freebsd-dev/usr.bin/doscmd/cpu.c
Thomas Gellekum 86c393fc09 - Add some more x86 instructions to emulate,
- emulate VGA read mode 0,
- emulate VGA write mode 1,
- minor cleanup.

Protel's Easytrax, a free PCB layout program, almost runs now; there are
still some problems with the keyboard emulation, but the graphics are fine
(albeit a bit slow).
2001-07-30 12:03:38 +00:00

430 lines
11 KiB
C

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