1 files changed, 40 insertions, 0 deletions
diff --git a/lib/libsys/rfork_thread_gen.c b/lib/libsys/rfork_thread_gen.c
new file mode 100644
index 000000000000..5a8f6e3f650f
--- /dev/null
+++ b/lib/libsys/rfork_thread_gen.c
@@ -0,0 +1,40 @@
+/*-
+ * SPDX-License-Identifier: BSD-2-Clause
+ *
+ * Copyright 2026 The FreeBSD Foundation
+ *
+ * This software were developed by
+ * Konstantin Belousov <kib@FreeBSD.org> under sponsorship from
+ * the FreeBSD Foundation.
+ */
+
+#include <errno.h>
+#include <unistd.h>
+
+pid_t
+rfork_thread(int flags, void *stack_addr, int (*start_fn)(void *), void *arg)
+{
+	pid_t res;
+	int ret;
+
+	/*
+	 * Generic implementation cannot switch stacks.  Only
+	 * architecture-specific code knows how to do it.  Require
+	 * that caller knows that, and refuse to do operate if the
+	 * stack was supplied.
+	 *
+	 * Note that implementations that do switch stack, would fault
+	 * immediately if the passed stack is NULL.  They do not need to
+	 * specifically check for the NULL stack value.
+	 */
+	if (stack_addr != NULL) {
+		errno = EOPNOTSUPP;
+		return (-1);
+	}
+	res = rfork(flags);
+	if (res == 0) {
+		ret = start_fn(arg);
+		_exit(ret);
+	}
+	return (res);
+}