tools: add syz-expand

The syz-expand tools allows to parse a program and print it including all
the default values. This is mainly useful for debugging, like doing manual
program modifications while trying to come up with a reproducer for some
particular kernel behavior.

Makefile

@@ -172,6 +172,9 @@ trace2syz:
 usbgen:
 	GOOS=$(HOSTOS) GOARCH=$(HOSTARCH) $(HOSTGO) build $(GOHOSTFLAGS) -o ./bin/syz-usbgen github.com/google/syzkaller/tools/syz-usbgen
 
+expand:
+	GOOS=$(HOSTOS) GOARCH=$(HOSTARCH) $(HOSTGO) build $(GOHOSTFLAGS) -o ./bin/syz-expand github.com/google/syzkaller/tools/syz-expand
+
 # `extract` extracts const files from various kernel sources, and may only
 # re-generate parts of files.
 extract: bin/syz-extract

prog/encoding.go

@@ -25,11 +25,20 @@ func (p *Prog) String() string {
 }
 
 func (p *Prog) Serialize() []byte {
+	return p.serialize(false)
+}
+
+func (p *Prog) SerializeVerbose() []byte {
+	return p.serialize(true)
+}
+
+func (p *Prog) serialize(verbose bool) []byte {
 	p.debugValidate()
 	ctx := &serializer{
-		target: p.Target,
-		buf:    new(bytes.Buffer),
-		vars:   make(map[*ResultArg]int),
+		target:  p.Target,
+		buf:     new(bytes.Buffer),
+		vars:    make(map[*ResultArg]int),
+		verbose: verbose,
 	}
 	for _, c := range p.Calls {
 		ctx.call(c)
@@ -38,10 +47,11 @@ func (p *Prog) Serialize() []byte {
 }
 
 type serializer struct {
-	target *Target
-	buf    *bytes.Buffer
-	vars   map[*ResultArg]int
-	varSeq int
+	target  *Target
+	buf     *bytes.Buffer
+	vars    map[*ResultArg]int
+	varSeq  int
+	verbose bool
 }
 
 func (ctx *serializer) printf(text string, args ...interface{}) {
@@ -91,7 +101,7 @@ func (a *PointerArg) serialize(ctx *serializer) {
 	}
 	target := ctx.target
 	ctx.printf("&%v", target.serializeAddr(a))
-	if a.Res != nil && isDefault(a.Res) && !target.isAnyPtr(a.Type()) {
+	if a.Res != nil && !ctx.verbose && isDefault(a.Res) && !target.isAnyPtr(a.Type()) {
 		return
 	}
 	ctx.printf("=")
@@ -136,7 +146,7 @@ func (a *GroupArg) serialize(ctx *serializer) {
 	}
 	ctx.buf.WriteByte(delims[0])
 	lastNonDefault := len(a.Inner) - 1
-	if a.fixedInnerSize() {
+	if !ctx.verbose && a.fixedInnerSize() {
 		for ; lastNonDefault >= 0; lastNonDefault-- {
 			if !isDefault(a.Inner[lastNonDefault]) {
 				break
@@ -158,7 +168,7 @@ func (a *GroupArg) serialize(ctx *serializer) {
 
 func (a *UnionArg) serialize(ctx *serializer) {
 	ctx.printf("@%v", a.Option.Type().FieldName())
-	if isDefault(a.Option) {
+	if !ctx.verbose && isDefault(a.Option) {
 		return
 	}
 	ctx.printf("=")

prog/prog_test.go

@@ -46,19 +46,31 @@ func TestDefaultCallArgs(t *testing.T) {
 	}
 }
 
-func TestSerialize(t *testing.T) {
+func testSerialize(t *testing.T, verbose bool) {
 	target, rs, iters := initTest(t)
 	for i := 0; i < iters; i++ {
 		p := target.Generate(rs, 10, nil)
-		data := p.Serialize()
-		p1, err := target.Deserialize(data, NonStrict)
+		var data []byte
+		mode := NonStrict
+		if verbose {
+			data = p.SerializeVerbose()
+			mode = Strict
+		} else {
+			data = p.Serialize()
+		}
+		p1, err := target.Deserialize(data, mode)
 		if err != nil {
 			t.Fatalf("failed to deserialize program: %v\n%s", err, data)
 		}
 		if p1 == nil {
 			t.Fatalf("deserialized nil program:\n%s", data)
 		}
-		data1 := p1.Serialize()
+		var data1 []byte
+		if verbose {
+			data1 = p1.SerializeVerbose()
+		} else {
+			data1 = p1.Serialize()
+		}
 		if len(p.Calls) != len(p1.Calls) {
 			t.Fatalf("different number of calls")
 		}
@@ -68,6 +80,14 @@ func TestSerialize(t *testing.T) {
 	}
 }
 
+func TestSerialize(t *testing.T) {
+	testSerialize(t, false)
+}
+
+func TestSerializeVerbose(t *testing.T) {
+	testSerialize(t, true)
+}
+
 func TestVmaType(t *testing.T) {
 	target, rs, iters := initRandomTargetTest(t, "test", "64")
 	meta := target.SyscallMap["test$vma0"]

tools/syz-expand/expand.go

@@ -0,0 +1,52 @@
+// 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.
+
+// Parses a program and prints it including all default values.
+
+package main
+
+import (
+	"flag"
+	"fmt"
+	"io/ioutil"
+	"os"
+	"runtime"
+
+	"github.com/google/syzkaller/prog"
+	_ "github.com/google/syzkaller/sys"
+)
+
+var (
+	flagOS     = flag.String("os", runtime.GOOS, "target os")
+	flagArch   = flag.String("arch", runtime.GOARCH, "target arch")
+	flagProg   = flag.String("prog", "", "file with program to expand")
+	flagStrict = flag.Bool("strict", false, "parse input program in strict mode")
+)
+
+func main() {
+	flag.Parse()
+	if *flagProg == "" {
+		flag.Usage()
+		os.Exit(1)
+	}
+	target, err := prog.GetTarget(*flagOS, *flagArch)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "%v", err)
+		os.Exit(1)
+	}
+	data, err := ioutil.ReadFile(*flagProg)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "failed to read prog file: %v\n", err)
+		os.Exit(1)
+	}
+	mode := prog.NonStrict
+	if *flagStrict {
+		mode = prog.Strict
+	}
+	p, err := target.Deserialize(data, mode)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "failed to deserialize the program: %v\n", err)
+		os.Exit(1)
+	}
+	fmt.Printf("%s", p.SerializeVerbose())
+}