/*      $NetBSD: execsp.S,v 1.1 2025/04/20 22:33:41 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 1.1 2025/04/20 22:33:41 riastradh Exp $")

#ifdef __PIC__
#define SETHI(label, got, reg)                                                \
       set     label, reg;             /* reg := &label - &GOT */            \
       ld      [got + reg], reg        /* reg := &label */
#define LO(label, reg)                                                        \
       reg
#else
#define SETHI(label, got, reg)                                                \
       sethi   %hi(label), reg         /* reg := &label - %lo(label) */
#define LO(label, reg)                                                        \
       reg + %lo(label)
#endif

       .text

/*
* void execsp_start(struct ps_strings *ps_strings@g1,
*     void *obj_main@g2, void (*cleanup@g3)(void))
*
*      ELF entry point.  Saves the stack pointer in startsp and defers
*      to the usual csu __start routine.
*/
ENTRY(execsp_start)
       PIC_PROLOGUE(%o1, %o2)                  /* o1 := GOT, clobber o2 */
       SETHI(_C_LABEL(startsp), %o1, %o2)      /* o2 := &startup */
       call    _C_LABEL(__start)               /* jump to start via PLT */
        st     %sp, [LO(_C_LABEL(startsp), %o2)] /* startsp := sp */
       /* don't care what happens here, caller must never return */
       ta      1                               /* Tcc, trap always */
END(execsp_start)

/*
* void execsp_ctor(void)
*
*      ELF constructor.  Saves the stack pointer in ctorsp and
*      returns.
*/
ENTRY(execsp_ctor)
       /* Reminder: o6 is frame pointer, o7 + 8 is return address. */
       PIC_PROLOGUE(%g1, %o5)                  /* g1 := &GOT, clobber o5 */
       SETHI(_C_LABEL(ctorsp), %g1, %o5)       /* o5 := &ctorsp */
       retl                                    /* return to caller */
        st     %sp, [LO(_C_LABEL(ctorsp), %o5)] /* ctorsp := sp */
END(execsp_ctor)

       /* Make execsp_ctor a constructor. */
       .pushsection .ctors,"aw",@progbits
       .p2align 2
       .long   _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.
*/
ENTRY(main)
       /* Reminder: o6 is frame pointer, o7 + 8 is return address. */
       PIC_PROLOGUE(%g1, %o5)                  /* g1 := &GOT, clobber o5 */
       SETHI(_C_LABEL(mainsp), %g1, %o5)       /* o5 := &mainsp */
       st      %sp, [LO(_C_LABEL(mainsp), %o5)] /* mainsp := sp */
       retl                                    /* return to caller */
        mov    0, %o0                          /* return 0 */
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.
*/
ENTRY(execsp_dtor)
       /* Reminder: o6 is frame pointer, o7 + 8 is return address. */
       PIC_PROLOGUE(%g1, %o5)                  /* g1 := &GOT, clobber o5 */
       SETHI(_C_LABEL(dtorsp), %g1, %o5)       /* o5 := &dtorsp - &GOT */
       st      %sp, [LO(_C_LABEL(dtorsp), %o5)] /* dtorsp := sp */
       mov     %o7, %o5                        /* save return address */
       call    _C_LABEL(execsp_main)           /* tail call to execsp_main */
        mov    %o5, %o7                        /* restore return address */
END(execsp_dtor)

       /* Make execsp_ctor a destructor. */
       .pushsection .dtors,"aw",@progbits
       .p2align 2
       .long   _C_LABEL(execsp_dtor)
       .popsection

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