add system for resetting TLS to initial values

this is needed for reused threads in the SIGEV_THREAD timer
notification system, and could be reused elsewhere in the future if
needed, though it should be refactored for such use.

for static linking, __init_tls.c is simply modified to export the TLS
info in a structure with external linkage, rather than using statics.
this perhaps makes the code more clear, since the statics were poorly
named for statics. the new __reset_tls.c is only linked if it is used.

for dynamic linking, the code is in dynlink.c. sharing code with
__copy_tls is not practical since __reset_tls must also re-zero
thread-local bss.

1 files changed, 22 insertions, 0 deletions

diff --git a/src/env/__reset_tls.c b/src/env/__reset_tls.c
new file mode 100644
index 00000000..28c4405e
--- /dev/null
+++ b/src/env/__reset_tls.c
@@ -0,0 +1,22 @@
+#ifndef SHARED
+
+#include <string.h>
+#include "pthread_impl.h"
+#include "libc.h"
+
+extern struct tls_image {
+	void *image;
+	size_t len, size, align;
+} __static_tls ATTR_LIBC_VISIBILITY;
+
+#define T __static_tls
+
+void __reset_tls()
+{
+	if (!T.size) return;
+	pthread_t self = __pthread_self();
+	memcpy(self->dtv[1], T.image, T.len);
+	memset((char *)self->dtv[1]+T.len, 0, T.size-T.len);
+}
+
+#endif