wasip2: Flesh out GETFL and SETFL (WebAssembly#668)

This commit implements `fcntl` with `F_GETFL` and `F_SETFL` in WASIp2.
Notably blocking flags are now maintained for files to get Python's test
suite passing.

Author: alexcrichton

libc-bottom-half/cloudlibc/src/libc/fcntl/fcntl.c

@@ -14,6 +14,11 @@
 #include <stdarg.h>
 
 int fcntl(int fildes, int cmd, ...) {
+#ifdef __wasilibc_use_wasip2
+  descriptor_table_entry_t *entry = descriptor_table_get_ref(fildes);
+  if (entry == NULL)
+    return -1;
+#endif
   switch (cmd) {
     case F_GETFD:
       // Act as if the close-on-exec flag is always set.
@@ -23,31 +28,11 @@ int fcntl(int fildes, int cmd, ...) {
       return 0;
     case F_GETFL: {
 #ifdef __wasilibc_use_wasip2
-    // Translate the file descriptor to an internal handle
-    filesystem_borrow_descriptor_t file_handle;
-    if (fd_to_file_handle(fildes, &file_handle) < 0)
-      return -1;
-
-    // Get the flags of the descriptor
-    filesystem_descriptor_flags_t flags;
-    filesystem_error_code_t error_code;
-    if (!filesystem_method_descriptor_get_flags(file_handle, &flags, &error_code)) {
-      translate_error(error_code);
-      return -1;
-    }
-
-    int oflags = 0;
-    if (flags & FILESYSTEM_DESCRIPTOR_FLAGS_READ) {
-      if (flags & FILESYSTEM_DESCRIPTOR_FLAGS_WRITE)
-        oflags |= O_RDWR;
-      else
-        oflags |= O_RDONLY;
-    } else if (flags & FILESYSTEM_DESCRIPTOR_FLAGS_WRITE)
-        oflags |= O_WRONLY;
-    else
-        oflags |= O_SEARCH;
-
-    return oflags;
+      if (!entry->vtable->fcntl_getfl) {
+        errno = EINVAL;
+        return -1;
+      }
+      return entry->vtable->fcntl_getfl(entry->data);
 #else
       // Obtain the flags and the rights of the descriptor.
       __wasi_fdstat_t fds;
@@ -81,12 +66,11 @@ int fcntl(int fildes, int cmd, ...) {
       va_end(ap);
 
 #ifdef __wasilibc_use_wasip2
-    // Translate the file descriptor to an internal handle
-    filesystem_borrow_descriptor_t file_handle;
-    if (fd_to_file_handle(fildes, &file_handle) < 0)
-      return -1;
-
-    // This is a no-op -- not supported in wasip2
+      if (!entry->vtable->fcntl_setfl) {
+        errno = EINVAL;
+        return -1;
+      }
+      return entry->vtable->fcntl_setfl(entry->data, flags);
 #else
       __wasi_fdflags_t fs_flags = flags & 0xfff;
       __wasi_errno_t error =

libc-bottom-half/cloudlibc/src/libc/sys/ioctl/ioctl.c

@@ -14,26 +14,6 @@
 #endif
 
 int ioctl(int fildes, int request, ...) {
-#ifdef __wasilibc_use_wasip2
-	descriptor_table_entry_t *entry = descriptor_table_get_ref(fildes);
-        if (!entry)
-          return -1;
-	switch (request) {
-	case FIONBIO: {
-		va_list ap;
-		va_start(ap, request);
-		bool blocking = *va_arg(ap, const int *) == 0;
-		va_end(ap);
-		return entry->vtable->set_blocking(entry->data, blocking);
-	}
-
-	default:
-		// TODO wasi-sockets: anything else we should support?
-		errno = EINVAL;
-		return -1;
-	}
-#endif // __wasilibc_use_wasip2
-
   switch (request) {
     case FIONREAD: {
 #ifdef __wasilibc_use_wasip2
@@ -87,9 +67,17 @@ int ioctl(int fildes, int request, ...) {
     }
     case FIONBIO: {
 #ifdef __wasilibc_use_wasip2
-      // wasip2 doesn't support setting the non-blocking flag
-      errno = ENOTSUP;
-      return -1;
+      descriptor_table_entry_t *entry = descriptor_table_get_ref(fildes);
+      va_list ap;
+      va_start(ap, request);
+      bool blocking = *va_arg(ap, const int *) == 0;
+      va_end(ap);
+
+      if (!entry->vtable->set_blocking) {
+        errno = EINVAL;
+        return -1;
+      }
+      return entry->vtable->set_blocking(entry->data, blocking);
 #else
       // Obtain the current file descriptor flags.
       __wasi_fdstat_t fds;

libc-bottom-half/headers/private/wasi/descriptor_table.h

@@ -53,6 +53,10 @@ typedef struct descriptor_vtable_t {
   /// closed before deleting the file to ensure there are no open references to
   /// it.
   void (*close_streams)(void*);
+  /// Implementation of `fnctl(fd, F_GETFL)`.
+  int (*fcntl_getfl)(void*);
+  /// Implementation of `fnctl(fd, F_SETFL)`.
+  int (*fcntl_setfl)(void*, int);
 
   // =====================================================================
   // Sockets-related APIs

libc-bottom-half/sources/wasip2_file.c

@@ -24,10 +24,7 @@ typedef struct {
   // and initially set to 0.
   streams_own_pollable_t read_pollable;
   streams_own_pollable_t write_pollable;
-  // File was opened for reading
-  bool readable;
-  // File was opened for writing
-  bool writable;
+  int oflag;
 } file_t;
 
 static void file_close_streams(void *data) {
@@ -172,14 +169,60 @@ static off_t file_seek(void *data, off_t offset, int whence) {
   return file->offset;
 }
 
+static int file_set_blocking(void *data, bool blocking) {
+  file_t *file = (file_t *)data;
+  if (blocking)
+    file->oflag &= ~O_NONBLOCK;
+  else
+    file->oflag |= O_NONBLOCK;
+  return 0;
+}
+
+static int file_fcntl_getfl(void *data) {
+  file_t *file = (file_t *)data;
+
+  // Get the flags of the descriptor
+  filesystem_descriptor_flags_t flags;
+  filesystem_error_code_t error_code;
+
+  filesystem_borrow_descriptor_t file_handle = filesystem_borrow_descriptor(file->file_handle);
+  if (!filesystem_method_descriptor_get_flags(file_handle, &flags, &error_code)) {
+    translate_error(error_code);
+    return -1;
+  }
+
+  int oflags = file->oflag & (O_NONBLOCK | O_APPEND);
+  if (flags & FILESYSTEM_DESCRIPTOR_FLAGS_READ) {
+    if (flags & FILESYSTEM_DESCRIPTOR_FLAGS_WRITE)
+      oflags |= O_RDWR;
+    else
+      oflags |= O_RDONLY;
+  } else if (flags & FILESYSTEM_DESCRIPTOR_FLAGS_WRITE) {
+      oflags |= O_WRONLY;
+  } else {
+      oflags |= O_SEARCH;
+  }
+  return oflags;
+}
+
+static int file_fcntl_setfl(void *data, int flags) {
+  file_t *file = (file_t *)data;
+  flags &= O_NONBLOCK | O_APPEND;
+  file->oflag = (file->oflag & ~(O_NONBLOCK | O_APPEND)) | flags;
+  return 0;
+}
+
 static descriptor_vtable_t file_vtable = {
   .free = file_free,
   .get_read_stream = file_get_read_stream,
   .get_write_stream = file_get_write_stream,
   .get_file = file_get_file,
+  .set_blocking = file_set_blocking,
   .fstat = file_fstat,
   .seek = file_seek,
   .close_streams = file_close_streams,
+  .fcntl_getfl = file_fcntl_getfl,
+  .fcntl_setfl = file_fcntl_setfl,
 };
 
 int __wasilibc_add_file(filesystem_own_descriptor_t file_handle, int oflag) {
@@ -191,8 +234,7 @@ int __wasilibc_add_file(filesystem_own_descriptor_t file_handle, int oflag) {
   }
   assert(file_handle.__handle != 0);
   file->file_handle = file_handle;
-  file->readable = oflag & O_RDONLY;
-  file->writable = oflag & O_WRONLY;
+  file->oflag = oflag;
 
   descriptor_table_entry_t entry;
   entry.vtable = &file_vtable;

libc-bottom-half/sources/wasip2_stdio.c

@@ -1,6 +1,7 @@
 #ifdef __wasilibc_use_wasip2
 
 #include <errno.h>
+#include <fcntl.h>
 #include <string.h>
 #include <wasi/descriptor_table.h>
 #include <wasi/stdio.h>
@@ -81,11 +82,21 @@ static int stdio_fstat(void *data, struct stat *buf) {
   return 0;
 }
 
+static int stdio_fcntl_getfl(void *data) {
+  stdio_t *stdio = (stdio_t *)data;
+  if (stdio->fd == 0) {
+    return O_RDONLY;
+  } else {
+    return O_WRONLY;
+  }
+}
+
 static descriptor_vtable_t stdio_vtable = {
   .free = stdio_free,
   .get_read_stream = stdio_get_read_stream,
   .get_write_stream = stdio_get_write_stream,
   .fstat = stdio_fstat,
+  .fcntl_getfl = stdio_fcntl_getfl,
 };
 
 static int stdio_add(int fd) {

test/CMakeLists.txt

@@ -275,6 +275,7 @@ add_wasilibc_test(fdatasync.c FS)
 add_wasilibc_test(fdopen.c FS)
 add_wasilibc_test(feof.c FS)
 add_wasilibc_test(file_permissions.c FS)
+add_wasilibc_test(file_nonblocking.c FS)
 add_wasilibc_test(fseek.c FS)
 add_wasilibc_test(fstat.c FS)
 add_wasilibc_test(fsync.c FS)

test/src/file_nonblocking.c

@@ -0,0 +1,63 @@
+#include <errno.h>
+#include <fcntl.h>
+#include <sys/ioctl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <sys/stat.h>
+#include "test.h"
+
+#define TEST(c) do { \
+	errno = 0; \
+	if (!(c)) \
+		t_error("%s failed (errno = %d)\n", #c, errno); \
+} while(0)
+
+int main(void)
+{
+	char tmp[] = "testsuite-XXXXXX";
+	int fd;
+        int enabled = 1;
+        int disabled = 0;
+
+	TEST((fd = open(tmp, O_RDWR | O_CREAT, 0600)) > 2);
+
+        // O_NONBLOCK
+        TEST(fcntl(fd, F_GETFL) == O_RDWR);
+        TEST(ioctl(fd, FIONBIO, &enabled) == 0);
+        TEST(fcntl(fd, F_GETFL) == (O_RDWR | O_NONBLOCK));
+        TEST(ioctl(fd, FIONBIO, &disabled) == 0);
+        TEST(fcntl(fd, F_GETFL) == O_RDWR);
+        TEST(fcntl(fd, F_SETFL, O_NONBLOCK) == 0);
+        TEST(fcntl(fd, F_GETFL) == (O_RDWR | O_NONBLOCK));
+        TEST(fcntl(fd, F_SETFL, 0) == 0);
+        TEST(fcntl(fd, F_GETFL) == O_RDWR);
+
+        // O_APPEND
+        TEST(fcntl(fd, F_SETFL, O_APPEND) == 0);
+        TEST(fcntl(fd, F_GETFL) == (O_RDWR | O_APPEND));
+        TEST(fcntl(fd, F_SETFL, O_APPEND | O_NONBLOCK) == 0);
+        TEST(fcntl(fd, F_GETFL) == (O_RDWR | O_APPEND | O_NONBLOCK));
+        TEST(fcntl(fd, F_SETFL, 0) == 0);
+        TEST(fcntl(fd, F_GETFL) == O_RDWR);
+
+        TEST(close(fd) == 0);
+
+        // stdio - not that wasmtime's implementation for wasip1-threads is
+        // broken so some tests are skipped there.
+        TEST(fcntl(0, F_GETFL) == O_RDONLY);
+#ifndef __wasm_atomics__
+        TEST(fcntl(1, F_GETFL) == O_WRONLY);
+        TEST(fcntl(2, F_GETFL) == O_WRONLY);
+#endif
+        TEST(fcntl(0, F_SETFL, O_APPEND) == -1);
+        TEST(fcntl(1, F_SETFL, O_APPEND) == -1);
+        TEST(fcntl(2, F_SETFL, O_APPEND) == -1);
+        TEST(fcntl(0, F_SETFL, O_NONBLOCK) == -1);
+        TEST(fcntl(1, F_SETFL, O_NONBLOCK) == -1);
+        TEST(fcntl(2, F_SETFL, O_NONBLOCK) == -1);
+
+	return t_status;
+}
+