neo-go/pkg/vm/context.go
Anna Shaleva fe1f0a7245 core: introduce CheckReturnState constants
At the moment we should have 3 possible options to check return state
during vm context unloading:
	* no check
	* ensure the stack is empty
	* ensure the stack is not empty

It is necessary to distinguish them because new _deploy method shouldn't
left anything on stack. Example: if we use _deploy method before some
ordinary contract method which returns one value. Without these changes
the contract invocation will fail due to 2 elements on stack left after
invocation (the first `null` element is from _deploy, the second element
is return-value from the ordinary contract method).
2020-10-13 19:14:44 +03:00

264 lines
6.6 KiB
Go

package vm
import (
"encoding/binary"
"errors"
"math/big"
"github.com/nspcc-dev/neo-go/pkg/crypto/hash"
"github.com/nspcc-dev/neo-go/pkg/smartcontract"
"github.com/nspcc-dev/neo-go/pkg/util"
"github.com/nspcc-dev/neo-go/pkg/vm/opcode"
"github.com/nspcc-dev/neo-go/pkg/vm/stackitem"
)
// Context represents the current execution context of the VM.
type Context struct {
// Instruction pointer.
ip int
// The next instruction pointer.
nextip int
// The raw program script.
prog []byte
// Breakpoints.
breakPoints []int
// Evaluation stack pointer.
estack *Stack
static *Slot
local *Slot
arguments *Slot
// Exception context stack pointer.
tryStack *Stack
// Script hash of the prog.
scriptHash util.Uint160
// Caller's contract script hash.
callingScriptHash util.Uint160
// Call flags this context was created with.
callFlag smartcontract.CallFlag
// CheckReturn specifies if amount of return values needs to be checked.
CheckReturn CheckReturnState
}
// CheckReturnState represents possible states of stack after opcode.RET was processed.
type CheckReturnState byte
const (
// NoCheck performs no return values check.
NoCheck CheckReturnState = 0
// EnsureIsEmpty checks that stack is empty and panics if not.
EnsureIsEmpty CheckReturnState = 1
// EnsureNotEmpty checks that stack contains not more than 1 element and panics if not.
// It pushes stackitem.Null on stack in case if there's no elements.
EnsureNotEmpty CheckReturnState = 2
)
var errNoInstParam = errors.New("failed to read instruction parameter")
// NewContext returns a new Context object.
func NewContext(b []byte) *Context {
return &Context{
prog: b,
breakPoints: []int{},
}
}
// NextIP returns next instruction pointer.
func (c *Context) NextIP() int {
return c.nextip
}
// Next returns the next instruction to execute with its parameter if any. After
// its invocation the instruction pointer points to the instruction being
// returned.
func (c *Context) Next() (opcode.Opcode, []byte, error) {
var err error
c.ip = c.nextip
if c.ip >= len(c.prog) {
return opcode.RET, nil, nil
}
var instrbyte = c.prog[c.ip]
instr := opcode.Opcode(instrbyte)
c.nextip++
var numtoread int
switch instr {
case opcode.PUSHDATA1:
if c.nextip >= len(c.prog) {
err = errNoInstParam
} else {
numtoread = int(c.prog[c.nextip])
c.nextip++
}
case opcode.PUSHDATA2:
if c.nextip+1 >= len(c.prog) {
err = errNoInstParam
} else {
numtoread = int(binary.LittleEndian.Uint16(c.prog[c.nextip : c.nextip+2]))
c.nextip += 2
}
case opcode.PUSHDATA4:
if c.nextip+3 >= len(c.prog) {
err = errNoInstParam
} else {
var n = binary.LittleEndian.Uint32(c.prog[c.nextip : c.nextip+4])
if n > stackitem.MaxSize {
return instr, nil, errors.New("parameter is too big")
}
numtoread = int(n)
c.nextip += 4
}
case opcode.JMP, opcode.JMPIF, opcode.JMPIFNOT, opcode.JMPEQ, opcode.JMPNE,
opcode.JMPGT, opcode.JMPGE, opcode.JMPLT, opcode.JMPLE,
opcode.CALL, opcode.ISTYPE, opcode.CONVERT, opcode.NEWARRAYT,
opcode.ENDTRY,
opcode.INITSSLOT, opcode.LDSFLD, opcode.STSFLD, opcode.LDARG, opcode.STARG, opcode.LDLOC, opcode.STLOC:
numtoread = 1
case opcode.INITSLOT, opcode.TRY:
numtoread = 2
case opcode.JMPL, opcode.JMPIFL, opcode.JMPIFNOTL, opcode.JMPEQL, opcode.JMPNEL,
opcode.JMPGTL, opcode.JMPGEL, opcode.JMPLTL, opcode.JMPLEL,
opcode.ENDTRYL,
opcode.CALLL, opcode.SYSCALL, opcode.PUSHA:
numtoread = 4
case opcode.TRYL:
numtoread = 8
default:
if instr <= opcode.PUSHINT256 {
numtoread = 1 << instr
} else {
// No parameters, can just return.
return instr, nil, nil
}
}
if c.nextip+numtoread-1 >= len(c.prog) {
err = errNoInstParam
}
if err != nil {
return instr, nil, err
}
parameter := make([]byte, numtoread)
copy(parameter, c.prog[c.nextip:c.nextip+numtoread])
c.nextip += numtoread
return instr, parameter, nil
}
// IP returns current instruction offset in the context script.
func (c *Context) IP() int {
return c.ip
}
// LenInstr returns the number of instructions loaded.
func (c *Context) LenInstr() int {
return len(c.prog)
}
// CurrInstr returns the current instruction and opcode.
func (c *Context) CurrInstr() (int, opcode.Opcode) {
return c.ip, opcode.Opcode(c.prog[c.ip])
}
// Copy returns an new exact copy of c.
func (c *Context) Copy() *Context {
ctx := new(Context)
*ctx = *c
return ctx
}
// GetCallFlags returns calling flags context was created with.
func (c *Context) GetCallFlags() smartcontract.CallFlag {
return c.callFlag
}
// Program returns the loaded program.
func (c *Context) Program() []byte {
return c.prog
}
// ScriptHash returns a hash of the script in the current context.
func (c *Context) ScriptHash() util.Uint160 {
if c.scriptHash.Equals(util.Uint160{}) {
c.scriptHash = hash.Hash160(c.prog)
}
return c.scriptHash
}
// Value implements stackitem.Item interface.
func (c *Context) Value() interface{} {
return c
}
// Dup implements stackitem.Item interface.
func (c *Context) Dup() stackitem.Item {
return c
}
// TryBool implements stackitem.Item interface.
func (c *Context) TryBool() (bool, error) { panic("can't convert Context to Bool") }
// TryBytes implements stackitem.Item interface.
func (c *Context) TryBytes() ([]byte, error) {
return nil, errors.New("can't convert Context to ByteArray")
}
// TryInteger implements stackitem.Item interface.
func (c *Context) TryInteger() (*big.Int, error) {
return nil, errors.New("can't convert Context to Integer")
}
// Type implements stackitem.Item interface.
func (c *Context) Type() stackitem.Type { panic("Context cannot appear on evaluation stack") }
// Convert implements stackitem.Item interface.
func (c *Context) Convert(_ stackitem.Type) (stackitem.Item, error) {
panic("Context cannot be converted to anything")
}
// Equals implements stackitem.Item interface.
func (c *Context) Equals(s stackitem.Item) bool {
return c == s
}
func (c *Context) atBreakPoint() bool {
for _, n := range c.breakPoints {
if n == c.nextip {
return true
}
}
return false
}
func (c *Context) String() string {
return "execution context"
}
// getContextScriptHash returns script hash of the invocation stack element
// number n.
func (v *VM) getContextScriptHash(n int) util.Uint160 {
element := v.Istack().Peek(n)
if element == nil {
return util.Uint160{}
}
ctxIface := element.Value()
ctx := ctxIface.(*Context)
return ctx.ScriptHash()
}
// PushContextScriptHash pushes to evaluation stack the script hash of the
// invocation stack element number n.
func (v *VM) PushContextScriptHash(n int) error {
h := v.getContextScriptHash(n)
v.Estack().PushVal(h.BytesBE())
return nil
}