prepping for walkers to be plugins

Signed-off-by: Vincent Batts <vbatts@hashbangbash.com>

main.go

@@ -21,13 +21,37 @@ var (
 		"writeBytes": writeBytesFuzz,
 		"writeNum":   writeNumFuzz,
 	}
-	fuzzTimeout = 500 * time.Millisecond
+	fuzzTimeout   = 500 * time.Millisecond
+	walkerPlugins []walker.Fuzzer
 )
 
+func appInit(c *cli.Context) error {
+	matches, err := filepath.Glob(c.String("plugins"))
+	if err != nil {
+		return err
+	}
+	for _, match := range matches {
+		ff, err := walker.LoadPlugin(match)
+		if err != nil {
+			return err
+		}
+		walkerPlugins = append(walkerPlugins, ff)
+	}
+	return nil
+}
+
 func main() {
 	app := cli.NewApp()
 	app.Name = "fuzz-walker"
 	app.Usage = "a walker to poke and prod at /proc and /sys"
+	app.Before = appInit
+	app.Flags = []cli.Flag{
+		cli.StringFlag{
+			Name:  "plugins",
+			Value: "*.so",
+			Usage: "pattern to glob walker plugins",
+		},
+	}
 	app.Action = func(c *cli.Context) error {
 		hasError := false
 		for _, dir := range dirs {

walker/func.go

@@ -1,8 +1,34 @@
 package walker
 
 import (
+	"fmt"
 	"os"
+	"plugin"
 	"time"
 )
 
+// LoadPlugin loads the file path and returns a Fuzzer
+func LoadPlugin(path string) (Fuzzer, error) {
+	p, err := plugin.Open(path)
+	if err != nil {
+		return nil, err
+	}
+	sym, err := p.Lookup("MyFuzzerFunc")
+	if err != nil {
+		return nil, err
+	}
+	mff, ok := sym.(Fuzzer)
+	if !ok {
+		return nil, fmt.Errorf("plugin at %q did not provide a FuzzFunc named MyFuzzerFunc", path)
+	}
+	return mff, nil
+}
+
+// Fuzzer is a struct that produces a FuzzFunc
+type Fuzzer interface {
+	Name() string
+	Func() FuzzFunc
+}
+
+// FuzzFunc is like filepath.WalkerFunc, but for poking at `path`
 type FuzzFunc func(path string, info os.FileInfo, timeout time.Duration) error