Merge pull request #1150 from fjl/fix-jumpdest

core/vm: improve JUMPDEST analysis
This commit is contained in:
Jeffrey Wilcke 2015-06-03 09:11:56 -07:00
commit 122d2db095
4 changed files with 175 additions and 32 deletions

View File

@ -3,34 +3,45 @@ package vm
import (
"math/big"
"gopkg.in/fatih/set.v0"
"github.com/ethereum/go-ethereum/common"
)
type destinations struct {
set *set.Set
var bigMaxUint64 = new(big.Int).SetUint64(^uint64(0))
// destinations stores one map per contract (keyed by hash of code).
// The maps contain an entry for each location of a JUMPDEST
// instruction.
type destinations map[common.Hash]map[uint64]struct{}
// has checks whether code has a JUMPDEST at dest.
func (d destinations) has(codehash common.Hash, code []byte, dest *big.Int) bool {
// PC cannot go beyond len(code) and certainly can't be bigger than 64bits.
// Don't bother checking for JUMPDEST in that case.
if dest.Cmp(bigMaxUint64) > 0 {
return false
}
m, analysed := d[codehash]
if !analysed {
m = jumpdests(code)
d[codehash] = m
}
_, ok := m[dest.Uint64()]
return ok
}
func (d *destinations) Has(dest *big.Int) bool {
return d.set.Has(string(dest.Bytes()))
}
func (d *destinations) Add(dest *big.Int) {
d.set.Add(string(dest.Bytes()))
}
func analyseJumpDests(code []byte) (dests *destinations) {
dests = &destinations{set.New()}
// jumpdests creates a map that contains an entry for each
// PC location that is a JUMPDEST instruction.
func jumpdests(code []byte) map[uint64]struct{} {
m := make(map[uint64]struct{})
for pc := uint64(0); pc < uint64(len(code)); pc++ {
var op OpCode = OpCode(code[pc])
switch op {
case PUSH1, PUSH2, PUSH3, PUSH4, PUSH5, PUSH6, PUSH7, PUSH8, PUSH9, PUSH10, PUSH11, PUSH12, PUSH13, PUSH14, PUSH15, PUSH16, PUSH17, PUSH18, PUSH19, PUSH20, PUSH21, PUSH22, PUSH23, PUSH24, PUSH25, PUSH26, PUSH27, PUSH28, PUSH29, PUSH30, PUSH31, PUSH32:
a := uint64(op) - uint64(PUSH1) + 1
pc += a
case JUMPDEST:
dests.Add(big.NewInt(int64(pc)))
m[pc] = struct{}{}
}
}
return
return m
}

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@ -16,6 +16,8 @@ type Context struct {
caller ContextRef
self ContextRef
jumpdests destinations // result of JUMPDEST analysis.
Code []byte
CodeAddr *common.Address
@ -24,10 +26,17 @@ type Context struct {
Args []byte
}
// Create a new context for the given data items
// Create a new context for the given data items.
func NewContext(caller ContextRef, object ContextRef, value, gas, price *big.Int) *Context {
c := &Context{caller: caller, self: object, Args: nil}
if parent, ok := caller.(*Context); ok {
// Reuse JUMPDEST analysis from parent context if available.
c.jumpdests = parent.jumpdests
} else {
c.jumpdests = make(destinations)
}
// Gas should be a pointer so it can safely be reduced through the run
// This pointer will be off the state transition
c.Gas = gas //new(big.Int).Set(gas)

View File

@ -71,18 +71,22 @@ func (self *Vm) Run(context *Context, callData []byte) (ret []byte, err error) {
}
}
var (
op OpCode
// Don't bother with the execution if there's no code.
if len(code) == 0 {
return context.Return(nil), nil
}
destinations = analyseJumpDests(context.Code)
mem = NewMemory()
stack = newStack()
pc = new(big.Int)
statedb = self.env.State()
var (
op OpCode
codehash = crypto.Sha3Hash(code)
mem = NewMemory()
stack = newStack()
pc = new(big.Int)
statedb = self.env.State()
jump = func(from *big.Int, to *big.Int) error {
nop := context.GetOp(to)
if !destinations.Has(to) {
if !context.jumpdests.has(codehash, code, to) {
nop := context.GetOp(to)
return fmt.Errorf("invalid jump destination (%v) %v", nop, to)
}
@ -95,11 +99,6 @@ func (self *Vm) Run(context *Context, callData []byte) (ret []byte, err error) {
}
)
// Don't bother with the execution if there's no code.
if len(code) == 0 {
return context.Return(nil), nil
}
for {
// The base for all big integer arithmetic
base := new(big.Int)

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