internal/helper: relocate from helper

This package is ugly and is pending removal only kept alive by xdg-dbus-proxy.

Its exported symbols are made available until v0.4.0 where it will be removed for #24.

Signed-off-by: Ophestra <cat@gensokyo.uk>

14 files changed, 136 insertions, 955 deletions

diff --git a/helper/args.go b/helper/args.go
deleted file mode 100644
index 80cd3024..00000000
--- a/helper/args.go
+++ /dev/null
@@ -1,59 +0,0 @@
-package helper
-
-import (
-	"bytes"
-	"io"
-	"syscall"
-)
-
-type argsWt [][]byte
-
-func (a argsWt) WriteTo(w io.Writer) (int64, error) {
-	nt := 0
-	for _, arg := range a {
-		n, err := w.Write(arg)
-		nt += n
-
-		if err != nil {
-			return int64(nt), err
-		}
-	}
-
-	return int64(nt), nil
-}
-
-func (a argsWt) String() string {
-	return string(
-		bytes.TrimSuffix(
-			bytes.ReplaceAll(
-				bytes.Join(a, nil),
-				[]byte{0}, []byte{' '},
-			),
-			[]byte{' '},
-		),
-	)
-}
-
-// NewCheckedArgs returns a checked null-terminated argument writer for a copy of args.
-func NewCheckedArgs(args ...string) (wt io.WriterTo, err error) {
-	a := make(argsWt, len(args))
-	for i, arg := range args {
-		a[i], err = syscall.ByteSliceFromString(arg)
-		if err != nil {
-			return
-		}
-	}
-	wt = a
-	return
-}
-
-// MustNewCheckedArgs returns a checked null-terminated argument writer for a copy of args.
-// If s contains a NUL byte this function panics instead of returning an error.
-func MustNewCheckedArgs(args ...string) io.WriterTo {
-	a, err := NewCheckedArgs(args...)
-	if err != nil {
-		panic(err.Error())
-	}
-
-	return a
-}
diff --git a/helper/args_test.go b/helper/args_test.go
deleted file mode 100644
index d6225c3e..00000000
--- a/helper/args_test.go
+++ /dev/null
@@ -1,41 +0,0 @@
-package helper_test
-
-import (
-	"errors"
-	"fmt"
-	"strings"
-	"syscall"
-	"testing"
-
-	"hakurei.app/helper"
-)
-
-func TestArgsString(t *testing.T) {
-	t.Parallel()
-	wantString := strings.Join(wantArgs, " ")
-	if got := argsWt.(fmt.Stringer).String(); got != wantString {
-		t.Errorf("String: %q, want %q", got, wantString)
-	}
-}
-
-func TestNewCheckedArgs(t *testing.T) {
-	t.Parallel()
-
-	args := []string{"\x00"}
-	if _, err := helper.NewCheckedArgs(args...); !errors.Is(err, syscall.EINVAL) {
-		t.Errorf("NewCheckedArgs: error = %v, wantErr %v", err, syscall.EINVAL)
-	}
-
-	t.Run("must panic", func(t *testing.T) {
-		t.Parallel()
-
-		badPayload := []string{"\x00"}
-		defer func() {
-			wantPanic := "invalid argument"
-			if r := recover(); r != wantPanic {
-				t.Errorf("MustNewCheckedArgs: panic = %v, wantPanic %v", r, wantPanic)
-			}
-		}()
-		helper.MustNewCheckedArgs(badPayload...)
-	})
-}
diff --git a/helper/cmd.go b/helper/cmd.go
deleted file mode 100644
index 9a5bc3ab..00000000
--- a/helper/cmd.go
+++ /dev/null
@@ -1,84 +0,0 @@
-package helper
-
-import (
-	"context"
-	"errors"
-	"io"
-	"os"
-	"os/exec"
-	"slices"
-	"sync"
-	"syscall"
-
-	"hakurei.app/helper/proc"
-)
-
-// NewDirect initialises a new direct Helper instance with wt as the null-terminated argument writer.
-// Function argF returns an array of arguments passed directly to the child process.
-func NewDirect(
-	ctx context.Context,
-	name string,
-	wt io.WriterTo,
-	stat bool,
-	argF func(argsFd, statFd int) []string,
-	cmdF func(cmd *exec.Cmd),
-	extraFiles []*os.File,
-) Helper {
-	d, args := newHelperCmd(ctx, name, wt, stat, argF, extraFiles)
-	d.Args = append(d.Args, args...)
-	if cmdF != nil {
-		cmdF(d.Cmd)
-	}
-	return d
-}
-
-func newHelperCmd(
-	ctx context.Context,
-	name string,
-	wt io.WriterTo,
-	stat bool,
-	argF func(argsFd, statFd int) []string,
-	extraFiles []*os.File,
-) (cmd *helperCmd, args []string) {
-	cmd = new(helperCmd)
-	cmd.helperFiles, args = newHelperFiles(ctx, wt, stat, argF, extraFiles)
-	cmd.Cmd = exec.CommandContext(ctx, name)
-	cmd.Cmd.Cancel = func() error { return cmd.Process.Signal(syscall.SIGTERM) }
-	cmd.WaitDelay = WaitDelay
-	return
-}
-
-// helperCmd provides a [exec.Cmd] wrapper around helper ipc.
-type helperCmd struct {
-	mu sync.RWMutex
-	*helperFiles
-	*exec.Cmd
-}
-
-func (h *helperCmd) Start() error {
-	h.mu.Lock()
-	defer h.mu.Unlock()
-
-	// Check for doubled Start calls before we defer failure cleanup. If the prior
-	// call to Start succeeded, we don't want to spuriously close its pipes.
-	if h.Cmd != nil && h.Cmd.Process != nil {
-		return errors.New("helper: already started")
-	}
-
-	h.Env = slices.Grow(h.Env, 2)
-	if h.useArgsFd {
-		h.Env = append(h.Env, HakureiHelper+"=1")
-	} else {
-		h.Env = append(h.Env, HakureiHelper+"=0")
-	}
-	if h.useStatFd {
-		h.Env = append(h.Env, HakureiStatus+"=1")
-
-		// stat is populated on fulfill
-		h.Cancel = func() error { return h.stat.Close() }
-	} else {
-		h.Env = append(h.Env, HakureiStatus+"=0")
-	}
-
-	return proc.Fulfill(h.helperFiles.ctx, &h.ExtraFiles, h.Cmd.Start, h.files, h.extraFiles)
-}
diff --git a/helper/cmd_test.go b/helper/cmd_test.go
deleted file mode 100644
index 64ac643f..00000000
--- a/helper/cmd_test.go
+++ /dev/null
@@ -1,40 +0,0 @@
-package helper_test
-
-import (
-	"context"
-	"errors"
-	"io"
-	"os"
-	"os/exec"
-	"testing"
-
-	"hakurei.app/container"
-	"hakurei.app/helper"
-)
-
-func TestCmd(t *testing.T) {
-	t.Run("start non-existent helper path", func(t *testing.T) {
-		h := helper.NewDirect(t.Context(), container.Nonexistent, argsWt, false, argF, nil, nil)
-
-		if err := h.Start(); !errors.Is(err, os.ErrNotExist) {
-			t.Errorf("Start: error = %v, wantErr %v",
-				err, os.ErrNotExist)
-		}
-	})
-
-	t.Run("valid new helper nil check", func(t *testing.T) {
-		if got := helper.NewDirect(t.Context(), "hakurei", argsWt, false, argF, nil, nil); got == nil {
-			t.Errorf("NewDirect(%q, %q) got nil",
-				argsWt, "hakurei")
-			return
-		}
-	})
-
-	t.Run("implementation compliance", func(t *testing.T) {
-		testHelper(t, func(ctx context.Context, setOutput func(stdoutP, stderrP *io.Writer), stat bool) helper.Helper {
-			return helper.NewDirect(ctx, os.Args[0], argsWt, stat, argF, func(cmd *exec.Cmd) {
-				setOutput(&cmd.Stdout, &cmd.Stderr)
-			}, nil)
-		})
-	})
-}
diff --git a/helper/container.go b/helper/container.go
deleted file mode 100644
index b85f5859..00000000
--- a/helper/container.go
+++ /dev/null
@@ -1,79 +0,0 @@
-package helper
-
-import (
-	"context"
-	"errors"
-	"io"
-	"os"
-	"os/exec"
-	"slices"
-	"sync"
-
-	"hakurei.app/container"
-	"hakurei.app/container/check"
-	"hakurei.app/helper/proc"
-	"hakurei.app/message"
-)
-
-// New initialises a Helper instance with wt as the null-terminated argument writer.
-func New(
-	ctx context.Context,
-	msg message.Msg,
-	pathname *check.Absolute, name string,
-	wt io.WriterTo,
-	stat bool,
-	argF func(argsFd, statFd int) []string,
-	cmdF func(z *container.Container),
-	extraFiles []*os.File,
-) Helper {
-	var args []string
-	h := new(helperContainer)
-	h.helperFiles, args = newHelperFiles(ctx, wt, stat, argF, extraFiles)
-	h.Container = container.NewCommand(ctx, msg, pathname, name, args...)
-	h.WaitDelay = WaitDelay
-	if cmdF != nil {
-		cmdF(h.Container)
-	}
-	return h
-}
-
-// helperContainer provides a [sandbox.Container] wrapper around helper ipc.
-type helperContainer struct {
-	started bool
-
-	mu sync.Mutex
-	*helperFiles
-	*container.Container
-}
-
-func (h *helperContainer) Start() error {
-	h.mu.Lock()
-	defer h.mu.Unlock()
-
-	if h.started {
-		return errors.New("helper: already started")
-	}
-	h.started = true
-
-	h.Env = slices.Grow(h.Env, 2)
-	if h.useArgsFd {
-		h.Env = append(h.Env, HakureiHelper+"=1")
-	} else {
-		h.Env = append(h.Env, HakureiHelper+"=0")
-	}
-	if h.useStatFd {
-		h.Env = append(h.Env, HakureiStatus+"=1")
-
-		// stat is populated on fulfill
-		h.Cancel = func(*exec.Cmd) error { return h.stat.Close() }
-	} else {
-		h.Env = append(h.Env, HakureiStatus+"=0")
-	}
-
-	return proc.Fulfill(h.helperFiles.ctx, &h.ExtraFiles, func() error {
-		if err := h.Container.Start(); err != nil {
-			return err
-		}
-		return h.Container.Serve()
-	}, h.files, h.extraFiles)
-}
diff --git a/helper/container_test.go b/helper/container_test.go
deleted file mode 100644
index 922d8253..00000000
--- a/helper/container_test.go
+++ /dev/null
@@ -1,45 +0,0 @@
-package helper_test
-
-import (
-	"context"
-	"io"
-	"os"
-	"testing"
-
-	"hakurei.app/container"
-	"hakurei.app/container/check"
-	"hakurei.app/container/fhs"
-	"hakurei.app/helper"
-)
-
-func TestContainer(t *testing.T) {
-	t.Run("start invalid container", func(t *testing.T) {
-		h := helper.New(t.Context(), nil, check.MustAbs(container.Nonexistent), "hakurei", argsWt, false, argF, nil, nil)
-
-		wantErr := "container: starting an invalid container"
-		if err := h.Start(); err == nil || err.Error() != wantErr {
-			t.Errorf("Start: error = %v, wantErr %q",
-				err, wantErr)
-		}
-	})
-
-	t.Run("valid new helper nil check", func(t *testing.T) {
-		if got := helper.New(t.Context(), nil, check.MustAbs(container.Nonexistent), "hakurei", argsWt, false, argF, nil, nil); got == nil {
-			t.Errorf("New(%q, %q) got nil",
-				argsWt, "hakurei")
-			return
-		}
-	})
-
-	t.Run("implementation compliance", func(t *testing.T) {
-		testHelper(t, func(ctx context.Context, setOutput func(stdoutP, stderrP *io.Writer), stat bool) helper.Helper {
-			return helper.New(ctx, nil, check.MustAbs(os.Args[0]), "helper", argsWt, stat, argF, func(z *container.Container) {
-				setOutput(&z.Stdout, &z.Stderr)
-				z.
-					Bind(fhs.AbsRoot, fhs.AbsRoot, 0).
-					Proc(fhs.AbsProc).
-					Dev(fhs.AbsDev, true)
-			}, nil)
-		})
-	})
-}
diff --git a/helper/deprecated.go b/helper/deprecated.go
new file mode 100644
index 00000000..f09b0c84
--- /dev/null
+++ b/helper/deprecated.go
@@ -0,0 +1,73 @@
+// Package helper exposes the internal/helper package.
+//
+// Deprecated: This package will be removed in 0.4.
+package helper
+
+import (
+	"context"
+	"io"
+	"os"
+	"os/exec"
+	"time"
+	_ "unsafe" // for go:linkname
+
+	"hakurei.app/container"
+	"hakurei.app/container/check"
+	"hakurei.app/internal/helper"
+	"hakurei.app/message"
+)
+
+//go:linkname WaitDelay hakurei.app/internal/helper.WaitDelay
+var WaitDelay time.Duration
+
+const (
+	// HakureiHelper is set to 1 when args fd is enabled and 0 otherwise.
+	HakureiHelper = helper.HakureiHelper
+	// HakureiStatus is set to 1 when stat fd is enabled and 0 otherwise.
+	HakureiStatus = helper.HakureiStatus
+)
+
+type Helper = helper.Helper
+
+// NewCheckedArgs returns a checked null-terminated argument writer for a copy of args.
+//
+//go:linkname NewCheckedArgs hakurei.app/internal/helper.NewCheckedArgs
+func NewCheckedArgs(args ...string) (wt io.WriterTo, err error)
+
+// MustNewCheckedArgs returns a checked null-terminated argument writer for a copy of args.
+// If s contains a NUL byte this function panics instead of returning an error.
+//
+//go:linkname MustNewCheckedArgs hakurei.app/internal/helper.MustNewCheckedArgs
+func MustNewCheckedArgs(args ...string) io.WriterTo
+
+// NewDirect initialises a new direct Helper instance with wt as the null-terminated argument writer.
+// Function argF returns an array of arguments passed directly to the child process.
+//
+//go:linkname NewDirect hakurei.app/internal/helper.NewDirect
+func NewDirect(
+	ctx context.Context,
+	name string,
+	wt io.WriterTo,
+	stat bool,
+	argF func(argsFd, statFd int) []string,
+	cmdF func(cmd *exec.Cmd),
+	extraFiles []*os.File,
+) Helper
+
+// New initialises a Helper instance with wt as the null-terminated argument writer.
+//
+//go:linkname New hakurei.app/internal/helper.New
+func New(
+	ctx context.Context,
+	msg message.Msg,
+	pathname *check.Absolute, name string,
+	wt io.WriterTo,
+	stat bool,
+	argF func(argsFd, statFd int) []string,
+	cmdF func(z *container.Container),
+	extraFiles []*os.File,
+) Helper
+
+// InternalHelperStub is an internal function but exported because it is cross-package;
+// it is part of the implementation of the helper stub.
+func InternalHelperStub() { helper.InternalHelperStub() }
diff --git a/helper/helper.go b/helper/helper.go
deleted file mode 100644
index 60bd7615..00000000
--- a/helper/helper.go
+++ /dev/null
@@ -1,83 +0,0 @@
-// Package helper runs external helpers with optional sandboxing.
-package helper
-
-import (
-	"context"
-	"fmt"
-	"io"
-	"os"
-	"time"
-
-	"hakurei.app/helper/proc"
-)
-
-var WaitDelay = 2 * time.Second
-
-const (
-	// HakureiHelper is set to 1 when args fd is enabled and 0 otherwise.
-	HakureiHelper = "HAKUREI_HELPER"
-	// HakureiStatus is set to 1 when stat fd is enabled and 0 otherwise.
-	HakureiStatus = "HAKUREI_STATUS"
-)
-
-type Helper interface {
-	// Start starts the helper process.
-	Start() error
-	// Wait blocks until Helper exits.
-	Wait() error
-
-	fmt.Stringer
-}
-
-func newHelperFiles(
-	ctx context.Context,
-	wt io.WriterTo,
-	stat bool,
-	argF func(argsFd, statFd int) []string,
-	extraFiles []*os.File,
-) (hl *helperFiles, args []string) {
-	hl = new(helperFiles)
-	hl.ctx = ctx
-	hl.useArgsFd = wt != nil
-	hl.useStatFd = stat
-
-	hl.extraFiles = new(proc.ExtraFilesPre)
-	for _, f := range extraFiles {
-		_, v := hl.extraFiles.Append()
-		*v = f
-	}
-
-	argsFd := -1
-	if hl.useArgsFd {
-		f := proc.NewWriterTo(wt)
-		argsFd = int(proc.InitFile(f, hl.extraFiles))
-		hl.files = append(hl.files, f)
-	}
-
-	statFd := -1
-	if hl.useStatFd {
-		f := proc.NewStat(&hl.stat)
-		statFd = int(proc.InitFile(f, hl.extraFiles))
-		hl.files = append(hl.files, f)
-	}
-
-	args = argF(argsFd, statFd)
-	return
-}
-
-// helperFiles provides a generic wrapper around helper ipc.
-type helperFiles struct {
-	// whether argsFd is present
-	useArgsFd bool
-	// whether statFd is present
-	useStatFd bool
-
-	// closes statFd
-	stat io.Closer
-	// deferred extraFiles fulfillment
-	files []proc.File
-	// passed through to [proc.Fulfill] and [proc.InitFile]
-	extraFiles *proc.ExtraFilesPre
-
-	ctx context.Context
-}
diff --git a/helper/helper_test.go b/helper/helper_test.go
deleted file mode 100644
index 4cc36d34..00000000
--- a/helper/helper_test.go
+++ /dev/null
@@ -1,139 +0,0 @@
-package helper_test
-
-import (
-	"context"
-	"errors"
-	"fmt"
-	"io"
-	"os"
-	"reflect"
-	"strconv"
-	"strings"
-	"syscall"
-	"testing"
-	"time"
-
-	"hakurei.app/helper"
-)
-
-var (
-	wantArgs = []string{
-		"unix:path=/run/dbus/system_bus_socket",
-		"/tmp/hakurei.1971/12622d846cc3fe7b4c10359d01f0eb47/system_bus_socket",
-		"--filter",
-		"--talk=org.bluez",
-		"--talk=org.freedesktop.Avahi",
-		"--talk=org.freedesktop.UPower",
-	}
-
-	wantPayload = strings.Join(wantArgs, "\x00") + "\x00"
-	argsWt      = helper.MustNewCheckedArgs(wantArgs...)
-)
-
-func argF(argsFd, statFd int) []string {
-	if argsFd == -1 {
-		panic("invalid args fd")
-	}
-
-	return argFChecked(argsFd, statFd)
-}
-
-func argFChecked(argsFd, statFd int) (args []string) {
-	args = make([]string, 0, 6)
-	if argsFd > -1 {
-		args = append(args, "--args", strconv.Itoa(argsFd))
-	}
-	if statFd > -1 {
-		args = append(args, "--fd", strconv.Itoa(statFd))
-	}
-	return
-}
-
-const (
-	containerTimeout = 30 * time.Second
-)
-
-// this function tests an implementation of the helper.Helper interface
-func testHelper(t *testing.T, createHelper func(ctx context.Context, setOutput func(stdoutP, stderrP *io.Writer), stat bool) helper.Helper) {
-	oldWaitDelay := helper.WaitDelay
-	helper.WaitDelay = 16 * time.Second
-	t.Cleanup(func() { helper.WaitDelay = oldWaitDelay })
-
-	t.Run("start helper with status channel and wait", func(t *testing.T) {
-		ctx, cancel := context.WithTimeout(t.Context(), containerTimeout)
-		stdout := new(strings.Builder)
-		h := createHelper(ctx, func(stdoutP, stderrP *io.Writer) { *stdoutP, *stderrP = stdout, os.Stderr }, true)
-
-		t.Run("wait not yet started helper", func(t *testing.T) {
-			if err := h.Wait(); !reflect.DeepEqual(err, syscall.EINVAL) &&
-				!reflect.DeepEqual(err, errors.New("exec: not started")) {
-				t.Errorf("Wait: error = %v", err)
-			}
-		})
-
-		t.Log("starting helper stub")
-		if err := h.Start(); err != nil {
-			t.Errorf("Start: error = %v", err)
-			cancel()
-			return
-		}
-		t.Log("cancelling context")
-		cancel()
-
-		t.Run("start already started helper", func(t *testing.T) {
-			wantErr := "helper: already started"
-			if err := h.Start(); err != nil && err.Error() != wantErr {
-				t.Errorf("Start: error = %v, wantErr %v",
-					err, wantErr)
-				return
-			}
-		})
-
-		t.Log("waiting on helper")
-		if err := h.Wait(); !errors.Is(err, context.Canceled) {
-			t.Errorf("Wait: error = %v",
-				err)
-		}
-
-		t.Run("wait already finalised helper", func(t *testing.T) {
-			wantErr := "exec: Wait was already called"
-			if err := h.Wait(); err != nil && err.Error() != wantErr {
-				t.Errorf("Wait: error = %v, wantErr %v",
-					err, wantErr)
-				return
-			}
-		})
-
-		if got := trimStdout(stdout); got != wantPayload {
-			t.Errorf("Start: stdout = %q, want %q",
-				got, wantPayload)
-		}
-	})
-
-	t.Run("start helper and wait", func(t *testing.T) {
-		ctx, cancel := context.WithTimeout(t.Context(), containerTimeout)
-		defer cancel()
-		stdout := new(strings.Builder)
-		h := createHelper(ctx, func(stdoutP, stderrP *io.Writer) { *stdoutP, *stderrP = stdout, os.Stderr }, false)
-
-		if err := h.Start(); err != nil {
-			t.Errorf("Start: error = %v",
-				err)
-			return
-		}
-
-		if err := h.Wait(); err != nil {
-			t.Errorf("Wait: error = %v stdout = %q",
-				err, stdout)
-		}
-
-		if got := trimStdout(stdout); got != wantPayload {
-			t.Errorf("Start: stdout = %q, want %q",
-				got, wantPayload)
-		}
-	})
-}
-
-func trimStdout(stdout fmt.Stringer) string {
-	return strings.TrimPrefix(stdout.String(), "=== RUN   TestHelperInit\n")
-}
diff --git a/helper/proc/deprecated.go b/helper/proc/deprecated.go
new file mode 100644
index 00000000..91897526
--- /dev/null
+++ b/helper/proc/deprecated.go
@@ -0,0 +1,63 @@
+// Deprecated: This package will be removed in 0.4.
+package proc
+
+import (
+	"context"
+	"io"
+	"os"
+	"os/exec"
+	"time"
+	_ "unsafe" // for go:linkname
+
+	"hakurei.app/internal/helper/proc"
+)
+
+//go:linkname FulfillmentTimeout hakurei.app/internal/helper/proc.FulfillmentTimeout
+var FulfillmentTimeout time.Duration
+
+// A File is an extra file with deferred initialisation.
+type File = proc.File
+
+// ExtraFilesPre is a linked list storing addresses of [os.File].
+type ExtraFilesPre = proc.ExtraFilesPre
+
+// Fulfill calls the [File.Fulfill] method on all files, starts cmd and blocks until all fulfillment completes.
+//
+//go:linkname Fulfill hakurei.app/internal/helper/proc.Fulfill
+func Fulfill(ctx context.Context,
+	v *[]*os.File, start func() error,
+	files []File, extraFiles *ExtraFilesPre,
+) (err error)
+
+// InitFile initialises f as part of the slice extraFiles points to,
+// and returns its final fd value.
+//
+//go:linkname InitFile hakurei.app/internal/helper/proc.InitFile
+func InitFile(f File, extraFiles *ExtraFilesPre) (fd uintptr)
+
+// BaseFile implements the Init method of the File interface and provides indirect access to extra file state.
+type BaseFile = proc.BaseFile
+
+//go:linkname ExtraFile hakurei.app/internal/helper/proc.ExtraFile
+func ExtraFile(cmd *exec.Cmd, f *os.File) (fd uintptr)
+
+//go:linkname ExtraFileSlice hakurei.app/internal/helper/proc.ExtraFileSlice
+func ExtraFileSlice(extraFiles *[]*os.File, f *os.File) (fd uintptr)
+
+// NewWriterTo returns a [File] that receives content from wt on fulfillment.
+//
+//go:linkname NewWriterTo hakurei.app/internal/helper/proc.NewWriterTo
+func NewWriterTo(wt io.WriterTo) File
+
+// NewStat returns a [File] implementing the behaviour
+// of the receiving end of xdg-dbus-proxy stat fd.
+//
+//go:linkname NewStat hakurei.app/internal/helper/proc.NewStat
+func NewStat(s *io.Closer) File
+
+var (
+	//go:linkname ErrStatFault hakurei.app/internal/helper/proc.ErrStatFault
+	ErrStatFault error
+	//go:linkname ErrStatRead hakurei.app/internal/helper/proc.ErrStatRead
+	ErrStatRead error
+)
diff --git a/helper/proc/files.go b/helper/proc/files.go
deleted file mode 100644
index 0612718e..00000000
--- a/helper/proc/files.go
+++ /dev/null
@@ -1,162 +0,0 @@
-package proc
-
-import (
-	"context"
-	"os"
-	"os/exec"
-	"sync/atomic"
-	"syscall"
-	"testing"
-	"time"
-)
-
-var FulfillmentTimeout = 2 * time.Second
-
-func init() {
-	if testing.Testing() {
-		FulfillmentTimeout *= 10
-	}
-}
-
-// A File is an extra file with deferred initialisation.
-type File interface {
-	// Init initialises File state. Init must not be called more than once.
-	Init(fd uintptr, v **os.File) uintptr
-	// Fd returns the fd value set on initialisation.
-	Fd() uintptr
-	// ErrCount returns count of error values emitted during fulfillment.
-	ErrCount() int
-	// Fulfill is called prior to process creation and must populate its corresponding file address.
-	// Calls to dispatchErr must match the return value of ErrCount.
-	// Fulfill must not be called more than once.
-	Fulfill(ctx context.Context, dispatchErr func(error)) error
-}
-
-// ExtraFilesPre is a linked list storing addresses of [os.File].
-type ExtraFilesPre struct {
-	n *ExtraFilesPre
-	v *os.File
-}
-
-// Append grows the list by one entry and returns an address of the address of [os.File] stored in the new entry.
-func (f *ExtraFilesPre) Append() (uintptr, **os.File) { return f.append(3) }
-
-// Files returns a slice pointing to a continuous segment of memory containing all addresses stored in f in order.
-func (f *ExtraFilesPre) Files() []*os.File { return f.copy(make([]*os.File, 0, f.len())) }
-
-func (f *ExtraFilesPre) append(i uintptr) (uintptr, **os.File) {
-	if f.n == nil {
-		f.n = new(ExtraFilesPre)
-		return i, &f.v
-	}
-	return f.n.append(i + 1)
-}
-func (f *ExtraFilesPre) len() uintptr {
-	if f == nil {
-		return 0
-	}
-	return f.n.len() + 1
-}
-func (f *ExtraFilesPre) copy(e []*os.File) []*os.File {
-	if f == nil {
-		// the public methods ensure the first call is never nil;
-		// the last element is unused, slice it off here
-		return e[:len(e)-1]
-	}
-	return f.n.copy(append(e, f.v))
-}
-
-// Fulfill calls the [File.Fulfill] method on all files, starts cmd and blocks until all fulfillment completes.
-func Fulfill(ctx context.Context,
-	v *[]*os.File, start func() error,
-	files []File, extraFiles *ExtraFilesPre,
-) (err error) {
-	var ecs int
-	for _, o := range files {
-		ecs += o.ErrCount()
-	}
-	ec := make(chan error, ecs)
-
-	c, cancel := context.WithTimeout(ctx, FulfillmentTimeout)
-	defer cancel()
-
-	for _, f := range files {
-		err = f.Fulfill(c, makeDispatchErr(f, ec))
-		if err != nil {
-			return
-		}
-	}
-
-	*v = extraFiles.Files()
-	if err = start(); err != nil {
-		return
-	}
-
-	for ecs > 0 {
-		select {
-		case err = <-ec:
-			ecs--
-			if err != nil {
-				break
-			}
-		case <-ctx.Done():
-			err = syscall.ECANCELED
-			break
-		}
-	}
-	return
-}
-
-// InitFile initialises f as part of the slice extraFiles points to,
-// and returns its final fd value.
-func InitFile(f File, extraFiles *ExtraFilesPre) (fd uintptr) { return f.Init(extraFiles.Append()) }
-
-// BaseFile implements the Init method of the File interface and provides indirect access to extra file state.
-type BaseFile struct {
-	fd uintptr
-	v  **os.File
-}
-
-func (f *BaseFile) Init(fd uintptr, v **os.File) uintptr {
-	if v == nil || fd < 3 {
-		panic("invalid extra file initial state")
-	}
-	if f.v != nil {
-		panic("extra file initialised twice")
-	}
-	f.fd, f.v = fd, v
-	return fd
-}
-
-func (f *BaseFile) Fd() uintptr {
-	if f.v == nil {
-		panic("use of uninitialised extra file")
-	}
-	return f.fd
-}
-
-func (f *BaseFile) Set(v *os.File) {
-	*f.v = v // runtime guards against use before init
-}
-
-func makeDispatchErr(f File, ec chan<- error) func(error) {
-	c := new(atomic.Int32)
-	c.Store(int32(f.ErrCount()))
-	return func(err error) {
-		if c.Add(-1) < 0 {
-			panic("unexpected error dispatches")
-		}
-		ec <- err
-	}
-}
-
-func ExtraFile(cmd *exec.Cmd, f *os.File) (fd uintptr) {
-	return ExtraFileSlice(&cmd.ExtraFiles, f)
-}
-
-func ExtraFileSlice(extraFiles *[]*os.File, f *os.File) (fd uintptr) {
-	// ExtraFiles: If non-nil, entry i becomes file descriptor 3+i.
-	fd = uintptr(3 + len(*extraFiles))
-	*extraFiles = append(*extraFiles, f)
-	return
-}
diff --git a/helper/proc/pipe.go b/helper/proc/pipe.go
deleted file mode 100644
index 838c4ae4..00000000
--- a/helper/proc/pipe.go
+++ /dev/null
@@ -1,110 +0,0 @@
-package proc
-
-import (
-	"context"
-	"errors"
-	"io"
-	"os"
-	"runtime"
-)
-
-// NewWriterTo returns a [File] that receives content from wt on fulfillment.
-func NewWriterTo(wt io.WriterTo) File { return &writeToFile{wt: wt} }
-
-// writeToFile exports the read end of a pipe with data written by an [io.WriterTo].
-type writeToFile struct {
-	wt io.WriterTo
-	BaseFile
-}
-
-func (f *writeToFile) ErrCount() int { return 3 }
-func (f *writeToFile) Fulfill(ctx context.Context, dispatchErr func(error)) error {
-	r, w, err := os.Pipe()
-	if err != nil {
-		return err
-	}
-	f.Set(r)
-
-	done := make(chan struct{})
-	go func() {
-		_, err = f.wt.WriteTo(w)
-		dispatchErr(err)
-		dispatchErr(w.Close())
-		close(done)
-		runtime.KeepAlive(r)
-	}()
-	go func() {
-		select {
-		case <-done:
-			dispatchErr(nil)
-		case <-ctx.Done():
-			dispatchErr(w.Close()) // this aborts WriteTo with file already closed
-			runtime.KeepAlive(r)
-		}
-	}()
-
-	return nil
-}
-
-// NewStat returns a [File] implementing the behaviour
-// of the receiving end of xdg-dbus-proxy stat fd.
-func NewStat(s *io.Closer) File { return &statFile{s: s} }
-
-var (
-	ErrStatFault = errors.New("generic stat fd fault")
-	ErrStatRead  = errors.New("unexpected stat behaviour")
-)
-
-// statFile implements xdg-dbus-proxy stat fd behaviour.
-type statFile struct {
-	s *io.Closer
-	BaseFile
-}
-
-func (f *statFile) ErrCount() int { return 2 }
-func (f *statFile) Fulfill(ctx context.Context, dispatchErr func(error)) error {
-	r, w, err := os.Pipe()
-	if err != nil {
-		return err
-	}
-	f.Set(w)
-
-	done := make(chan struct{})
-	go func() {
-		defer close(done)
-		var n int
-
-		n, err = r.Read(make([]byte, 1))
-		switch n {
-		case -1:
-			if err == nil {
-				err = ErrStatFault
-			}
-			dispatchErr(err)
-		case 0:
-			if err == nil {
-				err = ErrStatRead
-			}
-			dispatchErr(err)
-		case 1:
-			dispatchErr(err)
-		default:
-			panic("unreachable")
-		}
-		runtime.KeepAlive(w)
-	}()
-
-	go func() {
-		select {
-		case <-done:
-			dispatchErr(nil)
-		case <-ctx.Done():
-			dispatchErr(r.Close()) // this aborts Read with file already closed
-			runtime.KeepAlive(w)
-		}
-	}()
-
-	// this gets closed by the caller
-	*f.s = r
-	return nil
-}
diff --git a/helper/stub.go b/helper/stub.go
deleted file mode 100644
index c1f97e63..00000000
--- a/helper/stub.go
+++ /dev/null
@@ -1,102 +0,0 @@
-package helper
-
-import (
-	"flag"
-	"fmt"
-	"io"
-	"os"
-	"strconv"
-	"syscall"
-)
-
-// InternalHelperStub is an internal function but exported because it is cross-package;
-// it is part of the implementation of the helper stub.
-func InternalHelperStub() {
-	// this test mocks the helper process
-	var ap, sp string
-	if v, ok := os.LookupEnv(HakureiHelper); !ok {
-		return
-	} else {
-		ap = v
-	}
-	if v, ok := os.LookupEnv(HakureiStatus); !ok {
-		panic(HakureiStatus)
-	} else {
-		sp = v
-	}
-
-	genericStub(flagRestoreFiles(1, ap, sp))
-
-	os.Exit(0)
-}
-
-func newFile(fd int, name, p string) *os.File {
-	present := false
-	switch p {
-	case "0":
-	case "1":
-		present = true
-	default:
-		panic(fmt.Sprintf("%s fd has unexpected presence value %q", name, p))
-	}
-
-	f := os.NewFile(uintptr(fd), name)
-	if !present && f != nil {
-		panic(fmt.Sprintf("%s fd set but not present", name))
-	}
-	if present && f == nil {
-		panic(fmt.Sprintf("%s fd preset but unset", name))
-	}
-
-	return f
-}
-
-func flagRestoreFiles(offset int, ap, sp string) (argsFile, statFile *os.File) {
-	argsFd := flag.Int("args", -1, "")
-	statFd := flag.Int("fd", -1, "")
-	_ = flag.CommandLine.Parse(os.Args[offset:])
-	argsFile = newFile(*argsFd, "args", ap)
-	statFile = newFile(*statFd, "stat", sp)
-	return
-}
-
-func genericStub(argsFile, statFile *os.File) {
-	if argsFile != nil {
-		// this output is checked by parent
-		if _, err := io.Copy(os.Stdout, argsFile); err != nil {
-			panic("cannot read args: " + err.Error())
-		}
-	}
-
-	if statFile != nil {
-		// simulate status pipe behaviour
-		var epoll int
-		if fd, err := syscall.EpollCreate1(0); err != nil {
-			panic("cannot open epoll fd: " + err.Error())
-		} else {
-			defer func() {
-				if err = syscall.Close(fd); err != nil {
-					panic("cannot close epoll fd: " + err.Error())
-				}
-			}()
-			epoll = fd
-		}
-		if err := syscall.EpollCtl(epoll, syscall.EPOLL_CTL_ADD, int(statFile.Fd()), &syscall.EpollEvent{}); err != nil {
-			panic("cannot add status pipe to epoll: " + err.Error())
-		}
-
-		if _, err := statFile.Write([]byte{'x'}); err != nil {
-			panic("cannot write to status pipe: " + err.Error())
-		}
-
-		// wait for status pipe close
-		events := make([]syscall.EpollEvent, 1)
-		if _, err := syscall.EpollWait(epoll, events, -1); err != nil {
-			panic("cannot poll status pipe: " + err.Error())
-		}
-		if events[0].Events != syscall.EPOLLERR {
-			panic(strconv.Itoa(int(events[0].Events)))
-
-		}
-	}
-}
diff --git a/helper/stub_test.go b/helper/stub_test.go
deleted file mode 100644
index 58a25383..00000000
--- a/helper/stub_test.go
+++ /dev/null
@@ -1,11 +0,0 @@
-package helper_test
-
-import (
-	"os"
-	"testing"
-
-	"hakurei.app/container"
-	"hakurei.app/helper"
-)
-
-func TestMain(m *testing.M) { container.TryArgv0(nil); helper.InternalHelperStub(); os.Exit(m.Run()) }