Implement and document --gc-keep-exported

include/
	* bfdlink.h (struct bfd_link_info): Add gc_keep_exported.
bfd/
	* elflink.c (bfd_elf_gc_mark_dynamic_ref_symbol): Add handling
	for info->gc_keep_exported.
	(bfd_elf_gc_sections): Likewise.
ld/
	* ld.texinfo: Document --gc-keep-exported.
	* ldlex.h (enum option_values): Add OPTION_GC_KEEP_EXPORTED.
	* lexsup.c (parse_args): Add handling for --gc-keep-exported.

bfd/ChangeLog

@@ -1,3 +1,9 @@
+2016-12-16  fincs  <fincs.alt1@gmail.com>
+
+	* elflink.c (bfd_elf_gc_mark_dynamic_ref_symbol): Add handling
+	for info->gc_keep_exported.
+	(bfd_elf_gc_sections): Likewise.
+
 2016-12-15  Alan Modra  <amodra@gmail.com>
 
 	PR ld/20968

bfd/elflink.c

@@ -13051,6 +13051,7 @@ bfd_elf_gc_mark_dynamic_ref_symbol (struct elf_link_hash_entry *h, void *inf)
 	      && ELF_ST_VISIBILITY (h->other) != STV_INTERNAL
 	      && ELF_ST_VISIBILITY (h->other) != STV_HIDDEN
 	      && (!bfd_link_executable (info)
+		  || info->gc_keep_exported
 		  || info->export_dynamic
 		  || (h->dynamic
 		      && d != NULL
@@ -13170,7 +13171,7 @@ bfd_elf_gc_sections (bfd *abfd, struct bfd_link_info *info)
     return FALSE;
 
   /* Mark dynamically referenced symbols.  */
-  if (htab->dynamic_sections_created)
+  if (htab->dynamic_sections_created || info->gc_keep_exported)
     elf_link_hash_traverse (htab, bed->gc_mark_dynamic_ref, info);
 
   /* Grovel through relocs to find out who stays ...  */

include/ChangeLog

@@ -1,3 +1,7 @@
+2016-12-16  fincs  <fincs.alt1@gmail.com>
+
+	* bfdlink.h (struct bfd_link_info): Add gc_keep_exported.
+
 2016-12-14  Maciej W. Rozycki  <macro@imgtec.com>
 
 	* elf/mips.h (Elf_Internal_ABIFlags_v0): Also declare struct

include/bfdlink.h

@@ -328,6 +328,9 @@ struct bfd_link_info
   /* TRUE if unreferenced sections should be removed.  */
   unsigned int gc_sections: 1;
 
+  /* TRUE if exported symbols should be kept during section gc.  */
+  unsigned int gc_keep_exported: 1;
+
   /* TRUE if every symbol should be reported back via the notice
      callback.  */
   unsigned int notice_all: 1;

ld/ChangeLog

@@ -1,3 +1,9 @@
+2016-12-16  fincs  <fincs.alt1@gmail.com>
+
+	* ld.texinfo: Document --gc-keep-exported.
+	* ldlex.h (enum option_values): Add OPTION_GC_KEEP_EXPORTED.
+	* lexsup.c (parse_args): Add handling for --gc-keep-exported.
+
 2016-12-14  Yury Norov <ynorov@caviumnetworks.com>
 
 	* ld/testsuite/ld-aarch64/aarch64-elf.exp: Add tests for tiny and

ld/ld.texinfo

@@ -1558,6 +1558,18 @@ default behaviour (of not listing the sections that are removed) can
 be restored by specifying @samp{--no-print-gc-sections} on the command
 line.
 
+@kindex --gc-keep-exported
+@cindex garbage collection
+@item --gc-keep-exported
+When @samp{--gc-sections} is enabled, this option prevents garbage
+collection of unused input sections that contain global symbols having
+default or protected visibility.  This option is intended to be used for
+executables where unreferenced sections would otherwise be garbage
+collected regardless of the external visibility of contained symbols.
+Note that this option has no effect when linking shared objects since
+it is already the default behaviour.  This option is only supported for
+ELF format targets.
+
 @kindex --print-output-format
 @cindex output format
 @item --print-output-format

ld/ldlex.h

@@ -101,6 +101,7 @@ enum option_values
   OPTION_NO_GC_SECTIONS,
   OPTION_PRINT_GC_SECTIONS,
   OPTION_NO_PRINT_GC_SECTIONS,
+  OPTION_GC_KEEP_EXPORTED,
   OPTION_HASH_SIZE,
   OPTION_CHECK_SECTIONS,
   OPTION_NO_CHECK_SECTIONS,

ld/lexsup.c

@@ -335,6 +335,9 @@ static const struct ld_option ld_options[] =
   { {"no-print-gc-sections", no_argument, NULL, OPTION_NO_PRINT_GC_SECTIONS},
     '\0', NULL, N_("Do not list removed unused sections"),
     TWO_DASHES },
+  { {"gc-keep-exported", no_argument, NULL, OPTION_GC_KEEP_EXPORTED},
+    '\0', NULL, N_("Keep exported symbols when removing unused sections"),
+    TWO_DASHES },
   { {"hash-size=<NUMBER>", required_argument, NULL, OPTION_HASH_SIZE},
     '\0', NULL, N_("Set default hash table size close to <NUMBER>"),
     TWO_DASHES },
@@ -861,6 +864,9 @@ parse_args (unsigned argc, char **argv)
 	case OPTION_PRINT_GC_SECTIONS:
 	  link_info.print_gc_sections = TRUE;
 	  break;
+	case OPTION_GC_KEEP_EXPORTED:
+	  link_info.gc_keep_exported = TRUE;
+	  break;
 	case OPTION_HELP:
 	  help ();
 	  xexit (0);