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resumecontext.S revision 1.3 
      1 /*	$NetBSD: resumecontext.S,v 1.3 2006/11/08 20:28:03 drochner 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  * Modified for x86-64 by fvdl (at) wasabisystems.com
     39  */
     40 
     41 #include <machine/asm.h>
     42 #include "SYS.h"
     43 
     44 #if defined(LIBC_SCCS) && !defined(lint)
     45 	RCSID("$NetBSD: resumecontext.S,v 1.3 2006/11/08 20:28:03 drochner Exp $")
     46 #endif /* LIBC_SCCS && !lint */
     47 
     48 /*
     49  * This assembly-language implementation differs from the (obvious)
     50  * C-language implementation only in not clobbering the previous
     51  * function's return address (us), which is the point of the exercise.
     52  */
     53 
     54 NENTRY(_resumecontext)	/* profiling prologue would clobber TOS */
     55 	leaq	-(8 + 784)(%rsp),%rdi	/* retaddr + sizeof (ucontext_t) */
     56 	andq	$~15,%rdi		/* align on _UC_UCONTEXT_ALIGN */
     57 	movq	%rdi,%rsp
     58 #ifdef PIC
     59 	call	PIC_PLT(_C_LABEL(_getcontext))
     60 #else
     61 	call	_C_LABEL(_getcontext)
     62 #endif
     63 	movq	8(%rsp),%rdi	/* uc_link */
     64 	testq	%rdi,%rdi	/* link end? */
     65 	jnz	9f
     66 
     67 	/* normal exit */
     68 #ifdef PIC
     69 	call	PIC_PLT(_C_LABEL(exit))
     70 #else
     71 	call	_C_LABEL(exit)
     72 #endif
     73 
     74 9:
     75 #ifdef PIC
     76 	call	PIC_PLT(_C_LABEL(setcontext))
     77 #else
     78 	call	_C_LABEL(setcontext)
     79 #endif
     80 	/* NOTREACHED */
     81 
     82 	/* something is wrong, pull the brake */
     83 	movq	$-1,%rdi
     84 	movq	$SYS_exit,%rax
     85 	syscall
     86 	/* NOTREACHED */
     87