libdl: calculate the length for second parameter of munmap.

Revert 35105679b9a900d58dadd0852e679c235f8176ba and add some debug
code.

ldso/libdl/libdl.c

@@ -856,6 +856,8 @@ static int do_dlclose(void *vhandle, int need_fini)
 					i < tpnt->n_phent; ppnt++, i++) {
 				if (ppnt->p_type != PT_LOAD)
 					continue;
+				if (ppnt->p_vaddr < start)
+					start = ppnt->p_vaddr;
 				if (end < ppnt->p_vaddr + ppnt->p_memsz)
 					end = ppnt->p_vaddr + ppnt->p_memsz;
 			}
@@ -962,13 +964,15 @@ static int do_dlclose(void *vhandle, int need_fini)
 			}
 #endif
 
-			start = tpnt->mapaddr;
-			_dl_if_debug_print("unmapping before alignment: %s start: '%p' end: '%p'\n", tpnt->libname, start, end);
 			end = (end + ADDR_ALIGN) & PAGE_ALIGN;
 			start = start & ~ADDR_ALIGN;
-			_dl_if_debug_print("unmapping: %s start: '%p' end: '%p'\n", tpnt->libname, start, end);
-			if (end > start)
-			  DL_LIB_UNMAP (tpnt, end - start);
+			if (end > start) {
+				_dl_if_debug_print("unmapping: %s at %p with length: '%p' until %p\n", tpnt->libname, tpnt->mapaddr, end - start, tpnt->mapaddr + (end - start));
+				DL_LIB_UNMAP (tpnt, end - start);
+			}
+			else {
+				_dl_if_debug_print("NOT unmapping: %s at %p. start<end ('%p'<'%p')", tpnt->libname, tpnt->mapaddr, start, end);
+			}
 			/* Free elements in RTLD_LOCAL scope list */
 			for (runp = tpnt->rtld_local; runp; runp = tmp) {
 				tmp = runp->next;