add membarrier syscall wrapper, refactor dynamic tls install to use it

the motivation for this change is twofold. first, it gets the fallback
logic out of the dynamic linker, improving code readability and
organization. second, it provides application code that wants to use
the membarrier syscall, which depends on preregistration of intent
before the process becomes multithreaded unless unbounded latency is
acceptable, with a symbol that, when linked, ensures that this
registration happens.

1 files changed, 9 insertions, 0 deletions

diff --git a/src/include/sys/membarrier.h b/src/include/sys/membarrier.h
new file mode 100644
index 00000000..3654491c
--- /dev/null
+++ b/src/include/sys/membarrier.h
@@ -0,0 +1,9 @@
+#ifndef SYS_MEMBARRIER_H
+#define SYS_MEMBARRIER_H
+
+#include "../../../include/sys/membarrier.h"
+#include <features.h>
+
+hidden int __membarrier(int, int);
+
+#endif