/*      $NetBSD: __clone.S,v 1.3 2015/03/27 23:23:14 matt Exp $ */

/*-
 * Copyright (c) 2001 The NetBSD Foundation, Inc.
 * All rights reserved.
 *
 * This code is derived from software contributed to The NetBSD Foundation
 * by Jason R. Thorpe.
 *
 * 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/errno.h>

#include "SYS.h"

#if defined(SYSLIBC_SCCS) && !defined(lint)
        RCSID("$NetBSD: __clone.S,v 1.3 2015/03/27 23:23:14 matt Exp $");
#endif /* SYSLIBC_SCCS and not lint */

#ifdef WEAK_ALIAS
WEAK_ALIAS(clone, __clone)
#endif

/*
 * int __clone(int (*fn)(void *), void *stack, int flags, void *arg);
 */
ENTRY(__clone)
        /*
         * Sanity checks: func and stack may not be NULL.
         */
        mv      t0, a0                  /* we need a0 for return value */
        li      a0, EINVAL
        beqz    t0, 8f
        beqz    a1, 8f

        /*
         * We need to be able to get at the func and arg arguments
         * in the child.  Luckily, we have a convenient place to
         * do this: the child's stack.
         */
        addi    a1, a1, -CALLFRAME_SIZ
        REG_S   t0, 0(a1)
        REG_S   a3, SZREG(a1)

        /*
         * The system call expects (flags, stack).
         */
        mv      a0, a2
        SYSTRAP(__clone)
        # a1 (rv[1]) == 0, parent, child pid in a0
8:      JUMP_TO_CERROR()        /* error */
        bnez    a1, 9f          /* success */
        ret                     # parent return

        /* NOTREACHED */

9:      /*
         * Child: Fetch the function and argument from the new stack and create
         a frame so that the child can be safely called.
         *
         * There are already register slots on the stack from above.
         * They already include the o32 argument save area.  The
         * highest is unused.  a1 should equal sp now.
         */

        REG_L           t0, 0(sp)
        REG_L           a0, SZREG(sp)

        REG_S           zero, CALLFRAME_RA(sp)  /* make sure stack frame ends */

        /* Call the clone's entry point. */
        jalr            t0

        /* Pass the return value to _exit. */
        tail            _C_LABEL(_exit)

        /* NOTREACHED */
END(__clone)