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__clone.S revision 1.3 
      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
     41 WEAK_ALIAS(clone, __clone)
     42 #endif
     43 
     44 /*
     45  * int __clone(int (*fn)(void *), void *stack, int flags, void *arg);
     46  */
     47 ENTRY(__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
     71 8:	JUMP_TO_CERROR()	/* error */
     72 	bnez	a1, 9f		/* success */
     73 	ret			# parent return
     74 
     75 	/* NOTREACHED */
     76 
     77 9:	/*
     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 */
     98 END(__clone)
     99