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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/mem.h>

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

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

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

#include <ll/i386/cons.h>

#include <ll/i386/error.h>

FILE(VM - 86);

/*

#define __LL_DEBUG__

#define __DUMB_CODE__

#define __CHK_IO__

*/

#define VM86_STACK_SIZE 1024

/* 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;

DWORD *GLOBesp;

#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                  */

};

#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

/* 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 * tos)

{

    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) {

        GLOBesp = tos;

#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);

        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);

    }

    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, vm86_exc);

    /* 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=%p\n", 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:%hx 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;

*/

#ifdef __LL_DEBUG__

        message("%x\n", (WORD) * (GLOBesp));

        message("%x\n", (WORD) * (GLOBesp + 1));

        /*EDI*/ message("%x\n", (WORD) * (GLOBesp + 2));

        /*ESI*/ message("%x\n", (WORD) * (GLOBesp + 3));

        /*EBP*/ message("%x\n", (WORD) * (GLOBesp + 4));

        /*ESP*/ message("%x\n", (WORD) * (GLOBesp + 5));

        /*EBX*/ message("%x\n", (WORD) * (GLOBesp + 6));

        /*EDX*/

#endif

            out->x.ax = (WORD) * (GLOBesp + 8);

        out->x.bx = (WORD) * (GLOBesp + 5);

        out->x.cx = (WORD) * (GLOBesp + 7);

        out->x.dx = (WORD) * (GLOBesp + 6);

        out->x.si = (WORD) * (GLOBesp + 2);

        out->x.di = (WORD) * (GLOBesp + 1);

        out->x.cflag = (WORD) * (GLOBesp);

    }

    if (s != NULL) {

        s->es = vm86_TSS.t.es;

        s->ds = vm86_TSS.t.ds;

    }

#endif

    return 1;

}