runtime: add geust memory dump

When guest panic, dump guest kernel memory to host filesystem.
And also includes:
- hypervisor config
- hypervisor version
- and state of sandbox

Fixes: #1012

Signed-off-by: bin liu <bin@hyper.sh>

src/runtime/pkg/utils/utils_test.go

@@ -6,7 +6,10 @@
 package utils
 
 import (
+	"fmt"
+	"io/ioutil"
 	"net/http"
+	"os"
 	"testing"
 
 	"github.com/stretchr/testify/assert"
@@ -45,3 +48,71 @@ func TestGzipAccepted(t *testing.T) {
 		assert.Equal(tc.result, b)
 	}
 }
+
+func TestEnsureDir(t *testing.T) {
+	const testMode = 0755
+	tmpdir, err := ioutil.TempDir("", "TestEnsureDir")
+	assert := assert.New(t)
+
+	assert.NoError(err)
+	defer os.RemoveAll(tmpdir)
+
+	testCases := []struct {
+		before func()
+		path   string
+		err    bool
+		msg    string
+	}{
+		{
+			before: nil,
+			path:   "a/b/c",
+			err:    true,
+			msg:    "Not an absolute path",
+		},
+		{
+			before: nil,
+			path:   fmt.Sprintf("%s/abc/def", tmpdir),
+			err:    false,
+			msg:    "",
+		},
+		{
+			before: nil,
+			path:   fmt.Sprintf("%s/abc", tmpdir),
+			err:    false,
+			msg:    "",
+		},
+		{
+			before: func() {
+				err := os.MkdirAll(fmt.Sprintf("%s/abc/def", tmpdir), testMode)
+				assert.NoError(err)
+			},
+			path: fmt.Sprintf("%s/abc/def", tmpdir),
+			err:  false,
+			msg:  "",
+		},
+		{
+			before: func() {
+				// create a regular file
+				err := os.MkdirAll(fmt.Sprintf("%s/abc", tmpdir), testMode)
+				assert.NoError(err)
+				_, err = os.Create(fmt.Sprintf("%s/abc/file.txt", tmpdir))
+				assert.NoError(err)
+			},
+			path: fmt.Sprintf("%s/abc/file.txt", tmpdir),
+			err:  true,
+			msg:  "Not a directory",
+		},
+	}
+
+	for _, tc := range testCases {
+		if tc.before != nil {
+			tc.before()
+		}
+		err := EnsureDir(tc.path, testMode)
+		if tc.err {
+			assert.Contains(err.Error(), tc.msg, "error msg should contains: %s, but got %s", tc.msg, err.Error())
+		} else {
+			assert.Equal(err, nil, "failed for path: %s, except no error, but got %+v", tc.path, err)
+		}
+	}
+}