Fix known issues which blow up the process after dlopen("libthr.so")

(or loading a dso linked to libthr.so into process which was not
linked against threading library).

MFC r276630:
Remove interposing, fix malloc, reinstall signal handlers wrappers on
libthr load.

MFC r276681:
Avoid calling internal libc function through PLT or accessing data
though GOT.

MFC r277032:
Reduce the size of the interposing table and amount of
cancellation-handling code in the libthr.

MFC note:
r276646 ("do not erronously export 'openat' symbol from rtld") is not
applicable to stable/10 yet, since PATHFDS support was not merged.

1 files changed, 6 insertions, 2 deletions

diff --git a/lib/libthr/thread/thr_create.c b/lib/libthr/thread/thr_create.c
index a41b33f..df3509d 100644
--- a/lib/libthr/thread/thr_create.c
+++ b/lib/libthr/thread/thr_create.c
@@ -40,6 +40,7 @@
 #include <pthread_np.h>
 #include "un-namespace.h"
 
+#include "libc_private.h"
 #include "thr_private.h"
 
 static int  create_stack(struct pthread_attr *pattr);
@@ -66,8 +67,11 @@ _pthread_create(pthread_t * thread, const pthread_attr_t * attr,
 	/*
 	 * Tell libc and others now they need lock to protect their data.
 	 */
-	if (_thr_isthreaded() == 0 && _thr_setthreaded(1))
-		return (EAGAIN);
+	if (_thr_isthreaded() == 0) {
+		_malloc_first_thread();
+		if (_thr_setthreaded(1))
+			return (EAGAIN);
+	}
 
 	curthread = _get_curthread();
 	if ((new_thread = _thr_alloc(curthread)) == NULL)