Make fstat work on file descriptors with no name part 1

This fixes fstat on "anonymous" file descriptors in node rawfs and
includes the changes to library_syscall and library_fs needed to
allow pipes emscripten-core#23306 and nodefs descriptors emscripten-core#23058 to be stated.

Author: hoodmane

src/library_fs.js

@@ -479,6 +479,24 @@ FS.staticInit();
       stream.stream_ops?.dup?.(stream);
       return stream;
     },
+    streamGetAttr(stream) {
+      var node = stream.node;
+      var res = stream.stream_ops?.getattr?.(stream) ?? node.node_ops?.getattr?.(node);
+      if (res) {
+        return res;
+      }
+      throw new FS.ErrnoError({{{ cDefs.EPERM }}});
+    },
+    streamSetAttr(stream, attr) {
+      var node = stream.node;
+      var set;
+      if (set = stream.stream_ops.setattr) {
+        return set(stream, attr);
+      } else if (set = node.node_ops.setattr) {
+        return set(node, attr);
+      }
+      throw new FS.ErrnoError({{{ cDefs.EPERM }}});
+    },
 
     //
     // devices
@@ -956,6 +974,10 @@ FS.staticInit();
       }
       return node.node_ops.getattr(node);
     },
+    fstat(fd) {
+      var stream = FS.getStreamChecked(fd);
+      return FS.streamGetAttr(stream);
+    },
     lstat(path) {
       return FS.stat(path, true);
     },
@@ -981,7 +1003,10 @@ FS.staticInit();
     },
     fchmod(fd, mode) {
       var stream = FS.getStreamChecked(fd);
-      FS.chmod(stream.node, mode);
+      FS.streamSetAttr(stream, {
+        mode: (mode & {{{ cDefs.S_IALLUGO }}}) | (stream.node.mode & ~{{{ cDefs.S_IALLUGO }}}),
+        ctime: Date.now()
+      });
     },
     chown(path, uid, gid, dontFollow) {
       var node;
@@ -1005,7 +1030,22 @@ FS.staticInit();
     },
     fchown(fd, uid, gid) {
       var stream = FS.getStreamChecked(fd);
-      FS.chown(stream.node, uid, gid);
+      FS.streamSetAttr(stream, {
+        timestamp: Date.now()
+        // we ignore the uid / gid for now
+      });
+    },
+    truncateChecks(node) {
+      if (FS.isDir(node.mode)) {
+        throw new FS.ErrnoError({{{ cDefs.EISDIR }}});
+      }
+      if (!FS.isFile(node.mode)) {
+        throw new FS.ErrnoError({{{ cDefs.EINVAL }}});
+      }
+      var errCode = FS.nodePermissions(node, 'w');
+      if (errCode) {
+        throw new FS.ErrnoError(errCode);
+      }
     },
     truncate(path, len) {
       if (len < 0) {
@@ -1018,30 +1058,21 @@ FS.staticInit();
       } else {
         node = path;
       }
-      if (!node.node_ops.setattr) {
-        throw new FS.ErrnoError({{{ cDefs.EPERM }}});
-      }
-      if (FS.isDir(node.mode)) {
-        throw new FS.ErrnoError({{{ cDefs.EISDIR }}});
-      }
-      if (!FS.isFile(node.mode)) {
-        throw new FS.ErrnoError({{{ cDefs.EINVAL }}});
-      }
-      var errCode = FS.nodePermissions(node, 'w');
-      if (errCode) {
-        throw new FS.ErrnoError(errCode);
-      }
       node.node_ops.setattr(node, {
         size: len,
         timestamp: Date.now()
       });
     },
     ftruncate(fd, len) {
       var stream = FS.getStreamChecked(fd);
-      if ((stream.flags & {{{ cDefs.O_ACCMODE }}}) === {{{ cDefs.O_RDONLY}}}) {
+      if (len < 0 || (stream.flags & {{{ cDefs.O_ACCMODE }}}) === {{{ cDefs.O_RDONLY}}}) {
         throw new FS.ErrnoError({{{ cDefs.EINVAL }}});
       }
-      FS.truncate(stream.node, len);
+      FS.truncateChecks(stream.node);
+      FS.streamSetAttr(stream, {
+        size: len,
+        timestamp: Date.now()
+      });
     },
     utime(path, atime, mtime) {
       var lookup = FS.lookupPath(path, { follow: true });

src/library_noderawfs.js

@@ -79,6 +79,10 @@ addToLibrary({
       }
       return stat;
     },
+    fstat(fd) {
+      var stream = FS.getStreamChecked(fd);
+      return fs.fstatSync(stream.nfd);
+    },
     chmod(path, mode, dontFollow) {
       mode &= {{{ cDefs.S_IALLUGO }}};
       if (NODEFS.isWindows) {

src/library_syscall.js

@@ -678,8 +678,7 @@ var SyscallsLibrary = {
     return SYSCALLS.writeStat(buf, FS.lstat(path));
   },
   __syscall_fstat64: (fd, buf) => {
-    var stream = SYSCALLS.getStreamFromFD(fd);
-    return SYSCALLS.writeStat(buf, FS.stat(stream.path));
+    return SYSCALLS.writeStat(buf, FS.fstat(fd));
   },
   __syscall_fchown32: (fd, owner, group) => {
     FS.fchown(fd, owner, group);

test/fs/test_stat_unnamed_file_descriptor.c

@@ -0,0 +1,20 @@
+#include <fcntl.h>
+#include <unistd.h>
+#include <sys/stat.h>
+#include <assert.h>
+#include "stdio.h"
+
+int main() {
+  int fd = open("file.txt", O_RDWR | O_CREAT, 0666);
+  unlink("file.txt");
+  int res;
+  struct stat buf;
+  res = fstat(fd, &buf);
+  assert(res == 0);
+  assert(buf.st_atime > 1000000000);
+  res = fchmod(fd, 0777);
+  assert(res == 0);
+  res = ftruncate(fd, 10);
+  assert(res == 0);
+  printf("success\n");
+}

test/test_core.py

@@ -5847,6 +5847,16 @@ def test_fs_64bit(self):
       self.set_setting('FORCE_FILESYSTEM')
     self.do_runf('fs/test_64bit.c', 'success')
 
+  @crossplatform
+  @also_with_noderawfs
+  def test_fs_stat_unnamed_file_descriptor(self):
+    nodefs = '-DNODEFS' in self.emcc_args or '-DNODERAWFS' in self.emcc_args
+    if self.get_setting('WASMFS'):
+      if nodefs:
+        self.skipTest('NODEFS in WasmFS')
+      self.set_setting('FORCE_FILESYSTEM')
+    self.do_runf('fs/test_stat_unnamed_file_descriptor.c', 'success')
+
   @requires_node
   @crossplatform
   @with_all_fs