/* $OpenBSD: get_address.c,v 1.1 1996/08/27 10:32:51 downsj Exp $ */ /* * get_address.c * * Get the effective address from an FPU instruction. * * * Copyright (C) 1992,1993,1994 * W. Metzenthen, 22 Parker St, Ormond, Vic 3163, * Australia. E-mail billm@vaxc.cc.monash.edu.au * All rights reserved. * * This copyright notice covers the redistribution and use of the * FPU emulator developed by W. Metzenthen. It covers only its use * in the 386BSD, FreeBSD and NetBSD operating systems. Any other * use is not permitted under this copyright. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must include information specifying * that source code for the emulator is freely available and include * either: * a) an offer to provide the source code for a nominal distribution * fee, or * b) list at least two alternative methods whereby the source * can be obtained, e.g. a publically accessible bulletin board * and an anonymous ftp site from which the software can be * downloaded. * 3. All advertising materials specifically mentioning features or use of * this emulator must acknowledge that it was developed by W. Metzenthen. * 4. The name of W. Metzenthen may not be used to endorse or promote * products derived from this software without specific prior written * permission. * * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY * AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL * W. METZENTHEN BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. * * * The purpose of this copyright, based upon the Berkeley copyright, is to * ensure that the covered software remains freely available to everyone. * * The software (with necessary differences) is also available, but under * the terms of the GNU copyleft, for the Linux operating system and for * the djgpp ms-dos extender. * * W. Metzenthen June 1994. * * * $FreeBSD: get_address.c,v 1.3 1994/06/10 07:44:29 rich Exp $ * */ /*---------------------------------------------------------------------------+ | 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 #include #include #include #include #include #include #include #include static int reg_offset[] = { tEAX, tECX, tEDX, tEBX, tESP, tEBP, tESI, tEDI}; #define REG_(x) (*(((int*)FPU_info) + reg_offset[(x)])) void *FPU_data_address; /* Decode the SIB byte. This function assumes mod != 0 */ static void * sib(int mod) { unsigned char ss, index, base; long offset; REENTRANT_CHECK(OFF); base = fubyte((char *) FPU_EIP); /* The SIB byte */ REENTRANT_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 */ REENTRANT_CHECK(OFF); offset += (signed char) fubyte((char *) FPU_EIP); REENTRANT_CHECK(ON); FPU_EIP++; } else if (mod == 2 || base == 5) { /* The second condition also * has mod==0 */ /* 32 bit displacment */ REENTRANT_CHECK(OFF); offset += (signed) fuword((unsigned long *) FPU_EIP); REENTRANT_CHECK(ON); FPU_EIP += 4; } return (void *) offset; } /* 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 get_address(unsigned char FPU_modrm) { unsigned char mod; long *cpu_reg_ptr; int offset = 0; /* Initialized just to stop compiler warnings. */ mod = (FPU_modrm >> 6) & 3; if (FPU_rm == 4 && mod != 3) { FPU_data_address = sib(mod); return; } cpu_reg_ptr = (long *) ®_(FPU_rm); switch (mod) { case 0: if (FPU_rm == 5) { /* Special case: disp32 */ REENTRANT_CHECK(OFF); offset = fuword((unsigned long *) FPU_EIP); REENTRANT_CHECK(ON); FPU_EIP += 4; FPU_data_address = (void *) offset; return; } else { FPU_data_address = (void *) *cpu_reg_ptr; /* Just return the * contents of the cpu * register */ return; } case 1: /* 8 bit signed displacement */ REENTRANT_CHECK(OFF); offset = (signed char) fubyte((char *) FPU_EIP); REENTRANT_CHECK(ON); FPU_EIP++; break; case 2: /* 32 bit displacement */ REENTRANT_CHECK(OFF); offset = (signed) fuword((unsigned long *) FPU_EIP); REENTRANT_CHECK(ON); FPU_EIP += 4; break; case 3: /* Not legal for the FPU */ EXCEPTION(EX_Invalid); } FPU_data_address = offset + (char *) *cpu_reg_ptr; }