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432 lines
12 KiB
C
432 lines
12 KiB
C
/*
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* Copyright (c) 2001 The FreeBSD Project, Inc.
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* All rights reserved.
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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 reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY The FreeBSD Project, Inc. AND CONTRIBUTORS
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* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL The FreeBSD Project, Inc. OR
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* CONTRIBUTORS 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 PROFITS;
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* OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
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* WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
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* OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
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* ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include <sys/cdefs.h>
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__FBSDID("$FreeBSD$");
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#include "doscmd.h"
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#include "video.h"
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static u_int32_t decode_modrm(u_int8_t *, u_int16_t,
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regcontext_t *, int *);
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static u_int8_t *reg8(u_int8_t c, regcontext_t *);
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static u_int16_t *reg16(u_int8_t c, regcontext_t *);
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#if 0
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static u_int32_t *reg32(u_int8_t c, regcontext_t *);
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#endif
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static u_int8_t read_byte(u_int32_t);
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static void write_byte(u_int32_t, u_int8_t);
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static void write_word(u_int32_t, u_int16_t);
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/*
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** Hardware /0 interrupt
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*/
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void
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int00(regcontext_t *REGS __unused)
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{
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debug(D_ALWAYS, "Divide by 0 in DOS program!\n");
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exit(1);
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}
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void
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int01(regcontext_t *REGS __unused)
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{
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debug(D_ALWAYS, "INT 1 with no handler! (single-step/debug)\n");
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}
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void
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int03(regcontext_t *REGS __unused)
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{
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debug(D_ALWAYS, "INT 3 with no handler! (breakpoint)\n");
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}
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void
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int0d(regcontext_t *REGS __unused)
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{
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debug(D_ALWAYS, "IRQ5 with no handler!\n");
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}
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void
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cpu_init(void)
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{
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u_long vec;
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vec = insert_hardint_trampoline();
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ivec[0x00] = vec;
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register_callback(vec, int00, "int 00");
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vec = insert_softint_trampoline();
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ivec[0x01] = vec;
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register_callback(vec, int01, "int 01");
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vec = insert_softint_trampoline();
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ivec[0x03] = vec;
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register_callback(vec, int03, "int 03");
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vec = insert_hardint_trampoline();
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ivec[0x0d] = vec;
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register_callback(vec, int0d, "int 0d");
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vec = insert_null_trampoline();
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ivec[0x34] = vec; /* floating point emulator */
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ivec[0x35] = vec; /* floating point emulator */
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ivec[0x36] = vec; /* floating point emulator */
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ivec[0x37] = vec; /* floating point emulator */
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ivec[0x38] = vec; /* floating point emulator */
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ivec[0x39] = vec; /* floating point emulator */
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ivec[0x3a] = vec; /* floating point emulator */
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ivec[0x3b] = vec; /* floating point emulator */
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ivec[0x3c] = vec; /* floating point emulator */
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ivec[0x3d] = vec; /* floating point emulator */
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ivec[0x3e] = vec; /* floating point emulator */
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ivec[0x3f] = vec; /* floating point emulator */
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}
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/*
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* Emulate CPU instructions. We need this for VGA graphics, at least in the 16
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* color modes.
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*
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* The emulator is far from complete. We are adding the instructions as we
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* encounter them, so this function is likely to change over time. There are
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* no optimizations and we only emulate a single instruction at a time.
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*
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* As long as there is no support for DPMI or the Operand Size Override prefix
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* we won't need the 32-bit registers. This also means that the default
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* operand size is 16 bit.
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*/
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int
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emu_instr(regcontext_t *REGS)
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{
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int prefix = 1;
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u_int8_t *cs = (u_int8_t *)(R_CS << 4);
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int ip = R_IP;
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int dir, i, instrlen;
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u_int8_t *r8;
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u_int8_t val8;
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u_int16_t val16;
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u_int16_t *seg = &R_DS;
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u_int32_t addr, toaddr;
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while (prefix) {
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prefix = 0;
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switch (cs[ip]) {
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case 0x08: /* or r/m8, r8 */
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addr = decode_modrm(cs + ip, *seg, REGS, &instrlen);
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r8 = reg8(cs[ip + 1], REGS);
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val8 = read_byte(addr) | *r8;
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write_byte(addr, val8);
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/* clear carry and overflow; check zero, sign, parity */
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R_EFLAGS &= ~PSL_C | ~PSL_V;
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if (val8 == 0)
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R_EFLAGS |= PSL_Z;
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if (val8 % 2 != 0)
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R_EFLAGS |= PSL_PF;
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if (val8 & 0x80)
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R_EFLAGS |= PSL_N;
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ip += 2 + instrlen;
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break;
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case 0x22: /* and r8, r/m8 */
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addr = decode_modrm(cs + ip, *seg, REGS, &instrlen);
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r8 = reg8(cs[ip + 1], REGS);
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*r8 &= read_byte(addr);
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/* clear carry and overflow; check zero, sign, parity */
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R_EFLAGS &= ~PSL_C | ~PSL_V;
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if (*r8 == 0)
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R_EFLAGS |= PSL_Z;
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if (*r8 % 2 != 0)
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R_EFLAGS |= PSL_PF;
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if (*r8 & 0x80)
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R_EFLAGS |= PSL_N;
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ip += 2 + instrlen;
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break;
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case 0x26: /* Segment Override ES */
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seg = &R_ES;
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prefix = 1;
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ip++;
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break;
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case 0x2e: /* Segment Override CS */
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seg = &R_CS;
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prefix = 1;
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ip++;
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break;
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case 0x36: /* Segment Override SS */
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seg = &R_SS;
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prefix = 1;
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ip++;
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break;
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case 0x3e: /* Segment Override DS */
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seg = &R_DS;
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prefix = 1;
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ip++;
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break;
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case 0x64: /* Segment Override FS */
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seg = &R_FS;
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prefix = 1;
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ip++;
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break;
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case 0x65: /* Segment Override GS */
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seg = &R_GS;
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prefix = 1;
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ip++;
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break;
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case 0x88: /* mov r/m8, r8 */
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addr = decode_modrm(cs + ip, *seg, REGS, &instrlen);
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write_byte(addr, *reg8(cs[ip + 1], REGS));
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ip += 2 + instrlen;
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break;
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case 0x8a: /* mov r8, r/m8 */
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addr = decode_modrm(cs + ip, *seg, REGS, &instrlen);
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r8 = reg8(cs[ip + 1], REGS);
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*r8 = read_byte(addr);
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ip += 2 + instrlen;
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break;
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case 0xc6: /* mov r/m8, imm8 */
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addr = decode_modrm(cs + ip, *seg, REGS, &instrlen);
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write_byte(addr, cs[ip + 2 + instrlen]);
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ip += 2 + instrlen + 1;
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break;
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case 0xc7: /* mov r/m32/16, imm32/16 */
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addr = decode_modrm(cs + ip, *seg, REGS, &instrlen);
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val16 = *(u_int16_t *)&cs[ip + 2 + instrlen];
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write_word(addr, val16);
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ip += 2 + instrlen + 2;
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break;
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case 0xa4: /* movs m8, m8 */
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write_byte(MAKEPTR(R_ES, R_DI), read_byte(MAKEPTR(*seg, R_SI)));
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dir = (R_EFLAGS & PSL_D) ? -1 : 1;
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R_DI += dir;
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R_SI += dir;
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ip++;
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break;
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case 0xaa: /* stos m8 */
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addr = MAKEPTR(R_ES, R_DI);
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write_byte(addr, R_AL);
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R_DI += (R_EFLAGS & PSL_D) ? -1 : 1;
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ip++;
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break;
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case 0xab: /* stos m32/16*/
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addr = MAKEPTR(R_ES, R_DI);
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write_word(addr, R_AX);
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R_DI += (R_EFLAGS & PSL_D) ? -2 : 2;
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ip++;
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break;
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case 0xf3: /* rep */
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switch (cs[++ip]) {
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case 0xa4: /* movs m8, m8 */
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/* XXX Possible optimization: if both source and target
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addresses lie within the video memory and write mode 1 is
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selected, we can use memcpy(). */
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dir = (R_EFLAGS & PSL_D) ? -1 : 1;
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addr = MAKEPTR(R_ES, R_DI);
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toaddr = MAKEPTR(*seg, R_SI);
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for (i = R_CX; i > 0; i--) {
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write_byte(addr, read_byte(toaddr));
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addr += dir;
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toaddr += dir;
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}
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PUTPTR(R_ES, R_DI, addr);
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PUTPTR(*seg, R_SI, toaddr);
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ip++;
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break;
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case 0xaa: /* stos m8 */
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/* direction */
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dir = (R_EFLAGS & PSL_D) ? -1 : 1;
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addr = MAKEPTR(R_ES, R_DI);
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for (i = R_CX; i > 0; i--) {
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write_byte(addr, R_AL);
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addr += dir;
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}
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PUTPTR(R_ES, R_DI, addr);
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ip++;
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break;
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case 0xab: /* stos m32/16 */
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/* direction */
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dir = (R_EFLAGS & PSL_D) ? -2 : 2;
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addr = MAKEPTR(R_ES, R_DI);
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for (i = R_CX; i > 0; i--) {
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write_word(addr, R_AX);
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addr += dir;
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}
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PUTPTR(R_ES, R_DI, addr);
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ip++;
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break;
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default:
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R_IP = --ip; /* Move IP back to the 'rep' instruction. */
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return -1;
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}
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R_CX = 0;
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break;
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default:
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/* Unknown instruction, get out of here and let trap.c:sigbus()
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catch it. */
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return -1;
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}
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R_IP = ip;
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}
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return 0;
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}
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/* Decode the ModR/M byte. Returns the memory address of the operand. 'c'
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points to the current instruction, 'seg' contains the value for the current
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base segment; this is usually 'DS', but may have been changed by a segment
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override prefix. We return the length of the current instruction in
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'instrlen' so we can adjust 'IP' on return.
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XXX We will probably need a second function for 32-bit instructions.
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XXX We do not check for undefined combinations, like Mod=01, R/M=001. */
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static u_int32_t
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decode_modrm(u_int8_t *c, u_int16_t seg, regcontext_t *REGS, int *instrlen)
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{
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u_int32_t addr = 0; /* absolute address */
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int16_t dspl = 0; /* displacement, signed */
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*instrlen = 0;
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switch (c[1] & 0xc0) { /* decode Mod */
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case 0x00: /* DS:[reg] */
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/* 'reg' is selected in the R/M bits */
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break;
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case 0x40: /* 8 bit displacement */
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dspl = (int16_t)(int8_t)c[2];
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*instrlen = 1;
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break;
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case 0x80: /* 16 bit displacement */
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dspl = *(int16_t *)&c[2];
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*instrlen = 2;
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break;
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case 0xc0: /* reg in R/M */
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if (c[0] & 1) /* 16-bit reg */
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return *reg16(c[1], REGS);
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else /* 8-bit reg */
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return *reg8(c[1], REGS);
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break;
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}
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switch (c[1] & 0x07) { /* decode R/M */
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case 0x00:
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addr = MAKEPTR(seg, R_BX + R_SI);
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break;
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case 0x01:
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addr = MAKEPTR(seg, R_BX + R_DI);
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break;
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case 0x02:
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addr = MAKEPTR(seg, R_BP + R_SI);
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break;
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case 0x03:
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addr = MAKEPTR(seg, R_BP + R_DI);
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break;
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case 0x04:
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addr = MAKEPTR(seg, R_SI);
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break;
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case 0x05:
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addr = MAKEPTR(seg, R_DI);
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break;
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case 0x06:
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if ((c[1] & 0xc0) >= 0x40)
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addr += R_BP;
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else {
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addr = MAKEPTR(seg, *(int16_t *)&c[2]);
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*instrlen = 2;
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}
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break;
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case 0x07:
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addr = MAKEPTR(seg, R_BX + dspl);
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break;
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}
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return addr;
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}
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static u_int8_t *
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reg8(u_int8_t c, regcontext_t *REGS)
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{
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u_int8_t *r8[] = {&R_AL, &R_CL, &R_DL, &R_BL,
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&R_AH, &R_CH, &R_DH, &R_BH};
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/* select 'rrr' bits in ModR/M */
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return r8[(c & 0x38) >> 3];
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}
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static u_int16_t *
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reg16(u_int8_t c, regcontext_t *REGS)
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{
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u_int16_t *r16[] = {&R_AX, &R_CX, &R_DX, &R_BX,
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&R_SP, &R_BP, &R_SI, &R_DI};
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return r16[(c & 0x38) >> 3];
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}
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#if 0
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/* not yet */
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static u_int32_t *
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reg32(u_int8_t c, regcontext_t *REGS)
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{
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u_int32_t *r32[] = {&R_EAX, &R_ECX, &R_EDX, &R_EBX,
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&R_ESP, &R_EBP, &R_ESI, &R_EDI};
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return r32[(c & 0x38) >> 3];
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}
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#endif
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/* Read an 8-bit value from the location specified by 'addr'. If 'addr' lies
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within the video memory, we call 'video.c:vga_read()'. */
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static u_int8_t
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read_byte(u_int32_t addr)
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{
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if (addr >= 0xa0000 && addr < 0xb0000)
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return vga_read(addr);
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else
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return *(u_int8_t *)addr;
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}
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/* Write an 8-bit value to the location specified by 'addr'. If 'addr' lies
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within the video memory region, we call 'video.c:vga_write()'. */
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static void
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write_byte(u_int32_t addr, u_int8_t val)
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{
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if (addr >= 0xa0000 && addr < 0xb0000)
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vga_write(addr, val);
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else
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*(u_int8_t *)addr = val;
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return;
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}
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/* Write a 16-bit value to the location specified by 'addr'. If 'addr' lies
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within the video memory region, we call 'video.c:vga_write()'. */
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static void
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write_word(u_int32_t addr, u_int16_t val)
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{
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if (addr >= 0xa0000 && addr < 0xb0000) {
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vga_write(addr, (u_int8_t)(val & 0xff));
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vga_write(addr + 1, (u_int8_t)((val & 0xff00) >> 8));
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} else
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*(u_int16_t *)addr = val;
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return;
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}
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