RE: Compact EH Support

["Moore, Catherine" <Catherine_Moore at mentor dot com>]

> -----Original Message-----
> From: Alan Modra [mailto:amodra@gmail.com]
> Sent: Friday, August 26, 2016 1:58 AM
> To: Moore, Catherine <Catherine_Moore@mentor.com>;
> bschmidt@redhat.com; paul@nowt.org
> Cc: binutils@sourceware.org
> Subject: Re: Compact EH Support
> 
> Re https://sourceware.org/ml/binutils/2015-05/msg00237.html
> 
> Would the person responsible for _bfd_elf_section_for_symbol please
> add a comment describing what the function does, in particular why it
> is looking for symbols defined in discarded sections.  It doesn't make
> much sense to me..
> 
> Please also move the function to elf-eh-frame.c and make it static.
> 
> --
> Alan Modra
> Australia Development Lab, IBM

The intent with the addition of _bfd_elf_section_for_symbol was to pull common code from bfd_reloc_symbol_deleted_p and bfd_elf_parse_eh_frame_entry.
This patch adds the comment and updates bfd_reloc_symbol_deleted_p to call _bfd_section_for_symbol.
OK to push?

2016-09-02  Catherine Moore  <clm@codesourcery.com>

        * elflink.c ( _bfd_elf_section_for_symbol): Add comment.
        Merge discard criteria from bfd_elf_reloc_symbol_deleted_p.
        (bfd_elf_reloc_symbol_deleted_p): Delete common code. Call
        _bfd_section_for_symbol.

diff --git a/bfd/elflink.c b/bfd/elflink.c
index 9e9a33c..00603be 100644
--- a/bfd/elflink.c
+++ b/bfd/elflink.c
@@ -58,6 +58,11 @@ struct elf_find_verdep_info
 static bfd_boolean _bfd_elf_fix_symbol_flags
   (struct elf_link_hash_entry *, struct elf_info_failed *);

+/*  Given a relocation cookie and its symndx, return the section
+    that defines the symbol or NULL if the symbol is not defined.
+    When DISCARD is true, a local symbol that has been defined in
+    a discarded section will be treated as an undefined symbol.  */
+
 asection *
 _bfd_elf_section_for_symbol (struct elf_reloc_cookie *cookie,
                             unsigned long r_symndx,
@@ -92,8 +97,10 @@ _bfd_elf_section_for_symbol (struct elf_reloc_cookie *cookie,
       /* Need to: get the symbol; get the section.  */
       isym = &cookie->locsyms[r_symndx];
       isec = bfd_section_from_elf_index (cookie->abfd, isym->st_shndx);
-      if (isec != NULL
-         && discard ? discarded_section (isec) : 1)
+
+      if (!discard
+         || (isec != NULL
+             && (isec->kept_section != NULL || discarded_section (isec))))
        return isec;
      }
   return NULL;
@@ -13509,40 +13516,8 @@ bfd_elf_reloc_symbol_deleted_p (bfd_vma offset, void *cookie)
       if (r_symndx == STN_UNDEF)
        return TRUE;

-      if (r_symndx >= rcookie->locsymcount
-         || ELF_ST_BIND (rcookie->locsyms[r_symndx].st_info) != STB_LOCAL)
-       {
-         struct elf_link_hash_entry *h;
-
-         h = rcookie->sym_hashes[r_symndx - rcookie->extsymoff];
-
-         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;
-
-         if ((h->root.type == bfd_link_hash_defined
-              || h->root.type == bfd_link_hash_defweak)
-             && (h->root.u.def.section->owner != rcookie->abfd
-                 || h->root.u.def.section->kept_section != NULL
-                 || discarded_section (h->root.u.def.section)))
-           return TRUE;
-       }
-      else
-       {
-         /* It's not a relocation against a global symbol,
-            but it could be a relocation against a local
-            symbol for a discarded section.  */
-         asection *isec;
-         Elf_Internal_Sym *isym;
-
-         /* Need to: get the symbol; get the section.  */
-         isym = &rcookie->locsyms[r_symndx];
-         isec = bfd_section_from_elf_index (rcookie->abfd, isym->st_shndx);
-         if (isec != NULL
-             && (isec->kept_section != NULL
-                 || discarded_section (isec)))
-           return TRUE;
-       }
+      if (_bfd_elf_section_for_symbol (rcookie, r_symndx, TRUE) != NULL)
+       return TRUE;
       return FALSE;
     }
   return FALSE;