The Day I Reverse Engineered a Gameboy Advance Game (Coding Portugal meetup)

Gameboy Advance was one of the most popular video game platforms of its time and, because of it, many people worked together as a community to study and to document its architecture and develop ROM hacking and other interesting tools.

It turns out that this video game is a fantastic way to start studying reverse engineering: its architecture is very well documented and simpler if compared to the current game console generation – and, of course, it is very fun to work in a game-related project.

So... what do you think of learning reverse engineering through this challenge: developing a level editor for a GBA game called "Klonoa: Empire of Dreams"?
We need to understand the architecture behind ARM hardware, apply reverse engineering in order to discover how the logic of the game works, and then use our front-end knowledge (JS + React.js) to build a level editor.

Transcript

1. The day I reverse engineered a Gameboy Advance game With @macabeus
2. WTF?! THE DAY I REVERSE ENGINEERED A GAMEBOY ADVANCE GAME
3. soooo…
5. This is me
6. This is my friend
7. This is US PLAYING KLONOA
8. This is US PLAYING KLONOA
9. This is US PLAYING KLONOA
10. But we were bored
11. soooo…
12. I want MORE LEVELS TO PLAY WITH
13. WANTED DIFFERENT LEVELS
14. soooo…
15. soooo…
16. soooo…
17. soooo…AND THIS IS KLONNOA
18. soooo…AND THIS IS KLONNOA
22. http://bit.ly/klo-gba-js-repo
23. Stretching the bridge THE DAY I REVERSE ENGINEERED A GAMEBOY ADVANCE GAME
24. https://www.nogba.com
25. https://www.hex-rays.com/products/ida
28. This is the tile ID. In this example, all tiles with the ID 9B are exactly the bridge part, which is the left corner. 9A is the ID of the continuous part of the bridge.
29. This tells us where the tile is stored in the memory. In this example, it is at 0600F1AD.
30. https://www.coranac.com/tonc/text/hardware.htm
31. https://www.coranac.com/tonc/text/hardware.htm The address found is expected 0600F1AD given that everything between 0600 and 0601 is part of the section known as VRAM.
32. Our bridge starts here!
33. Our bridge starts here!
34. And now we grow it bigger!
35. And now we grow it bigger!
36. And now we grow it bigger! WTF??!
37. Understanding the DMA THE DAY I REVERSE ENGINEERED A GAMEBOY ADVANCE GAME
40. VRAM pulls the tilemap
 containing exactly what the player has to see from somewhere else that has the entire thing.
41. https://www.coranac.com/tonc/text/regbg.htm
42. https://www.coranac.com/tonc/text/regbg.htm Direct Memory Access
43. https://www.coranac.com/tonc/text/regbg.htm It is a feature of computer systems that allows certain hardware subsystems to access main system memory (random- access memory), independent of the CPU
44. https://www.coranac.com/tonc/text/regbg.htm tldr; a faster copy and paste
45. DMA3: 03000900 0600E000 80000400 DMA3: 03001100 0600E800 80000400 DMA3: 03004DB0 0600F000 80000200 DMA3: 03004800 07000000 84000048
46. DMA3: 03000900 0600E000 80000400 DMA3: 03001100 0600E800 80000400 DMA3: 03004DB0 0600F000 80000200 DMA3: 03004800 07000000 84000048 The closest to the bytes of our bridge (0600F1AD).
47. DMA3: 03000900 0600E000 80000400 DMA3: 03001100 0600E800 80000400 DMA3: 03004DB0 0600F000 80000200 DMA3: 03004800 07000000 84000048 This address is the VRAM data source. It’s located in a region called Fast WRAM.
49. Our bridge starts here!
50. Stretching it…
51. Stretching it… …It works! And…
52. Stretching it… …It works! And… WTF??!
53. Stretching it… …It works! And… WTF??!
56. Our extra tiles disappear when out of the player vision range.
57. LET’S TALK ABOUT PHYSICS THE DAY I REVERSE ENGINEERED A GAMEBOY ADVANCE GAME
58. Object Attribute Memory
59. OAM
61. This is the address in which Klonoa is stored on the memory
62. DMA3: 03000900 0600E000 80000400 DMA3: 03001100 0600E800 80000400 DMA3: 03004DB0 0600F000 80000200 DMA3: 03004800 07000000 8400003E
63. DMA3: 03000900 0600E000 80000400 DMA3: 03001100 0600E800 80000400 DMA3: 03004DB0 0600F000 80000200 DMA3: 03004800 07000000 8400003E We can see exactly the byte that writes on Klonoa’s object (03004800).
64. DMA3: 03000900 0600E000 80000400 DMA3: 03001100 0600E800 80000400 DMA3: 03004DB0 0600F000 80000200 DMA3: 03004800 07000000 8400003E We can see exactly the byte that writes on Klonoa’s OAM (03004800).
70. 1 2
82. Here is where Y fixes Klonoa’s position
83. Here is where Y fixes Klonoa’s position Here is where which decides if should fix or not Klonoa’s position
85. https://www.coranac.com/tonc/text/hardware.htm
86. https://www.coranac.com/tonc/text/hardware.htm
89. Let’s find the tilemap on rom THE DAY I REVERSE ENGINEERED A GAMEBOY ADVANCE GAME
90. Cartridge > > > > The data flow
91. Cartridge Slow WRAM > > > > The data flow
92. Cartridge Fast WRAM Slow WRAM > > > > The data flow
93. Cartridge Fast WRAM Slow WRAM VRAM > > > > The data flow
94. Cartridge Fast WRAM Display Slow WRAM VRAM > > > > The data flow
95. Cartridge Fast WRAM Display VRAM Slow WRAM > > > > Our research flow
97. swi 11h what?
98. Swi
99. SoftWare Interrupt
100. SoftWare Interrupt = Bios calls
102. BIOS is a firmware that is intended to initialise the physical components of the system
103. BIOS is a firmware that is intended to initialise the physical components of the system In GBA, its BIOS exposes many functions often used in games, including data compression and decompression
104. BIOS is a firmware that is intended to initialise the physical components of the system In GBA, its BIOS exposes many functions often used in games, including data compression and decompression Each function has an associated numeric code, which must be used as a parameter in the SWI statement
105. Input: How division works on ARM Assembly swi 0x06 Output:
106. Input: How division works on ARM Assembly swi 0x06 R0
 numerator R1
 denominator Output:
107. Input: How division works on ARM Assembly swi 0x06 R0
 numerator R1
 denominator R0
 numerator / denominator R1
 numerator % denominator R3
 abs(numerator / denominator) Output:
114. 6E 6E 6E B0 B1 BD 77 AB B3 AB B3 7C 6E 6E 6E 6E 6E 6E 6E 6E 7C 6E 6E 6E 6E 7C 6E 6E
115. 6E 6E 6E B0 B1 BD 77 AB B3 AB B3 7C 6E 6E 6E 6E 6E 6E 6E 6E 7C 6E 6E 6E 6E 7C 6E 6E
116. 6E 6E 6E B0 B1 BD 77 AB B3 AB B3 7C 6E 6E 6E 6E 6E 6E 6E 6E 7C 6E 6E 6E 6E 7C 6E 6E 6E 6E 6E B0 B1 BD 77 AB B3 AB B3 7C 6E 6E 6E 6E 6E 6E 6E 6E 7C 6E 6E 6E 6E 7C 6E 6E
117. 6E 6E 6E B0 B1 BD 77 AB B3 AB B3 7C 6E 6E 6E 6E 6E 6E 6E 6E 7C 6E 6E 6E 6E 7C 6E 6E 6E 6E 6E B0 B1 BD 77 AB B3 AB B3 7C 6E 6E 6E 6E 6E 6E 6E 6E 7C 6E 6E 6E 6E 7C 6E 6E
118. 6E 6E 6E B0 B1 BD 77 AB B3 AB B3 7C 6E 6E 6E 6E 6E 6E 6E 6E 7C 6E 6E 6E 6E 7C 6E 6E 6E 6E 6E B0 B1 BD 77 AB B3 AB B3 7C 6E 6E 6E 6E 6E 6E 6E 6E 7C 6E 6E 6E 6E 7C 6E 6E =
119. Let’s paint the tilemap THE DAY I REVERSE ENGINEERED A GAMEBOY ADVANCE GAME
120. 0x1A 0x1B 0x1C 0x1D 0x1E 0x1F
121. 0x1A 0x1B 0x1C 0x1D 0x1E 0x1F 0x1A 0x1B 0x1C 0x1D 0x1E 0x1F 0x1A 0x1B 0x1C 0x1D 0x1E 0x1F 0x1A 0x1B 0x1C 0x1D 0x1E 0x1F
122. 0x1A 0x1B 0x1C 0x1D 0x1E 0x1F 0x1A 0x1B 0x1C 0x1D 0x1E 0x1F 0x1A 0x1B 0x1C 0x1D 0x1E 0x1F 0x1A 0x1B 0x1C 0x1D 0x1E 0x1F
123. 0x1A 0x1B 0x1C 0x1D 0x1E 0x1F
124. H · W = 25023
 H,W ∈ ℕ
126. x x x x a x x x x x x x x b x x x x I’m on tile a
127. x x x x a x x x x x x x x b x x x x I’m on tile a
128. x x x x a x x x x x x x x b x x x x I’m on tile a x x x x a x x x x x x x x b x x x x From the tile a to b there are 9 bytes (= 9 tiles), so the length of the tilemap is exactly 9
130. Breakpoint here
131. …is located here This byte…
133. As I change this byte…
134. …it reflects right here
136. Changing these bytes…
137. …we drop Klonoa one level below
139. Changing these bytes… …we found the B tile!
140. 020085DB The length of the level is 420! - 02008437 = 1A4 (420)
141. https://github.com/oliver-moran/jimp
142. const Jimp = require('jimp') const { drop } = require('ramda') const fs = require('fs') const data = drop(3, fs.readFileSync('dump/level-2/tilemap'))
143. const getPixelColor = hexTile "# { if (hexTile === 0) { return 0x00000000 } return 0xFFFFFFFF }
144. new Jimp(300, 600, (err, image) "# { let x = 0 let y = 0 for (let i = 0; i < data.length; i += 1) { const value = data[i] x += 1 if (x === 300) { y += 1 x = 0 } let color = getPixelColor(value) image.setPixelColor(color, x, y) } image.write('image.png') })
150. let’s see the project THE DAY I REVERSE ENGINEERED A GAMEBOY ADVANCE GAME
151. Coding THE DAY I REVERSE ENGINEERED A GAMEBOY ADVANCE GAME
152. Stack
153. React.js ✈
154. Former-Kit ✈
155. Ramda.js ✈
156. architecture
157. ✂ Brush Scissors
158. klo-gba.js/scissors/src/visions/
159. export default { rom: { tilemap: [0x1B27FC, 0x1B36F3], customTilemap: [0x367700, 0x3686AF], objects: [0xE2B90, 0xE2F59], portals: [0xD48C8, 0xD48EF], }, tilemap: { totalStages: 3, height: 60, width: 420, scheme: [ { name: 'grass', ids: [0x7D, 0x80, 0x81, 0x82, 0x8E, 0x8F, 0x90],
160. export default { rom: { tilemap: [0x1B27FC, 0x1B36F3], customTilemap: [0x367700, 0x3686AF], objects: [0xE2B90, 0xE2F59], portals: [0xD48C8, 0xD48EF], }, tilemap: { totalStages: 3, height: 60, width: 420, scheme: [ { name: 'grass', ids: [0x7D, 0x80, 0x81, 0x82, 0x8E, 0x8F, 0x90],
161. export default { rom: { tilemap: [0x1B27FC, 0x1B36F3], customTilemap: [0x367700, 0x3686AF], objects: [0xE2B90, 0xE2F59], portals: [0xD48C8, 0xD48EF], }, tilemap: { totalStages: 3, height: 60, width: 420, scheme: [ { name: 'grass', ids: [0x7D, 0x80, 0x81, 0x82, 0x8E, 0x8F, 0x90],
162. { name: 'rock', ids: [0x54, 0x53, 0x55, 0x56, 0x57, 0x58, 0x59, }, { name: 'darkRock', ids: [0x40, 0x41, 0x42, 0x43, 0x44, 0x45, 0x46, }, { name: 'wood', ids: [0x52, 0x94, 0x98, 0x99, 0x9A, 0x9B, 0x9D, }, { name: 'bridgeRope', ids: [0x04, 0x05, 0x0B, 0x0C, 0x11, 0x13, 0x14,
163. { name: 'spike', ids: [0x3D], }, ], },
164. Web assembly
165. Tilemap compressed Old C code to uncompress it Decompressed Tilemap > >
166. Tilemap compressed Old C code to uncompress it Decompressed Tilemap > > Can’t run C code on browser!
167. Tilemap compressed Old C code to uncompress it Decompressed Tilemap > >
168. Tilemap compressed Old C code to uncompress it Decompressed Tilemap > > >Emscripten >WebAssembly
169. huffman.c lzss.c > > Emscripten huffman.js lzss.js huffman.wasm lzss.wasm +
170. class HuffmanDecodeError extends Error { constructor (e) { super(`Error when tried to use huffman decoder: ${e}`) this.name = 'HuffmanDecodeError' } } huffmanModule.onRuntimeInitialized = () "# {} const huffmanDecode = (buffer) "# { FS.writeFile('file', buffer)
171. class HuffmanDecodeError extends Error { constructor (e) { super(`Error when tried to use huffman decoder: ${e}`) this.name = 'HuffmanDecodeError' } } huffmanModule.onRuntimeInitialized = () "# {} const huffmanDecode = (buffer) "# { FS.writeFile('file', buffer)
172. const huffmanDecode = (buffer) "# { FS.writeFile('file', buffer) huffmanModule._HUF_Decode() try { return huffmanModule.FS.readFile('file', { encoding: 'binary' }) } catch (e) { throw new HuffmanDecodeError(e) } }
173. function docker_run_emscripten { local filename="$1" echo "Compiling $filename$$." docker run \ --rm -it \ -v $(pwd)/scissors/src/wasm:/src \ trzeci/emscripten \ emcc -s WASM=1 -s ALLOW_MEMORY_GROWTH=1 -s MODULARIZE=1 -s EXTRA_EXPORTED_RUNTIME_METHODS=[\"FS\"] -s EXPORT_NAME=\"$filename\" -o ./$filename.js $filename.c } docker_run_emscripten huffman docker_run_emscripten lzss
174. function docker_run_emscripten { local filename="$1" echo "Compiling $filename$$." docker run \ --rm -it \ -v $(pwd)/scissors/src/wasm:/src \ trzeci/emscripten \ emcc -s WASM=1 -s ALLOW_MEMORY_GROWTH=1 -s MODULARIZE=1 -s EXTRA_EXPORTED_RUNTIME_METHODS=[\"FS\"] -s EXPORT_NAME=\"$filename\" -o ./$filename.js $filename.c } docker_run_emscripten huffman docker_run_emscripten lzss
176. const extractFullTilemap = (romBuffer, [addressStart, addressEnd]) "# romBuffer.slice(addressStart, addressEnd) |> huffmanDecode |> lzssDecode
177. Saving the new tilemap
178. Each level is stored continually in the memory First Level Second Level Third Level
179. First Level Second Level Third Level > Changes in the first level
180. First Level Second Level Third Level > Customised First Level > Changes in the first level
181. Second Level Third Level First Level Second Level Third Level > Customised First Level > Changes in the first level
182. Second Level Third Level First Level Second Level Third Level > Customised First Level > Changes in the first level
184. ARM Thumb
185. ARM Thumb Faster to execute Instructions demands less memory
186. ARM Thumb Faster to execute Instructions demands less memory Can perform instructions more complex
187. The switch between ARM and Thumb must be done by bx instruction. And this instruction only can read a register
188. Instructions to load a level . . . . . . . . . Very big hole at the end of cartridge First Level__ Second Level__ Third Level__ 081B27FC 081B3E5C 081B50AC Instructions to load a level
189. First Level__ Second Level__ Third Level__ . . . . . . . . . 081B27FC 081B3E5C 081B50AC Instructions to load a level Customised First Level__ Customised level loader Constant addresses map table Hole Customised Second Level__ Hole Customised Third Level__ Hole Hole 08367700 083686B0 08369380
190. Instructions to load a level 08367620 FC 27 1B 08 08367624 00 77 36 08 08367628 5C 3E 1B 08 0836762C B0 86 36 08 08367620 AC 50 1B 08 08367634 80 93 36 08 First Level__ Second Level__ Third Level__ . . . . . . . . . 081B27FC 081B3E5C 081B50AC Customised First Level__ Customised level loader Constant addresses map table Hole Customised Second Level__ Hole Customised Third Level__ Hole Hole 08367700 083686B0 08369380
191. Instructions to load a level 08367620 FC 27 1B 08 08367624 00 77 36 08 08367628 5C 3E 1B 08 0836762C B0 86 36 08 08367620 AC 50 1B 08 08367634 80 93 36 08 First Level__ Second Level__ Third Level__ . . . . . . . . . 081B27FC 081B3E5C 081B50AC Customised First Level__ Customised level loader Constant addresses map table Hole Customised Second Level__ Hole Customised Third Level__ Hole Hole 08367700 083686B0 08369380
192. Instructions to load a level 08367620 FC 27 1B 08 08367624 00 77 36 08 08367628 5C 3E 1B 08 0836762C B0 86 36 08 08367620 AC 50 1B 08 08367634 80 93 36 08 First Level__ Second Level__ Third Level__ . . . . . . . . . 081B27FC 081B3E5C 081B50AC Customised First Level__ Customised level loader Constant addresses map table Hole Customised Second Level__ Hole Customised Third Level__ Hole Hole 08367700 083686B0 08369380
193. Instructions to load a level 08367620 FC 27 1B 08 08367624 00 77 36 08 08367628 5C 3E 1B 08 0836762C B0 86 36 08 08367620 AC 50 1B 08 08367634 80 93 36 08 First Level__ Second Level__ Third Level__ . . . . . . . . . 081B27FC 081B3E5C 081B50AC Customised First Level__ Customised level loader Constant addresses map table Hole Customised Second Level__ Hole Customised Third Level__ Hole Hole 08367700 083686B0 08369380
194. Instructions to load a level (patched) First Level__ Second Level__ Third Level__ . . . . . . . . . 081B27FC 081B3E5C 081B50AC Customised First Level__ Customised level loader Constant addresses map table Hole Customised Second Level__ Hole Customised Third Level__ Hole Hole 08367700 083686B0 08369380 Original loader Patched loader 08043B0A mov r4,r0 08043B0C bl 08367610h 08043B10 bl 0805143Ch 08043B0A mov r4,r0 08043B0C add r0,r5,4 08043B0E mov r1,r4 08043B10 bl 0805143Ch
195. Instructions to load a level (patched) First Level__ Second Level__ Third Level__ . . . . . . . . . 081B27FC 081B3E5C 081B50AC Customised First Level__ Customised level loader Constant addresses map table Hole Customised Second Level__ Hole Customised Third Level__ Hole Hole 08367700 083686B0 08369380 R0 is the pointer to where is the tilemap that will load Original loader Patched loader 08043B0A mov r4,r0 08043B0C bl 08367610h 08043B10 bl 0805143Ch 08043B0A mov r4,r0 08043B0C add r0,r5,4 08043B0E mov r1,r4 08043B10 bl 0805143Ch
196. Instructions to load a level (patched) First Level__ Second Level__ Third Level__ . . . . . . . . . 081B27FC 081B3E5C 081B50AC Customised First Level__ Customised level loader Constant addresses map table Hole Customised Second Level__ Hole Customised Third Level__ Hole Hole 08367700 083686B0 08369380 Original loader Patched loader 08043B0A mov r4,r0 08043B0C bl 08367610h 08043B10 bl 0805143Ch 08043B0A mov r4,r0 08043B0C add r0,r5,4 08043B0E mov r1,r4 08043B10 bl 0805143Ch
197. Instructions to load a level (patched) First Level__ Second Level__ Third Level__ . . . . . . . . . 081B27FC 081B3E5C 081B50AC Customised First Level__ Customised level loader Constant addresses map table Hole Customised Second Level__ Hole Customised Third Level__ Hole Hole 08367700 083686B0 08369380 Original loader Patched loader 08043B0A mov r4,r0 08043B0C bl 08367610h 08043B10 bl 0805143Ch 08043B0A mov r4,r0 08043B0C add r0,r5,4 08043B0E mov r1,r4 08043B10 bl 0805143Ch
198. Instructions to load a level (patched) First Level__ Second Level__ Third Level__ . . . . . . . . . 081B27FC 081B3E5C 081B50AC Customised First Level__ Customised level loader Constant addresses map table Hole Customised Second Level__ Hole Customised Third Level__ Hole Hole 08367700 083686B0 08369380 08367610 mov r0,r15 08367612 add r0,3Ch 08367614 bx r0
199. Instructions to load a level (patched) First Level__ Second Level__ Third Level__ . . . . . . . . . 081B27FC 081B3E5C 081B50AC Customised First Level__ Customised level loader Constant addresses map table Hole Customised Second Level__ Hole Customised Third Level__ Hole Hole 08367700 083686B0 08369380 08367650 add r0,r4,4h 08367654 ldr r4,[r15,#-3Ch] 08367658 cmp r0,r4 0836765C ldreq r0,[r15,#-40h] 08367654 ldr r4,[r15,#-40h] 08367658 cmp r0,r4 0836765C ldreq r0,[r15,#-44h] 08367654 ldr r4,[r15,#-44h] 08367658 cmp r0,r4 0836765C ldreq r0,[r15,#-48h] 08367660 mov r4,r1 08367664 bx r14
200. Instructions to load a level (patched) First Level__ Second Level__ Third Level__ . . . . . . . . . 081B27FC 081B3E5C 081B50AC Customised First Level__ Customised level loader Constant addresses map table Hole Customised Second Level__ Hole Customised Third Level__ Hole Hole 08367700 083686B0 08369380 08367650 add r0,r4,4h 08367654 ldr r4,[r15,#-3Ch] 08367658 cmp r0,r4 0836765C ldreq r0,[r15,#-40h] 08367654 ldr r4,[r15,#-40h] 08367658 cmp r0,r4 0836765C ldreq r0,[r15,#-44h] 08367654 ldr r4,[r15,#-44h] 08367658 cmp r0,r4 0836765C ldreq r0,[r15,#-48h] 08367660 mov r4,r1 08367664 bx r14
201. Instructions to load a level (patched) First Level__ Second Level__ Third Level__ . . . . . . . . . 081B27FC 081B3E5C 081B50AC Customised First Level__ Customised level loader Constant addresses map table Hole Customised Second Level__ Hole Customised Third Level__ Hole Hole 08367700 083686B0 08369380 08367650 add r0,r4,4h 08367654 ldr r4,[r15,#-3Ch] 08367658 cmp r0,r4 0836765C ldreq r0,[r15,#-40h] 08367654 ldr r4,[r15,#-40h] 08367658 cmp r0,r4 0836765C ldreq r0,[r15,#-44h] 08367654 ldr r4,[r15,#-44h] 08367658 cmp r0,r4 0836765C ldreq r0,[r15,#-48h] 08367660 mov r4,r1 08367664 bx r14
202. Instructions to load a level (patched) First Level__ Second Level__ Third Level__ . . . . . . . . . 081B27FC 081B3E5C 081B50AC Customised First Level__ Customised level loader Constant addresses map table Hole Customised Second Level__ Hole Customised Third Level__ Hole Hole 08367700 083686B0 08369380 08367650 add r0,r4,4h 08367654 ldr r4,[r15,#-3Ch] 08367658 cmp r0,r4 0836765C ldreq r0,[r15,#-40h] 08367654 ldr r4,[r15,#-40h] 08367658 cmp r0,r4 0836765C ldreq r0,[r15,#-44h] 08367654 ldr r4,[r15,#-44h] 08367658 cmp r0,r4 0836765C ldreq r0,[r15,#-48h] 08367660 mov r4,r1 08367664 bx r14
203. Instructions to load a level (patched) First Level__ Second Level__ Third Level__ . . . . . . . . . 081B27FC 081B3E5C 081B50AC Customised First Level__ Customised level loader Constant addresses map table Hole Customised Second Level__ Hole Customised Third Level__ Hole Hole 08367700 083686B0 08369380 08367650 add r0,r4,4h 08367654 ldr r4,[r15,#-3Ch] 08367658 cmp r0,r4 0836765C ldreq r0,[r15,#-40h] 08367654 ldr r4,[r15,#-40h] 08367658 cmp r0,r4 0836765C ldreq r0,[r15,#-44h] 08367654 ldr r4,[r15,#-44h] 08367658 cmp r0,r4 0836765C ldreq r0,[r15,#-48h] 08367660 mov r4,r1 08367664 bx r14
204. 1. Redirect to the patched code 2. Check if the R0 is on the table 3. If yes, load the associated value 4. Return to the original loader
205. 1. Redirect to the patched code 2. Check if the R0 is on the table 3. If yes, load the associated value 4. Return to the original loader
206. 1. Redirect to the patched code 2. Check if the R0 is on the table 3. If yes, load the associated value 4. Return to the original loader
207. 1. Redirect to the patched code 2. Check if the R0 is on the table 3. If yes, load the associated value 4. Return to the original loader
208. 1. Redirect to the patched code 2. Check if the R0 is on the table 3. If yes, load the associated value 4. Return to the original loader
210. Result THE DAY I REVERSE ENGINEERED A GAMEBOY ADVANCE GAME
217. WE ARE... THE DAY I REVERSE ENGINEERED A GAMEBOY ADVANCE GAME
218. MACABEUS macabeus ____ www.macalogs.com.br _ _ Software Engineer Always creating crazy projects
219. MATHEUS ALBUQUERQUE YTHECOMBINATOR www.ythecombinator.space LAND@YTHECOMBINATOR.SPACE Software Engineer,
 Front-End addicted to emojis, memes and beer
220. Benjamin Stauffer kcowolf TRANSLATOR
221. Raul peres behance.net/Kniksis illustrator
222. This talk THE DAY I REVERSE ENGINEERED A GAMEBOY ADVANCE GAME
223. http://bit.ly/balccon-gba http://bit.ly/theconf-gba
224. http://bit.ly/klo-gba-js-repo
225. http://bit.ly/gba-posts
226. Obrigado THANKS @macabeus
227. São Paulo Lisbon
229. soccer, caipirinha and carnival
230. soccer, caipirinha and carnival ✘
234. ✔ Display tiles and OAM ✔ Allow the user to edit it
235. https://github.com/konvajs/konva
237. 1st load: ˜3 seconds! 2nd load: ˜13 seconds!
238. After some React.js performance work…
239. 1st load
240. 1st load ˜1.8 seconds!
241. 1st load 2nd load
242. 1st load 2nd load ˜3.6 seconds!
243. After switching from Canvas to WebGL…
244. 1st load
245. 1st load ˜1.6 seconds!
246. 1st load ˜1.6 seconds! 2nd load
247. 1st load ˜1.6 seconds! 2nd load ˜2.8 seconds!
248. After doing more optimizations on WebGL…
249. 1st load
250. 1st load ˜625 ms!
251. 1st load 2nd load ˜625 ms!
252. 1st load 2nd load ˜536 ms! ˜625 ms!
253. 1st load: ˜3 seconds! 2nd load: ˜13 seconds! Perf recap: No one is gonna play with this
254. 1st load: ˜3 1.8 seconds! 2nd load: ˜13 3.6 seconds! Perf recap: Removing wasted renders and other React optimisation stuff.
255. 1st load: ˜3 1.8 1.6 seconds! 2nd load: ˜13 3.6 2.8 seconds! Perf recap: Canvas → WebGL
256. 1st load: ˜3 1.8 1.6 0.625 seconds! 2nd load: ˜13 3.6 2.8 0.536 seconds! Perf recap: React → WebGL
259. DMA3: 03000900 0600E000 80000400 DMA3: 03001100 0600E800 80000400 DMA3: 03004DB0 0600F000 80000200 DMA3: 03004800 07000000 8400003E Update the OAM
260. DMA3: 03000900 0600E000 80000400 DMA3: 03001100 0600E800 80000400 DMA3: 03004DB0 0600F000 80000200 DMA3: 03004800 07000000 8400003E Update the OAM
261. DMA3: 03000900 0600E000 80000400 DMA3: 03001100 0600E800 80000400 DMA3: 03004DB0 0600F000 80000200 DMA3: 03004800 07000000 8400003E Update the OAM 0300480A:0300480B ✘
262. C
268. Global OAM
269. Global OAM
270. > > > > 08051440 08003CD4 0800B602 0800B634 0804505C
272. ROM OAM
277. Global OAM OAM > ROM OAM >
279. ROM OAM of the first level 08367700 083686B0 08369380
280. ROM OAM of the first level 08367700 083686B0 08369380 ROM OAM of the third level ROM OAM of the second level Hole Hole . . .
281. const [ xFirstPosition, yFirstPosition, xSecondPosition, ySecondPosition, xThirdPosition, yThirdPosition, xFourthPosition, yFourthPosition, xFifthPosition, yFifthPosition, kind, ] = qunpack.unpack('v2 x4 v2 x4 v2 x4 v2 x4 v2 x5 c', bytes);
282. const [ xFirstPosition, yFirstPosition, xSecondPosition, ySecondPosition, xThirdPosition, yThirdPosition, xFourthPosition, yFourthPosition, xFifthPosition, yFifthPosition, kind, ] = qunpack.unpack('v2 x4 v2 x4 v2 x4 v2 x4 v2 x5 c', bytes); ✘
283. const { xStage1, yStage1, xStage2, yStage2, xStage3, yStage3, xStage4, yStage4, xStage5, yStage5, kind, } = binary.parse(memory) .word16lu('xStage1').word16lu('yStage1') .skip(4) .word16lu('xStage2').word16lu('yStage2') .skip(4) .word16lu('xStage3').word16lu('yStage3') .skip(4) .word16lu('xStage4').word16lu('yStage4') .skip(4) .word16lu('xStage5').word16lu('yStage5') .skip(5) .word8lu('kind') .vars