Prevent rtld_verify_object_versions() from being called several times

for the same object. This can happen when object is a dependency of the
dlopen()ed dso. When called several times, we waste time due to unneeded
processing, and memory, because obj->vertab is allocated anew on each
iteration.

Reviewed by:	kan
MFC after:	2 weeks

libexec/rtld-elf/rtld.c

@@ -4158,6 +4158,10 @@ rtld_verify_object_versions(Obj_Entry *obj)
     const Obj_Entry *depobj;
     int maxvernum, vernum;
 
+    if (obj->ver_checked)
+	return (0);
+    obj->ver_checked = true;
+
     maxvernum = 0;
     /*
      * Walk over defined and required version records and figure out

libexec/rtld-elf/rtld.h

@@ -230,6 +230,7 @@ typedef struct Struct_Obj_Entry {
     bool mainprog : 1;		/* True if this is the main program */
     bool rtld : 1;		/* True if this is the dynamic linker */
     bool relocated : 1;		/* True if processed by relocate_objects() */
+    bool ver_checked : 1;	/* True if processed by rtld_verify_object_versions */
     bool textrel : 1;		/* True if there are relocations to text seg */
     bool symbolic : 1;		/* True if generated with "-Bsymbolic" */
     bool bind_now : 1;		/* True if all relocations should be made first */