FreeBSD/Linux Kernel Cross Reference
sys/i386/i386/vm86bios.s

     /*-
      * Copyright (c) 1998 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.
     *
     * $FreeBSD$
     */
    
    #include <machine/asmacros.h>           /* miscellaneous asm macros */
    #include <machine/trap.h>
    
    #include "assym.inc"
    
    #define SCR_NEWPTD      PCB_ESI         /* readability macros */ 
    #define SCR_VMFRAME     PCB_EBP         /* see vm86.c for explanation */
    #define SCR_STACK       PCB_ESP
    #define SCR_PGTABLE     PCB_EBX
    #define SCR_ARGFRAME    PCB_EIP
    #define SCR_TSS0        PCB_VM86
    #define SCR_TSS1        (PCB_VM86+4)
    
            .data
            ALIGN_DATA
    
            .globl  vm86pcb
    
    vm86pcb:                .long   0
    
            .text
    
    /*
     * vm86_bioscall(struct trapframe_vm86 *vm86)
     */
    ENTRY(vm86_bioscall)
            movl    vm86pcb,%edx            /* scratch data area */
            movl    4(%esp),%eax
            movl    %eax,SCR_ARGFRAME(%edx) /* save argument pointer */
            pushl   %ebx
            pushl   %ebp
            pushl   %esi
            pushl   %edi
            pushl   %gs
    
            movl    PCPU(CURTHREAD),%ecx
            cmpl    %ecx,PCPU(FPCURTHREAD)  /* do we need to save fp? */
            jne     1f
            pushl   %edx
            movl    TD_PCB(%ecx),%ecx
            pushl   PCB_SAVEFPU(%ecx)
            movl    $npxsave,%eax
            call    *%eax
            addl    $4,%esp
            popl    %edx                    /* recover our pcb */
    1:
            movl    SCR_VMFRAME(%edx),%ebx  /* target frame location */
            movl    %ebx,%edi               /* destination */
            movl    SCR_ARGFRAME(%edx),%esi /* source (set on entry) */
            movl    $VM86_FRAMESIZE/4,%ecx  /* sizeof(struct vm86frame)/4 */
            cld
            rep
            movsl                           /* copy frame to new stack */
    
            movl    PCPU(CURPCB),%eax
            pushl   %eax                    /* save curpcb */
            movl    %edx,PCPU(CURPCB)       /* set curpcb to vm86pcb */
    
            movl    PCPU(TSS_GDT),%ebx      /* entry in GDT */
            movl    0(%ebx),%eax
            movl    %eax,SCR_TSS0(%edx)     /* save first word */
            movl    4(%ebx),%eax
            andl    $~0x200, %eax           /* flip 386BSY -> 386TSS */
            movl    %eax,SCR_TSS1(%edx)     /* save second word */
    
            movl    PCB_EXT(%edx),%edi      /* vm86 tssd entry */
            movl    0(%edi),%eax
            movl    %eax,0(%ebx)
            movl    4(%edi),%eax
            movl    %eax,4(%ebx)
            movl    $GPROC0_SEL*8,%esi      /* GSEL(entry, SEL_KPL) */
           ltr     %si
   
           movl    %cr3,%eax
           pushl   %eax                    /* save address space */
           cmpb    $0,pae_mode
           jne     2f
           movl    IdlePTD_nopae,%ecx      /* va (and pa) of Idle PTD */
           jmp     3f
   2:      movl    IdlePTD_pae,%ecx
   3:      movl    %ecx,%ebx
           movl    0(%ebx),%eax
           pushl   %eax                    /* old ptde != 0 when booting */
           pushl   %ebx                    /* keep for reuse */
   
           movl    %esp,SCR_STACK(%edx)    /* save current stack location */
   
           movl    SCR_NEWPTD(%edx),%eax   /* mapping for vm86 page table */
           movl    %eax,0(%ebx)            /* ... install as PTD entry 0 */
   
           cmpb    $0,pae_mode
           je      4f
           movl    IdlePDPT,%ecx
   4:      movl    %ecx,%cr3               /* new page tables */
           movl    SCR_VMFRAME(%edx),%esp  /* switch to new stack */
   
           pushl   %esp
           movl    $vm86_prepcall, %eax
           call    *%eax                   /* finish setup */
           add     $4, %esp
           
           /*
            * Return via doreti
            */
           MEXITCOUNT
           jmp     doreti
   
   
   /*
    * vm86_biosret(struct trapframe_vm86 *vm86)
    */
   ENTRY(vm86_biosret)
           movl    vm86pcb,%edx            /* data area */
   
           movl    4(%esp),%esi            /* source */
           movl    SCR_ARGFRAME(%edx),%edi /* destination */
           movl    $VM86_FRAMESIZE/4,%ecx  /* size */
           cld
           rep
           movsl                           /* copy frame to original frame */
   
           movl    SCR_STACK(%edx),%esp    /* back to old stack */
           popl    %ebx                    /* saved va of Idle PTD */
           popl    %eax
           movl    %eax,0(%ebx)            /* restore old pte */
           popl    %eax
           movl    %eax,%cr3               /* install old page table */
   
           movl    PCPU(TSS_GDT),%ebx              /* entry in GDT */
           movl    SCR_TSS0(%edx),%eax
           movl    %eax,0(%ebx)            /* restore first word */
           movl    SCR_TSS1(%edx),%eax
           movl    %eax,4(%ebx)            /* restore second word */
           movl    $GPROC0_SEL*8,%esi      /* GSEL(entry, SEL_KPL) */
           ltr     %si
           
           popl    PCPU(CURPCB)            /* restore curpcb/curproc */
           movl    SCR_ARGFRAME(%edx),%edx /* original stack frame */
           movl    TF_TRAPNO(%edx),%eax    /* return (trapno) */
   
           popl    %gs
           popl    %edi
           popl    %esi
           popl    %ebp
           popl    %ebx
           ret                             /* back to our normal program */

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