vm: add workdir_template functionality

The new manager config argument workdir_template refers to a directory. Optional.
Each VM will get a recursive copy of the files that are present in workdir_template.
VM config can then use these private copies as needed. The copy directory
can be referenced with "{{TEMPLATE}}" string. This is different from using
the files directly in that each instance will get own clean, private,
scratch copy of the files. Currently supported only for qemu_args argument
of qemu VM type. Use example:
Create a template dir with necessary files:
$ mkdir /mytemplatedir
$ truncate -s 64K /mytemplatedir/fd
Then specify the dir in the manager config:
	"workdir_template": "/mytemplatedir"
Then use these files in VM config:
	"qemu_args": "-fda {{TEMPLATE}}/fd"

5 files changed, 69 insertions, 7 deletions

diff --git a/pkg/mgrconfig/config.go b/pkg/mgrconfig/config.go
index 07df5d0c7..69df2a801 100644
--- a/pkg/mgrconfig/config.go
+++ b/pkg/mgrconfig/config.go
@@ -19,6 +19,21 @@ type Config struct {
 	// - <workdir>/corpus.db: corpus with interesting programs
 	// - <workdir>/instance-x: per VM instance temporary files
 	Workdir string `json:"workdir"`
+	// Refers to a directory. Optional.
+	// Each VM will get a recursive copy of the files that are present in workdir_template.
+	// VM config can then use these private copies as needed. The copy directory
+	// can be referenced with "{{TEMPLATE}}" string. This is different from using
+	// the files directly in that each instance will get own clean, private,
+	// scratch copy of the files. Currently supported only for qemu_args argument
+	// of qemu VM type. Use example:
+	// Create a template dir with necessary files:
+	// $ mkdir /mytemplatedir
+	// $ truncate -s 64K /mytemplatedir/fd
+	// Then specify the dir in the manager config:
+	//	"workdir_template": "/mytemplatedir"
+	// Then use these files in VM config:
+	//	"qemu_args": "-fda {{TEMPLATE}}/fd"
+	WorkdirTemplate string `json:"workdir_template"`
 	// Directory with kernel object files (e.g. `vmlinux` for linux)
 	// (used for report symbolization and coverage reports, optional).
 	KernelObj string `json:"kernel_obj"`
diff --git a/pkg/mgrconfig/load.go b/pkg/mgrconfig/load.go
index 0733a9c2a..4e4136362 100644
--- a/pkg/mgrconfig/load.go
+++ b/pkg/mgrconfig/load.go
@@ -5,6 +5,7 @@ package mgrconfig
 
 import (
 	"fmt"
+	"io/ioutil"
 	"os"
 	"path/filepath"
 	"strings"
@@ -82,6 +83,12 @@ func Complete(cfg *Config) error {
 		return fmt.Errorf("config param workdir is empty")
 	}
 	cfg.Workdir = osutil.Abs(cfg.Workdir)
+	if cfg.WorkdirTemplate != "" {
+		cfg.WorkdirTemplate = osutil.Abs(cfg.WorkdirTemplate)
+		if _, err := ioutil.ReadDir(cfg.WorkdirTemplate); err != nil {
+			return fmt.Errorf("failed to read workdir_template: %v", err)
+		}
+	}
 	if cfg.Syzkaller == "" {
 		return fmt.Errorf("config param syzkaller is empty")
 	}
diff --git a/pkg/osutil/osutil.go b/pkg/osutil/osutil.go
index 32a8054e7..0bc257e76 100644
--- a/pkg/osutil/osutil.go
+++ b/pkg/osutil/osutil.go
@@ -163,6 +163,30 @@ func CopyFiles(srcDir, dstDir string, files map[string]bool) error {
 	return os.Rename(tmpDir, dstDir)
 }
 
+func CopyDirRecursively(srcDir, dstDir string) error {
+	if err := MkdirAll(dstDir); err != nil {
+		return err
+	}
+	files, err := ioutil.ReadDir(srcDir)
+	if err != nil {
+		return err
+	}
+	for _, file := range files {
+		src := filepath.Join(srcDir, file.Name())
+		dst := filepath.Join(dstDir, file.Name())
+		if file.IsDir() {
+			if err := CopyDirRecursively(src, dst); err != nil {
+				return err
+			}
+			continue
+		}
+		if err := CopyFile(src, dst); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
 // LinkFiles creates hard links for files from dstDir to srcDir.
 // Files are assumed to be relative names in slash notation.
 // All other files in dstDir are removed.
diff --git a/vm/qemu/qemu.go b/vm/qemu/qemu.go
index 44e12246b..dae8f493b 100644
--- a/vm/qemu/qemu.go
+++ b/vm/qemu/qemu.go
@@ -337,9 +337,7 @@ func (inst *instance) boot() error {
 		"-serial", "stdio",
 		"-no-reboot",
 	}
-	if inst.cfg.QemuArgs != "" {
-		args = append(args, strings.Split(inst.cfg.QemuArgs, " ")...)
-	}
+	args = append(args, splitArgs(inst.cfg.QemuArgs, filepath.Join(inst.workdir, "template"))...)
 	if inst.image == "9p" {
 		args = append(args,
 			"-fsdev", "local,id=fsdev0,path=/,security_model=none,readonly",
@@ -426,6 +424,16 @@ func (inst *instance) boot() error {
 	return nil
 }
 
+func splitArgs(str, template string) (args []string) {
+	for _, arg := range strings.Split(str, " ") {
+		if arg == "" {
+			continue
+		}
+		args = append(args, strings.Replace(arg, "{{TEMPLATE}}", template, -1))
+	}
+	return
+}
+
 func (inst *instance) Forward(port int) (string, error) {
 	addr := hostAddr
 	if inst.target.HostFuzzer {
diff --git a/vm/vm.go b/vm/vm.go
index 2e499f567..1b6e7eb2e 100644
--- a/vm/vm.go
+++ b/vm/vm.go
@@ -12,6 +12,7 @@ import (
 	"bytes"
 	"fmt"
 	"os"
+	"path/filepath"
 	"time"
 
 	"github.com/google/syzkaller/pkg/mgrconfig"
@@ -32,8 +33,9 @@ import (
 )
 
 type Pool struct {
-	impl    vmimpl.Pool
-	workdir string
+	impl     vmimpl.Pool
+	workdir  string
+	template string
 }
 
 type Instance struct {
@@ -86,8 +88,9 @@ func Create(cfg *mgrconfig.Config, debug bool) (*Pool, error) {
 		return nil, err
 	}
 	return &Pool{
-		impl:    impl,
-		workdir: env.Workdir,
+		impl:     impl,
+		workdir:  env.Workdir,
+		template: cfg.WorkdirTemplate,
 	}, nil
 }
 
@@ -103,6 +106,11 @@ func (pool *Pool) Create(index int) (*Instance, error) {
 	if err != nil {
 		return nil, fmt.Errorf("failed to create instance temp dir: %v", err)
 	}
+	if pool.template != "" {
+		if err := osutil.CopyDirRecursively(pool.template, filepath.Join(workdir, "template")); err != nil {
+			return nil, err
+		}
+	}
 	impl, err := pool.impl.Create(workdir, index)
 	if err != nil {
 		os.RemoveAll(workdir)