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start of contribution guide #99

Merged
2 commits merged into from
Jun 29, 2018
Merged

start of contribution guide #99

2 commits merged into from
Jun 29, 2018

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ttdonovan
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From this issue #84 I've stated a contribution guide. Feel free to make any changes. Other things that might be useful are screenshots or a video explaining how to reverse an example function.

There are also a couple of #TODOs that could use some polishing to further explain concepts.

mewmew
mewmew reviewed Jun 29, 2018
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Thanks @ttdonovan. Great start of the contribution docs. We can keep evolving these docs as the project progresses.

Added some comments, mostly typos.

CONTRIBUTE.md Outdated

## How To...

Described below are steps for using the IDA and SYM to reverse the Diablo
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-and SYM to
+and SYM files to

CONTRIBUTE.md Outdated

* A clean installation of Diablo patched to version 1.09b (Diablo.exe)
* Download IDA (Interactive Disassembler) [Hex-Rays](https://www.hex-rays.com/products/ida/support/download_freeware.shtml)
* Download IDC script from sancturary/notes repository: [notes.idc](http://sanctuary.github.io/notes/notes.idc)
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-sancturary
+sanctuary

CONTRIBUTE.md Outdated
Described below are steps for using the IDA and SYM to reverse the Diablo
source.

### Understanding Devilusion and Sancutary Notes
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-Devilusion
+Devilution
-Sancutary
+Sanctuary

CONTRIBUTE.md Outdated

### Understanding Devilusion and Sancutary Notes

Both Devilution and the Sancutary Notes repo have the intended aim to get as
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-Sancutary
+Sanctuary

CONTRIBUTE.md Outdated
See for instance [drlg_l1_load_dun](http://sanctuary.github.io/notes/#function/drlg_l1_load_dun),
which is defined in `drlg_l1.cpp`. This function has the PSX signature
`void LoadL1Dungeon__FPcii(char *sFileName, int vx, int vy)`, but is documented
in the Sancutary Notes repo as follows for consistency:
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-Sancutary
+Sanctuary

CONTRIBUTE.md Outdated
* Processor type i386 (80386)
* Run the IDC script in IDA on the fresh IDB database to import names for
variables and functions, type definitions, etc. (Note: run the IDC script
only on new IDB databases as it removes all variable names before adding new
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-only
+**only**

to put emphasis that this is an important notice.

CONTRIBUTE.md Outdated

### About the SYM

The diasurgical/scalpel includes a copy of a symbolic file was accidentally
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-The diasurgical/scalpel includes a copy of a symbolic file was accidentally
+The diasurgical/scalpel repository includes a copy of a symbolic file that was accidentally

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mewmew commented Jun 29, 2018

@galaxyhaxz Would you like to add notes for how to open the diabpsx.bin executable from the Diablo (Japan) [SLPS-01416] release? The steps are fairly involved, as the file is loaded as raw.

Our current notes are as follows,

  1. Processor type: MIPS R5900 (Sony Playstation 2) little endian
  2. ok
  3. ROM: ROM start address: 0x80010000
  4. Input file: Loading address: 0x80010000
  5. File -> Load file -> Another binary file: pregame.bin
  6. Loading segment: 0x8001000 (in paragraphs)
  7. Loading offset: 0x129BF8 (0x80139BF8-0x80010000)

We should probably extend these steps by mentioning that the same address of the .SYM files may map to more than one function, as only one of fmv.bin, frontend.bin, game.bin, or pregame.bin may be loaded at once, and they are loaded at the same base address.

From #84 (comment), this could be tidied up a bit and added to the CONTRIBUTE.md documentation.

Load diabpsx.bin executable in IDA and explore :) You may also want to extract the lump.bin archive to be able to load fmv.bin, frontend.bin, game.bin, or pregame.bin shared libraries. Note, only one of these libraries is loaded at any one time, the reason probably being that Playstation 1 had very limited memory. For notes on what each address maps to in the PSX release, refer to scalpel.

We may also want to mention how to map global variable accesses relative to $gp, e.g.

# How to calculate global variable addresses in MIPS

$gp = 0x8011A780

## Example from drlg_l1.cpp___L5firstRoom(void)

seg003:8013D9C4                 sb      $zero, 0x215A($gp)

address: 0x8011A780 + 0x215A = 0x8011C8DA

sbss:8011C8DA HR3:            .space 1                 # PSX ref: 0x8011C8DA
sbss:8011C8DA                                          # PSX def: unsigned char HR3

heinermann
heinermann reviewed Jun 29, 2018
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CONTRIBUTE.md Outdated
* Function arguments `(char *dun_path, int view_x, int view_y)`
* #TODO whatelse can be inferred from below?

```
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Can probably syntax highlight using asm

@ttdonovan
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I've corrected the typos in the CONTRIBUTE.md

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ghost commented Jun 29, 2018

Indeed there is a lot to reversing the PSX module. I'll add some more notes on that, and how to annotate function variables based on the symbol file. This is a good start though!

@ghost ghost merged commit 4881ed2 into diasurgical:master Jun 29, 2018
@ttdonovan ttdonovan deleted the contribute branch July 3, 2018 19:18
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