/*-
 * Copyright (c) 1997 Jonathan Lemon
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

/*
 * Functions for calling x86 BIOS functions from the BSD kernel
 */
        
#include <machine/asmacros.h>

#include "assym.inc"

        .data
        ALIGN_DATA
bioscall_frame:         .long   0
bioscall_stack:         .long   0

        .text
/*
 * bios32(regs, offset, segment)
 *      struct bios_regs *regs;
 *      u_int offset;
 *      u_short segment;
 */
ENTRY(bios32)
        pushl   %ebp
        movl    16(%esp),%ebp
        mov     %bp,bioscall_vector+4
        movl    12(%esp),%ebp
        movl    %ebp,bioscall_vector
        movl    8(%esp),%ebp
        pushl   %ebx
        pushl   %esi
        pushl   %edi
        movl    0(%ebp),%eax
        movl    4(%ebp),%ebx
        movl    8(%ebp),%ecx
        movl    12(%ebp),%edx
        movl    16(%ebp),%esi
        movl    20(%ebp),%edi
        pushl   %ebp
        lcall   *bioscall_vector
        popl    %ebp
        movl    %eax,0(%ebp)
        movl    %ebx,4(%ebp)
        movl    %ecx,8(%ebp)
        movl    %edx,12(%ebp)
        movl    %esi,16(%ebp)
        movl    %edi,20(%ebp)
        movl    $0,%eax                 /* presume success */
        jnc     1f
        movl    $1,%eax                 /* nope */
1:
        popl    %edi
        popl    %esi
        popl    %ebx
        popl    %ebp
        ret


/*
 * bios16_call(regs, stack)
 *      struct bios_regs *regs;
 *      char *stack;
 */
ENTRY(bios16_call)
        pushl   %ebp
        movl    %esp,%ebp
        addl    $4,%ebp                 /* frame pointer */
        movl    %ebp,bioscall_frame     /* ... save it */
        pushl   %ebx
        pushl   %esi
        pushl   %edi
/*
 * the problem with a full 32-bit stack segment is that 16-bit code
 * tends to do a pushf, which only pushes %sp, not %esp.  This value
 * is then popped off (into %esp) which causes a page fault because 
 * it is the wrong address.
 *
 * the reverse problem happens for 16-bit stack addresses; the kernel
 * code attempts to get the address of something on the stack, and the
 * value returned is the address relative to %ss, not %ds.
 *
 * we fix this by installing a temporary stack at page 0, so the
 * addresses are always valid in both 32 bit and 16 bit modes.
 */
        movl    %esp,bioscall_stack     /* save current stack location */
        movl    8(%ebp),%esp            /* switch to page 0 stack */

        movl    4(%ebp),%ebp            /* regs */

        movl    0(%ebp),%eax
        movl    4(%ebp),%ebx
        movl    8(%ebp),%ecx
        movl    12(%ebp),%edx
        movl    16(%ebp),%esi
        movl    20(%ebp),%edi

        pushl   $BC32SEL
        leal    CNAME(bios16_jmp),%ebp
        andl    $PAGE_MASK,%ebp
        pushl   %ebp                    /* reload %cs and */
        lret                            /* ...continue below */
        .globl  CNAME(bios16_jmp)
CNAME(bios16_jmp):
        lcallw  *bioscall_vector        /* 16-bit call */

        jc      1f
        pushl   $0                      /* success */
        jmp     2f
1:
        pushl   $1                      /* failure */
2:
        movl    bioscall_frame,%ebp

        movl    4(%ebp),%ebp            /* regs */

        movl    %eax,0(%ebp)
        movl    %ebx,4(%ebp)
        movl    %ecx,8(%ebp)
        movl    %edx,12(%ebp)
        movl    %esi,16(%ebp)
        movl    %edi,20(%ebp)

        popl    %eax                    /* recover return value */
        movl    bioscall_stack,%esp     /* return to normal stack */

        popl    %edi
        popl    %esi
        popl    %ebx
        popl    %ebp

        movl    (%esp),%ecx
        pushl   %ecx                    /* return address */
        movl    $KCSEL,4(%esp)
        lret                            /* reload %cs on the way out */

        .section .note.GNU-stack,"",%progbits