/*      $NetBSD: execregs.c,v 1.1 2025/02/27 00:55:32 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.
 */

#include <sys/cdefs.h>
__RCSID("$NetBSD: execregs.c,v 1.1 2025/02/27 00:55:32 riastradh Exp $");

#include "execregs.h"

#include <errno.h>
#include <spawn.h>
#include <stddef.h>
#include <unistd.h>

extern char **environ;

static unsigned long
nonnull(unsigned long x)
{

        x |= x << 8;
        x |= x << 16;
        return x;
}

int
execregschild(char *path)
{
        /* fp: frame pointer, nonnull */
        /* ap: argument pointer, on user stack, nonnull */
        /* sp: stack pointer, nonnull */
        register long r0 __asm("r0") = nonnull(0x10);
        register long r1 __asm("r1") = nonnull(1);
        register long r2 __asm("r2") = nonnull(2);
        register long r3 __asm("r3") = nonnull(3);
        register long r4 __asm("r4") = nonnull(4);
        register long r5 __asm("r5") = nonnull(5);
        register long r6 __asm("r6") = nonnull(6);
        register long r7 __asm("r7") = nonnull(7);
        register long r8 __asm("r8") = nonnull(8);
        register long r9 __asm("r9") = nonnull(9);
        register long r10 __asm("r10") = nonnull(10);
        register long r11 __asm("r11") = nonnull(11);
        /* pc: user PC, will be nonnull */
        /* psl: processor status longword, will be nonnull */

        char *argv[] = {path, NULL};
        char **envp = environ;

        /*
         * Not perfect -- compiler might use some registers for
         * stack/argument transfers, but all the arguments are nonnull
         * so this is probably a good test anyway.
         */
        __asm volatile("" :
            "+r"(r0),
            "+r"(r1),
            "+r"(r2),
            "+r"(r3),
            "+r"(r4),
            "+r"(r5),
            "+r"(r6),
            "+r"(r7),
            "+r"(r8),
            "+r"(r9),
            "+r"(r10),
            "+r"(r11)
            :: "memory");

        return execve(path, argv, envp);
}

pid_t
spawnregschild(char *path, int fd)
{
        /* fp: frame pointer, nonnull */
        /* ap: argument pointer, on user stack, nonnull */
        /* sp: stack pointer, nonnull */
        register long r0 __asm("r0") = nonnull(0x10);
        register long r1 __asm("r1") = nonnull(1);
        register long r2 __asm("r2") = nonnull(2);
        register long r3 __asm("r3") = nonnull(3);
        register long r4 __asm("r4") = nonnull(4);
        register long r5 __asm("r5") = nonnull(5);
        register long r6 __asm("r6") = nonnull(6);
        register long r7 __asm("r7") = nonnull(7);
        register long r8 __asm("r8") = nonnull(8);
        register long r9 __asm("r9") = nonnull(9);
        register long r10 __asm("r10") = nonnull(10);
        register long r11 __asm("r11") = nonnull(11);
        /* pc: user PC, will be nonnull */
        /* psl: processor status longword, will be nonnull */

        char *argv[] = {path, NULL};
        char **envp = environ;
        posix_spawn_file_actions_t fileacts;
        posix_spawnattr_t attr;
        pid_t pid;
        int error;

        error = posix_spawn_file_actions_init(&fileacts);
        if (error)
                goto out;
        error = posix_spawn_file_actions_adddup2(&fileacts, fd, STDOUT_FILENO);
        if (error)
                goto out;
        error = posix_spawnattr_init(&attr);
        if (error)
                goto out;

        /*
         * Not perfect -- compiler might use some registers for
         * stack/argument transfers, but all the arguments are nonnull
         * so this is probably a good test anyway.
         */
        __asm volatile("" :
            "+r"(r0),
            "+r"(r1),
            "+r"(r2),
            "+r"(r3),
            "+r"(r4),
            "+r"(r5),
            "+r"(r6),
            "+r"(r7),
            "+r"(r8),
            "+r"(r9),
            "+r"(r10),
            "+r"(r11)
            :: "memory");

        error = posix_spawn(&pid, path, &fileacts, &attr, argv, envp);
        if (error)
                goto out;

out:    posix_spawnattr_destroy(&attr);
        posix_spawn_file_actions_destroy(&fileacts);
        if (error) {
                errno = error;
                return -1;
        }
        return 0;
}