1 2 3
Posted: 11/30/2012 9:21 AM
Quote
FractalFusion
Editor, Expert player (2079)
Joined: 6/15/2005
Posts: 3282
Glitchy TAS of 2013 Gameboy TAS of 2013 PSX TASer of 2010
OK, I've managed to reduce it to 11 bytes. I must warn though that what follows is pretty hackish: 
24      INC H
input:
76      HALT
E2      LDH (C) A
F2      LDH A (C)
2F      CPL A
32      LDD (HL) A
02      LD (BC) A (item hack)
18 F8   JR input
64 D3   (not executed) pointer
Inject this code into D364. The pointer above will fall on D36D, as desired. This code relies on the fact that the registers have preset values at the moment of PC hijack: 
AF: 5880
BC: AF00
DE: 0D5D
HL: D364 (or whatever D36D points to)
SP: DFF9
PC: D364
In particular, HL is whatever D36D points to (D364), so INC H (making it D464) to obtain a sane starting point for HL (byte sequence will be written backwards and will overwrite the JR opcode thus allowing execution of the byte sequence). C already has 0, and A already has a number whose 4th bit is 1 and 5th bit is 0, so there is no need to initialize them. Finally, DI is not required for this, and HALT controls it so bytes are written per frame. This code also relies on the fact that a patching program can be written entirely in the 1x and 2x opcode rows. Note that the output byte sequence is limited to 1x and 2x opcodes, and 1x alternates with 2x (this is from "LDH A (C)" and "CPL A" above). The idea is to load an address 1x2x or 2x2x into DE, load A with the value at that address (which comes from the ROM) and put it in the address pointed by HL (which should be Dxxx-something). A can also be modified using CPL, DAA, RR, and RL, and the address for HL can be set up quickly because of "ADD HL,HL" (essentially HL:=HL*2), among H and L-modifying opcodes. All these opcodes come from the 1x and 2x rows. A self-contained program cannot be written entirely in 1x and 2x rows (because no backward branches are possible) but since this patching program need not be self-contained, just write a new program after the byte sequence. I should do more testing.
Posted: 12/3/2012 2:51 AM
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FractalFusion
Editor, Expert player (2079)
Joined: 6/15/2005
Posts: 3282
Glitchy TAS of 2013 Gameboy TAS of 2013 PSX TASer of 2010
Now to the patching program, which writes a 34-byte program at D465. Here is the table of 1x2y and 2x2y addresses: 
xxyy
 yy=20 21 22 23 24 25 26 27 28 29 2A 2B 2C 2D 2E 2F
xx=
10: FA E0 D4 A7 C8 47 0E 00 11 10 C1 2A 12 14 7B C6
11: 0A 5F 3E 6B 22 7B A7 28 06 18 F1 3E 63 83 77 D1
12: D1 3C 22 F1 77 C9 3E 01 EA 4A CC 3E 40 EA 9A D0
13: D1 06 41 C3 5B 3C 21 DB D0 4F 06 00 09 7E C9 F0
14: 3E 09 38 17 78 FE 4A 3E 0A 38 10 78 FE 74 3E 0B
15: D4 CB BE E1 C9 E5 21 2F D4 CB 9E E1 C9 E5 21 2F
16: 1E F1 CD 7E 3E F1 E0 BA C9 3E 08 E0 C6 CD 64 1E
17: 20 FC C9 E5 1A FE 50 20 04 44 4D E1 C9 FE 4E 20
18: C3 24 17 93 8C 50 93 91 80 88 8D 84 91 50 8F 82
19: F0 F9 AB EA 57 D3 79 EA 3A CC 78 EA 3B CC 2A FE
1A: 28 10 FE 16 28 0C 7E CD 38 22 CD 3E 37 E1 C1 C3
1B: 2A 12 7B 3C E6 1F 47 7B E6 E0 B0 5F 0D 20 EE C9
1C: C9 F0 C6 A7 C8 08 BF FF F0 C7 6F F0 C8 67 F9 F0
1D: E0 4A E0 06 E0 07 E0 47 E0 48 E0 49 3E 80 E0 40
1E: 00 20 CD 9B 49 CD F5 1E CD 6D 3E CD C8 01 F0 D6
1F: 3C C0 AF EA 43 DA FA 42 DA 3C EA 42 DA FE 3C C0
20: CD 93 20 20 DE C3 9B 20 F0 FF E6 0F FE 08 20 D3
21: 33 21 FA 42 CC C6 60 E0 AC F0 AA FE 02 20 04 3E
22: 78 18 15 AF EA 2A C0 EA 2B C0 EA 2C C0 EA 2D C0
23: C0 F0 B8 F5 3E 01 CD 7E 3E 3E FF EA CA CF CD B7
24: 3E 03 EA A6 D0 AF EA A0 D0 EA A1 D0 EA A7 D0 CD
25: D0 67 23 C3 8D 27 E1 AF EA A0 D0 FA A7 D0 CB 4F
26: FA A3 D0 85 30 01 24 EA AC D0 7C EA AD D0 FA A0
27: D0 47 FA A2 D0 B8 20 BD AF EA A0 D0 C9 11 5D 27
28: 84 3E 21 11 CF CB 46 CB 86 20 06 FA 5D D3 CD 8B
29: 29 3E 02 EA 93 CF F0 B8 F5 3E 01 CD 7E 3E CD A5
2A: D7 CB 6F FA 26 CC 0E 07 20 01 0D B9 20 C6 AF EA
2B: 93 CF A7 20 03 CD 1C 23 3E 01 EA 37 CC FA 29 D1
2C: 2F D7 CB B6 C3 E8 35 CB 4F C2 33 2D CB 57 C2 C9
2D: C9 AF EA 35 CC 3E FF C9 F1 F6 F7 50 7F 7F 7F 7F
2E: CD 03 13 F1 EA 1D D1 E1 D1 13 FA 93 CF FE 03 20
2F: F1 06 F6 80 12 13 3E 50 12 F1 EA 1D D1 C1 D1 E1

 yy=20 21 22 23 24 25 26 27 28 29 2A 2B 2C 2D 2E 2F
If the desired number is in the 1x2y table, use the two-byte load (0x11): 
11 2y 1x *2F 1A 22
If the desired number is in the 2x2y table, use two one-byte loads (0x16, 0x1E): 
16 2x 1E 2y 1A 22
It is somewhat more complicated if the number is not in the table. I won't say more on that now. Here is the patching program. It begins at D37D and runs for 232 bytes. It sets the HL pointer to D465, then writes the stage 2 program (bytes indicated on the right, with assembly translation). Starred (*) opcodes in the patching program are hack bytes. 
21 10 2F *1F                       HL=2F10
29 *1F                             HL=5E20
29                                 HL=BC40
11 25 18 *2F                       DE=1825
19 *2F                             HL=D465
11 25 1A *2F 1A 2F *13 22          F3  DI
16 21 1E 21 1A 22                  21  LD HL 98EE
11 2E 1B *2F 1A 22                 EE
11 2D 1C *2F 1A 2F *13 22          98
11 22 11 *2F 1A 22                 3E  LD A 77
11 2E 11 *2F 1A 22                 77
11 24 11 *2F 1A 22                 22  LDI (HL) A
11 24 11 *2F 1A 22                 22  LDI (HL) A
16 27 1E 2D 1A 22                  11  LD DE FEFF
11 27 1C *2F 1A 22                 FF
11 25 14 *2F 1A 22                 FE
16 21 1E 21 1A 22                  21  LD HL DAAA
16 21 1E 2A 1A 22                  AA
11 25 1F *2F 1A 22                 DA
                                   input:
11 2C 19 *2F 1A *24 17 *25 *13 22  76  HALT
16 21 1E 2F 1A 22                  3E  LD A 3
16 24 1E 21 1A 22                  03
16 22 1E 24 1A 22                  EA  LD (2000) A
11 27 10 *2F 1A 22                 00
16 20 1E 22 1A 22                  20
16 20 1E 20 1A 22                  CD  CALL 4004
16 21 1E 2E 1A 22                  04
11 2C 12 *2F 1A 22                 40
16 20 1E 28 1A 22                  F0  LDH A (FFF5)
16 23 1E 23 1A 22                  F5
11 24 11 *2F 1A 22                 22  LDI (HL) A
16 2E 1E 22 1A 22                  13  INC DE
11 2E 10 *2F 1A 22                 7B  LD A E
11 2A 17 *2F 1A 2F *13 22          B2  OR D
16 23 1E 2C 1A 22                  CA  JP Z DAAA
16 21 1E 2A 1A 22                  AA
11 25 1F *2F 1A 22                 DA
16 22 1E 21 1A 22                  18  JR input
16 2E 1E 22 1A 2F *13 22           EC
*1F *2F *1F
About the stage 2 program: The initial part (above HALT) sets the size of the stage 3 program (0x10000-0xFEFF = 257 bytes) and where it is written to (0xDAAA). The part under input uses bank switch to 3 and call routine at 0x4004 (thanks p4wn3r) to get input value to FFF5. I also did some study on VRAM and experimented. Since there was a little room left to fit in a few more bytes into the stage 2 program, I inserted instructions (above HALT) to write ぇ tiles on the screen. The tiles already exist from before the PC hijack. I'm currently planning what the stage 3 program should do. I'll probably need to study sound as well. I'm not sure how the music keeps playing or where the music data is stored. (I used HALT, unlike bortreb's submission at least for his first 3 stages).
Posted: 12/14/2012 3:04 AM
Quote
FractalFusion
Editor, Expert player (2079)
Joined: 6/15/2005
Posts: 3282
Glitchy TAS of 2013 Gameboy TAS of 2013 PSX TASer of 2010
Hm, I somehow missed the part of p4wn3r's post that said that after a HALT, the game writes input to FFF5. Well then, that makes it even easier. 
76        HALT
F0 F5     LDH A (FFF5)
22        LDI (HL) A
C3 xx D3  JP D3xx
... provided that the code is followed by a bunch of 0s or statements that have no significant effect when executed. The jump to D3xx goes into these 0s, and the code is located so that xx D3 falls on D36D, which is the pointer to this code. Of course HL is set to D3xx as well, and the program writes there. The mind-numbing thing is that the program continuously executes (every cycle) whatever is written there. This can be bypassed using some well-placed spaghetti code, provided there is enough room to do so. I'll get to that later. I now change the code to make use of rival name, and avoid switching parity. Here is the 11-byte block (all NOPs are hack bytes): 
00        NOP
00        NOP
22        LDI (HL) A
00        NOP
76        HALT
00        NOP
F0 F5     LDH A (FFF5)
D4 50 D3  CALL NC D350
Note that the program will always call routine since carry is always clear. The initial placement of LDI (HL) A means that the program will start by writing 0x50, and fortunately this is a harmless instruction (LD D B). In terms of taking D343-D34D and swapping it to D322-D32C, this is: 
   00 30 00 sp       fm pk ed
0  $1 $2 $3 N1 0  0  N2 N3 N4 0
*  .  *  .  *  .  *  .  *  .  *
00 00 22 00 76 00 F0 F5 D4 50 D3
where $ is money byte, N is rival name byte, * means quantity (when switched to D322-D32C), and . means item ID. Some * bytes must be reduced through item tossing, but . bytes are exact, so parity need not be switched. I then place this 11-byte block at D364-D36E. When executed, this program writes 0x50 at D350, then writes in forward direction whatever input you give it. D350 is also executed every frame (this is why the writing program must be preceded by harmless opcodes such as 0s). Using input, I write the following at D351 (remember this is located just before the writing program): 
18 0F     JR there
there2:
16 80     LD D 0x80 (limit)
21 6F D3  LD HL D36F (target)
input:
76        HALT
F0 F5     LDH A (FFF5)
22        LDI (HL) A
15        DEC D
CA 6F D3  JP Z D36F (target)
18 F6     JR input
there:
18 EF     JR there2
Here's an explanation of why this works: - The program first writes 0x18 so the instruction reads "jump relative by 0". When executed, this doesn't branch anywhere (think about it), so execution normally falls back into the writing program. - Next time through, the program writes 0x0F so now the instruction reads "jump relative forward by 15". Provided there is enough space, execution still falls back into the writing program. - Because of the jump instruction, the program will not execute the following 15 bytes through the next 15 cycles, so the program can write whatever it wants there. - At the destination of the jump, the program then writes 0x18. The instruction there reads "jump relative by 0", and again no harm is done. - Finally, the program writes 0xEF so now the instruction reads "jump relative backward by 17". When execution hits this instruction, it jumps into the new program written in the 15 bytes between the jumps, and stage 2 begins.
Posted: 2/11/2013 5:00 PM
Quote
zwataketa
He/Him
Joined: 9/1/2012
Posts: 309
The things that lemonade can do! ^.^ i typed this while drinking lemonade, btw :D
I quit TASing.
Posted: 2/11/2013 7:25 PM
Quote
CoolKirby
Editor, Experienced player (570)
Joined: 11/8/2010
Posts: 4038
Exotic platforms TASer of 2014 NES TAS of 2013
Uh, what does that have to do with Pokemon Yellow?
Posted: 2/11/2013 9:09 PM
Quote
NitroGenesis
He/Him
Editor, Experienced player (556)
Joined: 12/24/2009
Posts: 1873
CoolKirby wrote:
Uh, what does that have to do with Pokemon Yellow?
Lemonade is yellow.
YoungJ1997lol wrote:
Normally i would say Yes, but thennI thought "its not the same hack" so ill stick with meh.
Posted: 2/11/2013 9:30 PM
Quote
CoolKirby
Editor, Experienced player (570)
Joined: 11/8/2010
Posts: 4038
Exotic platforms TASer of 2014 NES TAS of 2013
Pokemon Lemon Yellow?
Posted: 2/11/2013 10:33 PM
Quote
OmnipotentEntity
He/Him
Player (36)
Joined: 9/11/2004
Posts: 2631
CoolKirby wrote:
Uh, what does that have to do with Pokemon Yellow?
The run spent like 2 or 3 minutes just buying lemonaid.
Build a man a fire, warm him for a day, Set a man on fire, warm him for the rest of his life.
Posted: 3/14/2013 7:16 AM
(Edited: 3/14/2013 11:30 PM)
Quote
FractalFusion
Editor, Expert player (2079)
Joined: 6/15/2005
Posts: 3282
Glitchy TAS of 2013 Gameboy TAS of 2013 PSX TASer of 2010
This post is supplementary material for this submission, although it is useful here as well. ---- Here's an analytical look at my TAS. It is known that program execution in Pokemon Yellow can be hijacked with nothing more than a 7-byte sequence with 13 zeroes proceeding it. A 7-byte sequence would be: 
D368:
76        HALT
F0 F5     LDH A (FFF5)
22        LDI (HL) A
C3 5B D3  JP D35B
We'll get into how it works later. For the purposes of this TAS, the following 9-byte sequence takes less time to enter (and requires D350-D365 to be all 0): 
D366:
22        LDI (HL) A
00        NOP
76        HALT
00        NOP
F0 F5     LDH A (FFF5)
D4 50 D3  CALL NC D350
Why? Well, go back to when the rival was named (space) (female) (PK) (END). Memory in D343 at that point is: 
D343: 00 00 00 00 30 00 7F F5 E1 50 00
We want to change it to the 9-byte sequence somehow, so we do this: * Reset in the middle of saving. This overwrites D162 with FF and the game thinks you have 255 Pokemon. More importantly, you can now switch Pokemon below the 6th level. This will swap huge chunks of memory. * Switch any Pokemon 1-9 with the 10th Pokemon. This overwrites D31C with FF and the game thinks you have 255 items. * Switch the 17th and 20th Pokemon. Apart from other stuff going on, this will swap D322-D32C with D343-D34D. So now D322, which is close to the beginning of the item list, reads: 
D322: 00 00 00 00 30 00 7F F5 E1 50 00
or from the beginning of the item list: 
D31D: FF FF FF FF FF 00 00 00 00 30 00 7F F5 E1 50 00
None of the "items" cause problems when trying to toss them (some values crash the game, or are untossable). The addresses in the even spaces (D31E, D320, D322, ...) can all be reduced through tossing items, and 00 is treated as 0x100 so tossing one gives 0xFF. We now do this: * Toss D321 completely. This shifts it so it looks like this: 
D31D: FF FF FF FF 00 00 00 30 00 7F F5 E1 50 00 00 00
* Toss 14 of D323. This changes 0x30 to 0x22. * Toss 9 of D325. This changes 0x7F to 0x76. * Toss 13 of D327. This changes 0xE1 to 0xD4. * Toss 45 of D329. This changes the 0x00 directly after 0x50 to 0xD3. 
D31D: FF FF FF FF 00 00 00 22 00 76 F5 D4 50 D3 00 00
* Switch D32B and D329. This switches the last 00 00 with 50 D3. * Switch D329 and D327. This switches the same 00 00 with F5 D4. 
D31D: FF FF FF FF 00 00 00 22 00 76 00 00 F5 D4 50 D3
* Toss 16 of D327. This switches the last 0x00 with 0xF0. 
D31D: FF FF FF FF 00 00 00 22 00 76 00 F0 F5 D4 50 D3
Notice that we have our 9-byte sequence above starting from D324, but it needs to go to D366. So we do some Pokemon switches: * Switch the 19th and 17th Pokemon. This swaps D322-D32C with D338-D342. * Switch the 12th and 11th Pokemon. This swaps D322-D34D with D34E-D379 so now D338-D342 ends up at D364-D36E, exactly where we want it. Notice that the switching ensures that D350-D363 are all 0. Now close the menu. This is what happens: * At some point, the game reads D350 off of address D36E, which is supposed to hold a ROM address, and jumps to it. The value in register A is 0x50, and in HL is 0xD350, the location of the jump (note that the instruction 00 is NOP, which does nothing). 
D350: 00 00 ... 00 22 00 76 00 F0 F5 D4 50 D3
The instruction LDI (HL),A (22) writes whatever is in A to the address pointed by HL. When it reaches HALT (76), it waits for the next frame. 
D350: 50 00 00 ... 00 22 00 76 00 F0 F5 D4 50 D3
Now HALT runs a routine that puts key input into FFF5 as a number. The instruction LD A, (FFF5) (F0 F5) places this number into A. Then CALL D350 (D4 50 D3) jumps to D350 as a subroutine (in which we do not care about the "subroutine" part of it) and execution cycles again. Thus, by using LDI (HL), A over and over along with LD A (FFF5) to read input, we can write a program at D350. However, since D350 is executed every cycle, we must be careful. The program at D350 reads: 
50        LD D B
which is harmless. We feed the input 0x18 and now it reads: 
50        LD D B
18 00     JR 0
JR 0 means "jump relative by 0", which doesn't go anywhere. We feed the input 0x0F and now it reads: 
50        LD D B
18 0F     JR D362
Notice the significance of the last instruction. It jumps 15 forward but still prior to the instruction LDI (HL),A at D366. That means that now we can input anything for the next 15 bytes and execution will ignore them. We now write: 
50        LD D B
18 0F     JR there
16 98     LD D 0x98
21 6F D3  LD HL D36F
          input:
76        HALT
F0 F5     LDH A (FFF5)
22        LDI (HL) A
15        DEC D
CA 6F D3  JP Z D36F
18 F6     JR input
          there:
Feed the input 0x18: 
50        LD D B
18 0F     JR there
16 98     LD D 0x98
21 6F D3  LD HL D36F
          input:
76        HALT
F0 F5     LDH A (FFF5)
22        LDI (HL) A
15        DEC D
CA 6F D3  JP Z D36F
18 F6     JR input
          there:
18 00     JR 0
Again, when jumping to the label "there", the instruction 18 00 does nothing because it is jump by 0. Now feed the input 0xEF: 
50        LD D B
18 0F     JR there
          enter:
16 98     LD D 0x98
21 6F D3  LD HL D36F
          input:
76        HALT
F0 F5     LDH A (FFF5)
22        LDI (HL) A
15        DEC D
CA 6F D3  JP Z D36F
18 F6     JR input
          there:
18 EF     JR enter
Execution now jumps to "there", which then jumps to "enter", executing the program we set up. This is the stage 2 program, a simple RAM writer that writes 152 bytes to D36F and then executes it. It is left to the reader to verify this. Stage 3 is now constructed, and it is large. Here it is: 
21308F    LD HL 8F30   //where to place data in Tile Data Table
01D2D3    LD BC data   //where 8x8 data is
1628      LD D 28      //size of 8x8 data
          loop:
0A        LD A,(BC)
22        LDI (HL),A
22        LDI (HL),A
03        INC BC
15        DEC D
20F9      JR NZ loop

2100D6    LD HL D600
3E10      LD A #10
          loop1.5:
22        LDI (HL),A    //clear mirror
CB44      BIT 0,H
28FB      JR Z loop1.5  //loop until D700		

1E00      LD E 00      // register DE is offset of BTM
          outerloop:

76        HALT
F0F5      LD A, FFF5 
FEEF      CP A,#EF
2869      JR Z exit
FEEE      CP A,#EE
282B      JR Z refresh
3016      JR NC numbers
4F        LD C A
CB61      BIT 4,C
2804      JR Z sprite1
3EF4      LD A #F4 //pirev
1802      JR skip

          sprite1:
3EF3      LD A #F3 //pi

          skip:
CBA1      RES 4,C
0600      LD B 0
2100D6    LD HL D600 //start of lower BTM mirror (starting from 9980)
09        ADD HL,BC
77        LD (HL),A
18DD      JR outerloop		

          numbers:
210298    LD HL 9802 //start of BTM+2
19        ADD HL,DE		
12        LD (HL),A  //write "Fx" number to BTM
13        INC DE
CB63      BIT 4,E
28D3      JR Z outerloop
7B        LD A E
C610      ADD A,#10
5F        LD E A
30CD      JR NC outerloop
14        INC D
18CA      JR outerloop

          refresh:
218299    LD HL 9982 //start of lower BTM
0100D6    LD BC D600
          loop2:		//loop for 256 bytes
0A        LD A,(BC)
22        LDI (HL),A
3E10      LD A #10
02        LD (BC),A	//clear mirror
03        INC BC
CB40      BIT 0,B
28F6      JR Z loop2  //that means B is still D6
18B8      JR outerloop		

          data:

FF 81 5B DB DB DB DB B9 //f3  pi
FF 3B B7 B7 B7 B7 B5 03 //f4  pirev
00 00 00 00 00 30 30 00 //f5  .
00 38 4C C6 C6 64 38 00 //f6  0
00 18 38 18 18 18 7E 00 //f7  1

          exit:
F3        DI   //disable interrupts, such as current music
218099    LD HL 9980
3EF3      LD A #F3 //pi
          loop3:
22        LDI (HL), A
CB54      BIT 2,H  //loop until 9C00
28FB      JR Z loop3:

          done:
18FE      JR done
It works as such: * First, it draws out the 8x8 tiles for pi, pi upside down ("pirev"), decimal point, 0, and 1. All other digits are already in the tileset. * Then, it takes input and changes the VRAM accordingly. Input is as follows: ** If input is from 0x00 to 0xED, the program draws to a cache which can later be dumped into VRAM at 9982. The drawing field is 8 rows by 16 columns. The input is considered as aaacbbbb, where aaa is the row, bbbb is the column, and c=0 for the pi tile and c=1 for the pirev tile. The choice of format is motivated by the fact that going down a row in VRAM is the same as adding 0x20=32 to the address. ** If input is 0xEE, the program dumps the cache into 9982, and then clears the cache using the black tile (value 0x10). ** If input is 0xEF, the program executes its ending sequence. ** If input is 0xF0-0xFF, the program writes directly to 9802, with the drawing field being 12 rows by 16 columns. The input's own number is written in as the value of the tile; all tiles of interest are in the Fx row. Tiles are written serially from left to right, then from top to bottom. Technically, the program can draw into the the bottom drawing field used by the first case of input above. * Its ending routine is a "fake crash" that disables interrupts, floods the bottom screen with pi tiles, then gets itself into an infinite loop (18 EF, or JR -2). And that's about it. There is no guarantee that VRAM writing occurs in a safe (to a real GB) manner; it does not check for status of FF40-FF41 (for reference, pages 51-53 of http://marc.rawer.de/Gameboy/Docs/GBCPUman.pdf ). ---- The C++ parser works as follows: * It recognizes the characters "0123456789abcdef|*s@." as well as uppercase variants. All other characters are delimiters. * If it first detects a character from "0123456789abcdef", then it expects immediately a second character from "01234567". This is for drawing to the cache representing VRAM at 9982. The first character represents the column, the second character the row. If it is immediately followed by '*', then it uses the pirev tile. Otherwise it uses the pi tile. * If it first detects the character '|', it counts to 15, inserting 0xED inputs along the way (the do-nothing-visible input), then inserts 0xEE (dump cache). It also resets the count to 1. * If it first detects the character '@', it counts to 8, inserting 0xED inputs along the way (the do-nothing-visible input), then inserts 0xEE (dump cache). * If it first detects 's', then it expects immediately a second character from ".0123456789". This is for drawing directly to VRAM at 9802. It uses the second character's corresponding tile. The parser does not insert the ending code (0xEF); it must be manually hex-edited. Also, the number of inputs between 0xEE (dump cache) commands should not exceed the counts to 15 or 8, whichever is appropriate. ---- Edit: Fixed pointer to data.
Posted: 3/14/2013 5:59 PM
Quote
Sanqui
Any
Player (26)
Joined: 4/25/2011
Posts: 33
There is no guarantee that VRAM writing occurs in a safe (to a real GB) manner; it does not check for status of FF40-FF41…
To achieve this for the graphics, you can call CopyVideoData ($1848). Put the graphics offest in de, the VRAM offset in hl and number of bytes divided by 16 in c first. The tilemap tiles may be more complicated. Pokémon Red keeps its own an internal tilemap buffer, which is however only activated when you're in a menu, so because you're in overworld mode at the time of exploit your current writes don't get overwritten each vblank. To enable it, I think you have to write 1 to H_AUTOBGTRANSFERENABLED ($FFBA) and then just modify the tilemap at starting at $C3A0. This may or may not be enough. Check out pokered (project page) for code which may be helpful; keep in mind it's not yet complete, however. I feel like this would have been better if it could run flawlessly on an actual Gameboy, instead of relying on known emulation inaccuracies. Anyway, I have to say the method by which you write arbitrary code with just a few (limited!) bytes is really impressive. Kudos! Happy half tau day, everybody.
ovo
Posted: 5/26/2013 6:01 AM
Quote
ais523
Editor, Player (44)
Joined: 7/11/2010
Posts: 1029
Someone did total control in a non-timing-sensitive way (i.e. possible without TASing: it looks like they used an emulator but not frame advance): http://forums.glitchcity.info/index.php/topic,6638.0.html The method's a lot slower than the one used in the current TAS, but interesting in its own way. I love seeing tricks that I thought were TAS-only done on console, by the way.
Posted: 6/26/2013 12:46 PM
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TASeditor
Editor, Skilled player (1537)
Joined: 7/9/2010
Posts: 1319
Glitchy TAS of 2015 NES TASer of 2014 Speedy TAS of 2014 NES TAS of 2013
Now they're able to save the program, they've written, into the battery save. Link to video Selling those catridges would be a frightened experience for those who don't understand this.
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Posted: 7/11/2013 9:15 AM
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Patashu
He/Him
Joined: 10/2/2005
Posts: 4045
Yo~! Pokemon Gold Total Control Hack might be a thing in the future if this can bootstrap a more powerful attack: Link to video http://forums.glitchcity.info/index.php/topic,6716.0.html
My Chiptune music, made in Famitracker: http://soundcloud.com/patashu My twitch. I stream mostly shmups & rhythm games http://twitch.tv/patashu My youtube, again shmups and rhythm games and misc stuff: http://youtube.com/user/patashu
Posted: 7/12/2013 4:57 AM
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ais523
Editor, Player (44)
Joined: 7/11/2010
Posts: 1029
The amount of space needed to write a message to the screen can't be that far off the amount of space needed to copy one byte between arbitrary memory locations, or to jump to an arbitrary memory location. You'd then just need somewhere in RAM to store the program while you were bootstrapping it. FWIW, I suspect the majority of old console games have total control glitches, just people tend not to be looking for them. Anything that crashes a game but only sometimes (like the Coin Case in G/S) is a prime candidate for looking at to see if it's exploitable.
Posted: 7/12/2013 8:53 AM
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Patashu
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Joined: 10/2/2005
Posts: 4045
ais523 wrote:
FWIW, I suspect the majority of old console games have total control glitches, just people tend not to be looking for them. Anything that crashes a game but only sometimes (like the Coin Case in G/S) is a prime candidate for looking at to see if it's exploitable.
I kind of agree, but Pokemon RBY/GSC is a special case - the program is a very special kind of hacky and corner cutting that few other games can claim to have. Plus, it's full of so many dynamically long strings, numbers, other data structures, etc that the player has many ways of manipulating. Never know though! Myself, I am wondering if this can be combined with a glitch like the 'Affirmative Action' glitch (showcased in the run below) to get access to enough things to pull off total control: Link to video The topic where arbitrary code execution with the coin case is being discussed also brought up this technique for mutating and cloning items: Link to video
My Chiptune music, made in Famitracker: http://soundcloud.com/patashu My twitch. I stream mostly shmups & rhythm games http://twitch.tv/patashu My youtube, again shmups and rhythm games and misc stuff: http://youtube.com/user/patashu
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