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First post, by diaxen

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Hi,

Here is a patch which allows using the GNU debugger as an alternative to the DOSBox built-in debugger. The built-in debugger may be more convenient to show x86 specific information about execution state, whereas Gdb is useful for C and C++ source level debugging.

This patch applies against svn revision 3761. Once applied the configure script can be used with a new option:

./autogen.sh
./configure --enable-debug=gdbserver

DOSBox then listen on TCP port 1234 and a Gdb client compiled for x86_64 or i686 targets can be connected:

$ gdb
(gdb) target remote localhost:1234

The gdb architecture must be set depending on the code your are trying to disassemble (16 or 32 bits), for instance:

(gdb) set architecture i8086
(gdb) x/32i $eip

Breakpoints and watchpoints are supported and some DOSBox specific features are available through the gdb "monitor" command.

This patch adds the following files:
- src/debug/gdb_server.cpp file
- src/debug/debug_log.cpp
- src/debug/debug_helpers.cpp

The debug.cpp file has been split in 3 files so that the original file now contains built-in debugger stuff only and debug_log.cpp/debug_helpers.cpp files contain common code used by both built-in and Gdb debuggers. Some variables which were previously local to debug.cpp have been prefixed by DEBUG_ and debug.h has been updated accordingly.

Tested under GNU/Linux.

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  • Filename
    dosbox_gdbserver.diff
    File size
    127.05 KiB
    Downloads
    66 downloads
    File license
    Fair use/fair dealing exception

Reply 3 of 6, by klei

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Is there an easy way to make this work under windows?

To make the patched r3778 compile under mingw/msys I had to re-enable <Winsock2.h> and include <io.h> into gdb_server.cpp and I had to link against -lws2_32. Furthermore I had to call WSAStartup() in DEBUG_Init() otherwise the socket() API failed with WSANOTINITIALISED.

Now it seems that the produced executable is working. I get the following message: GDB: listening on TCP port 1234.

But my remote GDB client, GDB 7.5, throws the following error messages after connection with default settings:

(gdb) target remote localhost:1234 Remote debugging using localhost:1234 Ignoring packet error, continuing... warning: unrecogni […]
Show full quote

(gdb) target remote localhost:1234
Remote debugging using localhost:1234
Ignoring packet error, continuing...
warning: unrecognized item "timeout" in "qSupported" response
Ignoring packet error, continuing...
Ignoring packet error, continuing...
Ignoring packet error, continuing...
Ignoring packet error, continuing...
Ignoring packet error, continuing...
warning: Invalid remote reply: timeout

Furthermore, whatever I try in dosbox results in a possibly endless loop:

585949507: CPU:Illegal Unhandled Interrupt Called 6 585949509: CPU:CPU:GRP5:Illegal Call 7 585949510: CPU:Illegal Unhandled I […]
Show full quote

585949507: CPU:Illegal Unhandled Interrupt Called 6
585949509: CPU:CPU:GRP5:Illegal Call 7
585949510: CPU:Illegal Unhandled Interrupt Called 6
585949512: CPU:CPU:GRP5:Illegal Call 7
585949513: CPU:Illegal Unhandled Interrupt Called 6
585949515: CPU:CPU:GRP5:Illegal Call 7
585949516: CPU:Illegal Unhandled Interrupt Called 6
585949518: CPU:CPU:GRP5:Illegal Call 7
585949519: CPU:Illegal Unhandled Interrupt Called 6
585949521: CPU:CPU:GRP5:Illegal Call 7
585949522: CPU:Illegal Unhandled Interrupt Called 6
585949524: CPU:CPU:GRP5:Illegal Call 7
585949525: CPU:Illegal Unhandled Interrupt Called 6
585949527: CPU:CPU:GRP5:Illegal Call 7
585949528: CPU:Illegal Unhandled Interrupt Called 6
585949530: CPU:CPU:GRP5:Illegal Call 7
585949531: CPU:Illegal Unhandled Interrupt Called 6
585949533: CPU:CPU:GRP5:Illegal Call 7
585949534: CPU:Illegal Unhandled Interrupt Called 6
585949536: CPU:CPU:GRP5:Illegal Call 7
585949537: CPU:Illegal Unhandled Interrupt Called 6
585949539: CPU:CPU:GRP5:Illegal Call 7
585949540: CPU:Illegal Unhandled Interrupt Called 6
585949542: CPU:CPU:GRP5:Illegal Call 7

Reply 5 of 6, by DosFreak

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Update it to compile against the latest SVN.
Create a ticket at the DOSBox sourceforge site.
List the benefits of using GDB over the DOSBox debugger.

If none of the above is done it's really sad. Also fake news.

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Reply 6 of 6, by ssokolow

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DosFreak wrote:

List the benefits of using GDB over the DOSBox debugger.

Same benefit WineDbg gains by supporting the gdbserver protocol. Access to advanced frontends like gdbgui and DDD.

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