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Date:      Thu, 20 Apr 2000 01:44:59 -0700 (PDT)
From:      "NandaKumar P.K." <p_k_nandan@yahoo.com>
To:        freebsd-hackers@freebsd.org
Subject:   Remote kernel debugging
Message-ID:  <20000420084459.11675.qmail@web1901.mail.yahoo.com>

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Hi,

We were trying to debug the SCSI CAM driver using
remote gdb, but we were not able to establish the
connection between the target machine and host
machine.

The host and the target machine were connected using a
null modem cable which was tested using Pcplus utility
in DOS. In both the machines the cable is connected to
the COM1 port.

The steps which we followed were as follows.
In the host machine
1. Made a copy of the GENERIC kernel called MYKERNEL.
2. The follwing additions were made to MYKERNEL
  options DDB
  device sio0 at isa? port "IO_COM1" flags 0x080
3. Compiled using config -g and installed MYKERNEL .
4. Made a copy of the kernel , kernel.debug
5. Copied the kernel.debug to the target machine.

In the target machine
1. Strip -x kernel.debug & then reboot.
2. At the boot prompt ,loaded kernel.debug
3. Opened the debugger using boot -d

In the host machine
1. cd /usr/src/sys/compile/MYKERNEL
2. gdb -k kernel
3. (kgdb) target remote /dev/cuaa0

In the target
1.db>gdb
2. s

Now the following error message was displayed in the
host
 Ignoring packet error,continuing..
 Ignoring packet error,continuing..
 Ignoring packet error,continuing..
 Could'nt establish connection to remote target
 Malformed response to offset query,timeout

Using the same cable i was able to set the serial
console on the machine and were able to find the
printf messages coming on the other machine. I also
found some characters sent by the host machine when
the target
remote /dev/cuaa0 command is given. I had the terminal
emulation package pcplus on the other machine. But i
couldn't find any character sent by the target machine
when 's' is pressed there. So i have a doubt regarding
my target machine's setting is not O.K. But i am not
able to find the problem there. Any help will be
deeply appreciated.

Regards,
Nandan









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