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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                  */
    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

/* 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;
}