sentry: capture CPU usage metadata for save.

PiperOrigin-RevId: 195466647
Change-Id: Ib5ca815f7b64a4881441e58567adedf344b206f1

pkg/sentry/state/BUILD

@@ -7,10 +7,12 @@ go_library(
     srcs = [
         "state.go",
         "state_metadata.go",
+        "state_unsafe.go",
     ],
     importpath = "gvisor.googlesource.com/gvisor/pkg/sentry/state",
     visibility = ["//pkg/sentry:internal"],
     deps = [
+        "//pkg/abi/linux",
         "//pkg/log",
         "//pkg/sentry/inet",
         "//pkg/sentry/kernel",

pkg/sentry/state/state.go

@@ -27,6 +27,8 @@ import (
 	"gvisor.googlesource.com/gvisor/pkg/state/statefile"
 )
 
+var previousMetadata map[string]string
+
 // ErrStateFile is returned when the state file cannot be opened.
 type ErrStateFile struct {
 	err error
@@ -103,11 +105,13 @@ type LoadOpts struct {
 // Load loads the given kernel, setting the provided platform and stack.
 func (opts LoadOpts) Load(k *kernel.Kernel, p platform.Platform, n inet.Stack) error {
 	// Open the file.
-	r, _, err := statefile.NewReader(opts.Source, opts.Key)
+	r, m, err := statefile.NewReader(opts.Source, opts.Key)
 	if err != nil {
 		return ErrStateFile{err}
 	}
 
+	previousMetadata = m
+
 	// Restore the Kernel object graph.
 	return k.LoadFrom(r, p, n)
 }

pkg/sentry/state/state_metadata.go

@@ -17,13 +17,29 @@ package state
 import (
 	"fmt"
 	"time"
+
+	"gvisor.googlesource.com/gvisor/pkg/log"
 )
 
 // The save metadata keys for timestamp.
 const (
+	cpuUsage          = "cpu_usage"
 	metadataTimestamp = "timestamp"
 )
 
 func addSaveMetadata(m map[string]string) {
+	t, err := cpuTime()
+	if err != nil {
+		log.Warningf("Error getting cpu time: %v", err)
+	}
+	if previousMetadata != nil {
+		p, err := time.ParseDuration(previousMetadata[cpuUsage])
+		if err != nil {
+			log.Warningf("Error parsing previous runs' cpu time: %v", err)
+		}
+		t += p
+	}
+	m[cpuUsage] = t.String()
+
 	m[metadataTimestamp] = fmt.Sprintf("%v", time.Now())
 }

pkg/sentry/state/state_unsafe.go

@@ -0,0 +1,33 @@
+// Copyright 2018 Google Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package state
+
+import (
+	"fmt"
+	"syscall"
+	"time"
+	"unsafe"
+
+	"gvisor.googlesource.com/gvisor/pkg/abi/linux"
+)
+
+func cpuTime() (time.Duration, error) {
+	var ts syscall.Timespec
+	_, _, errno := syscall.RawSyscall(syscall.SYS_CLOCK_GETTIME, uintptr(linux.CLOCK_PROCESS_CPUTIME_ID), uintptr(unsafe.Pointer(&ts)), 0)
+	if errno != 0 {
+		return 0, fmt.Errorf("failed calling clock_gettime(CLOCK_PROCESS_CPUTIME_ID): errno=%d", errno)
+	}
+	return time.Duration(ts.Nano()), nil
+}