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core/vm: improved jumpdest analysis

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This commit is contained in:
Martin Holst Swende 2017-06-03 19:01:22 +02:00
parent 6171d01b11
commit f4b5f67ee0
2 changed files with 72 additions and 9 deletions
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44
core/vm/analysis.go
View File

@ -41,21 +41,47 @@ func (d destinations) has(codehash common.Hash, code []byte, dest *big.Int) bool
m = jumpdests(code) m = jumpdests(code)
d[codehash] = m d[codehash] = m
} }
return (m[udest/8] & (1 << (udest % 8))) != 0 return OpCode(code[udest]) == JUMPDEST && (m[udest/8]&(0x80>>(udest%8))) == 0
// return (m[udest/8] & (1 << (udest % 8))) != 0
}
type bitvec struct {
m []byte
}
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))
} }
// jumpdests creates a map that contains an entry for each // jumpdests creates a map that contains an entry for each
// PC location that is a JUMPDEST instruction. // PC location that is a JUMPDEST instruction.
func jumpdests(code []byte) []byte { func jumpdests(code []byte) []byte {
m := make([]byte, len(code)/8+1) //The map is 4 bytes longer than necessary, in case the code
for pc := uint64(0); pc < uint64(len(code)); pc++ { // 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}
for pc := uint64(0); pc < uint64(len(code)); {
op := OpCode(code[pc]) op := OpCode(code[pc])
if op == JUMPDEST {
m[pc/8] |= 1 << (pc % 8) if op >= PUSH1 && op <= PUSH32 {
} else if op >= PUSH1 && op <= PUSH32 { numbits := op - PUSH1 + 1
a := uint64(op) - uint64(PUSH1) + 1 pc++
pc += a for ; numbits >= 8; numbits -= 8 {
bits.addOneByte(pc) // 8
pc += 8
}
for ; numbits > 0; numbits-- {
bits.addone(pc)
pc++
}
} else {
pc++
} }
} }
return m return bits.m
} }

37
core/vm/analysis_test.go Normal file
View File

@ -0,0 +1,37 @@
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 := jumpdests(test.code)
if ret[test.which] != test.exp {
t.Fatalf("expected %x, got %02x", test.exp, ret[test.which])
}
}
}