pkg/codesearch: add skeleton for code searching tool

Add a clang tool that is used for code indexing (tools/clang/codesearch/).
It follows conventions and build procedure of the declextract tool.

Add pkg/codesearch package that aggregates the info exposed by the clang tools,
and allows doing simple queries:
 - show source code of an entity (function, struct, etc)
 - show entity comment
 - show all entities defined in a source file

Add tools/syz-codesearch wrapper tool that allows to create index for a kernel build,
and then run code queries on it.

1 files changed, 61 insertions, 0 deletions

diff --git a/pkg/codesearch/codesearch_test.go b/pkg/codesearch/codesearch_test.go
new file mode 100644
index 000000000..7af509294
--- /dev/null
+++ b/pkg/codesearch/codesearch_test.go
@@ -0,0 +1,61 @@
+// Copyright 2025 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 codesearch
+
+import (
+	"bytes"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+
+	"github.com/google/syzkaller/pkg/clangtool/tooltest"
+	"github.com/google/syzkaller/pkg/osutil"
+)
+
+func TestClangTool(t *testing.T) {
+	tooltest.TestClangTool[Database](t)
+}
+
+func TestCommands(t *testing.T) {
+	db := tooltest.LoadOutput[Database](t)
+	index := &Index{db, []string{"testdata"}}
+	files, err := filepath.Glob(filepath.Join(osutil.Abs("testdata"), "query*"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(files) == 0 {
+		t.Fatal("found no qeury files")
+	}
+	covered := make(map[string]bool)
+	for _, file := range files {
+		t.Run(filepath.Base(file), func(t *testing.T) {
+			testCommand(t, index, covered, file)
+		})
+	}
+	for _, cmd := range Commands {
+		if !covered[cmd.Name] {
+			t.Errorf("command %v is not covered, add at least one test", cmd.Name)
+		}
+	}
+}
+
+func testCommand(t *testing.T, index *Index, covered map[string]bool, file string) {
+	data, err := os.ReadFile(file)
+	if err != nil {
+		t.Fatal(err)
+	}
+	query, _, _ := bytes.Cut(data, []byte{'\n'})
+	args := strings.Fields(string(query))
+	if len(args) == 0 {
+		t.Fatal("no command found")
+	}
+	result, err := index.Command(args[0], args[1:])
+	if err != nil {
+		t.Fatal(err)
+	}
+	got := append([]byte(strings.Join(args, " ")+"\n\n"), result...)
+	tooltest.CompareGoldenData(t, file, got)
+	covered[args[0]] = true
+}