wasi: improve stdin support for nonblocking, fix stdout (#1542)

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

imports/wasi_snapshot_preview1/fs_test.go

@@ -423,41 +423,41 @@ func Test_fdFdstatGet_StdioNonblock(t *testing.T) {
 			fd:   sys.FdStdin,
 			expectedMemory: []byte{
 				0, 0, // fs_filetype
-				4, 0, 0, 0, 0, 0, // fs_flags
+				5, 0, 0, 0, 0, 0, // fs_flags
 				0xff, 0x1, 0xe0, 0x8, 0x0, 0x0, 0x0, 0x0, // fs_rights_base
 				0, 0, 0, 0, 0, 0, 0, 0, // fs_rights_inheriting
 			},
 			expectedLog: `
 ==> wasi_snapshot_preview1.fd_fdstat_get(fd=0)
-<== (stat={filetype=UNKNOWN,fdflags=NONBLOCK,fs_rights_base=FD_DATASYNC|FD_READ|FD_SEEK|FDSTAT_SET_FLAGS|FD_SYNC|FD_TELL|FD_WRITE|FD_ADVISE|FD_ALLOCATE,fs_rights_inheriting=},errno=ESUCCESS)
+<== (stat={filetype=UNKNOWN,fdflags=APPEND|NONBLOCK,fs_rights_base=FD_DATASYNC|FD_READ|FD_SEEK|FDSTAT_SET_FLAGS|FD_SYNC|FD_TELL|FD_WRITE|FD_ADVISE|FD_ALLOCATE,fs_rights_inheriting=},errno=ESUCCESS)
 `,
 		},
 		{
 			name: "stdout",
 			fd:   sys.FdStdout,
 			expectedMemory: []byte{
 				0, 0, // fs_filetype
-				4, 0, 0, 0, 0, 0, // fs_flags
+				5, 0, 0, 0, 0, 0, // fs_flags
 				0xff, 0x1, 0xe0, 0x8, 0x0, 0x0, 0x0, 0x0, // fs_rights_base
 				0, 0, 0, 0, 0, 0, 0, 0, // fs_rights_inheriting
 			},
 			expectedLog: `
 ==> wasi_snapshot_preview1.fd_fdstat_get(fd=1)
-<== (stat={filetype=UNKNOWN,fdflags=NONBLOCK,fs_rights_base=FD_DATASYNC|FD_READ|FD_SEEK|FDSTAT_SET_FLAGS|FD_SYNC|FD_TELL|FD_WRITE|FD_ADVISE|FD_ALLOCATE,fs_rights_inheriting=},errno=ESUCCESS)
+<== (stat={filetype=UNKNOWN,fdflags=APPEND|NONBLOCK,fs_rights_base=FD_DATASYNC|FD_READ|FD_SEEK|FDSTAT_SET_FLAGS|FD_SYNC|FD_TELL|FD_WRITE|FD_ADVISE|FD_ALLOCATE,fs_rights_inheriting=},errno=ESUCCESS)
 `,
 		},
 		{
 			name: "stderr",
 			fd:   sys.FdStderr,
 			expectedMemory: []byte{
 				0, 0, // fs_filetype
-				4, 0, 0, 0, 0, 0, // fs_flags
+				5, 0, 0, 0, 0, 0, // fs_flags
 				0xff, 0x1, 0xe0, 0x8, 0x0, 0x0, 0x0, 0x0, // fs_rights_base
 				0, 0, 0, 0, 0, 0, 0, 0, // fs_rights_inheriting
 			},
 			expectedLog: `
 ==> wasi_snapshot_preview1.fd_fdstat_get(fd=2)
-<== (stat={filetype=UNKNOWN,fdflags=NONBLOCK,fs_rights_base=FD_DATASYNC|FD_READ|FD_SEEK|FDSTAT_SET_FLAGS|FD_SYNC|FD_TELL|FD_WRITE|FD_ADVISE|FD_ALLOCATE,fs_rights_inheriting=},errno=ESUCCESS)
+<== (stat={filetype=UNKNOWN,fdflags=APPEND|NONBLOCK,fs_rights_base=FD_DATASYNC|FD_READ|FD_SEEK|FDSTAT_SET_FLAGS|FD_SYNC|FD_TELL|FD_WRITE|FD_ADVISE|FD_ALLOCATE,fs_rights_inheriting=},errno=ESUCCESS)
 `,
 		},
 	}

imports/wasi_snapshot_preview1/poll.go

@@ -86,8 +86,8 @@ func pollOneoffFn(_ context.Context, mod api.Module, params []uint64) syscall.Er
 
 	// Extract FS context, used in the body of the for loop for FS access.
 	fsc := mod.(*wasm.ModuleInstance).Sys.FS()
-	// Slice of events that are processed out of the loop (stdin subscribers).
-	var stdinSubs []*event
+	// Slice of events that are processed out of the loop (blocking stdin subscribers).
+	var blockingStdinSubs []*event
 	// The timeout is initialized at max Duration, the loop will find the minimum.
 	var timeout time.Duration = 1<<63 - 1
 	// Count of all the clock subscribers that have been already written back to outBuf.
@@ -131,12 +131,16 @@ func pollOneoffFn(_ context.Context, mod api.Module, params []uint64) syscall.Er
 			if fd < 0 {
 				return syscall.EBADF
 			}
-			if fd == internalsys.FdStdin {
-				// if the fd is Stdin, do not ack yet,
-				// append to a slice for delayed evaluation.
-				stdinSubs = append(stdinSubs, evt)
+			if file, ok := fsc.LookupFile(fd); !ok {
+				evt.errno = wasip1.ErrnoBadf
+				writeEvent(outBuf, evt)
+				readySubs++
+				continue
+			} else if fd == internalsys.FdStdin && !file.File.IsNonblock() {
+				// if the fd is Stdin, and it is in non-blocking mode,
+				// do not ack yet, append to a slice for delayed evaluation.
+				blockingStdinSubs = append(blockingStdinSubs, evt)
 			} else {
-				evt.errno = processFDEventRead(fsc, fd)
 				writeEvent(outBuf, evt)
 				readySubs++
 			}
@@ -145,7 +149,11 @@ func pollOneoffFn(_ context.Context, mod api.Module, params []uint64) syscall.Er
 			if fd < 0 {
 				return syscall.EBADF
 			}
-			evt.errno = processFDEventWrite(fsc, fd)
+			if _, ok := fsc.LookupFile(fd); ok {
+				evt.errno = wasip1.ErrnoNotsup
+			} else {
+				evt.errno = wasip1.ErrnoBadf
+			}
 			readySubs++
 			writeEvent(outBuf, evt)
 		default:
@@ -159,8 +167,8 @@ func pollOneoffFn(_ context.Context, mod api.Module, params []uint64) syscall.Er
 		timeout = 0
 	}
 
-	// If there are stdin subscribers, check for data with given timeout.
-	if len(stdinSubs) > 0 {
+	// If there are blocking stdin subscribers, check for data with given timeout.
+	if len(blockingStdinSubs) > 0 {
 		stdin, ok := fsc.LookupFile(internalsys.FdStdin)
 		if !ok {
 			return syscall.EBADF
@@ -172,9 +180,9 @@ func pollOneoffFn(_ context.Context, mod api.Module, params []uint64) syscall.Er
 		}
 		if stdinReady {
 			// stdin has data ready to for reading, write back all the events
-			for i := range stdinSubs {
+			for i := range blockingStdinSubs {
 				readySubs++
-				evt := stdinSubs[i]
+				evt := blockingStdinSubs[i]
 				evt.errno = 0
 				writeEvent(outBuf, evt)
 			}
@@ -223,23 +231,6 @@ func processClockEvent(inBuf []byte) (time.Duration, syscall.Errno) {
 	}
 }
 
-// processFDEventRead returns ErrnoSuccess if the file exists and ErrnoBadf otherwise.
-func processFDEventRead(fsc *internalsys.FSContext, fd int32) wasip1.Errno {
-	if _, ok := fsc.LookupFile(fd); ok {
-		return wasip1.ErrnoSuccess
-	} else {
-		return wasip1.ErrnoBadf
-	}
-}
-
-// processFDEventWrite returns ErrnoNotsup if the file exists and ErrnoBadf otherwise.
-func processFDEventWrite(fsc *internalsys.FSContext, fd int32) wasip1.Errno {
-	if _, ok := fsc.LookupFile(fd); ok {
-		return wasip1.ErrnoNotsup
-	}
-	return wasip1.ErrnoBadf
-}
-
 // writeEvent writes the event corresponding to the processed subscription.
 // https://github.com/WebAssembly/WASI/blob/snapshot-01/phases/snapshot/docs.md#-event-struct
 func writeEvent(outBuf []byte, evt *event) {

imports/wasi_snapshot_preview1/testdata/gotip/wasi.go

@@ -8,6 +8,7 @@ import (
 	"os"
 	"sync"
 	"syscall"
+	"time"
 )
 
 func main() {
@@ -24,7 +25,14 @@ func main() {
 		if err := mainNonblock(os.Args[2], os.Args[3:]); err != nil {
 			panic(err)
 		}
+	case "stdin":
+		if err := mainStdin(); err != nil {
+			panic(err)
+		}
+	case "stdout":
+		mainStdout()
 	}
+
 }
 
 // mainSock is an explicit test of a blocking socket.
@@ -160,3 +168,22 @@ func mainNonblock(mode string, files []string) error {
 	wg.Wait()
 	return nil
 }
+
+// Reproducer for https://github.com/tetratelabs/wazero/issues/1538
+func mainStdin() error {
+	go func() {
+		time.Sleep(1 * time.Second)
+		os.Stdout.WriteString("waiting for stdin...\n")
+	}()
+
+	b, err := io.ReadAll(os.Stdin)
+	if err != nil {
+		return err
+	}
+	os.Stdout.Write(b)
+	return nil
+}
+
+func mainStdout() {
+	os.Stdout.WriteString("test")
+}

imports/wasi_snapshot_preview1/wasi_stdlib_test.go

@@ -8,6 +8,7 @@ import (
 	"io/fs"
 	"net"
 	"net/http"
+	"os"
 	"runtime"
 	"strconv"
 	"strings"
@@ -457,3 +458,35 @@ func testHTTP(t *testing.T, bin []byte) {
 	console := <-ch
 	require.Equal(t, "", console)
 }
+
+func Test_Stdin(t *testing.T) {
+	toolchains := map[string][]byte{}
+	if wasmGotip != nil {
+		toolchains["gotip"] = wasmGotip
+	}
+
+	for toolchain, bin := range toolchains {
+		toolchain := toolchain
+		bin := bin
+		t.Run(toolchain, func(t *testing.T) {
+			testStdin(t, bin)
+		})
+	}
+}
+
+func testStdin(t *testing.T, bin []byte) {
+	r, w, err := os.Pipe()
+	require.NoError(t, err)
+	moduleConfig := wazero.NewModuleConfig().
+		WithSysNanotime(). // poll_oneoff requires nanotime.
+		WithArgs("wasi", "stdin").
+		WithStdin(r)
+	ch := make(chan string, 1)
+	go func() {
+		ch <- compileAndRun(t, testCtx, moduleConfig, bin)
+	}()
+	time.Sleep(1 * time.Second)
+	_, _ = w.WriteString("foo")
+	s := <-ch
+	require.Equal(t, "waiting for stdin...\nfoo", s)
+}

internal/sysfs/file.go

@@ -69,6 +69,17 @@ type stdioFile struct {
 	st fsapi.Stat_t
 }
 
+// SetAppend implements File.SetAppend
+func (f *stdioFile) SetAppend(bool) syscall.Errno {
+	// Ignore for stdio.
+	return 0
+}
+
+// IsAppend implements File.SetAppend
+func (f *stdioFile) IsAppend() bool {
+	return true
+}
+
 // IsDir implements File.IsDir
 func (f *stdioFile) IsDir() (bool, syscall.Errno) {
 	return false, 0

internal/sysfs/file_test.go

@@ -131,6 +131,16 @@ func TestFileSetAppend(t *testing.T) {
 	requireFileContent("wazero6789wazero")
 }
 
+func TestStdioFile_SetAppend(t *testing.T) {
+	// SetAppend should not affect Stdio.
+	file, err := NewStdioFile(false, os.Stdout)
+	require.NoError(t, err)
+	errno := file.SetAppend(true)
+	require.EqualErrno(t, 0, errno)
+	_, errno = file.Write([]byte{})
+	require.EqualErrno(t, 0, errno)
+}
+
 func TestFileIno(t *testing.T) {
 	tmpDir := t.TempDir()
 	dirFS, embedFS, mapFS := dirEmbedMapFS(t, tmpDir)