Complete the ld.so boot cleanup: move most libc initialization from

_csu_finish() to _libc_preinit(), which is an .init_array function
in shared libc (and mark it INITFIRST) or a .preinit_array function
in static libc, grabbing the _dl_cb callback there from ld.so.  Then
in _csu_finish(), invoke the dl_clean_boot() callback to free ld.so's
startup bits before main() gets control.

Other cleanups this permits:
 - move various startup structures into .data.rel.ro
 - the dl* stubs in libc can be strong and call the callbacks provided
   via _dl_cb
 - no longer need to conditionalize dlctl() calls on presence of _DYNAMIC

original concept and full diff ok kettenis@
ok deraadt@

2 files changed, 5 insertions, 8 deletions

diff --git a/src/lib/libc/include/namespace.h b/src/lib/libc/include/namespace.h
index 79692af0bc..330af4050a 100644
--- a/src/lib/libc/include/namespace.h
+++ b/src/lib/libc/include/namespace.h
@@ -1,4 +1,4 @@
-/*      $OpenBSD: namespace.h,v 1.13 2019/05/13 20:00:32 guenther Exp $ */
+/*      $OpenBSD: namespace.h,v 1.14 2019/06/02 01:03:01 guenther Exp $ */
 
 #ifndef _LIBC_NAMESPACE_H_
 #define _LIBC_NAMESPACE_H_
@@ -59,6 +59,8 @@
 #define MAKE_CLONE(dst, src)    __dso_hidden typeof(dst) HIDDEN(dst) \
                                 __attribute__((alias (HIDDEN_STRING(src))))
 
+#define __relro                 __attribute__((section(".data.rel.ro")))
+
 
 /*
  * gcc and clang will generate calls to the functions below.
diff --git a/src/lib/libc/stdlib/thread_atexit.c b/src/lib/libc/stdlib/thread_atexit.c
index 2e00428eba..ef0423c428 100644
--- a/src/lib/libc/stdlib/thread_atexit.c
+++ b/src/lib/libc/stdlib/thread_atexit.c
@@ -1,4 +1,4 @@
-/*      $OpenBSD: thread_atexit.c,v 1.1 2017/12/16 20:06:56 guenther Exp $ */
+/*      $OpenBSD: thread_atexit.c,v 1.2 2019/06/02 01:03:01 guenther Exp $ */
 /*
  * Copyright (c) 2017 Mark Kettenis <kettenis@openbsd.org>
  *
@@ -16,15 +16,11 @@
  */
 
 #include <dlfcn.h>
-#include <elf.h>
-#pragma weak _DYNAMIC
 #include <stdlib.h>
 #include <tib.h>
 
 #include "atexit.h"
 
-typeof(dlctl) dlctl asm("_dlctl") __attribute__((weak));
-
 __weak_alias(__cxa_thread_atexit, __cxa_thread_atexit_impl);
 
 int
@@ -37,8 +33,7 @@ __cxa_thread_atexit_impl(void (*func)(void *), void *arg, void *dso)
         if (fnp == NULL)
                 return -1;
 
-        if (_DYNAMIC)
-                dlctl(NULL, DL_REFERENCE, dso);
+        dlctl(NULL, DL_REFERENCE, dso);
 
         fnp->func = func;
         fnp->arg = arg;