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Merge pull request #14582 from holiman/jumpdest_improv 

core/vm: improve jumpdest analysis
This commit is contained in:
Péter Szilágyi 2017-11-15 10:52:14 +02:00 committed by GitHub
parent 43c8a1914c 96ddf27a48
commit bce5d837b5
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GPG Key ID: 4AEE18F83AFDEB23
2 changed files with 96 additions and 14 deletions
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57
core/vm/analysis.go
View File

@ -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 {
@ -38,24 +38,53 @@ func (d destinations) has(codehash common.Hash, code []byte, dest *big.Int) bool
m, analysed := d[codehash]
if !analysed {
m = jumpdests(code)
m = codeBitmap(code)
d[codehash] = m
}
return (m[udest/8] & (1 << (udest % 8))) != 0
return OpCode(code[udest]) == JUMPDEST && m.codeSegment(udest)
}
// jumpdests creates a map that contains an entry for each
// PC location that is a JUMPDEST instruction.
func jumpdests(code []byte) []byte {
m := make([]byte, len(code)/8+1)
for pc := uint64(0); pc < uint64(len(code)); pc++ {
// bitvec is a bit vector which maps bytes in a program.
// An unset bit means the byte is an opcode, a set bit means
// it's data (i.e. argument of PUSHxx).
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))
}
// 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
}
// codeBitmap collects data locations in code.
func codeBitmap(code []byte) bitvec {
// The bitmap is 4 bytes longer than necessary, in case the code
// ends with a PUSH32, the algorithm will push zeroes onto the
// bitvector outside the bounds of the actual code.
bits := make(bitvec, len(code)/8+1+4)
for pc := uint64(0); pc < uint64(len(code)); {
op := OpCode(code[pc])
if op == JUMPDEST {
m[pc/8] |= 1 << (pc % 8)
} else if op >= PUSH1 && op <= PUSH32 {
a := uint64(op) - uint64(PUSH1) + 1
pc += a
if op >= PUSH1 && op <= PUSH32 {
numbits := op - PUSH1 + 1
pc++
for ; numbits >= 8; numbits -= 8 {
bits.set8(pc) // 8
pc += 8
}
for ; numbits > 0; numbits-- {
bits.set(pc)
pc++
}
} else {
pc++
}
}
return m
return bits
}

53
core/vm/analysis_test.go Normal file
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@ -0,0 +1,53 @@
// Copyright 2017 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
package vm
import "testing"
func TestJumpDestAnalysis(t *testing.T) {
tests := []struct {
code []byte
exp byte
which int
}{
{[]byte{byte(PUSH1), 0x01, 0x01, 0x01}, 0x40, 0},
{[]byte{byte(PUSH1), byte(PUSH1), byte(PUSH1), byte(PUSH1)}, 0x50, 0},
{[]byte{byte(PUSH8), byte(PUSH8), byte(PUSH8), byte(PUSH8), byte(PUSH8), byte(PUSH8), byte(PUSH8), byte(PUSH8), 0x01, 0x01, 0x01}, 0x7F, 0},
{[]byte{byte(PUSH8), 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01}, 0x80, 1},
{[]byte{0x01, 0x01, 0x01, 0x01, 0x01, byte(PUSH2), byte(PUSH2), byte(PUSH2), 0x01, 0x01, 0x01}, 0x03, 0},
{[]byte{0x01, 0x01, 0x01, 0x01, 0x01, byte(PUSH2), 0x01, 0x01, 0x01, 0x01, 0x01}, 0x00, 1},
{[]byte{byte(PUSH3), 0x01, 0x01, 0x01, byte(PUSH1), 0x01, 0x01, 0x01, 0x01, 0x01, 0x01}, 0x74, 0},
{[]byte{byte(PUSH3), 0x01, 0x01, 0x01, byte(PUSH1), 0x01, 0x01, 0x01, 0x01, 0x01, 0x01}, 0x00, 1},
{[]byte{0x01, byte(PUSH8), 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01}, 0x3F, 0},
{[]byte{0x01, byte(PUSH8), 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01}, 0xC0, 1},
{[]byte{byte(PUSH16), 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01}, 0x7F, 0},
{[]byte{byte(PUSH16), 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01}, 0xFF, 1},
{[]byte{byte(PUSH16), 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01}, 0x80, 2},
{[]byte{byte(PUSH8), 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, byte(PUSH1), 0x01}, 0x7f, 0},
{[]byte{byte(PUSH8), 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, byte(PUSH1), 0x01}, 0xA0, 1},
{[]byte{byte(PUSH32)}, 0x7F, 0},
{[]byte{byte(PUSH32)}, 0xFF, 1},
{[]byte{byte(PUSH32)}, 0xFF, 2},
}
for _, test := range tests {
ret := codeBitmap(test.code)
if ret[test.which] != test.exp {
t.Fatalf("expected %x, got %02x", test.exp, ret[test.which])
}
}
}