Kernel debugger

A kernel debugger is a debugger present in some operating system kernels to ease debugging and kernel development by the kernel developers. A kernel debugger might be a stub implementing low-level operations, with a full-blown debugger such as GNU Debugger (gdb), running on another machine, sending commands to the stub over a serial line or a network connection, or it might provide a command line that can be used directly on the machine being debugged.

Operating systems and operating system kernels that contain a kernel debugger:

• The Windows NT family includes a kernel debugger named KD, ^[1] which can act as a local debugger with limited capabilities (reading and writing kernel memory, and setting breakpoints) ^[2] and can attach to a remote machine over a serial line, IEEE 1394 connection, USB 2.0 or USB 3.0 connection. ^[3] The WinDbg GUI debugger can also be used to debug kernels on local and remote machines.
• BeOS and Haiku include a kernel debugger usable with either an on-screen console or over a serial line. It features various commands to inspect memory, threads, and other kernel structures. In Haiku, the debugger is called "Kernel Debugging Land" (KDL). ^[4]
• DragonFly BSD
• Linux kernel; No kernel debugger was included in the mainline Linux tree prior to version 2.6.26-rc1 because Linus Torvalds didn't want a kernel debugger in the kernel. ^{[5] [6]}
  • KDB (local) ^[7]
  • KGDB (remote)
  • MDB (local/remote) ^{[8] [9] [10]}
• NetBSD has DDB for local and KGDB for remote.
• macOS has ddb for local and kdp for remote. ^[11]
• OpenBSD includes ddb which has a syntax is similar to GNU Debugger. ^[12]

References

1. "Debugging Environments". Debugging Tools for Windows (WinDbg, KD, CDB, NTSD). Retrieved 16 February 2020.
2. "Local Kernel-Mode Debugging" . Retrieved 16 February 2020.
3. "Live Kernel-Mode Debugging Using KD" . Retrieved 16 January 2020.
4. "Welcome to Kernel Debugging Land".
5. "LWN.net" . Retrieved 29 May 2008.
6. Torvalds, Linus (3 May 2008). "Linux 2.6.26-rc1". LWN. Retrieved 9 March 2015.
7. Nellitheertha, Hariprasad. "Inside the Linux kernel debugger". IBM . Archived from the original on 21 June 2008. Retrieved 29 May 2008.
8. "LWN Weekly Kernel News". 7 September 2008.
9. "MDB Github Website". 1 January 2016. Archived from the original on 22 March 2016.
10. "LWN Weekly Kernel News". 28 June 2010.
11. Singh, Amit (December 2003). "XNU: The Kernel". What is Mac OS X?. Archived from the original on 2 June 2020. Retrieved 25 May 2012. the built-in low-level kernel debugger, ddb, is part of XNU's Mach component, and so is kdp, a remote kernel debugging protocol implementation
12. "ddb(4)". OpenBSD manual page server. 6 December 2019. Retrieved 13 December 2019. The ddb debugger provides a means for debugging the kernel, and analysing the kernel after a system crash ("panic"), with a gdb(1)-like syntax.