allow mips to overwrite the output

README.md

@@ -92,9 +92,8 @@ ID=0 BLOCK=13284469 npx hardhat run scripts/assert.js --network hosthat
 # compute real MIPS checkpoint
 minigeth/go-ethereum 13284491 && mipsevm/mipsevm 13284491
 
-# alternate fake MIPS checkpoint
+# alternate fake MIPS checkpoint (will modify output file)
 BASEDIR=/tmp/cannon_fault minigeth/go-ethereum 13284491 && OUTPUTFAULT=1 BASEDIR=/tmp/cannon_fault mipsevm/mipsevm 13284491
-python3 -c 'f="/tmp/cannon_fault/0_13284491/output";o=b"\xba\xba\xba\xba"+open(f, "rb").read()[4:]; open(f, "wb").write(o)'
 
 # start challenge
 BASEDIR=/tmp/cannon_fault BLOCK=13284491 npx hardhat run scripts/challenge.js --network hosthat

mipsevm/main.go

 package main
 
 import (
+	"bytes"
+	"encoding/binary"
 	"fmt"
 	"io/ioutil"
 	"os"
@@ -94,7 +96,27 @@ func main() {
 	}
 
 	if target == -1 {
+		output_filename := fmt.Sprintf("%s/output", root)
+		outputs, err := ioutil.ReadFile(output_filename)
+		check(err)
+		real := append([]byte{0x13, 0x37, 0xf0, 0x0d}, outputs...)
+
+		output := []byte{}
+		for i := 0; i < 0x44; i += 4 {
+			t := make([]byte, 4)
+			binary.BigEndian.PutUint32(t, ram[uint32(0x30000800+i)])
+			output = append(output, t...)
+		}
+
+		if bytes.Compare(real, output) != 0 {
+			fmt.Println("MISMATCH OUTPUT, OVERWRITING!!!")
+			ioutil.WriteFile(output_filename, output[4:], 0644)
+		} else {
+			fmt.Println("output match")
+		}
+
 		WriteCheckpoint(ram, fmt.Sprintf("%s/checkpoint_final.json", root), lastStep)
+
 	}
 
 	// step 2 (optional), validate each 1 million chunk in EVM