Add ARM Cortex-M OpenOCD arch, command, and session manager

[Grazfather]

This is for debugging ARM cortex-m targets through JTAG/SWD using the gdbserver implemented in OpenOCD.

Manually tested with a debugger and openocd

[hugsy]

LGTM

[Grazfather]

Still needs work, mostly in the gef project, but want to have a way for an arch to hint to the memory manager how to map.

[hugsy]

Does this PR still make sense (after #99 got merged)?

[Grazfather]

Does this PR still make sense (after #99 got merged)?

Yes. That was for BlackMagicProbe, this is for OpenOCD. Updated the description so it makes sense.

Still need to do more testing and write docs.

[hugsy]

very cool stuff, too bad I can't test it I'd love to try but the code is sound (very minor stuff to fix)

[PowerUser64]

I tested this on a Tiva C-series (ek-tm4c123gxl) through openocd and everything seems to work fine. LGTM?

[Grazfather]

@PowerUser64 thanks for testing this out. I just applied what should be a no-op change as suggested by @hugsy . Any chance you could try to ensure it still works? We can merge then. I just don't have the hardware accessible for a few days and I basically forgot this PR was still open, so it would be nice to merge.

[PowerUser64]

Seems to work! I'm able to place (hardware) breakpoints, go to next instructions, watch variables (done by halting pc every frame), and I get registers, stack, code, threads, and trace from gef's data printout. Would you like me to test loading arm-openocd.py in any way other than source ./arm-openocd.py, then arch set armopenocd after gef-extras is loaded? (Or is that the intended way?)

[Grazfather]

Ah, you should use the gef-openocd-remote which also sets up the remote. How were you connecting to the target?

[PowerUser64]

I've been using this command to start openocd and connect to the board:

gef -ex 'target extended-remote | openocd -f board/ek-tm4c1294xl.cfg -c "gdb_port pipe; log_output openocd.log"; monitor reset; monitor halt' ./build/debug.axf

Using gef-openocd-remote, I get an error:

# *first, launched openocd from another terminal like this: openocd -f board/ti_ek-tm4c123gxl.cfg
# ...
gef> gef-openocd-remote localhost 3333
0x0000048e in SystemInit () at src/system_TM4C123.c:608608         for (i = 0; i < 10000; i++);   /* wait a while */
[*] Using `target remote` with GEF should work in most cases, but use `gef-remote` if you can. You can disable the overwrite of the `target remote` command by toggling `gef.disable_target_remote_overwrite` in the config.
[!] Command 'gef-openocd-remote' failed to execute properly, reason: Specified arch ARMOPENOCD is not supported 

In the error, it looks like it's capitalizing the architecture name. When I use arch set, I give it armopenocd in lowercase, but the error it's upper case.

However, I'm also noticing that I don't get the gef-openocd-remote command until after I do source ./arm-openocd.py, so it could be something with my environment. I feel like gef-extras should be loading this by default, along with the other "extra" things that it definitely is loading, but it seems extra arches are unloaded by default. I checked the docs to see if it says how to load these, but I couldn't seem to find anything suggesting a way to automatically load it. Does gef provide a way to load files like arm-openocd.py other than putting source /path/to/gef-extras/archs/arm-openocd.py in ~/.gdbinit?

[Grazfather]

I manually source mine after gef.py and the rest of gef-extras. The arch selection should not be case sensitive. I can't repro this (without hardware atm) but will test with hardware this week.

If what you have is working, that's great! I've never seen the gdb_port pipe openocd command before.

[Grazfather]

I finally had a use for this, and saw that lower case issue.

Pushed a fix in hugsy/gef#1159

x

[Grazfather]

Should be ok to merge after that PR.

[Grazfather]

I can't merge for some reason