108 lines
2.5 KiB
Go
108 lines
2.5 KiB
Go
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// Copyright 2021 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package fuzz
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import (
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"fmt"
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"math/bits"
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)
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// ResetCovereage sets all of the counters for each edge of the instrumented
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// source code to 0.
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func ResetCoverage() {
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cov := coverage()
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for i := range cov {
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cov[i] = 0
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}
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}
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// SnapshotCoverage copies the current counter values into coverageSnapshot,
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// preserving them for later inspection. SnapshotCoverage also rounds each
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// counter down to the nearest power of two. This lets the coordinator store
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// multiple values for each counter by OR'ing them together.
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func SnapshotCoverage() {
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cov := coverage()
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for i, b := range cov {
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b |= b >> 1
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b |= b >> 2
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b |= b >> 4
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b -= b >> 1
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coverageSnapshot[i] = b
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}
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}
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// diffCoverage returns a set of bits set in snapshot but not in base.
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// If there are no new bits set, diffCoverage returns nil.
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func diffCoverage(base, snapshot []byte) []byte {
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if len(base) != len(snapshot) {
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panic(fmt.Sprintf("the number of coverage bits changed: before=%d, after=%d", len(base), len(snapshot)))
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}
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found := false
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for i := range snapshot {
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if snapshot[i]&^base[i] != 0 {
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found = true
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break
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}
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}
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if !found {
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return nil
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}
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diff := make([]byte, len(snapshot))
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for i := range diff {
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diff[i] = snapshot[i] &^ base[i]
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}
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return diff
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}
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// countNewCoverageBits returns the number of bits set in snapshot that are not
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// set in base.
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func countNewCoverageBits(base, snapshot []byte) int {
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n := 0
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for i := range snapshot {
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n += bits.OnesCount8(snapshot[i] &^ base[i])
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}
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return n
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}
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// isCoverageSubset returns true if all the base coverage bits are set in
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// snapshot
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func isCoverageSubset(base, snapshot []byte) bool {
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for i, v := range base {
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if v&snapshot[i] != v {
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return false
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}
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}
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return true
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}
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// hasCoverageBit returns true if snapshot has at least one bit set that is
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// also set in base.
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func hasCoverageBit(base, snapshot []byte) bool {
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for i := range snapshot {
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if snapshot[i]&base[i] != 0 {
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return true
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}
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}
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return false
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}
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func countBits(cov []byte) int {
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n := 0
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for _, c := range cov {
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n += bits.OnesCount8(c)
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}
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return n
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}
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var (
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coverageEnabled = len(coverage()) > 0
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coverageSnapshot = make([]byte, len(coverage()))
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// _counters and _ecounters mark the start and end, respectively, of where
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// the 8-bit coverage counters reside in memory. They're known to cmd/link,
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// which specially assigns their addresses for this purpose.
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_counters, _ecounters [0]byte
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)
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