Add support for creating ELF import libraries

2016-07-15  Thomas Preud'homme  <thomas.preudhomme@arm.com>

bfd/
	* elf-bfd.h (elf_backend_filter_implib_symbols): Declare backend hook.
	(_bfd_elf_filter_global_symbols): Declare.
	* elf.c (_bfd_elf_filter_global_symbols): New function.
	* elflink.c (elf_filter_global_symbols): Likewise.
	(elf_output_implib): Likewise.
	(bfd_elf_final_link): Call above function, failing if it does.
	* elfxx-target.h (elf_backend_filter_implib_symbols): Define macro and
	default it to NULL.
	(elf_backend_copy_indirect_symbol): Fix spacing.
	(elf_backend_hide_symbol): Likewise.
	(elfNN_bed): Initialize elf_backend_filter_implib_symbols backend hook.

include/
	* bfdlink.h (struct bfd_link_info): Declare new ldscript_def and
	out_implib_bfd fields.

2016-07-15  Thomas Preud'homme  <thomas.preudhomme@arm.com>
	    Nick Clifton  <nickc@redhat.com>

ld/
	* emultempl/elf32.em (gld${EMULATION_NAME}_after_open): Open import
	library file for writing and initialize implib_bfd field of link_info
	structure.
	* emultempl/pe.em (pe_implib_filename): Remove variable declaration.
	(OPTION_IMPLIB_FILENAME): Remove macro definition.
	(gld${EMULATION_NAME}_add_options): Remove --out-implib option.
	(gld_${EMULATION_NAME}_list_options): Likewise.
	(gld${EMULATION_NAME}_handle_option): Likewise.
	(gld_${EMULATION_NAME}_finish): Use command_line.out_implib_filename
	instead of pe_implib_filename.
	* emultempl/pep.em (pep_implib_filename): Remove variable declaration.
	(OPTION_IMPLIB_FILENAME): Remove enumerator.
	(gld${EMULATION_NAME}_add_options): Remove --out-implib option.
	(gld_${EMULATION_NAME}_list_options): Likewise.
	(gld${EMULATION_NAME}_handle_option): Likewise.
	(gld_${EMULATION_NAME}_finish): Use command_line.out_implib_filename
	instead of pep_implib_filename.
	* ld.h (args_type): Declare new out_implib_filename field.
	* ld.texinfo (--out-implib): Move documentation to arch-independent
	part and rephrase to apply to ELF targets.
	* ldexp.c (exp_fold_tree_1): Set ldscript_def field to 1 for symbols
	defined in linker scripts.
	* ldlex.h (enum option_values): Declare new OPTION_OUT_IMPLIB
	enumerator.
	* lexsup.c (ld_options): Add entry for new --out-implib switch.
	(parse_args): Handle OPTION_OUT_IMPLIB case.
	* testsuite/ld-elf/elf.exp (Generate empty import library): New test.
	(Generate import library): Likewise.
	* testsuite/ld-elf/implib.s: Likewise.
	* testsuite/ld-elf/implib.rd: New file.
	* testsuite/ld-elf/empty-implib.out: Likewise

5 files changed, 172 insertions, 2 deletions

diff --git a/bfd/ChangeLog b/bfd/ChangeLog
index b553e1c..ec8fd85 100644
--- a/bfd/ChangeLog
+++ b/bfd/ChangeLog
@@ -1,3 +1,17 @@
+2016-07-15  Thomas Preud'homme  <thomas.preudhomme@arm.com>
+
+	* elf-bfd.h (elf_backend_filter_implib_symbols): Declare backend hook.
+	(_bfd_elf_filter_global_symbols): Declare.
+	* elf.c (_bfd_elf_filter_global_symbols): New function.
+	* elflink.c (elf_filter_global_symbols): Likewise.
+	(elf_output_implib): Likewise.
+	(bfd_elf_final_link): Call above function, failing if it does.
+	* elfxx-target.h (elf_backend_filter_implib_symbols): Define macro and
+	default it to NULL.
+	(elf_backend_copy_indirect_symbol): Fix spacing.
+	(elf_backend_hide_symbol): Likewise.
+	(elfNN_bed): Initialize elf_backend_filter_implib_symbols backend hook.
+
 2016-07-15  Andrew Burgess  <andrew.burgess@embecosm.com>
 	    Nick Clifton  <nickc@redhat.com>
 
diff --git a/bfd/elf-bfd.h b/bfd/elf-bfd.h
index 163ef35..bb3371f 100644
--- a/bfd/elf-bfd.h
+++ b/bfd/elf-bfd.h
@@ -1126,6 +1126,11 @@ struct elf_backend_data
      bfd_boolean (*) (void *, const char *, Elf_Internal_Sym *, asection *,
 		      struct elf_link_hash_entry *));
 
+  /* Filter what symbols of the output file to include in the import
+     library if one is created.  */
+  unsigned int (*elf_backend_filter_implib_symbols)
+    (bfd *, struct bfd_link_info *, asymbol **, long);
+
   /* Copy any information related to dynamic linking from a pre-existing
      symbol to a newly created symbol.  Also called to copy flags and
      other back-end info to a weakdef, in which case the symbol is not
@@ -1951,6 +1956,8 @@ extern bfd_boolean _bfd_elf_section_already_linked
   (bfd *, asection *, struct bfd_link_info *);
 extern void bfd_elf_set_group_contents
   (bfd *, asection *, void *);
+extern unsigned int _bfd_elf_filter_global_symbols
+  (bfd *, struct bfd_link_info *, asymbol **, long);
 extern asection *_bfd_elf_check_kept_section
   (asection *, struct bfd_link_info *);
 #define _bfd_elf_link_just_syms _bfd_generic_link_just_syms
diff --git a/bfd/elf.c b/bfd/elf.c
index cb4de50..ebcf40a 100644
--- a/bfd/elf.c
+++ b/bfd/elf.c
@@ -3870,6 +3870,43 @@ sym_is_global (bfd *abfd, asymbol *sym)
 	  || bfd_is_com_section (bfd_get_section (sym)));
 }
 
+/* Filter global symbols of ABFD to include in the import library.  All
+   SYMCOUNT symbols of ABFD can be examined from their pointers in
+   SYMS.  Pointers of symbols to keep should be stored contiguously at
+   the beginning of that array.
+
+   Returns the number of symbols to keep.  */
+
+unsigned int
+_bfd_elf_filter_global_symbols (bfd *abfd, struct bfd_link_info *info,
+				asymbol **syms, long symcount)
+{
+  long src_count, dst_count = 0;
+
+  for (src_count = 0; src_count < symcount; src_count++)
+    {
+      asymbol *sym = syms[src_count];
+      char *name = (char *) bfd_asymbol_name (sym);
+      struct bfd_link_hash_entry *h;
+
+      if (!sym_is_global (abfd, sym))
+	continue;
+
+      h = bfd_link_hash_lookup (info->hash, name, FALSE, FALSE, FALSE);
+      if (h->type != bfd_link_hash_defined && h->type != bfd_link_hash_defweak)
+	continue;
+
+      if (h->linker_def || h->ldscript_def)
+	continue;
+
+      syms[dst_count++] = sym;
+    }
+
+  syms[dst_count] = NULL;
+
+  return dst_count;
+}
+
 /* Don't output section symbols for sections that are not going to be
    output, that are duplicates or there is no BFD section.  */
 
diff --git a/bfd/elflink.c b/bfd/elflink.c
index 3e24940..b2a814f 100644
--- a/bfd/elflink.c
+++ b/bfd/elflink.c
@@ -11028,6 +11028,107 @@ elf_fixup_link_order (bfd *abfd, asection *o)
   return TRUE;
 }
 
+/* Generate an import library in INFO->implib_bfd from symbols in ABFD.
+   Returns TRUE upon success, FALSE otherwise.  */
+
+static bfd_boolean
+elf_output_implib (bfd *abfd, struct bfd_link_info *info)
+{
+  bfd_boolean ret = FALSE;
+  bfd *implib_bfd;
+  const struct elf_backend_data *bed;
+  flagword flags;
+  enum bfd_architecture arch;
+  unsigned int mach;
+  asymbol **sympp = NULL;
+  long symsize;
+  long symcount;
+  long src_count;
+  elf_symbol_type *osymbuf;
+
+  implib_bfd = info->out_implib_bfd;
+  bed = get_elf_backend_data (abfd);
+
+  if (!bfd_set_format (implib_bfd, bfd_object))
+    return FALSE;
+
+  flags = bfd_get_file_flags (abfd);
+  flags &= ~HAS_RELOC;
+  if (!bfd_set_start_address (implib_bfd, 0)
+      || !bfd_set_file_flags (implib_bfd, flags))
+    return FALSE;
+
+  /* Copy architecture of output file to import library file.  */
+  arch = bfd_get_arch (abfd);
+  mach = bfd_get_mach (abfd);
+  if (!bfd_set_arch_mach (implib_bfd, arch, mach)
+      && (abfd->target_defaulted
+	  || bfd_get_arch (abfd) != bfd_get_arch (implib_bfd)))
+    return FALSE;
+
+  /* Get symbol table size.  */
+  symsize = bfd_get_symtab_upper_bound (abfd);
+  if (symsize < 0)
+    return FALSE;
+
+  /* Read in the symbol table.  */
+  sympp = (asymbol **) xmalloc (symsize);
+  symcount = bfd_canonicalize_symtab (abfd, sympp);
+  if (symcount < 0)
+    goto free_sym_buf;
+
+  /* Allow the BFD backend to copy any private header data it
+     understands from the output BFD to the import library BFD.  */
+  if (! bfd_copy_private_header_data (abfd, implib_bfd))
+    goto free_sym_buf;
+
+  /* Filter symbols to appear in the import library.  */
+  if (bed->elf_backend_filter_implib_symbols)
+    symcount = bed->elf_backend_filter_implib_symbols (abfd, info, sympp,
+						       symcount);
+  else
+    symcount = _bfd_elf_filter_global_symbols (abfd, info, sympp, symcount);
+  if (symcount == 0)
+    {
+      (*_bfd_error_handler) (_("%B: no symbol found for import library"),
+			     implib_bfd);
+      goto free_sym_buf;
+    }
+
+
+  /* Make symbols absolute.  */
+  osymbuf = (elf_symbol_type *) bfd_alloc2 (implib_bfd, symcount,
+					    sizeof (*osymbuf));
+  for (src_count = 0; src_count < symcount; src_count++)
+    {
+      memcpy (&osymbuf[src_count], (elf_symbol_type *) sympp[src_count],
+	      sizeof (*osymbuf));
+      osymbuf[src_count].symbol.section = bfd_abs_section_ptr;
+      osymbuf[src_count].internal_elf_sym.st_shndx = SHN_ABS;
+      osymbuf[src_count].symbol.value += sympp[src_count]->section->vma;
+      osymbuf[src_count].internal_elf_sym.st_value =
+	osymbuf[src_count].symbol.value;
+      sympp[src_count] = &osymbuf[src_count].symbol;
+    }
+
+  bfd_set_symtab (implib_bfd, sympp, symcount);
+
+  /* Allow the BFD backend to copy any private data it understands
+     from the output BFD to the import library BFD.  This is done last
+     to permit the routine to look at the filtered symbol table.  */
+  if (! bfd_copy_private_bfd_data (abfd, implib_bfd))
+    goto free_sym_buf;
+
+  if (!bfd_close (implib_bfd))
+    goto free_sym_buf;
+
+  ret = TRUE;
+
+free_sym_buf:
+  free (sympp);
+  return ret;
+}
+
 static void
 elf_final_link_free (bfd *obfd, struct elf_final_link_info *flinfo)
 {
@@ -11830,6 +11931,13 @@ bfd_elf_final_link (bfd *abfd, struct bfd_link_info *info)
 	return FALSE;
     }
 
+  if (info->out_implib_bfd && !elf_output_implib (abfd, info))
+    {
+      (*_bfd_error_handler) (_("%B: failed to generate import library"),
+			     info->out_implib_bfd);
+      return FALSE;
+    }
+
   /* Adjust the relocs to have the correct symbol indices.  */
   for (o = abfd->sections; o != NULL; o = o->next)
     {
diff --git a/bfd/elfxx-target.h b/bfd/elfxx-target.h
index 97aa5e6..364bddf 100644
--- a/bfd/elfxx-target.h
+++ b/bfd/elfxx-target.h
@@ -524,11 +524,14 @@
 #ifndef elf_backend_output_arch_syms
 #define elf_backend_output_arch_syms		NULL
 #endif
+#ifndef elf_backend_filter_implib_symbols
+#define elf_backend_filter_implib_symbols	NULL
+#endif
 #ifndef elf_backend_copy_indirect_symbol
-#define elf_backend_copy_indirect_symbol  _bfd_elf_link_hash_copy_indirect
+#define elf_backend_copy_indirect_symbol	_bfd_elf_link_hash_copy_indirect
 #endif
 #ifndef elf_backend_hide_symbol
-#define elf_backend_hide_symbol		_bfd_elf_link_hash_hide_symbol
+#define elf_backend_hide_symbol			_bfd_elf_link_hash_hide_symbol
 #endif
 #ifndef elf_backend_fixup_symbol
 #define elf_backend_fixup_symbol		NULL
@@ -764,6 +767,7 @@ static struct elf_backend_data elfNN_bed =
   elf_backend_print_symbol_all,
   elf_backend_output_arch_local_syms,
   elf_backend_output_arch_syms,
+  elf_backend_filter_implib_symbols,
   elf_backend_copy_indirect_symbol,
   elf_backend_hide_symbol,
   elf_backend_fixup_symbol,