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authorMartin Holst Swende <martin@swende.se>2017-08-14 16:57:54 +0800
committerMartin Holst Swende <martin@swende.se>2017-08-14 16:57:54 +0800
commit967e097faa51850a01053624cc74f300edf9770b (patch)
tree6756c3cfebd11f899b9a7d3b0fd6049afe5578d4 /core/vm
parentf4b5f67ee07dabc25b5baab0a94f3420606fd0ea (diff)
downloaddexon-967e097faa51850a01053624cc74f300edf9770b.tar.gz
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core/vm: Address review concerns
Diffstat (limited to 'core/vm')
-rw-r--r--core/vm/analysis.go33
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
}