mirror of
https://git.do.srb2.org/STJr/SRB2.git
synced 2024-11-29 23:52:30 +00:00
171 lines
No EOL
6.5 KiB
Text
171 lines
No EOL
6.5 KiB
Text
GDB Stub for DJGPP 0.2 Readme File
|
|
==================================
|
|
|
|
Copyright
|
|
---------
|
|
GDB Stub for DJGPP is distributed under the terms of the GNU Library
|
|
General Public License (GNU LGPL) - please see the document LICENSE,
|
|
which should be found in the same directory as this file.
|
|
|
|
Copyright (c) 2000 by Jonathan Brogdon, 2002 by Gordon Schumacher
|
|
|
|
What It Does
|
|
------------
|
|
The GDB stub is used to debug a DJGPP target remotely over a one of
|
|
the PC COM ports. GDB, running on a host machine, communicates with
|
|
the target using the GDB serial protocol over the serial link. For
|
|
more information on the GDB stub, see "Debugging with GDB, The GNU
|
|
Source-Level Debugger", by Richard M. Stallman and Roland H. Pesch
|
|
(http://sources.redhat.com/gdb/download/onlinedocs/gdb.html)
|
|
|
|
How It Works
|
|
------------
|
|
|
|
Exceptions:
|
|
|
|
The GDB stub needs to handle all processor exceptions. Since these
|
|
exceptions already handled by DJGPP, we cannot handle them directly.
|
|
DJGPP maps all processor exceptions to signals. Therefore, we can
|
|
install the GDB stub handler as the signal handler for those signals
|
|
that represent processor exceptions. The following table shows the
|
|
processor exception to signal mapping:
|
|
|
|
Exception/Interrupt: Exception #: Signal:
|
|
------------------- ----------- ------
|
|
Divide Error 0 SIGFPE
|
|
Debug Exception 1 SIGTRAP
|
|
NMI Interrupt 2 No signal defined
|
|
Breakpoint 3 SIGTRAP
|
|
INTO-detected overflow 4 SIGFPE
|
|
BOUND Range Exceeded 5 SIGSEGV
|
|
Invalid Opcode 6 No signal defined
|
|
Coprocessor not available 7 SIGNOFP
|
|
Double Fault 8 SIGSEGV
|
|
Coprocessor Seg overrun 9 SIGSEGV
|
|
Invalid Task State Seg 10 No signal defined
|
|
Segment not present 11 SIGSEGV
|
|
Stack Fault 12 SIGSEGV
|
|
General Protection Fault 13 SIGSEGV
|
|
Page Fault 14 SIGSEGV
|
|
Intel Reserved 15 No signal defined
|
|
Coprocessor Error 16 SIGFPE
|
|
|
|
The GDB stub handler services requests from the GDB host. These
|
|
requests are seen by the GDB stub handler as command messages from
|
|
the GDB host. These commands and command formats are defined in
|
|
"Debugging with GDB, The GNU Source-Level Debugger", by Richard M.
|
|
Stallman and Roland H. Pesch (http://sources.redhat.com/gdb/
|
|
download/onlinedocs/gdb.html -- one of many sources).
|
|
|
|
Serial Interface:
|
|
|
|
Interface functions for sending and receiving characters from the
|
|
serial interface must be provided by the engineer porting the GDB
|
|
stub. The following funtions must be provided to support the
|
|
implementation.
|
|
|
|
int getDebugChar(void);
|
|
void putDebugChar(int c);
|
|
|
|
There are a variety of serial libraries for DJGPP. The user may
|
|
already be using one of these libraries in their application, and
|
|
installing more than one serial library often causes conflicts.
|
|
To this end, a modular function layer was written that allows any
|
|
serial library to be used with the GDB stub. Layers have been
|
|
written to support SVAsync, DZComm, and the _bios_serialcom()
|
|
function. At the time of this writing, DZComm appears to work the
|
|
best for serial debugging.
|
|
|
|
Hard Coded Breakpoint:
|
|
|
|
A breakpoint() function is provided to manually invoke the stub.
|
|
This function, inserts a breakpoint instruction directly in the code
|
|
to invoke the GDB stub handler.
|
|
|
|
How You Use It
|
|
--------------
|
|
First, you need to select a serial library. In the i386-supp.c file,
|
|
there are lines of the form
|
|
|
|
// #include "some_layer.h"
|
|
|
|
Uncomment the line for the serial library you intend to use - or add
|
|
a new include line for a file written for some other library.
|
|
In the main() function of your target program, you should initilize
|
|
the GDB serial handlers and the GDB stub. The following functions
|
|
are provided in the GDB stub library for this purpose.
|
|
|
|
gdb_serial_init(unsigned int port, unsigned int speed);
|
|
gdb_target_init(void);
|
|
|
|
Where, port is the COM port number, and speed is the baud rate for
|
|
the serial link.
|
|
|
|
After initialing the GDB serial interface and target, you should
|
|
invoke the breakpoint() function somewhere. You may choose to do
|
|
this immediately after initialization, or at a specific location in
|
|
your code where you wish to set a breakpoint. By putting the
|
|
breakpoint() function in the beginning of main(), you can use the
|
|
GDB host to set a breakpoint at any place in your code.
|
|
|
|
Make sure that you use the '-g' option when compiling your files with
|
|
gcc.
|
|
|
|
After the target executable is running, start up gdb on the host,
|
|
passing the target executable as an argument.
|
|
|
|
Example: gdb demo.exe
|
|
|
|
Now, tell gdb which serial interface to use for communicating to
|
|
the target.
|
|
|
|
Example: (gdb) target remote COM1
|
|
|
|
This example uses COM1 on the host to communicate with the target.
|
|
GDB is now 'listening' on COM for a valid GDB serial packet.
|
|
|
|
Once your GDB host finds your target, you may need to tell GDB where
|
|
to find any source files which were used to generate your program.
|
|
Use the directory command to do this.
|
|
|
|
Example: (gdb) directory ../src/demo
|
|
|
|
That's it. You should now be able to single step through code, set
|
|
breakpoints, set variables, examine variables, any anthing else that
|
|
you would normally use GDB to accomplish.
|
|
|
|
What You Build
|
|
--------------
|
|
Read the INSTALL file for more information on installing the GDB stub
|
|
library. After installing the library, your code should include
|
|
i386-stub.h for function prototypes. In addition, your code should
|
|
link against the libgdb.a library. The source for a demonstration
|
|
program has been included with this distributias an example.
|
|
As an alternative, you can simply include the i386-stub and i386-supp
|
|
files and the layer header for the serial library you plan to use into
|
|
your project and link them in directly.
|
|
|
|
For More Info
|
|
-------------
|
|
See "Debugging with GDB, The GNU Source-Level Debugger", by Richard
|
|
M. Stallman and Roland H. Pesch (http://sources.redhat.com/gdb/
|
|
download/onlinedocs/gdb.html -- one of many sources).
|
|
|
|
TODO
|
|
----
|
|
Port for network operation.
|
|
|
|
Contact Info
|
|
------------
|
|
My contact info is below. If you have any comments, suggestions, bug
|
|
reports or problems, please mail me, and I'll see what I can do.
|
|
|
|
Regards,
|
|
Jonathan Brogdon
|
|
<brogdon@austin.rr.com>
|
|
6th June 2000
|
|
|
|
Modular update:
|
|
Gordon Schumacher
|
|
<gordons@valleyhold.org>
|
|
12th February 2002 |