inotify, faccessat2, fsync for Linux programs, and D-Bus credentials

What installing and starting Epiphany ran into:

- inotify: inotify_init/init1, add_watch, rm_watch, as a new kind of event
  descriptor. The filesystem reports creates, deletes, renames (with a
  cookie pairing MOVED_FROM and MOVED_TO), writes, close-after-write,
  truncation and attribute changes, to watches on the inode and on its
  directory with the name. ONESHOT, MASK_ADD, MASK_CREATE, ONLYDIR,
  DONT_FOLLOW, IGNORED on removal, Q_OVERFLOW, and Linux's coalescing of
  repeated events. The hooks cost one load when nothing is watched. Without
  it GLib found no file monitor and GNOME programs aborted.
- FIONREAD on inotify descriptors and pipes (inotifywait sizes its buffer
  by it).
- fsync and fdatasync had no Linux numbers since the first commit: GLib's
  atomic writes, gtk-update-icon-cache and dbus-uuidgen all got ENOSYS.
- faccessat2, the flags-taking faccessat musl uses for any flags.
- sendmsg accepts SCM_CREDENTIALS when they are the sender's own, as Linux
  checks; GDBus sends them in every handshake and was refused with EINVAL.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01S1giNvrHTrPMPw7V6x1kQ4

kernel/sys/table.inc

@@ -213,8 +213,11 @@ SYSCALL(127,         92, chown)
 SYSCALL(128,         93, fchown)
 SYSCALL(129,         94, lchown)
 SYSCALL(130,         84, rmdir)
-SYSCALL(131,   NO_LINUX, fsync)
-SYSCALL(132,   NO_LINUX, fdatasync)
+// fsync and fdatasync had no Linux numbers from the first commit on, and
+// every Linux program that saves a file carefully got ENOSYS: GLib's atomic
+// file writes, gtk-update-icon-cache, dbus-uuidgen, apk's triggers.
+SYSCALL(131,         74, fsync)
+SYSCALL(132,         75, fdatasync)
 SYSCALL(133,        162, sync)
 SYSCALL(134,         17, pread)
 SYSCALL(135,         18, pwrite)
@@ -300,6 +303,11 @@ SYSCALL(207,         51, getsockname)
 SYSCALL(208,         52, getpeername)
 SYSCALL(209,        125, capget)
 SYSCALL(210,        126, capset)
+SYSCALL(211,        439, faccessat2)
+SYSCALL(212,        253, inotify_init)
+SYSCALL(213,        294, inotify_init1)
+SYSCALL(214,        254, inotify_add_watch)
+SYSCALL(215,        255, inotify_rm_watch)
 
 // --- mounts ---
 SYSCALL(185,        165, mount)