/*-
 * 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.
 */

#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
         */
        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 */