ADLO: linuxbios v1 hangs after jumping to boot code at 0x7c00

Richard Smith rsmith at
Tue Jul 13 20:07:01 CEST 2004

Simon Xin Cheng wrote:

> I am trying to use ADLO + video bios to enable VGA support for my EPIA 800
> board. Unfortunately, the code hangs after the elfboot "Jumping to boot
> code at 0x7c00 "
> According to ADLO document, I enabled the original bios shadow from C0000
> to DFFFF and capture the vedio bios by:

Make sure your shadowing is enable correctly.  You want to read from the 
  bios chip and write to RAM.  Then enable the full shadow of that location.

>  dd if=/proc/kcore of=/usr/src/video.bios.bin bs=1 count=65536 skip=790528

Examine this file and see if it has the BIOS extension signature of 
0xaa55 (or 0x55aa depending on what endian you view it as)  You should 
also see some text iding the bios.

> By the way, how to debug ADLO?

In ./util/ADLO/bochs/bios/rombios.c there should be a #define 
DEBUG_SERIAL.  Set that to 1 and all of the bios messages will go out 
the serial port.  Note you have to disable it to get video since it 
bypases screenwrites.

DEBUG_SERIAL is from a patch but I don't know if it make it into CVS. 
If you don't have a DEBUG_SERIAL then search the archives for the patch. 
  If you can't find it then let me know and I'll see about generating 
one for you.

rombios.c also has lots of debug options as well look at the source.

One thing to note is that if you do any hacking on the assembly in 
rombios.c you must be very careful about shifting the positions of all 
the bios entry points.     A single instrution in some of those assembly 
blocks will break all the bios entry points.

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