package mountinfo
import (
"bufio"
"fmt"
"io"
"os"
"runtime"
"strconv"
"strings"
"sync"
"golang.org/x/sys/unix"
)
// GetMountsFromReader retrieves a list of mounts from the
// reader provided, with an optional filter applied (use nil
// for no filter). This can be useful in tests or benchmarks
// that provide fake mountinfo data, or when a source other
// than /proc/thread-self/mountinfo needs to be read from.
//
// This function is Linux-specific.
func GetMountsFromReader(r io.Reader, filter FilterFunc) ([]*Info, error) {
s := bufio.NewScanner(r)
out := []*Info{}
for s.Scan() {
var err error
/*
See http://man7.org/linux/man-pages/man5/proc.5.html
36 35 98:0 /mnt1 /mnt2 rw,noatime master:1 - ext3 /dev/root rw,errors=continue
(1)(2)(3) (4) (5) (6) (7) (8) (9) (10) (11)
(1) mount ID: unique identifier of the mount (may be reused after umount)
(2) parent ID: ID of parent (or of self for the top of the mount tree)
(3) major:minor: value of st_dev for files on filesystem
(4) root: root of the mount within the filesystem
(5) mount point: mount point relative to the process's root
(6) mount options: per mount options
(7) optional fields: zero or more fields of the form "tag[:value]"
(8) separator: marks the end of the optional fields
(9) filesystem type: name of filesystem of the form "type[.subtype]"
(10) mount source: filesystem specific information or "none"
(11) super options: per super block options
In other words, we have:
* 6 mandatory fields (1)..(6)
* 0 or more optional fields (7)
* a separator field (8)
* 3 mandatory fields (9)..(11)
*/
text := s.Text()
fields := strings.Split(text, " ")
numFields := len(fields)
if numFields < 10 {
// should be at least 10 fields
return nil, fmt.Errorf("parsing '%s' failed: not enough fields (%d)", text, numFields)
}
// separator field
sepIdx := numFields - 4
// In Linux <= 3.9 mounting a cifs with spaces in a share
// name (like "//srv/My Docs") _may_ end up having a space
// in the last field of mountinfo (like "unc=//serv/My Docs").
// Since kernel 3.10-rc1, cifs option "unc=" is ignored,
// so spaces should not appear.
//
// Check for a separator, and work around the spaces bug
for fields[sepIdx] != "-" {
sepIdx--
if sepIdx == 5 {
return nil, fmt.Errorf("parsing '%s' failed: missing - separator", text)
}
}
p := &Info{}
p.Mountpoint, err = unescape(fields[4])
if err != nil {
return nil, fmt.Errorf("parsing '%s' failed: mount point: %w", fields[4], err)
}
p.FSType, err = unescape(fields[sepIdx+1])
if err != nil {
return nil, fmt.Errorf("parsing '%s' failed: fstype: %w", fields[sepIdx+1], err)
}
p.Source, err = unescape(fields[sepIdx+2])
if err != nil {
return nil, fmt.Errorf("parsing '%s' failed: source: %w", fields[sepIdx+2], err)
}
p.VFSOptions = fields[sepIdx+3]
// ignore any numbers parsing errors, as there should not be any
p.ID, _ = strconv.Atoi(fields[0])
p.Parent, _ = strconv.Atoi(fields[1])
mm := strings.SplitN(fields[2], ":", 3)
if len(mm) != 2 {
return nil, fmt.Errorf("parsing '%s' failed: unexpected major:minor pair %s", text, mm)
}
p.Major, _ = strconv.Atoi(mm[0])
p.Minor, _ = strconv.Atoi(mm[1])
p.Root, err = unescape(fields[3])
if err != nil {
return nil, fmt.Errorf("parsing '%s' failed: root: %w", fields[3], err)
}
p.Options = fields[5]
// zero or more optional fields
p.Optional = strings.Join(fields[6:sepIdx], " ")
// Run the filter after parsing all fields.
var skip, stop bool
if filter != nil {
skip, stop = filter(p)
if skip {
continue
}
}
out = append(out, p)
if stop {
break
}
}
if err := s.Err(); err != nil {
return nil, err
}
return out, nil
}
var (
haveProcThreadSelf bool
haveProcThreadSelfOnce sync.Once
)
func parseMountTable(filter FilterFunc) (_ []*Info, err error) {
haveProcThreadSelfOnce.Do(func() {
_, err := os.Stat("/proc/thread-self/mountinfo")
haveProcThreadSelf = err == nil
})
// We need to lock ourselves to the current OS thread in order to make sure
// that the thread referenced by /proc/thread-self stays alive until we
// finish parsing the file.
runtime.LockOSThread()
defer runtime.UnlockOSThread()
var f *os.File
if haveProcThreadSelf {
f, err = os.Open("/proc/thread-self/mountinfo")
} else {
// On pre-3.17 kernels (such as CentOS 7), we don't have
// /proc/thread-self/ so we need to manually construct
// /proc/self/task/<tid>/ as a fallback.
f, err = os.Open("/proc/self/task/" + strconv.Itoa(unix.Gettid()) + "/mountinfo")
if os.IsNotExist(err) {
// If /proc/self/task/... failed, it means that our active pid
// namespace doesn't match the pid namespace of the /proc mount. In
// this case we just have to make do with /proc/self, since there
// is no other way of figuring out our tid in a parent pid
// namespace on pre-3.17 kernels.
f, err = os.Open("/proc/self/mountinfo")
}
}
if err != nil {
return nil, err
}
defer f.Close()
return GetMountsFromReader(f, filter)
}
// PidMountInfo retrieves the list of mounts from a given process' mount
// namespace. Unless there is a need to get mounts from a mount namespace
// different from that of a calling process, use GetMounts.
//
// This function is Linux-specific.
//
// Deprecated: this will be removed before v1; use GetMountsFromReader with
// opened /proc/<pid>/mountinfo as an argument instead.
func PidMountInfo(pid int) ([]*Info, error) {
f, err := os.Open(fmt.Sprintf("/proc/%d/mountinfo", pid))
if err != nil {
return nil, err
}
defer f.Close()
return GetMountsFromReader(f, nil)
}
// A few specific characters in mountinfo path entries (root and mountpoint)
// are escaped using a backslash followed by a character's ascii code in octal.
//
// space -- as \040
// tab (aka \t) -- as \011
// newline (aka \n) -- as \012
// backslash (aka \\) -- as \134
//
// This function converts path from mountinfo back, i.e. it unescapes the above sequences.
func unescape(path string) (string, error) {
// try to avoid copying
if strings.IndexByte(path, '\\') == -1 {
return path, nil
}
// The following code is UTF-8 transparent as it only looks for some
// specific characters (backslash and 0..7) with values < utf8.RuneSelf,
// and everything else is passed through as is.
buf := make([]byte, len(path))
bufLen := 0
for i := 0; i < len(path); i++ {
if path[i] != '\\' {
buf[bufLen] = path[i]
bufLen++
continue
}
s := path[i:]
if len(s) < 4 {
// too short
return "", fmt.Errorf("bad escape sequence %q: too short", s)
}
c := s[1]
switch c {
case '0', '1', '2', '3', '4', '5', '6', '7':
v := c - '0'
for j := 2; j < 4; j++ { // one digit already; two more
if s[j] < '0' || s[j] > '7' {
return "", fmt.Errorf("bad escape sequence %q: not a digit", s[:3])
}
x := s[j] - '0'
v = (v << 3) | x
}
if v > 255 {
return "", fmt.Errorf("bad escape sequence %q: out of range" + s[:3])
}
buf[bufLen] = v
bufLen++
i += 3
continue
default:
return "", fmt.Errorf("bad escape sequence %q: not a digit" + s[:3])
}
}
return string(buf[:bufLen]), nil
}
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