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      1 /*	$NetBSD: _lwp.c,v 1.2 2024/11/30 01:04:03 christos Exp $	*/
      2 
      3 /*
      4  * Copyright (c) 2001 Wasabi Systems, Inc.
      5  * All rights reserved.
      6  *
      7  * Written by Allen Briggs for Wasabi Systems, Inc.
      8  *
      9  * Redistribution and use in source and binary forms, with or without
     10  * modification, are permitted provided that the following conditions
     11  * are met:
     12  * 1. Redistributions of source code must retain the above copyright
     13  *    notice, this list of conditions and the following disclaimer.
     14  * 2. Redistributions in binary form must reproduce the above copyright
     15  *    notice, this list of conditions and the following disclaimer in the
     16  *    documentation and/or other materials provided with the distribution.
     17  * 3. All advertising materials mentioning features or use of this software
     18  *    must display the following acknowledgement:
     19  *      This product includes software developed for the NetBSD Project by
     20  *      Wasabi Systems, Inc.
     21  * 4. The name of Wasabi Systems, Inc. may not be used to endorse
     22  *    or promote products derived from this software without specific prior
     23  *    written permission.
     24  *
     25  * THIS SOFTWARE IS PROVIDED BY WASABI SYSTEMS, INC. ``AS IS'' AND
     26  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
     27  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     28  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL WASABI SYSTEMS, INC
     29  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     30  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
     31  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     32  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     33  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     34  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     35  * POSSIBILITY OF SUCH DAMAGE.
     36  */
     37 
     38 #include <sys/cdefs.h>
     39 #if defined(LIBC_SCCS) && !defined(lint)
     40 __RCSID("$NetBSD: _lwp.c,v 1.2 2024/11/30 01:04:03 christos Exp $");
     41 #endif /* LIBC_SCCS and not lint */
     42 
     43 #include "namespace.h"
     44 #include <sys/param.h>
     45 #include <sys/types.h>
     46 #include <ucontext.h>
     47 #include <lwp.h>
     48 #include <stdlib.h>
     49 
     50 #include <machine/lwp_private.h>
     51 
     52 void
     53 _lwp_makecontext(ucontext_t *u, void (*start)(void *), void *arg,
     54 	void *tcb, caddr_t stack_base, size_t stack_size)
     55 {
     56 	uintptr_t sp;
     57 
     58 	getcontext(u);
     59 	u->uc_link = NULL;
     60 
     61 	u->uc_stack.ss_sp = stack_base;
     62 	u->uc_stack.ss_size = stack_size;
     63 
     64 	sp = (uintptr_t)stack_base + stack_size;
     65 	sp -= STACK_ALIGNBYTES + 1;
     66 	sp &= ~STACK_ALIGNBYTES;
     67 
     68 	u->uc_mcontext.__gregs[_REG_RV] = (uintptr_t)arg;	/* arg1 */
     69 	u->uc_mcontext.__gregs[_REG_SP] = (uintptr_t)sp;	/* stack */
     70 	u->uc_mcontext.__gregs[_REG_RA] = (uintptr_t)_lwp_exit;	/* RA */
     71 	u->uc_mcontext.__gregs[_REG_PC] = (uintptr_t)start;	/* PC */
     72 	u->uc_mcontext.__gregs[_REG_TP] =
     73 	    (uintptr_t)tcb + TLS_TP_OFFSET + sizeof(struct tls_tcb);
     74 }
     75