add code to retrieve kernel command line parameters

pkg/util/metrics/system/cmdline_args.go

@@ -0,0 +1,88 @@
+/*
+Copyright 2020 The Kubernetes Authors All rights reserved.
+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 system
+
+import (
+	"encoding/json"
+	"fmt"
+	"strings"
+)
+
+var cmdlineFilePath = "/proc/cmdline"
+
+type CmdlineArg struct {
+	Key   string `json:"key"`
+	Value string `json:"value"`
+}
+
+func (d CmdlineArg) String() string {
+	s, _ := json.Marshal(d)
+	return string(s)
+}
+
+// As per the documentation kernel command line parameters can also be specified
+// within double quotes and are separated with spaces.
+// https://www.kernel.org/doc/html/v4.14/admin-guide/kernel-parameters.html#the-kernel-s-command-line-parameters
+var withinQuotes = false
+
+func splitAfterSpace(inputChar rune) bool {
+	// words with space within double quotes cannot be split.
+	// so we track the start quote and when we find the
+	// end quote, then we reiterate.
+	if inputChar == '"' {
+		withinQuotes = !withinQuotes
+		return false
+	}
+	//ignore spaces when it is within quotes.
+	if withinQuotes {
+		return false
+	}
+	return inputChar == ' '
+}
+
+// CmdlineArgs returns all the kernel cmdline. It is read from cat /proc/cmdline.
+func CmdlineArgs() ([]CmdlineArg, error) {
+	lines, err := ReadFileIntoLines(cmdlineFilePath)
+	if err != nil {
+		return nil, fmt.Errorf("error reading the file %v, %v", cmdlineFilePath, err)
+	}
+	if len(lines) < 1 {
+		return nil, fmt.Errorf("no lines are retured")
+	}
+	cmdlineArgs := strings.FieldsFunc(lines[0], splitAfterSpace)
+	var result = make([]CmdlineArg, 0, len(cmdlineArgs))
+	// for commandline only one line is returned.
+	for _, words := range cmdlineArgs {
+		// Ignore the keys that start with double quotes
+		if strings.Index(words, "\"") == 0 {
+			continue
+		}
+		splitsWords := strings.Split(words, "=")
+		if len(splitsWords) < 2 {
+			var stats = CmdlineArg{
+				Key: splitsWords[0],
+			}
+			result = append(result, stats)
+		} else {
+			//remove quotes in the values
+			trimmedValue := strings.Trim(splitsWords[1], "\"'")
+			var stats = CmdlineArg{
+				Key:   splitsWords[0],
+				Value: trimmedValue,
+			}
+			result = append(result, stats)
+		}
+	}
+	return result, nil
+}

pkg/util/metrics/system/cmdline_args_test.go

@@ -0,0 +1,101 @@
+package system
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestCmdlineStats(t *testing.T) {
+	testcases := []struct {
+		name                  string
+		fakeCmdlineFilePath   string
+		expectedCmdlineArgs   []CmdlineArg
+		unExpectedCmdlineArgs []CmdlineArg
+	}{
+		{
+			name:                "default_cos",
+			fakeCmdlineFilePath: "testdata/cmdline_args_key_cos.txt",
+			expectedCmdlineArgs: []CmdlineArg{
+				{
+					Key:   "console",
+					Value: "ttyS0",
+				},
+				{
+					Key:   "boot",
+					Value: "local",
+				},
+				{
+					Key: "cros_efi",
+				},
+			},
+			unExpectedCmdlineArgs: []CmdlineArg{
+				{
+					Key:   "hashstart",
+					Value: "4077568",
+				},
+				{
+					Key: "vroot",
+				},
+			},
+		},
+		{
+			name:                "sample",
+			fakeCmdlineFilePath: "testdata/cmdline_args_sample.txt",
+			expectedCmdlineArgs: []CmdlineArg{
+				{
+					Key:   "key1",
+					Value: "value1",
+				},
+				{
+					Key:   "key3",
+					Value: "value2 value3",
+				},
+				{
+					Key: "key2",
+				},
+			},
+			unExpectedCmdlineArgs: []CmdlineArg{
+				{
+					Key:   "value2",
+					Value: "value3",
+				},
+				{
+					Key: "value3",
+				},
+			},
+		},
+	}
+	for _, test := range testcases {
+		t.Run(test.name, func(t *testing.T) {
+			originalCmdlineFilePath := cmdlineFilePath
+			defer func() {
+				cmdlineFilePath = originalCmdlineFilePath
+			}()
+
+			cmdlineFilePath = test.fakeCmdlineFilePath
+			cmdlineArgs, err := CmdlineArgs()
+			if err != nil {
+				t.Errorf("Unexpected error retrieving cmdlineArgs: %v\nCmdlineArgsFilePath: %s\n", err, cmdlineFilePath)
+			}
+			for _, expectedCmdlineArg := range test.expectedCmdlineArgs {
+				assert.Contains(t, cmdlineArgs, expectedCmdlineArg, "Failed to find cmdlineArgs: %v\n", expectedCmdlineArg)
+			}
+			for _, unExpectedCmdlineArg := range test.unExpectedCmdlineArgs {
+				assert.NotContains(t, cmdlineArgs, unExpectedCmdlineArg, "Unpected expected cmdlinearg found: %v\n", unExpectedCmdlineArg)
+			}
+		})
+	}
+}
+
+func TestCmdlineStats_String(t *testing.T) {
+	v := CmdlineArg{
+		Key:   "test",
+		Value: "test",
+	}
+	e := `{"key":"test","value":"test"}`
+	assert.Equal(t,
+		e, fmt.Sprintf("%v", v), "CmdlineArg string is invalid: %v", v)
+
+}

pkg/util/metrics/system/common.go

@@ -18,7 +18,7 @@ import (
 	"os"
 )
 
-// ReadFile reads contents from a file and returns lines.
+// ReadFileIntoLines reads contents from a file and returns lines.
 func ReadFileIntoLines(filename string) ([]string, error) {
 	file, err := os.Open(filename)
 	if err != nil {

pkg/util/metrics/system/testdata/cmdline_args_key_cos.txt

@@ -0,0 +1 @@
+BOOT_IMAGE=/syslinux/vmlinuz.A init=/usr/lib/systemd/systemd boot=local rootwait ro noresume noswap loglevel=7 noinitrd console=ttyS0 virtio_net.napi_tx=1 systemd.unified_cgroup_hierarchy=false systemd.legacy_systemd_cgroup_controller=false csm.disabled=1 loadpin.exclude=kernel-module modules-load=loadpin_trigger module.sig_enforce=1 dm_verity.error_behavior=3 dm_verity.max_bios=-1 dm_verity.dev_wait=1 i915.modeset=1 cros_efi "dm=1 vroot none ro 1,0 verity hashstart=4077568"

pkg/util/metrics/system/testdata/cmdline_args_sample.txt

@@ -0,0 +1 @@
+key1=value1 key2 key3="value2 value3"