Difference between revisions of "KDB"

From eLinux.org
Jump to: navigation, search
(Kernel configuration)
(add link to official kdb/kgdb docs)
Line 13: Line 13:
 
* video 5 of 6: http://www.youtube.com/watch?v=sWiHV5mt8_k - use an address watch (hardware watchpoint) using kgdb (data access hardware breakpoint on tp_address_ref)
 
* video 5 of 6: http://www.youtube.com/watch?v=sWiHV5mt8_k - use an address watch (hardware watchpoint) using kgdb (data access hardware breakpoint on tp_address_ref)
 
* video 6 of 6: http://www.youtube.com/watch?v=nnopzcwvLTs - use of kgdb over serial - Start up the agent-proxy and connect and hit a breakpoint a sys_sync
 
* video 6 of 6: http://www.youtube.com/watch?v=nnopzcwvLTs - use of kgdb over serial - Start up the agent-proxy and connect and hit a breakpoint a sys_sync
 +
 +
Documentation, up-to-date as of 2010, for KDB and KGDB is at:
  
 
== Older Information ==
 
== Older Information ==
Line 31: Line 33:
 
** sysrq trigger ('echo g >/proc/sysrq-trigger')
 
** sysrq trigger ('echo g >/proc/sysrq-trigger')
 
* how to use agent-proxy to multiplex console and kdb (or is this only for kgdb?)
 
* how to use agent-proxy to multiplex console and kdb (or is this only for kgdb?)
 +
  
 
== Kernel configuration ==
 
== Kernel configuration ==

Revision as of 23:05, 22 June 2011

Here is some information about KDB - the in-kernel debugger for the Linux kernel.

The KDB and KGDB official wiki: https://kgdb.wiki.kernel.org/

Jason Wessel is the current KDB maintainer. Here is a presentation from him at LinuxCon 2010 (August 2010): http://kernel.org/pub/linux/kernel/people/jwessel/dbg_webinar/State_Of_kernel_debugging_LinuxCon2010.pdf

Here are some videos showing use of KDB and KGDB:

Documentation, up-to-date as of 2010, for KDB and KGDB is at:

Older Information

See http://www.ibm.com/developerworks/linux/library/l-kdbug/ for a tutorial for the 2.4.20 kernel (from June 2003)

Here's an article from 2002 on KDB vs. KGDB: http://kerneltrap.org/node/112 It has a good discussion excerpt between Andrew Morton and Keith Owens about the relative merits of KDB versus KGDB.

Questions

Here are some questions to answer:

  • What kernel versions are supported?
    • 2.6.35 and on
  • what kernel configs are required to be set?
    • CONFIG_KDB
    • CONFIG_
  • how to invoke the debugger?
    • panic
    • sysrq trigger ('echo g >/proc/sysrq-trigger')
  • how to use agent-proxy to multiplex console and kdb (or is this only for kgdb?)


Kernel configuration

In a 2.6.35 kernel, CONFIG_KGDB=y is used to configured the kgdb (target agent) for the kernel, for gdb.

Use CONFIG_KGDB_SERIAL_CONSOLE=Y to share a serial console with kgdb. Sysrq-g must be used to break in initially.

Selecting this will automatically set CONSOLE_POLL=N and MAGIC_SYSRQ=Y.

CONFIG_KGDB_KDB=Y will include the kdb frontend for kgdb (what the heck does this mean?)

Using gdb to see the kernel source listing