Archipelago » qemu

/*

 *  i386 emulator main execution loop

 *

 *  Copyright (c) 2003-2005 Fabrice Bellard

 *

 * This library is free software; you can redistribute it and/or

 * modify it under the terms of the GNU Lesser General Public

 * License as published by the Free Software Foundation; either

 * version 2 of the License, or (at your option) any later version.

 *

 * This library 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

 * Lesser General Public License for more details.

 *

 * You should have received a copy of the GNU Lesser General Public

 * License along with this library; if not, see <http://www.gnu.org/licenses/>.

 */

#include "config.h"

#include "exec.h"

#include "disas.h"

#include "tcg.h"

#include "kvm.h"

#if !defined(CONFIG_SOFTMMU)

#undef EAX

#undef ECX

#undef EDX

#undef EBX

#undef ESP

#undef EBP

#undef ESI

#undef EDI

#undef EIP

#include <signal.h>

#ifdef __linux__

#include <sys/ucontext.h>

#endif

#endif

#if defined(__sparc__) && !defined(HOST_SOLARIS)

// Work around ugly bugs in glibc that mangle global register contents

#undef env

#define env cpu_single_env

#endif

int tb_invalidated_flag;

//#define DEBUG_EXEC

//#define DEBUG_SIGNAL

int qemu_cpu_has_work(CPUState *env)

{

    return cpu_has_work(env);

}

void cpu_loop_exit(void)

{

    /* NOTE: the register at this point must be saved by hand because

       longjmp restore them */

    regs_to_env();

    longjmp(env->jmp_env, 1);

}

/* exit the current TB from a signal handler. The host registers are

   restored in a state compatible with the CPU emulator

 */

void cpu_resume_from_signal(CPUState *env1, void *puc)

{

#if !defined(CONFIG_SOFTMMU)

#ifdef __linux__

    struct ucontext *uc = puc;

#elif defined(__OpenBSD__)

    struct sigcontext *uc = puc;

#endif

#endif

    env = env1;

    /* XXX: restore cpu registers saved in host registers */

#if !defined(CONFIG_SOFTMMU)

    if (puc) {

        /* XXX: use siglongjmp ? */

#ifdef __linux__

        sigprocmask(SIG_SETMASK, &uc->uc_sigmask, NULL);

#elif defined(__OpenBSD__)

        sigprocmask(SIG_SETMASK, &uc->sc_mask, NULL);

#endif

    }

#endif

    env->exception_index = -1;

    longjmp(env->jmp_env, 1);

}

/* Execute the code without caching the generated code. An interpreter

   could be used if available. */

static void cpu_exec_nocache(int max_cycles, TranslationBlock *orig_tb)

{

    unsigned long next_tb;

    TranslationBlock *tb;

    /* Should never happen.

       We only end up here when an existing TB is too long.  */

    if (max_cycles > CF_COUNT_MASK)

        max_cycles = CF_COUNT_MASK;

    tb = tb_gen_code(env, orig_tb->pc, orig_tb->cs_base, orig_tb->flags,

                     max_cycles);

    env->current_tb = tb;

    /* execute the generated code */

    next_tb = tcg_qemu_tb_exec(tb->tc_ptr);

    if ((next_tb & 3) == 2) {

        /* Restore PC.  This may happen if async event occurs before

           the TB starts executing.  */

        cpu_pc_from_tb(env, tb);

    }

    tb_phys_invalidate(tb, -1);

    tb_free(tb);

}

static TranslationBlock *tb_find_slow(target_ulong pc,

                                      target_ulong cs_base,

                                      uint64_t flags)

{

    TranslationBlock *tb, **ptb1;

    unsigned int h;

    target_ulong phys_pc, phys_page1, phys_page2, virt_page2;

    tb_invalidated_flag = 0;

    regs_to_env(); /* XXX: do it just before cpu_gen_code() */

    /* find translated block using physical mappings */

    phys_pc = get_phys_addr_code(env, pc);

    phys_page1 = phys_pc & TARGET_PAGE_MASK;

    phys_page2 = -1;

    h = tb_phys_hash_func(phys_pc);

    ptb1 = &tb_phys_hash[h];

    for(;;) {

        tb = *ptb1;

        if (!tb)

            goto not_found;

        if (tb->pc == pc &&

            tb->page_addr[0] == phys_page1 &&

            tb->cs_base == cs_base &&

            tb->flags == flags) {

            /* check next page if needed */

            if (tb->page_addr[1] != -1) {

                virt_page2 = (pc & TARGET_PAGE_MASK) +

                    TARGET_PAGE_SIZE;

                phys_page2 = get_phys_addr_code(env, virt_page2);

                if (tb->page_addr[1] == phys_page2)

                    goto found;

            } else {

                goto found;

            }

        }

        ptb1 = &tb->phys_hash_next;

    }

 not_found:

   /* if no translated code available, then translate it now */

    tb = tb_gen_code(env, pc, cs_base, flags, 0);

 found:

    /* we add the TB in the virtual pc hash table */

    env->tb_jmp_cache[tb_jmp_cache_hash_func(pc)] = tb;

    return tb;

}

static inline TranslationBlock *tb_find_fast(void)

{

    TranslationBlock *tb;

    target_ulong cs_base, pc;

    int flags;

    /* we record a subset of the CPU state. It will

       always be the same before a given translated block

       is executed. */

    cpu_get_tb_cpu_state(env, &pc, &cs_base, &flags);

    tb = env->tb_jmp_cache[tb_jmp_cache_hash_func(pc)];

    if (unlikely(!tb || tb->pc != pc || tb->cs_base != cs_base ||

                 tb->flags != flags)) {

        tb = tb_find_slow(pc, cs_base, flags);

    }

    return tb;

}

static CPUDebugExcpHandler *debug_excp_handler;

CPUDebugExcpHandler *cpu_set_debug_excp_handler(CPUDebugExcpHandler *handler)

{

    CPUDebugExcpHandler *old_handler = debug_excp_handler;

    debug_excp_handler = handler;

    return old_handler;

}

static void cpu_handle_debug_exception(CPUState *env)

{

    CPUWatchpoint *wp;

    if (!env->watchpoint_hit)

        TAILQ_FOREACH(wp, &env->watchpoints, entry)

            wp->flags &= ~BP_WATCHPOINT_HIT;

    if (debug_excp_handler)

        debug_excp_handler(env);

}

/* main execution loop */

int cpu_exec(CPUState *env1)

{

#define DECLARE_HOST_REGS 1

#include "hostregs_helper.h"

    int ret, interrupt_request;

    TranslationBlock *tb;

    uint8_t *tc_ptr;

    unsigned long next_tb;

    if (cpu_halted(env1) == EXCP_HALTED)

        return EXCP_HALTED;

    cpu_single_env = env1;

    /* first we save global registers */

#define SAVE_HOST_REGS 1

#include "hostregs_helper.h"

    env = env1;

    env_to_regs();

#if defined(TARGET_I386)

    /* put eflags in CPU temporary format */

    CC_SRC = env->eflags & (CC_O | CC_S | CC_Z | CC_A | CC_P | CC_C);

    DF = 1 - (2 * ((env->eflags >> 10) & 1));

    CC_OP = CC_OP_EFLAGS;

    env->eflags &= ~(DF_MASK | CC_O | CC_S | CC_Z | CC_A | CC_P | CC_C);

#elif defined(TARGET_SPARC)

#elif defined(TARGET_M68K)

    env->cc_op = CC_OP_FLAGS;

    env->cc_dest = env->sr & 0xf;

    env->cc_x = (env->sr >> 4) & 1;

#elif defined(TARGET_ALPHA)

#elif defined(TARGET_ARM)

#elif defined(TARGET_PPC)

#elif defined(TARGET_MICROBLAZE)

#elif defined(TARGET_MIPS)

#elif defined(TARGET_SH4)

#elif defined(TARGET_CRIS)

    /* XXXXX */

#else

#error unsupported target CPU

#endif

    env->exception_index = -1;

    /* prepare setjmp context for exception handling */

    for(;;) {

        if (setjmp(env->jmp_env) == 0) {

#if defined(__sparc__) && !defined(HOST_SOLARIS)

#undef env

                    env = cpu_single_env;

#define env cpu_single_env

#endif

            env->current_tb = NULL;

            /* if an exception is pending, we execute it here */

            if (env->exception_index >= 0) {

                if (env->exception_index >= EXCP_INTERRUPT) {

                    /* exit request from the cpu execution loop */

                    ret = env->exception_index;

                    if (ret == EXCP_DEBUG)

                        cpu_handle_debug_exception(env);

                    break;

                } else {

#if defined(CONFIG_USER_ONLY)

                    /* if user mode only, we simulate a fake exception

                       which will be handled outside the cpu execution

                       loop */

#if defined(TARGET_I386)

                    do_interrupt_user(env->exception_index,

                                      env->exception_is_int,

                                      env->error_code,

                                      env->exception_next_eip);

                    /* successfully delivered */

                    env->old_exception = -1;

#endif

                    ret = env->exception_index;

                    break;

#else

#if defined(TARGET_I386)

                    /* simulate a real cpu exception. On i386, it can

                       trigger new exceptions, but we do not handle

                       double or triple faults yet. */

                    do_interrupt(env->exception_index,

                                 env->exception_is_int,

                                 env->error_code,

                                 env->exception_next_eip, 0);

                    /* successfully delivered */

                    env->old_exception = -1;

#elif defined(TARGET_PPC)

                    do_interrupt(env);

#elif defined(TARGET_MICROBLAZE)

                    do_interrupt(env);

#elif defined(TARGET_MIPS)

                    do_interrupt(env);

#elif defined(TARGET_SPARC)

                    do_interrupt(env);

#elif defined(TARGET_ARM)

                    do_interrupt(env);

#elif defined(TARGET_SH4)

                    do_interrupt(env);

#elif defined(TARGET_ALPHA)

                    do_interrupt(env);

#elif defined(TARGET_CRIS)

                    do_interrupt(env);

#elif defined(TARGET_M68K)

                    do_interrupt(0);

#endif

#endif

                }

                env->exception_index = -1;

            }

#ifdef CONFIG_KQEMU

            if (kqemu_is_ok(env) && env->interrupt_request == 0 && env->exit_request == 0) {

                int ret;

                env->eflags = env->eflags | helper_cc_compute_all(CC_OP) | (DF & DF_MASK);

                ret = kqemu_cpu_exec(env);

                /* put eflags in CPU temporary format */

                CC_SRC = env->eflags & (CC_O | CC_S | CC_Z | CC_A | CC_P | CC_C);

                DF = 1 - (2 * ((env->eflags >> 10) & 1));

                CC_OP = CC_OP_EFLAGS;

                env->eflags &= ~(DF_MASK | CC_O | CC_S | CC_Z | CC_A | CC_P | CC_C);

                if (ret == 1) {

                    /* exception */

                    longjmp(env->jmp_env, 1);

                } else if (ret == 2) {

                    /* softmmu execution needed */

                } else {

                    if (env->interrupt_request != 0 || env->exit_request != 0) {

                        /* hardware interrupt will be executed just after */

                    } else {

                        /* otherwise, we restart */

                        longjmp(env->jmp_env, 1);

                    }

                }

            }

#endif

            if (kvm_enabled()) {

                kvm_cpu_exec(env);

                longjmp(env->jmp_env, 1);

            }

            next_tb = 0; /* force lookup of first TB */

            for(;;) {

                interrupt_request = env->interrupt_request;

                if (unlikely(interrupt_request)) {

                    if (unlikely(env->singlestep_enabled & SSTEP_NOIRQ)) {

                        /* Mask out external interrupts for this step. */

                        interrupt_request &= ~(CPU_INTERRUPT_HARD |

                                               CPU_INTERRUPT_FIQ |

                                               CPU_INTERRUPT_SMI |

                                               CPU_INTERRUPT_NMI);

                    }

                    if (interrupt_request & CPU_INTERRUPT_DEBUG) {

                        env->interrupt_request &= ~CPU_INTERRUPT_DEBUG;

                        env->exception_index = EXCP_DEBUG;

                        cpu_loop_exit();

                    }

#if defined(TARGET_ARM) || defined(TARGET_SPARC) || defined(TARGET_MIPS) || \

    defined(TARGET_PPC) || defined(TARGET_ALPHA) || defined(TARGET_CRIS) || \

    defined(TARGET_MICROBLAZE)

                    if (interrupt_request & CPU_INTERRUPT_HALT) {

                        env->interrupt_request &= ~CPU_INTERRUPT_HALT;

                        env->halted = 1;

                        env->exception_index = EXCP_HLT;

                        cpu_loop_exit();

                    }

#endif

#if defined(TARGET_I386)

                    if (interrupt_request & CPU_INTERRUPT_INIT) {

                            svm_check_intercept(SVM_EXIT_INIT);

                            do_cpu_init(env);

                            env->exception_index = EXCP_HALTED;

                            cpu_loop_exit();

                    } else if (interrupt_request & CPU_INTERRUPT_SIPI) {

                            do_cpu_sipi(env);

                    } else if (env->hflags2 & HF2_GIF_MASK) {

                        if ((interrupt_request & CPU_INTERRUPT_SMI) &&

                            !(env->hflags & HF_SMM_MASK)) {

                            svm_check_intercept(SVM_EXIT_SMI);

                            env->interrupt_request &= ~CPU_INTERRUPT_SMI;

                            do_smm_enter();

                            next_tb = 0;

                        } else if ((interrupt_request & CPU_INTERRUPT_NMI) &&

                                   !(env->hflags2 & HF2_NMI_MASK)) {

                            env->interrupt_request &= ~CPU_INTERRUPT_NMI;

                            env->hflags2 |= HF2_NMI_MASK;

                            do_interrupt(EXCP02_NMI, 0, 0, 0, 1);

                            next_tb = 0;

                        } else if (interrupt_request & CPU_INTERRUPT_MCE) {

                            env->interrupt_request &= ~CPU_INTERRUPT_MCE;

                            do_interrupt(EXCP12_MCHK, 0, 0, 0, 0);

                            next_tb = 0;

                        } else if ((interrupt_request & CPU_INTERRUPT_HARD) &&

                                   (((env->hflags2 & HF2_VINTR_MASK) && 

                                     (env->hflags2 & HF2_HIF_MASK)) ||

                                    (!(env->hflags2 & HF2_VINTR_MASK) && 

                                     (env->eflags & IF_MASK && 

                                      !(env->hflags & HF_INHIBIT_IRQ_MASK))))) {

                            int intno;

                            svm_check_intercept(SVM_EXIT_INTR);

                            env->interrupt_request &= ~(CPU_INTERRUPT_HARD | CPU_INTERRUPT_VIRQ);

                            intno = cpu_get_pic_interrupt(env);

                            qemu_log_mask(CPU_LOG_TB_IN_ASM, "Servicing hardware INT=0x%02x\n", intno);

#if defined(__sparc__) && !defined(HOST_SOLARIS)

#undef env

                    env = cpu_single_env;

#define env cpu_single_env

#endif

                            do_interrupt(intno, 0, 0, 0, 1);

                            /* ensure that no TB jump will be modified as

                               the program flow was changed */

                            next_tb = 0;

#if !defined(CONFIG_USER_ONLY)

                        } else if ((interrupt_request & CPU_INTERRUPT_VIRQ) &&

                                   (env->eflags & IF_MASK) && 

                                   !(env->hflags & HF_INHIBIT_IRQ_MASK)) {

                            int intno;

                            /* FIXME: this should respect TPR */

                            svm_check_intercept(SVM_EXIT_VINTR);

                            intno = ldl_phys(env->vm_vmcb + offsetof(struct vmcb, control.int_vector));

                            qemu_log_mask(CPU_LOG_TB_IN_ASM, "Servicing virtual hardware INT=0x%02x\n", intno);

                            do_interrupt(intno, 0, 0, 0, 1);

                            env->interrupt_request &= ~CPU_INTERRUPT_VIRQ;

                            next_tb = 0;

#endif

                        }

                    }

#elif defined(TARGET_PPC)

#if 0

                    if ((interrupt_request & CPU_INTERRUPT_RESET)) {

                        cpu_ppc_reset(env);

                    }

#endif

                    if (interrupt_request & CPU_INTERRUPT_HARD) {

                        ppc_hw_interrupt(env);

                        if (env->pending_interrupts == 0)

                            env->interrupt_request &= ~CPU_INTERRUPT_HARD;

                        next_tb = 0;

                    }

#elif defined(TARGET_MICROBLAZE)

                    if ((interrupt_request & CPU_INTERRUPT_HARD)

                        && (env->sregs[SR_MSR] & MSR_IE)

                        && !(env->sregs[SR_MSR] & (MSR_EIP | MSR_BIP))

                        && !(env->iflags & (D_FLAG | IMM_FLAG))) {

                        env->exception_index = EXCP_IRQ;

                        do_interrupt(env);

                        next_tb = 0;

                    }

#elif defined(TARGET_MIPS)

                    if ((interrupt_request & CPU_INTERRUPT_HARD) &&

                        (env->CP0_Status & env->CP0_Cause & CP0Ca_IP_mask) &&

                        (env->CP0_Status & (1 << CP0St_IE)) &&

                        !(env->CP0_Status & (1 << CP0St_EXL)) &&

                        !(env->CP0_Status & (1 << CP0St_ERL)) &&

                        !(env->hflags & MIPS_HFLAG_DM)) {

                        /* Raise it */

                        env->exception_index = EXCP_EXT_INTERRUPT;

                        env->error_code = 0;

                        do_interrupt(env);

                        next_tb = 0;

                    }

#elif defined(TARGET_SPARC)

                    if ((interrupt_request & CPU_INTERRUPT_HARD) &&

                        cpu_interrupts_enabled(env)) {

                        int pil = env->interrupt_index & 15;

                        int type = env->interrupt_index & 0xf0;

                        if (((type == TT_EXTINT) &&

                             (pil == 15 || pil > env->psrpil)) ||

                            type != TT_EXTINT) {

                            env->interrupt_request &= ~CPU_INTERRUPT_HARD;

                            env->exception_index = env->interrupt_index;

                            do_interrupt(env);

                            env->interrupt_index = 0;

#if !defined(CONFIG_USER_ONLY)

                            cpu_check_irqs(env);

#endif

                        next_tb = 0;

                        }

                    } else if (interrupt_request & CPU_INTERRUPT_TIMER) {

                        //do_interrupt(0, 0, 0, 0, 0);

                        env->interrupt_request &= ~CPU_INTERRUPT_TIMER;

                    }

#elif defined(TARGET_ARM)

                    if (interrupt_request & CPU_INTERRUPT_FIQ

                        && !(env->uncached_cpsr & CPSR_F)) {

                        env->exception_index = EXCP_FIQ;

                        do_interrupt(env);

                        next_tb = 0;

                    }

                    /* ARMv7-M interrupt return works by loading a magic value

                       into the PC.  On real hardware the load causes the

                       return to occur.  The qemu implementation performs the

                       jump normally, then does the exception return when the

                       CPU tries to execute code at the magic address.

                       This will cause the magic PC value to be pushed to

                       the stack if an interrupt occured at the wrong time.

                       We avoid this by disabling interrupts when

                       pc contains a magic address.  */

                    if (interrupt_request & CPU_INTERRUPT_HARD

                        && ((IS_M(env) && env->regs[15] < 0xfffffff0)

                            || !(env->uncached_cpsr & CPSR_I))) {

                        env->exception_index = EXCP_IRQ;

                        do_interrupt(env);

                        next_tb = 0;

                    }

#elif defined(TARGET_SH4)

                    if (interrupt_request & CPU_INTERRUPT_HARD) {

                        do_interrupt(env);

                        next_tb = 0;

                    }

#elif defined(TARGET_ALPHA)

                    if (interrupt_request & CPU_INTERRUPT_HARD) {

                        do_interrupt(env);

                        next_tb = 0;

                    }

#elif defined(TARGET_CRIS)

                    if (interrupt_request & CPU_INTERRUPT_HARD

                        && (env->pregs[PR_CCS] & I_FLAG)) {

                        env->exception_index = EXCP_IRQ;

                        do_interrupt(env);

                        next_tb = 0;

                    }

                    if (interrupt_request & CPU_INTERRUPT_NMI

                        && (env->pregs[PR_CCS] & M_FLAG)) {

                        env->exception_index = EXCP_NMI;

                        do_interrupt(env);

                        next_tb = 0;

                    }

#elif defined(TARGET_M68K)

                    if (interrupt_request & CPU_INTERRUPT_HARD

                        && ((env->sr & SR_I) >> SR_I_SHIFT)

                            < env->pending_level) {

                        /* Real hardware gets the interrupt vector via an

                           IACK cycle at this point.  Current emulated

                           hardware doesn't rely on this, so we

                           provide/save the vector when the interrupt is

                           first signalled.  */

                        env->exception_index = env->pending_vector;

                        do_interrupt(1);

                        next_tb = 0;

                    }

#endif

                   /* Don't use the cached interupt_request value,

                      do_interrupt may have updated the EXITTB flag. */

                    if (env->interrupt_request & CPU_INTERRUPT_EXITTB) {

                        env->interrupt_request &= ~CPU_INTERRUPT_EXITTB;

                        /* ensure that no TB jump will be modified as

                           the program flow was changed */

                        next_tb = 0;

                    }

                }

                if (unlikely(env->exit_request)) {

                    env->exit_request = 0;

                    env->exception_index = EXCP_INTERRUPT;

                    cpu_loop_exit();

                }

#ifdef DEBUG_EXEC

                if (qemu_loglevel_mask(CPU_LOG_TB_CPU)) {

                    /* restore flags in standard format */

                    regs_to_env();

#if defined(TARGET_I386)

                    env->eflags = env->eflags | helper_cc_compute_all(CC_OP) | (DF & DF_MASK);

                    log_cpu_state(env, X86_DUMP_CCOP);

                    env->eflags &= ~(DF_MASK | CC_O | CC_S | CC_Z | CC_A | CC_P | CC_C);

#elif defined(TARGET_ARM)

                    log_cpu_state(env, 0);

#elif defined(TARGET_SPARC)

                    log_cpu_state(env, 0);

#elif defined(TARGET_PPC)

                    log_cpu_state(env, 0);

#elif defined(TARGET_M68K)

                    cpu_m68k_flush_flags(env, env->cc_op);

                    env->cc_op = CC_OP_FLAGS;

                    env->sr = (env->sr & 0xffe0)

                              | env->cc_dest | (env->cc_x << 4);

                    log_cpu_state(env, 0);

#elif defined(TARGET_MICROBLAZE)

                    log_cpu_state(env, 0);

#elif defined(TARGET_MIPS)

                    log_cpu_state(env, 0);

#elif defined(TARGET_SH4)

                    log_cpu_state(env, 0);

#elif defined(TARGET_ALPHA)

                    log_cpu_state(env, 0);

#elif defined(TARGET_CRIS)

                    log_cpu_state(env, 0);

#else

#error unsupported target CPU

#endif

                }

#endif

                spin_lock(&tb_lock);

                tb = tb_find_fast();

                /* Note: we do it here to avoid a gcc bug on Mac OS X when

                   doing it in tb_find_slow */

                if (tb_invalidated_flag) {

                    /* as some TB could have been invalidated because

                       of memory exceptions while generating the code, we

                       must recompute the hash index here */

                    next_tb = 0;

                    tb_invalidated_flag = 0;

                }

#ifdef DEBUG_EXEC

                qemu_log_mask(CPU_LOG_EXEC, "Trace 0x%08lx [" TARGET_FMT_lx "] %s\n",

                             (long)tb->tc_ptr, tb->pc,

                             lookup_symbol(tb->pc));

#endif

                /* see if we can patch the calling TB. When the TB

                   spans two pages, we cannot safely do a direct

                   jump. */

                {

                    if (next_tb != 0 &&

#ifdef CONFIG_KQEMU

                        (env->kqemu_enabled != 2) &&

#endif

                        tb->page_addr[1] == -1) {

                    tb_add_jump((TranslationBlock *)(next_tb & ~3), next_tb & 3, tb);

                }

                }

                spin_unlock(&tb_lock);

                env->current_tb = tb;

                /* cpu_interrupt might be called while translating the

                   TB, but before it is linked into a potentially

                   infinite loop and becomes env->current_tb. Avoid

                   starting execution if there is a pending interrupt. */

                if (unlikely (env->exit_request))

                    env->current_tb = NULL;

                while (env->current_tb) {

                    tc_ptr = tb->tc_ptr;

                /* execute the generated code */

#if defined(__sparc__) && !defined(HOST_SOLARIS)

#undef env

                    env = cpu_single_env;

#define env cpu_single_env

#endif

                    next_tb = tcg_qemu_tb_exec(tc_ptr);

                    env->current_tb = NULL;

                    if ((next_tb & 3) == 2) {

                        /* Instruction counter expired.  */

                        int insns_left;

                        tb = (TranslationBlock *)(long)(next_tb & ~3);

                        /* Restore PC.  */

                        cpu_pc_from_tb(env, tb);

                        insns_left = env->icount_decr.u32;

                        if (env->icount_extra && insns_left >= 0) {

                            /* Refill decrementer and continue execution.  */

                            env->icount_extra += insns_left;

                            if (env->icount_extra > 0xffff) {

                                insns_left = 0xffff;

                            } else {

                                insns_left = env->icount_extra;

                            }

                            env->icount_extra -= insns_left;

                            env->icount_decr.u16.low = insns_left;

                        } else {

                            if (insns_left > 0) {

                                /* Execute remaining instructions.  */

                                cpu_exec_nocache(insns_left, tb);

                            }

                            env->exception_index = EXCP_INTERRUPT;

                            next_tb = 0;

                            cpu_loop_exit();

                        }

                    }

                }

                /* reset soft MMU for next block (it can currently

                   only be set by a memory fault) */

#if defined(CONFIG_KQEMU)

#define MIN_CYCLE_BEFORE_SWITCH (100 * 1000)

                if (kqemu_is_ok(env) &&

                    (cpu_get_time_fast() - env->last_io_time) >= MIN_CYCLE_BEFORE_SWITCH) {

                    cpu_loop_exit();

                }

#endif

            } /* for(;;) */

        } else {

            env_to_regs();

        }

    } /* for(;;) */

#if defined(TARGET_I386)

    /* restore flags in standard format */

    env->eflags = env->eflags | helper_cc_compute_all(CC_OP) | (DF & DF_MASK);

#elif defined(TARGET_ARM)

    /* XXX: Save/restore host fpu exception state?.  */

#elif defined(TARGET_SPARC)

#elif defined(TARGET_PPC)

#elif defined(TARGET_M68K)

    cpu_m68k_flush_flags(env, env->cc_op);

    env->cc_op = CC_OP_FLAGS;

    env->sr = (env->sr & 0xffe0)

              | env->cc_dest | (env->cc_x << 4);

#elif defined(TARGET_MICROBLAZE)

#elif defined(TARGET_MIPS)

#elif defined(TARGET_SH4)

#elif defined(TARGET_ALPHA)

#elif defined(TARGET_CRIS)

    /* XXXXX */

#else

#error unsupported target CPU

#endif

    /* restore global registers */

#include "hostregs_helper.h"

    /* fail safe : never use cpu_single_env outside cpu_exec() */

    cpu_single_env = NULL;

    return ret;

}

/* must only be called from the generated code as an exception can be

   generated */

void tb_invalidate_page_range(target_ulong start, target_ulong end)

{

    /* XXX: cannot enable it yet because it yields to MMU exception

       where NIP != read address on PowerPC */

#if 0

    target_ulong phys_addr;

    phys_addr = get_phys_addr_code(env, start);

    tb_invalidate_phys_page_range(phys_addr, phys_addr + end - start, 0);

#endif

}

#if defined(TARGET_I386) && defined(CONFIG_USER_ONLY)

void cpu_x86_load_seg(CPUX86State *s, int seg_reg, int selector)

{

    CPUX86State *saved_env;

    saved_env = env;

    env = s;

    if (!(env->cr[0] & CR0_PE_MASK) || (env->eflags & VM_MASK)) {

        selector &= 0xffff;

        cpu_x86_load_seg_cache(env, seg_reg, selector,

                               (selector << 4), 0xffff, 0);

    } else {

        helper_load_seg(seg_reg, selector);

    }

    env = saved_env;

}

void cpu_x86_fsave(CPUX86State *s, target_ulong ptr, int data32)

{

    CPUX86State *saved_env;

    saved_env = env;

    env = s;

    helper_fsave(ptr, data32);

    env = saved_env;

}

void cpu_x86_frstor(CPUX86State *s, target_ulong ptr, int data32)

{

    CPUX86State *saved_env;

    saved_env = env;

    env = s;

    helper_frstor(ptr, data32);

    env = saved_env;

}

#endif /* TARGET_I386 */

#if !defined(CONFIG_SOFTMMU)

#if defined(TARGET_I386)

/* 'pc' is the host PC at which the exception was raised. 'address' is

   the effective address of the memory exception. 'is_write' is 1 if a

   write caused the exception and otherwise 0'. 'old_set' is the

   signal set which should be restored */

static inline int handle_cpu_signal(unsigned long pc, unsigned long address,

                                    int is_write, sigset_t *old_set,

                                    void *puc)

{

    TranslationBlock *tb;

    int ret;

    if (cpu_single_env)

        env = cpu_single_env; /* XXX: find a correct solution for multithread */

#if defined(DEBUG_SIGNAL)

    qemu_printf("qemu: SIGSEGV pc=0x%08lx address=%08lx w=%d oldset=0x%08lx\n",

                pc, address, is_write, *(unsigned long *)old_set);

#endif

    /* XXX: locking issue */

    if (is_write && page_unprotect(h2g(address), pc, puc)) {

        return 1;

    }

    /* see if it is an MMU fault */

    ret = cpu_x86_handle_mmu_fault(env, address, is_write, MMU_USER_IDX, 0);

    if (ret < 0)

        return 0; /* not an MMU fault */

    if (ret == 0)

        return 1; /* the MMU fault was handled without causing real CPU fault */

    /* now we have a real cpu fault */

    tb = tb_find_pc(pc);

    if (tb) {

        /* the PC is inside the translated code. It means that we have

           a virtual CPU fault */

        cpu_restore_state(tb, env, pc, puc);

    }

    if (ret == 1) {

#if 0

        printf("PF exception: EIP=0x%08x CR2=0x%08x error=0x%x\n",

               env->eip, env->cr[2], env->error_code);

#endif

        /* we restore the process signal mask as the sigreturn should

           do it (XXX: use sigsetjmp) */

        sigprocmask(SIG_SETMASK, old_set, NULL);

        raise_exception_err(env->exception_index, env->error_code);

    } else {

        /* activate soft MMU for this block */

        env->hflags |= HF_SOFTMMU_MASK;

        cpu_resume_from_signal(env, puc);

    }

    /* never comes here */

    return 1;

}

#elif defined(TARGET_ARM)

static inline int handle_cpu_signal(unsigned long pc, unsigned long address,

                                    int is_write, sigset_t *old_set,

                                    void *puc)

{

    TranslationBlock *tb;

    int ret;

    if (cpu_single_env)

        env = cpu_single_env; /* XXX: find a correct solution for multithread */

#if defined(DEBUG_SIGNAL)

    printf("qemu: SIGSEGV pc=0x%08lx address=%08lx w=%d oldset=0x%08lx\n",

           pc, address, is_write, *(unsigned long *)old_set);

#endif

    /* XXX: locking issue */

    if (is_write && page_unprotect(h2g(address), pc, puc)) {

        return 1;

    }

    /* see if it is an MMU fault */

    ret = cpu_arm_handle_mmu_fault(env, address, is_write, MMU_USER_IDX, 0);

    if (ret < 0)

        return 0; /* not an MMU fault */

    if (ret == 0)

        return 1; /* the MMU fault was handled without causing real CPU fault */

    /* now we have a real cpu fault */

    tb = tb_find_pc(pc);

    if (tb) {

        /* the PC is inside the translated code. It means that we have

           a virtual CPU fault */

        cpu_restore_state(tb, env, pc, puc);

    }

    /* we restore the process signal mask as the sigreturn should

       do it (XXX: use sigsetjmp) */

    sigprocmask(SIG_SETMASK, old_set, NULL);

    cpu_loop_exit();

    /* never comes here */

    return 1;

}

#elif defined(TARGET_SPARC)

static inline int handle_cpu_signal(unsigned long pc, unsigned long address,

                                    int is_write, sigset_t *old_set,

                                    void *puc)

{

    TranslationBlock *tb;

    int ret;

    if (cpu_single_env)

        env = cpu_single_env; /* XXX: find a correct solution for multithread */

#if defined(DEBUG_SIGNAL)

    printf("qemu: SIGSEGV pc=0x%08lx address=%08lx w=%d oldset=0x%08lx\n",

           pc, address, is_write, *(unsigned long *)old_set);

#endif

    /* XXX: locking issue */

    if (is_write && page_unprotect(h2g(address), pc, puc)) {

        return 1;

    }

    /* see if it is an MMU fault */

    ret = cpu_sparc_handle_mmu_fault(env, address, is_write, MMU_USER_IDX, 0);

    if (ret < 0)

        return 0; /* not an MMU fault */

    if (ret == 0)

        return 1; /* the MMU fault was handled without causing real CPU fault */