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      1 /*
      2  * CDDL HEADER START
      3  *
      4  * The contents of this file are subject to the terms of the
      5  * Common Development and Distribution License (the "License").
      6  * You may not use this file except in compliance with the License.
      7  *
      8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
      9  * or http://www.opensolaris.org/os/licensing.
     10  * See the License for the specific language governing permissions
     11  * and limitations under the License.
     12  *
     13  * When distributing Covered Code, include this CDDL HEADER in each
     14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
     15  * If applicable, add the following below this CDDL HEADER, with the
     16  * fields enclosed by brackets "[]" replaced with your own identifying
     17  * information: Portions Copyright [yyyy] [name of copyright owner]
     18  *
     19  * CDDL HEADER END
     20  */
     21 
     22 /*
     23  * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
     24  * Use is subject to license terms.
     25  */
     26 
     27 	.file	"getcontext.s"
     28 
     29 #include <sys/asm_linkage.h>
     30 
     31 	ANSI_PRAGMA_WEAK(getcontext,function)
     32 	ANSI_PRAGMA_WEAK(swapcontext,function)
     33 
     34 #include "SYS.h"
     35 #include <../assym.h>
     36 
     37 /*
     38  * getcontext() is written in assembler since it has to capture the correct
     39  * machine state of the calle.
     40  *
     41  * As swapcontext() is actually equivalent to getcontext() + setcontext(),
     42  * swapcontext() shares the most code with getcontext().
     43  */
     44 
     45 #define	GETCONTEXT_IMPL(offset)						\
     46 	pushq	%rdi;		/* preserve the ucontext_t pointer */	\
     47 	call	__getcontext;						\
     48 				/* call getcontext: syscall */		\
     49 	popq	%rdx;							\
     50 	andl	%eax, %eax;	/* if (error_return_from_syscall) */	\
     51 	je	1f;							\
     52 	addq	$offset, %rsp;						\
     53 	ret;			/*	then just return */		\
     54 1:									\
     55 	/*								\
     56 	 * fix up %rsp and %rip						\
     57 	 */								\
     58 	addq	$UC_MCONTEXT_GREGS, %rdx;				\
     59 				/* &ucp->uc_mcontext.gregs */		\
     60 	movq	offset+0(%rsp), %rax;					\
     61 				/* read return PC from stack */		\
     62 	movq	%rax, RIP_OFF (%rdx);					\
     63 				/* store ret PC in EIP of env var */	\
     64 	leaq	offset+8(%rsp), %rax;					\
     65 				/* get caller's sp at time of call */	\
     66 	movq	%rax, RSP_OFF (%rdx);					\
     67 				/* store the sp into UESP of env var */	\
     68 	xorq	%rax, %rax;	/* return 0 */				\
     69 	movq	%rax, RAX_OFF (%rdx);					\
     70 				/* getcontext returns 0 after setcontext */
     71 
     72 /*
     73  * getcontext(ucontext_t *ucp)
     74  */
     75 
     76 	ENTRY(getcontext)
     77 	GETCONTEXT_IMPL(0)
     78 	ret
     79 	SET_SIZE(getcontext)
     80 
     81 /*
     82  * swapcontext(ucontext_t *oucp, const ucontext_t *ucp)
     83  */
     84 
     85 	ENTRY(swapcontext)
     86 	pushq	%rsi			/* preserve the 2nd argument */
     87 
     88 	GETCONTEXT_IMPL(8)
     89 
     90 	/* call setcontext */
     91 	popq	%rdi
     92 	call	setcontext
     93 	ret
     94 	SET_SIZE(swapcontext)
     95