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package main
import (
"context"
"encoding/hex"
"errors"
"flag"
"fmt"
"os"
"strconv"
"strings"
"time"
"github.com/godbus/dbus/v5"
"golang.org/x/sys/unix"
"swproof/busdial"
)
type Record struct {
PID int
StartTicks uint64
Unit string
InvocationID string
}
func startTicks(pid int) (uint64, error) {
raw, err := os.ReadFile(fmt.Sprintf("/proc/%d/stat", pid))
if err != nil {
return 0, err
}
s := string(raw)
i := strings.LastIndexByte(s, ')')
f := strings.Fields(s[i+2:])
return strconv.ParseUint(f[19], 10, 64)
}
func call(ctx context.Context, c *dbus.Conn, method string, args ...any) *dbus.Call {
return c.Object("org.freedesktop.systemd1", "/org/freedesktop/systemd1").CallWithContext(ctx, "org.freedesktop.systemd1.Manager."+method, 0, args...)
}
func unitInvocation(ctx context.Context, c *dbus.Conn, path dbus.ObjectPath) (string, string, error) {
o := c.Object("org.freedesktop.systemd1", path)
var id, inv dbus.Variant
if err := o.CallWithContext(ctx, "org.freedesktop.DBus.Properties.Get", 0, "org.freedesktop.systemd1.Unit", "Id").Store(&id); err != nil {
return "", "", err
}
if err := o.CallWithContext(ctx, "org.freedesktop.DBus.Properties.Get", 0, "org.freedesktop.systemd1.Unit", "InvocationID").Store(&inv); err != nil {
return "", "", err
}
return id.Value().(string), hex.EncodeToString(inv.Value().([]byte)), nil
}
func classifyBusErr(err error) string {
var de dbus.Error
if errors.As(err, &de) {
switch de.Name {
case "org.freedesktop.systemd1.NoUnitForPID", "org.freedesktop.systemd1.NoSuchUnit", "org.freedesktop.systemd1.NoSuchProcess":
return "Lost(" + de.Name + ")"
}
return "Unknown(dbus " + de.Name + ")"
}
return "Unknown(transport: " + err.Error() + ")"
}
func main() {
mode := flag.String("mode", "private", "session|private")
busPath := flag.String("bus", "", "override socket path")
pid := flag.Int("pid", 0, "pid")
unit := flag.String("unit", "", "expected unit")
inv := flag.String("inv", "", "expected invocation id")
ticks := flag.Uint64("ticks", 0, "expected start ticks (0 = learn)")
hold := flag.Duration("hold", 0, "hold pidfd open, then recheck after this delay")
flag.Parse()
fmt.Printf("ident pid=%d expect unit=%s inv=%s ticks=%d\n", *pid, *unit, *inv, *ticks)
pfd, err := unix.PidfdOpen(*pid, 0)
if err != nil {
fmt.Printf("pidfd_open: %v -> verdict Lost(process gone)\n", err)
os.Exit(0)
}
fmt.Printf("pidfd_open ok fd=%d\n", pfd)
st, err := startTicks(*pid)
fmt.Printf("stat starttime(field22)=%v err=%v\n", st, err)
if err := unix.PidfdSendSignal(pfd, 0, nil, 0); err != nil {
fmt.Printf("pidfd_send_signal(0) after stat read: %v -> verdict Lost\n", err)
os.Exit(0)
}
if *ticks != 0 && st != *ticks {
fmt.Printf("start ticks mismatch %d != %d -> verdict Lost(pid reused)\n", st, *ticks)
os.Exit(0)
}
check := func(label string) {
ctx, cancel := context.WithTimeout(context.Background(), 2*time.Second)
defer cancel()
t0 := time.Now()
c, err := busdial.Raw(ctx, *mode, *busPath)
if err != nil {
fmt.Printf("[%s] bus connect (%s %s): %v after %s -> verdict %s\n", label, *mode, *busPath, err, time.Since(t0), classifyBusErr(err))
return
}
defer c.Close()
fmt.Printf("[%s] bus connected (%s) unixfd=%v\n", label, *mode, c.SupportsUnixFDs())
var p dbus.ObjectPath
var name string
var invb []byte
err = call(ctx, c, "GetUnitByPIDFD", dbus.UnixFD(pfd)).Store(&p, &name, &invb)
if err != nil {
fmt.Printf("[%s] GetUnitByPIDFD: %v -> %s\n", label, err, classifyBusErr(err))
} else {
fmt.Printf("[%s] GetUnitByPIDFD: path=%s unit=%s invocation=%s\n", label, p, name, hex.EncodeToString(invb))
}
var p2 dbus.ObjectPath
err = call(ctx, c, "GetUnitByPID", uint32(*pid)).Store(&p2)
if err != nil {
fmt.Printf("[%s] GetUnitByPID(%d): %v -> %s\n", label, *pid, err, classifyBusErr(err))
} else {
id, iv, err := unitInvocation(ctx, c, p2)
fmt.Printf("[%s] GetUnitByPID(%d): path=%s Id=%s InvocationID=%s err=%v\n", label, *pid, p2, id, iv, err)
}
if *unit != "" {
var p3 dbus.ObjectPath
if err := call(ctx, c, "GetUnit", *unit).Store(&p3); err != nil {
fmt.Printf("[%s] GetUnit(%s): %v -> %s\n", label, *unit, err, classifyBusErr(err))
} else {
id, iv, _ := unitInvocation(ctx, c, p3)
var mp dbus.Variant
_ = c.Object("org.freedesktop.systemd1", p3).CallWithContext(ctx, "org.freedesktop.DBus.Properties.Get", 0, "org.freedesktop.systemd1.Service", "MainPID").Store(&mp)
fmt.Printf("[%s] GetUnit(%s): Id=%s InvocationID=%s MainPID=%v\n", label, *unit, id, iv, mp.Value())
}
}
if *inv != "" {
if err == nil && name == *unit && hex.EncodeToString(invb) == *inv {
fmt.Printf("[%s] verdict Alive(same unit+invocation, pidfd-pinned)\n", label)
}
}
}
check("t0")
if *hold > 0 {
fmt.Printf("holding pidfd %s ...\n", *hold)
time.Sleep(*hold)
fds := []unix.PollFd{{Fd: int32(pfd), Events: unix.POLLIN}}
n, _ := unix.Poll(fds, 0)
fmt.Printf("poll(pidfd) readable=%v (readable == process exited)\n", n == 1)
err := unix.PidfdSendSignal(pfd, 0, nil, 0)
fmt.Printf("pidfd_send_signal(0) on held fd: %v\n", err)
st2, err2 := startTicks(*pid)
fmt.Printf("/proc/%d/stat now: ticks=%v err=%v\n", *pid, st2, err2)
check("t1")
}
}
