misc/go_android_exec/main.go - toolchain/go - Git at Google

 // Copyright 2014 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.

 // This wrapper uses syscall.Flock to prevent concurrent adb commands,
 // so for now it only builds on platforms that support that system call.
 // TODO(#33974): use a more portable library for file locking.

 //go:build darwin || dragonfly || freebsd || illumos || linux || netbsd || openbsd

 // This program can be used as go_android_GOARCH_exec by the Go tool.
 // It executes binaries on an android device using adb.
 package main

 import (
 	"bytes"
 	"errors"
 	"fmt"
 	"io"
 	"log"
 	"os"
 	"os/exec"
 	"os/signal"
 	"path"
 	"path/filepath"
 	"regexp"
 	"runtime"
 	"strconv"
 	"strings"
 	"sync"
 	"syscall"
 )

 func adbRun(args string) (int, error) {
 	// The exit code of adb is often wrong. In theory it was fixed in 2016
 	// (https://code.google.com/p/android/issues/detail?id=3254), but it's
 	// still broken on our builders in 2023. Instead, append the exitcode to
 	// the output and parse it from there.
 	filter, exitStr := newExitCodeFilter(os.Stdout)
 	args += "; echo -n " + exitStr + "$?"

 	cmd := adbCmd("exec-out", args)
 	cmd.Stdout = filter
 	// If the adb subprocess somehow hangs, go test will kill this wrapper
 	// and wait for our os.Stderr (and os.Stdout) to close as a result.
 	// However, if the os.Stderr (or os.Stdout) file descriptors are
 	// passed on, the hanging adb subprocess will hold them open and
 	// go test will hang forever.
 	//
 	// Avoid that by wrapping stderr, breaking the short circuit and
 	// forcing cmd.Run to use another pipe and goroutine to pass
 	// along stderr from adb.
 	cmd.Stderr = struct{ io.Writer }{os.Stderr}
 	err := cmd.Run()

 	// Before we process err, flush any further output and get the exit code.
 	exitCode, err2 := filter.Finish()

 	if err != nil {
 		return 0, fmt.Errorf("adb exec-out %s: %v", args, err)
 	}
 	return exitCode, err2
 }

 func adb(args ...string) error {
 	if out, err := adbCmd(args...).CombinedOutput(); err != nil {
 		fmt.Fprintf(os.Stderr, "adb %s\n%s", strings.Join(args, " "), out)
 		return err
 	}
 	return nil
 }

 func adbCmd(args ...string) *exec.Cmd {
 	if flags := os.Getenv("GOANDROID_ADB_FLAGS"); flags != "" {
 		args = append(strings.Split(flags, " "), args...)
 	}
 	return exec.Command("adb", args...)
 }

 const (
 	deviceRoot   = "/data/local/tmp/go_android_exec"
 	deviceGoroot = deviceRoot + "/goroot"
 )

 func main() {
 	log.SetFlags(0)
 	log.SetPrefix("go_android_exec: ")
 	exitCode, err := runMain()
 	if err != nil {
 		log.Fatal(err)
 	}
 	os.Exit(exitCode)
 }

 func runMain() (int, error) {
 	// Concurrent use of adb is flaky, so serialize adb commands.
 	// See https://github.com/golang/go/issues/23795 or
 	// https://issuetracker.google.com/issues/73230216.
 	lockPath := filepath.Join(os.TempDir(), "go_android_exec-adb-lock")
 	lock, err := os.OpenFile(lockPath, os.O_CREATE|os.O_RDWR, 0666)
 	if err != nil {
 		return 0, err
 	}
 	defer lock.Close()
 	if err := syscall.Flock(int(lock.Fd()), syscall.LOCK_EX); err != nil {
 		return 0, err
 	}

 	// In case we're booting a device or emulator alongside all.bash, wait for
 	// it to be ready. adb wait-for-device is not enough, we have to
 	// wait for sys.boot_completed.
 	if err := adb("wait-for-device", "exec-out", "while [[ -z $(getprop sys.boot_completed) ]]; do sleep 1; done;"); err != nil {
 		return 0, err
 	}

 	// Done once per make.bash.
 	if err := adbCopyGoroot(); err != nil {
 		return 0, err
 	}

 	// Prepare a temporary directory that will be cleaned up at the end.
 	// Binary names can conflict.
 	// E.g. template.test from the {html,text}/template packages.
 	binName := filepath.Base(os.Args[1])
 	deviceGotmp := fmt.Sprintf(deviceRoot+"/%s-%d", binName, os.Getpid())
 	deviceGopath := deviceGotmp + "/gopath"
 	defer adb("exec-out", "rm", "-rf", deviceGotmp) // Clean up.

 	// Determine the package by examining the current working
 	// directory, which will look something like
 	// "$GOROOT/src/mime/multipart" or "$GOPATH/src/golang.org/x/mobile".
 	// We extract everything after the $GOROOT or $GOPATH to run on the
 	// same relative directory on the target device.
 	importPath, isStd, modPath, modDir, err := pkgPath()
 	if err != nil {
 		return 0, err
 	}
 	var deviceCwd string
 	if isStd {
 		// Note that we use path.Join here instead of filepath.Join:
 		// The device paths should be slash-separated even if the go_android_exec
 		// wrapper itself is compiled for Windows.
 		deviceCwd = path.Join(deviceGoroot, "src", importPath)
 	} else {
 		deviceCwd = path.Join(deviceGopath, "src", importPath)
 		if modDir != "" {
 			// In module mode, the user may reasonably expect the entire module
 			// to be present. Copy it over.
 			deviceModDir := path.Join(deviceGopath, "src", modPath)
 			if err := adb("exec-out", "mkdir", "-p", path.Dir(deviceModDir)); err != nil {
 				return 0, err
 			}
 			// We use a single recursive 'adb push' of the module root instead of
 			// walking the tree and copying it piecewise. If the directory tree
 			// contains nested modules this could push a lot of unnecessary contents,
 			// but for the golang.org/x repos it seems to be significantly (~2x)
 			// faster than copying one file at a time (via filepath.WalkDir),
 			// apparently due to high latency in 'adb' commands.
 			if err := adb("push", modDir, deviceModDir); err != nil {
 				return 0, err
 			}
 		} else {
 			if err := adb("exec-out", "mkdir", "-p", deviceCwd); err != nil {
 				return 0, err
 			}
 			if err := adbCopyTree(deviceCwd, importPath); err != nil {
 				return 0, err
 			}

 			// Copy .go files from the package.
 			goFiles, err := filepath.Glob("*.go")
 			if err != nil {
 				return 0, err
 			}
 			if len(goFiles) > 0 {
 				args := append(append([]string{"push"}, goFiles...), deviceCwd)
 				if err := adb(args...); err != nil {
 					return 0, err
 				}
 			}
 		}
 	}

 	deviceBin := fmt.Sprintf("%s/%s", deviceGotmp, binName)
 	if err := adb("push", os.Args[1], deviceBin); err != nil {
 		return 0, err
 	}

 	// Forward SIGQUIT from the go command to show backtraces from
 	// the binary instead of from this wrapper.
 	quit := make(chan os.Signal, 1)
 	signal.Notify(quit, syscall.SIGQUIT)
 	go func() {
 		for range quit {
 			// We don't have the PID of the running process; use the
 			// binary name instead.
 			adb("exec-out", "killall -QUIT "+binName)
 		}
 	}()
 	cmd := `export TMPDIR="` + deviceGotmp + `"` +
 		`; export GOROOT="` + deviceGoroot + `"` +
 		`; export GOPATH="` + deviceGopath + `"` +
 		`; export CGO_ENABLED=0` +
 		`; export GOPROXY=` + os.Getenv("GOPROXY") +
 		`; export GOCACHE="` + deviceRoot + `/gocache"` +
 		`; export PATH="` + deviceGoroot + `/bin":$PATH` +
 		`; export HOME="` + deviceRoot + `/home"` +
 		`; cd "` + deviceCwd + `"` +
 		"; '" + deviceBin + "' " + strings.Join(os.Args[2:], " ")
 	code, err := adbRun(cmd)
 	signal.Reset(syscall.SIGQUIT)
 	close(quit)
 	return code, err
 }

 type exitCodeFilter struct {
 	w      io.Writer // Pass through to w
 	exitRe *regexp.Regexp
 	buf    bytes.Buffer
 }

 func newExitCodeFilter(w io.Writer) (*exitCodeFilter, string) {
 	const exitStr = "exitcode="

 	// Build a regexp that matches any prefix of the exit string at the end of
 	// the input. We do it this way to avoid assuming anything about the
 	// subcommand output (e.g., it might not be \n-terminated).
 	var exitReStr strings.Builder
 	for i := 1; i <= len(exitStr); i++ {
 		fmt.Fprintf(&exitReStr, "%s$|", exitStr[:i])
 	}
 	// Finally, match the exit string along with an exit code.
 	// This is the only case we use a group, and we'll use this
 	// group to extract the numeric code.
 	fmt.Fprintf(&exitReStr, "%s([0-9]+)$", exitStr)
 	exitRe := regexp.MustCompile(exitReStr.String())

 	return &exitCodeFilter{w: w, exitRe: exitRe}, exitStr
 }

 func (f *exitCodeFilter) Write(data []byte) (int, error) {
 	n := len(data)
 	f.buf.Write(data)
 	// Flush to w until a potential match of exitRe
 	b := f.buf.Bytes()
 	match := f.exitRe.FindIndex(b)
 	if match == nil {
 		// Flush all of the buffer.
 		_, err := f.w.Write(b)
 		f.buf.Reset()
 		if err != nil {
 			return n, err
 		}
 	} else {
 		// Flush up to the beginning of the (potential) match.
 		_, err := f.w.Write(b[:match[0]])
 		f.buf.Next(match[0])
 		if err != nil {
 			return n, err
 		}
 	}
 	return n, nil
 }

 func (f *exitCodeFilter) Finish() (int, error) {
 	// f.buf could be empty, contain a partial match of exitRe, or
 	// contain a full match.
 	b := f.buf.Bytes()
 	defer f.buf.Reset()
 	match := f.exitRe.FindSubmatch(b)
 	if len(match) < 2 || match[1] == nil {
 		// Not a full match. Flush.
 		if _, err := f.w.Write(b); err != nil {
 			return 0, err
 		}
 		return 0, fmt.Errorf("no exit code (in %q)", string(b))
 	}

 	// Parse the exit code.
 	code, err := strconv.Atoi(string(match[1]))
 	if err != nil {
 		// Something is malformed. Flush.
 		if _, err := f.w.Write(b); err != nil {
 			return 0, err
 		}
 		return 0, fmt.Errorf("bad exit code: %v (in %q)", err, string(b))
 	}
 	return code, nil
 }

 // pkgPath determines the package import path of the current working directory,
 // and indicates whether it is
 // and returns the path to the package source relative to $GOROOT (or $GOPATH).
 func pkgPath() (importPath string, isStd bool, modPath, modDir string, err error) {
 	errorf := func(format string, args ...any) (string, bool, string, string, error) {
 		return "", false, "", "", fmt.Errorf(format, args...)
 	}
 	goTool, err := goTool()
 	if err != nil {
 		return errorf("%w", err)
 	}
 	cmd := exec.Command(goTool, "list", "-e", "-f", "{{.ImportPath}}:{{.Standard}}{{with .Module}}:{{.Path}}:{{.Dir}}{{end}}", ".")
 	out, err := cmd.Output()
 	if err != nil {
 		if ee, ok := err.(*exec.ExitError); ok && len(ee.Stderr) > 0 {
 			return errorf("%v: %s", cmd, ee.Stderr)
 		}
 		return errorf("%v: %w", cmd, err)
 	}

 	parts := strings.SplitN(string(bytes.TrimSpace(out)), ":", 4)
 	if len(parts) < 2 {
 		return errorf("%v: missing ':' in output: %q", cmd, out)
 	}
 	importPath = parts[0]
 	if importPath == "" || importPath == "." {
 		return errorf("current directory does not have a Go import path")
 	}
 	isStd, err = strconv.ParseBool(parts[1])
 	if err != nil {
 		return errorf("%v: non-boolean .Standard in output: %q", cmd, out)
 	}
 	if len(parts) >= 4 {
 		modPath = parts[2]
 		modDir = parts[3]
 	}

 	return importPath, isStd, modPath, modDir, nil
 }

 // adbCopyTree copies testdata, go.mod, go.sum files from subdir
 // and from parent directories all the way up to the root of subdir.
 // go.mod and go.sum files are needed for the go tool modules queries,
 // and the testdata directories for tests.  It is common for tests to
 // reach out into testdata from parent packages.
 func adbCopyTree(deviceCwd, subdir string) error {
 	dir := ""
 	for {
 		for _, name := range []string{"testdata", "go.mod", "go.sum"} {
 			hostPath := filepath.Join(dir, name)
 			if _, err := os.Stat(hostPath); err != nil {
 				continue
 			}
 			devicePath := path.Join(deviceCwd, dir)
 			if err := adb("exec-out", "mkdir", "-p", devicePath); err != nil {
 				return err
 			}
 			if err := adb("push", hostPath, devicePath); err != nil {
 				return err
 			}
 		}
 		if subdir == "." {
 			break
 		}
 		subdir = filepath.Dir(subdir)
 		dir = path.Join(dir, "..")
 	}
 	return nil
 }

 // adbCopyGoroot clears deviceRoot for previous versions of GOROOT, GOPATH
 // and temporary data. Then, it copies relevant parts of GOROOT to the device,
 // including the go tool built for android.
 // A lock file ensures this only happens once, even with concurrent exec
 // wrappers.
 func adbCopyGoroot() error {
 	goTool, err := goTool()
 	if err != nil {
 		return err
 	}
 	cmd := exec.Command(goTool, "version")
 	cmd.Stderr = os.Stderr
 	out, err := cmd.Output()
 	if err != nil {
 		return fmt.Errorf("%v: %w", cmd, err)
 	}
 	goVersion := string(out)

 	// Also known by cmd/dist. The bootstrap command deletes the file.
 	statPath := filepath.Join(os.TempDir(), "go_android_exec-adb-sync-status")
 	stat, err := os.OpenFile(statPath, os.O_CREATE|os.O_RDWR, 0666)
 	if err != nil {
 		return err
 	}
 	defer stat.Close()
 	// Serialize check and copying.
 	if err := syscall.Flock(int(stat.Fd()), syscall.LOCK_EX); err != nil {
 		return err
 	}
 	s, err := io.ReadAll(stat)
 	if err != nil {
 		return err
 	}
 	if string(s) == goVersion {
 		return nil
 	}

 	goroot, err := findGoroot()
 	if err != nil {
 		return err
 	}

 	// Delete the device's GOROOT, GOPATH and any leftover test data,
 	// and recreate GOROOT.
 	if err := adb("exec-out", "rm", "-rf", deviceRoot); err != nil {
 		return err
 	}

 	// Build Go for Android.
 	cmd = exec.Command(goTool, "install", "cmd")
 	out, err = cmd.CombinedOutput()
 	if err != nil {
 		if len(bytes.TrimSpace(out)) > 0 {
 			log.Printf("\n%s", out)
 		}
 		return fmt.Errorf("%v: %w", cmd, err)
 	}
 	if err := adb("exec-out", "mkdir", "-p", deviceGoroot); err != nil {
 		return err
 	}

 	// Copy the Android tools from the relevant bin subdirectory to GOROOT/bin.
 	cmd = exec.Command(goTool, "list", "-f", "{{.Target}}", "cmd/go")
 	cmd.Stderr = os.Stderr
 	out, err = cmd.Output()
 	if err != nil {
 		return fmt.Errorf("%v: %w", cmd, err)
 	}
 	platformBin := filepath.Dir(string(bytes.TrimSpace(out)))
 	if platformBin == "." {
 		return errors.New("failed to locate cmd/go for target platform")
 	}
 	if err := adb("push", platformBin, path.Join(deviceGoroot, "bin")); err != nil {
 		return err
 	}

 	// Copy only the relevant subdirectories from pkg: pkg/include and the
 	// platform-native binaries in pkg/tool.
 	if err := adb("exec-out", "mkdir", "-p", path.Join(deviceGoroot, "pkg", "tool")); err != nil {
 		return err
 	}
 	if err := adb("push", filepath.Join(goroot, "pkg", "include"), path.Join(deviceGoroot, "pkg", "include")); err != nil {
 		return err
 	}

 	cmd = exec.Command(goTool, "list", "-f", "{{.Target}}", "cmd/compile")
 	cmd.Stderr = os.Stderr
 	out, err = cmd.Output()
 	if err != nil {
 		return fmt.Errorf("%v: %w", cmd, err)
 	}
 	platformToolDir := filepath.Dir(string(bytes.TrimSpace(out)))
 	if platformToolDir == "." {
 		return errors.New("failed to locate cmd/compile for target platform")
 	}
 	relToolDir, err := filepath.Rel(filepath.Join(goroot), platformToolDir)
 	if err != nil {
 		return err
 	}
 	if err := adb("push", platformToolDir, path.Join(deviceGoroot, relToolDir)); err != nil {
 		return err
 	}

 	// Copy all other files from GOROOT.
 	dirents, err := os.ReadDir(goroot)
 	if err != nil {
 		return err
 	}
 	for _, de := range dirents {
 		switch de.Name() {
 		case "bin", "pkg":
 			// We already created GOROOT/bin and GOROOT/pkg above; skip those.
 			continue
 		}
 		if err := adb("push", filepath.Join(goroot, de.Name()), path.Join(deviceGoroot, de.Name())); err != nil {
 			return err
 		}
 	}

 	if _, err := stat.WriteString(goVersion); err != nil {
 		return err
 	}
 	return nil
 }

 func findGoroot() (string, error) {
 	gorootOnce.Do(func() {
 		// If runtime.GOROOT reports a non-empty path, assume that it is valid.
 		// (It may be empty if this binary was built with -trimpath.)
 		gorootPath = runtime.GOROOT()
 		if gorootPath != "" {
 			return
 		}

 		// runtime.GOROOT is empty — perhaps go_android_exec was built with
 		// -trimpath and GOROOT is unset. Try 'go env GOROOT' as a fallback,
 		// assuming that the 'go' command in $PATH is the correct one.

 		cmd := exec.Command("go", "env", "GOROOT")
 		cmd.Stderr = os.Stderr
 		out, err := cmd.Output()
 		if err != nil {
 			gorootErr = fmt.Errorf("%v: %w", cmd, err)
 		}

 		gorootPath = string(bytes.TrimSpace(out))
 		if gorootPath == "" {
 			gorootErr = errors.New("GOROOT not found")
 		}
 	})

 	return gorootPath, gorootErr
 }

 func goTool() (string, error) {
 	goroot, err := findGoroot()
 	if err != nil {
 		return "", err
 	}
 	return filepath.Join(goroot, "bin", "go"), nil
 }

 var (
 	gorootOnce sync.Once
 	gorootPath string
 	gorootErr  error
 )
	// Copyright 2014 The Go Authors. All rights reserved.
	// Use of this source code is governed by a BSD-style
	// license that can be found in the LICENSE file.

	// This wrapper uses syscall.Flock to prevent concurrent adb commands,
	// so for now it only builds on platforms that support that system call.
	// TODO(#33974): use a more portable library for file locking.

	//go:build darwin \|\| dragonfly \|\| freebsd \|\| illumos \|\| linux \|\| netbsd \|\| openbsd

	// This program can be used as go_android_GOARCH_exec by the Go tool.
	// It executes binaries on an android device using adb.
	package main

	import (
	"bytes"
	"errors"
	"fmt"
	"io"
	"log"
	"os"
	"os/exec"
	"os/signal"
	"path"
	"path/filepath"
	"regexp"
	"runtime"
	"strconv"
	"strings"
	"sync"
	"syscall"
	)

	func adbRun(args string) (int, error) {
	// The exit code of adb is often wrong. In theory it was fixed in 2016
	// (https://code.google.com/p/android/issues/detail?id=3254), but it's
	// still broken on our builders in 2023. Instead, append the exitcode to
	// the output and parse it from there.
	filter, exitStr := newExitCodeFilter(os.Stdout)
	args += "; echo -n " + exitStr + "$?"

	cmd := adbCmd("exec-out", args)
	cmd.Stdout = filter
	// If the adb subprocess somehow hangs, go test will kill this wrapper
	// and wait for our os.Stderr (and os.Stdout) to close as a result.
	// However, if the os.Stderr (or os.Stdout) file descriptors are
	// passed on, the hanging adb subprocess will hold them open and
	// go test will hang forever.
	//
	// Avoid that by wrapping stderr, breaking the short circuit and
	// forcing cmd.Run to use another pipe and goroutine to pass
	// along stderr from adb.
	cmd.Stderr = struct{ io.Writer }{os.Stderr}
	err := cmd.Run()

	// Before we process err, flush any further output and get the exit code.
	exitCode, err2 := filter.Finish()

	if err != nil {
	return 0, fmt.Errorf("adb exec-out %s: %v", args, err)
	}
	return exitCode, err2
	}

	func adb(args ...string) error {
	if out, err := adbCmd(args...).CombinedOutput(); err != nil {
	fmt.Fprintf(os.Stderr, "adb %s\n%s", strings.Join(args, " "), out)
	return err
	}
	return nil
	}

	func adbCmd(args ...string) *exec.Cmd {
	if flags := os.Getenv("GOANDROID_ADB_FLAGS"); flags != "" {
	args = append(strings.Split(flags, " "), args...)
	}
	return exec.Command("adb", args...)
	}

	const (
	deviceRoot = "/data/local/tmp/go_android_exec"
	deviceGoroot = deviceRoot + "/goroot"
	)

	func main() {
	log.SetFlags(0)
	log.SetPrefix("go_android_exec: ")
	exitCode, err := runMain()
	if err != nil {
	log.Fatal(err)
	}
	os.Exit(exitCode)
	}

	func runMain() (int, error) {
	// Concurrent use of adb is flaky, so serialize adb commands.
	// See https://github.com/golang/go/issues/23795 or
	// https://issuetracker.google.com/issues/73230216.
	lockPath := filepath.Join(os.TempDir(), "go_android_exec-adb-lock")
	lock, err := os.OpenFile(lockPath, os.O_CREATE\|os.O_RDWR, 0666)
	if err != nil {
	return 0, err
	}
	defer lock.Close()
	if err := syscall.Flock(int(lock.Fd()), syscall.LOCK_EX); err != nil {
	return 0, err
	}

	// In case we're booting a device or emulator alongside all.bash, wait for
	// it to be ready. adb wait-for-device is not enough, we have to
	// wait for sys.boot_completed.
	if err := adb("wait-for-device", "exec-out", "while [[ -z $(getprop sys.boot_completed) ]]; do sleep 1; done;"); err != nil {
	return 0, err
	}

	// Done once per make.bash.
	if err := adbCopyGoroot(); err != nil {
	return 0, err
	}

	// Prepare a temporary directory that will be cleaned up at the end.
	// Binary names can conflict.
	// E.g. template.test from the {html,text}/template packages.
	binName := filepath.Base(os.Args[1])
	deviceGotmp := fmt.Sprintf(deviceRoot+"/%s-%d", binName, os.Getpid())
	deviceGopath := deviceGotmp + "/gopath"
	defer adb("exec-out", "rm", "-rf", deviceGotmp) // Clean up.

	// Determine the package by examining the current working
	// directory, which will look something like
	// "$GOROOT/src/mime/multipart" or "$GOPATH/src/golang.org/x/mobile".
	// We extract everything after the $GOROOT or $GOPATH to run on the
	// same relative directory on the target device.
	importPath, isStd, modPath, modDir, err := pkgPath()
	if err != nil {
	return 0, err
	}
	var deviceCwd string
	if isStd {
	// Note that we use path.Join here instead of filepath.Join:
	// The device paths should be slash-separated even if the go_android_exec
	// wrapper itself is compiled for Windows.
	deviceCwd = path.Join(deviceGoroot, "src", importPath)
	} else {
	deviceCwd = path.Join(deviceGopath, "src", importPath)
	if modDir != "" {
	// In module mode, the user may reasonably expect the entire module
	// to be present. Copy it over.
	deviceModDir := path.Join(deviceGopath, "src", modPath)
	if err := adb("exec-out", "mkdir", "-p", path.Dir(deviceModDir)); err != nil {
	return 0, err
	}
	// We use a single recursive 'adb push' of the module root instead of
	// walking the tree and copying it piecewise. If the directory tree
	// contains nested modules this could push a lot of unnecessary contents,
	// but for the golang.org/x repos it seems to be significantly (~2x)
	// faster than copying one file at a time (via filepath.WalkDir),
	// apparently due to high latency in 'adb' commands.
	if err := adb("push", modDir, deviceModDir); err != nil {
	return 0, err
	}
	} else {
	if err := adb("exec-out", "mkdir", "-p", deviceCwd); err != nil {
	return 0, err
	}
	if err := adbCopyTree(deviceCwd, importPath); err != nil {
	return 0, err
	}

	// Copy .go files from the package.
	goFiles, err := filepath.Glob("*.go")
	if err != nil {
	return 0, err
	}
	if len(goFiles) > 0 {
	args := append(append([]string{"push"}, goFiles...), deviceCwd)
	if err := adb(args...); err != nil {
	return 0, err
	}
	}
	}
	}

	deviceBin := fmt.Sprintf("%s/%s", deviceGotmp, binName)
	if err := adb("push", os.Args[1], deviceBin); err != nil {
	return 0, err
	}

	// Forward SIGQUIT from the go command to show backtraces from
	// the binary instead of from this wrapper.
	quit := make(chan os.Signal, 1)
	signal.Notify(quit, syscall.SIGQUIT)
	go func() {
	for range quit {
	// We don't have the PID of the running process; use the
	// binary name instead.
	adb("exec-out", "killall -QUIT "+binName)
	}
	}()
	cmd := `export TMPDIR="` + deviceGotmp + `"` +
	`; export GOROOT="` + deviceGoroot + `"` +
	`; export GOPATH="` + deviceGopath + `"` +
	`; export CGO_ENABLED=0` +
	`; export GOPROXY=` + os.Getenv("GOPROXY") +
	`; export GOCACHE="` + deviceRoot + `/gocache"` +
	`; export PATH="` + deviceGoroot + `/bin":$PATH` +
	`; export HOME="` + deviceRoot + `/home"` +
	`; cd "` + deviceCwd + `"` +
	"; '" + deviceBin + "' " + strings.Join(os.Args[2:], " ")
	code, err := adbRun(cmd)
	signal.Reset(syscall.SIGQUIT)
	close(quit)
	return code, err
	}

	type exitCodeFilter struct {
	w io.Writer // Pass through to w
	exitRe *regexp.Regexp
	buf bytes.Buffer
	}

	func newExitCodeFilter(w io.Writer) (*exitCodeFilter, string) {
	const exitStr = "exitcode="

	// Build a regexp that matches any prefix of the exit string at the end of
	// the input. We do it this way to avoid assuming anything about the
	// subcommand output (e.g., it might not be \n-terminated).
	var exitReStr strings.Builder
	for i := 1; i <= len(exitStr); i++ {
	fmt.Fprintf(&exitReStr, "%s$\|", exitStr[:i])
	}
	// Finally, match the exit string along with an exit code.
	// This is the only case we use a group, and we'll use this
	// group to extract the numeric code.
	fmt.Fprintf(&exitReStr, "%s([0-9]+)$", exitStr)
	exitRe := regexp.MustCompile(exitReStr.String())

	return &exitCodeFilter{w: w, exitRe: exitRe}, exitStr
	}

	func (f *exitCodeFilter) Write(data []byte) (int, error) {
	n := len(data)
	f.buf.Write(data)
	// Flush to w until a potential match of exitRe
	b := f.buf.Bytes()
	match := f.exitRe.FindIndex(b)
	if match == nil {
	// Flush all of the buffer.
	_, err := f.w.Write(b)
	f.buf.Reset()
	if err != nil {
	return n, err
	}
	} else {
	// Flush up to the beginning of the (potential) match.
	_, err := f.w.Write(b[:match[0]])
	f.buf.Next(match[0])
	if err != nil {
	return n, err
	}
	}
	return n, nil
	}

	func (f *exitCodeFilter) Finish() (int, error) {
	// f.buf could be empty, contain a partial match of exitRe, or
	// contain a full match.
	b := f.buf.Bytes()
	defer f.buf.Reset()
	match := f.exitRe.FindSubmatch(b)
	if len(match) < 2 \|\| match[1] == nil {
	// Not a full match. Flush.
	if _, err := f.w.Write(b); err != nil {
	return 0, err
	}
	return 0, fmt.Errorf("no exit code (in %q)", string(b))
	}

	// Parse the exit code.
	code, err := strconv.Atoi(string(match[1]))
	if err != nil {
	// Something is malformed. Flush.
	if _, err := f.w.Write(b); err != nil {
	return 0, err
	}
	return 0, fmt.Errorf("bad exit code: %v (in %q)", err, string(b))
	}
	return code, nil
	}

	// pkgPath determines the package import path of the current working directory,
	// and indicates whether it is
	// and returns the path to the package source relative to $GOROOT (or $GOPATH).
	func pkgPath() (importPath string, isStd bool, modPath, modDir string, err error) {
	errorf := func(format string, args ...any) (string, bool, string, string, error) {
	return "", false, "", "", fmt.Errorf(format, args...)
	}
	goTool, err := goTool()
	if err != nil {
	return errorf("%w", err)
	}
	cmd := exec.Command(goTool, "list", "-e", "-f", "{{.ImportPath}}:{{.Standard}}{{with .Module}}:{{.Path}}:{{.Dir}}{{end}}", ".")
	out, err := cmd.Output()
	if err != nil {
	if ee, ok := err.(*exec.ExitError); ok && len(ee.Stderr) > 0 {
	return errorf("%v: %s", cmd, ee.Stderr)
	}
	return errorf("%v: %w", cmd, err)
	}

	parts := strings.SplitN(string(bytes.TrimSpace(out)), ":", 4)
	if len(parts) < 2 {
	return errorf("%v: missing ':' in output: %q", cmd, out)
	}
	importPath = parts[0]
	if importPath == "" \|\| importPath == "." {
	return errorf("current directory does not have a Go import path")
	}
	isStd, err = strconv.ParseBool(parts[1])
	if err != nil {
	return errorf("%v: non-boolean .Standard in output: %q", cmd, out)
	}
	if len(parts) >= 4 {
	modPath = parts[2]
	modDir = parts[3]
	}

	return importPath, isStd, modPath, modDir, nil
	}

	// adbCopyTree copies testdata, go.mod, go.sum files from subdir
	// and from parent directories all the way up to the root of subdir.
	// go.mod and go.sum files are needed for the go tool modules queries,
	// and the testdata directories for tests. It is common for tests to
	// reach out into testdata from parent packages.
	func adbCopyTree(deviceCwd, subdir string) error {
	dir := ""
	for {
	for _, name := range []string{"testdata", "go.mod", "go.sum"} {
	hostPath := filepath.Join(dir, name)
	if _, err := os.Stat(hostPath); err != nil {
	continue
	}
	devicePath := path.Join(deviceCwd, dir)
	if err := adb("exec-out", "mkdir", "-p", devicePath); err != nil {
	return err
	}
	if err := adb("push", hostPath, devicePath); err != nil {
	return err
	}
	}
	if subdir == "." {
	break
	}
	subdir = filepath.Dir(subdir)
	dir = path.Join(dir, "..")
	}
	return nil
	}

	// adbCopyGoroot clears deviceRoot for previous versions of GOROOT, GOPATH
	// and temporary data. Then, it copies relevant parts of GOROOT to the device,
	// including the go tool built for android.
	// A lock file ensures this only happens once, even with concurrent exec
	// wrappers.
	func adbCopyGoroot() error {
	goTool, err := goTool()
	if err != nil {
	return err
	}
	cmd := exec.Command(goTool, "version")
	cmd.Stderr = os.Stderr
	out, err := cmd.Output()
	if err != nil {
	return fmt.Errorf("%v: %w", cmd, err)
	}
	goVersion := string(out)

	// Also known by cmd/dist. The bootstrap command deletes the file.
	statPath := filepath.Join(os.TempDir(), "go_android_exec-adb-sync-status")
	stat, err := os.OpenFile(statPath, os.O_CREATE\|os.O_RDWR, 0666)
	if err != nil {
	return err
	}
	defer stat.Close()
	// Serialize check and copying.
	if err := syscall.Flock(int(stat.Fd()), syscall.LOCK_EX); err != nil {
	return err
	}
	s, err := io.ReadAll(stat)
	if err != nil {
	return err
	}
	if string(s) == goVersion {
	return nil
	}

	goroot, err := findGoroot()
	if err != nil {
	return err
	}

	// Delete the device's GOROOT, GOPATH and any leftover test data,
	// and recreate GOROOT.
	if err := adb("exec-out", "rm", "-rf", deviceRoot); err != nil {
	return err
	}

	// Build Go for Android.
	cmd = exec.Command(goTool, "install", "cmd")
	out, err = cmd.CombinedOutput()
	if err != nil {
	if len(bytes.TrimSpace(out)) > 0 {
	log.Printf("\n%s", out)
	}
	return fmt.Errorf("%v: %w", cmd, err)
	}
	if err := adb("exec-out", "mkdir", "-p", deviceGoroot); err != nil {
	return err
	}

	// Copy the Android tools from the relevant bin subdirectory to GOROOT/bin.
	cmd = exec.Command(goTool, "list", "-f", "{{.Target}}", "cmd/go")
	cmd.Stderr = os.Stderr
	out, err = cmd.Output()
	if err != nil {
	return fmt.Errorf("%v: %w", cmd, err)
	}
	platformBin := filepath.Dir(string(bytes.TrimSpace(out)))
	if platformBin == "." {
	return errors.New("failed to locate cmd/go for target platform")
	}
	if err := adb("push", platformBin, path.Join(deviceGoroot, "bin")); err != nil {
	return err
	}

	// Copy only the relevant subdirectories from pkg: pkg/include and the
	// platform-native binaries in pkg/tool.
	if err := adb("exec-out", "mkdir", "-p", path.Join(deviceGoroot, "pkg", "tool")); err != nil {
	return err
	}
	if err := adb("push", filepath.Join(goroot, "pkg", "include"), path.Join(deviceGoroot, "pkg", "include")); err != nil {
	return err
	}

	cmd = exec.Command(goTool, "list", "-f", "{{.Target}}", "cmd/compile")
	cmd.Stderr = os.Stderr
	out, err = cmd.Output()
	if err != nil {
	return fmt.Errorf("%v: %w", cmd, err)
	}
	platformToolDir := filepath.Dir(string(bytes.TrimSpace(out)))
	if platformToolDir == "." {
	return errors.New("failed to locate cmd/compile for target platform")
	}
	relToolDir, err := filepath.Rel(filepath.Join(goroot), platformToolDir)
	if err != nil {
	return err
	}
	if err := adb("push", platformToolDir, path.Join(deviceGoroot, relToolDir)); err != nil {
	return err
	}

	// Copy all other files from GOROOT.
	dirents, err := os.ReadDir(goroot)
	if err != nil {
	return err
	}
	for _, de := range dirents {
	switch de.Name() {
	case "bin", "pkg":
	// We already created GOROOT/bin and GOROOT/pkg above; skip those.
	continue
	}
	if err := adb("push", filepath.Join(goroot, de.Name()), path.Join(deviceGoroot, de.Name())); err != nil {
	return err
	}
	}

	if _, err := stat.WriteString(goVersion); err != nil {
	return err
	}
	return nil
	}

	func findGoroot() (string, error) {
	gorootOnce.Do(func() {
	// If runtime.GOROOT reports a non-empty path, assume that it is valid.
	// (It may be empty if this binary was built with -trimpath.)
	gorootPath = runtime.GOROOT()
	if gorootPath != "" {
	return
	}

	// runtime.GOROOT is empty — perhaps go_android_exec was built with
	// -trimpath and GOROOT is unset. Try 'go env GOROOT' as a fallback,
	// assuming that the 'go' command in $PATH is the correct one.

	cmd := exec.Command("go", "env", "GOROOT")
	cmd.Stderr = os.Stderr
	out, err := cmd.Output()
	if err != nil {
	gorootErr = fmt.Errorf("%v: %w", cmd, err)
	}

	gorootPath = string(bytes.TrimSpace(out))
	if gorootPath == "" {
	gorootErr = errors.New("GOROOT not found")
	}
	})

	return gorootPath, gorootErr
	}

	func goTool() (string, error) {
	goroot, err := findGoroot()
	if err != nil {
	return "", err
	}
	return filepath.Join(goroot, "bin", "go"), nil
	}

	var (
	gorootOnce sync.Once
	gorootPath string
	gorootErr error
	)