topic Re: KGDB on i.MX8 serial in i.MX Processors

KGDB on i.MX8 serial

lorenzo_giraudi — Fri, 23 Oct 2020 06:47:37 GMT

Hello,

I am trying to debug the Linux Kernel remotely using KGDB over the serial port.

I followed the instruction shown here: https://elinux.org/images/1/1b/ELC19_Serial_kdb_kgdb.pdf but can't make it to work. This is what I get:

I can do echo ttyLP0 > /sys/module/kgdboc/parameters/kgdboc and it gets successfully registered (note: ttyLP0 is my console too)
when I do echo g > /proc/sysrq-trigger I get messages telling that the kernel dropped into kdb, then I see the kdb prompt but it stops there, when I try to type nothing happens

I have the idea that it may involve the polling functions lpuart32_poll_put_char and lpuart32_poll_get_char but I do not know how to debug it.

It would be great to know if someone from NXP ever tried it.

BR,

Lorenzo

nxf63675 — Thu, 17 Dec 2020 06:12:35 GMT

Hi Lorenzo,

Connecting the debugger can work in my side, as follows:

For gdb-multiarch, customer need to "set architecture aarch64" firstly,then "target remote /dev/ttyUSBx".

Another method:

If you want to extending the terminals, they can use agent-proxy. The steps is as follows:

in another terminal:

Then in the third terminal, executing "gdb-multiarch vmlinux" or "aarch64-poky-linux-gdb vmlinux" to connect target.

Note the last picture, "target remote localhost:5551" when connecting target.

Best Regards,

Israel H.

lorenzo_giraudi — Wed, 27 Jan 2021 13:24:38 GMT

Hello Israel,

Thank you very much for the detailed description. I will try to replicate it and see if I can do that.

Best regards,

Lorenzo Giraudi