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* Gdb for OpenRISC 1000: (gdb for Or1K).   The GNU debugger for OpenRISC 1000.

END-INFO-DIR-ENTRY

   This file documents the GNU debugger GDB when used with OpenRISC

1000 processors.

   This is the Second Edition, of `Debugging the OpenRISC 1000 GDB' for

GDB Version 6.8.

   Copyright (C) 2008 Embecosm Limited

   Permission is granted to copy, distribute and/or modify this document

under the terms of the GNU Free Documentation License, Version 3 or any

later version published by the Free Software Foundation; with the

Front-Cover Texts being "Debugging the OpenRISC 1000 with GDB by Jeremy

Bennett" and with the Back-Cover Texts being "You are free to copy and

modify this Manual."

File: or1k.info,  Node: Top,  Next: Summary,  Prev: (dir),  Up: (dir)

Debugging the OpenRISC 1000 with GDB

************************************

This file describes GDB, the GNU symbolic debugger for use with the

OpenRISC 1000 processor architecture.

   This is the Second Edition, for GDB Version 6.8.

   Copyright (C) 2008 Embecosm Limited

* Menu:

* Summary::                         Summary of GDB with OpenRISC 1000

* Connecting to the Target::        Connecting to an OpenRISC 1000 Target

* OpenRISC 1000 Specific Commands:: Commands just for the OpenRISC 1000

* OpenRISC 1000 Example::           A small example

* OpenRISC 1000 Limitations::       Known problems

* Copying::                         GNU General Public License says

                                    how you can copy and share GDB

* GNU Free Documentation License::  The license for this documentation

* Index::                           Index

File: or1k.info,  Node: Summary,  Next: Connecting to the Target,  Prev: Top,  Up: Top

Summary of GDB with OpenRISC 1000

*********************************

GDB is described well in its user manual, "Debugging with GDB: The GNU

Source-Level Debugger".

   This manual describes how to use GDB to debug C programs cross

compiled for and running on processors using the OpenRISC 1000

architecture. In general GDB does not run on the actual target, but on

a separate host processor. It communicates with the target via the GDB

"Remote Serial Protocol" (RSP).

   For backwards compatibility, GDB for OpenRISC also supports the

legacy custom remote protocol, which drives the JTAG interface on the

OpenRISC 1000.  This is provided by adding a special target, "jtag" to

GDB, allowing the debugger to connect via the JTAG interface. *Note

Connecting to the Target: Connecting to the Target.

   In addition the info command is extended to allow inspection of

OpenRISC 1000 Special Purpose registers, and a new command "spr" is

added to set the value of a Special Purpose Register. *Note OpenRISC

1000 Specific Commands: OpenRISC 1000 Specific Commands.

   All the normal GDB commands should work, although hardware

watchpoints are not tested at present. The `info registers' command

will show the 32 general purpose registers, while the `info registers

all' command will add the program counter, supervision register and

exception program counter register.

   For those who like their debugging graphical, the `gdbtui' command is

available (typically as `or32-uclinux-gdbtui'). GDB for OpenRISC 1000

can also be run under `ddd' as follows:

     `ddd --debugger=or32-uclinux-gdb --gdb'

* Menu:

* Contributors::                Contributors to GDB for the OpenRISC 1000

File: or1k.info,  Node: Contributors,  Up: Summary

Contributors to GDB for the OpenRISC 1000

=========================================

The pantheon of contributors to GDB over the years is recorded in the

main user manual, `Debugging with GDB: The GNU Source-Level Debugger".

   There is no official history of contributors to the OpenRISC 1000

version. However the current author believes the original GDB 5.0 and

5.3 ports were the work of:

   * Ivan Guzvinec and Johan Rydverg at OpenCores, who wrote the Binary

     File Descriptor library;

   * Alessandro Forin at Carnegie-Mellon University and Per Bothner at

     the University of Wisconsin who wrote the main GDB interface; and

   * Mark Mlinar at Cygnus Support and Chris Ziomkowski at ASICS.ws,who

     wrote the OpenRISC JTAG interface.

   The port to GDB 6.8 is the work of Jeremy Bennett of Embecosm

Limited (jeremy.bennett@embecosm.com).

     Plea: If you know of anyone who has been omitted from this list,

     please email the current author, so the omission can be corrected,

     and credit given where it is due.

File: or1k.info,  Node: Connecting to the Target,  Next: OpenRISC 1000 Specific Commands,  Prev: Summary,  Up: Top

1 Connecting to an OpenRISC 1000 Target

***************************************

There are two ways to connect to an OpenRISC 1000 target with GDB.

  1. To hardware directly connected via a JP1 header linked to the

     parallel port. This uses the GDB command `target jtag'.

  2. Via a TCP/IP socket to a machine which has the hardware connected,

     or is running the architectural simulator using the standard GDB

     "Remote Serial Protocol". This uses the GDB commands `target

     remote' or `target extended-remote'.

  3. Via a TCP/IP socket to a machine which has the hardware connected,

     or is running the architectural simulator using the custom

     OpenRISC 1000 Remote JTAG protocol. This uses the GDB command

     `target jtag'.

          Note: This connection mechanism is deprecated. It remains for

          backward compatibility only.

     Caution: If used with version 0.2.0 of the architectural

     simulator, Or1ksim, GDB version 6.8 requires a patch to be applied

     to the architectural simulator. This should be available on the

     OpenCores website, or contact the author directly. Only the legacy

     OpenRISC 1000 Remote JTAG Protocol interface is available for this

     version of the architectural simualtor.

     The user is strongly recommended to use Or1ksim 0.3.0 or later,

     since this interfaces directly to GDB using the "Remote Serial

     Protocol".

* Menu:

* Direct JTAG Connection::            Direct connection via a JTAG JP1

                                      interface

* Remote Serial Protocol Connection:: Connection via the GDB Remote

                                      Serial Protocol Interface

* Remote JTAG Connection::            Connection via the OpenRISC 1000 Remote

                                      JTAG Interface

File: or1k.info,  Node: Direct JTAG Connection,  Next: Remote Serial Protocol Connection,  Up: Connecting to the Target

1.1 Direct connection via a JTAG JP1 Interface

==============================================

In this case the the device to which the JP1 header is connected must be

specifed to the `target jtag' command. Typically that will be the

parallel printer port, so the command would be:

     `target jtag /dev/lp'

     Caution: The current author is not aware of anyone using the JP1

     interface. As a result this code has not been tested in the port to

     GDB version 6.8. Modern hardware connections are usually via

     interfaces such as USB, for which the OpenRISC Remote Interface

     can be used (*note Remote JTAG Connection: Remote JTAG

     Connection.).

File: or1k.info,  Node: Remote Serial Protocol Connection,  Next: Remote JTAG Connection,  Prev: Direct JTAG Connection,  Up: Connecting to the Target

1.2 Connection via the GDB Remote Serial Protocol

=================================================

The usual mode of operation is through the GDB "Remote Serial Protocol"

(RSP). This communicates to the target through a TCP/IP socket. The

target must then implement the server side of the interface to drive

either physical hardware (for example through a USB/JTAG connector) or a

simulation of the hardware (such as the OpenRISC Architectural

Simulator).

   Although referred to as a _remote_ interface, the target may actually

be on the same machine, just running in a separate process, with its own

terminal window.

   For example, to connect to the OpenRISC 1000 Architectural

simulator, which is running on machine "thomas" and has been configured

to talk to GDB on port 51000, the following command would be used:

     `target remote thomas:51000'

   The target machine is specified as the machine name and port number.

If the architectural simulator was running on the same machine, its

name may be omitted, thus:

     `target remote :51000'

File: or1k.info,  Node: Remote JTAG Connection,  Prev: Remote Serial Protocol Connection,  Up: Connecting to the Target

1.3 Connection via the OpenRISC 1000 Remote JTAG Interface

==========================================================

Historically, GDB communicated with remote OpenRISC 1000 targets using

a customer protocol, the "OpenRISC 1000 Remote JTAG Interface".

   This protocol is maintained for backwards compatibility, but is now

deprecated. It communicates to the target through a TCP/IP socket. The

target must then implement the client side of the interface to drive

either physical hardware (for example through a USB/JTAG connector) or

a simulation of the hardware (such as the OpenRISC Architectural

Simulator).

   Although referred to as the _remote_ interface, the target may

actually be on the same machine, just running in a separate process,

with its own terminal window.

   For example, to connect to the OpenRISC 1000 Architectural

simulator, which is running on machine "thomas" and has been configured

to talk to GDB on port 50000, I could use the command:

     `target jtag jtag://thomas:50000'

   The target machine is specified after the jtag:// and separated from

the target port by a colon. If the architectural simulator was running

on the same machine, just locahost would suffice as the machine name,

thus:

     `target jtag jtag://localhost:50000'

   Unfortunately there are now two different flavours of the JTAG

interface used with OpenRISC 1000. The original version was created for

use with the OpenRISC 1000 System-on-Chip, ORPSoC. A new (smaller and

simpler) JTAG interface was developed by Igor Mohor in 2004, which is

used on some designs.

   The default behavior of GDB is to use the original ORPSoC version of

the interface for backwards compatibility. GDB can use the Igor Mohor

version by specifying for example:

     `target jtag jtag_mohor://localhost:50000'

   This interface is only available with remote connections using the

legacy OpenRISC 1000 Remote JTAG Protocol (deprecated). The direct JP1

interface can support only the ORPSoC version of JTAG.

   The recommended approach is to use the GDB "Remote Serial Protocol"

which interfaces directly to the simulator, and is independent of the

JTAG implementation used.

   For completeness

     `target jtag jtag_orpsoc://localhost:50000'

   is provided as a synonym for:

     `target jtag jtag://localhost:50000'

   By default, establishing a connection _does not_ reset the target.

This allows debugging to resume a partially complete program on

connection. If a reset is required, the keyworkd `RESET' (case

insensitive) may be added at the end of the `target' command. For

example:

     `target jtag jtag://localhost:50000 reset'

     Warning: The OpenRISC remote JTAG interface is not particularly

     robust. In particular dropping and reconnecting sessions does not

     seem to work well. This was a key factor in its replacement by the

     generic GDB Remote Serial Interface.

File: or1k.info,  Node: OpenRISC 1000 Specific Commands,  Next: OpenRISC 1000 Example,  Prev: Connecting to the Target,  Up: Top

2 Commands just for the OpenRISC 1000

*************************************

The OpenRISC 1000 has one particular feature that is difficult for GDB.

GDB models target processors with a register bank and a block of

memory. The internals of GDB assume that there are not a huge number of

registers in total.

   The OpenRISC 1000 Special Purpose Registers (SPR) do not really fit

well into this structure. There are too many of them (12 groups each

with 2000+ entries so far, with up to 32 groups permitted) to be

implemented as ordinary registers in GDB. Think what this would mean

for the command `info registers all'. However they cannot be considered

memory, since they do not reside in the main memory map.

   The solution is to add two new commands to GDB to see the value of a

particular SPR and to set the value of a particular SPR.

  1. `info spr' is used to show the value of a SPR or group of SPRs.

  2. `spr' is used to set the value of an individual SPR.

* Menu:

* Reading SPRs::            Using the ``info spr'' command

* Writing SPRs::            Using the spr command

File: or1k.info,  Node: Reading SPRs,  Next: Writing SPRs,  Up: OpenRISC 1000 Specific Commands

2.1 Using the `info spr' Command

================================

The value of an SPR is read by specifying either the unique name of the

SPR, or the its group and index in that group. For example the Debug

Reason Register (`DRR', register 21 in group 6 (Debug)) can be read

using any of the following commands:

     `info spr DRR'

     `info spr debug DRR'

     `info spr debug 21'

     `info spr 6 DRR'

     `info spr 6 21'

   In each case the output will be:

     `DEBUG.DRR = SPR6_21 = 0 (0x0)'

   It is also possible to inspect all the registers in a group. For

example to look at all the Programmable Interrupt Controller registers

(group 9), either of the following commands could be used:

     `info spr PIC'

     `info spr 9'

   And the output would be:

     `PIC.PICMR = SPR9_0 = 0 (0x9)'

     `PIC.PICSR = SPR9_2 = 0 (0x8)'

   Indicating that interrupts 0 and 4 are enabled and interrupt 4 is

pending.

File: or1k.info,  Node: Writing SPRs,  Prev: Reading SPRs,  Up: OpenRISC 1000 Specific Commands

2.2 Using the `spr' Command

===========================

The value of an SPR is written by specifying the unique name of the SPR

or its group and index in the same manner as for the `info spr'

command. An additional argument specifies the value to be written. So

for example the Programmable Interrupt Controller mask register could

be changed to enable interrupts 5 and 3 only by any of the following

commands.

     `spr PICMR 0x24'

     `spr PIC PICMR 0x24'

     `spr PIC 0 0x24'

     `spr 9 PICMR 0x24'

     `spr 9 2 0x24'

File: or1k.info,  Node: OpenRISC 1000 Example,  Next: OpenRISC 1000 Limitations,  Prev: OpenRISC 1000 Specific Commands,  Up: Top

3 A Small Example

*****************

A simple "Hello World" program (what else) is used to show the basics

   This is the cannonical small program. Here is the main program and

its two subprograms (added to demonstrate a meaningful backtrace).

     void level2() {

       simexit( 0 );

     }

     void level1() {

       level2();

     }

     main()

     {

       int  i;

       int  j;

       simputs( "Hello World!\n" );

       level1();

     }

   It is linked with a program providing the utility functions

`simexit', `simputc' and `simprints'.

     void  simexit( int  rc )

     {

       __asm__ __volatile__ ( "\tl.nop\t%0" : : "K"( NOP_EXIT ));

     }  /* simexit() */

     void  simputc( int  c )

     {

       __asm__ __volatile__ ( "\tl.nop\t%0" : : "K"( NOP_PUTC ));

     }  /* simputc() */

     void  simputs( char *str )

     {

       int  i;

       for( i = 0; str[i] != '\0' ; i++ ) {

         simputc( (int)(str[i]) );

       }

     }  /* simputs() */

   Finally, a small bootloader is needed, which will be placed at the

OpenRISC reset vector location (0x100) to set up a stack and jump to

the main program.

             .org    0x100           # The reset routine goes at 0x100

             .global _start

     _start:

             l.addi  r1,r0,0x7f00    # Set SP to value 0x7f00

             l.addi  r2,r1,0x0       # FP and SP are the same

             l.mfspr r3,r0,17        # Get SR value

             l.ori   r3,r3,0x10      # Set exception enable bit

             l.jal   _main           # Jump to main routine

             l.mtspr r0,r3,17        # Enable exceptions (DELAY SLOT)

             .org    0xFFC

             l.nop                   # Guarantee the exception vector space

                                     # does not have general purpose code

   This is compiled and linked with the OpenRISC 1000 GNU toolchain.

Note that the linking must specify the bootloader first and use the

`-Ttext 0x0' argument.

   The Or1ksim architectural simulator is configured with memory

starting at location 0x0. The debugging interface is enabled by using a

debug section.

     section debug

       enabled         =          1

       gdb_enabled     =          1

       server_port     =      50000

     end

   The architectural simulator is started in its own terminal window.

If the configuration is in `rsp.cfg', then the command might be:

     `or32-uclinux-sim -f rsp.cfg'

     Reading script file from 'rsp.cfg'...

     Building automata... done, num uncovered: 0/213.

     Parsing operands data... done.

     Resetting memory controller.

     Resetting PIC.

   Note that no program is specified - that will be loaded from GDB.

   In a separate window start up GDB.

     `or32-uclinux-gdb'

   A local copy of the symbol table is needed, specified with the `file'

command.

     Building automata... done, num uncovered: 0/216.

     Parsing operands data... done.

     GNU gdb 6.8

     Copyright (C) 2008 Free Software Foundation, Inc.

     License GPLv3+: GNU GPL version 3 or later 

     This is free software: you are free to change and redistribute it.

     There is NO WARRANTY, to the extent permitted by law.  Type "show copying"

     and "show warranty" for details.

     This GDB was configured as "--host=i686-pc-linux-gnu --target=or32-uclinux".

     (gdb) `file hello'

     Reading symbols from /home/jeremy/svntrunk/GNU/gdb-6.8/progs_or32/hello...done.

     (gdb)

   The connection to the target (the architectural simulator) is then

established, using the port number given in the configuration file.

     (gdb) `target remote :51000'

     Remote debugging using :51000

     0x00000100 in _start ()

     (gdb)

   The program of interest can now be loaded:

     (gdb) `load hello'

     Loading section .text, size 0x1290 lma 0x0

     Loading section .rodata, size 0xe lma 0x1290

     Start address 0x100, load size 4766

     Transfer rate: 5 KB/sec, 238 bytes/write.

     (gdb)

   The program does not immediately start running, since on opening the

connection to the target, Or1ksim stalls.

   All the GDB commands (including the SPR commands are available). For

example

     (gdb) `bt'

     #0  0x00000100 in _start ()

     (gdb) `info spr 0 17'

     SYS.SR = SPR0_17 = 32769 (0x8001)

     (gdb)

   The Supervision Register shows the target is in Supervisor Mode and

that SPRs have User Mode read access.

   _Note._ The supervision register is used to provide the value for the

GDB `$ps' processor status variable, so can also be accessed as:

     (gdb) `print $ps'

     $1 = 32769

     (gdb)

   For this example set a breakpoint at the start of main and then

continue the program

     (gdb) `break main'

     Breakpoint 1 at 0x1264: file hello.c, line 41.

     (gdb) `continue'

     Continuing.

     Breakpoint 1, main () at hello.c:41

     41        simputs( "Hello World!\n" );

     (gdb)

   It is now possible to step through the code:

     (gdb) `step'

     simputs (str=0x1290 "Hello World!\n") at utils.c:90

     90        for( i = 0; str[i] != '\0' ; i++ ) {

     (gdb) `step'

     91          simputc( (int)(str[i]) );

     (gdb) `step'

     simputc (c=72) at utils.c:58

     58        __asm__ __volatile__ ( "\tl.nop\t%0" : : "K"( NOP_PUTC ));

     (gdb)

   At this point a backtrace will show where the code has reached:

     (gdb) `bt'

     #0  simputc (c=72) at utils.c:58

     #1  0x000011cc in simputs (str=0x1290 "Hello World!\n") at utils.c:91

     #2  0x00001274 in main () at hello.c:41

     #3  0x00000118 in _start ()

     (gdb)

   One more step completes the call to the character output routine.

Inspecting the terminal running the Or1ksim simulation, shows the

output appearing:

     JTAG Proxy server started on port 50000

     Resetting PIC.

     H

   Let the program run to completion by giving GDB the continue command:

     (gdb) `continue'

     Continuing.

     Remote connection closed

     (gdb)

   With completion of the program, the terminal running Or1ksim shows

its final output:

     Resetting PIC.

     Hello World!

     exit(0)

     @reset : cycles 0, insn #0

     @exit  : cycles 215892308, insn #215891696

      diff  : cycles 215892308, insn #215891696

   When execution exits (by execution of a `l.nop 1'), the connection

to the target is automatically broken as the simulator exits.

File: or1k.info,  Node: OpenRISC 1000 Limitations,  Next: Copying,  Prev: OpenRISC 1000 Example,  Up: Top

4 Known Problems

****************

There are some known problems with the current implementation

  1. If the OpenRISC 1000 Architecture supports hardware watchpoints,

     GDB will use them to implement hardware breakpoints and

     watchpoints. GDB is not perfect in handling of watchpoints. It is

     possible to allocate hardware watchpoints and not discover until

     running that sufficient watchpoints are not available. It is also

     possible that GDB will report watchpoints being hit spuriously.

     This can be down to the assembly code having additional memory

     accesses that are not obviously reflected in the source code.

  2. The remote JTAG connection is not robust to being interrupted, or

     reconnecting. If the connection is lost due to error, then you

     must restart GDB and the target server (for example the Or1ksim

     architectural simulator). Moving to the Remote Serial Protocol is

     intended to remedy this problem in the future.

  3. The OpenRISC 1000 architecture has evolved since the port of GDB

     5.3 in 2001. In particular the structure of the Unit Present

     register has changed and the CPU Configuration register has been

     added. The port of GDB version 6.8 uses the _current_

     specification of the OpenRISC 1000. This means that old clients

     that talk to the debugger may not work. In particular the Or1ksim

     Architectural simulator requires a patch to work.

  4. The handling of watchpoints in the Or1ksim architectural simulator

     was incorrect. To work with GDB 6.8, a patch is required to fix

     this problem. This is combined with the patch changing the

     structure of the Unit Present and CPU Configuration registers.

  5. The OpenRISC 1000 architecture uses its General Purpose Register

     (GPR) 2 as a frame pointer register. However the `$fp' variable in

     GDB is not currently implemented, and will return the value of the

     stack pointer (GPR 1) instead.

   Reports of bugs are much welcomed. Please report problems through the

OpenCORES tracker at `www.opencores.org/ptracker.cgi/list/or1k'.

File: or1k.info,  Node: Copying,  Next: GNU Free Documentation License,  Prev: OpenRISC 1000 Limitations,  Up: Top

Appendix A GNU GENERAL PUBLIC LICENSE

*************************************

                         Version 2, June 1991

     Copyright (C) 1989, 1991 Free Software Foundation, Inc.

     51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.

     Everyone is permitted to copy and distribute verbatim copies

     of this license document, but changing it is not allowed.

Preamble

========

The licenses for most software are designed to take away your freedom

to share and change it.  By contrast, the GNU General Public License is

intended to guarantee your freedom to share and change free

software--to make sure the software is free for all its users.  This

General Public License applies to most of the Free Software

Foundation's software and to any other program whose authors commit to

using it.  (Some other Free Software Foundation software is covered by

the GNU Library General Public License instead.)  You can apply it to

your programs, too.

   When we speak of free software, we are referring to freedom, not

price.  Our General Public Licenses are designed to make sure that you

have the freedom to distribute copies of free software (and charge for

this service if you wish), that you receive source code or can get it

if you want it, that you can change the software or use pieces of it in

new free programs; and that you know you can do these things.

   To protect your rights, we need to make restrictions that forbid

anyone to deny you these rights or to ask you to surrender the rights.

These restrictions translate to certain responsibilities for you if you

distribute copies of the software, or if you modify it.

   For example, if you distribute copies of such a program, whether

gratis or for a fee, you must give the recipients all the rights that

you have.  You must make sure that they, too, receive or can get the

source code.  And you must show them these terms so they know their

rights.

   We protect your rights with two steps: (1) copyright the software,

and (2) offer you this license which gives you legal permission to copy,

distribute and/or modify the software.

   Also, for each author's protection and ours, we want to make certain

that everyone understands that there is no warranty for this free

software.  If the software is modified by someone else and passed on, we

want its recipients to know that what they have is not the original, so

that any problems introduced by others will not reflect on the original

authors' reputations.

   Finally, any free program is threatened constantly by software

patents.  We wish to avoid the danger that redistributors of a free

program will individually obtain patent licenses, in effect making the

program proprietary.  To prevent this, we have made it clear that any

patent must be licensed for everyone's free use or not licensed at all.

   The precise terms and conditions for copying, distribution and

modification follow.

    TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION

  0. This License applies to any program or other work which contains a

     notice placed by the copyright holder saying it may be distributed

     under the terms of this General Public License.  The "Program",

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     the Program" means either the Program or any derivative work under

     copyright law: that is to say, a work containing the Program or a

     portion of it, either verbatim or with modifications and/or

     translated into another language.  (Hereinafter, translation is

     included without limitation in the term "modification".)  Each

     licensee is addressed as "you".

     Activities other than copying, distribution and modification are

     not covered by this License; they are outside its scope.  The act

     of running the Program is not restricted, and the output from the

     Program is covered only if its contents constitute a work based on

     the Program (independent of having been made by running the

     Program).  Whether that is true depends on what the Program does.

  1. You may copy and distribute verbatim copies of the Program's

     source code as you receive it, in any medium, provided that you

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     copyright notice and disclaimer of warranty; keep intact all the

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     You may charge a fee for the physical act of transferring a copy,

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  2. You may modify your copy or copies of the Program or any portion

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       b. You must cause any work that you distribute or publish, that

          in whole or in part contains or is derived from the Program

          or any part thereof, to be licensed as a whole at no charge

          to all third parties under the terms of this License.

       c. If the modified program normally reads commands interactively

          when run, you must cause it, when started running for such

          interactive use in the most ordinary way, to print or display

          an announcement including an appropriate copyright notice and

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          provide a warranty) and that users may redistribute the

          program under these conditions, and telling the user how to

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          to print an announcement.)

     These requirements apply to the modified work as a whole.  If

     identifiable sections of that work are not derived from the

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     whole which is a work based on the Program, the distribution of

     the whole must be on the terms of this License, whose permissions

     for other licensees extend to the entire whole, and thus to each

     and every part regardless of who wrote it.

     Thus, it is not the intent of this section to claim rights or

     contest your rights to work written entirely by you; rather, the

     intent is to exercise the right to control the distribution of

     derivative or collective works based on the Program.

     In addition, mere aggregation of another work not based on the

     Program with the Program (or with a work based on the Program) on

     a volume of a storage or distribution medium does not bring the

     other work under the scope of this License.

  3. You may copy and distribute the Program (or a work based on it,

     under Section 2) in object code or executable form under the terms

     of Sections 1 and 2 above provided that you also do one of the

     following:

       a. Accompany it with the complete corresponding machine-readable

          source code, which must be distributed under the terms of

          Sections 1 and 2 above on a medium customarily used for

          software interchange; or,

       b. Accompany it with a written offer, valid for at least three

          years, to give any third party, for a charge no more than your

          cost of physically performing source distribution, a complete

          machine-readable copy of the corresponding source code, to be

          distributed under the terms of Sections 1 and 2 above on a

          medium customarily used for software interchange; or,

       c. Accompany it with the information you received as to the offer

          to distribute corresponding source code.  (This alternative is

          allowed only for noncommercial distribution and only if you

          received the program in object code or executable form with

          such an offer, in accord with Subsection b above.)

     The source code for a work means the preferred form of the work for

     making modifications to it.  For an executable work, complete

     source code means all the source code for all modules it contains,

     plus any associated interface definition files, plus the scripts

     used to control compilation and installation of the executable.

     However, as a special exception, the source code distributed need

     not include anything that is normally distributed (in either

     source or binary form) with the major components (compiler,

     kernel, and so on) of the operating system on which the executable

     runs, unless that component itself accompanies the executable.

     If distribution of executable or object code is made by offering

     access to copy from a designated place, then offering equivalent

     access to copy the source code from the same place counts as

     distribution of the source code, even though third parties are not

     compelled to copy the source along with the object code.

  4. You may not copy, modify, sublicense, or distribute the Program

     except as expressly provided under this License.  Any attempt

     otherwise to copy, modify, sublicense or distribute the Program is

     void, and will automatically terminate your rights under this

     License.  However, parties who have received copies, or rights,

     from you under this License will not have their licenses

     terminated so long as such parties remain in full compliance.

  5. You are not required to accept this License, since you have not

     signed it.  However, nothing else grants you permission to modify

     or distribute the Program or its derivative works.  These actions

     are prohibited by law if you do not accept this License.

     Therefore, by modifying or distributing the Program (or any work

     based on the Program), you indicate your acceptance of this

     License to do so, and all its terms and conditions for copying,

     distributing or modifying the Program or works based on it.

  6. Each time you redistribute the Program (or any work based on the

     Program), the recipient automatically receives a license from the

     original licensor to copy, distribute or modify the Program

     subject to these terms and conditions.  You may not impose any

     further restrictions on the recipients' exercise of the rights

     granted herein.  You are not responsible for enforcing compliance

     by third parties to this License.

  7. If, as a consequence of a court judgment or allegation of patent

     infringement or for any other reason (not limited to patent

     issues), conditions are imposed on you (whether by court order,

     agreement or otherwise) that contradict the conditions of this

     License, they do not excuse you from the conditions of this

     License.  If you cannot distribute so as to satisfy simultaneously

     your obligations under this License and any other pertinent

     obligations, then as a consequence you may not distribute the

     Program at all.  For example, if a patent license would not permit

     royalty-free redistribution of the Program by all those who

     receive copies directly or indirectly through you, then the only

     way you could satisfy both it and this License would be to refrain

     entirely from distribution of the Program.

     If any portion of this section is held invalid or unenforceable

     under any particular circumstance, the balance of the section is

     intended to apply and the section as a whole is intended to apply

     in other circumstances.

     It is not the purpose of this section to induce you to infringe any

     patents or other property right claims or to contest validity of

     any such claims; this section has the sole purpose of protecting

     the integrity of the free software distribution system, which is

     implemented by public license practices.  Many people have made

     generous contributions to the wide range of software distributed

     through that system in reliance on consistent application of that

     system; it is up to the author/donor to decide if he or she is

     willing to distribute software through any other system and a

     licensee cannot impose that choice.

     This section is intended to make thoroughly clear what is believed

     to be a consequence of the rest of this License.

  8. If the distribution and/or use of the Program is restricted in

     certain countries either by patents or by copyrighted interfaces,

     the original copyright holder who places the Program under this

     License may add an explicit geographical distribution limitation

     excluding those countries, so that distribution is permitted only

     in or among countries not thus excluded.  In such case, this

     License incorporates the limitation as if written in the body of

     this License.

  9. The Free Software Foundation may publish revised and/or new

     versions of the General Public License from time to time.  Such

     new versions will be similar in spirit to the present version, but

     may differ in detail to address new problems or concerns.

     Each version is given a distinguishing version number.  If the

     Program specifies a version number of this License which applies

     to it and "any later version", you have the option of following

     the terms and conditions either of that version or of any later

     version published by the Free Software Foundation.  If the Program

     does not specify a version number of this License, you may choose

     any version ever published by the Free Software Foundation.

 10. If you wish to incorporate parts of the Program into other free

     programs whose distribution conditions are different, write to the

     author to ask for permission.  For software which is copyrighted

     by the Free Software Foundation, write to the Free Software

     Foundation; we sometimes make exceptions for this.  Our decision

     will be guided by the two goals of preserving the free status of

     all derivatives of our free software and of promoting the sharing

     and reuse of software generally.

                                NO WARRANTY

 11. BECAUSE THE PROGRAM IS LICENSED FREE OF CHARGE, THERE IS NO

     WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY APPLICABLE

     LAW.  EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT

     HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM "AS IS" WITHOUT

     WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT

     NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND

     FITNESS FOR A PARTICULAR PURPOSE.  THE ENTIRE RISK AS TO THE

     QUALITY AND PERFORMANCE OF THE PROGRAM IS WITH YOU.  SHOULD THE

     PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY

     SERVICING, REPAIR OR CORRECTION.

 12. IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN

     WRITING WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY

     MODIFY AND/OR REDISTRIBUTE THE PROGRAM AS PERMITTED ABOVE, BE

     LIABLE TO YOU FOR DAMAGES, INCLUDING ANY GENERAL, SPECIAL,

     INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OR

     INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF

     DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU

     OR THIRD PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY

     OTHER PROGRAMS), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN

     ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.

                      END OF TERMS AND CONDITIONS

How to Apply These Terms to Your New Programs

=============================================

If you develop a new program, and you want it to be of the greatest

possible use to the public, the best way to achieve this is to make it

free software which everyone can redistribute and change under these

terms.

   To do so, attach the following notices to the program.  It is safest

to attach them to the start of each source file to most effectively

convey the exclusion of warranty; and each file should have at least

the "copyright" line and a pointer to where the full notice is found.