GDB Connection Problem

The "g" packet sent from your gdb client to Atollic gdb server was requiring all the target registers information. It is kind of handshake thing during the set up of connection. The error is due to the assumption of gdb client isn't consistent with the information returned from the gdb server.

The detailed cause is:
For you case, the gdb client figures out target register information from your ELF file which I assume is compiled for armv7-m or armv7e-m. Apparently those architectures don't contain any legacy FPA registers. That's also the recent GDB regards. You gdb client thinks so too. But the Atollic gdb server doesn't think so. For some reason, it returns register info which contains eight 96bit FPA registers. That breaks the assumption of gdb client and causes the complain of "reply is too long".

There are two solutions for this issue:
1) Pick up another GDB server which can return correct target register info. For STM32F4 board, there is a specific open source GDB server for STLINK at https://github.com/texane/stlink. You can give it a shot.

2) Or compose a special target description xml file which contains armv7-m core registers and faked FPA registers, then use gdb command "set tdesc filename YOUR-XML-FILE" to let the gdb client also assume the target contains FPA registers.

Meanwhile I am gonna to talk to Atollic to see if they can do something to their GDB server. But it will take some time.

Here is an example XML file for your reference:

<?xml version="1.0"?>
<!-- Copyright (C) 2007, 2008, 2009, 2010, 2011 Free Software Foundation, Inc.
Copying and distribution of this file, with or without modification,
are permitted in any medium without royalty provided the copyright
notice and this notice are preserved. -->
<!-- A target description for an M-profile device, for stubs that
transfer registers using the historical fpa layout. -->
<!DOCTYPE target SYSTEM "gdb-target.dtd">
<target>
<feature name="org.gnu.gdb.arm.m-profile">
<reg name="r0" bitsize="32"/>
<reg name="r1" bitsize="32"/>
<reg name="r2" bitsize="32"/>
<reg name="r3" bitsize="32"/>
<reg name="r4" bitsize="32"/>
<reg name="r5" bitsize="32"/>
<reg name="r6" bitsize="32"/>
<reg name="r7" bitsize="32"/>
<reg name="r8" bitsize="32"/>
<reg name="r9" bitsize="32"/>
<reg name="r10" bitsize="32"/>
<reg name="r11" bitsize="32"/>
<reg name="r12" bitsize="32"/>
<reg name="sp" bitsize="32" type="data_ptr"/>
<reg name="lr" bitsize="32"/>
<reg name="pc" bitsize="32" type="code_ptr"/>
<!-- Slack for unused FPA registers (f0-f7 + fps).
See arm-fpa.xml. -->
<reg name="" bitsize="96" type="arm_fpa_ext" regnum="16"/>
<reg name="" bitsize="96" type="arm_fpa_ext"/>
<reg name="" bitsize="96" type="arm_fpa_ext"/>
<reg name="" bitsize="96" type="arm_fpa_ext"/>
<reg name="" bitsize="96" type="arm_fpa_ext"/>
<reg name="" bitsize="96" type="arm_fpa_ext"/>
<reg name="" bitsize="96" type="arm_fpa_ext"/>
<reg name="" bitsize="96" type="arm_fpa_ext"/>
<reg name="" bitsize="32"/>
<reg name="xpsr" bitsize="32" regnum="25"/>
</feature>
</target>

Thanks for trying out our tool chain and please let me know if you have any question.

Terry