GDB thread awareness info running on QEMU target

[rflmota]

Hello, I'm current learning Zephyr and was trying to run some samples on the provided qemu targets (qemu_cortex_m3), although I noticed when attaching with gdb there's no thread information provided by threads command. Is it possible to get thread awareness information with gdb running on qemu targets?

[cfriedt]

Hi @rflmota - It's not super obvious, but what I often do when I debug is

west build -p auto -b board -t debugserver path/to/app \
    -- \
    -DCONFIG_NO_OPTIMIZATIONS=y \
    -DCONFIG_DEBUG=y \
    -DCONFIG_DEBUG_INFO=y \
    -DCONFIG_DEBUG_THREAD_INFO=y

Those extra options have the following effects:

1. "Optimize nothing" (prevent symbols from being "optimized-out")
2. "Build kernel with debugging enabled"
3. "System debugging information" (additional info for debuggers)
4. "Thread awareness support" (allow gdb, openocd, etc to see thread info)

You can always navigate Kconfig options through west build -t menuconfig sort of like it's done with the Linux kernel or busybox 👍

[rflmota]

Hello @cfriedt , thank you for your tips, I tried them but wasn't successful when running on qemu_cortex_m3 target.

[cfriedt]

I don't believe qemu_cortex_m3 is SMP capable. It's possible you will only see multiple threads when debugging an SMP-capable board such as qemu_cortex_a53_smp.

E.g. today, I was debugging several SMP Qemu targets and thread info was visible.

[noahp]

In this case, I think qemu's gdbstub (server) would need to implement Zephyr rtos-awareness; i.e. in Jlink or OpenOCD, it's done by the server. I see some examples that do Zephyr rtos awareness on the client side, eg in CLion, if that helps!

[bdmendes]

I filed an issue for this, in case you are interested: zephyrproject-rtos/sdk-ng#691

[rflmota]

Awesome work @bdmendes , thank you for sharing! 🙌🏻