/*---------------------------------------------------------------------------+
   |  get_address.c                                                            |
   |                                                                           |
   | Get the effective address from an FPU instruction.                        |
   |                                                                           |
   | Copyright (C) 1992,1993,1994,1997                                         |
   |                       W. Metzenthen, 22 Parker St, Ormond, Vic 3163,      |
   |                       Australia.  E-mail   billm@suburbia.net             |
   |                                                                           |
   |                                                                           |
   +---------------------------------------------------------------------------*/
  
  /*---------------------------------------------------------------------------+
   | Note:                                                                     |
   |    The file contains code which accesses user memory.                     |
   |    Emulator static data may change when user memory is accessed, due to   |
   |    other processes using the emulator while swapping is in progress.      |
   +---------------------------------------------------------------------------*/

  #include <linux/stddef.h>
  
  #include <asm/uaccess.h>
  #include <asm/desc.h>
  
  #include "fpu_system.h"
  #include "exception.h"
  #include "fpu_emu.h"

  #define FPU_WRITE_BIT 0x10
  
  static int reg_offset[] = {

  	offsetof(struct pt_regs, ax),
  	offsetof(struct pt_regs, cx),
  	offsetof(struct pt_regs, dx),
  	offsetof(struct pt_regs, bx),
  	offsetof(struct pt_regs, sp),
  	offsetof(struct pt_regs, bp),
  	offsetof(struct pt_regs, si),
  	offsetof(struct pt_regs, di)

  };

  #define REG_(x) (*(long *)(reg_offset[(x)] + (u_char *)FPU_info->regs))

  
  static int reg_offset_vm86[] = {

  	offsetof(struct pt_regs, cs),
  	offsetof(struct kernel_vm86_regs, ds),
  	offsetof(struct kernel_vm86_regs, es),
  	offsetof(struct kernel_vm86_regs, fs),
  	offsetof(struct kernel_vm86_regs, gs),
  	offsetof(struct pt_regs, ss),
  	offsetof(struct kernel_vm86_regs, ds)

  };

  
  #define VM86_REG_(x) (*(unsigned short *) \

  		(reg_offset_vm86[((unsigned)x)] + (u_char *)FPU_info->regs))

  static int reg_offset_pm[] = {

  	offsetof(struct pt_regs, cs),
  	offsetof(struct pt_regs, ds),
  	offsetof(struct pt_regs, es),
  	offsetof(struct pt_regs, fs),
  	offsetof(struct pt_regs, ds),	/* dummy, not saved on stack */
  	offsetof(struct pt_regs, ss),
  	offsetof(struct pt_regs, ds)

  };

  
  #define PM_REG_(x) (*(unsigned short *) \

  		(reg_offset_pm[((unsigned)x)] + (u_char *)FPU_info->regs))

  /* Decode the SIB byte. This function assumes mod != 0 */
  static int sib(int mod, unsigned long *fpu_eip)
  {

  	u_char ss, index, base;
  	long offset;
  
  	RE_ENTRANT_CHECK_OFF;
  	FPU_code_access_ok(1);
  	FPU_get_user(base, (u_char __user *) (*fpu_eip));	/* The SIB byte */
  	RE_ENTRANT_CHECK_ON;
  	(*fpu_eip)++;
  	ss = base >> 6;
  	index = (base >> 3) & 7;
  	base &= 7;
  
  	if ((mod == 0) && (base == 5))
  		offset = 0;	/* No base register */
  	else
  		offset = REG_(base);
  
  	if (index == 4) {
  		/* No index register */
  		/* A non-zero ss is illegal */
  		if (ss)
  			EXCEPTION(EX_Invalid);
  	} else {
  		offset += (REG_(index)) << ss;
  	}
  
  	if (mod == 1) {
  		/* 8 bit signed displacement */
  		long displacement;
  		RE_ENTRANT_CHECK_OFF;
  		FPU_code_access_ok(1);
  		FPU_get_user(displacement, (signed char __user *)(*fpu_eip));
  		offset += displacement;
  		RE_ENTRANT_CHECK_ON;
  		(*fpu_eip)++;
  	} else if (mod == 2 || base == 5) {	/* The second condition also has mod==0 */
  		/* 32 bit displacement */
  		long displacement;
  		RE_ENTRANT_CHECK_OFF;
  		FPU_code_access_ok(4);
  		FPU_get_user(displacement, (long __user *)(*fpu_eip));
  		offset += displacement;
  		RE_ENTRANT_CHECK_ON;
  		(*fpu_eip) += 4;
  	}

  	return offset;
  }

  static unsigned long vm86_segment(u_char segment, struct address *addr)

  {

  	segment--;

  #ifdef PARANOID

  	if (segment > PREFIX_SS_) {
  		EXCEPTION(EX_INTERNAL | 0x130);
  		math_abort(FPU_info, SIGSEGV);
  	}

  #endif /* PARANOID */

  	addr->selector = VM86_REG_(segment);
  	return (unsigned long)VM86_REG_(segment) << 4;

  }

  /* This should work for 16 and 32 bit protected mode. */
  static long pm_address(u_char FPU_modrm, u_char segment,
  		       struct address *addr, long offset)

  {
  	struct desc_struct descriptor;
  	unsigned long base_address, limit, address, seg_top;

  	segment--;

  
  #ifdef PARANOID

  	/* segment is unsigned, so this also detects if segment was 0: */
  	if (segment > PREFIX_SS_) {
  		EXCEPTION(EX_INTERNAL | 0x132);
  		math_abort(FPU_info, SIGSEGV);
  	}

  #endif /* PARANOID */

  	switch (segment) {

  	case PREFIX_GS_ - 1:

  		/* user gs handling can be lazy, use special accessors */
  		addr->selector = get_user_gs(FPU_info->regs);

  		break;
  	default:
  		addr->selector = PM_REG_(segment);

  	}

  	descriptor = LDT_DESCRIPTOR(PM_REG_(segment));
  	base_address = SEG_BASE_ADDR(descriptor);
  	address = base_address + offset;
  	limit = base_address
  	    + (SEG_LIMIT(descriptor) + 1) * SEG_GRANULARITY(descriptor) - 1;
  	if (limit < base_address)
  		limit = 0xffffffff;
  
  	if (SEG_EXPAND_DOWN(descriptor)) {
  		if (SEG_G_BIT(descriptor))
  			seg_top = 0xffffffff;
  		else {
  			seg_top = base_address + (1 << 20);
  			if (seg_top < base_address)
  				seg_top = 0xffffffff;
  		}
  		access_limit =
  		    (address <= limit) || (address >= seg_top) ? 0 :
  		    ((seg_top - address) >= 255 ? 255 : seg_top - address);
  	} else {
  		access_limit =
  		    (address > limit) || (address < base_address) ? 0 :
  		    ((limit - address) >= 254 ? 255 : limit - address + 1);
  	}
  	if (SEG_EXECUTE_ONLY(descriptor) ||
  	    (!SEG_WRITE_PERM(descriptor) && (FPU_modrm & FPU_WRITE_BIT))) {
  		access_limit = 0;
  	}
  	return address;
  }

  
  /*
         MOD R/M byte:  MOD == 3 has a special use for the FPU
                        SIB byte used iff R/M = 100b
  
         7   6   5   4   3   2   1   0
         .....   .........   .........
          MOD    OPCODE(2)     R/M

         SIB byte
  
         7   6   5   4   3   2   1   0
         .....   .........   .........
          SS      INDEX        BASE
  
  */
  
  void __user *FPU_get_address(u_char FPU_modrm, unsigned long *fpu_eip,

  			     struct address *addr, fpu_addr_modes addr_modes)
  {
  	u_char mod;
  	unsigned rm = FPU_modrm & 7;
  	long *cpu_reg_ptr;
  	int address = 0;	/* Initialized just to stop compiler warnings. */
  
  	/* Memory accessed via the cs selector is write protected
  	   in `non-segmented' 32 bit protected mode. */
  	if (!addr_modes.default_mode && (FPU_modrm & FPU_WRITE_BIT)
  	    && (addr_modes.override.segment == PREFIX_CS_)) {
  		math_abort(FPU_info, SIGSEGV);
  	}
  
  	addr->selector = FPU_DS;	/* Default, for 32 bit non-segmented mode. */
  
  	mod = (FPU_modrm >> 6) & 3;
  
  	if (rm == 4 && mod != 3) {
  		address = sib(mod, fpu_eip);
  	} else {
  		cpu_reg_ptr = &REG_(rm);
  		switch (mod) {
  		case 0:
  			if (rm == 5) {
  				/* Special case: disp32 */
  				RE_ENTRANT_CHECK_OFF;
  				FPU_code_access_ok(4);
  				FPU_get_user(address,
  					     (unsigned long __user
  					      *)(*fpu_eip));
  				(*fpu_eip) += 4;
  				RE_ENTRANT_CHECK_ON;
  				addr->offset = address;
  				return (void __user *)address;
  			} else {
  				address = *cpu_reg_ptr;	/* Just return the contents
  							   of the cpu register */
  				addr->offset = address;
  				return (void __user *)address;
  			}
  		case 1:
  			/* 8 bit signed displacement */
  			RE_ENTRANT_CHECK_OFF;
  			FPU_code_access_ok(1);
  			FPU_get_user(address, (signed char __user *)(*fpu_eip));
  			RE_ENTRANT_CHECK_ON;
  			(*fpu_eip)++;
  			break;
  		case 2:
  			/* 32 bit displacement */
  			RE_ENTRANT_CHECK_OFF;
  			FPU_code_access_ok(4);
  			FPU_get_user(address, (long __user *)(*fpu_eip));
  			(*fpu_eip) += 4;
  			RE_ENTRANT_CHECK_ON;
  			break;
  		case 3:
  			/* Not legal for the FPU */
  			EXCEPTION(EX_Invalid);
  		}
  		address += *cpu_reg_ptr;
  	}
  
  	addr->offset = address;
  
  	switch (addr_modes.default_mode) {
  	case 0:
  		break;
  	case VM86:
  		address += vm86_segment(addr_modes.override.segment, addr);
  		break;
  	case PM16:
  	case SEG32:
  		address = pm_address(FPU_modrm, addr_modes.override.segment,
  				     addr, address);
  		break;
  	default:
  		EXCEPTION(EX_INTERNAL | 0x133);
  	}
  
  	return (void __user *)address;
  }
  
  void __user *FPU_get_address_16(u_char FPU_modrm, unsigned long *fpu_eip,
  				struct address *addr, fpu_addr_modes addr_modes)

  {

  	u_char mod;
  	unsigned rm = FPU_modrm & 7;
  	int address = 0;	/* Default used for mod == 0 */
  
  	/* Memory accessed via the cs selector is write protected
  	   in `non-segmented' 32 bit protected mode. */
  	if (!addr_modes.default_mode && (FPU_modrm & FPU_WRITE_BIT)
  	    && (addr_modes.override.segment == PREFIX_CS_)) {
  		math_abort(FPU_info, SIGSEGV);
  	}
  
  	addr->selector = FPU_DS;	/* Default, for 32 bit non-segmented mode. */
  
  	mod = (FPU_modrm >> 6) & 3;
  
  	switch (mod) {

  	case 0:

  		if (rm == 6) {
  			/* Special case: disp16 */
  			RE_ENTRANT_CHECK_OFF;
  			FPU_code_access_ok(2);
  			FPU_get_user(address,
  				     (unsigned short __user *)(*fpu_eip));
  			(*fpu_eip) += 2;
  			RE_ENTRANT_CHECK_ON;
  			goto add_segment;
  		}
  		break;

  	case 1:

  		/* 8 bit signed displacement */
  		RE_ENTRANT_CHECK_OFF;
  		FPU_code_access_ok(1);
  		FPU_get_user(address, (signed char __user *)(*fpu_eip));
  		RE_ENTRANT_CHECK_ON;
  		(*fpu_eip)++;
  		break;

  	case 2:

  		/* 16 bit displacement */
  		RE_ENTRANT_CHECK_OFF;
  		FPU_code_access_ok(2);
  		FPU_get_user(address, (unsigned short __user *)(*fpu_eip));
  		(*fpu_eip) += 2;
  		RE_ENTRANT_CHECK_ON;
  		break;

  	case 3:

  		/* Not legal for the FPU */
  		EXCEPTION(EX_Invalid);
  		break;
  	}
  	switch (rm) {
  	case 0:

  		address += FPU_info->regs->bx + FPU_info->regs->si;

  		break;
  	case 1:

  		address += FPU_info->regs->bx + FPU_info->regs->di;

  		break;
  	case 2:

  		address += FPU_info->regs->bp + FPU_info->regs->si;

  		if (addr_modes.override.segment == PREFIX_DEFAULT)
  			addr_modes.override.segment = PREFIX_SS_;
  		break;
  	case 3:

  		address += FPU_info->regs->bp + FPU_info->regs->di;

  		if (addr_modes.override.segment == PREFIX_DEFAULT)
  			addr_modes.override.segment = PREFIX_SS_;
  		break;
  	case 4:

  		address += FPU_info->regs->si;

  		break;
  	case 5:

  		address += FPU_info->regs->di;

  		break;
  	case 6:

  		address += FPU_info->regs->bp;

  		if (addr_modes.override.segment == PREFIX_DEFAULT)
  			addr_modes.override.segment = PREFIX_SS_;
  		break;
  	case 7:

  		address += FPU_info->regs->bx;

  		break;

  	}

        add_segment:
  	address &= 0xffff;

  	addr->offset = address;
  
  	switch (addr_modes.default_mode) {
  	case 0:
  		break;
  	case VM86:
  		address += vm86_segment(addr_modes.override.segment, addr);
  		break;
  	case PM16:
  	case SEG32:
  		address = pm_address(FPU_modrm, addr_modes.override.segment,
  				     addr, address);
  		break;
  	default:
  		EXCEPTION(EX_INTERNAL | 0x131);

  	}

  
  	return (void __user *)address;

  }