PATCH: Warn alternate ELF machine code

["H.J. Lu" <hongjiu dot lu at intel dot com>]

This patch adds an option, --warn-alternate-em, to issue a warning if
an object has alternate ELF machine code.  The default is off. OK for
trunk?

Thanks.


H.J.
---
bfd/

2009-04-07  H.J. Lu  <hongjiu.lu@intel.com>

	* elflink.c (elf_link_add_object_symbols): Warn alternate ELF
	machine code.

include/

2009-04-07  H.J. Lu  <hongjiu.lu@intel.com>

	* bfdlink.h (bfd_link_info): Add warn_alternate_em.
ld/

2009-04-07  H.J. Lu  <hongjiu.lu@intel.com>

	* lexsup.c (option_values): Add OPTION_WARN_ALTERNATE_EM.
	(ld_options): Likewise.
	(parse_args): Likewise.

	* ld.texinfo: Document --warn-alternate-em.

	* NEWS: Mention --warn-alternate-em.

Index: ld/lexsup.c
===================================================================
--- ld/lexsup.c	(revision 5628)
+++ ld/lexsup.c	(working copy)
@@ -163,6 +163,7 @@ enum option_values
   OPTION_WARN_UNRESOLVED_SYMBOLS,
   OPTION_ERROR_UNRESOLVED_SYMBOLS,
   OPTION_WARN_SHARED_TEXTREL,
+  OPTION_WARN_ALTERNATE_EM,
   OPTION_REDUCE_MEMORY_OVERHEADS,
   OPTION_DEFAULT_SCRIPT
 };
@@ -555,6 +556,9 @@ static const struct ld_option ld_options
   { {"warn-shared-textrel", no_argument, NULL, OPTION_WARN_SHARED_TEXTREL},
     '\0', NULL, N_("Warn if shared object has DT_TEXTREL"),
     TWO_DASHES },
+  { {"warn-alternate-em", no_argument, NULL, OPTION_WARN_ALTERNATE_EM},
+    '\0', NULL, N_("Warn if an object has alternate ELF machine code"),
+    TWO_DASHES },
   { {"warn-unresolved-symbols", no_argument, NULL,
      OPTION_WARN_UNRESOLVED_SYMBOLS},
     '\0', NULL, N_("Report unresolved symbols as warnings"), TWO_DASHES },
@@ -1359,6 +1363,9 @@ parse_args (unsigned argc, char **argv)
 	case OPTION_WARN_SHARED_TEXTREL:
 	  link_info.warn_shared_textrel = TRUE;
 	  break;
+	case OPTION_WARN_ALTERNATE_EM:
+	  link_info.warn_alternate_em = TRUE;
+	  break;
 	case OPTION_WHOLE_ARCHIVE:
 	  whole_archive = TRUE;
 	  break;
Index: ld/NEWS
===================================================================
--- ld/NEWS	(revision 5628)
+++ ld/NEWS	(working copy)
@@ -1,5 +1,8 @@
 -*- text -*-
 
+* ELF: --warn-alternate-em option to warn if an object has alternate
+  ELF machine code.
+
 * New script function REGION_ALIAS to add alias names to memory regions.
 
 * PE targets no longer make use of the long section names PE extension to
Index: ld/ld.texinfo
===================================================================
--- ld/ld.texinfo	(revision 5628)
+++ ld/ld.texinfo	(working copy)
@@ -1935,6 +1935,10 @@ the section (@pxref{SECTIONS}).
 @item --warn-shared-textrel
 Warn if the linker adds a DT_TEXTREL to a shared object.
 
+@kindex --warn-alternate-em
+@item --warn-alternate-em
+Warn if an object has alternate ELF machine code.
+
 @kindex --warn-unresolved-symbols
 @item --warn-unresolved-symbols
 If the linker is going to report an unresolved symbol (see the option
Index: include/bfdlink.h
===================================================================
--- include/bfdlink.h	(revision 5628)
+++ include/bfdlink.h	(working copy)
@@ -322,6 +322,9 @@ struct bfd_link_info
   /* TRUE if we should warn when adding a DT_TEXTREL to a shared object.  */
   unsigned int warn_shared_textrel: 1;
 
+  /* TRUE if we should warn alternate ELF machine code.  */
+  unsigned int warn_alternate_em: 1;
+
   /* TRUE if unreferenced sections should be removed.  */
   unsigned int gc_sections: 1;
 
Index: bfd/elflink.c
===================================================================
--- bfd/elflink.c	(revision 5628)
+++ bfd/elflink.c	(working copy)
@@ -3425,6 +3425,7 @@ _bfd_elf_relocs_compatible (const bfd_ta
 static bfd_boolean
 elf_link_add_object_symbols (bfd *abfd, struct bfd_link_info *info)
 {
+  Elf_Internal_Ehdr *ehdr;
   Elf_Internal_Shdr *hdr;
   bfd_size_type symcount;
   bfd_size_type extsymcount;
@@ -3480,6 +3481,17 @@ elf_link_add_object_symbols (bfd *abfd, 
 	}
     }
 
+  ehdr = elf_elfheader (abfd);
+  if (info->warn_alternate_em
+      && bed->elf_machine_code != ehdr->e_machine
+      && ((bed->elf_machine_alt1 != 0
+	   && ehdr->e_machine == bed->elf_machine_alt1)
+	  || (bed->elf_machine_alt2 != 0
+	      && ehdr->e_machine == bed->elf_machine_alt2)))
+    info->callbacks->einfo
+      (_("%P: warning: alternate ELF machine code (%d): %B\n"),
+       ehdr->e_machine, abfd);
+
   /* As a GNU extension, any input sections which are named
      .gnu.warning.SYMBOL are treated as warning symbols for the given
      symbol.  This differs from .gnu.warning sections, which generate