Support .gnu.lto_.lto section in ELF files (PR 24768).

bfd/ChangeLog:

2019-07-22  Martin Liska  <mliska@suse.cz>

	PR 24768
	* archive.c (_bfd_compute_and_write_armap): Come up with
	report_plugin_err variable.
	* bfd-in2.h (struct bfd): Add lto_slim_object flag.
	* elf.c (struct lto_section): New.
	(_bfd_elf_make_section_from_shdr): Parse content of
	.gnu_lto_.lto section.
	* elflink.c: Report error for a missing LTO plugin.
	* linker.c (_bfd_generic_link_add_one_symbol): Likewise.

binutils/ChangeLog:

2019-07-22  Martin Liska  <mliska@suse.cz>

	PR 24768
	* nm.c (filter_symbols): Set report_plugin_err if
	error is reported.
	(display_rel_file): Report error for a missing LTO plugin.

gold/ChangeLog:

2019-07-22  Martin Liska  <mliska@suse.cz>

	PR 24768
	* layout.h (class Layout): Add is_lto_slim_object and
	set_lto_slim_object.
	* object.cc (struct lto_section): Add lto_slim_object_.
	(big_endian>::do_layout): Parse content of
	.gnu_lto_.lto section.
	(big_endian>::do_add_symbols): Report error for a missing
	LTO plugin.

6 files changed, 79 insertions, 10 deletions

diff --git a/bfd/ChangeLog b/bfd/ChangeLog
index 1364904..4258351 100644
--- a/bfd/ChangeLog
+++ b/bfd/ChangeLog
@@ -1,3 +1,15 @@
+2019-07-29  Martin Liska  <mliska@suse.cz>
+
+	PR 24768
+	* archive.c (_bfd_compute_and_write_armap): Come up with
+	report_plugin_err variable.
+	* bfd-in2.h (struct bfd): Add lto_slim_object flag.
+	* elf.c (struct lto_section): New.
+	(_bfd_elf_make_section_from_shdr): Parse content of
+	.gnu_lto_.lto section.
+	* elflink.c: Report error for a missing LTO plugin.
+	* linker.c (_bfd_generic_link_add_one_symbol): Likewise.
+
 2019-07-28  Alan Modra  <amodra@gmail.com>
 
 	PR 24857
diff --git a/bfd/archive.c b/bfd/archive.c
index 68a92a3..0a7da3a 100644
--- a/bfd/archive.c
+++ b/bfd/archive.c
@@ -2236,6 +2236,7 @@ _bfd_compute_and_write_armap (bfd *arch, unsigned int elength)
   long syms_max = 0;
   bfd_boolean ret;
   bfd_size_type amt;
+  static bfd_boolean report_plugin_err = TRUE;
 
   /* Dunno if this is the best place for this info...  */
   if (elength != 0)
@@ -2270,6 +2271,14 @@ _bfd_compute_and_write_armap (bfd *arch, unsigned int elength)
 	  long symcount;
 	  long src_count;
 
+	  if (current->lto_slim_object && report_plugin_err)
+	    {
+	      report_plugin_err = FALSE;
+	      _bfd_error_handler
+		(_("%pB: plugin needed to handle lto object"),
+		 current);
+	    }
+
 	  storage = bfd_get_symtab_upper_bound (current);
 	  if (storage < 0)
 	    goto error_return;
@@ -2322,10 +2331,14 @@ _bfd_compute_and_write_armap (bfd *arch, unsigned int elength)
 			  && syms[src_count]->name[1] == '_'
 			  && strcmp (syms[src_count]->name
 				     + (syms[src_count]->name[2] == '_'),
-				     "__gnu_lto_slim") == 0)
-			_bfd_error_handler
-			  (_("%pB: plugin needed to handle lto object"),
-			   current);
+				     "__gnu_lto_slim") == 0
+			  && report_plugin_err)
+			{
+			  report_plugin_err = FALSE;
+			  _bfd_error_handler
+			    (_("%pB: plugin needed to handle lto object"),
+			     current);
+			}
 		      namelen = strlen (syms[src_count]->name);
 		      amt = sizeof (char *);
 		      map[orl_count].name = (char **) bfd_alloc (arch, amt);
diff --git a/bfd/bfd-in2.h b/bfd/bfd-in2.h
index 8374390..7e6dad7 100644
--- a/bfd/bfd-in2.h
+++ b/bfd/bfd-in2.h
@@ -7196,6 +7196,9 @@ struct bfd
   /* Set if this is a plugin output file.  */
   unsigned int lto_output : 1;
 
+  /* Set if this is a slim LTO object not loaded with a compiler plugin.  */
+  unsigned int lto_slim_object: 1;
+
   /* Set to dummy BFD created when claimed by a compiler plug-in
      library.  */
   bfd *plugin_dummy_bfd;
diff --git a/bfd/elf.c b/bfd/elf.c
index f47e88b..6b5d12c 100644
--- a/bfd/elf.c
+++ b/bfd/elf.c
@@ -999,6 +999,18 @@ convert_zdebug_to_debug (bfd *abfd, const char *name)
   return new_name;
 }
 
+/* This a copy of lto_section defined in GCC (lto-streamer.h).  */
+
+struct lto_section
+{
+  int16_t major_version;
+  int16_t minor_version;
+  unsigned char slim_object;
+
+  /* Flags is a private field that is not defined publicly.  */
+  uint16_t flags;
+};
+
 /* Make a BFD section from an ELF section.  We store a pointer to the
    BFD section in the bfd_section field of the header.  */
 
@@ -1275,6 +1287,17 @@ _bfd_elf_make_section_from_shdr (bfd *abfd,
 	newsect->flags |= SEC_ELF_RENAME;
     }
 
+  /* GCC uses .gnu.lto_.lto.<some_hash> as a LTO bytecode information
+     section.  */
+  const char *lto_section_name = ".gnu.lto_.lto.";
+  if (strncmp (name, lto_section_name, strlen (lto_section_name)) == 0)
+    {
+      struct lto_section lsection;
+      if (bfd_get_section_contents (abfd, newsect, &lsection, 0,
+				    sizeof (struct lto_section)))
+	abfd->lto_slim_object = lsection.slim_object;
+    }
+
   return TRUE;
 }
 
diff --git a/bfd/elflink.c b/bfd/elflink.c
index ad146d4..5971845 100644
--- a/bfd/elflink.c
+++ b/bfd/elflink.c
@@ -4401,6 +4401,12 @@ error_free_dyn:
       goto error_free_vers;
     }
 
+  if (abfd->lto_slim_object)
+    {
+      _bfd_error_handler
+	(_("%pB: plugin needed to handle lto object"), abfd);
+    }
+
   for (isym = isymbuf, isymend = isymbuf + extsymcount;
        isym < isymend;
        isym++, sym_hash++, ever = (ever != NULL ? ever + 1 : NULL))
diff --git a/bfd/linker.c b/bfd/linker.c
index 1b71fcf..edbd0a7 100644
--- a/bfd/linker.c
+++ b/bfd/linker.c
@@ -1421,12 +1421,24 @@ _bfd_generic_link_add_one_symbol (struct bfd_link_info *info,
   else if (bfd_is_com_section (section))
     {
       row = COMMON_ROW;
-      if (!bfd_link_relocatable (info)
-	  && name[0] == '_'
-	  && name[1] == '_'
-	  && strcmp (name + (name[2] == '_'), "__gnu_lto_slim") == 0)
-	_bfd_error_handler
-	  (_("%pB: plugin needed to handle lto object"), abfd);
+      static bfd_boolean report_plugin_err = TRUE;
+      if (!bfd_link_relocatable (info) && report_plugin_err)
+	{
+	  if (abfd->lto_slim_object)
+	    {
+	      report_plugin_err = FALSE;
+	      _bfd_error_handler
+		(_("%pB: plugin needed to handle lto object"), abfd);
+	    }
+	  else if (name[0] == '_'
+		   && name[1] == '_'
+		   && strcmp (name + (name[2] == '_'), "__gnu_lto_slim") == 0)
+	    {
+	      report_plugin_err = FALSE;
+	      _bfd_error_handler
+		(_("%pB: plugin needed to handle lto object"), abfd);
+	    }
+	}
     }
   else
     row = DEF_ROW;