Standalone gdb server?

For jtag (or j-link) I've used CoIde with STM3240G-EVAL. Very easy to set up and use.

Didn't quite get OpenOCD to work properly. It worked partially (I think - don't remember very well), but had to switch to CoIde.

Now the idea is to debug a bare metal program on a board (Raspberry Pi 2 B) with only serial port.r

I don't have jtag (or the like) pod, and now the only way is to compile a program on one computer, move it to another computer (without the development environment, but has a card reader), write the program onto the SD-card, take the memory and put it in RPi and boot. If it fails (how should I know?), have to do that all over.

Tedious + not good for the SD-card - or RPi memory card slot.

I'd rather have a dbg server on the SD-card so I could upload the program onto the chip and debug - and keep the SD-card in place. (That's why gdb stub is not very good solution either, although it would at least allow debugging).

Yes, I'm after the option #3.

RasPi has a bootloader, but it's for the GPU. The GPU reads in the boot code for the ARM, and it doesn't include any debugging facilities. That code basically initializes the ARM-side and reads in the kernel from the memory card. To boot your own SW, you just generate a binary image and put it onto the memory card as 'kernel.img'.

Asking from OpenOCD-guys is a good idea.

Sadly I'm no expert in this area, but here's my thoughts ... Perhaps you've already been thinking about these things.

If I understand it correctly now, it's more like a "remote debugger" you're looking for; eg. a "thin debugger" so to speak ?

-But if you're going to "run a program" on the target board, I believe you would need one of these 3...

1: An operating system

2: To link your program with a 'debugger library' (the 'stub' you mentioned)

3: A bootloader, which is also the 'thin debugger'

I expect that you're interested in something like #3 ?

(I do not know if the RasPi has a built-in bootloader, which allows simple debugging; some Cortex-M devices are 'born' with a bootloader that has a few extra features. If the RasPi has such a bootloader, already, you'd only need to write a small program on your host, which interfaces with GDB).

Although you're not looking for OpenOCD, I would still advice to ask this question on the OpenOCD developer mailing list, because many of the people there are experts; they work with ARM architectures and also know the inner workings of OpenOCD; which is a GDB server. There's a slim chance that someone could have tried something similar already.

I think not - OpenOCD also runs on host (and wants an OS around), and is used for "HW debugging" (=jtag, j-link, ...).

What I'm after is like gdb stub, but separate standalone program not linked into the program to be debugged.

I have a Linux machine as host and a bare metal ARM-board (Raspberry Pi) as a target. I don't have a jtag pod

(or anything for that function).