xref: /netbsd-src/lib/libc/arch/riscv/sys/__clone.S (revision 35c3446182b5d2ae37a831f3e9c1597901314cac)
1/*	$NetBSD: __clone.S,v 1.3 2015/03/27 23:23:14 matt Exp $	*/
2
3/*-
4 * Copyright (c) 2001 The NetBSD Foundation, Inc.
5 * All rights reserved.
6 *
7 * This code is derived from software contributed to The NetBSD Foundation
8 * by Jason R. Thorpe.
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 *    notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 *    notice, this list of conditions and the following disclaimer in the
17 *    documentation and/or other materials provided with the distribution.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
20 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
21 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
22 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
23 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
24 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
25 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
26 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
27 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
28 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
29 * POSSIBILITY OF SUCH DAMAGE.
30 */
31
32#include <sys/errno.h>
33
34#include "SYS.h"
35
36#if defined(SYSLIBC_SCCS) && !defined(lint)
37	RCSID("$NetBSD: __clone.S,v 1.3 2015/03/27 23:23:14 matt Exp $");
38#endif /* SYSLIBC_SCCS and not lint */
39
40#ifdef WEAK_ALIAS
41WEAK_ALIAS(clone, __clone)
42#endif
43
44/*
45 * int __clone(int (*fn)(void *), void *stack, int flags, void *arg);
46 */
47ENTRY(__clone)
48	/*
49	 * Sanity checks: func and stack may not be NULL.
50	 */
51	mv	t0, a0			/* we need a0 for return value */
52	li	a0, EINVAL
53	beqz	t0, 8f
54	beqz	a1, 8f
55
56	/*
57	 * We need to be able to get at the func and arg arguments
58	 * in the child.  Luckily, we have a convenient place to
59	 * do this: the child's stack.
60	 */
61	addi	a1, a1, -CALLFRAME_SIZ
62	REG_S	t0, 0(a1)
63	REG_S	a3, SZREG(a1)
64
65	/*
66	 * The system call expects (flags, stack).
67	 */
68	mv	a0, a2
69	SYSTRAP(__clone)
70	# a1 (rv[1]) == 0, parent, child pid in a0
718:	JUMP_TO_CERROR()	/* error */
72	bnez	a1, 9f		/* success */
73	ret			# parent return
74
75	/* NOTREACHED */
76
779:	/*
78	 * Child: Fetch the function and argument from the new stack and create
79	 a frame so that the child can be safely called.
80	 *
81	 * There are already register slots on the stack from above.
82	 * They already include the o32 argument save area.  The
83	 * highest is unused.  a1 should equal sp now.
84	 */
85
86	REG_L		t0, 0(sp)
87	REG_L		a0, SZREG(sp)
88
89	REG_S		zero, CALLFRAME_RA(sp)	/* make sure stack frame ends */
90
91	/* Call the clone's entry point. */
92	jalr		t0
93
94	/* Pass the return value to _exit. */
95	tail		_C_LABEL(_exit)
96
97	/* NOTREACHED */
98END(__clone)
99