Initial fchmodat support

Author: patricoferris

lib_eio/fs.ml

@@ -71,6 +71,7 @@ module Pi = struct
     val rename : t -> path -> _ dir -> path -> unit
     val read_link : t -> path -> string
     val symlink : link_to:path -> t -> path -> unit
+    val chmod : t -> follow:bool -> perm:File.Unix_perm.t -> path -> unit
     val pp : t Fmt.t
     val native : t -> string -> string option
   end

lib_eio/path.ml

@@ -218,6 +218,14 @@ let symlink ~link_to source =
     let bt = Printexc.get_raw_backtrace () in
     Exn.reraise_with_context ex bt "creating symlink %a -> %s" pp source link_to
 
+let chmod ~follow ~perm t =
+  let (Resource.T (dir, ops), path) = t in
+  let module X = (val (Resource.get ops Fs.Pi.Dir)) in
+  try X.chmod dir ~follow ~perm path
+  with Exn.Io _ as ex ->
+    let bt = Printexc.get_raw_backtrace () in
+    Exn.reraise_with_context ex bt "chmoding file %a" pp t
+
 let rec mkdirs ?(exists_ok=false) ~perm t =
   (* Check parent exists first. *)
   split t |> Option.iter (fun (parent, _) ->

lib_eio/path.mli

@@ -217,3 +217,8 @@ val symlink : link_to:string -> _ t -> unit
     {[
       Eio.Path.symlink (dir / "current") ~link_to:"version-1.0"
     ]} *)
+
+val chmod : follow:bool -> perm:int -> _ t -> unit
+(** [chmod ~follow ~perm t] allows you to change the file mode bits.
+
+    @param follow If [true] and [t] is a symlink then change the file mode bits target. *)

lib_eio_linux/eio_linux.ml

@@ -455,6 +455,9 @@ end = struct
   let symlink ~link_to t path =
     Low_level.symlink ~link_to t.fd path
 
+  let chmod t ~follow ~perm path =
+    Low_level.chmod t.fd ~follow ~mode:perm path
+
   let pp f t = Fmt.string f (String.escaped t.label)
 
   let fd t = t.fd

lib_eio_linux/eio_stubs.c

@@ -115,6 +115,20 @@ CAMLprim value caml_eio_symlinkat(value v_old_path, value v_new_fd, value v_new_
   CAMLreturn(Val_unit);
 }
 
+CAMLprim value caml_eio_fchmodat(value v_fd, value v_path, value v_mode, value v_flags) {
+  CAMLparam1(v_path);
+  char *path;
+  int ret;
+  caml_unix_check_path(v_path, "fchmodat");
+  path = caml_stat_strdup(String_val(v_path));
+  caml_enter_blocking_section();
+  ret = fchmodat(Int_val(v_fd), path, Int_val(v_mode), Int_val(v_flags));
+  caml_leave_blocking_section();
+  caml_stat_free(path);
+  if (ret == -1) uerror("fchmodat", v_path);
+  CAMLreturn(Val_unit);
+}
+
 CAMLprim value caml_eio_getrandom(value v_ba, value v_off, value v_len) {
   CAMLparam1(v_ba);
   ssize_t ret;

lib_eio_linux/low_level.ml

@@ -360,6 +360,8 @@ external eio_renameat : Unix.file_descr -> string -> Unix.file_descr -> string -
 
 external eio_symlinkat : string -> Unix.file_descr -> string -> unit = "caml_eio_symlinkat"
 
+external eio_fchmodat : Unix.file_descr -> string -> int -> int -> unit = "caml_eio_fchmodat"
+
 external eio_getrandom : Cstruct.buffer -> int -> int -> int = "caml_eio_getrandom"
 
 external eio_getdents : Unix.file_descr -> string list = "caml_eio_getdents"
@@ -486,6 +488,15 @@ let symlink ~link_to dir path =
     eio_symlinkat link_to parent leaf
   with Unix.Unix_error (code, name, arg) -> raise @@ Err.wrap_fs code name arg
 
+
+let chmod ~follow ~mode dir path =
+  let module X = Uring.Statx in
+  with_parent_dir "chmodat" dir path @@ fun parent leaf ->
+  let flags = if follow then 0 else (* at_symlink_nofollow *) 0x100 in
+  try
+    eio_fchmodat parent leaf mode flags
+  with Unix.Unix_error (code, name, arg) -> raise @@ Err.wrap_fs code name arg
+
 let shutdown socket command =
   try
     Fd.use_exn "shutdown" socket @@ fun fd ->

lib_eio_linux/low_level.mli

@@ -153,6 +153,9 @@ val rename : dir_fd -> string -> dir_fd -> string -> unit
 val symlink : link_to:string -> dir_fd -> string -> unit
 (** [symlink ~link_to dir path] creates a new symlink at [dir / path] pointing to [link_to]. *)
 
+val chmod : follow:bool -> mode:int -> dir_fd -> string -> unit
+(** [chmod ~follow ~mode dir path] changes the file mode bits of [dir / path]. *)
+
 val pipe : sw:Switch.t -> fd * fd
 (** [pipe ~sw] returns a pair [r, w] with the readable and writeable ends of a new pipe. *)
 

lib_eio_posix/eio_posix_stubs.c

@@ -405,6 +405,20 @@ CAMLprim value caml_eio_posix_symlinkat(value v_old_path, value v_new_fd, value
   CAMLreturn(Val_unit);
 }
 
+CAMLprim value caml_eio_posix_fchmodat(value v_fd, value v_path, value v_mode, value v_flags) {
+  CAMLparam1(v_path);
+  char *path;
+  int ret;
+  caml_unix_check_path(v_path, "fchmodat");
+  path = caml_stat_strdup(String_val(v_path));
+  caml_enter_blocking_section();
+  ret = fchmodat(Int_val(v_fd), path, Int_val(v_mode), Int_val(v_flags));
+  caml_leave_blocking_section();
+  caml_stat_free_preserving_errno(path);
+  if (ret == -1) uerror("fchmodat", v_path);
+  CAMLreturn(Val_unit);
+}
+
 CAMLprim value caml_eio_posix_spawn(value v_errors, value v_actions) {
   CAMLparam1(v_actions);
   pid_t child_pid;

lib_eio_posix/fs.ml

@@ -97,6 +97,9 @@ end = struct
   let symlink ~link_to t path =
     Err.run (Low_level.symlink ~link_to t.fd) path
 
+  let chmod t ~follow ~perm path =
+    Err.run (Low_level.chmod ~follow ~mode:perm t.fd) path
+
   let open_dir t ~sw path =
     let flags = Low_level.Open_flags.(rdonly + directory +? path) in
     let fd = Err.run (Low_level.openat ~sw ~mode:0 t.fd path) flags in

lib_eio_posix/low_level.ml

@@ -423,6 +423,15 @@ let symlink ~link_to new_dir new_path =
   let new_dir = Option.value new_dir ~default:at_fdcwd in
   eio_symlinkat link_to new_dir new_path
 
+external eio_fchmodat : Unix.file_descr -> string -> int -> int -> unit = "caml_eio_posix_fchmodat"
+
+let chmod ~follow ~mode dir path =
+  in_worker_thread "chmod" @@ fun () ->
+  Resolve.with_parent "chmod" dir path @@ fun dir path ->
+  let new_dir = Option.value dir ~default:at_fdcwd in
+  let flags = if follow then 0 else Config.at_symlink_nofollow in
+  eio_fchmodat new_dir path mode flags
+
 let read_link dirfd path =
   in_worker_thread "read_link" @@ fun () ->
   Resolve.with_parent "read_link" dirfd path @@ fun dirfd path ->