1*d30ea906Sjfb8856606 /* SPDX-License-Identifier: BSD-3-Clause
2*d30ea906Sjfb8856606  * Copyright(c) 2017 Cavium, Inc
32bfe3f2eSlogwang  */
42bfe3f2eSlogwang 
52bfe3f2eSlogwang #ifndef STACK_H
62bfe3f2eSlogwang #define STACK_H
72bfe3f2eSlogwang 
82bfe3f2eSlogwang #ifdef __cplusplus
92bfe3f2eSlogwang extern "C" {
102bfe3f2eSlogwang #endif
112bfe3f2eSlogwang 
122bfe3f2eSlogwang #include "lthread_int.h"
132bfe3f2eSlogwang 
142bfe3f2eSlogwang /*
152bfe3f2eSlogwang  * Sets up the initial stack for the lthread.
162bfe3f2eSlogwang  */
172bfe3f2eSlogwang static inline void
arch_set_stack(struct lthread * lt,void * func)182bfe3f2eSlogwang arch_set_stack(struct lthread *lt, void *func)
192bfe3f2eSlogwang {
202bfe3f2eSlogwang 	void **stack_top = (void *)((char *)(lt->stack) + lt->stack_size);
212bfe3f2eSlogwang 
222bfe3f2eSlogwang 	/*
232bfe3f2eSlogwang 	 * Align stack_top to 16 bytes. Arm64 has the constraint that the
242bfe3f2eSlogwang 	 * stack pointer must always be quad-word aligned.
252bfe3f2eSlogwang 	 */
262bfe3f2eSlogwang 	stack_top = (void **)(((unsigned long)(stack_top)) & ~0xfUL);
272bfe3f2eSlogwang 
282bfe3f2eSlogwang 	/*
292bfe3f2eSlogwang 	 * First Stack Frame
302bfe3f2eSlogwang 	 */
312bfe3f2eSlogwang 	stack_top[0] = NULL;
322bfe3f2eSlogwang 	stack_top[-1] = NULL;
332bfe3f2eSlogwang 
342bfe3f2eSlogwang 	/*
352bfe3f2eSlogwang 	 * Initialize the context
362bfe3f2eSlogwang 	 */
372bfe3f2eSlogwang 	lt->ctx.fp = &stack_top[-1];
382bfe3f2eSlogwang 	lt->ctx.sp = &stack_top[-2];
392bfe3f2eSlogwang 
402bfe3f2eSlogwang 	/*
412bfe3f2eSlogwang 	 * Here only the address of _lthread_exec is saved as the link
422bfe3f2eSlogwang 	 * register value. The argument to _lthread_exec i.e the address of
432bfe3f2eSlogwang 	 * the lthread struct is not saved. This is because the first
442bfe3f2eSlogwang 	 * argument to ctx_switch is the address of the new context,
452bfe3f2eSlogwang 	 * which also happens to be the address of required lthread struct.
462bfe3f2eSlogwang 	 * So while returning from ctx_switch into _thread_exec, parameter
472bfe3f2eSlogwang 	 * register x0 will always contain the required value.
482bfe3f2eSlogwang 	 */
492bfe3f2eSlogwang 	lt->ctx.lr = func;
502bfe3f2eSlogwang }
512bfe3f2eSlogwang 
522bfe3f2eSlogwang #ifdef __cplusplus
532bfe3f2eSlogwang }
542bfe3f2eSlogwang #endif
552bfe3f2eSlogwang 
562bfe3f2eSlogwang #endif /* STACK_H_ */
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