/*
 * DPMI 0.9 emulation
 *
 * Copyright 1995 Alexandre Julliard
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

#include "config.h"

#include "windef.h"
#include "wine/winbase16.h"
#include "miscemu.h"
#include "task.h"
#include "msdos.h"
#include "dosexe.h"

#include "wine/debug.h"

WINE_DEFAULT_DEBUG_CHANNEL(int31);

/* 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;
static WORD dpmi_flag;

/**********************************************************************
 *	    INT_GetRealModeContext
 */
static void INT_GetRealModeContext( REALMODECALL *call, CONTEXT86 *context )
{
    context->Eax    = call->eax;
    context->Ebx    = call->ebx;
    context->Ecx    = call->ecx;
    context->Edx    = call->edx;
    context->Esi    = call->esi;
    context->Edi    = call->edi;
    context->Ebp    = call->ebp;
    context->EFlags = call->fl | V86_FLAG;
    context->Eip    = call->ip;
    context->Esp    = call->sp;
    context->SegCs  = call->cs;
    context->SegDs  = call->ds;
    context->SegEs  = call->es;
    context->SegFs  = call->fs;
    context->SegGs  = call->gs;
    context->SegSs  = call->ss;
}


/**********************************************************************
 *	    INT_SetRealModeContext
 */
static void INT_SetRealModeContext( REALMODECALL *call, CONTEXT86 *context )
{
    call->eax = context->Eax;
    call->ebx = context->Ebx;
    call->ecx = context->Ecx;
    call->edx = context->Edx;
    call->esi = context->Esi;
    call->edi = context->Edi;
    call->ebp = context->Ebp;
    call->fl  = LOWORD(context->EFlags);
    call->ip  = LOWORD(context->Eip);
    call->sp  = LOWORD(context->Esp);
    call->cs  = context->SegCs;
    call->ds  = context->SegDs;
    call->es  = context->SegEs;
    call->fs  = context->SegFs;
    call->gs  = context->SegGs;
    call->ss  = context->SegSs;
}


#ifdef __i386__

void DPMI_CallRMCB32(RMCB *rmcb, UINT16 ss, DWORD esp, UINT16*es, DWORD*edi)
#if 0 /* original code, which early gccs puke on */
{
    int _clobber;
    __asm__ __volatile__(
        "pushl %%ebp\n"
        "pushl %%ebx\n"
        "pushl %%es\n"
        "pushl %%ds\n"
        "pushfl\n"
        "mov %7,%%es\n"
        "mov %5,%%ds\n"
        ".byte 0x36, 0xff, 0x18\n" /* lcall *%ss:(%eax) */
        "popl %%ds\n"
        "mov %%es,%0\n"
        "popl %%es\n"
        "popl %%ebx\n"
        "popl %%ebp\n"
    : "=d" (*es), "=D" (*edi), "=S" (_clobber), "=a" (_clobber), "=c" (_clobber)
    : "0" (ss), "2" (esp),
      "4" (rmcb->regs_sel), "1" (rmcb->regs_ofs),
      "3" (&rmcb->proc_ofs) );
}
#else /* code generated by a gcc new enough */
;
__ASM_GLOBAL_FUNC(DPMI_CallRMCB32,
    "pushl %ebp\n\t"
    "movl %esp,%ebp\n\t"
    "pushl %edi\n\t"
    "pushl %esi\n\t"
    "movl 0x8(%ebp),%eax\n\t"
    "movl 0x10(%ebp),%esi\n\t"
    "movl 0xc(%ebp),%edx\n\t"
    "movl 0x10(%eax),%ecx\n\t"
    "movl 0xc(%eax),%edi\n\t"
    "addl $0x4,%eax\n\t"
    "pushl %ebp\n\t"
    "pushl %ebx\n\t"
    "pushl %es\n\t"
    "pushl %ds\n\t"
    "pushfl\n\t"
    "mov %cx,%es\n\t"
    "mov %dx,%ds\n\t"
    ".byte 0x36, 0xff, 0x18\n\t" /* lcall *%ss:(%eax) */
    "popl %ds\n\t"
    "mov %es,%dx\n\t"
    "popl %es\n\t"
    "popl %ebx\n\t"
    "popl %ebp\n\t"
    "movl 0x14(%ebp),%eax\n\t"
    "movw %dx,(%eax)\n\t"
    "movl 0x18(%ebp),%edx\n\t"
    "movl %edi,(%edx)\n\t"
    "popl %esi\n\t"
    "popl %edi\n\t"
    "leave\n\t"
    "ret")
#endif

#endif /* __i386__ */

/**********************************************************************
 *	    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 esp,edi;

        INT_SetRealModeContext(MapSL(MAKESEGPTR( rmcb->regs_sel, rmcb->regs_ofs )), context);
        ss = SELECTOR_AllocBlock( (void *)(context->SegSs<<4), 0x10000, WINE_LDT_FLAGS_DATA );
        esp = context->Esp;

        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) {
            /* 32-bit DPMI client */
            DPMI_CallRMCB32(rmcb, ss, esp, &es, &edi);
        } else {
            /* 16-bit DPMI client */
            CONTEXT86 ctx = *context;
            ctx.SegCs = rmcb->proc_sel;
            ctx.Eip   = rmcb->proc_ofs;
            ctx.SegDs = ss;
            ctx.Esi   = esp;
            ctx.SegEs = rmcb->regs_sel;
            ctx.Edi   = rmcb->regs_ofs;
            /* FIXME: I'm pretty sure this isn't right - should push flags first */
            wine_call_to_16_regs_short(&ctx, 0);
            es = ctx.SegEs;
            edi = ctx.Edi;
        }
	FreeSelector16(ss);
        INT_GetRealModeContext( MapSL( MAKESEGPTR( 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;
    LPVOID addr = NULL; /* avoid gcc warning */
    RMCB *CurrRMCB;
    int alloc = 0, already = 0;
    BYTE *code;

    TRACE("EAX=%08lx EBX=%08lx ECX=%08lx EDX=%08lx\n",
                 context->Eax, context->Ebx, context->Ecx, context->Edx );
    TRACE("ESI=%08lx EDI=%08lx ES=%04lx DS=%04lx CS:IP=%04lx:%04x, %d WORD arguments, %s\n",
                 context->Esi, context->Edi, context->SegEs, context->SegDs,
                 context->SegCs, LOWORD(context->Eip), 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, context->SegCs, context->Eip);
    switch (*code) {
    case 0xe9: /* JMP NEAR */
      context->Eip += 3 + *(WORD *)(code+1);
      /* yeah, I know these gotos don't look good... */
      goto callrmproc_again;
    case 0xea: /* JMP FAR */
      context->Eip = *(WORD *)(code+1);
      context->SegCs = *(WORD *)(code+3);
      /* ...but since the label is there anyway... */
      goto callrmproc_again;
    case 0xeb: /* JMP SHORT */
      context->Eip += 2 + *(signed char *)(code+1);
      /* ...because of other gotos below, so... */
      goto callrmproc_again;
    }

/* shortcut for chaining to internal interrupt handlers */
    if ((context->SegCs == 0xF000) && iret)
    {
        DOSVM_RealModeInterrupt( LOWORD(context->Eip)/4, context);
        return 0;
    }

/* shortcut for RMCBs */
    CurrRMCB = FirstRMCB;

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

    if (!CurrRMCB && !MZ_Current())
    {
        FIXME("DPMI real-mode call using DOS VM task system, not fully tested!\n");
        TRACE("creating VM86 task\n");
        MZ_AllocDPMITask();
    }
    if (!already) {
        if (!context->SegSs) {
            alloc = 1; /* allocate default stack */
            stack16 = addr = DOSMEM_GetBlock( 64, (UINT16 *)&(context->SegSs) );
            context->Esp = 64-2;
            stack16 += 32-1;
            if (!addr) {
                ERR("could not allocate default stack\n");
                return 1;
            }
        } else {
            stack16 = CTX_SEG_OFF_TO_LIN(context, context->SegSs, context->Esp);
        }
        context->Esp -= (args + (iret?1:0)) * sizeof(WORD);
        stack16 -= args;
        if (args) memcpy(stack16, stack, args*sizeof(WORD) );
        /* push flags if iret */
        if (iret) {
            stack16--; args++;
            *stack16 = LOWORD(context->EFlags);
        }
        /* push return address (return to interrupt wrapper) */
        *(--stack16) = DOSMEM_wrap_seg;
        *(--stack16) = 0;
        /* adjust stack */
        context->Esp -= 2*sizeof(WORD);
        already = 1;
    }

    if (CurrRMCB) {
        /* RMCB call, invoke protected-mode handler directly */
        DPMI_CallRMCBProc(context, CurrRMCB, dpmi_flag);
        /* check if we returned to where we thought we would */
        if ((context->SegCs != DOSMEM_wrap_seg) ||
            (LOWORD(context->Eip) != 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 {
        TRACE("entering real mode...\n");
        DOSVM_Enter( context );
        TRACE("returned from real-mode call\n");
    }
    if (alloc) DOSMEM_FreeBlock( addr );
    return 0;
}


/**********************************************************************
 *	    CallRMInt   (WINEDOS.@)
 */
void WINAPI DOSVM_CallRMInt( CONTEXT86 *context )
{
    CONTEXT86 realmode_ctx;
    FARPROC16 rm_int = DOSVM_GetRMHandler( BL_reg(context) );
    REALMODECALL *call = MapSL( MAKESEGPTR( context->SegEs, 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... */
        realmode_ctx.SegCs = HIWORD(rm_int);
        realmode_ctx.Eip   = 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... */
        DOSVM_RealModeInterrupt( LOWORD(rm_int)/4, &realmode_ctx );
    }
    INT_SetRealModeContext( call, &realmode_ctx );
}


/**********************************************************************
 *	    CallRMProc   (WINEDOS.@)
 */
void WINAPI DOSVM_CallRMProc( CONTEXT86 *context, int iret )
{
    REALMODECALL *p = MapSL( MAKESEGPTR( context->SegEs, 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)MapSL(MAKESEGPTR(context->SegSs, LOWORD(context->Esp))))+3,
                     CX_reg(context), iret );
    INT_SetRealModeContext(p, &context16);
}


/* (see dosmem.c, function DOSMEM_InitDPMI) */
static void StartPM( CONTEXT86 *context )
{
    UINT16 cs, ss, ds, es;
    CONTEXT86 pm_ctx;
    DWORD psp_ofs = (DWORD)(DOSVM_psp<<4);
    PDB16 *psp = (PDB16 *)psp_ofs;
    HANDLE16 env_seg = psp->environment;
    unsigned char selflags = WINE_LDT_FLAGS_DATA;

    RESET_CFLAG(context);
    dpmi_flag = AX_reg(context);
/* our mode switch wrapper have placed the desired CS into DX */
    cs = SELECTOR_AllocBlock( (void *)(DX_reg(context)<<4), 0x10000, WINE_LDT_FLAGS_CODE );
/* 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. */
    if (dpmi_flag & 1) selflags |= WINE_LDT_FLAGS_32BIT;
    ss = SELECTOR_AllocBlock( (void *)(context->SegSs<<4), 0x10000, selflags );
/* do the same for the data segments, just in case */
    if (context->SegDs == context->SegSs) ds = ss;
    else ds = SELECTOR_AllocBlock( (void *)(context->SegDs<<4), 0x10000, selflags );
    es = SELECTOR_AllocBlock( psp, 0x100, selflags );
/* convert environment pointer, as the spec says, but we're a bit lazy about the size here... */
    psp->environment = SELECTOR_AllocBlock( (void *)(env_seg<<4), 0x10000, WINE_LDT_FLAGS_DATA );

    pm_ctx = *context;
    pm_ctx.SegCs = DOSMEM_dpmi_sel;
/* our mode switch wrapper expects the new CS in DX, and the new SS in AX */
    pm_ctx.Eax   = ss;
    pm_ctx.Edx   = cs;
    pm_ctx.SegDs = ds;
    pm_ctx.SegEs = es;
    pm_ctx.SegFs = 0;
    pm_ctx.SegGs = 0;

    TRACE("DOS program is now entering protected mode\n");
    wine_call_to_16_regs_short(&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... */

    FreeSelector16(psp->environment);
    psp->environment = env_seg;
    FreeSelector16(es);
    if (ds != ss) FreeSelector16(ds);
    FreeSelector16(ss);
    FreeSelector16(cs);
}

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

    if (NewRMCB)
    {
	LPVOID RMCBmem = DOSMEM_GetBlock(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 */
	NewRMCB->address = MAKELONG(0, uParagraph);
	NewRMCB->next = FirstRMCB;
	FirstRMCB = NewRMCB;
    }
    return NewRMCB;
}


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(DOSMEM_MapRealToLinear(CurrRMCB->address));
	HeapFree(GetProcessHeap(), 0, CurrRMCB);
	return 0;
    }
    return 1;
}


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


/* 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));
  rm_ctx.SegDs  = AX_sig(context);
  rm_ctx.SegEs  = CX_sig(context);
  rm_ctx.SegSs  = DX_sig(context);
  rm_ctx.Esp    = EBX_sig(context);
  rm_ctx.SegCs  = SI_sig(context);
  rm_ctx.Eip    = EDI_sig(context);
  rm_ctx.Ebp    = EBP_sig(context);
  rm_ctx.SegFs  = 0;
  rm_ctx.SegGs  = 0;
  rm_ctx.EFlags = EFL_sig(context); /* at least we need the IF flag */

  /* enter real mode again */
  TRACE("re-entering real mode at %04lx:%04lx\n",rm_ctx.SegCs,rm_ctx.Eip);
  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)  = LOWORD(rm_ctx.Eax);
  ES_sig(context)  = LOWORD(rm_ctx.Ecx);
  SS_sig(context)  = LOWORD(rm_ctx.Edx);
  ESP_sig(context) = rm_ctx.Ebx;
  CS_sig(context)  = LOWORD(rm_ctx.Esi);
  EIP_sig(context) = rm_ctx.Edi;
  EBP_sig(context) = rm_ctx.Ebp;
  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


/**********************************************************************
 *	    AllocRMCB   (WINEDOS.@)
 */
void WINAPI DOSVM_AllocRMCB( CONTEXT86 *context )
{
    RMCB *NewRMCB = DPMI_AllocRMCB();

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

    if (NewRMCB)
    {
	/* FIXME: if 32-bit DPMI client, use ESI and EDI */
	NewRMCB->proc_ofs = LOWORD(context->Esi);
	NewRMCB->proc_sel = context->SegDs;
	NewRMCB->regs_ofs = LOWORD(context->Edi);
	NewRMCB->regs_sel = context->SegEs;
	SET_LOWORD( context->Ecx, HIWORD(NewRMCB->address) );
	SET_LOWORD( context->Edx, LOWORD(NewRMCB->address) );
    }
    else
    {
	SET_LOWORD( context->Eax, 0x8015 ); /* callback unavailable */
	SET_CFLAG(context);
    }
}


/**********************************************************************
 *	    FreeRMCB   (WINEDOS.@)
 */
void WINAPI DOSVM_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( context->Eax, 0x8024 ); /* invalid callback address */
	SET_CFLAG(context);
    }
}


/**********************************************************************
 *	    DOSVM_Int31Handler
 *
 * Handler for real-mode int 31h (DPMI).
 */
void WINAPI DOSVM_Int31Handler( CONTEXT86 *context )
{
    /* check if it's our wrapper */
    TRACE("called from real mode\n");
    if (context->SegCs==DOSMEM_dpmi_seg) {
        /* This is the protected mode switch */
        StartPM(context);
        return;
    }
    else if (context->SegCs==DOSMEM_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) != context->SegCs))
            CurrRMCB = CurrRMCB->next;

        if (CurrRMCB) {
            /* RMCB call, propagate to protected-mode handler */
            DPMI_CallRMCBProc(context, CurrRMCB, dpmi_flag);
            return;
        }
    }

    /* chain to protected mode handler */
    INT_Int31Handler( context );
}