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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 /*	Copyright (c) 1988 AT&T	*/
     28 /*	  All Rights Reserved  	*/
     29 
     30 #pragma ident	"%Z%%M%	%I%	%E% SMI"
     31 
     32 #pragma weak _makecontext = makecontext
     33 #pragma weak ___makecontext_v2 = __makecontext_v2
     34 
     35 #include "lint.h"
     36 #include <stdarg.h>
     37 #include <strings.h>
     38 #include <sys/ucontext.h>
     39 #include <sys/stack.h>
     40 #include <sys/frame.h>
     41 
     42 /*
     43  * The ucontext_t that the user passes in must have been primed with a
     44  * call to getcontext(2), have the uc_stack member set to reflect the
     45  * stack which this context will use, and have the uc_link member set
     46  * to the context which should be resumed when this context returns.
     47  * When makecontext() returns, the ucontext_t will be set to run the
     48  * given function with the given parameters on the stack specified by
     49  * uc_stack, and which will return to the ucontext_t specified by uc_link.
     50  */
     51 
     52 static void resumecontext(void);
     53 
     54 void
     55 makecontext(ucontext_t *ucp, void (*func)(), int argc, ...)
     56 {
     57 	greg_t *reg;
     58 	long *tsp;
     59 	char *sp;
     60 	int argno;
     61 	va_list ap;
     62 	size_t size;
     63 
     64 	reg = ucp->uc_mcontext.gregs;
     65 	reg[REG_PC] = (greg_t)func;
     66 	reg[REG_nPC] = reg[REG_PC] + 0x4;
     67 
     68 	/*
     69 	 * Reserve enough space for a frame and the arguments beyond the
     70 	 * sixth; round to stack alignment.
     71 	 */
     72 	size = sizeof (struct frame);
     73 	size += (argc > 6 ? argc - 6 : 0) * sizeof (long);
     74 
     75 	/*
     76 	 * The legacy implemenation of makecontext() on sparc has been to
     77 	 * interpret the uc_stack.ss_sp member incorrectly as the top of the
     78 	 * stack rather than the base. We preserve this behavior here, but
     79 	 * provide the correct semantics in __makecontext_v2().
     80 	 */
     81 	sp = (char *)(((uintptr_t)ucp->uc_stack.ss_sp - size) &
     82 	    ~(STACK_ALIGN - 1));
     83 
     84 	/*
     85 	 * Copy all args to the stack, and put the first 6 args into the
     86 	 * ucontext_t. Zero the other fields of the frame.
     87 	 */
     88 	/* LINTED pointer cast may result in improper alignment */
     89 	tsp = &((struct frame *)sp)->fr_argd[0];
     90 	bzero(sp, sizeof (struct frame));
     91 
     92 	va_start(ap, argc);
     93 
     94 	for (argno = 0; argno < argc; argno++) {
     95 		if (argno < 6)
     96 			*tsp++ = reg[REG_O0 + argno] = va_arg(ap, long);
     97 		else
     98 			*tsp++ = va_arg(ap, long);
     99 	}
    100 
    101 	va_end(ap);
    102 
    103 	reg[REG_SP] = (greg_t)sp - STACK_BIAS;		/* sp (when done) */
    104 	reg[REG_O7] = (greg_t)resumecontext - 8;	/* return pc */
    105 }
    106 
    107 void
    108 __makecontext_v2(ucontext_t *ucp, void (*func)(), int argc, ...)
    109 {
    110 	greg_t *reg;
    111 	long *tsp;
    112 	char *sp;
    113 	int argno;
    114 	va_list ap;
    115 	size_t size;
    116 
    117 	reg = ucp->uc_mcontext.gregs;
    118 	reg[REG_PC] = (greg_t)func;
    119 	reg[REG_nPC] = reg[REG_PC] + 0x4;
    120 
    121 	/*
    122 	 * Reserve enough space for a frame and the arguments beyond the
    123 	 * sixth; round to stack alignment.
    124 	 */
    125 	size = sizeof (struct frame);
    126 	size += (argc > 6 ? argc - 6 : 0) * sizeof (long);
    127 
    128 	sp = (char *)(((uintptr_t)ucp->uc_stack.ss_sp +
    129 	    ucp->uc_stack.ss_size - size) & ~(STACK_ALIGN - 1));
    130 
    131 	/*
    132 	 * Copy all args to the stack, and put the first 6 args into the
    133 	 * ucontext_t. Zero the other fields of the frame.
    134 	 */
    135 	/* LINTED pointer cast may result in improper alignment */
    136 	tsp = &((struct frame *)sp)->fr_argd[0];
    137 	bzero(sp, sizeof (struct frame));
    138 
    139 	va_start(ap, argc);
    140 
    141 	for (argno = 0; argno < argc; argno++) {
    142 		if (argno < 6)
    143 			*tsp++ = reg[REG_O0 + argno] = va_arg(ap, long);
    144 		else
    145 			*tsp++ = va_arg(ap, long);
    146 	}
    147 
    148 	va_end(ap);
    149 
    150 	reg[REG_SP] = (greg_t)sp - STACK_BIAS;		/* sp (when done) */
    151 	reg[REG_O7] = (greg_t)resumecontext - 8;	/* return pc */
    152 }
    153 
    154 static void
    155 resumecontext(void)
    156 {
    157 	/*
    158 	 * We can't include ucontext.h (where these functions are defined)
    159 	 * because it remaps the symbol makecontext.
    160 	 */
    161 	extern int getcontext(ucontext_t *);
    162 	extern int setcontext(const ucontext_t *);
    163 	ucontext_t uc;
    164 
    165 	(void) getcontext(&uc);
    166 	(void) setcontext(uc.uc_link);
    167 }
    168