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// Copyright 2019 The Prometheus Authors
// 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 procfs
import (
"bufio"
"fmt"
"io"
"os"
"strconv"
"strings"
)
var validOptionalFields = map[string]bool{
"shared": true,
"master": true,
"propagate_from": true,
"unbindable": true,
}
// A MountInfo is a type that describes the details, options
// for each mount, parsed from /proc/self/mountinfo.
// The fields described in each entry of /proc/self/mountinfo
// is described in the following man page.
// http://man7.org/linux/man-pages/man5/proc.5.html
type MountInfo struct {
// Unique Id for the mount
MountId int
// The Id of the parent mount
ParentId int
// The value of `st_dev` for the files on this FS
MajorMinorVer string
// The pathname of the directory in the FS that forms
// the root for this mount
Root string
// The pathname of the mount point relative to the root
MountPoint string
// Mount options
Options map[string]string
// Zero or more optional fields
OptionalFields map[string]string
// The Filesystem type
FSType string
// FS specific information or "none"
Source string
// Superblock options
SuperOptions map[string]string
}
// Returns part of the mountinfo line, if it exists, else an empty string.
func getStringSliceElement(parts []string, idx int, defaultValue string) string {
if idx >= len(parts) {
return defaultValue
}
return parts[idx]
}
// Reads each line of the mountinfo file, and returns a list of formatted MountInfo structs.
func parseMountInfo(r io.Reader) ([]*MountInfo, error) {
mounts := []*MountInfo{}
scanner := bufio.NewScanner(r)
for scanner.Scan() {
mountString := scanner.Text()
parsedMounts, err := parseMountInfoString(mountString)
if err != nil {
return nil, err
}
mounts = append(mounts, parsedMounts)
}
err := scanner.Err()
return mounts, err
}
// Parses a mountinfo file line, and converts it to a MountInfo struct.
// An important check here is to see if the hyphen separator, as if it does not exist,
// it means that the line is malformed.
func parseMountInfoString(mountString string) (*MountInfo, error) {
var err error
// OptionalFields can be zero, hence these checks to ensure we do not populate the wrong values in the wrong spots
separatorIndex := strings.Index(mountString, "-")
if separatorIndex == -1 {
return nil, fmt.Errorf("no separator found in mountinfo string: %s", mountString)
}
beforeFields := strings.Fields(mountString[:separatorIndex])
afterFields := strings.Fields(mountString[separatorIndex+1:])
if (len(beforeFields) + len(afterFields)) < 7 {
return nil, fmt.Errorf("too few fields")
}
mount := &MountInfo{
MajorMinorVer: getStringSliceElement(beforeFields, 2, ""),
Root: getStringSliceElement(beforeFields, 3, ""),
MountPoint: getStringSliceElement(beforeFields, 4, ""),
Options: mountOptionsParser(getStringSliceElement(beforeFields, 5, "")),
OptionalFields: nil,
FSType: getStringSliceElement(afterFields, 0, ""),
Source: getStringSliceElement(afterFields, 1, ""),
SuperOptions: mountOptionsParser(getStringSliceElement(afterFields, 2, "")),
}
mount.MountId, err = strconv.Atoi(getStringSliceElement(beforeFields, 0, ""))
if err != nil {
return nil, fmt.Errorf("failed to parse mount ID")
}
mount.ParentId, err = strconv.Atoi(getStringSliceElement(beforeFields, 1, ""))
if err != nil {
return nil, fmt.Errorf("failed to parse parent ID")
}
// Has optional fields, which is a space separated list of values.
// Example: shared:2 master:7
if len(beforeFields) > 6 {
mount.OptionalFields = make(map[string]string)
optionalFields := beforeFields[6:]
for _, field := range optionalFields {
optionSplit := strings.Split(field, ":")
target, value := optionSplit[0], ""
if len(optionSplit) == 2 {
value = optionSplit[1]
}
// Checks if the 'keys' in the optional fields in the mountinfo line are acceptable.
// Allowed 'keys' are shared, master, propagate_from, unbindable.
if _, ok := validOptionalFields[target]; ok {
mount.OptionalFields[target] = value
}
}
}
return mount, nil
}
// Parses the mount options, superblock options.
func mountOptionsParser(mountOptions string) map[string]string {
opts := make(map[string]string)
options := strings.Split(mountOptions, ",")
for _, opt := range options {
splitOption := strings.Split(opt, "=")
if len(splitOption) < 2 {
key := splitOption[0]
opts[key] = ""
} else {
key, value := splitOption[0], splitOption[1]
opts[key] = value
}
}
return opts
}
// Retrieves mountinfo information from `/proc/self/mountinfo`.
func GetMounts() ([]*MountInfo, error) {
f, err := os.Open("/proc/self/mountinfo")
if err != nil {
return nil, err
}
defer f.Close()
return parseMountInfo(f)
}
// Retrieves mountinfo information from a processes' `/proc/<pid>/mountinfo`.
func GetProcMounts(pid int) ([]*MountInfo, error) {
f, err := os.Open(fmt.Sprintf("/proc/%d/mountinfo", pid))
if err != nil {
return nil, err
}
defer f.Close()
return parseMountInfo(f)
}
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