/*      $NetBSD: execsp.S,v 1.2 2025/04/27 16:49:54 riastradh Exp $     */

/*-
* Copyright (c) 2025 The NetBSD Foundation, Inc.
* All rights reserved.
*
* 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 NETBSD FOUNDATION, INC. 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 FOUNDATION 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 _LOCORE

#include <machine/asm.h>

RCSID("$NetBSD: execsp.S,v 1.2 2025/04/27 16:49:54 riastradh Exp $")

#include "SYS.h"

       .text

/*
* void execsp_start(void *stackpointer@a0, void (*cleanup@a1)(void),
*     void *obj_main@a2, struct ps_strings *ps_strings@a3)
*
*      ELF entry point.  Saves the stack pointer in startsp and defers
*      to the usual csu __start routine.
*/
LEAF(execsp_start)
       PIC_PROLOGUE(execsp_start)      /* gp setup, sets t3 */

       PTR_LA  t1, _C_LABEL(startsp)   /* load t1 := &startsp */
        NOP_L                          /* load hazard */
       PTR_S   sp, 0(t1)               /* store startsp := stack pointer */

       PIC_TAILCALL(__start)           /* gp restore, uses t3 */
END(execsp_start)

/*
* void execsp_ctor(void)
*
*      ELF constructor.  Saves the stack pointer in ctorsp and
*      returns.
*/
LEAF(execsp_ctor)
       PIC_PROLOGUE(execsp_ctor)       /* gp setup, sets t3 */

       PTR_LA  t1, _C_LABEL(ctorsp)    /* load t1 := &ctorsp */
        NOP_L                          /* load hazard */
       PTR_S   sp, 0(t1)               /* store ctorsp := stack pointer */

       PIC_RETURN()                    /* gp restore, uses t3 */
END(execsp_ctor)

       /* Make execsp_ctor a constructor. */
       .pushsection .ctors,"aw",@progbits
       .p2align PTR_SCALESHIFT
       PTR_WORD        _C_LABEL(execsp_ctor)
       .popsection

/*
* int main(int argc@a0, char **argv@a1, ...)
*
*      Main function.  Saves the stack pointer in mainsp and returns
*      zero.  We will call execsp_main in execsp_dtor once dtorsp has
*      been initialized.
*/
LEAF(main)
       PIC_PROLOGUE(main)              /* gp setup, sets t3 */

       PTR_LA  t1, _C_LABEL(mainsp)    /* load t1 := &mainsp */
        NOP_L                          /* load hazard */
       PTR_S   sp, 0(t1)               /* store mainsp := stack pointer */

       move    v0, zero                /* return 0 */

       PIC_RETURN()                    /* gp restore, uses t3 */
END(main)

/*
* void execsp_dtor(void)
*
*      ELF destructor.  Saves the stack pointer in dtorsp and defers
*      to the C execsp_main in h_execsp.c to report the stack pointers
*      back to the t_signal_and_sp parent.
*/
LEAF(execsp_dtor)
       PIC_PROLOGUE(execsp_dtor)       /* gp setup, sets t3 */

       PTR_LA  t1, _C_LABEL(dtorsp)    /* load t1 := &dtorsp */
        NOP_L                          /* load hazard */
       PTR_S   sp, 0(t1)               /* store dtorsp := stack pointer */

       PIC_TAILCALL(execsp_main)       /* gp restore, uses t3 */
END(execsp_dtor)

       /* Make execsp_ctor a destructor. */
       .pushsection .dtors,"aw",@progbits
       .p2align PTR_SCALESHIFT
       PTR_WORD        _C_LABEL(execsp_dtor)
       .popsection