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// Copyright 2018-2019 psgo 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 proc
import (
"bufio"
"fmt"
"os"
"path/filepath"
"strconv"
"strings"
"github.com/containers/psgo/internal/cgroups"
)
// GetPIDs extracts and returns all PIDs from /proc.
func GetPIDs() ([]string, error) {
procDir, err := os.Open("/proc/")
if err != nil {
return nil, err
}
defer procDir.Close()
// extract string slice of all directories in procDir
pidDirs, err := procDir.Readdirnames(0)
if err != nil {
return nil, err
}
pids := []string{}
for _, pidDir := range pidDirs {
_, err := strconv.Atoi(pidDir)
if err != nil {
// skip non-numerical entries (e.g., `/proc/softirqs`)
continue
}
pids = append(pids, pidDir)
}
return pids, nil
}
// GetPIDsFromCgroup returns a strings slice of all pids listed in pid's pids
// cgroup. It automatically detects if we're running in unified mode or not.
func GetPIDsFromCgroup(pid string) ([]string, error) {
unified, err := cgroups.IsCgroup2UnifiedMode()
if err != nil {
return nil, err
}
if unified {
return getPIDsFromCgroupV2(pid)
}
return getPIDsFromCgroupV1(pid)
}
// getPIDsFromCgroupV1 returns a strings slice of all pids listed in pid's pids
// cgroup.
func getPIDsFromCgroupV1(pid string) ([]string, error) {
// First, find the corresponding path to the PID cgroup.
pidPath := fmt.Sprintf("/proc/%s/cgroup", pid)
f, err := os.Open(pidPath)
if err != nil {
return nil, err
}
defer f.Close()
scanner := bufio.NewScanner(f)
cgroupPath := ""
for scanner.Scan() {
fields := strings.Split(scanner.Text(), ":")
if len(fields) != 3 {
continue
}
if fields[1] == "pids" {
cgroupPath = filepath.Join(cgroups.CgroupRoot, "pids", fields[2], "cgroup.procs")
break
}
}
if cgroupPath == "" {
return nil, fmt.Errorf("couldn't find v1 pids group for PID %s", pid)
}
// Second, extract the PIDs inside the cgroup.
f, err = os.Open(cgroupPath)
if err != nil {
if os.IsNotExist(err) {
// OCI runtimes might mount the container cgroup at the root, breaking what it showed
// in /proc/$PID/cgroup and the path.
// Check if the PID still exists to make sure the process is still alive.
if _, errStat := os.Stat(pidPath); errStat == nil {
cgroupPath = filepath.Join(cgroups.CgroupRoot, "pids", "cgroup.procs")
f, err = os.Open(cgroupPath)
}
}
if err != nil {
return nil, err
}
}
defer f.Close()
pids := []string{}
scanner = bufio.NewScanner(f)
for scanner.Scan() {
pids = append(pids, scanner.Text())
}
return pids, nil
}
// getPIDsFromCgroupV2 returns a strings slice of all pids listed in pid's pids
// cgroup.
func getPIDsFromCgroupV2(pid string) ([]string, error) {
// First, find the corresponding path to the PID cgroup.
f, err := os.Open(fmt.Sprintf("/proc/%s/cgroup", pid))
if err != nil {
return nil, err
}
defer f.Close()
scanner := bufio.NewScanner(f)
cgroupSlice := ""
for scanner.Scan() {
fields := strings.Split(scanner.Text(), ":")
if len(fields) != 3 {
continue
}
if fields[1] == "" {
cgroupSlice = fields[2]
break
}
}
if cgroupSlice == "" {
return nil, fmt.Errorf("couldn't find v2 pids group for PID %s", pid)
}
// Second, extract the PIDs inside the cgroup.
f, err = os.Open(filepath.Join(cgroups.CgroupRoot, cgroupSlice, "cgroup.procs"))
if err != nil {
return nil, err
}
defer f.Close()
pids := []string{}
scanner = bufio.NewScanner(f)
for scanner.Scan() {
pids = append(pids, scanner.Text())
}
return pids, nil
}
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