gold, ld: Implement -z start-stop-visibility=... option.

gold/
	Implement -z start-stop-visibility=... option.
	* options.h (class General_options): Handle -z start-stop-visibility=.
	(General_options::start_stop_visibility_enum): New public method.
	(General_options::set_start_stop_visibility_enum): New private method.
	(General_options::start_stop_visibility_enum_): New private member.
	* options.cc (General_options::General_options): Add initializer.
	(General_options::finalize): Set this->start_stop_visibility_enum_
	from string value.
	* layout.cc (Layout::define_section_symbols): Use option setting.

bfd/
	* elflink.c (bfd_elf_define_start_stop): Use start_stop_visibility
	field of bfd_link_info.

include/
	* bfdlink.h (struct bfd_link_info): New field start_stop_visibility.

ld/
	* NEWS: Mention -z start-stop-visibility=... option for ELF.
	* ld.texi (Options): Document -z start-stop-visibility=... option.
	* ldmain.c (main): Initialize link_info.start_stop_visibility.
	* emultempl/elf.em (gld${EMULATION_NAME}_handle_option):
	Parse -z start-stop-visibility=... option.

1 files changed, 13 insertions, 0 deletions

diff --git a/ld/ld.texi b/ld/ld.texi
index bf474d4..b89c1a5 100644
--- a/ld/ld.texi
+++ b/ld/ld.texi
@@ -1373,6 +1373,19 @@ Specify a stack size for an ELF @code{PT_GNU_STACK} segment.
 Specifying zero will override any default non-zero sized
 @code{PT_GNU_STACK} segment creation.
 
+@item start-stop-visibility=@var{value}
+@cindex visibility
+@cindex ELF symbol visibility
+Specify the ELF symbol visibility for synthesized
+@code{__start_SECNAME} and @code{__stop_SECNAME} symbols (@pxref{Input
+Section Example}).  @var{value} must be exactly @samp{default},
+@samp{internal}, @samp{hidden}, or @samp{protected}.  If no @samp{-z
+start-stop-visibility} option is given, @samp{protected} is used for
+compatibility with historical practice.  However, it's highly
+recommended to use @samp{-z start-stop-visibility=hidden} in new
+programs and shared libraries so that these symbols are not exported
+between shared objects, which is not usually what's intended.
+
 @item text
 @itemx notext
 @itemx textoff