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Hi, I'm back!
After a lot of silent backstage work I decided to share with you my research about Pokemon White 2 Game original code.
I decided to analyze White 2 because it's more structured than DPP, HGSS and also because Bond of projectpokemon gives a good database to start. I use IDA pro SDK 6.1 + a little plugin developed by Ludde and edited by me to generate pseudocode from ARM Thumb instructions (It's not perfect but It's very useful)
But now no more chatting!
Basic Idea
Like other NDS Rom games, W2 uses arm9.bin file to execute main game code and overlays files to load additional functions/structures. There is in particular a table that give us the loading addresses for each overlay (We have overlapping addresses, so we can't use a unique binary file to analyze all the overlays)
I try to divide the assembly file in "logical" blocks, and each block have a general structure and a series of functions.
Note: It may be contains mistakes!
Now, the arm9.bin file can be divided in these different "structure-functions" block (We uses as base address: 0x2000000, that is the main RAM address)
Legend:
o.h = Original C file Header
s.f = Save File
0x2000400 - 0x20057F0 Nintendo DS Generic OS Functions
Hi Bond, I've already your database (I work hardly on it for 1-2 years, finding a bunch of new functions).
I know that White 2 uses only a series of structures, with functions that operate in these structures. I called it wrongly "classes", it's only a naming convention.
I fixed the addresses, thanks!
Hi, guys!
As I promise, we start analyze ASM blocks from binary file of White 2 code.
For now we skip the first two "sections" (I wanna start with some "easy" to understand)
As I define previously, from offset 0x2006D64 to 0x2006EE8 we have all the functions linked with original snd_mic.c source file.
In particular we have:
loc_2006DCE
LDR R0, =micBlock
STR R4, [R0]
POP {R3-R7,PC}
Now we analyze step by step the ARM-to-PseudoCode conversion (I move some istructions from the original position to other to make a more clear traslation)
This operation pushes the registers used by the function onto the stack. We can skip during conversion, because this operation is "invisible" at pseudocode level
//Alloc block into memory filled with 00, with size of 0x2014 byte and save pointer into field_24 of micBlock structure)
micBlock.field_24 = MEM_CpuAllocBlock8(MEM_AllocBlock(groupID,0x2014,0,aSnd_mic_c),0,0x2014)
//Turn on the NDS Amplificator system?
PM_SetAmp(1)
//Set the gain of the NDS Amplificatore system?
PM_SetAmpGainAsync(2)
MicInit()
//Call a DSI function. I don't know what this part really do.
if (OS_CheckIsDSI == 1)
The next function is the "destructor" (a particular function that destroy the structure and free the memory)
The original ASM code of this function is:
As you can see, most of the code is little obscure yet, so I appreciate any suggestion on what it really do.
I stop here for now, because I wanna know If this approach is useful for you or not.
Stay tuned!
