daemon: build also without Hivex.OPEN_UNSAFE (RHBZ#1493048)

Do a configure check for the OPEN_UNSAFE flag in the OCaml binding of
Hivex, using it only when available.  This makes it possible to use
hivex < 1.3.14 to build libguestfs (the daemon, actually).

Amend the building documentation accordingly, bringing the minimum
version of hivex back as it was before
commit 64f49df747.

.gitignore

@@ -186,6 +186,7 @@ Makefile.in
 /daemon/actions.h
 /daemon/callbacks.ml
 /daemon/caml-stubs.c
+/daemon/daemon_config.ml
 /daemon/daemon_utils_tests
 /daemon/dispatch.c
 /daemon/guestfsd

configure.ac

@@ -247,6 +247,7 @@ AC_CONFIG_FILES([Makefile
                  common/windows/Makefile
                  csharp/Makefile
                  customize/Makefile
+                 daemon/daemon_config.ml
                  daemon/Makefile
                  df/Makefile
                  dib/Makefile

daemon/Makefile.am

@@ -251,6 +251,7 @@ SOURCES_MLI = \
 	callbacks.mli \
 	chroot.mli \
 	daemon.mli \
+	daemon_config.mli \
 	devsparts.mli \
 	file.mli \
 	filearch.mli \
@@ -279,6 +280,7 @@ SOURCES_MLI = \
 	utils.mli
 
 SOURCES_ML = \
+	daemon_config.ml \
 	utils.ml \
 	structs.ml \
 	optgroups.ml \

daemon/daemon_config.ml.in

@@ -0,0 +1,20 @@
+(* guestfsd
+ * @configure_input@
+ * Copyright (C) 2018 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.
+ *)
+
+let hivex_flag_unsafe = @HIVEX_OPEN_UNSAFE_FLAG@

daemon/daemon_config.mli

@@ -0,0 +1,19 @@
+(* guestfsd
+ * Copyright (C) 2018 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.
+ *)
+
+val hivex_flag_unsafe : Hivex.open_flag option

daemon/inspect_utils.ml

@@ -176,7 +176,11 @@ let parse_version_from_major_minor str data =
   )
 
 let with_hive hive_filename f =
-  let flags = [ Hivex.OPEN_UNSAFE ] in
+  let flags = [] in
+  let flags =
+    match Daemon_config.hivex_flag_unsafe with
+    | None -> flags
+    | Some f -> f :: flags in
   let flags = if verbose () then Hivex.OPEN_VERBOSE :: flags else flags in
   let h = Hivex.open_file hive_filename flags in
   protect ~f:(fun () -> f h (Hivex.root h)) ~finally:(fun () -> Hivex.close h)

docs/guestfs-building.pod

@@ -178,7 +178,7 @@ I<Required>.
 I<Required> if compiling from git.
 Optional if compiling from tarball.
 
-=item hivex E<ge> 1.3.14
+=item hivex E<ge> 1.2.7
 
 =item ocaml-hivex
 

m4/guestfs-ocaml.m4

@@ -79,6 +79,7 @@ else
 fi
 AC_SUBST([OCAMLDEP_ONE_LINE])
 
+have_Hivex_OPEN_UNSAFE=no
 if test "x$enable_daemon" = "xyes"; then
     OCAML_PKG_hivex=no
     AC_CHECK_OCAML_PKG(hivex)
@@ -86,6 +87,18 @@ if test "x$enable_daemon" = "xyes"; then
         AC_MSG_ERROR([the OCaml module 'hivex' is required])
     fi
 
+    # Check if Hivex has 'OPEN_UNSAFE' flag.
+    AC_MSG_CHECKING([for Hivex.OPEN_UNSAFE])
+    rm -f conftest.ml
+    echo 'let s = Hivex.OPEN_UNSAFE' > conftest.ml
+    if $OCAMLFIND ocamlc -package hivex -c conftest.ml >&5 2>&5 ; then
+        AC_MSG_RESULT([yes])
+        have_Hivex_OPEN_UNSAFE=yes
+    else
+        AC_MSG_RESULT([no])
+        have_Hivex_OPEN_UNSAFE=no
+    fi
+
     dnl Check which OCaml runtime to link the daemon again.
     dnl We can't use AC_CHECK_LIB here unfortunately because
     dnl the other symbols are resolved by OCaml itself.
@@ -182,6 +195,12 @@ AC_SUBST([OCAML_BYTES_COMPAT_CMO])
 AC_SUBST([OCAML_BYTES_COMPAT_ML])
 AM_CONDITIONAL([HAVE_BYTES_COMPAT_ML],
 	       [test "x$OCAML_BYTES_COMPAT_ML" != "x"])
+AS_IF([test "x$have_Hivex_OPEN_UNSAFE" = "xno"],[
+    HIVEX_OPEN_UNSAFE_FLAG="None"
+],[
+    HIVEX_OPEN_UNSAFE_FLAG="Some Hivex.OPEN_UNSAFE"
+])
+AC_SUBST([HIVEX_OPEN_UNSAFE_FLAG])
 
 dnl Flags we want to pass to every OCaml compiler call.
 OCAML_WARN_ERROR="-warn-error CDEFLMPSUVYZX+52-3"