mipsevm: step witness type, update syscall handling

mipsevm/evm_test.go

@@ -3,7 +3,6 @@ package mipsevm
 import (
 	"bytes"
 	"debug/elf"
-	"encoding/binary"
 	"io"
 	"math/big"
 	"os"
@@ -64,7 +63,7 @@ func TestEVM(t *testing.T) {
 			err = LoadUnicorn(state, mu)
 			require.NoError(t, err, "load state into unicorn")
 
-			us, err := NewUnicornState(mu, state, os.Stdout, os.Stderr)
+			us, err := NewUnicornState(mu, state, nil, os.Stdout, os.Stderr)
 			require.NoError(t, err, "hook unicorn to state")
 
 			for i := 0; i < 1000; i++ {
@@ -74,8 +73,8 @@ func TestEVM(t *testing.T) {
 				insn := state.Memory.GetMemory(state.PC)
 				t.Logf("step: %4d pc: 0x%08x insn: 0x%08x", state.Step, state.PC, insn)
 
-				stateData, proofData := us.Step(true)
-				input := FormatStepInput(stateData, proofData)
+				stepWitness := us.Step(true)
+				input := stepWitness.EncodeStepInput()
 				startingGas := uint64(30_000_000)
 
 				// we take a snapshot so we can clean up the state, and isolate the logs of this instruction run.
@@ -108,21 +107,6 @@ func TestEVM(t *testing.T) {
 	}
 }
 
-func FormatStepInput(stateData, proofData []byte) []byte {
-	stateHash := crypto.Keccak256Hash(stateData)
-	var input []byte
-	input = append(input, StepBytes4...)
-	input = append(input, stateHash[:]...)
-	input = append(input, uint32ToBytes32(32*3)...)                           // state data offset in bytes
-	input = append(input, uint32ToBytes32(32*3+32+uint32(len(stateData)))...) // proof data offset in bytes
-
-	input = append(input, uint32ToBytes32(uint32(len(stateData)))...) // state data length in bytes
-	input = append(input, stateData[:]...)
-	input = append(input, uint32ToBytes32(uint32(len(proofData)))...) // proof data length in bytes
-	input = append(input, proofData[:]...)
-	return input
-}
-
 func TestMinimalEVM(t *testing.T) {
 	contracts, err := LoadContracts()
 	require.NoError(t, err)
@@ -151,7 +135,7 @@ func TestMinimalEVM(t *testing.T) {
 	err = LoadUnicorn(state, mu)
 	require.NoError(t, err, "load state into unicorn")
 	var stdOutBuf, stdErrBuf bytes.Buffer
-	us, err := NewUnicornState(mu, state, io.MultiWriter(&stdOutBuf, os.Stdout), io.MultiWriter(&stdErrBuf, os.Stderr))
+	us, err := NewUnicornState(mu, state, nil, io.MultiWriter(&stdOutBuf, os.Stdout), io.MultiWriter(&stdErrBuf, os.Stderr))
 	require.NoError(t, err, "hook unicorn to state")
 
 	env, evmState := NewEVMEnv(contracts, addrs)
@@ -169,8 +153,8 @@ func TestMinimalEVM(t *testing.T) {
 			t.Logf("step: %4d pc: 0x%08x insn: 0x%08x", state.Step, state.PC, insn)
 		}
 
-		stateData, proofData := us.Step(true)
-		input := FormatStepInput(stateData, proofData)
+		stepWitness := us.Step(true)
+		input := stepWitness.EncodeStepInput()
 		startingGas := uint64(30_000_000)
 
 		// we take a snapshot so we can clean up the state, and isolate the logs of this instruction run.
@@ -204,9 +188,3 @@ func TestMinimalEVM(t *testing.T) {
 	require.Equal(t, "hello world!", stdOutBuf.String(), "stdout says hello")
 	require.Equal(t, "", stdErrBuf.String(), "stderr silent")
 }
-
-func uint32ToBytes32(v uint32) []byte {
-	var out [32]byte
-	binary.BigEndian.PutUint32(out[32-4:], v)
-	return out[:]
-}

mipsevm/state.go

@@ -4,6 +4,7 @@ import (
 	"encoding/binary"
 
 	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/common/hexutil"
 )
 
 type State struct {
@@ -24,6 +25,13 @@ type State struct {
 	Step uint64 `json:"step"`
 
 	Registers [32]uint32 `json:"registers"`
+
+	// LastHint is optional metadata, and not part of the VM state itself.
+	// It is used to remember the last pre-image hint,
+	// so a VM can start from any state without fetching prior pre-images,
+	// and instead just repeat the last hint on setup,
+	// to make sure pre-image requests can be served.
+	LastHint hexutil.Bytes `json:"lastHint,omitempty"`
 }
 
 func (s *State) EncodeWitness() []byte {
@@ -49,5 +57,3 @@ func (s *State) EncodeWitness() []byte {
 	}
 	return out
 }
-
-// TODO convert access-list to calldata and state-sets for EVM

mipsevm/state_test.go

@@ -58,7 +58,7 @@ func TestState(t *testing.T) {
 			err = LoadUnicorn(state, mu)
 			require.NoError(t, err, "load state into unicorn")
 
-			us, err := NewUnicornState(mu, state, os.Stdout, os.Stderr)
+			us, err := NewUnicornState(mu, state, nil, os.Stdout, os.Stderr)
 			require.NoError(t, err, "hook unicorn to state")
 
 			for i := 0; i < 1000; i++ {
@@ -92,7 +92,7 @@ func TestMinimal(t *testing.T) {
 	err = LoadUnicorn(state, mu)
 	require.NoError(t, err, "load state into unicorn")
 	var stdOutBuf, stdErrBuf bytes.Buffer
-	us, err := NewUnicornState(mu, state, io.MultiWriter(&stdOutBuf, os.Stdout), io.MultiWriter(&stdErrBuf, os.Stderr))
+	us, err := NewUnicornState(mu, state, nil, io.MultiWriter(&stdOutBuf, os.Stdout), io.MultiWriter(&stdErrBuf, os.Stderr))
 	require.NoError(t, err, "hook unicorn to state")
 
 	for i := 0; i < 400_000; i++ {

mipsevm/unicorn.go

@@ -10,6 +10,11 @@ import (
 	uc "github.com/unicorn-engine/unicorn/bindings/go/unicorn"
 )
 
+type PreimageOracle interface {
+	Hint(v []byte)
+	GetPreimage(k [32]byte) []byte
+}
+
 type UnicornState struct {
 	sync.Mutex
 
@@ -24,16 +29,41 @@ type UnicornState struct {
 	memProofEnabled bool
 	memProof        [28 * 32]byte
 
+	preimageOracle PreimageOracle
+
+	// number of bytes last read from the oracle.
+	// The read data is preimage[state.PreimageOffset-lastPreimageRead : state.PreimageOffset]
+	// when inspecting the post-step state.
+	lastPreimageRead uint32
+
+	// cached pre-image data for state.PreimageKey
+	lastPreimage []byte
+
 	onStep func()
 }
 
-// TODO add pre-image oracle
-func NewUnicornState(mu uc.Unicorn, state *State, stdOut, stdErr io.Writer) (*UnicornState, error) {
+const (
+	fdStdin         = 0
+	fdStdout        = 1
+	fdStderr        = 2
+	fdHintRead      = 3
+	fdHintWrite     = 4
+	fdPreimageRead  = 5
+	fdPreimageWrite = 6
+)
+
+const (
+	MipsEBADF  = 0x9
+	MipsEINVAL = 0x16
+)
+
+func NewUnicornState(mu uc.Unicorn, state *State, po PreimageOracle, stdOut, stdErr io.Writer) (*UnicornState, error) {
 	m := &UnicornState{
 		mu:             mu,
 		state:          state,
 		stdOut:         stdOut,
 		stdErr:         stdErr,
+		preimageOracle: po,
 	}
 	st := m.state
 
@@ -43,33 +73,48 @@ func NewUnicornState(mu uc.Unicorn, state *State, stdOut, stdErr io.Writer) (*Un
 			log.Fatal("invalid interrupt ", intno, " at step ", st.Step)
 		}
 
-		syscallNum, _ := mu.RegRead(uc.MIPS_REG_V0)
+		syscallNum := st.Registers[2] // v0
+		v0 := uint32(0)
+		//v1 := uint32(0)
+
+		a0 := st.Registers[4]
+		a1 := st.Registers[5]
+		a2 := st.Registers[6]
 
 		fmt.Printf("syscall: %d\n", syscallNum)
-		v0 := uint64(0)
 		switch syscallNum {
 		case 4004: // write
-			fd, _ := mu.RegRead(uc.MIPS_REG_A0)
-			addr, _ := mu.RegRead(uc.MIPS_REG_A1)
-			count, _ := mu.RegRead(uc.MIPS_REG_A2)
+			fd := a0
+			addr := a1
+			count := a2
 			switch fd {
-			case 1:
-				_, _ = io.Copy(stdOut, st.Memory.ReadMemoryRange(uint32(addr), uint32(count)))
-			case 2:
-				_, _ = io.Copy(stdErr, st.Memory.ReadMemoryRange(uint32(addr), uint32(count)))
+			case fdStdout:
+				_, _ = io.Copy(stdOut, st.Memory.ReadMemoryRange(addr, count))
+				v0 = count
+			case fdStderr:
+				_, _ = io.Copy(stdErr, st.Memory.ReadMemoryRange(addr, count))
+				v0 = count
+			case fdHintWrite:
+				hint, _ := io.ReadAll(st.Memory.ReadMemoryRange(addr, count))
+				v0 = count
+				po.Hint(hint)
+			case fdPreimageWrite:
+				// TODO
+				v0 = count
 			default:
+				v0 = 0xFFffFFff
+				//v1 = MipsEBADF
 				// ignore other output data
 			}
 		case 4090: // mmap
-			a0, _ := mu.RegRead(uc.MIPS_REG_A0)
-			sz, _ := mu.RegRead(uc.MIPS_REG_A1)
+			sz := a1
 			if sz&pageAddrMask != 0 { // adjust size to align with page size
 				sz += pageSize - (sz & pageAddrMask)
 			}
 			if a0 == 0 {
-				v0 = uint64(st.Heap)
+				v0 = st.Heap
 				fmt.Printf("mmap heap 0x%x size 0x%x\n", v0, sz)
-				st.Heap += uint32(sz)
+				st.Heap += sz
 			} else {
 				v0 = a0
 				fmt.Printf("mmap hint 0x%x size 0x%x\n", v0, sz)
@@ -77,9 +122,9 @@ func NewUnicornState(mu uc.Unicorn, state *State, stdOut, stdErr io.Writer) (*Un
 			// Go does this thing where it first gets memory with PROT_NONE,
 			// and then mmaps with a hint with prot=3 (PROT_READ|WRITE).
 			// We can ignore the NONE case, to avoid duplicate/overlapping mmap calls to unicorn.
-			prot, _ := mu.RegRead(uc.MIPS_REG_A2)
+			prot := a2
 			if prot != 0 {
-				if err := mu.MemMap(v0, sz); err != nil {
+				if err := mu.MemMap(uint64(v0), uint64(sz)); err != nil {
 					log.Fatalf("mmap fail: %v", err)
 				}
 			}
@@ -91,7 +136,7 @@ func NewUnicornState(mu uc.Unicorn, state *State, stdOut, stdErr io.Writer) (*Un
 			st.ExitCode = uint8(v0)
 			return
 		}
-		mu.RegWrite(uc.MIPS_REG_V0, v0)
+		mu.RegWrite(uc.MIPS_REG_V0, uint64(v0))
 		mu.RegWrite(uc.MIPS_REG_A3, 0)
 	}, 0, ^uint64(0))
 	if err != nil {
@@ -165,15 +210,16 @@ func NewUnicornState(mu uc.Unicorn, state *State, stdOut, stdErr io.Writer) (*Un
 	return m, nil
 }
 
-func (m *UnicornState) Step(proof bool) (stateWitness []byte, memProof []byte) {
+func (m *UnicornState) Step(proof bool) (wit *StepWitness) {
 	m.memProofEnabled = proof
 	m.lastMemAccess = ^uint32(0)
 
 	if proof {
-		stateWitness = m.state.EncodeWitness()
-
 		insnProof := m.state.Memory.MerkleProof(m.state.PC)
-		memProof = append(memProof, insnProof[:]...)
+		wit = &StepWitness{
+			state:    m.state.EncodeWitness(),
+			memProof: insnProof[:],
+		}
 	}
 
 	insn := m.state.Memory.GetMemory(m.state.PC)
@@ -222,7 +268,12 @@ func (m *UnicornState) Step(proof bool) (stateWitness []byte, memProof []byte) {
 	})
 
 	if proof {
-		memProof = append(memProof, m.memProof[:]...)
+		wit.memProof = append(wit.memProof, m.memProof[:]...)
+		if m.lastPreimageRead > 0 {
+			wit.preimageOffset = m.state.PreimageOffset
+			wit.preimageKey = m.state.PreimageKey
+			wit.preimageValue = m.lastPreimage
+		}
 	}
 
 	// count it

mipsevm/witness.go

+package mipsevm
+
+import (
+	"encoding/binary"
+
+	"github.com/ethereum/go-ethereum/crypto"
+)
+
+type StepWitness struct {
+	state []byte
+
+	memProof []byte
+
+	preimageKey    [32]byte // zeroed when no pre-image is accessed
+	preimageValue  []byte
+	preimageOffset uint32
+}
+
+func uint32ToBytes32(v uint32) []byte {
+	var out [32]byte
+	binary.BigEndian.PutUint32(out[32-4:], v)
+	return out[:]
+}
+
+func (wit *StepWitness) EncodeStepInput() []byte {
+	stateHash := crypto.Keccak256Hash(wit.state)
+	var input []byte
+	input = append(input, StepBytes4...)
+	input = append(input, stateHash[:]...)
+	input = append(input, uint32ToBytes32(32*3)...)                           // state data offset in bytes
+	input = append(input, uint32ToBytes32(32*3+32+uint32(len(wit.state)))...) // proof data offset in bytes
+
+	input = append(input, uint32ToBytes32(uint32(len(wit.state)))...) // state data length in bytes
+	input = append(input, wit.state[:]...)
+	input = append(input, uint32ToBytes32(uint32(len(wit.memProof)))...) // proof data length in bytes
+	input = append(input, wit.memProof[:]...)
+	return input
+}
+
+func (wit *StepWitness) EncodePreimageOracleInput() []byte {
+	if wit.preimageKey == ([32]byte{}) {
+		return nil
+	}
+	// TODO
+	return nil
+}