pkg/kconfig: add .config parsing

Update #2171

1 files changed, 153 insertions, 0 deletions

diff --git a/pkg/kconfig/config.go b/pkg/kconfig/config.go
new file mode 100644
index 000000000..70bdb1b17
--- /dev/null
+++ b/pkg/kconfig/config.go
@@ -0,0 +1,153 @@
+// Copyright 2020 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 kconfig
+
+import (
+	"bufio"
+	"bytes"
+	"fmt"
+	"io/ioutil"
+	"regexp"
+)
+
+// ConfigFile represents a parsed .config file.
+// It should not be modified directly, only by means of calling methods.
+// The only exception is Config.Value which may be modified directly.
+// Note: config names don't include CONFIG_ prefix, here and in other public interfaces,
+// users of this package should never mention CONFIG_.
+// Use Yes/Mod/No consts to check for/set config to particular values.
+type ConfigFile struct {
+	Configs  []*Config
+	Map      map[string]*Config // duplicates Configs for convenience
+	comments []string
+}
+
+type Config struct {
+	Name     string
+	Value    string
+	comments []string
+}
+
+const (
+	Yes    = "y"
+	Mod    = "m"
+	No     = "---===[[[is not set]]]===---" // to make it more obvious when some code writes it directly
+	prefix = "CONFIG_"
+)
+
+//  Value returns config value, or No if it's not present at all.
+func (cf *ConfigFile) Value(name string) string {
+	cfg := cf.Map[name]
+	if cfg == nil {
+		return No
+	}
+	return cfg.Value
+}
+
+// Set changes config value, or adds it if it's not yet present.
+func (cf *ConfigFile) Set(name, val string) {
+	cfg := cf.Map[name]
+	if cfg == nil {
+		cfg = &Config{
+			Name:  name,
+			Value: val,
+		}
+		cf.Map[name] = cfg
+		cf.Configs = append(cf.Configs, cfg)
+	}
+	cfg.Value = val
+	cfg.comments = append(cfg.comments, cf.comments...)
+	cf.comments = nil
+}
+
+// Unset sets config value to No, if it's present in the config.
+func (cf *ConfigFile) Unset(name string) {
+	cfg := cf.Map[name]
+	if cfg == nil {
+		return
+	}
+	cfg.Value = No
+}
+
+func (cf *ConfigFile) ModToYes() {
+	for _, cfg := range cf.Configs {
+		if cfg.Value == Mod {
+			cfg.Value = Yes
+		}
+	}
+}
+
+func (cf *ConfigFile) ModToNo() {
+	for _, cfg := range cf.Configs {
+		if cfg.Value == Mod {
+			cfg.Value = No
+		}
+	}
+}
+
+func (cf *ConfigFile) Serialize() []byte {
+	buf := new(bytes.Buffer)
+	for _, cfg := range cf.Configs {
+		for _, comment := range cfg.comments {
+			fmt.Fprintf(buf, "%v\n", comment)
+		}
+		if cfg.Value == No {
+			fmt.Fprintf(buf, "# %v%v is not set\n", prefix, cfg.Name)
+		} else {
+			fmt.Fprintf(buf, "%v%v=%v\n", prefix, cfg.Name, cfg.Value)
+		}
+	}
+	for _, comment := range cf.comments {
+		fmt.Fprintf(buf, "%v\n", comment)
+	}
+	return buf.Bytes()
+}
+
+func ParseConfig(file string) (*ConfigFile, error) {
+	data, err := ioutil.ReadFile(file)
+	if err != nil {
+		return nil, fmt.Errorf("failed to open .config file %v: %v", file, err)
+	}
+	return ParseConfigData(data, file)
+}
+
+func ParseConfigData(data []byte, file string) (*ConfigFile, error) {
+	cf := &ConfigFile{
+		Map: make(map[string]*Config),
+	}
+	s := bufio.NewScanner(bytes.NewReader(data))
+	for s.Scan() {
+		cf.parseLine(s.Text())
+	}
+	return cf, nil
+}
+
+func (cf *ConfigFile) clone() *ConfigFile {
+	cf1 := &ConfigFile{
+		Map:      make(map[string]*Config),
+		comments: cf.comments,
+	}
+	for _, cfg := range cf.Configs {
+		cfg1 := new(Config)
+		*cfg1 = *cfg
+		cf1.Configs = append(cf1.Configs, cfg1)
+		cf1.Map[cfg1.Name] = cfg1
+	}
+	return cf1
+}
+
+func (cf *ConfigFile) parseLine(text string) {
+	if match := reConfigY.FindStringSubmatch(text); match != nil {
+		cf.Set(match[1], match[2])
+	} else if match := reConfigN.FindStringSubmatch(text); match != nil {
+		cf.Set(match[1], No)
+	} else {
+		cf.comments = append(cf.comments, text)
+	}
+}
+
+var (
+	reConfigY = regexp.MustCompile(`^` + prefix + `([A-Za-z0-9_]+)=(y|m|(?:-?[0-9]+)|(?:0x[0-9a-fA-F]+)|(?:".*?"))$`)
+	reConfigN = regexp.MustCompile(`^# ` + prefix + `([A-Za-z0-9_]+) is not set$`)
+)