Implement the __pthread_map_stacks_exec() for libthr.

Stack creation code is changed to call _rtld_get_stack_prot() to get
the stack protection right. There is a race where thread is created
during dlopen() of dso that requires executable stacks. Then,
_rtld_get_stack_prot() may return PROT_READ | PROT_WRITE, but thread
is still not linked into the thread list. In this case, the callback
misses the thread stack, and rechecks the required protection
afterward.

Reviewed by:	davidxu

1 files changed, 5 insertions, 0 deletions

diff --git a/lib/libthr/thread/thr_rtld.c b/lib/libthr/thread/thr_rtld.c
index e6af702..d9dd94d 100644
--- a/lib/libthr/thread/thr_rtld.c
+++ b/lib/libthr/thread/thr_rtld.c
@@ -31,6 +31,8 @@
   * A lockless rwlock for rtld.
   */
 #include <sys/cdefs.h>
+#include <sys/mman.h>
+#include <link.h>
 #include <stdlib.h>
 #include <string.h>
 
@@ -194,6 +196,9 @@ _thr_rtld_init(void)
 	/* force to resolve memcpy PLT */
 	memcpy(&dummy, &dummy, sizeof(dummy));
 
+	mprotect(NULL, 0, 0);
+	_rtld_get_stack_prot();
+
 	li.lock_create  = _thr_rtld_lock_create;
 	li.lock_destroy = _thr_rtld_lock_destroy;
 	li.rlock_acquire = _thr_rtld_rlock_acquire;