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/* Project:     OSLib

 * Description: The OS Construction Kit

 * Date:                1.6.2000

 * Idea by:             Luca Abeni & Gerardo Lamastra

 *

 * OSLib is an SO project aimed at developing a common, easy-to-use

 * low-level infrastructure for developing OS kernels and Embedded

 * Applications; it partially derives from the HARTIK project but it

 * currently is independently developed.

 *

 * OSLib is distributed under GPL License, and some of its code has

 * been derived from the Linux kernel source; also some important

 * ideas come from studying the DJGPP go32 extender.

 *

 * We acknowledge the Linux Community, Free Software Foundation,

 * D.J. Delorie and all the other developers who believe in the

 * freedom of software and ideas.

 *

 * For legalese, check out the included GPL license.

 */

/* File: Vm86.C

 *                             

 * VM86 mode switch routines!

 * This is basically an alternative way of invoking the

 * BIOS service routines; it is very useful to support

 * native VBE compliant Video card, without writing an explicit driver

 */

#include <ll/i386/hw-data.h>

#include <ll/i386/hw-instr.h>

#include <ll/i386/hw-func.h>

#include <ll/i386/mem.h>

#include <ll/i386/x-bios.h>

#include <ll/i386/x-dosmem.h>

#include <ll/i386/cons.h>

#include <ll/i386/error.h>

FILE(VM-86);

/*

#define __LL_DEBUG__

#define __DUMB_CODE__

#define __CHK_IO__

*/

#define __LL_DEBUG__

#define VM86_STACK_SIZE 1024 

extern DWORD ll_irq_table[256];

/* TSS optional section */

static BYTE  vm86_stack0[VM86_STACK_SIZE];

static struct {

    TSS t;

    DWORD io_map[2048];

} vm86_TSS;

static LIN_ADDR vm86_stack;

static LIN_ADDR vm86_iretAddress;

struct registers *global_regs;

#ifdef __DUMB_CODE__

static LIN_ADDR vm86_code;

static BYTE prova86[] = {

                        0x1e,                   /* push ds              */

                        0xb8,0x00,0xb8,         /* mov ax,0xb800        */

                        0x8e,0xd8,              /* mov ds,ax            */

                        0xbf,0x9e,0x00,         /* mov di,0x009e (158)  */

                        0xb0,0x2a,              /* mov ax,'*'           */

                        0x88,0x05,              /* mov ds:[di],al       */

                        0x1f,                   /* pop ds               */

                        0xcd, 0x40,             /*???*/

#ifdef __CHK_IO__               

                        0xb0, 0x00,             /* movb   $0x0,%al*/

                        0x66,0xba, 0x80, 0x00,  /* movw   $0x80,%dx */

                        0x66,0xef,              /* outw %ax, (%dx) */

#endif          

                        0xcf,                   /* iret                 */

                        0xf4,                   /* hlt                  */

                        0};    

#endif

#ifdef __LL_DEBUG__

static BYTE vm86_retAddr[] = {

                        0x1e,                   /* push ds              */

                        0xb8,0x00,0xb8,         /* mov ax,0xb800        */

                        0x8e,0xd8,              /* mov ds,ax            */

                        0xbf,0x3e,0x01,         /* mov di,0x013c (316)  */

                        0xb0,'%',               /* mov ax,'%'           */

                        0x88,0x05,              /* mov ds:[di],al       */

                        0x1f,                   /* pop ds               */

                        0xcd, 0x48};            /* int 0x48             */

#else

static BYTE vm86_retAddr[] = {0xcd, 0x48};      /* int 48h              */

#endif

TSS *vm86_get_tss(void)

{

    return &(vm86_TSS.t);

}

/* This is the return point from V86 mode, called through int 0x48

 * (see vm86-exc.s). We double check that this function is called in

 * the V86 TSS. Otherwise, Panic!!!

 */

void vm86_return(DWORD n, struct registers r)

{

    CONTEXT c = get_TR();

#ifdef __LL_DEBUG__

    DWORD cs,eip;

    void *esp;

    DWORD a;

/*    message("Gotta code=%d [0 called from GPF/1 int 0x48]\n",code);*/

#endif

    if (c == X_VM86_TSS) {

        global_regs = &r;

#ifdef __LL_DEBUG__

        message("TSS CS=%x IP=%lx\n",vm86_TSS.t.cs,vm86_TSS.t.eip);

        message("Switching to %x\n", vm86_TSS.t.back_link);

        a = (DWORD)(vm86_iretAddress);

        cs = (a & 0xFF000) >> 4;

        eip = (a & 0xFFF);

        message("Real-Mode Address is CS=%lx IP=%lx\nLinear=%lx\n",cs,eip,a);

        esp = /* (void *)(tos)*/ (void *)0x69;

        message("Stack frame: %p %lx %lx\n",

                        esp, vm86_TSS.t.esp0, vm86_TSS.t.esp);

        message("%lx ",lmempeekd(esp));         /* bp */

        message("%lx ",lmempeekd(esp+4));       /* eip */

        message("%lx ",lmempeekd(esp+8));       /* 0x0d */

        message("%lx\n",lmempeekd(esp+12));     /* error code */

/* The error code is given by the selector causing shifted and or-ed with

   3 bits: [LDT/GDT | IDT | Ext/Int]

   If IDT == 1 -> the fault was provoked bu an interrupt (Internal if the

   Ext/Int bit is 0, External if the bit is 1)

   Else the LDT/GDT bit shows if the selector belongs to the LDT (if 1)

   or GDT (if 0)  

*/

        message("%lx ",lmempeekd(esp+16));      /* EIP of faulting instr */

        message("%lx ",lmempeekd(esp+20));      /* CS of faulting instr*/

        message("%lx ",lmempeekd(esp+24));      /* EFLAGS*/

        message("%lx\n",lmempeekd(esp+28));     /* old ESP*/

        message("%lx ",lmempeekd(esp+32));      /* old SS*/

        message("%lx ",lmempeekd(esp+36));      /* old ES*/

        message("%lx ",lmempeekd(esp+40));      /* old DS*/

        message("%lx\n",lmempeekd(esp+44));     /* old FS*/

#endif

        ll_context_load(vm86_TSS.t.back_link);

    }

        message("Here?\n");

    halt();

}

extern void vm86_exc(void);

/* Just a debugging function; it dumps the status of the TSS */

void vm86_dump_TSS(void)

{

    BYTE acc,gran;

    DWORD base,lim;

    message("vm86_TSS.t dump\n");

    message("Flag: %lx\n",vm86_TSS.t.eflags);

    message("SS: %hx SP:%lx\n", vm86_TSS.t.ss,vm86_TSS.t.esp);

    message("Stack0: %hx:%lx\n",vm86_TSS.t.ss0,vm86_TSS.t.esp0);

    message("Stack1: %hx:%lx\n",vm86_TSS.t.ss1,vm86_TSS.t.esp1);

    message("Stack2: %hx:%lx\n",vm86_TSS.t.ss2,vm86_TSS.t.esp2);

    message("CS: %hx IP: %lx",vm86_TSS.t.cs, vm86_TSS.t.eip);

    message("DS: %hx\n",vm86_TSS.t.ds);

    base = GDT_read(X_VM86_TSS,&lim,&acc,&gran);

    message("Base : %lx Lim : %lx Acc : %x Gran %x\n",

                    base,lim,(unsigned)(acc),(unsigned)(gran));

}

void vm86_init(void)

{

    int register i;

    /* Init the DOS memory allocator */

    DOS_mem_init();

    /* First of all, we need to setup a GDT entries to

     * allow vm86 task execution. We just need a free 386 TSS, which

     * will be used to store the execution context of the virtual 8086

     * task

     */

    GDT_place(X_VM86_TSS,(DWORD)(&vm86_TSS),

              sizeof(vm86_TSS),FREE_TSS386,GRAN_16);

    IDT_place(0x48, (void *)(vm86_return));

    /* Prepare a real-mode stack, obtaining it from the

     * DOS memory allocator!

     * 8K should be OK! Stack top is vm86_stack + SIZE!

     */

    vm86_stack = DOS_alloc(VM86_STACK_SIZE*2);

    vm86_stack += VM86_STACK_SIZE/2;

    /* Create a location of DOS memory containing the

     * opcode sequence which will generate a GPF

     * We use the privileged instruction hlt to do it

     */

    vm86_iretAddress = DOS_alloc(sizeof(vm86_retAddr));

    memcpy(vm86_iretAddress,vm86_retAddr,sizeof(vm86_retAddr));

#ifdef __LL_DEBUG__

    message("PM reentry linear address=0x%lx\n", (DWORD)vm86_iretAddress);

#endif

#ifdef __DUMB_CODE__

    vm86_code = DOS_alloc(2048);

    lmemcpy(vm86_code,prova86,sizeof(prova86));

#endif

    /* Zero the PM/Ring[1,2] ss:esp; they're unused! */

    vm86_TSS.t.esp1 = 0;

    vm86_TSS.t.esp2 = 0;

    vm86_TSS.t.ss1 = 0;

    vm86_TSS.t.ss2 = 0;

    /* Use only the GDT */

    vm86_TSS.t.ldt = 0;

    /* No paging activated */

    vm86_TSS.t.cr3 = 0;

    vm86_TSS.t.trap = 0;

    /* Yeah, free access to any I/O port; we trust BIOS anyway! */

    /* Here is the explanation: we have 65536 I/O ports... each bit

     * in the io_map masks/unmasks the exception for the given I/O port

     * If the bit is set, an exception is generated; otherwise, if the bit

     * is clear, everythings works fine...

     * Because of alignment problem, we need to add an extra byte all set

     * to 1, according to Intel manuals

     */

    vm86_TSS.t.io_base = (DWORD)(&(vm86_TSS.io_map)) -

                        (DWORD)(&(vm86_TSS));

    for (i = 0; i < 2047; i++) vm86_TSS.io_map[i] = 0;

    vm86_TSS.io_map[2047] = 0xFF000000;

}

int vm86_callBIOS(int service,X_REGS16 *in,X_REGS16 *out,X_SREGS16 *s)

{

    DWORD vm86_tmpAddr;

    DWORD vm86_flags, vm86_cs,vm86_ip;

    LIN_ADDR vm86_stackPtr;

    DWORD *IRQTable_entry;

    if (service < 0x10 || in == NULL) return -1;

    /* Setup the stack frame */

    vm86_tmpAddr = (DWORD)(vm86_stack);

    vm86_TSS.t.ss = (vm86_tmpAddr & 0xFF000) >> 4;

    vm86_TSS.t.ebp = vm86_TSS.t.esp = (vm86_tmpAddr & 0x0FFF)

                + VM86_STACK_SIZE - 6;

    /* Build an iret stack frame which returns to vm86_iretAddress */

    vm86_tmpAddr = (DWORD)(vm86_iretAddress);

    vm86_cs = (vm86_tmpAddr & 0xFF000) >> 4;

    vm86_ip = (vm86_tmpAddr & 0xFFF);

    vm86_flags = 0; /* CPU_FLAG_VM | CPU_FLAG_IOPL; */

    vm86_stackPtr = vm86_stack + VM86_STACK_SIZE;

    lmempokew(vm86_stackPtr-6,vm86_ip);

    lmempokew(vm86_stackPtr-4,vm86_cs);

    lmempokew(vm86_stackPtr-2,vm86_flags);

#ifdef __LL_DEBUG__

    message("Stack: %lx SS: %lx SP: %lx\n",

        vm86_tmpAddr + VM86_STACK_SIZE,(DWORD)vm86_TSS.t.ss,vm86_TSS.t.esp);

#endif

    /* Wanted VM86 mode + IOPL = 3! */

    vm86_TSS.t.eflags = CPU_FLAG_VM | CPU_FLAG_IOPL;

    /* Preload some standard values into the registers */

    vm86_TSS.t.ss0 = X_FLATDATA_SEL;

    vm86_TSS.t.esp0 = (DWORD)&(vm86_stack0[VM86_STACK_SIZE-1]);

#ifdef __DUMB_CODE__

    vm86_TSS.t.cs = ((DWORD)(vm86_code) & 0xFFFF0) >> 4;

    vm86_TSS.t.eip = ((DWORD)(vm86_code) & 0x000F);

#ifdef __LL_DEBUG_

    message("(DUMB CODE) CS:%x IP:%x/%x\n",

        (DWORD)vm86_TSS.t.cs,vm86_TSS.t.eip,&prova86);

    message("(DUMB CODE) Go...\n");

#endif

    vm86_TSS.t.back_link = ll_context_save();

    ll_context_load(X_VM86_TSS);

#ifdef __LL_DEBUG_

    message("(DUMB CODE) I am back...\n");

#endif

#else

    /* Copy the parms from the X_*REGS structures in the vm86 TSS */

    vm86_TSS.t.eax = (DWORD)in->x.ax;

    vm86_TSS.t.ebx = (DWORD)in->x.bx;

    vm86_TSS.t.ecx = (DWORD)in->x.cx;

    vm86_TSS.t.edx = (DWORD)in->x.dx;

    vm86_TSS.t.esi = (DWORD)in->x.si;

    vm86_TSS.t.edi = (DWORD)in->x.di;

    /* IF Segment registers are required, copy them... */

    if (s != NULL) {

        vm86_TSS.t.es = (WORD)s->es;

        vm86_TSS.t.ds = (WORD)s->ds;

    } else {

        vm86_TSS.t.ds = vm86_TSS.t.ss;

        vm86_TSS.t.es = vm86_TSS.t.ss;

    }

    vm86_TSS.t.gs = vm86_TSS.t.ss;

    vm86_TSS.t.fs = vm86_TSS.t.ss;

    /* Execute the BIOS call, fetching the CS:IP of the real interrupt

     * handler from 0:0 (DOS irq table!)

     */

    IRQTable_entry = (void *)(0L);

    vm86_TSS.t.cs= ((IRQTable_entry[service]) & 0xFFFF0000) >> 16;

    vm86_TSS.t.eip = ((IRQTable_entry[service]) & 0x0000FFFF);

#ifdef __LL_DEBUG__    

    message("CS:%x IP:%lx\n", vm86_TSS.t.cs, vm86_TSS.t.eip);

#endif

    /* Let's use the ll standard call... */

    vm86_TSS.t.back_link = ll_context_save();

    ll_context_load(X_VM86_TSS);

#ifdef __LL_DEBUG__    

    message("I am back...\n");

    message("TSS CS=%hx IP=%lx\n", vm86_TSS.t.cs, vm86_TSS.t.eip);

    { char *xp = (char *)(vm86_iretAddress + 0xe);

      message("PM reentry linear address=%p\n", vm86_iretAddress);

      message("Executing code: %x ",(unsigned char)(*xp)); xp++;

      message("%x\n",(unsigned char)(*xp));}

#endif

    /* Send back in the X_*REGS structure the value obtained with

     * the real-mode interrupt call

     */

    if (out != NULL) {

/*

      out->x.ax = (WORD)vm86_TSS.t.eax;

      out->x.bx = (WORD)vm86_TSS.t.ebx;

      out->x.cx = (WORD)vm86_TSS.t.ecx;

      out->x.dx = (WORD)vm86_TSS.t.edx;

      out->x.si = (WORD)vm86_TSS.t.esi;

      out->x.di = (WORD)vm86_TSS.t.edi;

      out->x.cflag = (WORD)vm86_TSS.t.eflags;

*/

      out->x.ax = global_regs->eax;

      out->x.bx = global_regs->ebx;

      out->x.cx = global_regs->ecx;

      out->x.dx = global_regs->edx;

      out->x.si = global_regs->esi;

      out->x.di = global_regs->edi;

      out->x.cflag = global_regs->flags;

    }

    if (s != NULL) {

      s->es = vm86_TSS.t.es;

      s->ds = vm86_TSS.t.ds;

    }

#endif

    return 1;

}