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author | Martin Holst Swende <martin@swende.se> | 2017-08-14 16:57:54 +0800 |
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committer | Martin Holst Swende <martin@swende.se> | 2017-08-14 16:57:54 +0800 |
commit | 967e097faa51850a01053624cc74f300edf9770b (patch) | |
tree | 6756c3cfebd11f899b9a7d3b0fd6049afe5578d4 /core/vm/analysis.go | |
parent | f4b5f67ee07dabc25b5baab0a94f3420606fd0ea (diff) | |
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core/vm: Address review concerns
Diffstat (limited to 'core/vm/analysis.go')
-rw-r--r-- | core/vm/analysis.go | 33 |
1 files changed, 19 insertions, 14 deletions
diff --git a/core/vm/analysis.go b/core/vm/analysis.go index b27dee8dc..3ff862695 100644 --- a/core/vm/analysis.go +++ b/core/vm/analysis.go @@ -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) addone(pos uint64) { - bits.m[pos/8] |= 0x80 >> (pos % 8) +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) 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 } |