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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() and swapcontext() are written in assembler since it has to
     39  * capture the correct machine state of the caller, including
     40  * the registers: %edi, %esi and %ebx.
     41  *
     42  * As swapcontext() is actually equivalent to getcontext() + setcontext(),
     43  * swapcontext() shares the most code with getcontext().
     44  */
     45 
     46 
     47 #define	GETCONTEXT_IMPL							\
     48 	movl	4(%esp), %eax;		/* %eax <-- first arg: ucp */	\
     49 	pushl	%eax;			/* push ucp for system call */	\
     50 	call	__getcontext;		/* call getcontext: syscall */	\
     51 	addl	$4, %esp;		/* pop arg */			\
     52 	andl	%eax, %eax;		/* if (err_ret_from_syscall) */	\
     53 	je	1f;							\
     54 	ret;				/*	then return */		\
     55 1:									\
     56 	movl	4(%esp), %eax;		/* recompute first arg */	\
     57 	/*								\
     58 	 * fix up %esp and %eip						\
     59 	 */								\
     60 	leal	UC_MCONTEXT_GREGS (%eax), %edx;				\
     61 				/* %edx <-- &ucp->uc_mcontext.gregs */	\
     62 	movl	0(%esp), %eax;	/* read return PC from stack */		\
     63 	movl	%eax, EIP_OFF (%edx);					\
     64 				/* store ret PC in EIP of env var */	\
     65 	leal	4(%esp), %eax;	/* get caller's sp at time of call */	\
     66 	movl	%eax, UESP_OFF (%edx);					\
     67 				/* store the sp into UESP of env var */	\
     68 	xorl	%eax, %eax;	/* return 0 */				\
     69 	movl	%eax, EAX_OFF (%edx);					\
     70 				/* getcontext returns 0 after a setcontext */
     71 
     72 /*
     73  * getcontext(ucontext_t *ucp)
     74  */
     75 	ENTRY(getcontext)
     76 	GETCONTEXT_IMPL
     77 	ret
     78 	SET_SIZE(getcontext)
     79 
     80 
     81 /*
     82  * swapcontext(ucontext_t *oucp, const ucontext_t *ucp)
     83  */
     84 	ENTRY(swapcontext)
     85 	GETCONTEXT_IMPL
     86 	/ call setcontext
     87 	movl	8(%esp), %eax		/* %eax <-- second arg: ucp */
     88 	pushl	%eax			/* push ucp for setcontext */
     89 	call	setcontext
     90 	addl	$4, %esp		/* pop arg: just in case */
     91 	ret
     92 	SET_SIZE(swapcontext)
     93