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resumecontext.S revision 1.4 
      1 /*	$NetBSD: resumecontext.S,v 1.4 2003/01/26 18:14:03 kleink Exp $	*/
      2 
      3 /*-
      4  * Copyright (c) 1999 The NetBSD Foundation, Inc.
      5  * All rights reserved.
      6  *
      7  * This code is derived from software contributed to The NetBSD Foundation
      8  * by Klaus Klein.
      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  * 3. All advertising materials mentioning features or use of this software
     19  *    must display the following acknowledgement:
     20  *        This product includes software developed by the NetBSD
     21  *        Foundation, Inc. and its contributors.
     22  * 4. Neither the name of The NetBSD Foundation nor the names of its
     23  *    contributors may be used to endorse or promote products derived
     24  *    from this software without specific prior written permission.
     25  *
     26  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
     27  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
     28  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     29  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
     30  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     31  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
     32  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     33  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     34  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     35  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     36  * POSSIBILITY OF SUCH DAMAGE.
     37  */
     38 
     39 #include <machine/asm.h>
     40 
     41 #if defined(LIBC_SCCS) && !defined(lint)
     42 	RCSID("$NetBSD: resumecontext.S,v 1.4 2003/01/26 18:14:03 kleink Exp $")
     43 #endif /* LIBC_SCCS && !lint */
     44 
     45 /*
     46  * This assembly-language implementation differs from the (obvious)
     47  * C-language implementation only in not clobbering the previous
     48  * function's return address (us), which is the point of the exercise.
     49  */
     50 
     51 NENTRY(_resumecontext)	/* profiling prologue would clobber TOS */
     52 	leal	-(4 + 776)(%esp),%ecx	/* retaddr + sizeof (ucontext_t) */
     53 	andl	$~(0xf),%ecx		/* align on _UC_UCONTEXT_ALIGN */
     54 	movl	%ecx,%esp
     55 	PIC_PROLOGUE
     56 	pushl	%ecx
     57 #ifdef PIC
     58 	call	PIC_PLT(_C_LABEL(_getcontext))
     59 #else
     60 	call	_C_LABEL(_getcontext)
     61 #endif
     62 	addl	$4,%esp
     63 	PIC_EPILOGUE
     64 	movl	4(%esp),%ecx		/* uc_link */
     65 	PIC_PROLOGUE
     66 	pushl	%ecx
     67 #ifdef PIC
     68 	call	PIC_PLT(_C_LABEL(setcontext))
     69 #else
     70 	call	_C_LABEL(setcontext)
     71 #endif
     72 	/* NOTREACHED */
     73