- initialization, and cleanup handler for when it
- unloads/unconfigures. Any given kgdb I/O driver has to operate
- very closely with the hardware and must do it in such a way that
- does not enable interrupts or change other parts of the system
- context without completely restoring them. Every kgdb I/O
- driver must provide a read and write character interface. The
- kgdb core will repeatedly "poll" a kgdb I/O driver for characters
- when it needs input. The I/O driver is expected to return
- immediately if there is no data available. Doing so allows for
- the future possibility to touch watch dog hardware in such a way
- as to have a target system not reset when these are enabled.
+ Each kgdb I/O driver has to provide an implemenation for the following:
+ <itemizedlist>
+ <listitem><para>configuration via builtin or module</para></listitem>
+ <listitem><para>dynamic configuration and kgdb hook registration calls</para></listitem>
+ <listitem><para>read and write character interface</para></listitem>
+ <listitem><para>A cleanup handler for unconfiguring from the kgdb core</para></listitem>
+ <listitem><para>(optional) Early debug methodology</para></listitem>
+ </itemizedlist>
+ Any given kgdb I/O driver has to operate very closely with the
+ hardware and must do it in such a way that does not enable
+ interrupts or change other parts of the system context without
+ completely restoring them. The kgdb core will repeatedly "poll"
+ a kgdb I/O driver for characters when it needs input. The I/O
+ driver is expected to return immediately if there is no data
+ available. Doing so allows for the future possibility to touch
+ watch dog hardware in such a way as to have a target system not
+ reset when these are enabled.
</para>
</listitem>
</orderedlist>
@@ -419,6 +396,38 @@
does not need to provide a specific implementation.
</para>
!Iinclude/linux/kgdb.h
+ </sect1>
+ <sect1 id="kgdbocDesign">
+ <title>kgdboc internals</title>
+ <para>
+ The kgdboc driver is actually a very thin driver that relies on the
+ underlying low level to the hardware driver having "polling hooks"
+ which the to which the tty driver is attached. In the initial
+ implementation of kgdboc it the serial_core was changed to expose a
+ low level uart hook for doing polled mode reading and writing of a
+ single character while in an atomic context. When kgdb makes an I/O
+ request to the debugger, kgdboc invokes a call back in the serial
+ core which in turn uses the call back in the uart driver. It is
+ certainly possible to extend kgdboc to work with non-uart based
+ consoles in the future.
+ </para>
+ <para>
+ When using kgdboc with a uart, the uart driver must implement two callbacks in the <constant>struct uart_ops</constant>. Example from drivers/8250.c:<programlisting>
+#ifdef CONFIG_CONSOLE_POLL
+ .poll_get_char = serial8250_get_poll_char,
+ .poll_put_char = serial8250_put_poll_char,
+#endif
+ </programlisting>
+ Any implementation specifics around creating a polling driver use the
+ <constant>#ifdef CONFIG_CONSOLE_POLL</constant>, as shown above.
+ Keep in mind that polling hooks have to be implemented in such a way
+ that they can be called from an atomic context and have to restore
+ the state of the uart chip on return such that the system can return
+ to normal when the debugger detaches. You need to be very careful
+ with any kind of lock you consider, because failing here is most
+ going to mean pressing the reset button.
+ </para>
+ </sect1>
</chapter>
<chapter id="credits">
<title>Credits</title>
@@ -427,8 +436,11 @@
<orderedlist>
<listitem><para>Amit Kale<email>amitkale@linsyssoft.com</email></para></listitem>
<listitem><para>Tom Rini<email>trini@kernel.crashing.org</email></para></listitem>
- <listitem><para>Jason Wessel<email>jason.wessel@windriver.com</email></para></listitem>
</orderedlist>
+ In March 2008 this document was completely rewritten by:
+ <itemizedlist>
+ <listitem><para>Jason Wessel<email>jason.wessel@windriver.com</email></para></listitem>
+ </itemizedlist>
</para>
</chapter>
</book>