9 "github.com/holiman/uint256"
11 "github.com/bytom/bytom/errors"
14 type virtualMachine struct {
17 program []byte // the program currently executing
22 expansionReserved bool
24 // Stores the data parsed out of an opcode. Used as input to
25 // data-pushing opcodes.
28 // CHECKPREDICATE spawns a child vm with depth+1
31 // In each of these stacks, stack[len(stack)-1] is the top element.
36 // TraceOut - if non-nil - will receive trace output during
38 var TraceOut io.Writer
40 // Verify program by running VM
41 func Verify(context *Context, gasLimit int64) (gasLeft int64, err error) {
43 if r := recover(); r != nil {
44 if rErr, ok := r.(error); ok {
45 err = errors.Sub(ErrUnexpected, rErr)
47 err = errors.Wrap(ErrUnexpected, r)
52 if context.VMVersion != 1 {
53 return gasLimit, ErrUnsupportedVM
56 vm := &virtualMachine{
57 expansionReserved: context.TxVersion != nil && *context.TxVersion == 1,
58 program: context.Code,
62 stateData := context.StateData
63 for i, state := range stateData {
64 if err = vm.pushAlt(state, false); err != nil {
65 return vm.runLimit, errors.Wrapf(err, "pushing initial statedata %d", i)
69 args := context.Arguments
70 for i, arg := range args {
71 err = vm.push(arg, false)
73 return vm.runLimit, errors.Wrapf(err, "pushing initial argument %d", i)
78 if err == nil && vm.falseResult() {
79 err = ErrFalseVMResult
82 return vm.runLimit, wrapErr(err, vm, args)
85 // falseResult returns true iff the stack is empty or the top
87 func (vm *virtualMachine) falseResult() bool {
88 return len(vm.dataStack) == 0 || !AsBool(vm.dataStack[len(vm.dataStack)-1])
91 func (vm *virtualMachine) run() error {
92 for vm.pc = 0; vm.pc < uint32(len(vm.program)); { // handle vm.pc updates in step
101 func (vm *virtualMachine) step() error {
102 inst, err := ParseOp(vm.program, vm.pc)
107 vm.nextPC = vm.pc + inst.Len
110 opname := inst.Op.String()
111 fmt.Fprintf(TraceOut, "vm %d pc %d limit %d %s", vm.depth, vm.pc, vm.runLimit, opname)
112 if len(inst.Data) > 0 {
113 fmt.Fprintf(TraceOut, " %x", inst.Data)
115 fmt.Fprint(TraceOut, "\n")
118 if isExpansion[inst.Op] {
119 if vm.expansionReserved {
120 return ErrDisallowedOpcode
123 return vm.applyCost(1)
128 err = ops[inst.Op].fn(vm)
132 err = vm.applyCost(vm.deferredCost)
139 for i := len(vm.dataStack) - 1; i >= 0; i-- {
140 fmt.Fprintf(TraceOut, " stack %d: %x\n", len(vm.dataStack)-1-i, vm.dataStack[i])
147 func (vm *virtualMachine) push(data []byte, deferred bool) error {
148 cost := 8 + int64(len(data))
152 err := vm.applyCost(cost)
157 vm.dataStack = append(vm.dataStack, data)
161 func (vm *virtualMachine) pushAlt(data []byte, deferred bool) error {
162 cost := 8 + int64(len(data))
166 err := vm.applyCost(cost)
171 vm.altStack = append(vm.altStack, data)
176 func (vm *virtualMachine) pushBool(b bool, deferred bool) error {
177 return vm.push(BoolBytes(b), deferred)
180 func (vm *virtualMachine) pushInt64(n int64, deferred bool) error {
181 return vm.push(Int64Bytes(n), deferred)
184 func (vm *virtualMachine) pushBigInt(n *uint256.Int, deferred bool) error {
185 return vm.push(BigIntBytes(n), deferred)
188 func (vm *virtualMachine) pop(deferred bool) ([]byte, error) {
189 if len(vm.dataStack) == 0 {
190 return nil, ErrDataStackUnderflow
192 res := vm.dataStack[len(vm.dataStack)-1]
193 vm.dataStack = vm.dataStack[:len(vm.dataStack)-1]
195 cost := 8 + int64(len(res))
205 func (vm *virtualMachine) popInt64(deferred bool) (int64, error) {
206 bytes, err := vm.pop(deferred)
210 n, err := AsInt64(bytes)
214 func (vm *virtualMachine) popBigInt(deferred bool) (*uint256.Int, error) {
215 bytes, err := vm.pop(deferred)
220 return AsBigInt(bytes)
223 func (vm *virtualMachine) top() ([]byte, error) {
224 if len(vm.dataStack) == 0 {
225 return nil, ErrDataStackUnderflow
227 return vm.dataStack[len(vm.dataStack)-1], nil
230 // positive cost decreases runlimit, negative cost increases it
231 func (vm *virtualMachine) applyCost(n int64) error {
234 return ErrRunLimitExceeded
240 func (vm *virtualMachine) deferCost(n int64) {
244 func stackCost(stack [][]byte) int64 {
245 result := int64(8 * len(stack))
246 for _, item := range stack {
247 result += int64(len(item))
252 func wrapErr(err error, vm *virtualMachine, args [][]byte) error {
257 dis, errDis := Disassemble(vm.program)
262 dataArgs := make([]string, 0, len(args))
263 for _, a := range args {
264 dataArgs = append(dataArgs, hex.EncodeToString(a))
267 return errors.Wrap(err, fmt.Sprintf("%s [prog %x = %s; args %s]", err.Error(), vm.program, dis, strings.Join(dataArgs, " ")))