remote kernel debugging

[Manuel Stühn]

On Sun, 22 Mar 2015 02:10:54 +0100, Bernd Walter wrote
> The flags are documented in the uart manpage.
> 0x10 flag sets the console uart and 0x80 the gdb uart.
> 0x90 sets both.
> But it assumes /boot/device.hints to be used, which to my knowledge isn't
> true on the BBB.
> The console is setup via stdin/stdout in
> sys/boot/fdt/dts/arm/beaglebone.dts
> No idea how gdb or any of the other flags can be entered in the DTS files.
>

After further investigation I found this flag for loader(8):

set hw.uart.dbgport="mm:0x48022000,br:115200" # uart1 on BBB

(more info in sys/dev/uart/uart_subr.c), which seems to be able to 
inform the debug-system about the desired uart-port. Unfortunately, when 
I'm setting this variable like shown above the systems stops right here:

Hit [Enter] to boot immediately, or any other key for command prompt.
Booting [/boot/kernel/kernel]...
Using DTB provided by U-Boot at address 0x80000100.
Kernel entry at 0x80200100...
Kernel args: (null)
GDB: debug ports: uart

No further output appears, it seems that the whole system stopped at 
this point.

Any hints?

Thanks,
Manuel