The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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FreeBSD/Linux Kernel Cross Reference
sys/i386/i386/bioscall.s

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    1 /*-
    2  * Copyright (c) 1997 Jonathan Lemon
    3  * All rights reserved.
    4  *
    5  * Redistribution and use in source and binary forms, with or without
    6  * modification, are permitted provided that the following conditions
    7  * are met:
    8  * 1. Redistributions of source code must retain the above copyright
    9  *    notice, this list of conditions and the following disclaimer.
   10  * 2. Redistributions in binary form must reproduce the above copyright
   11  *    notice, this list of conditions and the following disclaimer in the
   12  *    documentation and/or other materials provided with the distribution.
   13  *
   14  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
   15  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   16  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   17  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
   18  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   19  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   20  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   21  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   22  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   23  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   24  * SUCH DAMAGE.
   25  *
   26  * $FreeBSD: releng/9.0/sys/i386/i386/bioscall.s 103436 2002-09-17 01:49:00Z peter $
   27  */
   28 
   29 /*
   30  * Functions for calling x86 BIOS functions from the BSD kernel
   31  */
   32         
   33 #include <machine/asmacros.h>
   34 
   35 #include "assym.s"
   36 
   37         .data
   38         ALIGN_DATA
   39 bioscall_frame:         .long   0
   40 bioscall_stack:         .long   0
   41 
   42         .text
   43 /*
   44  * bios32(regs, offset, segment)
   45  *      struct bios_regs *regs;
   46  *      u_int offset;
   47  *      u_short segment;
   48  */
   49 ENTRY(bios32)
   50         pushl   %ebp
   51         movl    16(%esp),%ebp
   52         mov     %bp,bioscall_vector+4
   53         movl    12(%esp),%ebp
   54         movl    %ebp,bioscall_vector
   55         movl    8(%esp),%ebp
   56         pushl   %ebx
   57         pushl   %esi
   58         pushl   %edi
   59         movl    0(%ebp),%eax
   60         movl    4(%ebp),%ebx
   61         movl    8(%ebp),%ecx
   62         movl    12(%ebp),%edx
   63         movl    16(%ebp),%esi
   64         movl    20(%ebp),%edi
   65         pushl   %ebp
   66         lcall   *bioscall_vector
   67         popl    %ebp
   68         movl    %eax,0(%ebp)
   69         movl    %ebx,4(%ebp)
   70         movl    %ecx,8(%ebp)
   71         movl    %edx,12(%ebp)
   72         movl    %esi,16(%ebp)
   73         movl    %edi,20(%ebp)
   74         movl    $0,%eax                 /* presume success */
   75         jnc     1f
   76         movl    $1,%eax                 /* nope */
   77 1:
   78         popl    %edi
   79         popl    %esi
   80         popl    %ebx
   81         popl    %ebp
   82         ret
   83 
   84 
   85 /*
   86  * bios16_call(regs, stack)
   87  *      struct bios_regs *regs;
   88  *      char *stack;
   89  */
   90 ENTRY(bios16_call)
   91         pushl   %ebp
   92         movl    %esp,%ebp
   93         addl    $4,%ebp                 /* frame pointer */
   94         movl    %ebp,bioscall_frame     /* ... save it */
   95         pushl   %ebx
   96         pushl   %esi
   97         pushl   %edi
   98 /*
   99  * the problem with a full 32-bit stack segment is that 16-bit code
  100  * tends to do a pushf, which only pushes %sp, not %esp.  This value
  101  * is then popped off (into %esp) which causes a page fault because 
  102  * it is the wrong address.
  103  *
  104  * the reverse problem happens for 16-bit stack addresses; the kernel
  105  * code attempts to get the address of something on the stack, and the
  106  * value returned is the address relative to %ss, not %ds.
  107  *
  108  * we fix this by installing a temporary stack at page 0, so the
  109  * addresses are always valid in both 32 bit and 16 bit modes.
  110  */
  111         movl    %esp,bioscall_stack     /* save current stack location */
  112         movl    8(%ebp),%esp            /* switch to page 0 stack */
  113 
  114         movl    4(%ebp),%ebp            /* regs */
  115 
  116         movl    0(%ebp),%eax
  117         movl    4(%ebp),%ebx
  118         movl    8(%ebp),%ecx
  119         movl    12(%ebp),%edx
  120         movl    16(%ebp),%esi
  121         movl    20(%ebp),%edi
  122 
  123         pushl   $BC32SEL
  124         leal    CNAME(bios16_jmp),%ebp
  125         andl    $PAGE_MASK,%ebp
  126         pushl   %ebp                    /* reload %cs and */
  127         lret                            /* ...continue below */
  128         .globl  CNAME(bios16_jmp)
  129 CNAME(bios16_jmp):
  130         lcallw  *bioscall_vector        /* 16-bit call */
  131 
  132         jc      1f
  133         pushl   $0                      /* success */
  134         jmp     2f
  135 1:
  136         pushl   $1                      /* failure */
  137 2:
  138         movl    bioscall_frame,%ebp
  139 
  140         movl    4(%ebp),%ebp            /* regs */
  141 
  142         movl    %eax,0(%ebp)
  143         movl    %ebx,4(%ebp)
  144         movl    %ecx,8(%ebp)
  145         movl    %edx,12(%ebp)
  146         movl    %esi,16(%ebp)
  147         movl    %edi,20(%ebp)
  148 
  149         popl    %eax                    /* recover return value */
  150         movl    bioscall_stack,%esp     /* return to normal stack */
  151 
  152         popl    %edi
  153         popl    %esi
  154         popl    %ebx
  155         popl    %ebp
  156 
  157         movl    (%esp),%ecx
  158         pushl   %ecx                    /* return address */
  159         movl    $KCSEL,4(%esp)
  160         lret                            /* reload %cs on the way out */

Cache object: ba226af3e8bd4edebf386eb08bb03119


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