[PATCH v2 2/2] ld: Add --enable-mark-plt configure option

["H.J. Lu" <hjl.tools@gmail.com>]

Add --enable-mark-plt linker configure option to mark PLT entries with
DT_X86_64_PLT, DT_X86_64_PLTSZ and DT_X86_64_PLTENT dynamic tags by
default.

	* NEWS: Mention -z mark-plt/-z nomark-plt and --enable-mark-plt.
	* config.in: Regenerated.
	* configure: Likewise.
	* configure.ac: Add --enable-mark-plt.
	(DEFAULT_LD_Z_MARK_PLT): New AC_DEFINE_UNQUOTED.
	* emulparams/x86-64-plt.sh (PARSE_AND_LIST_OPTIONS_X86_64_PLT):
	Support DEFAULT_LD_Z_MARK_PLT.
	* emultempl/elf-x86.em (elf_x86_64_before_parse): New function.
	(LDEMUL_BEFORE_PARSE): New.  Set to elf_x86_64_before_parse for
	x86-64 targets.
---
 ld/NEWS                     |  5 +++++
 ld/config.in                |  4 ++++
 ld/configure                | 26 ++++++++++++++++++++++++--
 ld/configure.ac             | 17 +++++++++++++++++
 ld/emulparams/x86-64-plt.sh |  7 ++++++-
 ld/emultempl/elf-x86.em     | 17 +++++++++++++++++
 6 files changed, 73 insertions(+), 3 deletions(-)

diff --git a/ld/NEWS b/ld/NEWS
index a2c0b7fbcfe..cedd0d72d1b 100644
--- a/ld/NEWS
+++ b/ld/NEWS
@@ -1,5 +1,10 @@
 -*- text -*-
 
+* Add -z mark-plt/-z nomark-plt options to x86-64 ELF linker to mark PLT
+  entries with DT_X86_64_PLT, DT_X86_64_PLTSZ and DT_X86_64_PLTENT dynamic
+  tags.  Also added --enable-mark-plt configure option to mark PLT entries
+  by default.
+
 * Support Intel APX relocations.
 
 * On RISC-V, add ld target option --[no-]check-uleb128.  Should rebuild the
diff --git a/ld/config.in b/ld/config.in
index 86d90d53752..52d62f06ff0 100644
--- a/ld/config.in
+++ b/ld/config.in
@@ -45,6 +45,10 @@
    default. */
 #undef DEFAULT_LD_WARN_RWX_SEGMENTS
 
+/* Define to 1 if you want to enable -z mark-plt in ELF x86-64 linker by
+   default. */
+#undef DEFAULT_LD_Z_MARK_PLT
+
 /* Define to 1 if you want to enable -z relro in ELF linker by default. */
 #undef DEFAULT_LD_Z_RELRO
 
diff --git a/ld/configure b/ld/configure
index 07eb669d906..b7f29ca68b7 100755
--- a/ld/configure
+++ b/ld/configure
@@ -852,6 +852,7 @@ enable_new_dtags
 enable_relro
 enable_textrel_check
 enable_separate_code
+enable_mark_plt
 enable_warn_execstack
 enable_error_execstack
 enable_warn_rwx_segments
@@ -1546,6 +1547,7 @@ Optional Features:
   --enable-textrel-check=[yes|no|warning|error]
                           enable DT_TEXTREL check in ELF linker
   --enable-separate-code  enable -z separate-code in ELF linker by default
+  --enable-mark-plt       enable -z mark-plt in ELF x86-64 linker by default
   --enable-warn-execstack enable warnings when creating an executable stack
   --enable-error-execstack
                           turn executable stack warnings into errors
@@ -11681,7 +11683,7 @@ else
   lt_dlunknown=0; lt_dlno_uscore=1; lt_dlneed_uscore=2
   lt_status=$lt_dlunknown
   cat > conftest.$ac_ext <<_LT_EOF
-#line 11684 "configure"
+#line 11686 "configure"
 #include "confdefs.h"
 
 #if HAVE_DLFCN_H
@@ -11787,7 +11789,7 @@ else
   lt_dlunknown=0; lt_dlno_uscore=1; lt_dlneed_uscore=2
   lt_status=$lt_dlunknown
   cat > conftest.$ac_ext <<_LT_EOF
-#line 11790 "configure"
+#line 11792 "configure"
 #include "confdefs.h"
 
 #if HAVE_DLFCN_H
@@ -15682,6 +15684,17 @@ esac
 fi
 
 
+# Decide if -z mark-plt should be enabled in ELF x86-64 linker by default.
+ac_default_ld_z_mark_plt=unset
+# Check whether --enable-mark-plt was given.
+if test "${enable_mark_plt+set}" = set; then :
+  enableval=$enable_mark_plt; case "${enableval}" in
+  yes) ac_default_ld_z_mark_plt=1 ;;
+  no) ac_default_ld_z_mark_plt=0 ;;
+esac
+fi
+
+
 
 # By default warn when an executable stack is created due to object files
 # requesting such, not when the user specifies -z execstack.
@@ -19365,6 +19378,15 @@ cat >>confdefs.h <<_ACEOF
 _ACEOF
 
 
+if test "${ac_default_ld_z_mark_plt}" = unset; then
+  ac_default_ld_z_mark_plt=0
+fi
+
+cat >>confdefs.h <<_ACEOF
+#define DEFAULT_LD_Z_MARK_PLT $ac_default_ld_z_mark_plt
+_ACEOF
+
+
 
 
 cat >>confdefs.h <<_ACEOF
diff --git a/ld/configure.ac b/ld/configure.ac
index b46f415fe9b..4a11787ae71 100644
--- a/ld/configure.ac
+++ b/ld/configure.ac
@@ -213,6 +213,16 @@ AC_ARG_ENABLE(separate-code,
   no) ac_default_ld_z_separate_code=0 ;;
 esac])
 
+# Decide if -z mark-plt should be enabled in ELF x86-64 linker by default.
+ac_default_ld_z_mark_plt=unset
+AC_ARG_ENABLE(mark-plt,
+	      AS_HELP_STRING([--enable-mark-plt],
+	      [enable -z mark-plt in ELF x86-64 linker by default]),
+[case "${enableval}" in
+  yes) ac_default_ld_z_mark_plt=1 ;;
+  no) ac_default_ld_z_mark_plt=0 ;;
+esac])
+
 
 # By default warn when an executable stack is created due to object files
 # requesting such, not when the user specifies -z execstack.
@@ -562,6 +572,13 @@ AC_DEFINE_UNQUOTED(DEFAULT_LD_Z_SEPARATE_CODE,
   $ac_default_ld_z_separate_code,
   [Define to 1 if you want to enable -z separate-code in ELF linker by default.])
 
+if test "${ac_default_ld_z_mark_plt}" = unset; then
+  ac_default_ld_z_mark_plt=0
+fi
+AC_DEFINE_UNQUOTED(DEFAULT_LD_Z_MARK_PLT,
+  $ac_default_ld_z_mark_plt,
+  [Define to 1 if you want to enable -z mark-plt in ELF x86-64 linker by default.])
+
 
 AC_DEFINE_UNQUOTED(DEFAULT_LD_WARN_EXECSTACK,
   $ac_default_ld_warn_execstack,
diff --git a/ld/emulparams/x86-64-plt.sh b/ld/emulparams/x86-64-plt.sh
index 92732401dc7..d1a5c65937f 100644
--- a/ld/emulparams/x86-64-plt.sh
+++ b/ld/emulparams/x86-64-plt.sh
@@ -1,5 +1,10 @@
 PARSE_AND_LIST_OPTIONS_X86_64_PLT='
-  fprintf (file, _("\
+  if (DEFAULT_LD_Z_MARK_PLT != 0)
+    fprintf (file, _("\
+  -z mark-plt                 Mark PLT with dynamic tags (default)\n\
+  -z nomark-plt               Do not mark PLT with dynamic tags\n"));
+  else
+    fprintf (file, _("\
   -z mark-plt                 Mark PLT with dynamic tags\n\
   -z nomark-plt               Do not mark PLT with dynamic tags (default)\n"));
 '
diff --git a/ld/emultempl/elf-x86.em b/ld/emultempl/elf-x86.em
index 0ccad72ab9a..a6eda14253f 100644
--- a/ld/emultempl/elf-x86.em
+++ b/ld/emultempl/elf-x86.em
@@ -56,3 +56,20 @@ EOF
 
 LDEMUL_BEFORE_PARSE=elf_x86_before_parse
 fi
+
+case x${OUTPUT_FORMAT} in
+  x*x86-64*)
+fragment <<EOF
+
+static void
+elf_x86_64_before_parse (void)
+{
+  params.mark_plt = DEFAULT_LD_Z_MARK_PLT;
+
+  elf_x86_before_parse ();
+}
+EOF
+
+    LDEMUL_BEFORE_PARSE=elf_x86_64_before_parse
+    ;;
+esac
-- 
2.43.0