xref: /src/lib/libc/arch/riscv/sys/fork.S

/*	$NetBSD: fork.S,v 1.3 2023/05/07 12:41:47 skrll Exp $	*/


/*-
 * Copyright (c) 2014 The NetBSD Foundation, Inc.
 * All rights reserved.
 *
 * This code is derived from software contributed to The NetBSD Foundation
 * by Matt Thomas of 3am Software Foundry.
 *
 * 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.h"

#if defined(LIBC_SCCS) && !defined(lint)
	RCSID("$NetBSD: fork.S,v 1.3 2023/05/07 12:41:47 skrll Exp $")
#endif /* LIBC_SCCS and not lint */

/*
 * pid = fork();
 *
 * On return from the SYSTRAP:
 * a1 == 0 in parent process, a1 == 1 in child process.
 * a0 == pid of child in parent, a0 == pid of parent in child.
 */

ENTRY(__fork)
	SYSTRAP(fork)		// pid = fork()
	JUMP_TO_CERROR()	/* error */
	/* success */
	addi	a1, a1, -1	// a1 0->0xffffffff in parent, 1->0 in child
	and	a0, a0, a1	// a0 = child pid in parent, 0 in child
	ret
END(__fork)