Merge pull request #14582 from holiman/jumpdest_improv
core/vm: improve jumpdest analysis
This commit is contained in:
commit
bce5d837b5
@ -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
53
core/vm/analysis_test.go
Normal file
@ -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])
|
||||
}
|
||||
}
|
||||
|
||||
}
|
Loading…
Reference in New Issue
Block a user