Hi Olof, Olof Backing wrote:
Is it possible to use the debug application (found for instance in the nios2 uclinux) to achieve user application debugging? Or is the kernel lacking some important stuff that will make this solution impossible?There is no direct support for using JTAG to debug userapplications, however gdbserver / mb-uclinuc-gdb can work over a serial port. In principal you could debug over the MDM-uart. I seem to recall this was discussed previously on the list, see what the archives have to say.Is this to say that it's for ever impossible, or just currently a not supported option for debugging for the petalinux/microblaze combo? The reason why I stress this question is I still can achieve this by support from the Altera/Nios uClinux community when understanding how they did make it work on that softcore?
It's not impossible but rather difficult, as it would require either(1) getting CPU control over the debug interfaceto enable CPU single step mode and breakpoints etc to be set by the CPU itself. Currently this functionality is only accessible through JTAG/MDM.
or(2) modifying XMD to be able to talk to mb-linux-gdb (userspace app debugger, not standalone mb-gdb) and talk to kernel to implement the neceesary hooks to query the address offsets of userspace proceses
or (3) create a new host-based JTAG stub instead of XMD to do the same.None of these are a quick afternoon's hacking by any means. (1) might be achievable by reverse engineering the microblaze hardware debug signal protocol and creating a simple CPU interface to it. (2) is impossible unless you work for Xilinx, and (3) is a lot of work.
In contract, getting gdbserve rto work over the MDM/uart serial link should be pretty straight forward, as all of the hard work is already done.
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