Re: PATCH: Warning relocs against discarded functions

["H . J . Lu" <hjl at lucon dot org>]

On Thu, Nov 01, 2001 at 03:23:49PM -0800, Geoff Keating wrote:
> 
> > On Thu, Nov 01, 2001 at 11:43:10PM +1100, Keith Owens wrote:
> > > The problem is worse than stabs.  If a function is marked __exit _and_
> > > some code in another section refers to that function then :-
> > > 
> > > * ld resolves the reference as offset xxx from the start of section
> > >   .text.exit which is expected to get a decent start address.
> > > * Section .text.exit is discarded, giving it a zero start address.
> 
> That's not right!  When a section is discarded, it goes away, it
> doesn't go to location 0.  When a section is not in the final object,
> any non-weak relocations to it (that do make it to the final object)
> are an error, and should be reported as such ("undefined symbol" or
> similar).
> 

Here is the modified patch which handles weak references.


H.J.
---
2001-11-01  H.J. Lu  (hjl@gnu.org)

	* elflink.h (elf_link_input_bfd): Complain relocs against
	discarded sections.

Index: elflink.h
===================================================================
RCS file: /work/cvs/gnu/binutils/bfd/elflink.h,v
retrieving revision 1.88
diff -u -p -r1.88 elflink.h
--- elflink.h	2001/10/31 21:30:43	1.88
+++ elflink.h	2001/11/02 00:25:09
@@ -6079,6 +6079,7 @@ elf_link_input_bfd (finfo, input_bfd)
   asection *o;
   struct elf_backend_data *bed;
   boolean emit_relocs;
+  struct elf_link_hash_entry **sym_hashes;
 
   output_bfd = finfo->output_bfd;
   bed = get_elf_backend_data (output_bfd);
@@ -6251,6 +6252,7 @@ elf_link_input_bfd (finfo, input_bfd)
     }
 
   /* Relocate the contents of each section.  */
+  sym_hashes = elf_sym_hashes (input_bfd);
   for (o = input_bfd->sections; o != NULL; o = o->next)
     {
       bfd_byte *contents;
@@ -6298,26 +6300,59 @@ elf_link_input_bfd (finfo, input_bfd)
 	      && o->reloc_count > 0)
 	    return false;
 
-#if BFD_VERSION_DATE < 20031005
 	  {
 	    Elf_Internal_Rela *rel, *relend;
-	    /* Run through the relocs looking for any against section
-	       symbols from removed link-once sections.  Zero any such
-	       relocs.  We should really complain if anything in the
-	       final link tries to use it, but DWARF-based exception
-	       handling might have an entry in .eh_frame to describe a
-	       routine in the linkonce section, and it turns out to be
-	       hard to remove the .eh_frame entry too.  FIXME.  */
+	    /* Run through the relocs looking for any against symbols
+	       from discarded sections and section symbols from
+	       removed link-once sections. Complain about relocs
+	       against discarded sections. Zero relocs against removed
+	       link-once sections. We should really complain if
+	       anything in the final link tries to use it, but
+	       DWARF-based exception handling might have an entry in
+	       .eh_frame to describe a routine in the linkonce section,
+	       and it turns out to be hard to remove the .eh_frame
+	       entry too.  FIXME.  */
 	    rel = internal_relocs;
 	    relend = rel + o->reloc_count * bed->s->int_rels_per_ext_rel;
 	    for ( ; rel < relend; rel++)
 	      {
 		unsigned long r_symndx = ELF_R_SYM (rel->r_info);
 
-		if (r_symndx < locsymcount
-		    && (!elf_bad_symtab (input_bfd)
-			|| finfo->sections[r_symndx] != NULL))
+		if (r_symndx >= locsymcount
+		    || (elf_bad_symtab (input_bfd)
+			&& finfo->sections[r_symndx] == NULL))
 		  {
+		    struct elf_link_hash_entry *h;
+
+		    h = sym_hashes[r_symndx - symtab_hdr->sh_info];
+		    while (h->root.type == bfd_link_hash_indirect
+			   || h->root.type == bfd_link_hash_warning)
+		      h = (struct elf_link_hash_entry *) h->root.u.i.link;
+		    /* Complain if the definition comes from a
+		       discarded section.  */
+		    if ((h->root.type == bfd_link_hash_defined
+			 || h->root.type == bfd_link_hash_defweak)
+			&& h->root.u.def.section->output_section
+			   == bfd_abs_section_ptr)
+		      {
+			if ((h->elf_link_hash_flags
+			     & ELF_LINK_HASH_REF_REGULAR_NONWEAK) != 0)
+			  {
+			    if (! ((*finfo->info->callbacks->undefined_symbol)
+				    (finfo->info, h->root.root.string,
+				    input_bfd, o, rel->r_offset,
+				    true)))
+			      return false;
+			  }
+		        else
+			  {
+			    h->root.type = bfd_link_hash_undefweak;
+			  }
+		      }
+		  }
+#if BFD_VERSION_DATE < 20031005
+		else
+		  {
 		    isym = finfo->internal_syms + r_symndx;
 		    if (ELF_ST_TYPE (isym->st_info) == STT_SECTION)
 		      {
@@ -6337,11 +6372,11 @@ elf_link_input_bfd (finfo, input_bfd)
 			  }
 		      }
 		  }
-	      }
-	  }
 #else
 #error "gcc should be fixed by now, and this kludge no longer needed"
 #endif
+	      }
+	  }
 
 	  /* Relocate the section by invoking a back end routine.