I want to write a BIOS debugger.Can you give me some advice?

[王海明]

hi , all,
      I am a postgraduate student of Beijing University of Aeronautics and Astronautics ( in china , Beijing).
     I want to write a BIOS debugger as my graduation article.
     My plan are as follow:
      1. firstly I want to write a debug stub which is INDEPENDENT of specific Mainchips,
    	and  small enough. The stub can set up a basic environment ( such as  RAM 
        initialization,	uart initialization). It can also communicate with the develop PC  
        through Serial port,and excute the debug command transfered by the develp PC.
     2. write a source debugger	.
                                                     ---------
                                                    |         |
     --------------------------       serial port   | develop |
     | BIOS       |debug stub | ----<---->--------- |   pc    |
　　 --------------------------                     -----------
                                                       | |
                                                ------------------

the system figure

I appreciate some advice about the possibility of my plan .

best regards!			
　　　　　　　　　　　　yours　Haiming Wang
                             　王海明
　　　　　　　　　　　　　　[e-mail]
　　　　　　　　　　　　　　　　　2002-10-30

[Adam Sulmicki]

> firstly I want to write a debug stub which is INDEPENDENT of specific
>
> Mainchips, and small enough. The stub can set up a basic environment (
> such as RAM initialization, uart initialization). It can also
> communicate with the develop PC through Serial port,and excute the debug
> command transfered by the develp PC.

I don't belive there's such thing as "chipset independent ram
initalization". other than what what you descriped pretty much summarizes
what LinuxBIOS is.
> 2. write a source debugger	.
>                                                  ---------
>                                                 |         |
>  --------------------------       serial port   | develop |
>  | BIOS       |debug stub | ----<---->--------- |   pc    |
>
> ���� --------------------------                     -----------
>                                                        | |
>                                                 ------------------
>             the system figure

have you tried out bochs? It seems to me it may do pretty much what u
want. Although it will put your problem sort of upside down where the
burden will be to ensure accurate hardware representation by bochs.

just my two bits.

[Jeremy Jackson]

I think this is an excellent idea.  I have thought thought about this
myself also.

I was looking at taking kgdb kernel debugger stub and moving it
from the Linux kernel into LinuxBIOS.  It would have the advantage that
it could trap some hardware events that cause a reset, which are currently
overwritten or cleared by the PC BIOS upon reset.  A LinuxBIOS debugger
could save some extra machine state and send it out the debug (serial) port.
This functionality is related to implementing power management in
LinuxBIOS -
things like STR (suspend to ram) require a reset vector handler that is
more intelligent.

A BIOS debugger could also make use of the hardware Break/SMI button to
bring
up the debugger, even if keyboard and serial port are not responding.

I would find such a system useful.  I would encourage you to use existing
debuggers
if possible (kgdb, or kdb) since the source level debuggers already exist
for these
(ie emacs) and the project could be completed sooner.

Regards,

Jeremy

----- Original Message -----
From: "王海明" 
To: 
Sent: Tuesday, October 29, 2002 11:51 AM
Subject: I want to write a BIOS debugger.Can you give me some advice?
> hi , all,
>       I am a postgraduate student of Beijing University of Aeronautics and

Astronautics ( in china , Beijing).
> I want to write a BIOS debugger as my graduation article.
> My plan are as follow:
>       1. firstly I want to write a debug stub which is INDEPENDENT of

specific Mainchips,
> and  small enough. The stub can set up a basic environment ( such as  RAM
>         initialization, uart initialization). It can also communicate with

the develop PC
>     through Serial port,and excute the debug command transfered by the

develp PC.
> write a source debugger .
>                                              |         |
> --------------------------       serial port   | develop |
>   | BIOS       |debug stub | ----<---->--------- |   pc    |
>
> --------------------------                     -----------
>                                                        | |
>                                                 ------------------
>             the system figure
>
> I appreciate some advice about the possibility of my plan .
>
>
>
>   best regards!
>
> yours　Haiming Wang
>                              　王海明
> 　　　　　　　　　　　　　　[e-mail]
> 　　　　　　　　　　　　　　　　　2002-10-30
> _______________________________________________
> Linuxbios mailing list
> [e-mail]
> http://www.clustermatic.org/mailman/listinfo/linuxbios

������  writes:
> hi , all,
>       I am a postgraduate student of Beijing University of Aeronautics and
> Astronautics ( in china , Beijing).
> I want to write a BIOS debugger as my graduation article.
> My plan are as follow:
>   1. firstly I want to write a debug stub which is INDEPENDENT of specific
>
> Mainchips,
> and small enough. The stub can set up a basic environment ( such
>
> as RAM
>     initialization, uart initialization). It can also communicate with the
>
> develop PC
>     through Serial port,and excute the debug command transfered by the
>
> develp PC.

As has been previously mentioned
> 2. write a source debugger	.
>                                                  ---------
>                                                 |         |
>  --------------------------       serial port   | develop |
>  | BIOS       |debug stub | ----<---->--------- |   pc    |
>
> ���� --------------------------                     -----------
>                                                        | |
>                                                 ------------------
>             the system figure
>
> I appreciate some advice about the possibility of my plan . 	

LinuxBIOS initializes the ram, and a few other hardware devices and that
is it.  So if you want to write a debugger for that there is some
interesting work to do.  If you want to write a debugger for firmware
services that are active after the initial hardware setup that is a
different problem.  Currently LinuxBIOS provides none of those.

Ram initialization is the single hard dest driver to write for LinuxBIOS.
Short of an ICE I don't think you are going to get a debugger in
there.  An emulator like bochs would could work, but it an emulator
may not reproduce the bugs that are visible in real life.  A debugger
is useful for is looking around and dumping the state at a given
point.  That we can do moderately well with modifing the source code.

What would be truly advantageous is a mini-C compiler that would
compile code that would exclusively use the registers, not memory, and
allow either inline assembly or builtin operations for all of a
processors special instructions.  The biggest debugging problem I have
seen is when you add debugging code a register is accidentally
stomped.  If it was possible to write the initial startup code in a
high level language it would be much easier to debug and maintain.

On the subject of firmware services, there are projects underway to
build a backwards compatiblity layer for LinuxBIOS.  If what you are
really after are debugging firmware services, I would recommend
playing with etherboot.  The larger target would be stubs that you can
stick in a moderately random static ELF executable.   But I am fairly
certain this is just what is done on embedded targets and is not
really new ground.

Eric