1 files changed, 51 insertions, 0 deletions
diff --git a/lib/libsys/amd64/amd64_set_tlsbase.c b/lib/libsys/amd64/amd64_set_tlsbase.c
new file mode 100644
index 000000000000..a28441fbfc5d
--- /dev/null
+++ b/lib/libsys/amd64/amd64_set_tlsbase.c
@@ -0,0 +1,51 @@
+/*-
+ * SPDX-License-Identifier: BSD-2-Clause
+ *
+ * Copyright (c) 2025 The FreeBSD Foundation
+ * All rights reserved.
+ *
+ * This software was developed by Konstantin Belousov
+ * under sponsorship from the FreeBSD Foundation.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#define _WANT_P_OSREL
+#include <sys/param.h>
+#include <machine/cpufunc.h>
+#include <machine/specialreg.h>
+#include <machine/sysarch.h>
+#include <x86/ifunc.h>
+#include "libc_private.h"
+
+static int
+amd64_set_tlsbase_syscall(void *addr)
+{
+	return (sysarch(AMD64_SET_TLSBASE, &addr));
+}
+
+DEFINE_UIFUNC(, int, amd64_set_tlsbase, (void *))
+{
+	if (__getosreldate() >= P_OSREL_TLSBASE)
+		return (amd64_set_tlsbase_syscall);
+	return (amd64_set_fsbase);
+}