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core/vm: Address review concerns

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This commit is contained in:
Martin Holst Swende 2017-08-14 10:57:54 +02:00
parent f4b5f67ee0
commit 967e097faa
1 changed files with 19 additions and 14 deletions
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33
core/vm/analysis.go
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@ -25,7 +25,7 @@ import (
// 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][]byte
type destinations map[common.Hash]bitvec
// has checks whether code has a JUMPDEST at dest.
func (d destinations) has(codehash common.Hash, code []byte, dest *big.Int) bool {
@ -41,20 +41,25 @@ func (d destinations) has(codehash common.Hash, code []byte, dest *big.Int) bool
m = jumpdests(code)
d[codehash] = m
}
return OpCode(code[udest]) == JUMPDEST && (m[udest/8]&(0x80>>(udest%8))) == 0
return OpCode(code[udest]) == JUMPDEST && m.codeSegment(udest)
// return (m[udest/8] & (1 << (udest % 8))) != 0
}
type bitvec struct {
m []byte
// bitvec is a bit vector which maps bytes in a program
// An unset bit means the byte is a code-segemnt, a set bit means it's data-segment
type bitvec []byte
func (bits *bitvec) set(pos uint64) {
(*bits)[pos/8] |= 0x80 >> (pos % 8)
}
func (bits *bitvec) set8(pos uint64) {
(*bits)[pos/8] |= 0xFF >> (pos % 8)
(*bits)[pos/8+1] |= ^(0xFF >> (pos % 8))
}
func (bits *bitvec) addone(pos uint64) {
bits.m[pos/8] |= 0x80 >> (pos % 8)
}
func (bits *bitvec) addOneByte(pos uint64) {
bits.m[pos/8] |= 0xFF >> (pos % 8)
bits.m[pos/8+1] |= ^(0xFF >> (pos % 8))
// codeSegment checks if the position is in a code segment
func (bits *bitvec) codeSegment(pos uint64) bool {
return ((*bits)[pos/8] & (0x80 >> (pos % 8))) == 0
}
// jumpdests creates a map that contains an entry for each
@ -64,7 +69,7 @@ func jumpdests(code []byte) []byte {
// ends with a PUSH32, the algorithm will push zeroes onto the
// bitvector outside the bounds of the actual code.
m := make([]byte, len(code)/8+1+4)
bits := &bitvec{m}
bits := bitvec(m)
for pc := uint64(0); pc < uint64(len(code)); {
op := OpCode(code[pc])
@ -72,16 +77,16 @@ func jumpdests(code []byte) []byte {
numbits := op - PUSH1 + 1
pc++
for ; numbits >= 8; numbits -= 8 {
bits.addOneByte(pc) // 8
bits.set8(pc) // 8
pc += 8
}
for ; numbits > 0; numbits-- {
bits.addone(pc)
bits.set(pc)
pc++
}
} else {
pc++
}
}
return bits.m
return bits
}