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+/*
+ * BSD LICENSE
+ *
+ * Copyright (C) Cavium, Inc. 2017.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ * * 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.
+ * * Neither the name of Cavium, Inc nor the names of its
+ * contributors may be used to endorse or promote products derived
+ * from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS 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 COPYRIGHT
+ * OWNER 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.
+ */
+
+#ifndef STACK_H
+#define STACK_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include "lthread_int.h"
+
+/*
+ * Sets up the initial stack for the lthread.
+ */
+static inline void
+arch_set_stack(struct lthread *lt, void *func)
+{
+ void **stack_top = (void *)((char *)(lt->stack) + lt->stack_size);
+
+ /*
+ * Align stack_top to 16 bytes. Arm64 has the constraint that the
+ * stack pointer must always be quad-word aligned.
+ */
+ stack_top = (void **)(((unsigned long)(stack_top)) & ~0xfUL);
+
+ /*
+ * First Stack Frame
+ */
+ stack_top[0] = NULL;
+ stack_top[-1] = NULL;
+
+ /*
+ * Initialize the context
+ */
+ lt->ctx.fp = &stack_top[-1];
+ lt->ctx.sp = &stack_top[-2];
+
+ /*
+ * Here only the address of _lthread_exec is saved as the link
+ * register value. The argument to _lthread_exec i.e the address of
+ * the lthread struct is not saved. This is because the first
+ * argument to ctx_switch is the address of the new context,
+ * which also happens to be the address of required lthread struct.
+ * So while returning from ctx_switch into _thread_exec, parameter
+ * register x0 will always contain the required value.
+ */
+ lt->ctx.lr = func;
+}
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* STACK_H_ */