File I/O Monitoring with the Debugger

[ripper713]

Hi All:
I am currently trying to use the debugger in pSX V1.3 to reverse engineer the file formats used in the PSX game Lunar: Silver Star Story Complete. Presently, I am trying to break on file I/O related bios (system) calls but am having very little success. Does anyone have any tips? I have execution break points at 0x000000A0 and 0x000000B0 and am checking the value of R9 to identify the called functions but this does not seem to be working as the appropriate sub-functions (openfile, read from file, etc.) do not seem to be called but we all know that the exe needs to read the files somehow. Are there other ways to monitor File I/O? Any help would be greatly appreciated.

[pSX Author]

Most games do not use the standard file functions - they usually access the CD directly (which was done by linking to a library).

[Squaresoft74]

Dunno if this fully help you but here you go :

CaitSith2 said:

Lunadata.fil filing system format, as found on the lunadata.fil file, located on the lunar sssc cds.

First 32 bytes - Header
offset len purpose
0x00 1 equals 0x2E, purpose unknown.
0x01 19 equals 0x00, possibly reserved area.
0x14 4 Number of Files (numfiles)
0x18 4 Length of this data file
0x1C 4 unknown area, possibly reserved.

Next numfiles*32 bytes
for each file entry
0x00 20 File name
0x14 4 image cluster number where file is, each cluster is 0x800 bytes.
if even 1 byte of the cluster is used, the remaining 0x7FF bytes
is wasted.
0x18 4 Actual length of file
0x1C 4 purpose unknown


Just like a hard drive, the file is arranged into clusters.


Now that I know the filing system, I can write a program to extract all of the game data from the image file,
including the SEQ/VAB data.


Format of *.snd files

Do until EOF
Skip 4 bytes
Read next 4 bytes, to determine length of data
Read next len bytes.
Loop.

Files are arranged in this order

Vab Header
Vab Body
SEQ data

end of *.snd files

This can be found among other notes in the Lunar SSSC PSF set made by CaitSith2.

[ripper713]

Thank you for the advice. While I will eventually need the sound files (I am making a small RPG game and figured I would clone the beginning of this game because my artistic ability is lacking), at present, I am primarily looking for text, graphics, and animation sequences (not the movies but sprite movements). I will look into tracking direct CD access and move my break points over to the memory read type. I had already figured out how to extract all of the files from lunadata.fil but I am currently trying to figure out what to do with them as none of the graphics utilities that I have tried can figure them out. Even the file called insert.tim is not being identified as a TIM file so maybe some encryption or compression is being done. Lastly, if you are interested, I think the last 4 bytes in the file list entries is a time_t structure. Open the file in Hex Workshop and all of the files have dates ranging from 1996 to 1999 (the US version was released in mid 1999) with most listing 1998. Thank you again.