amd64/gen/makectxt.c

	makectxt.c revision 7257d1b4d25bfac0c802847390e98a464fd787ac
/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */

/*
 * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

/*  Copyright (c) 1988 AT&T */
/*    All Rights Reserved   */

#pragma ident   "%Z%%M% %I% %E% SMI"

#pragma weak _makecontext = makecontext

#include "lint.h"
#include <stdarg.h>
#include <ucontext.h>
#include <sys/stack.h>

/*
 * The ucontext_t that the user passes in must have been primed with a
 * call to getcontext(2), have the uc_stack member set to reflect the
 * stack which this context will use, and have the uc_link member set
 * to the context which should be resumed when this context returns.
 * When makecontext() returns, the ucontext_t will be set to run the
 * given function with the given parameters on the stack specified by
 * uc_stack, and which will return to the ucontext_t specified by uc_link.
 */

static void resumecontext(void);

void
makecontext(ucontext_t *ucp, void (*func)(), int argc, ...)
{
    long *sp;
    long *tsp;
    va_list ap;
    size_t size;
    int pusharg = (argc > 6 ? argc - 6 : 0);
    greg_t tmp;
    int i;

    ucp->uc_mcontext.gregs[REG_PC] = (greg_t)func;

    size = sizeof (long) * (pusharg + 1);

    /*
     * Calculate new value for %rsp. On entry to a function,
     * %rsp must be STACK_ENTRY_ALIGNed but not STACK_ALIGNed.
     * This is because the pushq %rbp will correct the alignment.
     */

    sp = (long *)(((uintptr_t)ucp->uc_stack.ss_sp +
        ucp->uc_stack.ss_size - size) & ~(STACK_ENTRY_ALIGN - 1));

    if (((uintptr_t)sp & (STACK_ALIGN - 1ul)) == 0)
        sp -= STACK_ENTRY_ALIGN / sizeof (*sp);

    tsp = sp + 1;

    va_start(ap, argc);

    for (i = 0; i < argc; i++) {
        tmp = va_arg(ap, long);
        switch (i) {
        case 0:
            ucp->uc_mcontext.gregs[REG_RDI] = tmp;
            break;
        case 1:
            ucp->uc_mcontext.gregs[REG_RSI] = tmp;
            break;
        case 2:
            ucp->uc_mcontext.gregs[REG_RDX] = tmp;
            break;
        case 3:
            ucp->uc_mcontext.gregs[REG_RCX] = tmp;
            break;
        case 4:
            ucp->uc_mcontext.gregs[REG_R8] = tmp;
            break;
        case 5:
            ucp->uc_mcontext.gregs[REG_R9] = tmp;
            break;
        default:
            *tsp++ = tmp;
            break;
        }
    }

    va_end(ap);

    *sp = (long)resumecontext;      /* return address */

    ucp->uc_mcontext.gregs[REG_SP] = (greg_t)sp;
}


static void
resumecontext(void)
{
    ucontext_t uc;

    (void) getcontext(&uc);
    (void) setcontext(uc.uc_link);
}