move stuff, more readme, add back DenyStateTransition

README.md

@@ -16,7 +16,7 @@ It's half geth, half of what I think truebit was supposed to be. When it's done,
 
 ```
 minigeth -- A standalone "geth" capable of computing a block transition
-mipigo -- minigeth compiled for MIPS. Outputs a binary that's run and mapped at 0x0
+mipigo -- minigeth compiled for MIPS. Outputs a MIPS binary that's run and mapped at 0x0
 mipsevm -- A MIPS runtime in the EVM (see also contracts/)
 ```
 

contracts/Challenge.sol

@@ -164,4 +164,19 @@ contract Challenge {
     
     emit ChallengerWins(challengeId);
   }
+
+  function DenyStateTransition(uint256 challengeId, bytes32 finalRiscState) external {
+    Chal storage c = challenges[challengeId];
+    require(c.challenger != address(0), "invalid challenge");
+    require(owner == msg.sender, "must be owner");
+    require(c.L + 1 == c.R, "binary search not finished");
+
+    // it's 0 if you agree with all attacker states except the final one
+    // in which case, you get a free pass to submit now
+    require(c.defendedState[c.R] == finalRiscState || c.defendedState[c.R] == bytes32(0), "must be consistent with state");
+    require(mips.Step(c.defendedState[c.L]) == finalRiscState, "wrong asserted state");
+
+    // consider the challenger mocked
+    emit ChallengerLoses(challengeId);
+  }
 }

mipigo/compile.py

@@ -5,6 +5,7 @@ import struct
 from rangetree import RangeTree
 from elftools.elf.elffile import ELFFile
 
+# TODO: refactor this to not use unicorn
 from unicorn import *
 from unicorn.mips_const import *
 

mipsevm/README

 Running MIPS processor on chain
 
-We considered using
-https://github.com/cartesi/machine-solidity-step
-but it's around 5000 lines!
-
-* We don't have any virtual memory
-* We don't support any CSRs
-* MIPS is two files, MIPS + MIPSMemory
-
-cartesi also has a second version of the emulator in Rust. we use the EVM one in both places
-
 Tests from https://github.com/grantae/OpenMIPS/tree/master/software/test/macro/tests
 Licensed GPLv3
 
@@ -24,9 +14,7 @@ Instruction set used by minigeth, 55 instructions:
  'sb', 'sll', 'sllv', 'slt', 'slti', 'sltiu', 'sltu', 'sra', 'srl', 'srlv', 'subu', 'sw', 'swr', 'sync', 'syscall',
  'xor', 'xori']
 
- STEPS=100000000 ./evm.sh unicorn ../mipigo/minigeth.bin
-
- There's three ways to run this, see "run_<type>":
+ There's three ways to run the embedded MIPS engine, see "run_<type>":
  * unicorn -- fastest, uses none of the solidity
- * evm -- uses MIPS.sol, but stubs MIPSMemory.sol and doesn't compute the merkle trie
- * chain -- uses MIPS.sol + MIPSMemory.sol, will actually run on chain like this
+ * evm -- uses MIPS.sol, but stubs MIPSMemory.sol to SLOAD/SSTORE and doesn't compute the merkle trie
+ * chain -- uses MIPS.sol + MIPSMemory.sol, slowest, will actually run on chain like this