In addition to the debugging of a Linux kernel that has already been started, with help of the UDE it is also possible to copy a newly built kernel image in the RAM of the target system.
This has the advantage that the debugging of the kernel is possible from the first line, in other words even before initialization of the MMU. The boot parameter "ATAG list" or "kernel command line" can also be comfortably configured via a HTML page that is integrated in the UDE, and copied to the correct position in the target memory (figure 7).
Furthermore, by means of a selection box, it can be decided if the target system loads an "initrd" (initial RAM disk) or via NFS (Network File System) the root file system. If the decision is made for the loading of an "initrd", then with the UDE a minimum "initrd" generated with the build process can be copied direct on the target. The use of external tools can therefore be entirely omitted.
Fig 7: Initialization of the boot parameter of the Linux kernel
To see a bigger version of this graphic click here.
Summary
To perform Linux kernel and application debugging on ARM9/ARM11-based embedded systems in parallel and without today's usual risks of deadlock scenarios, a synchronization of the conventional debug types is necessary. However, in order to accomplish this, new innovative tools - such as the Universal Debug Engine (UDE) - are required. The UDE allows a kernel and application debugging via a single JTAG interface and by the integration of both approaches combines their advantages, without the user therefore having to accept the disadvantages of missing synchronization.
References
[1] Linux Kernel Organisation: The Linux Kernel Archives, 2009
[2] Free Software Foundation (FSF): gdb Server Documentation, 2009
Heiko Riessland & Frank Noack are with pls Programmierbare Logik & Systeme GmbH, Technologiepark, 02991 Lauta, Germany. info@pls-mc.com
