/*      $NetBSD: execsp.S,v 1.1 2025/04/20 22:32:49 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 22:32:49 riastradh Exp $")

        .import _GLOBAL_OFFSET_TABLE_

/*
 * void execsp_start(struct ps_strings *ps_strings@arg0,
 *     void (*cleanup@arg1)(void), void *obj_main@arg2)
 *
 *      ELF entry point.  Saves the stack pointer in startsp and defers
 *      to the usual csu __start routine.
 */
LEAF_ENTRY(execsp_start)
        /*
         * Set up the data pointer (r19) and linkage table register
         * (r27) like the real startup routine so we can get at the
         * global symbols startsp and __start.
         *
         * XXX Not really sure why we need to set up r27, since we only
         * use r19 here and the real startup routine, __start, will set
         * up both r19 and r27 anyway.  But this crashes with SIGSEGV
         * shortly after startup if we don't set up r27, and gdb
         * crashes on my attempts to single-step, so I'll just leave
         * the initialization of r27 here for now until someone is
         * motivated by the potential for a single-instruction
         * micro-optimization in this test program to find out why r27
         * is needed too.
         */
        bl      L$lpc, %r27
         depi   0, 31, 2, %r27
L$lpc:  addil   L'_GLOBAL_OFFSET_TABLE_ - ($PIC_pcrel$0 - 8), %r27
        ldo     R'_GLOBAL_OFFSET_TABLE_ - ($PIC_pcrel$0 - 12)(%r1), %r27
        copy    %r27, %r19

        addil   LT%_C_LABEL(startsp), %r19      /* r20 := &startsp */
        ldw     RT%_C_LABEL(startsp)(%r1), %r20

        /* PIC_TAILCALL(__start), if we had it */
        addil   LT%_C_LABEL(__start), %r19      /* r1 := __start */
        ldw     RT%_C_LABEL(__start)(%r1), %r1
        bv      %r0(%r1)                        /* jump to __start */
         stw    %sp, 0(%r20)                    /* startsp := sp */
EXIT(execsp_start)

/*
 * void execsp_ctor(void)
 *
 *      ELF constructor.  Saves the stack pointer in ctorsp and
 *      returns.
 */
LEAF_ENTRY(execsp_ctor)
        addil   LT%_C_LABEL(ctorsp), %r19       /* r1 := &ctorsp */
        ldw     RT%_C_LABEL(ctorsp)(%r1), %r1
        bv      %r0(%rp)                        /* return */
         stw    %sp, 0(%r1)                     /* ctorsp := sp */
EXIT(execsp_ctor)

        /* Make execsp_ctor a constructor. */
        .section .ctors,"aw",@progbits
        .p2align 2
        .word   _C_LABEL(execsp_ctor)

/*
 * int main(int argc@arg0, char **argv@arg1, ...)
 *
 *      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_ENTRY(main)
        addil   LT%_C_LABEL(mainsp), %r19       /* r1 := &mainsp */
        ldw     RT%_C_LABEL(mainsp)(%r1), %r1
        stw     %sp, 0(%r1)                     /* ctorsp := sp */
        bv      %r0(%rp)                        /* return... */
         copy   %r0, %ret0                      /* ...zero */
EXIT(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_ENTRY(execsp_dtor)
        addil   LT%_C_LABEL(dtorsp), %r19       /* r20 := &dtorsp */
        ldw     RT%_C_LABEL(dtorsp)(%r1), %r20

        /* PIC_TAILCALL(__start), if we had it */
        addil   LT%_C_LABEL(execsp_main), %r19  /* r1 := execsp_main */
        ldw     RT%_C_LABEL(execsp_main)(%r1), %r1
        bv      %r0(%r1)                        /* jump to execsp_main */
         stw    %sp, 0(%r20)                    /* startsp := sp */
EXIT(execsp_dtor)

        /* Make execsp_ctor a destructor. */
        .section .dtors,"aw",@progbits
        .p2align 2
        .word   _C_LABEL(execsp_dtor)