[LinuxBIOS] VGA BIOS dissect.sh

[Leon Woestenberg]

Hello again Ronald,

Ronald G Minnich wrote:
> Leon Woestenberg wrote:
>> Hello,
>>
>> I found this script to be helpful to me in getting a VGA BIOS binary 
>> for my EPIA.
>
>
> hi leon, you have a working via with linuxbios, vga, etc? Have you 
> made ANY local mods to the source tree?
Concerning VGA BIOS, did you note my sidenote in my earlier mail (copied 
below again)?

Dumbly following the HOWTO (which has a subtle bug) is not adviced:

---

As a sidenote, I think the HOWTO/EPIA-M is wrong about how to extract:

WRONG: dd if=/dev/mem of=/video.bios.bin \
WRONG: bs=1 count=65536 skip=790528

Note that 790528=0xC1000 and 65536=0x10000

/dev/mem must be read from 0xC000-0xD000 (VGA BIOS), whereas /proc/kcore 
must be read from
0xC1000-0xD1000 because kcore is an ELF 'view' to the memory, with a 
0x1000 ELF header at 0xC000.

What I did is extract from 0xC000-0xD000 as follows:
dd if=/dev/mem of=/113mem.bin skip=1536 count=128
(bs=512 by default)
---</sidenote>---

leon at nehemiah <http://www.openbios.org/mailman/listinfo/linuxbios>:/$ ls -ald /113mem.bin
-rw-r--r--  1 root root 65536 2006-02-23 03:57 /113mem.bin

leon at nehemiah <http://www.openbios.org/mailman/listinfo/linuxbios>:/$ hexdump -C /113mem.bin | head -n 10
00000000  55 aa 7d e9 26 7f 5e 1b  fa f9 f4 82 00 00 00 00  
|/U.}.&.^.........|
/00000010  00 00 00 00 00 00 00 00  44 00 d4 b0 c6 00 49 42  
|/........D.....IB|
/00000020  4d 20 43 4f 4d 50 41 54  49 42 4c 45 42 43 50 4f  |M 
COMPATIBLEBCPO|
00000030  53 54 00 00 18 00 30 34  2f 31 38 2f 30 33 01 15  
|/ST....04/18/03..|
/00000040  00 c0 c6 00 50 43 49 52  06 11 22 31 00 00 18 00  
|/....PCIR.."1....|
/00000050  00 00 00 03 40 00 51 01  00 80 00 00 00 01 20 20  
|/.... at .Q....... <http://www.openbios.org/mailman/listinfo/linuxbios>  |
/00000060  20 56 49 41 20 54 65 63  2e 49 6e 63 2e 20 20 20  | VIA 
Tec.Inc.   |
00000070  20 20 20 20 20 20 20 20  20 56 45 52 2e 56 54 33  |         
VER.VT3|
00000080  31 32 33 20 20 20 20 01  15 01 12 56 49 41 20 20  |123    
....VIA  |
00000090  20 20 20 20 20 20 20 20  20 20 20 20 00 00 00 00  |            
....|

leon at nehemiah <http://www.openbios.org/mailman/listinfo/linuxbios>:/$ md5sum /113mem.bin
87017abc14c53e51a269fe59b5ba1508  /113mem.bin

---

Regards,

Leon.