fix(wsl): Non-English system users cannot use wsl machine

When checking if WSL is already installed, podman relies on the English string returned by WSL.
However, in non-English systems, WSL will return content in the current system language (such as Chinese).
To avoid this situation, we cannot simply rely on the content returned by WSL and need to manually check if the kernel exists.

Signed-off-by: Kevin Cui <bh@bugs.cc>

pkg/machine/wsl/wutil/wutil.go

@@ -3,26 +3,27 @@
 package wutil
 
 import (
-	"bufio"
 	"fmt"
-	"io"
 	"os"
 	"os/exec"
 	"path/filepath"
-	"strings"
 	"sync"
 	"syscall"
 
 	"github.com/containers/storage/pkg/fileutils"
-	"golang.org/x/text/encoding/unicode"
-	"golang.org/x/text/transform"
+	"golang.org/x/sys/windows"
 )
 
 var (
 	once    sync.Once
 	wslPath string
 )
 
+const (
+	// https://learn.microsoft.com/en-us/windows/win32/procthread/process-creation-flags
+	flagsCreateNoWindow = 0x08000000
+)
+
 func FindWSL() string {
 	// At the time of this writing, a defect appeared in the OS preinstalled WSL executable
 	// where it no longer reliably locates the preferred Windows App Store variant.
@@ -32,16 +33,12 @@ func FindWSL() string {
 		var locs []string
 
 		// Prefer Windows App Store version
-		if localapp := getLocalAppData(); localapp != "" {
-			locs = append(locs, filepath.Join(localapp, "Microsoft", "WindowsApps", "wsl.exe"))
+		if p, ok := getLocalAppData(); ok {
+			locs = append(locs, filepath.Join(p, "Microsoft", "WindowsApps", "wsl.exe"))
 		}
 
 		// Otherwise, the common location for the legacy system version
-		root := os.Getenv("SystemRoot")
-		if root == "" {
-			root = `C:\Windows`
-		}
-		locs = append(locs, filepath.Join(root, "System32", "wsl.exe"))
+		locs = append(locs, filepath.Join(getSystem32Root(), "wsl.exe"))
 
 		for _, loc := range locs {
 			if err := fileutils.Exists(loc); err == nil {
@@ -57,22 +54,8 @@ func FindWSL() string {
 	return wslPath
 }
 
-func getLocalAppData() string {
-	localapp := os.Getenv("LOCALAPPDATA")
-	if localapp != "" {
-		return localapp
-	}
-
-	if user := os.Getenv("USERPROFILE"); user != "" {
-		return filepath.Join(user, "AppData", "Local")
-	}
-
-	return localapp
-}
-
 func SilentExec(command string, args ...string) error {
-	cmd := exec.Command(command, args...)
-	cmd.SysProcAttr = &syscall.SysProcAttr{CreationFlags: 0x08000000}
+	cmd := SilentExecCmd(command, args...)
 	cmd.Stdout = nil
 	cmd.Stderr = nil
 	if err := cmd.Run(); err != nil {
@@ -83,28 +66,22 @@ func SilentExec(command string, args ...string) error {
 
 func SilentExecCmd(command string, args ...string) *exec.Cmd {
 	cmd := exec.Command(command, args...)
-	cmd.SysProcAttr = &syscall.SysProcAttr{CreationFlags: 0x08000000}
+	cmd.SysProcAttr = &syscall.SysProcAttr{CreationFlags: flagsCreateNoWindow}
 	return cmd
 }
 
 func IsWSLInstalled() bool {
-	cmd := SilentExecCmd(FindWSL(), "--status")
-	out, err := cmd.StdoutPipe()
-	cmd.Stderr = nil
-	if err != nil {
+	// If the kernel file does not exist,
+	// it means that the current system has only enabled the Features without running wsl --update
+	if !existsKernel() {
 		return false
 	}
-	if err = cmd.Start(); err != nil {
-		return false
-	}
-
-	kernelNotFound := matchOutputLine(out, "kernel file is not found")
 
-	if err := cmd.Wait(); err != nil {
+	if err := SilentExec(FindWSL(), "--status"); err != nil {
 		return false
 	}
 
-	return !kernelNotFound
+	return true
 }
 
 func IsWSLStoreVersionInstalled() bool {
@@ -118,13 +95,50 @@ func IsWSLStoreVersionInstalled() bool {
 	return true
 }
 
-func matchOutputLine(output io.ReadCloser, match string) bool {
-	scanner := bufio.NewScanner(transform.NewReader(output, unicode.UTF16(unicode.LittleEndian, unicode.UseBOM).NewDecoder()))
-	for scanner.Scan() {
-		line := scanner.Text()
-		if strings.Contains(line, match) {
-			return true
-		}
+func existsKernel() bool {
+	// from `MSI` or `Windows Update`
+	kernel := filepath.Join(getSystem32Root(), "lxss", "tools", "kernel")
+	if err := fileutils.Exists(kernel); err == nil {
+		return true
+	}
+
+	// from `Microsoft Store` or `Github`
+	kernel = filepath.Join(getProgramFiles(), "WSL", "tools", "kernel")
+	if err := fileutils.Exists(kernel); err == nil {
+		return true
 	}
+
 	return false
 }
+
+func getLocalAppData() (result string, ok bool) {
+	if local := os.Getenv("LOCALAPPDATA"); local != "" {
+		return local, true
+	}
+
+	if user := os.Getenv("USERPROFILE"); user != "" {
+		return filepath.Join(user, "AppData", "Local"), true
+	}
+
+	return "", false
+}
+
+func getSystem32Root() string {
+	if p := os.Getenv("SystemRoot"); p != "" {
+		return filepath.Join(p, "System32")
+	}
+
+	if p, err := windows.GetSystemDirectory(); err == nil {
+		return p
+	}
+
+	return `C:\Windows\System32`
+}
+
+func getProgramFiles() string {
+	if p := os.Getenv("ProgramFiles"); p != "" {
+		return p
+	}
+
+	return `C:\Program Files`
+}