wasi: add nonblock_test.go from gotip, fix nonblock read on Unix-like (#1517)

Signed-off-by: Edoardo Vacchi <evacchi@users.noreply.github.com>

imports/wasi_snapshot_preview1/testdata/gotip/wasi.go

@@ -6,6 +6,7 @@ import (
 	"net"
 	"net/http"
 	"os"
+	"sync"
 	"syscall"
 )
 
@@ -19,6 +20,10 @@ func main() {
 		if err := mainHTTP(); err != nil {
 			panic(err)
 		}
+	case "nonblock":
+		if err := mainNonblock(os.Args[2], os.Args[3:]); err != nil {
+			panic(err)
+		}
 	}
 }
 
@@ -100,3 +105,58 @@ func (e echoOnce) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	// Once one request was served, close the channel.
 	close(e.ch)
 }
+
+// Adapted from nonblock.go
+// https://github.com/golang/go/blob/0fcc70ecd56e3b5c214ddaee4065ea1139ae16b5/src/runtime/internal/wasitest/testdata/nonblock.go
+func mainNonblock(mode string, files []string) error {
+	ready := make(chan struct{})
+
+	var wg sync.WaitGroup
+	for _, path := range files {
+		f, err := os.Open(path)
+		if err != nil {
+			return err
+		}
+		switch mode {
+		case "open":
+		case "create":
+			fd := f.Fd()
+			if err = syscall.SetNonblock(int(fd), true); err != nil {
+				return err
+			}
+			f = os.NewFile(fd, path)
+		default:
+			return fmt.Errorf("invalid test mode")
+		}
+
+		spawnWait := make(chan struct{})
+
+		wg.Add(1)
+		go func(f *os.File) {
+			defer f.Close()
+			defer wg.Done()
+
+			// Signal the routine has been spawned.
+			close(spawnWait)
+
+			// Wait until ready.
+			<-ready
+
+			var buf [256]byte
+
+			if n, err := f.Read(buf[:]); err != nil {
+				panic(err)
+			} else {
+				os.Stderr.Write(buf[:n])
+			}
+		}(f)
+
+		// Spawn one goroutine at a time.
+		<-spawnWait
+	}
+
+	println("waiting")
+	close(ready)
+	wg.Wait()
+	return nil
+}

imports/wasi_snapshot_preview1/wasi_stdlib_unix_test.go

@@ -3,14 +3,22 @@
 package wasi_snapshot_preview1_test
 
 import (
+	"bufio"
+	"bytes"
+	"fmt"
+	"io"
+	"math/rand"
 	"os"
+	"path/filepath"
 	"strings"
 	"syscall"
 	"testing"
 
 	"github.com/tetratelabs/wazero"
 	"github.com/tetratelabs/wazero/api"
+	"github.com/tetratelabs/wazero/imports/wasi_snapshot_preview1"
 	"github.com/tetratelabs/wazero/internal/testing/require"
+	"github.com/tetratelabs/wazero/sys"
 )
 
 func Test_NonblockingFile(t *testing.T) {
@@ -53,3 +61,96 @@ func Test_NonblockingFile(t *testing.T) {
 	require.True(t, strings.HasPrefix(lines[0], "."))
 	require.Equal(t, "wazero", lines[1])
 }
+
+type fifo struct {
+	file *os.File
+	path string
+}
+
+func Test_NonblockGotip(t *testing.T) {
+	// - Create `numFifos` FIFOs.
+	// - Instantiate `wasmGotip` with the names of the FIFO in the order of creation
+	// - The test binary opens the FIFOs in the given order and spawns a goroutine for each
+	// - The unit test writes to the FIFO in reverse order.
+	// - Each goroutine reads from the given FIFO and writes the contents to stderr
+	//
+	// The test verifies that the output order matches the write order (i.e. reverse order).
+	//
+	// If I/O was blocking, all goroutines would be blocked waiting for one read call
+	// to return, and the output order wouldn't match.
+	//
+	// Adapted from https://github.com/golang/go/blob/0fcc70ecd56e3b5c214ddaee4065ea1139ae16b5/src/runtime/internal/wasitest/nonblock_test.go
+
+	if wasmGotip == nil {
+		t.Skip("skipping because wasi.go was not compiled (gotip missing or compilation error)")
+	}
+	const numFifos = 8
+
+	for _, mode := range []string{"open", "create"} {
+		t.Run(mode, func(t *testing.T) {
+			tempDir := t.TempDir()
+
+			args := []string{"wasi", "nonblock", mode}
+			fifos := make([]*fifo, numFifos)
+			for i := range fifos {
+				tempFile := fmt.Sprintf("wasip1-nonblock-fifo-%d-%d", rand.Uint32(), i)
+				path := filepath.Join(tempDir, tempFile)
+				err := syscall.Mkfifo(path, 0o666)
+				require.NoError(t, err)
+
+				file, err := os.OpenFile(path, os.O_RDWR, 0)
+				require.NoError(t, err)
+				defer file.Close()
+
+				args = append(args, tempFile)
+				fifos[len(fifos)-i-1] = &fifo{file, path}
+			}
+
+			pr, pw := io.Pipe()
+			defer pw.Close()
+
+			var consoleBuf bytes.Buffer
+
+			moduleConfig := wazero.NewModuleConfig().
+				WithArgs(args...).
+				WithFSConfig( // Mount the tempDir as root.
+						wazero.NewFSConfig().WithDirMount(tempDir, "/")).
+				WithStderr(pw). // Write Stderr to pw
+				WithStdout(&consoleBuf).
+				WithStartFunctions().
+				WithSysNanosleep()
+
+			ch := make(chan string, 1)
+			go func() {
+				r := wazero.NewRuntime(testCtx)
+				defer r.Close(testCtx)
+
+				_, err := wasi_snapshot_preview1.Instantiate(testCtx, r)
+				require.NoError(t, err)
+
+				mod, err := r.InstantiateWithConfig(testCtx, wasmGotip, moduleConfig) // clear
+				require.NoError(t, err)
+
+				_, err = mod.ExportedFunction("_start").Call(testCtx)
+				if exitErr, ok := err.(*sys.ExitError); ok {
+					require.Zero(t, exitErr.ExitCode(), consoleBuf.String())
+				}
+				ch <- consoleBuf.String()
+			}()
+
+			scanner := bufio.NewScanner(pr)
+			require.True(t, scanner.Scan(), fmt.Sprintf("expected line: %s", scanner.Err()))
+			require.Equal(t, "waiting", scanner.Text(), fmt.Sprintf("unexpected output: %s", scanner.Text()))
+
+			for _, fifo := range fifos {
+				_, err := fifo.file.WriteString(fifo.path + "\n")
+				require.NoError(t, err)
+				require.True(t, scanner.Scan(), fmt.Sprintf("expected line: %s", scanner.Err()))
+				require.Equal(t, fifo.path, scanner.Text(), fmt.Sprintf("unexpected line: %s", scanner.Text()))
+			}
+
+			s := <-ch
+			require.Equal(t, "", s)
+		})
+	}
+}

internal/sysfs/file_test.go

@@ -28,7 +28,7 @@ var (
 	emptyFile  = "empty.txt"
 )
 
-func TestFileSetNonblock(t *testing.T) {
+func TestStdioFileSetNonblock(t *testing.T) {
 	// Test using os.Pipe as it is known to support non-blocking reads.
 	r, w, err := os.Pipe()
 	require.NoError(t, err)
@@ -47,6 +47,54 @@ func TestFileSetNonblock(t *testing.T) {
 	require.False(t, rF.IsNonblock())
 }
 
+func TestRegularFileSetNonblock(t *testing.T) {
+	if runtime.GOOS == "windows" {
+		t.Skip("Nonblock on regular files is not supported on Windows")
+	}
+
+	// Test using os.Pipe as it is known to support non-blocking reads.
+	r, w, err := os.Pipe()
+	require.NoError(t, err)
+	defer r.Close()
+	defer w.Close()
+
+	rF := newOsFile("", syscall.O_RDONLY, 0, r)
+
+	errno := rF.SetNonblock(true)
+	require.EqualErrno(t, 0, errno)
+	require.True(t, rF.IsNonblock())
+
+	// Read from the file without ever writing to it should not block.
+	buf := make([]byte, 8)
+	_, e := rF.Read(buf)
+	require.EqualErrno(t, syscall.EAGAIN, e)
+
+	errno = rF.SetNonblock(false)
+	require.EqualErrno(t, 0, errno)
+	require.False(t, rF.IsNonblock())
+}
+
+func TestReadFdNonblock(t *testing.T) {
+	// Test using os.Pipe as it is known to support non-blocking reads.
+	r, w, err := os.Pipe()
+	require.NoError(t, err)
+	defer r.Close()
+	defer w.Close()
+
+	fd := r.Fd()
+	err = setNonblock(fd, true)
+	require.NoError(t, err)
+
+	// Read from the file without ever writing to it should not block.
+	buf := make([]byte, 8)
+	_, e := readFd(fd, buf)
+	if runtime.GOOS == "windows" {
+		require.EqualErrno(t, syscall.ENOSYS, e)
+	} else {
+		require.EqualErrno(t, syscall.EAGAIN, e)
+	}
+}
+
 func TestFileSetAppend(t *testing.T) {
 	tmpDir := t.TempDir()
 

internal/sysfs/file_unix.go

@@ -0,0 +1,21 @@
+//go:build unix || darwin || linux
+
+package sysfs
+
+import (
+	"syscall"
+
+	"github.com/tetratelabs/wazero/internal/platform"
+)
+
+const NonBlockingFileIoSupported = true
+
+// readFd exposes syscall.Read.
+func readFd(fd uintptr, buf []byte) (int, syscall.Errno) {
+	if len(buf) == 0 {
+		return 0, 0 // Short-circuit 0-len reads.
+	}
+	n, err := syscall.Read(int(fd), buf)
+	errno := platform.UnwrapOSError(err)
+	return n, errno
+}

internal/sysfs/file_unsupported.go

@@ -0,0 +1,12 @@
+//go:build !unix && !linux && !darwin
+
+package sysfs
+
+import "syscall"
+
+const NonBlockingFileIoSupported = false
+
+// readFd returns ENOSYS on unsupported platforms.
+func readFd(fd uintptr, buf []byte) (int, syscall.Errno) {
+	return -1, syscall.ENOSYS
+}

internal/sysfs/open_file_windows.go

@@ -13,7 +13,7 @@ import (
 
 func newOsFile(openPath string, openFlag int, openPerm fs.FileMode, f *os.File) fsapi.File {
 	return &windowsOsFile{
-		osFile: osFile{path: openPath, flag: openFlag, perm: openPerm, file: f},
+		osFile: osFile{path: openPath, flag: openFlag, perm: openPerm, file: f, fd: f.Fd()},
 	}
 }
 

internal/sysfs/osfile.go

@@ -12,7 +12,7 @@ import (
 )
 
 func newDefaultOsFile(openPath string, openFlag int, openPerm fs.FileMode, f *os.File) fsapi.File {
-	return &osFile{path: openPath, flag: openFlag, perm: openPerm, file: f}
+	return &osFile{path: openPath, flag: openFlag, perm: openPerm, file: f, fd: f.Fd()}
 }
 
 // osFile is a file opened with this package, and uses os.File or syscalls to
@@ -22,6 +22,7 @@ type osFile struct {
 	flag int
 	perm fs.FileMode
 	file *os.File
+	fd   uintptr
 
 	// closed is true when closed was called. This ensures proper syscall.EBADF
 	closed bool
@@ -92,7 +93,7 @@ func (f *osFile) SetNonblock(enable bool) (errno syscall.Errno) {
 	} else {
 		f.flag &= ^fsapi.O_NONBLOCK
 	}
-	if err := setNonblock(f.file.Fd(), enable); err != nil {
+	if err := setNonblock(f.fd, enable); err != nil {
 		return fileError(f, f.closed, platform.UnwrapOSError(err))
 	}
 	return 0
@@ -126,7 +127,15 @@ func (f *osFile) Stat() (fsapi.Stat_t, syscall.Errno) {
 
 // Read implements the same method as documented on fsapi.File
 func (f *osFile) Read(buf []byte) (n int, errno syscall.Errno) {
-	if n, errno = read(f.file, buf); errno != 0 {
+	if len(buf) == 0 {
+		return 0, 0 // Short-circuit 0-len reads.
+	}
+	if NonBlockingFileIoSupported && f.IsNonblock() {
+		n, errno = readFd(f.fd, buf)
+	} else {
+		n, errno = read(f.file, buf)
+	}
+	if errno != 0 {
 		// Defer validation overhead until we've already had an error.
 		errno = fileError(f, f.closed, errno)
 	}
@@ -160,7 +169,7 @@ func (f *osFile) Seek(offset int64, whence int) (newOffset int64, errno syscall.
 // PollRead implements the same method as documented on fsapi.File
 func (f *osFile) PollRead(timeout *time.Duration) (ready bool, errno syscall.Errno) {
 	fdSet := platform.FdSet{}
-	fd := int(f.file.Fd())
+	fd := int(f.fd)
 	fdSet.Set(fd)
 	nfds := fd + 1 // See https://man7.org/linux/man-pages/man2/select.2.html#:~:text=condition%20has%20occurred.-,nfds,-This%20argument%20should
 	count, err := _select(nfds, &fdSet, nil, nil, timeout)
@@ -232,7 +241,7 @@ func (f *osFile) Chown(uid, gid int) syscall.Errno {
 		return syscall.EBADF
 	}
 
-	return fchown(f.file.Fd(), uid, gid)
+	return fchown(f.fd, uid, gid)
 }
 
 // Utimens implements the same method as documented on fsapi.File
@@ -241,7 +250,7 @@ func (f *osFile) Utimens(times *[2]syscall.Timespec) syscall.Errno {
 		return syscall.EBADF
 	}
 
-	err := futimens(f.file.Fd(), times)
+	err := futimens(f.fd, times)
 	return platform.UnwrapOSError(err)
 }