/*
 * DPMI 0.9 emulation
 *
 * Copyright 1995 Alexandre Julliard
 */

#include <unistd.h>
#include <string.h>
#include "windef.h"
#include "wine/winbase16.h"
#include "ldt.h"
#include "global.h"
#include "module.h"
#include "miscemu.h"
#include "msdos.h"
#include "task.h"
#include "thread.h"	/* for !MZ_SUPPORTED */
#include "stackframe.h"	/* for !MZ_SUPPORTED */
#include "toolhelp.h"
#include "selectors.h"
#include "process.h"
#include "callback.h"
#include "debugtools.h"

DEFAULT_DEBUG_CHANNEL(int31)

#define DOS_GET_DRIVE(reg) ((reg) ? (reg) - 1 : DRIVE_GetCurrentDrive())

void CreateBPB(int drive, BYTE *data, BOOL16 limited);  /* defined in int21.c */

static void* lastvalloced = NULL;

/* Structure for real-mode callbacks */
typedef struct
{
    DWORD edi;
    DWORD esi;
    DWORD ebp;
    DWORD reserved;
    DWORD ebx;
    DWORD edx;
    DWORD ecx;
    DWORD eax;
    WORD  fl;
    WORD  es;
    WORD  ds;
    WORD  fs;
    WORD  gs;
    WORD  ip;
    WORD  cs;
    WORD  sp;
    WORD  ss;
} REALMODECALL;


typedef struct tagRMCB {
    DWORD address;
    DWORD proc_ofs,proc_sel;
    DWORD regs_ofs,regs_sel;
    struct tagRMCB *next;
} RMCB;

static RMCB *FirstRMCB = NULL;

UINT16 DPMI_wrap_seg;

/**********************************************************************
 *	    DPMI_xalloc
 * special virtualalloc, allocates lineary monoton growing memory.
 * (the usual VirtualAlloc does not satisfy that restriction)
 */
static LPVOID
DPMI_xalloc(int len) {
	LPVOID	ret;
	LPVOID	oldlastv = lastvalloced;

	if (lastvalloced) {
		int	xflag = 0;
		ret = NULL;
		while (!ret) {
			ret=VirtualAlloc(lastvalloced,len,MEM_COMMIT|MEM_RESERVE,PAGE_EXECUTE_READWRITE);
			if (!ret)
				lastvalloced = (char *) lastvalloced + 0x10000;
			/* we failed to allocate one in the first round. 
			 * try non-linear
			 */
			if (!xflag && (lastvalloced<oldlastv)) { /* wrapped */
				FIXME("failed to allocate lineary growing memory (%d bytes), using non-linear growing...\n",len);
				xflag++;
			}
			/* if we even fail to allocate something in the next 
			 * round, return NULL
			 */
			if ((xflag==1) && (lastvalloced >= oldlastv))
				xflag++;
			if ((xflag==2) && (lastvalloced < oldlastv)) {
				FIXME("failed to allocate any memory of %d bytes!\n",len);
				return NULL;
			}
		}
	} else
		 ret=VirtualAlloc(NULL,len,MEM_COMMIT|MEM_RESERVE,PAGE_EXECUTE_READWRITE);
	lastvalloced = (LPVOID)(((DWORD)ret+len+0xffff)&~0xffff);
	return ret;
}

static void
DPMI_xfree(LPVOID ptr) {
	VirtualFree(ptr,0,MEM_RELEASE);
}

/* FIXME: perhaps we could grow this mapped area... */
static LPVOID
DPMI_xrealloc(LPVOID ptr,int newsize) {
	MEMORY_BASIC_INFORMATION	mbi;
	LPVOID				newptr;

	newptr = DPMI_xalloc(newsize);
	if (ptr) {
		if (!VirtualQuery(ptr,&mbi,sizeof(mbi))) {
			FIXME("realloc of DPMI_xallocd region %p?\n",ptr);
			return NULL;
		}
		if (mbi.State == MEM_FREE) {
			FIXME("realloc of DPMI_xallocd region %p?\n",ptr);
			return NULL;
		}
		/* We do not shrink allocated memory. most reallocs
		 * only do grows anyway
		 */
		if (newsize<=mbi.RegionSize)
			return ptr;
		memcpy(newptr,ptr,mbi.RegionSize);
		DPMI_xfree(ptr);
	}
	return newptr;
}
/**********************************************************************
 *	    INT_GetRealModeContext
 */
static void INT_GetRealModeContext( REALMODECALL *call, CONTEXT86 *context )
{
    EAX_reg(context) = call->eax;
    EBX_reg(context) = call->ebx;
    ECX_reg(context) = call->ecx;
    EDX_reg(context) = call->edx;
    ESI_reg(context) = call->esi;
    EDI_reg(context) = call->edi;
    EBP_reg(context) = call->ebp;
    EFL_reg(context) = call->fl | V86_FLAG;
    EIP_reg(context) = call->ip;
    ESP_reg(context) = call->sp;
    CS_reg(context)  = call->cs;
    DS_reg(context)  = call->ds;
    ES_reg(context)  = call->es;
    FS_reg(context)  = call->fs;
    GS_reg(context)  = call->gs;
    SS_reg(context)  = call->ss;
    V86BASE(context) = (DWORD) DOSMEM_MemoryBase(0);
}


/**********************************************************************
 *	    INT_SetRealModeContext
 */
static void INT_SetRealModeContext( REALMODECALL *call, CONTEXT86 *context )
{
    call->eax = EAX_reg(context);
    call->ebx = EBX_reg(context);
    call->ecx = ECX_reg(context);
    call->edx = EDX_reg(context);
    call->esi = ESI_reg(context);
    call->edi = EDI_reg(context);
    call->ebp = EBP_reg(context);
    call->fl  = LOWORD(EFL_reg(context));
    call->ip  = LOWORD(EIP_reg(context));
    call->sp  = LOWORD(ESP_reg(context));
    call->cs  = CS_reg(context);
    call->ds  = DS_reg(context);
    call->es  = ES_reg(context);
    call->fs  = FS_reg(context);
    call->gs  = GS_reg(context);
    call->ss  = SS_reg(context);
}


/**********************************************************************
 *	    DPMI_CallRMCBProc
 *
 * This routine does the hard work of calling a callback procedure.
 */
static void DPMI_CallRMCBProc( CONTEXT86 *context, RMCB *rmcb, WORD flag )
{
    if (IS_SELECTOR_SYSTEM( rmcb->proc_sel )) {
        /* Wine-internal RMCB, call directly */
        ((RMCBPROC)rmcb->proc_ofs)(context);
    } else {
#ifdef __i386__
        UINT16 ss,es;
        DWORD edi;

        INT_SetRealModeContext((REALMODECALL *)PTR_SEG_OFF_TO_LIN( rmcb->regs_sel, rmcb->regs_ofs ), context);
        ss = SELECTOR_AllocBlock( DOSMEM_MemoryBase(0) + (DWORD)(SS_reg(context)<<4), 0x10000, SEGMENT_DATA, FALSE, FALSE );

        FIXME("untested!\n");

        /* The called proc ends with an IRET, and takes these parameters:
         * DS:ESI = pointer to real-mode SS:SP
         * ES:EDI = pointer to real-mode call structure
         * It returns:
         * ES:EDI = pointer to real-mode call structure (may be a copy)
         * It is the proc's responsibility to change the return CS:IP in the
         * real-mode call structure. */
        if (flag & 1) {
	    int _clobber;
            /* 32-bit DPMI client */
            __asm__ __volatile__(
                 "pushl %%es\n"
                 "pushl %%ds\n"
                 "pushfl\n"
                 "movl %5,%%es\n"
                 "movl %4,%%ds\n"
                 "lcall %3\n"
                 "popl %%ds\n"
                 "movl %%es,%0\n"
                 "popl %%es\n"
             : "=g" (es), "=D" (edi), "=S" (_clobber)
             : "m" (rmcb->proc_ofs),
               "g" (ss), "g" (rmcb->regs_sel),
               "S" (ESP_reg(context)), "1" (rmcb->regs_ofs)
             : "ecx", "edx", "ebp" );
        } else {
            /* 16-bit DPMI client */
            CONTEXT86 ctx = *context;
            CS_reg(&ctx) = rmcb->proc_sel;
            EIP_reg(&ctx) = rmcb->proc_ofs;
            DS_reg(&ctx) = ss;
            ESI_reg(&ctx) = ESP_reg(context);
            ES_reg(&ctx) = rmcb->regs_sel;
            EDI_reg(&ctx) = rmcb->regs_ofs;
            Callbacks->CallRegisterShortProc(&ctx, 2);
            es = ES_reg(&ctx);
            edi = EDI_reg(&ctx);
        }
	SELECTOR_FreeBlock(ss, 1);
        INT_GetRealModeContext((REALMODECALL*)PTR_SEG_OFF_TO_LIN( es, edi ), context);
#else
        ERR("RMCBs only implemented for i386\n");
#endif
    }
}


/**********************************************************************
 *	    DPMI_CallRMProc
 *
 * This routine does the hard work of calling a real mode procedure.
 */
int DPMI_CallRMProc( CONTEXT86 *context, LPWORD stack, int args, int iret )
{
    LPWORD stack16;
#ifndef MZ_SUPPORTED
    WORD sel;
    SEGPTR seg_addr;
#endif /* !MZ_SUPPORTED */
    LPVOID addr = NULL; /* avoid gcc warning */
    TDB *pTask = (TDB *)GlobalLock16( GetCurrentTask() );
    NE_MODULE *pModule = pTask ? NE_GetPtr( pTask->hModule ) : NULL;
    RMCB *CurrRMCB;
    int alloc = 0, already = 0;
    BYTE *code;

    GlobalUnlock16( GetCurrentTask() );

    TRACE("EAX=%08lx EBX=%08lx ECX=%08lx EDX=%08lx\n",
                 EAX_reg(context), EBX_reg(context), ECX_reg(context), EDX_reg(context) );
    TRACE("ESI=%08lx EDI=%08lx ES=%04lx DS=%04lx CS:IP=%04lx:%04x, %d WORD arguments, %s\n",
                 ESI_reg(context), EDI_reg(context), ES_reg(context), DS_reg(context),
                 CS_reg(context), LOWORD(EIP_reg(context)), args, iret?"IRET":"FAR" );

callrmproc_again:

/* there might be some code that just jumps to RMCBs or the like,
   in which case following the jumps here might get us to a shortcut */
    code = CTX_SEG_OFF_TO_LIN(context, CS_reg(context), EIP_reg(context));
    switch (*code) {
    case 0xe9: /* JMP NEAR */
      EIP_reg(context) += 3 + *(WORD *)(code+1);
      /* yeah, I know these gotos don't look good... */
      goto callrmproc_again;
    case 0xea: /* JMP FAR */
      EIP_reg(context) = *(WORD *)(code+1);
      CS_reg(context) = *(WORD *)(code+3);
      /* ...but since the label is there anyway... */
      goto callrmproc_again;
    case 0xeb: /* JMP SHORT */
      EIP_reg(context) += 2 + *(signed char *)(code+1);
      /* ...because of other gotos below, so... */
      goto callrmproc_again;
    }

/* shortcut for chaining to internal interrupt handlers */
    if ((CS_reg(context) == 0xF000) && iret) {
        return INT_RealModeInterrupt( LOWORD(EIP_reg(context))/4, context);
    }

/* shortcut for RMCBs */
    CurrRMCB = FirstRMCB;

    while (CurrRMCB && (HIWORD(CurrRMCB->address) != CS_reg(context)))
        CurrRMCB = CurrRMCB->next;

#ifdef MZ_SUPPORTED
    if (!(CurrRMCB || pModule->lpDosTask)) {
        FIXME("DPMI real-mode call using DOS VM task system, not fully tested!\n");
        TRACE("creating VM86 task\n");
        if (!MZ_InitTask( MZ_AllocDPMITask( pModule->self ) )) {
            ERR("could not setup VM86 task\n");
            return 1;
        }
    }
#endif
    if (!already) {
#ifdef MZ_SUPPORTED
        if (!SS_reg(context)) {
            alloc = 1; /* allocate default stack */
            stack16 = addr = DOSMEM_GetBlock( pModule->self, 64, (UINT16 *)&(SS_reg(context)) );
            ESP_reg(context) = 64-2;
            stack16 += 32-1;
            if (!addr) {
                ERR("could not allocate default stack\n");
                return 1;
            }
        } else {
            stack16 = CTX_SEG_OFF_TO_LIN(context, SS_reg(context), ESP_reg(context));
        }
        ESP_reg(context) -= (args + (iret?1:0)) * sizeof(WORD);
#else
        stack16 = (LPWORD) CURRENT_STACK16;
#endif
        stack16 -= args;
        if (args) memcpy(stack16, stack, args*sizeof(WORD) );
        /* push flags if iret */
        if (iret) {
            stack16--; args++;
            *stack16 = LOWORD(EFL_reg(context));
        }
#ifdef MZ_SUPPORTED
        /* push return address (return to interrupt wrapper) */
        *(--stack16) = DPMI_wrap_seg;
        *(--stack16) = 0;
        /* adjust stack */
        ESP_reg(context) -= 2*sizeof(WORD);
#endif
        already = 1;
    }

    if (CurrRMCB) {
        /* RMCB call, invoke protected-mode handler directly */
        DPMI_CallRMCBProc(context, CurrRMCB, pModule->lpDosTask?pModule->lpDosTask->dpmi_flag:0);
        /* check if we returned to where we thought we would */
        if ((CS_reg(context) != DPMI_wrap_seg) ||
            (LOWORD(EIP_reg(context)) != 0)) {
            /* we need to continue at different address in real-mode space,
               so we need to set it all up for real mode again */
            goto callrmproc_again;
        }
    } else {
#ifdef MZ_SUPPORTED
#if 0 /* this was probably unnecessary */
        /* push call address */
        *(--stack16) = CS_reg(context);
        *(--stack16) = LOWORD(EIP_reg(context));
        /* adjust stack */
        ESP_reg(context) -= 2*sizeof(WORD);
        /* set initial CS:IP to the wrapper's "lret" */
        CS_reg(context) = DPMI_wrap_seg;
        EIP_reg(context) = 2;
#endif
        TRACE("entering real mode...\n");
        DOSVM_Enter( context );
        TRACE("returned from real-mode call\n");
#else
        addr = CTX_SEG_OFF_TO_LIN(context, CS_reg(context), EIP_reg(context));
        sel = SELECTOR_AllocBlock( addr, 0x10000, SEGMENT_CODE, FALSE, FALSE );
        seg_addr = PTR_SEG_OFF_TO_SEGPTR( sel, 0 );

        CS_reg(context) = HIWORD(seg_addr);
        EIP_reg(context) = LOWORD(seg_addr);
        EBP_reg(context) = OFFSETOF( NtCurrentTeb()->cur_stack )
                                   + (WORD)&((STACK16FRAME*)0)->bp;
        Callbacks->CallRegisterShortProc(context, args*sizeof(WORD));
	SELECTOR_FreeBlock(sel, 1);
#endif
    }
    if (alloc) DOSMEM_FreeBlock( pModule->self, addr );
    return 0;
}


/**********************************************************************
 *	    CallRMInt
 */
static void CallRMInt( CONTEXT86 *context )
{
    CONTEXT86 realmode_ctx;
    FARPROC16 rm_int = INT_GetRMHandler( BL_reg(context) );
    REALMODECALL *call = (REALMODECALL *)PTR_SEG_OFF_TO_LIN( ES_reg(context),
                                                          DI_reg(context) );
    INT_GetRealModeContext( call, &realmode_ctx );

    /* we need to check if a real-mode program has hooked the interrupt */
    if (HIWORD(rm_int)!=0xF000) {
        /* yup, which means we need to switch to real mode... */
        CS_reg(&realmode_ctx) = HIWORD(rm_int);
        EIP_reg(&realmode_ctx) = LOWORD(rm_int);
        if (DPMI_CallRMProc( &realmode_ctx, NULL, 0, TRUE))
          SET_CFLAG(context);
    } else {
        RESET_CFLAG(context);
        /* use the IP we have instead of BL_reg, in case some apps
           decide to move interrupts around for whatever reason... */
        if (INT_RealModeInterrupt( LOWORD(rm_int)/4, &realmode_ctx ))
          SET_CFLAG(context);
        if (EFL_reg(context)&1) {
          FIXME("%02x: EAX=%08lx EBX=%08lx ECX=%08lx EDX=%08lx\n",
                BL_reg(context), EAX_reg(&realmode_ctx), EBX_reg(&realmode_ctx), 
                ECX_reg(&realmode_ctx), EDX_reg(&realmode_ctx));
          FIXME("      ESI=%08lx EDI=%08lx DS=%04lx ES=%04lx\n",
                ESI_reg(&realmode_ctx), EDI_reg(&realmode_ctx), 
                DS_reg(&realmode_ctx), ES_reg(&realmode_ctx) );
        }
    }
    INT_SetRealModeContext( call, &realmode_ctx );
}


static void CallRMProc( CONTEXT86 *context, int iret )
{
    REALMODECALL *p = (REALMODECALL *)PTR_SEG_OFF_TO_LIN( ES_reg(context), DI_reg(context) );
    CONTEXT86 context16;

    TRACE("RealModeCall: EAX=%08lx EBX=%08lx ECX=%08lx EDX=%08lx\n",
	p->eax, p->ebx, p->ecx, p->edx);
    TRACE("              ESI=%08lx EDI=%08lx ES=%04x DS=%04x CS:IP=%04x:%04x, %d WORD arguments, %s\n",
	p->esi, p->edi, p->es, p->ds, p->cs, p->ip, CX_reg(context), iret?"IRET":"FAR" );

    if (!(p->cs) && !(p->ip)) { /* remove this check
                                   if Int21/6501 case map function
                                   has been implemented */
	SET_CFLAG(context);
	return;
    }
    INT_GetRealModeContext(p, &context16);
    DPMI_CallRMProc( &context16, ((LPWORD)PTR_SEG_OFF_TO_LIN(SS_reg(context), LOWORD(ESP_reg(context))))+3,
                     CX_reg(context), iret );
    INT_SetRealModeContext(p, &context16);
}


static void WINAPI WINE_UNUSED RMCallbackProc( RMCB *rmcb )
{
    /* This routine should call DPMI_CallRMCBProc, but we don't have the
       register structure available - this is easily fixed by going through
       a Win16 register relay instead of calling RMCallbackProc "directly",
       but I won't bother at this time. */
    FIXME("not properly supported on your architecture!\n");
}

static RMCB *DPMI_AllocRMCB( void )
{
    RMCB *NewRMCB = HeapAlloc(GetProcessHeap(), 0, sizeof(RMCB));
    UINT16 uParagraph;

    if (NewRMCB)
    {
#ifdef MZ_SUPPORTED
	LPVOID RMCBmem = DOSMEM_GetBlock(0, 4, &uParagraph);
	LPBYTE p = RMCBmem;

	*p++ = 0xcd; /* RMCB: */
	*p++ = 0x31; /* int $0x31 */
/* it is the called procedure's task to change the return CS:EIP
   the DPMI 0.9 spec states that if it doesn't, it will be called again */
	*p++ = 0xeb;
	*p++ = 0xfc; /* jmp RMCB */
#else
	LPVOID RMCBmem = DOSMEM_GetBlock(0, 15, &uParagraph);
	LPBYTE p = RMCBmem;

	*p++ = 0x68; /* pushl */
	*(LPVOID *)p = NewRMCB;
	p+=4;
	*p++ = 0x9a; /* lcall */
	*(FARPROC16 *)p = (FARPROC16)RMCallbackProc; /* FIXME: register relay */
	p+=4;
	GET_CS(*(WORD *)p);
	p+=2;
	*p++=0xc3; /* lret (FIXME?) */
#endif
	NewRMCB->address = MAKELONG(0, uParagraph);
	NewRMCB->next = FirstRMCB;
	FirstRMCB = NewRMCB;
    }
    return NewRMCB;
}


static void AllocRMCB( CONTEXT86 *context )
{
    RMCB *NewRMCB = DPMI_AllocRMCB();

    TRACE("Function to call: %04x:%04x\n", (WORD)DS_reg(context), SI_reg(context) );

    if (NewRMCB)
    {
	/* FIXME: if 32-bit DPMI client, use ESI and EDI */
	NewRMCB->proc_ofs = SI_reg(context);
	NewRMCB->proc_sel = DS_reg(context);
	NewRMCB->regs_ofs = DI_reg(context);
	NewRMCB->regs_sel = ES_reg(context);
	SET_LOWORD( ECX_reg(context), HIWORD(NewRMCB->address) );
	SET_LOWORD( EDX_reg(context), LOWORD(NewRMCB->address) );
    }
    else
    {
	SET_LOWORD( EAX_reg(context), 0x8015 ); /* callback unavailable */
	SET_CFLAG(context);
    }
}


FARPROC16 WINAPI DPMI_AllocInternalRMCB( RMCBPROC proc )
{
    RMCB *NewRMCB = DPMI_AllocRMCB();

    if (NewRMCB) {
        NewRMCB->proc_ofs = (DWORD)proc;
        NewRMCB->proc_sel = 0;
        NewRMCB->regs_ofs = 0;
        NewRMCB->regs_sel = 0;
        return (FARPROC16)(NewRMCB->address);
    }
    return NULL;
}


static int DPMI_FreeRMCB( DWORD address )
{
    RMCB *CurrRMCB = FirstRMCB;
    RMCB *PrevRMCB = NULL;

    while (CurrRMCB && (CurrRMCB->address != address))
    {
	PrevRMCB = CurrRMCB;
	CurrRMCB = CurrRMCB->next;
    }
    if (CurrRMCB)
    {
	if (PrevRMCB)
	PrevRMCB->next = CurrRMCB->next;
	    else
	FirstRMCB = CurrRMCB->next;
	DOSMEM_FreeBlock(0, DOSMEM_MapRealToLinear(CurrRMCB->address));
	HeapFree(GetProcessHeap(), 0, CurrRMCB);
	return 0;
    }
    return 1;
}


static void FreeRMCB( CONTEXT86 *context )
{
    FIXME("callback address: %04x:%04x\n",
          CX_reg(context), DX_reg(context));

    if (DPMI_FreeRMCB(MAKELONG(DX_reg(context), CX_reg(context)))) {
	SET_LOWORD( EAX_reg(context), 0x8024 ); /* invalid callback address */
	SET_CFLAG(context);
    }
}


void WINAPI DPMI_FreeInternalRMCB( FARPROC16 proc )
{
    DPMI_FreeRMCB( (DWORD)proc );
}


#ifdef MZ_SUPPORTED
/* (see loader/dos/module.c, function MZ_InitDPMI) */

static void StartPM( CONTEXT86 *context, LPDOSTASK lpDosTask )
{
    char *base = DOSMEM_MemoryBase(0);
    UINT16 cs, ss, ds, es;
    CONTEXT86 pm_ctx;
    DWORD psp_ofs = (DWORD)(lpDosTask->psp_seg<<4);
    PDB16 *psp = (PDB16 *)(base + psp_ofs);
    HANDLE16 env_seg = psp->environment;
    int is32;

    RESET_CFLAG(context);
    lpDosTask->dpmi_flag = AX_reg(context);
    is32 = lpDosTask->dpmi_flag & 1;
/* our mode switch wrapper have placed the desired CS into DX */
    cs = SELECTOR_AllocBlock( base + (DWORD)(DX_reg(context)<<4), 0x10000, SEGMENT_CODE, FALSE, FALSE );
/* due to a flaw in some CPUs (at least mine), it is best to mark stack segments as 32-bit if they
   can be used in 32-bit code. Otherwise, these CPUs may not set the high word of esp during a
   ring transition (from kernel code) to the 16-bit stack, and this causes trouble if executing
   32-bit code using this stack. */
    ss = SELECTOR_AllocBlock( base + (DWORD)(SS_reg(context)<<4), 0x10000, SEGMENT_DATA, is32, FALSE );
/* do the same for the data segments, just in case */
    if (DS_reg(context) == SS_reg(context)) ds = ss;
    else ds = SELECTOR_AllocBlock( base + (DWORD)(DS_reg(context)<<4), 0x10000, SEGMENT_DATA, is32, FALSE );
    es = SELECTOR_AllocBlock( base + psp_ofs, 0x100, SEGMENT_DATA, is32, FALSE );
/* convert environment pointer, as the spec says, but we're a bit lazy about the size here... */
    psp->environment = SELECTOR_AllocBlock( base + (DWORD)(env_seg<<4),
					    0x10000, SEGMENT_DATA, FALSE, FALSE );

    pm_ctx = *context;
    CS_reg(&pm_ctx) = lpDosTask->dpmi_sel;
/* our mode switch wrapper expects the new CS in DX, and the new SS in AX */
    EAX_reg(&pm_ctx) = ss;
    EDX_reg(&pm_ctx) = cs;
    DS_reg(&pm_ctx) = ds;
    ES_reg(&pm_ctx) = es;
    FS_reg(&pm_ctx) = 0;
    GS_reg(&pm_ctx) = 0;

    TRACE("DOS program is now entering protected mode\n");
    Callbacks->CallRegisterShortProc(&pm_ctx, 0);

    /* in the current state of affairs, we won't ever actually return here... */
    /* we should have int21/ah=4c do it someday, though... */

    SELECTOR_FreeBlock(psp->environment, 1);
    psp->environment = env_seg;
    SELECTOR_FreeBlock(es, 1);
    if (ds != ss) SELECTOR_FreeBlock(ds, 1);
    SELECTOR_FreeBlock(ss, 1);
    SELECTOR_FreeBlock(cs, 1);
}

/* DPMI Raw Mode Switch handler */

#if 0
void WINAPI DPMI_RawModeSwitch( SIGCONTEXT *context )
{
  LPDOSTASK lpDosTask = MZ_Current();
  CONTEXT86 rm_ctx;
  int ret;

  if (!lpDosTask) {
    /* we could probably start a DPMI-only dosmod task here, but I doubt
       anything other than real DOS apps want to call raw mode switch */
    ERR("attempting raw mode switch without DOS task!\n");
    ExitProcess(1);
  }
  /* initialize real-mode context as per spec */
  memset(&rm_ctx, 0, sizeof(rm_ctx));
  DS_reg(&rm_ctx) = AX_sig(context);
  ES_reg(&rm_ctx) = CX_sig(context);
  SS_reg(&rm_ctx) = DX_sig(context);
  ESP_reg(&rm_ctx) = EBX_sig(context);
  CS_reg(&rm_ctx) = SI_sig(context);
  EIP_reg(&rm_ctx) = EDI_sig(context);
  EBP_reg(&rm_ctx) = EBP_sig(context);
  FS_reg(&rm_ctx) = 0;
  GS_reg(&rm_ctx) = 0;
  EFL_reg(&rm_ctx) = EFL_sig(context); /* at least we need the IF flag */

  /* enter real mode again */
  TRACE("re-entering real mode at %04lx:%04lx\n",
	CS_reg(&rm_ctx),EIP_reg(&rm_ctx));
  ret = DOSVM_Enter( &rm_ctx );
  /* when the real-mode stuff call its mode switch address,
     DOSVM_Enter will return and we will continue here */

  if (ret<0) {
    /* if the sync was lost, there's no way to recover */
    ExitProcess(1);
  }

  /* alter protected-mode context as per spec */
  DS_sig(context) = AX_reg(&rm_ctx);
  ES_sig(context) = CX_reg(&rm_ctx);
  SS_sig(context) = DX_reg(&rm_ctx);
  ESP_sig(context) = EBX_reg(&rm_ctx);
  CS_sig(context) = SI_reg(&rm_ctx);
  EIP_sig(context) = EDI_reg(&rm_ctx);
  EBP_sig(context) = EBP_reg(&rm_ctx);
  FS_sig(context) = 0;
  GS_sig(context) = 0;

  /* Return to new address and hope that we didn't mess up */
  TRACE("re-entering protected mode at %04x:%08lx\n",
	CS_sig(context), EIP_sig(context));
}
#endif

#else
#if 0
void WINAPI DPMI_RawModeSwitch( SIGCONTEXT *context )
{
  ERR("don't even think about DPMI raw mode switch without DOS support!\n");
  ExitProcess(1);
}
#endif
#endif

#define DOS_APP_ISDOS(addr,base) ((addr) < 0x110000)
#define DOS_WINE_ISDOS(addr,base) (((addr) >= (base)) && ((addr) < (base) + 0x110000))
#define DOS_UC_APPTOWINE(addr,base) ((addr) + (base))
#define DOS_UC_WINETOAPP(addr,base) ((addr) - (base))
#define DOS_APPTOWINE(addr,base) (DOS_APP_ISDOS(addr,base) ? DOS_UC_APPTOWINE(addr,base) : (addr))
#define DOS_WINETOAPP(addr,base) (DOS_WINE_ISDOS(addr,base) ? DOS_UC_WINETOAPP(addr,base) : (addr))
#define DOS_BADLIMIT(addr,base,limit) \
  ((limit == 0xffffffff) || /* disallow "fat DS" for now */ \
   (DOS_WINE_ISDOS(addr,base) && \
    ((addr) + (limit) > (base) + 0x110000)))

/**********************************************************************
 *	    INT_Int31Handler
 *
 * Handler for int 31h (DPMI).
 */

void WINAPI INT_Int31Handler( CONTEXT86 *context )
{
    /*
     * Note: For Win32s processes, the whole linear address space is
     *       shifted by 0x10000 relative to the OS linear address space.
     *       See the comment in msdos/vxd.c.
     */
    DWORD offset = W32S_APPLICATION() ? W32S_OFFSET : 0;

    DWORD dw;
    BYTE *ptr;

    LPDOSTASK lpDosTask = MZ_Current();

#ifdef MZ_SUPPORTED
    if (ISV86(context) && lpDosTask) {
        /* Called from real mode, check if it's our wrapper */
        TRACE("called from real mode\n");
        if (CS_reg(context)==lpDosTask->dpmi_seg) {
            /* This is the protected mode switch */
            StartPM(context,lpDosTask);
            return;
        } else
        if (CS_reg(context)==lpDosTask->xms_seg) {
            /* This is the XMS driver entry point */
            XMS_Handler(context);
            return;
        } else
        {
            /* Check for RMCB */
            RMCB *CurrRMCB = FirstRMCB;
            
            while (CurrRMCB && (HIWORD(CurrRMCB->address) != CS_reg(context)))
                CurrRMCB = CurrRMCB->next;
            
            if (CurrRMCB) {
                /* RMCB call, propagate to protected-mode handler */
                DPMI_CallRMCBProc(context, CurrRMCB, lpDosTask->dpmi_flag);
                return;
            }
        }
    }
#endif

    RESET_CFLAG(context);
    switch(AX_reg(context))
    {
    case 0x0000:  /* Allocate LDT descriptors */
    	TRACE("allocate LDT descriptors (%d)\n",CX_reg(context));
        if (!(EAX_reg(context) = AllocSelectorArray16( CX_reg(context) )))
        {
    	    TRACE("failed\n");
            EAX_reg(context) = 0x8011;  /* descriptor unavailable */
            SET_CFLAG(context);
        }
	TRACE("success, array starts at 0x%04x\n",AX_reg(context));
        break;

    case 0x0001:  /* Free LDT descriptor */
    	TRACE("free LDT descriptor (0x%04x)\n",BX_reg(context));
        if (FreeSelector16( BX_reg(context) ))
        {
            EAX_reg(context) = 0x8022;  /* invalid selector */
            SET_CFLAG(context);
        }
        else
        {
            /* If a segment register contains the selector being freed, */
            /* set it to zero. */
            if (!((DS_reg(context)^BX_reg(context)) & ~3)) DS_reg(context) = 0;
            if (!((ES_reg(context)^BX_reg(context)) & ~3)) ES_reg(context) = 0;
            if (!((FS_reg(context)^BX_reg(context)) & ~3)) FS_reg(context) = 0;
            if (!((GS_reg(context)^BX_reg(context)) & ~3)) GS_reg(context) = 0;
        }
        break;

    case 0x0002:  /* Real mode segment to descriptor */
    	TRACE("real mode segment to descriptor (0x%04x)\n",BX_reg(context));
        {
            WORD entryPoint = 0;  /* KERNEL entry point for descriptor */
            switch(BX_reg(context))
            {
            case 0x0000: entryPoint = 183; break;  /* __0000H */
            case 0x0040: entryPoint = 193; break;  /* __0040H */
            case 0xa000: entryPoint = 174; break;  /* __A000H */
            case 0xb000: entryPoint = 181; break;  /* __B000H */
            case 0xb800: entryPoint = 182; break;  /* __B800H */
            case 0xc000: entryPoint = 195; break;  /* __C000H */
            case 0xd000: entryPoint = 179; break;  /* __D000H */
            case 0xe000: entryPoint = 190; break;  /* __E000H */
            case 0xf000: entryPoint = 194; break;  /* __F000H */
            default:
	    	EAX_reg(context) = DOSMEM_AllocSelector(BX_reg(context));
                break;
            }
            if (entryPoint) 
                EAX_reg(context) = LOWORD(NE_GetEntryPoint( GetModuleHandle16( "KERNEL" ),
                                                            entryPoint ));
        }
        break;

    case 0x0003:  /* Get next selector increment */
    	TRACE("get selector increment (__AHINCR)\n");
        EAX_reg(context) = __AHINCR;
        break;

    case 0x0004:  /* Lock selector (not supported) */
    	FIXME("lock selector not supported\n");
        EAX_reg(context) = 0;  /* FIXME: is this a correct return value? */
        break;

    case 0x0005:  /* Unlock selector (not supported) */
    	FIXME("unlock selector not supported\n");
        EAX_reg(context) = 0;  /* FIXME: is this a correct return value? */
        break;

    case 0x0006:  /* Get selector base address */
    	TRACE("get selector base address (0x%04x)\n",BX_reg(context));
        if (!(dw = GetSelectorBase( BX_reg(context) )))
        {
            EAX_reg(context) = 0x8022;  /* invalid selector */
            SET_CFLAG(context);
        }
        else
        {
#ifdef MZ_SUPPORTED
            if (lpDosTask) {
                DWORD base = (DWORD)DOSMEM_MemoryBase(lpDosTask->hModule);
		dw = DOS_WINETOAPP(dw, base);
            }
#endif
            CX_reg(context) = HIWORD(W32S_WINE2APP(dw, offset));
            DX_reg(context) = LOWORD(W32S_WINE2APP(dw, offset));
        }
        break;

    case 0x0007:  /* Set selector base address */
    	TRACE("set selector base address (0x%04x,0x%08lx)\n",
                     BX_reg(context),
                     W32S_APP2WINE(MAKELONG(DX_reg(context),CX_reg(context)), offset));
        dw = W32S_APP2WINE(MAKELONG(DX_reg(context), CX_reg(context)), offset);
#ifdef MZ_SUPPORTED
        if (lpDosTask) {
            DWORD base = (DWORD)DOSMEM_MemoryBase(lpDosTask->hModule);
	    dw = DOS_APPTOWINE(dw, base);
        }
#endif
        SetSelectorBase(BX_reg(context), dw);
        break;

    case 0x0008:  /* Set selector limit */
    	TRACE("set selector limit (0x%04x,0x%08lx)\n",BX_reg(context),MAKELONG(DX_reg(context),CX_reg(context)));
        dw = MAKELONG( DX_reg(context), CX_reg(context) );
#ifdef MZ_SUPPORTED
        if (lpDosTask) {
	    DWORD base = (DWORD)DOSMEM_MemoryBase(lpDosTask->hModule);
            DWORD sbase = GetSelectorBase( BX_reg(context) );
	    if (!sbase) {
	        /* the app has set the limit without setting the base,
	         * it must be relying on that the default should be DOS space;
	         * so set the base address now */
	        SetSelectorBase( BX_reg(context), sbase = base );
	        if (dw == 0xffffffff) {
	            /* djgpp does this without checking (in _dos_ds setup, crt1.c),
	             * so we have to override the limit here */
	            dw = 0x110000;
	        }
	    }
	    if (DOS_BADLIMIT(sbase, base, dw)) {
                AX_reg(context) = 0x8021;  /* invalid value */
                SET_CFLAG(context);
                break;
            }
        }
#endif
        SetSelectorLimit16( BX_reg(context), dw );
        break;

    case 0x0009:  /* Set selector access rights */
    	TRACE("set selector access rights(0x%04x,0x%04x)\n",BX_reg(context),CX_reg(context));
        SelectorAccessRights16( BX_reg(context), 1, CX_reg(context) );
        break;

    case 0x000a:  /* Allocate selector alias */
    	TRACE("allocate selector alias (0x%04x)\n",BX_reg(context));
        if (!(AX_reg(context) = AllocCStoDSAlias16( BX_reg(context) )))
        {
            AX_reg(context) = 0x8011;  /* descriptor unavailable */
            SET_CFLAG(context);
        }
        break;

    case 0x000b:  /* Get descriptor */
    	TRACE("get descriptor (0x%04x)\n",BX_reg(context));
        {
            ldt_entry entry;
            LDT_GetEntry( SELECTOR_TO_ENTRY( BX_reg(context) ), &entry );
#ifdef MZ_SUPPORTED
            if (lpDosTask) {
                DWORD base = (DWORD)DOSMEM_MemoryBase(lpDosTask->hModule);
		entry.base = DOS_WINETOAPP(entry.base, base);
            }
#endif
            entry.base = W32S_WINE2APP(entry.base, offset);

            /* FIXME: should use ES:EDI for 32-bit clients */
            LDT_EntryToBytes( PTR_SEG_OFF_TO_LIN( ES_reg(context),
                                                  DI_reg(context) ), &entry );
        }
        break;

    case 0x000c:  /* Set descriptor */
    	TRACE("set descriptor (0x%04x)\n",BX_reg(context));
        {
            ldt_entry entry;
            LDT_BytesToEntry( PTR_SEG_OFF_TO_LIN( ES_reg(context),
                                                  DI_reg(context) ), &entry );
            entry.base = W32S_APP2WINE(entry.base, offset);
#ifdef MZ_SUPPORTED
            if (lpDosTask) {
                DWORD base = (DWORD)DOSMEM_MemoryBase(lpDosTask->hModule);
	        entry.base = DOS_APPTOWINE(entry.base, base);
		if (DOS_BADLIMIT(entry.base, base, entry.limit)) {
		    AX_reg(context) = 0x8021;  /* invalid value */
                    SET_CFLAG(context);
		    break;
		}
            }
#endif

            LDT_SetEntry( SELECTOR_TO_ENTRY( BX_reg(context) ), &entry );
        }
        break;

    case 0x000d:  /* Allocate specific LDT descriptor */
    	FIXME("allocate descriptor (0x%04x), stub!\n",BX_reg(context));
        AX_reg(context) = 0x8011; /* descriptor unavailable */
        SET_CFLAG(context);
        break;
    case 0x0100:  /* Allocate DOS memory block */
        TRACE("allocate DOS memory block (0x%x paragraphs)\n",BX_reg(context));
        dw = GlobalDOSAlloc16((DWORD)BX_reg(context)<<4);
        if (dw) {
            AX_reg(context) = HIWORD(dw);
            DX_reg(context) = LOWORD(dw);
        } else {
            AX_reg(context) = 0x0008; /* insufficient memory */
            BX_reg(context) = DOSMEM_Available(0)>>4;
            SET_CFLAG(context);
        }
        break;
    case 0x0101:  /* Free DOS memory block */
        TRACE("free DOS memory block (0x%04x)\n",DX_reg(context));
        dw = GlobalDOSFree16(DX_reg(context));
        if (!dw) {
            AX_reg(context) = 0x0009; /* memory block address invalid */
            SET_CFLAG(context);
        }
        break;
    case 0x0200: /* get real mode interrupt vector */
	FIXME("get realmode interupt vector(0x%02x) unimplemented.\n",
	      BL_reg(context));
    	SET_CFLAG(context);
        break;
    case 0x0201: /* set real mode interrupt vector */
	FIXME("set realmode interupt vector(0x%02x,0x%04x:0x%04x) unimplemented\n", BL_reg(context),CX_reg(context),DX_reg(context));
    	SET_CFLAG(context);
        break;
    case 0x0204:  /* Get protected mode interrupt vector */
    	TRACE("get protected mode interrupt handler (0x%02x), stub!\n",BL_reg(context));
	dw = (DWORD)INT_GetPMHandler( BL_reg(context) );
	CX_reg(context) = HIWORD(dw);
	DX_reg(context) = LOWORD(dw);
	break;

    case 0x0205:  /* Set protected mode interrupt vector */
    	TRACE("set protected mode interrupt handler (0x%02x,%p), stub!\n",
            BL_reg(context),PTR_SEG_OFF_TO_LIN(CX_reg(context),DX_reg(context)));
	INT_SetPMHandler( BL_reg(context),
                          (FARPROC16)PTR_SEG_OFF_TO_SEGPTR( CX_reg(context),
                                                            DX_reg(context) ));
	break;

    case 0x0300:  /* Simulate real mode interrupt */
        CallRMInt( context );
        break;

    case 0x0301:  /* Call real mode procedure with far return */
	CallRMProc( context, FALSE );
	break;

    case 0x0302:  /* Call real mode procedure with interrupt return */
	CallRMProc( context, TRUE );
        break;

    case 0x0303:  /* Allocate Real Mode Callback Address */
	AllocRMCB( context );
	break;

    case 0x0304:  /* Free Real Mode Callback Address */
	FreeRMCB( context );
	break;

    case 0x0305:  /* Get State Save/Restore Addresses */
        TRACE("get state save/restore addresses\n");
        /* we probably won't need this kind of state saving */
        AX_reg(context) = 0;
	/* real mode: just point to the lret */
	BX_reg(context) = DPMI_wrap_seg;
	ECX_reg(context) = 2;
	/* protected mode: don't have any handler yet... */
	FIXME("no protected-mode dummy state save/restore handler yet\n");
	SI_reg(context) = 0;
	EDI_reg(context) = 0;
        break;

    case 0x0306:  /* Get Raw Mode Switch Addresses */
        TRACE("get raw mode switch addresses\n");
	if (lpDosTask) {
	  /* real mode, point to standard DPMI return wrapper */
	  BX_reg(context) = DPMI_wrap_seg;
	  ECX_reg(context) = 0;
	  /* protected mode, point to DPMI call wrapper */
	  SI_reg(context) = lpDosTask->dpmi_sel;
	  EDI_reg(context) = 8; /* offset of the INT 0x31 call */
	} else {
	  ERR("win app attempting to get raw mode switch!\n");
	  AX_reg(context) = 0x8001; /* unsupported function */
	  SET_CFLAG(context);
	}
	break;
    case 0x0400:  /* Get DPMI version */
        TRACE("get DPMI version\n");
    	{
	    SYSTEM_INFO si;

	    GetSystemInfo(&si);
	    AX_reg(context) = 0x005a;  /* DPMI version 0.90 */
	    BX_reg(context) = 0x0005;  /* Flags: 32-bit, virtual memory */
	    CL_reg(context) = si.wProcessorLevel;
	    DX_reg(context) = 0x0102;  /* Master/slave interrupt controller base*/
	    break;
	}
    case 0x0500:  /* Get free memory information */
        TRACE("get free memory information\n");
        {
            MEMMANINFO mmi;

            mmi.dwSize = sizeof(mmi);
            MemManInfo16(&mmi);
            ptr = (BYTE *)PTR_SEG_OFF_TO_LIN(ES_reg(context),DI_reg(context));
            /* the layout is just the same as MEMMANINFO, but without
             * the dwSize entry.
             */
            memcpy(ptr,((char*)&mmi)+4,sizeof(mmi)-4);
            break;
        }
    case 0x0501:  /* Allocate memory block */
        TRACE("allocate memory block (%ld)\n",MAKELONG(CX_reg(context),BX_reg(context)));
	if (!(ptr = (BYTE *)DPMI_xalloc(MAKELONG(CX_reg(context), BX_reg(context)))))
        {
            AX_reg(context) = 0x8012;  /* linear memory not available */
            SET_CFLAG(context);
        } else {
            BX_reg(context) = SI_reg(context) = HIWORD(W32S_WINE2APP(ptr, offset));
            CX_reg(context) = DI_reg(context) = LOWORD(W32S_WINE2APP(ptr, offset));
        }
        break;

    case 0x0502:  /* Free memory block */
        TRACE("free memory block (0x%08lx)\n",
                     W32S_APP2WINE(MAKELONG(DI_reg(context),SI_reg(context)), offset));
	DPMI_xfree( (void *)W32S_APP2WINE(MAKELONG(DI_reg(context), 
                                               SI_reg(context)), offset) );
        break;

    case 0x0503:  /* Resize memory block */
        TRACE("resize memory block (0x%08lx,%ld)\n",
                     W32S_APP2WINE(MAKELONG(DI_reg(context),SI_reg(context)), offset),
                     MAKELONG(CX_reg(context),BX_reg(context)));
        if (!(ptr = (BYTE *)DPMI_xrealloc(
                (void *)W32S_APP2WINE(MAKELONG(DI_reg(context),SI_reg(context)), offset),
                MAKELONG(CX_reg(context),BX_reg(context)))))
        {
            AX_reg(context) = 0x8012;  /* linear memory not available */
            SET_CFLAG(context);
        } else {
            BX_reg(context) = SI_reg(context) = HIWORD(W32S_WINE2APP(ptr, offset));
            CX_reg(context) = DI_reg(context) = LOWORD(W32S_WINE2APP(ptr, offset));
        }
        break;

    case 0x0507:  /* Modify page attributes */
        FIXME("modify page attributes unimplemented\n");
        break;  /* Just ignore it */

    case 0x0600:  /* Lock linear region */
        FIXME("lock linear region unimplemented\n");
        break;  /* Just ignore it */

    case 0x0601:  /* Unlock linear region */
        FIXME("unlock linear region unimplemented\n");
        break;  /* Just ignore it */

    case 0x0602:  /* Unlock real-mode region */
        FIXME("unlock realmode region unimplemented\n");
        break;  /* Just ignore it */

    case 0x0603:  /* Lock real-mode region */
        FIXME("lock realmode region unimplemented\n");
        break;  /* Just ignore it */

    case 0x0604:  /* Get page size */
        TRACE("get pagesize\n");
        BX_reg(context) = 0;
        CX_reg(context) = VIRTUAL_GetPageSize();
	break;

    case 0x0702:  /* Mark page as demand-paging candidate */
        FIXME("mark page as demand-paging candidate\n");
        break;  /* Just ignore it */

    case 0x0703:  /* Discard page contents */
        FIXME("discard page contents\n");
        break;  /* Just ignore it */

     case 0x0800:  /* Physical address mapping */
        FIXME("map real to linear (0x%08lx)\n",MAKELONG(CX_reg(context),BX_reg(context)));
         if(!(ptr=DOSMEM_MapRealToLinear(MAKELONG(CX_reg(context),BX_reg(context)))))
         {
             AX_reg(context) = 0x8021; 
             SET_CFLAG(context);
         }
         else
         {
             BX_reg(context) = HIWORD(W32S_WINE2APP(ptr, offset));
             CX_reg(context) = LOWORD(W32S_WINE2APP(ptr, offset));
             RESET_CFLAG(context);
         }
         break;

    default:
        INT_BARF( context, 0x31 );
        AX_reg(context) = 0x8001;  /* unsupported function */
        SET_CFLAG(context);
        break;
    }

}