[U-Boot] remote debug u-boot through serial port

[Ding, ChiX]

Hi there
I'm learning how to remote debug u-boot through serial port.
In menuconfig general setup, I selected "enable debug information for tools".
It adds -g in gcc flag. After built is over, I got u-boot, u-boot.sym, u-boot.map and a few other files.
When I run objdump -trS u-boot, it does show the source code and the symbols.

However in gdb, when I tried to load the ELF executable file,  I got this error
(gdb) file u-boot
Reading symbols from u-boot...BFD: /root/work/cid_iafw_opensource-coreboot/payloads/external/U-Boot/u-boot/u-boot: attempt to load strings from a non-string section (number 0)
BFD: /root/work/cid_iafw_opensource-coreboot/payloads/external/U-Boot/u-boot/u-boot: attempt to load strings from a non-string section (number 0)

Anything I missed and caused this issue?
Also I wonder if I want to enable remote debugging of u-boot through serial port, what shall I do in the configuration?
I didn't see such option in menuconfig.  Is it enabled by default or shall I enable CONFIG_CMD_KGDB in my board config file ?

Thanks,
Chi


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