I tried to use KGDB on Ubuntu 14.04.2 - 3.16 kernel.
Target is running with 3.16 kernel on Ubuntu 14.04.2. Host is running with 3.16 kernel on Ububtu 14.04.2.
Target is waiting for remote gdb connection.
Started my Host mechine and try to connect target..
$ gdb ./vmlinux kernel image file of target machine. $ gdb> target remote /dev/ttyS0
“unrecognized item timeout in qsupported response”.
Not able to proceed further. Can any one pass some lite on this?
The “unrecognized item timeout in qsupported response” error message most typically occurs when the serial connection between the debug station (GDB host) and target (SUT) is not running reliably in my experience. The usual solution is to do two things. FIRST, check the serial connection manually using a program such as minicom, setserial, and sty. (Check your baud rate match, and that characters appear to transfer between the two systems OK manually). Unfortunately, in my experience, the even with the correct RTS/CTS hardware flow control dongles interspersed, the KDBG agent on the target doesn't handle flow control well. So the manual test will appear to work (no real flow control with a manual test, but it does prove you have correct baud rate control on both ends and complete control). SECOND, and the typically required best solution in my experience is to lower the baud rate down to 9600. (Everyone starts at MAX, or 57600, or 34K, or 19200), but drop it to down to 9600. The data sent/received by the kernel debugger is small, and even the serial console doesn't generate a lot of data in debug situations. By locking the baud rate down to 9600, you wake sure the SUT serial kgdboc keeps up on the target, and the problem you are seeing usually goes away. If you find the speed too slow, once you have it running properly at 9600, then you can increase the speed back up one step at a time (on both ends) and find the maximum serial rate for your setup that works properly.
