vm86.c

qemu虚拟机代码

/*
 *  vm86 linux syscall support
 * 
 *  Copyright (c) 2003 Fabrice Bellard
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */
#include <stdlib.h>
#include <stdio.h>
#include <stdarg.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>

#include "qemu.h"

//#define DEBUG_VM86

#define set_flags(X,new,mask) \
((X) = ((X) & ~(mask)) | ((new) & (mask)))

#define SAFE_MASK	(0xDD5)
#define RETURN_MASK	(0xDFF)

static inline int is_revectored(int nr, struct target_revectored_struct *bitmap)
{
    return (((uint8_t *)bitmap)[nr >> 3] >> (nr & 7)) & 1;
}

static inline void vm_putw(uint8_t *segptr, unsigned int reg16, unsigned int val)
{
    stw(segptr + (reg16 & 0xffff), val);
}

static inline void vm_putl(uint8_t *segptr, unsigned int reg16, unsigned int val)
{
    stl(segptr + (reg16 & 0xffff), val);
}

static inline unsigned int vm_getw(uint8_t *segptr, unsigned int reg16)
{
    return lduw(segptr + (reg16 & 0xffff));
}

static inline unsigned int vm_getl(uint8_t *segptr, unsigned int reg16)
{
    return ldl(segptr + (reg16 & 0xffff));
}

void save_v86_state(CPUX86State *env)
{
    TaskState *ts = env->opaque;
    struct target_vm86plus_struct * target_v86;

    lock_user_struct(target_v86, ts->target_v86, 0);
    /* put the VM86 registers in the userspace register structure */
    target_v86->regs.eax = tswap32(env->regs[R_EAX]);
    target_v86->regs.ebx = tswap32(env->regs[R_EBX]);
    target_v86->regs.ecx = tswap32(env->regs[R_ECX]);
    target_v86->regs.edx = tswap32(env->regs[R_EDX]);
    target_v86->regs.esi = tswap32(env->regs[R_ESI]);
    target_v86->regs.edi = tswap32(env->regs[R_EDI]);
    target_v86->regs.ebp = tswap32(env->regs[R_EBP]);
    target_v86->regs.esp = tswap32(env->regs[R_ESP]);
    target_v86->regs.eip = tswap32(env->eip);
    target_v86->regs.cs = tswap16(env->segs[R_CS].selector);
    target_v86->regs.ss = tswap16(env->segs[R_SS].selector);
    target_v86->regs.ds = tswap16(env->segs[R_DS].selector);
    target_v86->regs.es = tswap16(env->segs[R_ES].selector);
    target_v86->regs.fs = tswap16(env->segs[R_FS].selector);
    target_v86->regs.gs = tswap16(env->segs[R_GS].selector);
    set_flags(env->eflags, ts->v86flags, VIF_MASK | ts->v86mask);
    target_v86->regs.eflags = tswap32(env->eflags);
    unlock_user_struct(target_v86, ts->target_v86, 1);
#ifdef DEBUG_VM86
    fprintf(logfile, "save_v86_state: eflags=%08x cs:ip=%04x:%04x\n", 
            env->eflags, env->segs[R_CS].selector, env->eip);
#endif

    /* restore 32 bit registers */
    env->regs[R_EAX] = ts->vm86_saved_regs.eax;
    env->regs[R_EBX] = ts->vm86_saved_regs.ebx;
    env->regs[R_ECX] = ts->vm86_saved_regs.ecx;
    env->regs[R_EDX] = ts->vm86_saved_regs.edx;
    env->regs[R_ESI] = ts->vm86_saved_regs.esi;
    env->regs[R_EDI] = ts->vm86_saved_regs.edi;
    env->regs[R_EBP] = ts->vm86_saved_regs.ebp;
    env->regs[R_ESP] = ts->vm86_saved_regs.esp;
    env->eflags = ts->vm86_saved_regs.eflags;
    env->eip = ts->vm86_saved_regs.eip;

    cpu_x86_load_seg(env, R_CS, ts->vm86_saved_regs.cs);
    cpu_x86_load_seg(env, R_SS, ts->vm86_saved_regs.ss);
    cpu_x86_load_seg(env, R_DS, ts->vm86_saved_regs.ds);
    cpu_x86_load_seg(env, R_ES, ts->vm86_saved_regs.es);
    cpu_x86_load_seg(env, R_FS, ts->vm86_saved_regs.fs);
    cpu_x86_load_seg(env, R_GS, ts->vm86_saved_regs.gs);
}

/* return from vm86 mode to 32 bit. The vm86() syscall will return
   'retval' */
static inline void return_to_32bit(CPUX86State *env, int retval)
{
#ifdef DEBUG_VM86
    fprintf(logfile, "return_to_32bit: ret=0x%x\n", retval);
#endif
    save_v86_state(env);
    env->regs[R_EAX] = retval;
}

static inline int set_IF(CPUX86State *env)
{
    TaskState *ts = env->opaque;
    
    ts->v86flags |= VIF_MASK;
    if (ts->v86flags & VIP_MASK) {
        return_to_32bit(env, TARGET_VM86_STI);
        return 1;
    }
    return 0;
}

static inline void clear_IF(CPUX86State *env)
{
    TaskState *ts = env->opaque;

    ts->v86flags &= ~VIF_MASK;
}

static inline void clear_TF(CPUX86State *env)
{
    env->eflags &= ~TF_MASK;
}

static inline void clear_AC(CPUX86State *env)
{
    env->eflags &= ~AC_MASK;
}

static inline int set_vflags_long(unsigned long eflags, CPUX86State *env)
{
    TaskState *ts = env->opaque;

    set_flags(ts->v86flags, eflags, ts->v86mask);
    set_flags(env->eflags, eflags, SAFE_MASK);
    if (eflags & IF_MASK)
        return set_IF(env);
    else
        clear_IF(env);
    return 0;
}

static inline int set_vflags_short(unsigned short flags, CPUX86State *env)
{
    TaskState *ts = env->opaque;

    set_flags(ts->v86flags, flags, ts->v86mask & 0xffff);
    set_flags(env->eflags, flags, SAFE_MASK);
    if (flags & IF_MASK)
        return set_IF(env);
    else
        clear_IF(env);
    return 0;
}

static inline unsigned int get_vflags(CPUX86State *env)
{
    TaskState *ts = env->opaque;
    unsigned int flags;

    flags = env->eflags & RETURN_MASK;
    if (ts->v86flags & VIF_MASK)
        flags |= IF_MASK;
    flags |= IOPL_MASK;
    return flags | (ts->v86flags & ts->v86mask);
}

#define ADD16(reg, val) reg = (reg & ~0xffff) | ((reg + (val)) & 0xffff)

/* handle VM86 interrupt (NOTE: the CPU core currently does not
   support TSS interrupt revectoring, so this code is always executed) */
static void do_int(CPUX86State *env, int intno)
{
    TaskState *ts = env->opaque;
    uint32_t *int_ptr, segoffs;
    uint8_t *ssp;
    unsigned int sp;

    if (env->segs[R_CS].selector == TARGET_BIOSSEG)
        goto cannot_handle;
    if (is_revectored(intno, &ts->vm86plus.int_revectored))
        goto cannot_handle;
    if (intno == 0x21 && is_revectored((env->regs[R_EAX] >> 8) & 0xff, 
                                       &ts->vm86plus.int21_revectored))
        goto cannot_handle;
    int_ptr = (uint32_t *)(intno << 2);
    segoffs = tswap32(*int_ptr);
    if ((segoffs >> 16) == TARGET_BIOSSEG)
        goto cannot_handle;
#if defined(DEBUG_VM86)
    fprintf(logfile, "VM86: emulating int 0x%x. CS:IP=%04x:%04x\n", 
            intno, segoffs >> 16, segoffs & 0xffff);
#endif
    /* save old state */
    ssp = (uint8_t *)(env->segs[R_SS].selector << 4);
    sp = env->regs[R_ESP] & 0xffff;
    vm_putw(ssp, sp - 2, get_vflags(env));
    vm_putw(ssp, sp - 4, env->segs[R_CS].selector);
    vm_putw(ssp, sp - 6, env->eip);
    ADD16(env->regs[R_ESP], -6);
    /* goto interrupt handler */
    env->eip = segoffs & 0xffff;
    cpu_x86_load_seg(env, R_CS, segoffs >> 16);
    clear_TF(env);
    clear_IF(env);
    clear_AC(env);
    return;
 cannot_handle:
#if defined(DEBUG_VM86)
    fprintf(logfile, "VM86: return to 32 bits int 0x%x\n", intno);
#endif
    return_to_32bit(env, TARGET_VM86_INTx | (intno << 8));
}

void handle_vm86_trap(CPUX86State *env, int trapno)
{
    if (trapno == 1 || trapno == 3) {
        return_to_32bit(env, TARGET_VM86_TRAP + (trapno << 8));
    } else {
        do_int(env, trapno);