Change ld.so to correctly load dependant libraries for dlopen and unload them

on dlclose.  Also correctly call constructors and destructors for libraries
linked with /usr/lib/c++rt0.o.
Change interpretation of dlopen manpage to call _init() rather than init()
for dlopened objects.
Change c++rt0.o to avoid using atexit to call destructors, allowing dlclose to
call destructors when an object is unloaded.
Change interface between crt0 and ld.so to allow crt0 to call a function on
exit to call destructors for shared libraries explicitly.

These changes are backwards compatible.  Old binaries will work with the new
ld.so and new binaries will work with the old ld.so.  A version number has
been introduced in the crt0-ld.so interface to allow for future changes.

Reviewed by:	GAWollman, Craig Struble <cstruble@singularity.bevc.blacksburg.va.us>

2 files changed, 16 insertions, 4 deletions

diff --git a/lib/csu/i386/c++rt0.c b/lib/csu/i386/c++rt0.c
index df85907..aa28109 100644
--- a/lib/csu/i386/c++rt0.c
+++ b/lib/csu/i386/c++rt0.c
@@ -27,7 +27,7 @@
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  *
- *	$Id: c++rt0.c,v 1.1 1994/03/09 17:12:59 nate Exp $
+ *	$Id: c++rt0.c,v 1.2 1995/05/30 05:39:36 rgrimes Exp $
  */
 
 /*
@@ -61,6 +61,7 @@ __ctors(void)
 }
 
 extern void __init() asm(".init");
+extern void __fini() asm(".fini");
 
 void
 __init(void)
@@ -74,7 +75,12 @@ __init(void)
 	if (!initialized) {
 		initialized = 1;
 		__ctors();
-		atexit(__dtors);
 	}
 
 }
+
+void
+__fini(void)
+{
+	__dtors();
+}
diff --git a/lib/csu/i386/crt0.c b/lib/csu/i386/crt0.c
index f6f0759..7959e66 100644
--- a/lib/csu/i386/crt0.c
+++ b/lib/csu/i386/crt0.c
@@ -27,7 +27,7 @@
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  *
- *	$Id: crt0.c,v 1.15 1995/02/07 13:27:29 jkh Exp $
+ *	$Id: crt0.c,v 1.16 1995/02/24 07:51:13 phk Exp $
  */
 
 
@@ -194,6 +194,7 @@ __do_dynamic_link ()
 	struct exec	hdr;
 	char		*ldso;
 	int		(*entry)();
+	int		ret;
 
 #ifdef DEBUG
 	/* Provision for alternate ld.so - security risk! */
@@ -259,11 +260,16 @@ __do_dynamic_link ()
 	crt.crt_prog = __progname;
 
 	entry = (int (*)())(crt.crt_ba + sizeof hdr);
-	if ((*entry)(CRT_VERSION_BSD_3, &crt) == -1) {
+	ret = (*entry)(CRT_VERSION_BSD_3, &crt);
+	if (ret == -1) {
 		_FATAL("ld.so failed\n");
 	}
 
 	ld_entry = _DYNAMIC.d_entry;
+
+	if (ret >= LDSO_VERSION_HAS_DLEXIT)
+		atexit(ld_entry->dlexit);
+
 	return;
 }