pkg/vcs: refactor bisection support

In preparation for syz-ci bisection:
- move bisection function into a separate interface
  they look out of place in vcs.Repo because most OSes
  don't implement it and most users don't case
- extract author name and more CC emails for commits
- move linux-specific PreviousReleaseTags into linux.go
- fix inconclusive bisection (more than 1 potential commits)
- add tests fr bisection
- add maintainers returned from get_maintainers.pl for commits
  that don't have enough emails (e.g. only author email)

Update #501

1 files changed, 154 insertions, 0 deletions

diff --git a/pkg/vcs/linux.go b/pkg/vcs/linux.go
new file mode 100644
index 000000000..f8d97d60e
--- /dev/null
+++ b/pkg/vcs/linux.go
@@ -0,0 +1,154 @@
+// Copyright 2019 syzkaller project authors. All rights reserved.
+// Use of this source code is governed by Apache 2 LICENSE that can be found in the LICENSE file.
+
+package vcs
+
+import (
+	"bytes"
+	"io"
+	"net/mail"
+	"path/filepath"
+	"sort"
+	"strconv"
+	"strings"
+	"time"
+
+	"github.com/google/syzkaller/pkg/email"
+	"github.com/google/syzkaller/pkg/osutil"
+)
+
+type linux struct {
+	*git
+}
+
+func newLinux(dir string) *linux {
+	ignoreCC := map[string]bool{
+		"stable@vger.kernel.org": true,
+	}
+	return &linux{
+		git: newGit(dir, ignoreCC),
+	}
+}
+
+func (ctx *linux) Bisect(bad, good string, trace io.Writer, pred func() (BisectResult, error)) ([]*Commit, error) {
+	commits, err := ctx.git.Bisect(bad, good, trace, pred)
+	if len(commits) == 1 {
+		ctx.addMaintainers(commits[0])
+	}
+	return commits, err
+}
+
+func (ctx *linux) addMaintainers(com *Commit) {
+	if len(com.CC) > 3 {
+		return
+	}
+	list := ctx.getMaintainers(com.Hash, false)
+	if len(list) < 3 {
+		list = ctx.getMaintainers(com.Hash, true)
+	}
+	com.CC = email.MergeEmailLists(com.CC, list)
+}
+
+func (ctx *linux) getMaintainers(hash string, blame bool) []string {
+	args := "git show " + hash + " | " +
+		filepath.FromSlash("scripts/get_maintainer.pl") + " --no-n --no-rolestats"
+	if blame {
+		args += " --git-blame"
+	}
+	output, err := osutil.RunCmd(time.Minute, ctx.git.dir, "bash", "-c", args)
+	if err != nil {
+		return nil
+	}
+	var list []string
+	for _, line := range strings.Split(string(output), "\n") {
+		addr, err := mail.ParseAddress(line)
+		if err != nil {
+			continue
+		}
+		list = append(list, strings.ToLower(addr.Address))
+	}
+	return list
+}
+
+func (ctx *linux) PreviousReleaseTags(commit string) ([]string, error) {
+	output, err := runSandboxed(ctx.dir, "git", "tag", "--no-contains", commit, "--merged", commit, "v*.*")
+	if err != nil {
+		return nil, err
+	}
+	tags, err := gitParseReleaseTags(output)
+	if err != nil {
+		return nil, err
+	}
+	for i, tag := range tags {
+		if tag == "v3.8" {
+			// v3.8 does not work with modern perl, and as we go further in history
+			// make stops to work, then binutils, glibc, etc. So we stop at v3.8.
+			// Up to that point we only need an ancient gcc.
+			tags = tags[:i]
+			break
+		}
+	}
+	return tags, nil
+}
+
+func gitParseReleaseTags(output []byte) ([]string, error) {
+	var tags []string
+	for _, tag := range bytes.Split(output, []byte{'\n'}) {
+		if releaseTagRe.Match(tag) && gitReleaseTagToInt(string(tag)) != 0 {
+			tags = append(tags, string(tag))
+		}
+	}
+	sort.Slice(tags, func(i, j int) bool {
+		return gitReleaseTagToInt(tags[i]) > gitReleaseTagToInt(tags[j])
+	})
+	return tags, nil
+}
+
+func gitReleaseTagToInt(tag string) uint64 {
+	matches := releaseTagRe.FindStringSubmatchIndex(tag)
+	v1, err := strconv.ParseUint(tag[matches[2]:matches[3]], 10, 64)
+	if err != nil {
+		return 0
+	}
+	v2, err := strconv.ParseUint(tag[matches[4]:matches[5]], 10, 64)
+	if err != nil {
+		return 0
+	}
+	var v3 uint64
+	if matches[6] != -1 {
+		v3, err = strconv.ParseUint(tag[matches[6]:matches[7]], 10, 64)
+		if err != nil {
+			return 0
+		}
+	}
+	return v1*1e6 + v2*1e3 + v3
+}
+
+func (ctx *linux) EnvForCommit(commit string, kernelConfig []byte) (*BisectEnv, error) {
+	tagList, err := ctx.PreviousReleaseTags(commit)
+	if err != nil {
+		return nil, err
+	}
+	tags := make(map[string]bool)
+	for _, tag := range tagList {
+		tags[tag] = true
+	}
+	env := &BisectEnv{
+		Compiler:     "gcc-" + linuxCompilerVersion(tags),
+		KernelConfig: kernelConfig,
+	}
+	return env, nil
+}
+
+func linuxCompilerVersion(tags map[string]bool) string {
+	switch {
+	case tags["v4.12"]:
+		return "8.1.0"
+	case tags["v4.11"]:
+		return "7.3.0"
+	case tags["v3.19"]:
+		return "5.5.0"
+	default:
+		return "4.9.4"
+	}
+}