Add generic 'extra TLS'

Add the logic to append an 'extra TLS' block in the TLS block allocator
with a generic stub implementation. The duplicated code in
'csu/libc-tls.c' and 'elf/dl-tls.c' is to handle both statically linked
applications and the ELF dynamic loader.

Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Reviewed-by: Florian Weimer <fweimer@redhat.com>

1 files changed, 46 insertions, 0 deletions

diff --git a/sysdeps/generic/dl-extra_tls.h b/sysdeps/generic/dl-extra_tls.h
new file mode 100644
index 0000000..7f5b10d
--- /dev/null
+++ b/sysdeps/generic/dl-extra_tls.h
@@ -0,0 +1,46 @@
+/* extra tls utils for the dynamic linker.  Generic stub version.
+   Copyright (C) 2025 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#ifndef _DL_EXTRA_TLS_H
+#define _DL_EXTRA_TLS_H 1
+#include <stddef.h>
+
+/* In this generic version, the extra TLS block is unused.  */
+
+/* Returns the size of the extra TLS block, it must always be a multiple of the
+   alignment.  */
+static inline size_t
+_dl_extra_tls_get_size (void)
+{
+	return 0;
+}
+
+/* Returns the alignment requirements of the extra TLS block.  */
+static inline size_t
+_dl_extra_tls_get_align (void)
+{
+	return 0;
+}
+
+/* Record the offset of the extra TLS block from the thread pointer.  */
+static inline void
+_dl_extra_tls_set_offset (ptrdiff_t tls_offset __attribute__ ((unused)))
+{
+}
+
+#endif