/*
 * 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 2004 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

        .file   "_stack_grow.s"

/*
 * void *
 * _stack_grow(void *addr)
 * {
 *      uintptr_t base = (uintptr_t)curthread->ul_ustack.ss_sp;
 *      size_t size = curthread->ul_ustack.ss_size;
 *
 *      if (size > (uintptr_t)addr - base)
 *              return (addr);
 *
 *      if (size == 0)
 *              return (addr);
 *
 *      if (size > %sp - base)
 *              %sp = base - STACK_ALIGN;
 *
 *      *((char *)(base - 1));
 *
 *      _lwp_kill(_lwp_self(), SIGSEGV);
 * }
 */

#include "SYS.h"
#include <assym.h>

        ENTRY(_stack_grow)
        movl    4(%esp), %eax
        movl    %gs:UL_USTACK+SS_SP, %ecx
        movl    %gs:UL_USTACK+SS_SIZE, %edx
        movl    %eax, %ebx
        subl    %ecx, %ebx
        cmpl    %edx, %ebx
        jae     1f
        ret
1:
        /
        / If the stack size is 0, stack checking is disabled.
        /
        cmpl    $0, %edx
        jne     2f
        ret
2:
        /
        / Move the stack pointer outside the stack bounds if it isn't already.
        /
        movl    %esp, %ebx
        subl    %ecx, %ebx
        cmpl    %edx, %ebx
        jae     3f
        pushl   %ebp
        movl    %esp, %ebp
        movl    %ecx, %esp
        subl    $STACK_ALIGN, %esp
3:
        /
        / Dereference an address in the guard page.
        /
        movb    -1(%ecx), %bl

        /
        / If the above load doesn't raise a SIGSEGV then do it ourselves.
        /
        SYSTRAP_RVAL1(lwp_self)
        pushl   $SIGSEGV
        pushl   %eax
        pushl   $0
        SYSTRAP_RVAL1(lwp_kill)
        addl    $12, %esp

        /
        / Try one last time to take out the process.
        /
        movl    0x0, %eax
        SET_SIZE(_stack_grow)