On Mittwoch, 30. Januar 2019 11:27:41 CET Xen Mann wrote: > Hey there again! > adding this new interface I wonder, how actually does openOCD retrieve the > information where the program counter(pc) is on the target. At least the > connected client which is stepping through the lines of source code must > have a opinion where controllers pc is. Is this a client or a server thing?
> Does openOCD know at which address the next and previous pc is? Is it > configured in the scripts, is it hard coded in the target structure? No. OpenOCD is only interested in the state of the target at the point when you halt it. It retrieves all, or a subset of the registers from the debugged core, at minimum the PC, processor status and stack pointer. But it doesn't do anything with them aside from storing them in a cache. If gdb is attached it will eventually request the full register file from OpenOCD which is when the rest of the registers will be loaded. The method of loading the registers and halting, stepping, resuming the core are depending on the core architecture. It depends on the debug support the hardware has built in. Stepping is kind of a special case, depending on whether the core has hardware support for single stepping or nowt If not, it will have to be handled with breakpoints and will may require emulating branch instructions to find the places where breakpoints have to be put. Gdb will usually do that on its own, though. Your task basically boils down to the question, which part of debug hardware you access through the JTAG interface. I'm betting it will not be chip registers but it will be some kind of debug control hardware, maybe EmbeddedICE if the target core is an ARM9, for RISC-V it will be something else. This is what the chip designers will have to tell you. BR, Matthias > > > > > _______________________________________________ > OpenOCD-devel mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/openocd-devel _______________________________________________ OpenOCD-devel mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/openocd-devel
