[PATCH] Add --execstack and --noexecstack options to gas

[Jakub Jelinek <jakub at redhat dot com>]

Hi!

Now that GCC can mark all compiled code with execstack/noexecstack,
there is a problem with .S files which would need to be marked by hand.
I think it is far better to add a gas option which creates the note
automatically, so .S files don't have to be tweaked.
This can be also useful if say some .c file is known to require executable
stack for something other than GCC trampolines, one can use -Wa,--execstack
to compile it and override the default GCC guess that the .o file
does not need executable stack.

I don't know if it is ok to do this in generic code, or if I should instead
duplicate it for all the ELF backends which need it (i386, x86_64, ppc32,
alpha, s390, s390x, m68k at least).

2003-06-04  Jakub Jelinek  <jakub@redhat.com>

	* as.c (show_usage): Document --execstack and --noexecstack.
	(parse_args): Add --execstack and --noexecstack.
	(main): Create .note.GNU-stack section if --execstack or
	--noexecstack was given on comand line, set its SHF_EXECINSTR bit.
	* as.h (flag_execstack, flag_noexecstack): New.

--- gas/as.c.jj	2003-05-30 09:44:26.000000000 -0400
+++ gas/as.c	2003-06-04 07:43:05.000000000 -0400
@@ -268,6 +268,12 @@ Options:\n\
                           emulate output (default %s)\n"), def_em);
   }
 #endif
+#if defined BFD_ASSEMBLER && (defined OBJ_ELF || defined OBJ_MAYBE_ELF)
+  fprintf (stream, _("\
+  --execstack             require executable stack for this object\n"));
+  fprintf (stream, _("\
+  --noexecstack           don't require executable stack for this object\n"));
+#endif
   fprintf (stream, _("\
   -f                      skip whitespace and comment preprocessing\n"));
   fprintf (stream, _("\
@@ -437,7 +443,13 @@ parse_args (pargc, pargv)
     {"warn", no_argument, NULL, OPTION_WARN},
 #define OPTION_TARGET_HELP (OPTION_STD_BASE + 19)
     {"target-help", no_argument, NULL, OPTION_TARGET_HELP},
-#define OPTION_WARN_FATAL (OPTION_STD_BASE + 20)
+#if defined BFD_ASSEMBLER && (defined OBJ_ELF || defined OBJ_MAYBE_ELF)
+#define OPTION_EXECSTACK (OPTION_STD_BASE + 20)
+    {"execstack", no_argument, NULL, OPTION_EXECSTACK},
+#define OPTION_NOEXECSTACK (OPTION_STD_BASE + 21)
+    {"noexecstack", no_argument, NULL, OPTION_NOEXECSTACK},
+#endif
+#define OPTION_WARN_FATAL (OPTION_STD_BASE + 22)
     {"fatal-warnings", no_argument, NULL, OPTION_WARN_FATAL}
     /* When you add options here, check that they do not collide with
        OPTION_MD_BASE.  See as.h.  */
@@ -698,6 +710,18 @@ the GNU General Public License.  This pr
 	  flag_fatal_warnings = 1;
 	  break;
 
+#if defined BFD_ASSEMBLER && (defined OBJ_ELF || defined OBJ_MAYBE_ELF)
+	case OPTION_EXECSTACK:
+	  flag_execstack = 1;
+	  flag_noexecstack = 0;
+	  break;
+
+	case OPTION_NOEXECSTACK:
+	  flag_noexecstack = 1;
+	  flag_execstack = 0;
+	  break;
+#endif
+
 	case 'Z':
 	  flag_always_generate_output = 1;
 	  break;
@@ -907,6 +931,19 @@ main (argc, argv)
   md_end ();
 #endif
 
+#if defined BFD_ASSEMBLER && (defined OBJ_ELF || defined OBJ_MAYBE_ELF)
+  if ((flag_execstack || flag_noexecstack)
+      && OUTPUT_FLAVOR == bfd_target_elf_flavour)
+    {
+      segT gnustack;
+
+      gnustack = subseg_new (".note.GNU-stack", 0);
+      bfd_set_section_flags (stdoutput, gnustack,
+			     SEC_READONLY | (flag_execstack ? SEC_CODE : 0));
+                                                                             
+    }
+#endif
+
   /* If we've been collecting dwarf2 .debug_line info, either for
      assembly debugging or on behalf of the compiler, emit it now.  */
   dwarf2_finish ();
--- gas/as.h.jj	2003-05-23 09:24:40.000000000 -0400
+++ gas/as.h	2003-06-04 05:17:39.000000000 -0400
@@ -436,6 +436,12 @@ COMMON int flag_strip_local_absolute;
 /* True if we should generate a traditional format object file.  */
 COMMON int flag_traditional_format;
 
+/* TRUE if .note.GNU-stack section with SEC_CODE should be created */
+COMMON int flag_execstack;
+
+/* TRUE if .note.GNU-stack section with SEC_CODE should be created */
+COMMON int flag_noexecstack;
+
 /* name of emitted object file */
 COMMON char *out_file_name;
 

	Jakub