Add gold support for --package-metadata option.

Following the same format as the implementation in ld:
9e2bb0cb5e74aed4158f08495534922d7108f928

Generate a .note.package FDO package metadata ELF note, following
the spec: https://systemd.io/ELF_PACKAGE_METADATA/

If the jansson library is available at build time (and it is explicitly
enabled), link ld to it, and use it to validate that the input is
correct JSON, to avoid writing garbage to the file. The
configure option --enable-jansson has to be used to explicitly enable
it (error out when not found). This allows bootstrappers (or others who
are not interested) to seamlessly skip it without issues.

elfcpp/
	* elfcpp.h: Add FDO_PACKAGING_METADATA note type.

gold/
	* Makefile.am: Add jansson flags and libraries.
	* configure.ac: Check for jansson library.
	* layout.cc (Layout::create_notes): Call create_package_metadata().
	(Layout::create_package_metadata): New function.
	* layout.h (Layout::create_package_metadata): New function.
	(Layout::package_metadata_note_): New data member.
	* options.h (class General_options): Add --package-metadata option.
	* testsuite/Makefile.am (object_unittest): Add jansson libraries.
	(binary_unittest): Likewise.
	(leb128_unittest): Likewise.
	(overflow_unittest): Likewise.
	(package_metadata_test): New test.
	* testsuite/package_metadata_main.c: New test source.

13 files changed, 430 insertions, 26 deletions

diff --git a/elfcpp/elfcpp.h b/elfcpp/elfcpp.h
index 4b0aff0..3ca2d61 100644
--- a/elfcpp/elfcpp.h
+++ b/elfcpp/elfcpp.h
@@ -999,7 +999,9 @@ enum
   // string.
   NT_GNU_GOLD_VERSION = 4,
   // Program property note, as described in "Linux Extensions to the gABI".
-  NT_GNU_PROPERTY_TYPE_0 = 5
+  NT_GNU_PROPERTY_TYPE_0 = 5,
+  // FDO .note.package notes as defined on https://systemd.io/ELF_PACKAGE_METADATA/
+  FDO_PACKAGING_METADATA = 0xcafe1a7e
 };
 
 // The OS values which may appear in word 0 of a NT_GNU_ABI_TAG note.
diff --git a/gold/Makefile.am b/gold/Makefile.am
index 2e40671..934e366 100644
--- a/gold/Makefile.am
+++ b/gold/Makefile.am
@@ -35,7 +35,7 @@ THREADFLAGS = @PTHREAD_CFLAGS@
 THREADLIBS = @PTHREAD_LIBS@
 
 AM_CFLAGS = $(WARN_CFLAGS) $(LFS_CFLAGS) $(RANDOM_SEED_CFLAGS) $(ZLIBINC) $(THREADFLAGS)
-AM_CXXFLAGS = $(WARN_CXXFLAGS) $(LFS_CFLAGS) $(RANDOM_SEED_CFLAGS) $(ZLIBINC) $(THREADFLAGS)
+AM_CXXFLAGS = $(WARN_CXXFLAGS) $(LFS_CFLAGS) $(RANDOM_SEED_CFLAGS) $(ZLIBINC) $(THREADFLAGS) $(JANSSON_CFLAGS)
 AM_LDFLAGS = $(THREADFLAGS)
 
 AM_CPPFLAGS = \
@@ -187,7 +187,7 @@ libgold_a_LIBADD = $(LIBOBJS)
 sources_var = main.cc
 deps_var = $(TARGETOBJS) libgold.a $(LIBIBERTY) $(LIBINTL_DEP)
 ldadd_var = $(TARGETOBJS) libgold.a $(LIBIBERTY) $(GOLD_LDADD) $(LIBINTL) \
-	 $(THREADLIBS) $(LIBDL) $(ZLIB)
+	 $(THREADLIBS) $(LIBDL) $(ZLIB) $(JANSSON_LIBS)
 ldflags_var = $(GOLD_LDFLAGS)
 
 ld_new_SOURCES = $(sources_var)
@@ -201,12 +201,12 @@ incremental_dump_SOURCES = incremental-dump.cc
 incremental_dump_DEPENDENCIES = $(TARGETOBJS) libgold.a $(LIBIBERTY) \
 	$(LIBINTL_DEP)
 incremental_dump_LDADD = $(TARGETOBJS) libgold.a $(LIBIBERTY) $(LIBINTL) \
-	 $(THREADLIBS) $(LIBDL) $(ZLIB)
+	 $(THREADLIBS) $(LIBDL) $(ZLIB) $(JANSSON_LIBS)
 
 dwp_SOURCES = dwp.cc
 dwp_DEPENDENCIES = libgold.a $(LIBIBERTY) $(LIBINTL_DEP)
 dwp_LDADD = libgold.a $(LIBIBERTY) $(GOLD_LDADD) $(LIBINTL) $(THREADLIBS) \
-	$(LIBDL) $(ZLIB)
+	$(LIBDL) $(ZLIB) $(JANSSON_LIBS)
 dwp_LDFLAGS = $(GOLD_LDFLAGS)
 
 CONFIG_STATUS_DEPENDENCIES = $(srcdir)/../bfd/development.sh
diff --git a/gold/Makefile.in b/gold/Makefile.in
index 516eace..b7b7ad5 100644
--- a/gold/Makefile.in
+++ b/gold/Makefile.in
@@ -130,6 +130,7 @@ am__aclocal_m4_deps = $(top_srcdir)/../config/ax_pthread.m4 \
 	$(top_srcdir)/../config/lead-dot.m4 \
 	$(top_srcdir)/../config/nls.m4 \
 	$(top_srcdir)/../config/override.m4 \
+	$(top_srcdir)/../config/pkg.m4 \
 	$(top_srcdir)/../config/plugins.m4 \
 	$(top_srcdir)/../config/po.m4 \
 	$(top_srcdir)/../config/progtest.m4 \
@@ -193,7 +194,7 @@ ld_new_OBJECTS = $(am_ld_new_OBJECTS)
 am__DEPENDENCIES_2 = $(am__DEPENDENCIES_1) libgold.a $(LIBIBERTY) \
 	$(am__DEPENDENCIES_1) $(am__DEPENDENCIES_1) \
 	$(am__DEPENDENCIES_1) $(am__DEPENDENCIES_1) \
-	$(am__DEPENDENCIES_1)
+	$(am__DEPENDENCIES_1) $(am__DEPENDENCIES_1)
 ld_new_LINK = $(CXXLD) $(AM_CXXFLAGS) $(CXXFLAGS) $(ld_new_LDFLAGS) \
 	$(LDFLAGS) -o $@
 @GCC_TRUE@@NATIVE_LINKER_TRUE@am_ld1_OBJECTS = $(am__objects_4)
@@ -549,6 +550,8 @@ INSTALL_PROGRAM = @INSTALL_PROGRAM@
 INSTALL_SCRIPT = @INSTALL_SCRIPT@
 INSTALL_STRIP_PROGRAM = @INSTALL_STRIP_PROGRAM@
 INSTOBJEXT = @INSTOBJEXT@
+JANSSON_CFLAGS = @JANSSON_CFLAGS@
+JANSSON_LIBS = @JANSSON_LIBS@
 LDFLAGS = @LDFLAGS@
 LFS_CFLAGS = @LFS_CFLAGS@
 LIBINTL = @LIBINTL@
@@ -575,6 +578,9 @@ PACKAGE_TARNAME = @PACKAGE_TARNAME@
 PACKAGE_URL = @PACKAGE_URL@
 PACKAGE_VERSION = @PACKAGE_VERSION@
 PATH_SEPARATOR = @PATH_SEPARATOR@
+PKG_CONFIG = @PKG_CONFIG@
+PKG_CONFIG_LIBDIR = @PKG_CONFIG_LIBDIR@
+PKG_CONFIG_PATH = @PKG_CONFIG_PATH@
 POSUB = @POSUB@
 PTHREAD_CC = @PTHREAD_CC@
 PTHREAD_CFLAGS = @PTHREAD_CFLAGS@
@@ -668,7 +674,7 @@ ZLIBINC = @zlibinc@
 THREADFLAGS = @PTHREAD_CFLAGS@
 THREADLIBS = @PTHREAD_LIBS@
 AM_CFLAGS = $(WARN_CFLAGS) $(LFS_CFLAGS) $(RANDOM_SEED_CFLAGS) $(ZLIBINC) $(THREADFLAGS)
-AM_CXXFLAGS = $(WARN_CXXFLAGS) $(LFS_CFLAGS) $(RANDOM_SEED_CFLAGS) $(ZLIBINC) $(THREADFLAGS)
+AM_CXXFLAGS = $(WARN_CXXFLAGS) $(LFS_CFLAGS) $(RANDOM_SEED_CFLAGS) $(ZLIBINC) $(THREADFLAGS) $(JANSSON_CFLAGS)
 AM_LDFLAGS = $(THREADFLAGS)
 AM_CPPFLAGS = \
 	-I$(srcdir) -I$(srcdir)/../include -I$(srcdir)/../elfcpp \
@@ -805,7 +811,7 @@ libgold_a_LIBADD = $(LIBOBJS)
 sources_var = main.cc
 deps_var = $(TARGETOBJS) libgold.a $(LIBIBERTY) $(LIBINTL_DEP)
 ldadd_var = $(TARGETOBJS) libgold.a $(LIBIBERTY) $(GOLD_LDADD) $(LIBINTL) \
-	 $(THREADLIBS) $(LIBDL) $(ZLIB)
+	 $(THREADLIBS) $(LIBDL) $(ZLIB) $(JANSSON_LIBS)
 
 ldflags_var = $(GOLD_LDFLAGS)
 ld_new_SOURCES = $(sources_var)
@@ -818,12 +824,12 @@ incremental_dump_DEPENDENCIES = $(TARGETOBJS) libgold.a $(LIBIBERTY) \
 	$(LIBINTL_DEP)
 
 incremental_dump_LDADD = $(TARGETOBJS) libgold.a $(LIBIBERTY) $(LIBINTL) \
-	 $(THREADLIBS) $(LIBDL) $(ZLIB)
+	 $(THREADLIBS) $(LIBDL) $(ZLIB) $(JANSSON_LIBS)
 
 dwp_SOURCES = dwp.cc
 dwp_DEPENDENCIES = libgold.a $(LIBIBERTY) $(LIBINTL_DEP)
 dwp_LDADD = libgold.a $(LIBIBERTY) $(GOLD_LDADD) $(LIBINTL) $(THREADLIBS) \
-	$(LIBDL) $(ZLIB)
+	$(LIBDL) $(ZLIB) $(JANSSON_LIBS)
 
 dwp_LDFLAGS = $(GOLD_LDFLAGS)
 CONFIG_STATUS_DEPENDENCIES = $(srcdir)/../bfd/development.sh
diff --git a/gold/aclocal.m4 b/gold/aclocal.m4
index 303c4cc..6a0cd72 100644
--- a/gold/aclocal.m4
+++ b/gold/aclocal.m4
@@ -1203,6 +1203,7 @@ m4_include([../config/lcmessage.m4])
 m4_include([../config/lead-dot.m4])
 m4_include([../config/nls.m4])
 m4_include([../config/override.m4])
+m4_include([../config/pkg.m4])
 m4_include([../config/plugins.m4])
 m4_include([../config/po.m4])
 m4_include([../config/progtest.m4])
diff --git a/gold/config.in b/gold/config.in
index ca0b9d2..a2000d3 100644
--- a/gold/config.in
+++ b/gold/config.in
@@ -112,6 +112,9 @@
 /* Define to 1 if you have the <inttypes.h> header file. */
 #undef HAVE_INTTYPES_H
 
+/* The jansson library is to be used */
+#undef HAVE_JANSSON
+
 /* Define if your <locale.h> file defines LC_MESSAGES. */
 #undef HAVE_LC_MESSAGES
 
diff --git a/gold/configure b/gold/configure
index 5f5b8c3..84c413f 100755
--- a/gold/configure
+++ b/gold/configure
@@ -631,6 +631,11 @@ HAVE_NO_USE_LINKER_PLUGIN_FALSE
 HAVE_NO_USE_LINKER_PLUGIN_TRUE
 HAVE_PUBNAMES_FALSE
 HAVE_PUBNAMES_TRUE
+JANSSON_LIBS
+JANSSON_CFLAGS
+PKG_CONFIG_LIBDIR
+PKG_CONFIG_PATH
+PKG_CONFIG
 THREADS_FALSE
 THREADS_TRUE
 PTHREAD_CFLAGS
@@ -851,6 +856,7 @@ with_gold_ldflags
 with_gold_ldadd
 with_system_zlib
 enable_threads
+enable_jansson
 enable_maintainer_mode
 '
       ac_precious_vars='build_alias
@@ -867,6 +873,11 @@ CXXFLAGS
 CCC
 YACC
 YFLAGS
+PKG_CONFIG
+PKG_CONFIG_PATH
+PKG_CONFIG_LIBDIR
+JANSSON_CFLAGS
+JANSSON_LIBS
 CXXCPP'
 
 
@@ -1503,6 +1514,7 @@ Optional Features:
   --enable-werror         treat compile warnings as errors
   --enable-build-warnings enable build-time compiler warnings
   --enable-threads[=ARG]  multi-threaded linking [ARG={auto,yes,no}]
+  --enable-jansson        enable jansson [default=no]
   --enable-maintainer-mode
                           enable make rules and dependencies not useful (and
                           sometimes confusing) to the casual installer
@@ -1533,6 +1545,15 @@ Some influential environment variables:
   YFLAGS      The list of arguments that will be passed by default to $YACC.
               This script will default YFLAGS to the empty string to avoid a
               default value of `-d' given by some make applications.
+  PKG_CONFIG  path to pkg-config utility
+  PKG_CONFIG_PATH
+              directories to add to pkg-config's search path
+  PKG_CONFIG_LIBDIR
+              path overriding pkg-config's built-in search path
+  JANSSON_CFLAGS
+              C compiler flags for JANSSON, overriding pkg-config
+  JANSSON_LIBS
+              linker flags for JANSSON, overriding pkg-config
   CXXCPP      C++ preprocessor
 
 Use these variables to override the choices made by `configure' or to help
@@ -9575,6 +9596,251 @@ else
 fi
 
 
+# Used to validate --package-metadata= input. Disabled by default.
+# Check whether --enable-jansson was given.
+if test "${enable_jansson+set}" = set; then :
+  enableval=$enable_jansson; enable_jansson=$enableval
+else
+  enable_jansson="no"
+fi
+
+
+if test "x$enable_jansson" != "xno"; then
+
+
+
+
+
+
+
+if test "x$ac_cv_env_PKG_CONFIG_set" != "xset"; then
+	if test -n "$ac_tool_prefix"; then
+  # Extract the first word of "${ac_tool_prefix}pkg-config", so it can be a program name with args.
+set dummy ${ac_tool_prefix}pkg-config; ac_word=$2
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for $ac_word" >&5
+$as_echo_n "checking for $ac_word... " >&6; }
+if ${ac_cv_path_PKG_CONFIG+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  case $PKG_CONFIG in
+  [\\/]* | ?:[\\/]*)
+  ac_cv_path_PKG_CONFIG="$PKG_CONFIG" # Let the user override the test with a path.
+  ;;
+  *)
+  as_save_IFS=$IFS; IFS=$PATH_SEPARATOR
+for as_dir in $PATH
+do
+  IFS=$as_save_IFS
+  test -z "$as_dir" && as_dir=.
+    for ac_exec_ext in '' $ac_executable_extensions; do
+  if as_fn_executable_p "$as_dir/$ac_word$ac_exec_ext"; then
+    ac_cv_path_PKG_CONFIG="$as_dir/$ac_word$ac_exec_ext"
+    $as_echo "$as_me:${as_lineno-$LINENO}: found $as_dir/$ac_word$ac_exec_ext" >&5
+    break 2
+  fi
+done
+  done
+IFS=$as_save_IFS
+
+  ;;
+esac
+fi
+PKG_CONFIG=$ac_cv_path_PKG_CONFIG
+if test -n "$PKG_CONFIG"; then
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: $PKG_CONFIG" >&5
+$as_echo "$PKG_CONFIG" >&6; }
+else
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+fi
+
+
+fi
+if test -z "$ac_cv_path_PKG_CONFIG"; then
+  ac_pt_PKG_CONFIG=$PKG_CONFIG
+  # Extract the first word of "pkg-config", so it can be a program name with args.
+set dummy pkg-config; ac_word=$2
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for $ac_word" >&5
+$as_echo_n "checking for $ac_word... " >&6; }
+if ${ac_cv_path_ac_pt_PKG_CONFIG+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  case $ac_pt_PKG_CONFIG in
+  [\\/]* | ?:[\\/]*)
+  ac_cv_path_ac_pt_PKG_CONFIG="$ac_pt_PKG_CONFIG" # Let the user override the test with a path.
+  ;;
+  *)
+  as_save_IFS=$IFS; IFS=$PATH_SEPARATOR
+for as_dir in $PATH
+do
+  IFS=$as_save_IFS
+  test -z "$as_dir" && as_dir=.
+    for ac_exec_ext in '' $ac_executable_extensions; do
+  if as_fn_executable_p "$as_dir/$ac_word$ac_exec_ext"; then
+    ac_cv_path_ac_pt_PKG_CONFIG="$as_dir/$ac_word$ac_exec_ext"
+    $as_echo "$as_me:${as_lineno-$LINENO}: found $as_dir/$ac_word$ac_exec_ext" >&5
+    break 2
+  fi
+done
+  done
+IFS=$as_save_IFS
+
+  ;;
+esac
+fi
+ac_pt_PKG_CONFIG=$ac_cv_path_ac_pt_PKG_CONFIG
+if test -n "$ac_pt_PKG_CONFIG"; then
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_pt_PKG_CONFIG" >&5
+$as_echo "$ac_pt_PKG_CONFIG" >&6; }
+else
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+fi
+
+  if test "x$ac_pt_PKG_CONFIG" = x; then
+    PKG_CONFIG=""
+  else
+    case $cross_compiling:$ac_tool_warned in
+yes:)
+{ $as_echo "$as_me:${as_lineno-$LINENO}: WARNING: using cross tools not prefixed with host triplet" >&5
+$as_echo "$as_me: WARNING: using cross tools not prefixed with host triplet" >&2;}
+ac_tool_warned=yes ;;
+esac
+    PKG_CONFIG=$ac_pt_PKG_CONFIG
+  fi
+else
+  PKG_CONFIG="$ac_cv_path_PKG_CONFIG"
+fi
+
+fi
+if test -n "$PKG_CONFIG"; then
+	_pkg_min_version=0.9.0
+	{ $as_echo "$as_me:${as_lineno-$LINENO}: checking pkg-config is at least version $_pkg_min_version" >&5
+$as_echo_n "checking pkg-config is at least version $_pkg_min_version... " >&6; }
+	if $PKG_CONFIG --atleast-pkgconfig-version $_pkg_min_version; then
+		{ $as_echo "$as_me:${as_lineno-$LINENO}: result: yes" >&5
+$as_echo "yes" >&6; }
+	else
+		{ $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+		PKG_CONFIG=""
+	fi
+fi
+  if test -n "$PKG_CONFIG"; then :
+
+
+pkg_failed=no
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for jansson" >&5
+$as_echo_n "checking for jansson... " >&6; }
+
+if test -n "$JANSSON_CFLAGS"; then
+    pkg_cv_JANSSON_CFLAGS="$JANSSON_CFLAGS"
+ elif test -n "$PKG_CONFIG"; then
+    if test -n "$PKG_CONFIG" && \
+    { { $as_echo "$as_me:${as_lineno-$LINENO}: \$PKG_CONFIG --exists --print-errors \"jansson\""; } >&5
+  ($PKG_CONFIG --exists --print-errors "jansson") 2>&5
+  ac_status=$?
+  $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
+  test $ac_status = 0; }; then
+  pkg_cv_JANSSON_CFLAGS=`$PKG_CONFIG --cflags "jansson" 2>/dev/null`
+		      test "x$?" != "x0" && pkg_failed=yes
+else
+  pkg_failed=yes
+fi
+ else
+    pkg_failed=untried
+fi
+if test -n "$JANSSON_LIBS"; then
+    pkg_cv_JANSSON_LIBS="$JANSSON_LIBS"
+ elif test -n "$PKG_CONFIG"; then
+    if test -n "$PKG_CONFIG" && \
+    { { $as_echo "$as_me:${as_lineno-$LINENO}: \$PKG_CONFIG --exists --print-errors \"jansson\""; } >&5
+  ($PKG_CONFIG --exists --print-errors "jansson") 2>&5
+  ac_status=$?
+  $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
+  test $ac_status = 0; }; then
+  pkg_cv_JANSSON_LIBS=`$PKG_CONFIG --libs "jansson" 2>/dev/null`
+		      test "x$?" != "x0" && pkg_failed=yes
+else
+  pkg_failed=yes
+fi
+ else
+    pkg_failed=untried
+fi
+
+if test $pkg_failed = no; then
+  pkg_save_LDFLAGS="$LDFLAGS"
+  LDFLAGS="$LDFLAGS $pkg_cv_JANSSON_LIBS"
+  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+int
+main ()
+{
+
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_link "$LINENO"; then :
+
+else
+  pkg_failed=yes
+fi
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext conftest.$ac_ext
+  LDFLAGS=$pkg_save_LDFLAGS
+fi
+
+
+
+if test $pkg_failed = yes; then
+        { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+
+if $PKG_CONFIG --atleast-pkgconfig-version 0.20; then
+        _pkg_short_errors_supported=yes
+else
+        _pkg_short_errors_supported=no
+fi
+        if test $_pkg_short_errors_supported = yes; then
+	        JANSSON_PKG_ERRORS=`$PKG_CONFIG --short-errors --print-errors --cflags --libs "jansson" 2>&1`
+        else
+	        JANSSON_PKG_ERRORS=`$PKG_CONFIG --print-errors --cflags --libs "jansson" 2>&1`
+        fi
+	# Put the nasty error message in config.log where it belongs
+	echo "$JANSSON_PKG_ERRORS" >&5
+
+
+	  as_fn_error $? "Cannot find jansson library" "$LINENO" 5
+
+elif test $pkg_failed = untried; then
+        { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+
+	  as_fn_error $? "Cannot find jansson library" "$LINENO" 5
+
+else
+	JANSSON_CFLAGS=$pkg_cv_JANSSON_CFLAGS
+	JANSSON_LIBS=$pkg_cv_JANSSON_LIBS
+        { $as_echo "$as_me:${as_lineno-$LINENO}: result: yes" >&5
+$as_echo "yes" >&6; }
+
+
+$as_echo "#define HAVE_JANSSON 1" >>confdefs.h
+
+
+
+
+fi
+
+else
+
+      as_fn_error $? "Cannot find pkg-config" "$LINENO" 5
+
+fi
+fi
+
 ac_fn_c_check_decl "$LINENO" "basename" "ac_cv_have_decl_basename" "$ac_includes_default"
 if test "x$ac_cv_have_decl_basename" = xyes; then :
   ac_have_decl=1
diff --git a/gold/configure.ac b/gold/configure.ac
index 4f43280..25fae6b 100644
--- a/gold/configure.ac
+++ b/gold/configure.ac
@@ -591,6 +591,32 @@ if test "$threads" = "yes"; then
 fi
 AM_CONDITIONAL(THREADS, test "$threads" = "yes")
 
+# Used to validate --package-metadata= input. Disabled by default.
+AC_ARG_ENABLE([jansson],
+  [AS_HELP_STRING([--enable-jansson],
+    [enable jansson [default=no]])],
+  [enable_jansson=$enableval],
+  [enable_jansson="no"])
+
+if test "x$enable_jansson" != "xno"; then
+  PKG_PROG_PKG_CONFIG
+  AS_IF([test -n "$PKG_CONFIG"],
+    [
+      PKG_CHECK_MODULES(JANSSON, [jansson],
+	[
+	  AC_DEFINE(HAVE_JANSSON, 1, [The jansson library is to be used])
+	  AC_SUBST([JANSSON_CFLAGS])
+	  AC_SUBST([JANSSON_LIBS])
+	],
+	[
+	  AC_MSG_ERROR([Cannot find jansson library])
+	])
+    ],
+    [
+      AC_MSG_ERROR([Cannot find pkg-config])
+    ])
+fi
+
 dnl We have to check these in C, not C++, because autoconf generates
 dnl tests which have no type information, and current glibc provides
 dnl multiple declarations of functions like basename when compiling
diff --git a/gold/layout.cc b/gold/layout.cc
index 3efe8d9..184caa2 100644
--- a/gold/layout.cc
+++ b/gold/layout.cc
@@ -38,6 +38,9 @@
 #include <windows.h>
 #include <rpcdce.h>
 #endif
+#ifdef HAVE_JANSSON
+#include <jansson.h>
+#endif
 
 #include "parameters.h"
 #include "options.h"
@@ -2437,6 +2440,7 @@ Layout::create_notes()
   this->create_gold_note();
   this->create_stack_segment();
   this->create_build_id();
+  this->create_package_metadata();
 }
 
 // Create the dynamic sections which are needed before we read the
@@ -3534,6 +3538,52 @@ Layout::create_build_id()
     }
 }
 
+// If --package-metadata was used, set up the package metadata note.
+// https://systemd.io/ELF_PACKAGE_METADATA/
+
+void
+Layout::create_package_metadata()
+{
+  if (!parameters->options().user_set_package_metadata())
+    return;
+
+  const char* desc = parameters->options().package_metadata();
+  if (strcmp(desc, "") == 0)
+    return;
+
+#ifdef HAVE_JANSSON
+  json_error_t json_error;
+  json_t *json = json_loads(desc, 0, &json_error);
+  if (json)
+    json_decref(json);
+  else
+    {
+      gold_fatal(_("error: --package-metadata=%s does not contain valid "
+		   "JSON: %s\n"),
+		 desc, json_error.text);
+    }
+#endif
+
+  // Create the note.
+  size_t trailing_padding;
+  // Ensure the trailing NULL byte is always included, as per specification.
+  size_t descsz = strlen(desc) + 1;
+  Output_section* os = this->create_note("FDO", elfcpp::FDO_PACKAGING_METADATA,
+					 ".note.package", descsz, true,
+					 &trailing_padding);
+  if (os == NULL)
+    return;
+
+  Output_section_data* posd = new Output_data_const(desc, descsz, 4);
+  os->add_output_section_data(posd);
+
+  if (trailing_padding != 0)
+    {
+      posd = new Output_data_zero_fill(trailing_padding, 0);
+      os->add_output_section_data(posd);
+    }
+}
+
 // If we have both .stabXX and .stabXXstr sections, then the sh_link
 // field of the former should point to the latter.  I'm not sure who
 // started this, but the GNU linker does it, and some tools depend
diff --git a/gold/layout.h b/gold/layout.h
index 98c03b9..ee4f78c 100644
--- a/gold/layout.h
+++ b/gold/layout.h
@@ -1107,6 +1107,10 @@ class Layout
   void
   create_build_id();
 
+  // Create a package metadata note if needed.
+  void
+  create_package_metadata();
+
   // Link .stab and .stabstr sections.
   void
   link_stabs_sections();
@@ -1453,6 +1457,8 @@ class Layout
   Gdb_index* gdb_index_data_;
   // The space for the build ID checksum if there is one.
   Output_section_data* build_id_note_;
+  // The space for the package metadata JSON if there is one.
+  Output_section_data* package_metadata_note_;
   // The output section containing dwarf abbreviations
   Output_reduced_debug_abbrev_section* debug_abbrev_;
   // The output section containing the dwarf debug info tree
diff --git a/gold/options.h b/gold/options.h
index 9509a44..17236eb 100644
--- a/gold/options.h
+++ b/gold/options.h
@@ -1102,6 +1102,10 @@ class General_options
   DEFINE_bool(p, options::ONE_DASH, 'p', false,
 	      N_("Ignored for ARM compatibility"), NULL);
 
+  DEFINE_optional_string(package_metadata, options::TWO_DASHES, '\0', NULL,
+			 N_("Generate package metadata note"),
+			 N_("[=JSON]"));
+
   DEFINE_bool(pie, options::ONE_DASH, '\0', false,
 	      N_("Create a position independent executable"),
 	      N_("Do not create a position independent executable"));
diff --git a/gold/testsuite/Makefile.am b/gold/testsuite/Makefile.am
index 38e5481..b15000e 100644
--- a/gold/testsuite/Makefile.am
+++ b/gold/testsuite/Makefile.am
@@ -149,25 +149,25 @@ check_PROGRAMS += object_unittest
 object_unittest_SOURCES = object_unittest.cc
 object_unittest_LDFLAGS = $(THREADFLAGS)
 object_unittest_LDADD = libgoldtest.a ../libgold.a ../../libiberty/libiberty.a $(LIBINTL) \
-	$(THREADLIBS) $(LIBDL) $(ZLIB)
+	$(THREADLIBS) $(LIBDL) $(ZLIB) $(JANSSON_LIBS)
 
 check_PROGRAMS += binary_unittest
 binary_unittest_SOURCES = binary_unittest.cc
 binary_unittest_LDFLAGS = $(THREADFLAGS)
 binary_unittest_LDADD = libgoldtest.a ../libgold.a ../../libiberty/libiberty.a $(LIBINTL) \
-	$(THREADLIBS) $(LIBDL) $(ZLIB)
+	$(THREADLIBS) $(LIBDL) $(ZLIB) $(JANSSON_LIBS)
 
 check_PROGRAMS += leb128_unittest
 leb128_unittest_SOURCES = leb128_unittest.cc
 leb128_unittest_LDFLAGS = $(THREADFLAGS)
 leb128_unittest_LDADD = libgoldtest.a ../libgold.a ../../libiberty/libiberty.a $(LIBINTL) \
-	$(THREADLIBS) $(LIBDL) $(ZLIB)
+	$(THREADLIBS) $(LIBDL) $(ZLIB) $(JANSSON_LIBS)
 
 check_PROGRAMS += overflow_unittest
 overflow_unittest_SOURCES = overflow_unittest.cc
 overflow_unittest_LDFLAGS = $(THREADFLAGS)
 overflow_unittest_LDADD = libgoldtest.a ../libgold.a ../../libiberty/libiberty.a $(LIBINTL) \
-	$(THREADLIBS) $(LIBDL) $(ZLIB)
+	$(THREADLIBS) $(LIBDL) $(ZLIB) $(JANSSON_LIBS)
 overflow_unittest.o: overflow_unittest.cc
 	$(CXXCOMPILE) -O3 -c -o $@ $<
 
@@ -4435,3 +4435,10 @@ retain_2.o: retain_2.s
 	$(TEST_AS) -o $@ $<
 
 endif DEFAULT_TARGET_X86_64
+
+check_PROGRAMS += package_metadata_test
+package_metadata_test.o: package_metadata_main.c
+	$(COMPILE) -c -o $@ $<
+package_metadata_test$(EXEEXT): package_metadata_test.o gcctestdir/ld
+	$(CXXLINK) package_metadata_test.o -Wl,--package-metadata='{"foo":"bar"}'
+	$(TEST_READELF) --notes $@ | grep -q '{"foo":"bar"}'
diff --git a/gold/testsuite/Makefile.in b/gold/testsuite/Makefile.in
index 7b4b783..78bb0cc 100644
--- a/gold/testsuite/Makefile.in
+++ b/gold/testsuite/Makefile.in
@@ -109,7 +109,8 @@ check_PROGRAMS = $(am__EXEEXT_1) $(am__EXEEXT_2) $(am__EXEEXT_3) \
 	$(am__EXEEXT_37) $(am__EXEEXT_38) $(am__EXEEXT_39) \
 	$(am__EXEEXT_40) $(am__EXEEXT_41) $(am__EXEEXT_42) \
 	$(am__EXEEXT_43) $(am__EXEEXT_44) $(am__EXEEXT_45) \
-	$(am__EXEEXT_46) $(am__EXEEXT_47)
+	$(am__EXEEXT_46) $(am__EXEEXT_47) \
+	package_metadata_test$(EXEEXT)
 @NATIVE_OR_CROSS_LINKER_TRUE@am__append_1 = object_unittest \
 @NATIVE_OR_CROSS_LINKER_TRUE@	binary_unittest leb128_unittest \
 @NATIVE_OR_CROSS_LINKER_TRUE@	overflow_unittest
@@ -1146,6 +1147,7 @@ am__aclocal_m4_deps = $(top_srcdir)/../config/ax_pthread.m4 \
 	$(top_srcdir)/../config/lead-dot.m4 \
 	$(top_srcdir)/../config/nls.m4 \
 	$(top_srcdir)/../config/override.m4 \
+	$(top_srcdir)/../config/pkg.m4 \
 	$(top_srcdir)/../config/plugins.m4 \
 	$(top_srcdir)/../config/po.m4 \
 	$(top_srcdir)/../config/progtest.m4 \
@@ -1407,6 +1409,7 @@ am__DEPENDENCIES_1 =
 @NATIVE_OR_CROSS_LINKER_TRUE@	$(am__DEPENDENCIES_1) \
 @NATIVE_OR_CROSS_LINKER_TRUE@	$(am__DEPENDENCIES_1) \
 @NATIVE_OR_CROSS_LINKER_TRUE@	$(am__DEPENDENCIES_1) \
+@NATIVE_OR_CROSS_LINKER_TRUE@	$(am__DEPENDENCIES_1) \
 @NATIVE_OR_CROSS_LINKER_TRUE@	$(am__DEPENDENCIES_1)
 binary_unittest_LINK = $(CXXLD) $(AM_CXXFLAGS) $(CXXFLAGS) \
 	$(binary_unittest_LDFLAGS) $(LDFLAGS) -o $@
@@ -1732,6 +1735,7 @@ leb128_unittest_OBJECTS = $(am_leb128_unittest_OBJECTS)
 @NATIVE_OR_CROSS_LINKER_TRUE@	$(am__DEPENDENCIES_1) \
 @NATIVE_OR_CROSS_LINKER_TRUE@	$(am__DEPENDENCIES_1) \
 @NATIVE_OR_CROSS_LINKER_TRUE@	$(am__DEPENDENCIES_1) \
+@NATIVE_OR_CROSS_LINKER_TRUE@	$(am__DEPENDENCIES_1) \
 @NATIVE_OR_CROSS_LINKER_TRUE@	$(am__DEPENDENCIES_1)
 leb128_unittest_LINK = $(CXXLD) $(AM_CXXFLAGS) $(CXXFLAGS) \
 	$(leb128_unittest_LDFLAGS) $(LDFLAGS) -o $@
@@ -1755,6 +1759,7 @@ object_unittest_OBJECTS = $(am_object_unittest_OBJECTS)
 @NATIVE_OR_CROSS_LINKER_TRUE@	$(am__DEPENDENCIES_1) \
 @NATIVE_OR_CROSS_LINKER_TRUE@	$(am__DEPENDENCIES_1) \
 @NATIVE_OR_CROSS_LINKER_TRUE@	$(am__DEPENDENCIES_1) \
+@NATIVE_OR_CROSS_LINKER_TRUE@	$(am__DEPENDENCIES_1) \
 @NATIVE_OR_CROSS_LINKER_TRUE@	$(am__DEPENDENCIES_1)
 object_unittest_LINK = $(CXXLD) $(AM_CXXFLAGS) $(CXXFLAGS) \
 	$(object_unittest_LDFLAGS) $(LDFLAGS) -o $@
@@ -1767,9 +1772,13 @@ overflow_unittest_OBJECTS = $(am_overflow_unittest_OBJECTS)
 @NATIVE_OR_CROSS_LINKER_TRUE@	$(am__DEPENDENCIES_1) \
 @NATIVE_OR_CROSS_LINKER_TRUE@	$(am__DEPENDENCIES_1) \
 @NATIVE_OR_CROSS_LINKER_TRUE@	$(am__DEPENDENCIES_1) \
+@NATIVE_OR_CROSS_LINKER_TRUE@	$(am__DEPENDENCIES_1) \
 @NATIVE_OR_CROSS_LINKER_TRUE@	$(am__DEPENDENCIES_1)
 overflow_unittest_LINK = $(CXXLD) $(AM_CXXFLAGS) $(CXXFLAGS) \
 	$(overflow_unittest_LDFLAGS) $(LDFLAGS) -o $@
+package_metadata_test_SOURCES = package_metadata_test.c
+package_metadata_test_OBJECTS = package_metadata_test.$(OBJEXT)
+package_metadata_test_LDADD = $(LDADD)
 permission_test_SOURCES = permission_test.c
 permission_test_OBJECTS = permission_test.$(OBJEXT)
 permission_test_LDADD = $(LDADD)
@@ -2313,13 +2322,14 @@ SOURCES = $(libgoldtest_a_SOURCES) $(aarch64_pr23870_SOURCES) \
 	$(large_symbol_alignment_SOURCES) $(leb128_unittest_SOURCES) \
 	local_labels_test.c many_sections_r_test.c \
 	$(many_sections_test_SOURCES) $(object_unittest_SOURCES) \
-	$(overflow_unittest_SOURCES) permission_test.c \
-	$(pie_copyrelocs_test_SOURCES) plugin_test_1.c \
-	plugin_test_10.c plugin_test_11.c plugin_test_12.c \
-	plugin_test_2.c plugin_test_3.c plugin_test_4.c \
-	plugin_test_5.c plugin_test_6.c plugin_test_7.c \
-	plugin_test_8.c plugin_test_defsym.c plugin_test_start_lib.c \
-	plugin_test_tls.c plugin_test_wrap_symbols.c pr17704a_test.c \
+	$(overflow_unittest_SOURCES) package_metadata_test.c \
+	permission_test.c $(pie_copyrelocs_test_SOURCES) \
+	plugin_test_1.c plugin_test_10.c plugin_test_11.c \
+	plugin_test_12.c plugin_test_2.c plugin_test_3.c \
+	plugin_test_4.c plugin_test_5.c plugin_test_6.c \
+	plugin_test_7.c plugin_test_8.c plugin_test_defsym.c \
+	plugin_test_start_lib.c plugin_test_tls.c \
+	plugin_test_wrap_symbols.c pr17704a_test.c \
 	$(pr20216a_test_SOURCES) $(pr20216b_test_SOURCES) \
 	$(pr20216c_test_SOURCES) $(pr20216d_test_SOURCES) \
 	$(pr20216e_test_SOURCES) $(pr20308a_test_SOURCES) \
@@ -2635,6 +2645,8 @@ INSTALL_PROGRAM = @INSTALL_PROGRAM@
 INSTALL_SCRIPT = @INSTALL_SCRIPT@
 INSTALL_STRIP_PROGRAM = @INSTALL_STRIP_PROGRAM@
 INSTOBJEXT = @INSTOBJEXT@
+JANSSON_CFLAGS = @JANSSON_CFLAGS@
+JANSSON_LIBS = @JANSSON_LIBS@
 LDFLAGS = @LDFLAGS@
 LFS_CFLAGS = @LFS_CFLAGS@
 LIBINTL = @LIBINTL@
@@ -2661,6 +2673,9 @@ PACKAGE_TARNAME = @PACKAGE_TARNAME@
 PACKAGE_URL = @PACKAGE_URL@
 PACKAGE_VERSION = @PACKAGE_VERSION@
 PATH_SEPARATOR = @PATH_SEPARATOR@
+PKG_CONFIG = @PKG_CONFIG@
+PKG_CONFIG_LIBDIR = @PKG_CONFIG_LIBDIR@
+PKG_CONFIG_PATH = @PKG_CONFIG_PATH@
 POSUB = @POSUB@
 PTHREAD_CC = @PTHREAD_CC@
 PTHREAD_CFLAGS = @PTHREAD_CFLAGS@
@@ -2866,22 +2881,22 @@ DEPENDENCIES = \
 @NATIVE_OR_CROSS_LINKER_TRUE@object_unittest_SOURCES = object_unittest.cc
 @NATIVE_OR_CROSS_LINKER_TRUE@object_unittest_LDFLAGS = $(THREADFLAGS)
 @NATIVE_OR_CROSS_LINKER_TRUE@object_unittest_LDADD = libgoldtest.a ../libgold.a ../../libiberty/libiberty.a $(LIBINTL) \
-@NATIVE_OR_CROSS_LINKER_TRUE@	$(THREADLIBS) $(LIBDL) $(ZLIB)
+@NATIVE_OR_CROSS_LINKER_TRUE@	$(THREADLIBS) $(LIBDL) $(ZLIB) $(JANSSON_LIBS)
 
 @NATIVE_OR_CROSS_LINKER_TRUE@binary_unittest_SOURCES = binary_unittest.cc
 @NATIVE_OR_CROSS_LINKER_TRUE@binary_unittest_LDFLAGS = $(THREADFLAGS)
 @NATIVE_OR_CROSS_LINKER_TRUE@binary_unittest_LDADD = libgoldtest.a ../libgold.a ../../libiberty/libiberty.a $(LIBINTL) \
-@NATIVE_OR_CROSS_LINKER_TRUE@	$(THREADLIBS) $(LIBDL) $(ZLIB)
+@NATIVE_OR_CROSS_LINKER_TRUE@	$(THREADLIBS) $(LIBDL) $(ZLIB) $(JANSSON_LIBS)
 
 @NATIVE_OR_CROSS_LINKER_TRUE@leb128_unittest_SOURCES = leb128_unittest.cc
 @NATIVE_OR_CROSS_LINKER_TRUE@leb128_unittest_LDFLAGS = $(THREADFLAGS)
 @NATIVE_OR_CROSS_LINKER_TRUE@leb128_unittest_LDADD = libgoldtest.a ../libgold.a ../../libiberty/libiberty.a $(LIBINTL) \
-@NATIVE_OR_CROSS_LINKER_TRUE@	$(THREADLIBS) $(LIBDL) $(ZLIB)
+@NATIVE_OR_CROSS_LINKER_TRUE@	$(THREADLIBS) $(LIBDL) $(ZLIB) $(JANSSON_LIBS)
 
 @NATIVE_OR_CROSS_LINKER_TRUE@overflow_unittest_SOURCES = overflow_unittest.cc
 @NATIVE_OR_CROSS_LINKER_TRUE@overflow_unittest_LDFLAGS = $(THREADFLAGS)
 @NATIVE_OR_CROSS_LINKER_TRUE@overflow_unittest_LDADD = libgoldtest.a ../libgold.a ../../libiberty/libiberty.a $(LIBINTL) \
-@NATIVE_OR_CROSS_LINKER_TRUE@	$(THREADLIBS) $(LIBDL) $(ZLIB)
+@NATIVE_OR_CROSS_LINKER_TRUE@	$(THREADLIBS) $(LIBDL) $(ZLIB) $(JANSSON_LIBS)
 
 @GCC_TRUE@@NATIVE_LINKER_TRUE@large_symbol_alignment_SOURCES = large_symbol_alignment.cc
 @GCC_TRUE@@NATIVE_LINKER_TRUE@large_symbol_alignment_DEPENDENCIES = gcctestdir/ld
@@ -4828,6 +4843,7 @@ distclean-compile:
 @AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/many_sections_test.Po@am__quote@
 @AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/object_unittest.Po@am__quote@
 @AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/overflow_unittest.Po@am__quote@
+@AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/package_metadata_test.Po@am__quote@
 @AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/permission_test.Po@am__quote@
 @AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/pie_copyrelocs_test-pie_copyrelocs_test.Po@am__quote@
 @AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/plugin_test_1.Po@am__quote@
@@ -7775,6 +7791,13 @@ aarch64_pr23870.log: aarch64_pr23870$(EXEEXT)
 	--log-file $$b.log --trs-file $$b.trs \
 	$(am__common_driver_flags) $(AM_LOG_DRIVER_FLAGS) $(LOG_DRIVER_FLAGS) -- $(LOG_COMPILE) \
 	"$$tst" $(AM_TESTS_FD_REDIRECT)
+package_metadata_test.log: package_metadata_test$(EXEEXT)
+	@p='package_metadata_test$(EXEEXT)'; \
+	b='package_metadata_test'; \
+	$(am__check_pre) $(LOG_DRIVER) --test-name "$$f" \
+	--log-file $$b.log --trs-file $$b.trs \
+	$(am__common_driver_flags) $(AM_LOG_DRIVER_FLAGS) $(LOG_DRIVER_FLAGS) -- $(LOG_COMPILE) \
+	"$$tst" $(AM_TESTS_FD_REDIRECT)
 .test.log:
 	@p='$<'; \
 	$(am__set_b); \
@@ -10414,6 +10437,11 @@ uninstall-am:
 @DEFAULT_TARGET_X86_64_TRUE@	../ld-new -pie -e _start --gc-sections -o $@  retain_2.o
 @DEFAULT_TARGET_X86_64_TRUE@retain_2.o: retain_2.s
 @DEFAULT_TARGET_X86_64_TRUE@	$(TEST_AS) -o $@ $<
+package_metadata_test.o: package_metadata_main.c
+	$(COMPILE) -c -o $@ $<
+package_metadata_test$(EXEEXT): package_metadata_test.o gcctestdir/ld
+	$(CXXLINK) package_metadata_test.o -Wl,--package-metadata='{"foo":"bar"}'
+	$(TEST_READELF) --notes $@ | grep -q '{"foo":"bar"}'
 
 # Tell versions [3.59,3.63) of GNU make to not export all variables.
 # Otherwise a system limit (for SysV at least) may be exceeded.
diff --git a/gold/testsuite/package_metadata_main.c b/gold/testsuite/package_metadata_main.c
new file mode 100644
index 0000000..77bc677
--- /dev/null
+++ b/gold/testsuite/package_metadata_main.c
@@ -0,0 +1,5 @@
+int
+main(void)
+{
+  return 0;
+}