204 lines
6.0 KiB
C
204 lines
6.0 KiB
C
/*
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* get_address.c
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*
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* Get the effective address from an FPU instruction.
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*
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*
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* Copyright (C) 1992,1993,1994
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* W. Metzenthen, 22 Parker St, Ormond, Vic 3163,
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* Australia. E-mail billm@vaxc.cc.monash.edu.au
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* All rights reserved.
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*
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* This copyright notice covers the redistribution and use of the
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* FPU emulator developed by W. Metzenthen. It covers only its use
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* in the 386BSD, FreeBSD and NetBSD operating systems. Any other
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* use is not permitted under this copyright.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must include information specifying
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* that source code for the emulator is freely available and include
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* either:
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* a) an offer to provide the source code for a nominal distribution
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* fee, or
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* b) list at least two alternative methods whereby the source
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* can be obtained, e.g. a publically accessible bulletin board
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* and an anonymous ftp site from which the software can be
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* downloaded.
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* 3. All advertising materials specifically mentioning features or use of
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* this emulator must acknowledge that it was developed by W. Metzenthen.
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* 4. The name of W. Metzenthen may not be used to endorse or promote
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* products derived from this software without specific prior written
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* permission.
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*
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* THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES,
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* INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
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* AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
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* W. METZENTHEN BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
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* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
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* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
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* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
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* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
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* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
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* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*
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*
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* The purpose of this copyright, based upon the Berkeley copyright, is to
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* ensure that the covered software remains freely available to everyone.
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*
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* The software (with necessary differences) is also available, but under
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* the terms of the GNU copyleft, for the Linux operating system and for
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* the djgpp ms-dos extender.
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*
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* W. Metzenthen June 1994.
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*
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*
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* $Id: get_address.c,v 1.3 1994/06/10 07:44:29 rich Exp $
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*
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*/
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/*---------------------------------------------------------------------------+
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| Note: |
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| The file contains code which accesses user memory. |
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| Emulator static data may change when user memory is accessed, due to |
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| other processes using the emulator while swapping is in progress. |
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+---------------------------------------------------------------------------*/
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#include <sys/param.h>
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#include <sys/proc.h>
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#include <sys/systm.h>
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#include <machine/cpu.h>
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#include <machine/pcb.h>
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#include <machine/reg.h>
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#include <gnu/i386/fpemul/fpu_emu.h>
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#include <gnu/i386/fpemul/fpu_system.h>
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#include <gnu/i386/fpemul/exception.h>
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static int reg_offset[] = {
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tEAX, tECX, tEDX, tEBX, tESP, tEBP, tESI, tEDI};
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#define REG_(x) (*(((int*)FPU_info) + reg_offset[(x)]))
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void *FPU_data_address;
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/* Decode the SIB byte. This function assumes mod != 0 */
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static void *
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sib(int mod)
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{
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unsigned char ss, index, base;
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long offset;
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REENTRANT_CHECK(OFF);
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base = fubyte((char *) FPU_EIP); /* The SIB byte */
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REENTRANT_CHECK(ON);
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FPU_EIP++;
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ss = base >> 6;
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index = (base >> 3) & 7;
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base &= 7;
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if ((mod == 0) && (base == 5))
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offset = 0; /* No base register */
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else
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offset = REG_(base);
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if (index == 4) {
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/* No index register */
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/* A non-zero ss is illegal */
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if (ss)
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EXCEPTION(EX_Invalid);
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} else {
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offset += (REG_(index)) << ss;
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}
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if (mod == 1) {
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/* 8 bit signed displacement */
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REENTRANT_CHECK(OFF);
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offset += (signed char) fubyte((char *) FPU_EIP);
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REENTRANT_CHECK(ON);
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FPU_EIP++;
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} else
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if (mod == 2 || base == 5) { /* The second condition also
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* has mod==0 */
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/* 32 bit displacment */
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REENTRANT_CHECK(OFF);
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offset += (signed) fuword((unsigned long *) FPU_EIP);
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REENTRANT_CHECK(ON);
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FPU_EIP += 4;
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}
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return (void *) offset;
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}
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/*
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MOD R/M byte: MOD == 3 has a special use for the FPU
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SIB byte used iff R/M = 100b
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7 6 5 4 3 2 1 0
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..... ......... .........
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MOD OPCODE(2) R/M
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SIB byte
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7 6 5 4 3 2 1 0
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..... ......... .........
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SS INDEX BASE
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*/
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void
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get_address(unsigned char FPU_modrm)
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{
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unsigned char mod;
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long *cpu_reg_ptr;
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int offset = 0; /* Initialized just to stop compiler warnings. */
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mod = (FPU_modrm >> 6) & 3;
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if (FPU_rm == 4 && mod != 3) {
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FPU_data_address = sib(mod);
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return;
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}
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cpu_reg_ptr = (long *) ®_(FPU_rm);
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switch (mod) {
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case 0:
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if (FPU_rm == 5) {
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/* Special case: disp32 */
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REENTRANT_CHECK(OFF);
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offset = fuword((unsigned long *) FPU_EIP);
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REENTRANT_CHECK(ON);
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FPU_EIP += 4;
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FPU_data_address = (void *) offset;
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return;
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} else {
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FPU_data_address = (void *) *cpu_reg_ptr; /* Just return the
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* contents of the cpu
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* register */
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return;
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}
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case 1:
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/* 8 bit signed displacement */
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REENTRANT_CHECK(OFF);
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offset = (signed char) fubyte((char *) FPU_EIP);
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REENTRANT_CHECK(ON);
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FPU_EIP++;
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break;
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case 2:
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/* 32 bit displacement */
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REENTRANT_CHECK(OFF);
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offset = (signed) fuword((unsigned long *) FPU_EIP);
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REENTRANT_CHECK(ON);
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FPU_EIP += 4;
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break;
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case 3:
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/* Not legal for the FPU */
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EXCEPTION(EX_Invalid);
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}
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FPU_data_address = offset + (char *) *cpu_reg_ptr;
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}
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