tools/syz-testbed: support per-checkout syz-manager configs

Let the user of the tool specify individual syz-manager configs for
checkouts. A base config is specified as previously and then individual
parts of jsons are applied to that base config, e.g.

<...>
  "checkouts": [
    {
      "name": "first",
      "repo": "https://github.com/google/syzkaller.git",
    },
    {
      "name": "second",
      "repo": "https://github.com/google/syzkaller.git",
      "manager_config": {
        "kernel_obj": "/tmp/linux-stable2"
      }
    }
  ],
  "manager_config": {
	  "target": "linux/amd64",
	  "kernel_obj": "/tmp/linux-stable",
          <...>
  }
<...>

5 files changed, 140 insertions, 25 deletions

diff --git a/pkg/config/merge.go b/pkg/config/merge.go
new file mode 100644
index 000000000..49a7254de
--- /dev/null
+++ b/pkg/config/merge.go
@@ -0,0 +1,57 @@
+// Copyright 2021 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 config
+
+import (
+	"encoding/json"
+)
+
+// Unfortunately, if we want to apply a JSON patch to some configuration, we cannot just unmarshal
+// it twice - in that case json.RawMessage objects will be completely replaced, but not merged.
+func MergeJSONData(left, right []byte) ([]byte, error) {
+	vLeft, err := parseFragment(left)
+	if err != nil {
+		return nil, err
+	}
+	vRight, err := parseFragment(right)
+	if err != nil {
+		return nil, err
+	}
+	merged := mergeRecursive(vLeft, vRight)
+	return json.Marshal(merged)
+}
+
+func parseFragment(input []byte) (parsed interface{}, err error) {
+	if len(input) == 0 {
+		// For convenience, we allow empty strings to be passed to the function that merges JSONs.
+		return
+	}
+	err = json.Unmarshal(json.RawMessage(input), &parsed)
+	return
+}
+
+// If one of the elements is not a map, use the new one.
+// Otherwise, recursively merge map elements.
+func mergeRecursive(left, right interface{}) interface{} {
+	if left == nil {
+		return right
+	}
+	if right == nil {
+		return left
+	}
+	mLeft, okLeft := left.(map[string]interface{})
+	mRight, okRight := right.(map[string]interface{})
+	if !okLeft || !okRight {
+		return right
+	}
+	for key, val := range mRight {
+		valLeft, ok := mLeft[key]
+		if ok {
+			mLeft[key] = mergeRecursive(valLeft, val)
+		} else {
+			mLeft[key] = val
+		}
+	}
+	return mLeft
+}
diff --git a/pkg/config/merge_test.go b/pkg/config/merge_test.go
new file mode 100644
index 000000000..c5a45754e
--- /dev/null
+++ b/pkg/config/merge_test.go
@@ -0,0 +1,49 @@
+// Copyright 2021 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 config_test
+
+import (
+	"bytes"
+	"testing"
+
+	"github.com/google/syzkaller/pkg/config"
+)
+
+func TestMergeJSONData(t *testing.T) {
+	tests := []struct {
+		left   string
+		right  string
+		result string
+	}{
+		{
+			`{"a":1,"b":2}`,
+			`{"b":3,"c":4}`,
+			`{"a":1,"b":3,"c":4}`,
+		},
+		{
+			`{"a":1,"b":{"c":{"d":"nested string","e":"another string"}}}`,
+			`{"b":{"c":{"d":12345}}}`,
+			`{"a":1,"b":{"c":{"d":12345,"e":"another string"}}}`,
+		},
+		{
+			`{}`,
+			`{"a":{"b":{"c":0}}}`,
+			`{"a":{"b":{"c":0}}}`,
+		},
+		{
+			`{"a":{"b":{"c":0}}}`,
+			``,
+			`{"a":{"b":{"c":0}}}`,
+		},
+	}
+	for _, test := range tests {
+		res, err := config.MergeJSONData([]byte(test.left), []byte(test.right))
+		if err != nil {
+			t.Errorf("unexpected error: %s", err)
+		}
+		if !bytes.Equal(res, []byte(test.result)) {
+			t.Errorf("expected %s, got %s", test.result, res)
+		}
+	}
+}
diff --git a/tools/syz-testbed/checkout.go b/tools/syz-testbed/checkout.go
index fe846bbb2..91508ff99 100644
--- a/tools/syz-testbed/checkout.go
+++ b/tools/syz-testbed/checkout.go
@@ -10,15 +10,17 @@ import (
 	"time"
 
 	syz_instance "github.com/google/syzkaller/pkg/instance"
+	"github.com/google/syzkaller/pkg/mgrconfig"
 	"github.com/google/syzkaller/pkg/osutil"
 	"github.com/google/syzkaller/pkg/vcs"
 )
 
 type Checkout struct {
-	Path      string
-	Name      string
-	Running   []*Instance
-	Completed []*RunResult
+	Path          string
+	Name          string
+	ManagerConfig *mgrconfig.Config
+	Running       []*Instance
+	Completed     []*RunResult
 }
 
 func (checkout *Checkout) ArchiveRunning() error {
@@ -33,10 +35,11 @@ func (checkout *Checkout) ArchiveRunning() error {
 	return nil
 }
 
-func (ctx *TestbedContext) NewCheckout(config *CheckoutConfig) (*Checkout, error) {
+func (ctx *TestbedContext) NewCheckout(config *CheckoutConfig, mgrConfig *mgrconfig.Config) (*Checkout, error) {
 	checkout := &Checkout{
-		Name: config.Name,
-		Path: filepath.Join(ctx.Config.Workdir, "checkouts", config.Name),
+		Name:          config.Name,
+		Path:          filepath.Join(ctx.Config.Workdir, "checkouts", config.Name),
+		ManagerConfig: mgrConfig,
 	}
 	log.Printf("[%s] Checking out", checkout.Name)
 	if osutil.IsExist(checkout.Path) {
diff --git a/tools/syz-testbed/instance.go b/tools/syz-testbed/instance.go
index c51b9c597..f7293d289 100644
--- a/tools/syz-testbed/instance.go
+++ b/tools/syz-testbed/instance.go
@@ -108,7 +108,7 @@ func (ctx *TestbedContext) NewInstance(checkout *Checkout, mgrName string) (*Ins
 	}
 
 	log.Printf("[%s] Generating syz-manager config", name)
-	managerCfg := *ctx.ManagerConfig
+	managerCfg := *checkout.ManagerConfig
 	managerCfg.Name = mgrName
 	managerCfg.Workdir = workdir
 	managerCfg.Syzkaller = checkout.Path
diff --git a/tools/syz-testbed/testbed.go b/tools/syz-testbed/testbed.go
index e67dd6883..dee9ffc73 100644
--- a/tools/syz-testbed/testbed.go
+++ b/tools/syz-testbed/testbed.go
@@ -46,14 +46,14 @@ type DurationConfig struct {
 }
 
 type CheckoutConfig struct {
-	Name   string `json:"name"`
-	Repo   string `json:"repo"`
-	Branch string `json:"branch"`
+	Name          string          `json:"name"`
+	Repo          string          `json:"repo"`
+	Branch        string          `json:"branch"`
+	ManagerConfig json.RawMessage `json:"manager_config"` // a patch to manager config
 }
 
 type TestbedContext struct {
 	Config         *TestbedConfig
-	ManagerConfig  *mgrconfig.Config
 	Checkouts      []*Checkout
 	NextRestart    time.Time
 	NextCheckoutID int
@@ -76,24 +76,14 @@ func main() {
 	if err != nil {
 		tool.Failf("invalid config: %s", err)
 	}
-
-	managerCfg, err := mgrconfig.LoadPartialData(cfg.ManagerConfig)
-	if err != nil {
-		tool.Failf("failed to parse manager config: %s", err)
-	}
-	if managerCfg.HTTP == "" {
-		// Actually we don't care much about the specific ports of syz-managers.
-		managerCfg.HTTP = ":0"
-	}
-
 	ctx := TestbedContext{
-		Config:        cfg,
-		ManagerConfig: managerCfg,
+		Config: cfg,
 	}
 	go ctx.setupHTTPServer()
 
 	for _, checkoutCfg := range cfg.Checkouts {
-		co, err := ctx.NewCheckout(&checkoutCfg)
+		mgrCfg := ctx.MakeMgrConfig(cfg.ManagerConfig, checkoutCfg.ManagerConfig)
+		co, err := ctx.NewCheckout(&checkoutCfg, mgrCfg)
 		if err != nil {
 			tool.Failf("checkout failed: %s", err)
 		}
@@ -117,6 +107,22 @@ func main() {
 	ctx.Loop(shutdown)
 }
 
+func (ctx *TestbedContext) MakeMgrConfig(base, patch json.RawMessage) *mgrconfig.Config {
+	mergedConfig, err := config.MergeJSONData(base, patch)
+	if err != nil {
+		tool.Failf("failed to apply a patch to the base manager config: %s", err)
+	}
+	mgrCfg, err := mgrconfig.LoadPartialData(mergedConfig)
+	if err != nil {
+		tool.Failf("failed to parse base manager config: %s", err)
+	}
+	if mgrCfg.HTTP == "" {
+		// Actually, we don't care much about the specific ports of syz-managers.
+		mgrCfg.HTTP = ":0"
+	}
+	return mgrCfg
+}
+
 func (ctx *TestbedContext) GetStatViews() ([]StatView, error) {
 	groupsCompleted := []RunResultGroup{}
 	groupsAll := []RunResultGroup{}