[Libguestfs] [PATCH 02/27] daemon: Allow parts of the daemon and APIs to be written in OCaml.
Pino Toscano
ptoscano at redhat.com
Wed Jul 19 13:13:47 UTC 2017
On Friday, 14 July 2017 15:39:10 CEST Richard W.M. Jones wrote:
> .gitignore | 6 +-
> Makefile.am | 2 +-
> common/mlutils/Makefile.am | 4 -
> daemon/Makefile.am | 103 +++++++++++++++++++++++--
> daemon/chroot.ml | 85 +++++++++++++++++++++
> daemon/chroot.mli | 35 +++++++++
> daemon/daemon-c.c | 35 +++++++++
> daemon/daemon.ml | 39 ++++++++++
> daemon/guestfsd.c | 50 ++++++++++++
> daemon/sysroot-c.c | 37 +++++++++
> daemon/sysroot.ml | 19 +++++
> daemon/sysroot.mli | 22 ++++++
> daemon/utils.ml | 156 +++++++++++++++++++++++++++++++++++++
> daemon/utils.mli | 65 ++++++++++++++++
TBH I'd just have a single "Daemon" module for the OCaml helpers for
the daemon, instead of different modules, wirh a single -c.c file for
all the C implementations. The Sysroot submodule could be implemented
like the various submodules in Unix_utils.
> diff --git a/daemon/Makefile.am b/daemon/Makefile.am
> index eedf09d52..40b770762 100644
> --- a/daemon/Makefile.am
> +++ b/daemon/Makefile.am
> @@ -19,6 +19,7 @@ include $(top_srcdir)/subdir-rules.mk
>
> generator_built = \
> actions.h \
> + caml-stubs.c \
> dispatch.c \
> names.c \
> lvm-tokenization.c \
> @@ -31,13 +32,30 @@ generator_built = \
> stubs-4.c \
> stubs-5.c \
> stubs-6.c \
> - stubs.h
> + stubs.h \
> + callbacks.ml \
> + types.ml
>
> BUILT_SOURCES = \
> - $(generator_built)
> + actions.h \
> + caml-stubs.c \
> + dispatch.c \
> + names.c \
> + lvm-tokenization.c \
> + structs-cleanups.c \
> + structs-cleanups.h \
> + stubs-0.c \
> + stubs-1.c \
> + stubs-2.c \
> + stubs-3.c \
> + stubs-4.c \
> + stubs-5.c \
> + stubs-6.c \
> + stubs.h
Hm why the duplication here? I mean, I see generator_built has
callbacks.ml, and types.ml -- could it be possible to add a new
variable? (or use BUILT_SOURCES in generator_built, maybe)
> +OCAML_LIBS = \
> + -lmlcutils \
> + -lmlstdutils \
> + -lmlhivex \
> + -lcamlstr \
> + -lunix \
> + -l$(CAMLRUN) -ldl -lm
Are ld and m needed?
> diff --git a/daemon/chroot.mli b/daemon/chroot.mli
> new file mode 100644
> index 000000000..eda3a785f
> --- /dev/null
> +++ b/daemon/chroot.mli
> @@ -0,0 +1,35 @@
> +(* guestfs-inspection
> + * Copyright (C) 2009-2017 Red Hat Inc.
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation; either version 2 of the License, or
> + * (at your option) any later version.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
> + * GNU General Public License for more details.
> + *
> + * You should have received a copy of the GNU General Public License along
> + * with this program; if not, write to the Free Software Foundation, Inc.,
> + * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
> + *)
> +
> +(** This is a generic module for running functions in a chroot.
> + The function runs in a forked subprocess too so that we can
> + restore the root afterwards.
> +
> + It handles passing the parmeter, forking, running the
typo, "parameter"
> + function and marshalling the result or any exceptions. *)
> +
> +type t
> +
> +val create : ?name:string -> string -> t
> +(** Create a chroot handle. [?name] is an optional name used in
> + debugging and error messages. The string is the chroot
> + directory. *)
> +
> +val f : t -> ('a -> 'b) -> 'a -> 'b
> +(** Run a function in the chroot, returning the result or re-raising
> + any exception thrown. *)
After reading patch #11, IMHO there should be a variant that takes a
generic (unit -> unit) function (called 'fn', maybe?), and have 'f'
use it:
let f t fun arg =
f (fun () -> fun arg)
> diff --git a/daemon/guestfsd.c b/daemon/guestfsd.c
> index b3f40628b..1d35991b6 100644
> --- a/daemon/guestfsd.c
> +++ b/daemon/guestfsd.c
> @@ -56,6 +56,10 @@
>
> #include <augeas.h>
>
> +#include <caml/callback.h>
> +#include <caml/mlvalues.h>
> +#include <caml/unixsupport.h>
> +
> #include "sockets.h"
> #include "c-ctype.h"
> #include "ignore-value.h"
> @@ -348,6 +352,9 @@ main (int argc, char *argv[])
> */
> udev_settle ();
>
> + /* Initialize the OCaml stubs. */
> + caml_startup (argv);
> +
> /* Send the magic length message which indicates that
> * userspace is up inside the guest.
> */
> @@ -1205,3 +1212,46 @@ cleanup_free_mountable (mountable_t *mountable)
> free (mountable->volume);
> }
> }
> +
> +/* Convert an OCaml exception to a reply_with_error_errno call
> + * as best we can.
> + */
> +extern void ocaml_exn_to_reply_with_error (const char *func, value exn);
> +
> +void
> +ocaml_exn_to_reply_with_error (const char *func, value exn)
> +{
Shouldn't this use CAMLparam1 + CAMLreturn?
> diff --git a/daemon/sysroot-c.c b/daemon/sysroot-c.c
> new file mode 100644
> index 000000000..ad31d36ee
> --- /dev/null
> +++ b/daemon/sysroot-c.c
> @@ -0,0 +1,37 @@
> +/* guestfs-inspection
> + * Copyright (C) 2017 Red Hat Inc.
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation; either version 2 of the License, or
> + * (at your option) any later version.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
> + * GNU General Public License for more details.
> + *
> + * You should have received a copy of the GNU General Public License
> + * along with this program; if not, write to the Free Software
> + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
> + */
> +
> +#include <config.h>
> +
> +#include <stdio.h>
> +#include <stdlib.h>
> +
> +#include <caml/alloc.h>
> +#include <caml/fail.h>
> +#include <caml/memory.h>
> +#include <caml/mlvalues.h>
> +
> +#include "daemon.h"
> +
> +extern value guestfs_int_daemon_sysroot (value unitv);
> +
> +value
> +guestfs_int_daemon_sysroot (value unitv)
> +{
Ditto.
> diff --git a/daemon/utils.ml b/daemon/utils.ml
> new file mode 100644
> index 000000000..7630a5534
> --- /dev/null
> +++ b/daemon/utils.ml
> @@ -0,0 +1,156 @@
> +(* guestfs-inspection
> + * Copyright (C) 2009-2017 Red Hat Inc.
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation; either version 2 of the License, or
> + * (at your option) any later version.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
> + * GNU General Public License for more details.
> + *
> + * You should have received a copy of the GNU General Public License along
> + * with this program; if not, write to the Free Software Foundation, Inc.,
> + * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
> + *)
> +
> +open Unix
> +open Printf
> +
> +open Std_utils
> +
> +let prog_exists prog =
> + try ignore (which prog); true
> + with Executable_not_found _ -> false
> +
> +let commandr prog args =
Another option here, instead of the manual implementation, would be to
bind the C command* APIs -- this way there is no need to do fixes &
additions in both places.
> + if verbose () then
> + eprintf "command: %s %s\n%!"
> + prog (String.concat " " args);
stringify_args could help here.
> + let argv = Array.of_list (prog :: args) in
> +
> + let stdout_file, stdout_chan = Filename.open_temp_file "cmd" ".out" in
> + let stderr_file, stderr_chan = Filename.open_temp_file "cmd" ".err" in
> + let stdout_fd = descr_of_out_channel stdout_chan in
> + let stderr_fd = descr_of_out_channel stderr_chan in
> + let stdin_fd = openfile "/dev/null" [O_RDONLY] 0 in
> +
> + let pid = fork () in
> + if pid = 0 then (
> + (* Child process. *)
> + dup2 stdin_fd stdin;
> + close stdin_fd;
> + dup2 stdout_fd stdout;
> + close stdout_fd;
> + dup2 stderr_fd stderr;
> + close stderr_fd;
> +
> + execvp prog argv
> + );
> +
> + (* Parent process. *)
> + close stdin_fd;
> + close stdout_fd;
> + close stderr_fd;
> + let _, status = waitpid [] pid in
> + let r =
> + match status with
> + | WEXITED i -> i
> + | WSIGNALED i ->
> + failwithf "external command ‘%s’ killed by signal %d" prog i
> + | WSTOPPED i ->
> + failwithf "external command ‘%s’ stopped by signal %d" prog i in
> +
> + if verbose () then
> + eprintf "command: %s returned %d\n" prog r;
> +
> + let stdout = read_whole_file stdout_file in
> + let stderr = read_whole_file stderr_file in
> +
> + if verbose () then (
> + if stdout <> "" then (
> + eprintf "command: %s: stdout:\n%s%!" prog stdout;
> + if not (String.is_suffix stdout "\n") then eprintf "\n%!"
> + );
> + if stderr <> "" then (
> + eprintf "command: %s: stderr:\n%s%!" prog stderr;
> + if not (String.is_suffix stderr "\n") then eprintf "\n%!"
> + )
> + );
> +
> + (* Strip trailing \n from stderr but NOT from stdout. *)
> + let stderr =
> + let n = String.length stderr in
> + if n > 0 && stderr.[n-1] = '\n' then
> + String.sub stderr 0 (n-1)
> + else
> + stderr in
This bit is already done in v2v/linux_bootloaders.ml, get_default_image
helper function; can you please move that to a chop function in
Std_utils? Most probably it could be used in Common_utils.uuidgen as
well.
(Also, funny thing is that, while grepping for that, I noticed the C
equivalent is written in many places, all around daemon, library, and
tools...)
> +
> + (r, stdout, stderr)
> +
> +let command prog args =
> + let r, stdout, stderr = commandr prog args in
> + if r <> 0 then
> + failwithf "%s exited with status %d: %s" prog r stderr;
> + stdout
> +
> +let udev_settle ?filename () =
Ditto.
> + let args = ref [] in
> + if verbose () then
> + push_back args "--debug";
> + push_back args "settle";
> + (match filename with
> + | None -> ()
> + | Some filename ->
> + push_back args "-E";
> + push_back args filename
> + );
> + let args = !args in
> + let r, _, err = commandr "udevadm" args in
> + if r <> 0 then
> + eprintf "udevadm settle: %s\n" err
> +
> +let root_device = lazy ((stat "/").st_dev)
> +
> +let is_root_device_stat statbuf =
> + statbuf.st_rdev = Lazy.force root_device
> +
> +let is_root_device device =
> + udev_settle ~filename:device ();
> + try
> + let statbuf = stat device in
> + is_root_device_stat statbuf
> + with
> + Unix_error (err, func, arg) ->
> + eprintf "is_root_device: %s: %s: %s: %s\n"
> + device func arg (error_message err);
> + false
> +
> +let proc_unmangle_path path =
> + let n = String.length path in
> + let b = Buffer.create n in
> + let rec loop i =
> + if i < n-3 && path.[i] = '\\' then (
> + let to_int c = Char.code c - Char.code '0' in
> + let v =
> + (to_int path.[i+1] lsl 6) lor
> + (to_int path.[i+2] lsl 3) lor
> + to_int path.[i+3] in
> + Buffer.add_char b (Char.chr v);
> + loop (i+4)
> + )
> + else if i < n then (
> + Buffer.add_char b path.[i];
> + loop (i+1)
> + )
> + else
> + Buffer.contents b
> + in
> + loop 0
> +
> +let is_small_file path =
> + is_regular_file path &&
> + (stat path).st_size <= 2 * 1048 * 1024
There could be an helper function sysroot_path, to mimick the C
function with the same name, and simplify code like
let mp = Sysroot.sysroot () // mountpoint in
into
let mp = sysroot_path mountpoint in
--
Pino Toscano
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