cpu-exec.c

/*
 *  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/disas.h"
#include "tcg.h"
#include "sysemu/kvm.h"
#include "exec/hax.h"
#include "qemu/atomic.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(CONFIG_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 CONFIG_DEBUG_EXEC
//#define DEBUG_SIGNAL

int qemu_cpu_has_work(CPUOldState *env)
{
    return cpu_has_work(env);
}

void cpu_loop_exit(CPUArchState* env1)
{
    env1->current_tb = NULL;
    longjmp(env1->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(CPUArchState *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__
#ifdef __ia64
        sigprocmask(SIG_SETMASK, (sigset_t *)&uc->uc_sigmask, NULL);
#else
        sigprocmask(SIG_SETMASK, &uc->uc_sigmask, NULL);
#endif
#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);
    env->current_tb = NULL;

    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;

    /* find translated block using physical mappings */
    phys_pc = get_page_addr_code(env, pc);
    phys_page1 = phys_pc & TARGET_PAGE_MASK;
    phys_page2 = -1;
    h = tb_phys_hash_func(phys_pc);
    ptb1 = &tcg_ctx.tb_ctx.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_page_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:
    /* Move the last found TB to the head of the list */
    if (likely(*ptb1)) {
        *ptb1 = tb->phys_hash_next;
        tb->phys_hash_next = tcg_ctx.tb_ctx.tb_phys_hash[h];
        tcg_ctx.tb_ctx.tb_phys_hash[h] = tb;
    }
    /* 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;

void cpu_set_debug_excp_handler(CPUDebugExcpHandler *handler)
{
    debug_excp_handler = handler;
}

static void cpu_handle_debug_exception(CPUOldState *env)
{
    CPUWatchpoint *wp;

    if (!env->watchpoint_hit) {
        QTAILQ_FOREACH(wp, &env->watchpoints, entry) {
            wp->flags &= ~BP_WATCHPOINT_HIT;
        }
    }
    if (debug_excp_handler) {
        debug_excp_handler(env);
    }
}

/* main execution loop */

volatile sig_atomic_t exit_request;

/*
 * Qemu emulation can happen because of MMIO or emulation mode,
 * i.e. non-PG mode.  For MMIO cases, the pending interrupt should not
 * be emulated in qemu because MMIO is emulated for only one
 * instruction now and then back to the HAX kernel module.
 */
int need_handle_intr_request(CPUOldState *env)
{
#ifdef CONFIG_HAX
    if (!hax_enabled() || hax_vcpu_emulation_mode(env))
        return env->interrupt_request;
    return 0;
#else
    return env->interrupt_request;
#endif
}

int cpu_exec(CPUOldState *env1)
{
    volatile host_reg_t saved_env_reg;
    int ret, interrupt_request;
    TranslationBlock *tb;
    uint8_t *tc_ptr;
    unsigned long next_tb;

    if (env1->halted) {
        if (!cpu_has_work(env1)) {
        return EXCP_HALTED;
        }

        env1->halted = 0;
    }

    cpu_single_env = env1;

    /* the access to env below is actually saving the global register's
       value, so that files not including target-xyz/exec.h are free to
       use it.  */
    QEMU_BUILD_BUG_ON (sizeof (saved_env_reg) != sizeof (env));
    saved_env_reg = (host_reg_t) env;
    barrier();
    env = env1;

    if (unlikely(exit_request)) {
        env->exit_request = 1;
    }

#if defined(TARGET_I386)
    if (!kvm_enabled()) {
        /* 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_UNICORE32)
#elif defined(TARGET_PPC)
#elif defined(TARGET_LM32)
#elif defined(TARGET_MICROBLAZE)
#elif defined(TARGET_MIPS)
#elif defined(TARGET_SH4)
#elif defined(TARGET_CRIS)
#elif defined(TARGET_S390X)
    /* 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(CONFIG_SOLARIS)
#undef env
                    env = cpu_single_env;
#define env cpu_single_env
#endif
            /* 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_LM32)
                    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_UNICORE32)
                    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);
#elif defined(TARGET_S390X)
                    do_interrupt(env);
#endif
                    env->exception_index = -1;
#endif
                }
            }

#ifdef CONFIG_HAX
            if (hax_enabled() && !hax_vcpu_exec(env))
                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(need_handle_intr_request(env))) {
                    if (unlikely(env->singlestep_enabled & SSTEP_NOIRQ)) {
                        /* Mask out external interrupts for this step. */
                        interrupt_request &= ~CPU_INTERRUPT_SSTEP_MASK;
                    }
                    if (interrupt_request & CPU_INTERRUPT_DEBUG) {
                        env->interrupt_request &= ~CPU_INTERRUPT_DEBUG;
                        env->exception_index = EXCP_DEBUG;
                        cpu_loop_exit(env);
                    }
#if defined(TARGET_ARM) || defined(TARGET_SPARC) || defined(TARGET_MIPS) || \
    defined(TARGET_PPC) || defined(TARGET_ALPHA) || defined(TARGET_CRIS) || \
    defined(TARGET_MICROBLAZE) || defined(TARGET_LM32) || defined(TARGET_UNICORE32)
                    if (interrupt_request & CPU_INTERRUPT_HALT) {
                        env->interrupt_request &= ~CPU_INTERRUPT_HALT;
                        env->halted = 1;
                        env->exception_index = EXCP_HLT;
                        cpu_loop_exit(env);
                    }
#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(env);
                    } 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(CONFIG_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_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_LM32)
                    if ((interrupt_request & CPU_INTERRUPT_HARD)
                        && (env->ie & IE_IE)) {
                        env->exception_index = EXCP_IRQ;
                        do_interrupt(env);
                        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) &&
                        cpu_mips_hw_interrupts_pending(env)) {
                        /* 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) {
                        if (cpu_interrupts_enabled(env) &&
                            env->interrupt_index > 0) {
                            int pil = env->interrupt_index & 0xf;
                            int type = env->interrupt_index & 0xf0;

                            if (((type == TT_EXTINT) &&
                                  cpu_pil_allowed(env, pil)) ||
                                  type != TT_EXTINT) {
                                env->exception_index = env->interrupt_index;
                                do_interrupt(env);
                                next_tb = 0;
                            }
                        }
		    }
#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 occurred 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_UNICORE32)
                    if (interrupt_request & CPU_INTERRUPT_HARD
                        && !(env->uncached_asr & ASR_I)) {
                        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->locked_irq) {
                        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;
                    }
#elif defined(TARGET_S390X) && !defined(CONFIG_USER_ONLY)
                    if ((interrupt_request & CPU_INTERRUPT_HARD) &&
                        (env->psw.mask & PSW_MASK_EXT)) {
                        do_interrupt(env);
                        next_tb = 0;
                    }
#endif
                   /* Don't use the cached interrupt_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(env);
                }
#if defined(DEBUG_DISAS) || defined(CONFIG_DEBUG_EXEC)
                if (qemu_loglevel_mask(CPU_LOG_TB_CPU)) {
                    /* restore flags in standard format */
#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_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);
#else
                    log_cpu_state(env, 0);
#endif
                }
#endif /* DEBUG_DISAS || CONFIG_DEBUG_EXEC */
                spin_lock(&tcg_ctx.tb_ctx.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 CONFIG_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 && tb->page_addr[1] == -1) {
                    tb_add_jump((TranslationBlock *)(next_tb & ~3), next_tb & 3, tb);
                }
                spin_unlock(&tcg_ctx.tb_ctx.tb_lock);

                /* 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. */
                env->current_tb = tb;
                barrier();
                if (likely(!env->exit_request)) {
                    tc_ptr = tb->tc_ptr;
                /* execute the generated code */
#if defined(__sparc__) && !defined(CONFIG_SOLARIS)
#undef env
                    env = cpu_single_env;
#define env cpu_single_env
#endif
                    next_tb = tcg_qemu_tb_exec(tc_ptr);
                    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(env);
                        }
                    }
                }
                env->current_tb = NULL;
#ifdef CONFIG_HAX
                if (hax_enabled() && hax_stop_emulation(env))
                    cpu_loop_exit(env);
#endif
                /* reset soft MMU for next block (it can currently
                   only be set by a memory fault) */
            } /* for(;;) */
        }
    } /* 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_UNICORE32)
#elif defined(TARGET_SPARC)
#elif defined(TARGET_PPC)
#elif defined(TARGET_LM32)
#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)
#elif defined(TARGET_S390X)
    /* XXXXX */
#else
#error unsupported target CPU
#endif

    /* restore global registers */
    barrier();
    env = (void *) saved_env_reg;

    /* fail safe : never use cpu_single_env outside cpu_exec() */
    cpu_single_env = NULL;
    return ret;
}

#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)
#define EXCEPTION_ACTION raise_exception_err(env->exception_index, env->error_code)
#else
#define EXCEPTION_ACTION cpu_loop_exit(env)
#endif

/* '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_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(env, pc);
    }

    /* we restore the process signal mask as the sigreturn should
       do it (XXX: use sigsetjmp) */
    sigprocmask(SIG_SETMASK, old_set, NULL);
    EXCEPTION_ACTION;

    /* never comes here */
    return 1;
}

#if defined(__i386__)

#if defined(__APPLE__)
# include <sys/ucontext.h>

# define EIP_sig(context)  (*((unsigned long*)&(context)->uc_mcontext->ss.eip))
# define TRAP_sig(context)    ((context)->uc_mcontext->es.trapno)
# define ERROR_sig(context)   ((context)->uc_mcontext->es.err)
# define MASK_sig(context)    ((context)->uc_sigmask)
#elif defined (__NetBSD__)
# include <ucontext.h>

# define EIP_sig(context)     ((context)->uc_mcontext.__gregs[_REG_EIP])
# define TRAP_sig(context)    ((context)->uc_mcontext.__gregs[_REG_TRAPNO])
# define ERROR_sig(context)   ((context)->uc_mcontext.__gregs[_REG_ERR])
# define MASK_sig(context)    ((context)->uc_sigmask)
#elif defined (__FreeBSD__) || defined(__DragonFly__)
# include <ucontext.h>

# define EIP_sig(context)  (*((unsigned long*)&(context)->uc_mcontext.mc_eip))
# define TRAP_sig(context)    ((context)->uc_mcontext.mc_trapno)
# define ERROR_sig(context)   ((context)->uc_mcontext.mc_err)
# define MASK_sig(context)    ((context)->uc_sigmask)
#elif defined(__OpenBSD__)
# define EIP_sig(context)     ((context)->sc_eip)
# define TRAP_sig(context)    ((context)->sc_trapno)
# define ERROR_sig(context)   ((context)->sc_err)
# define MASK_sig(context)    ((context)->sc_mask)
#else
# define EIP_sig(context)     ((context)->uc_mcontext.gregs[REG_EIP])
# define TRAP_sig(context)    ((context)->uc_mcontext.gregs[REG_TRAPNO])
# define ERROR_sig(context)   ((context)->uc_mcontext.gregs[REG_ERR])
# define MASK_sig(context)    ((context)->uc_sigmask)
#endif

int cpu_signal_handler(int host_signum, void *pinfo,
                       void *puc)
{
    siginfo_t *info = pinfo;
#if defined(__NetBSD__) || defined (__FreeBSD__) || defined(__DragonFly__)
    ucontext_t *uc = puc;
#elif defined(__OpenBSD__)
    struct sigcontext *uc = puc;
#else
    struct ucontext *uc = puc;
#endif
    unsigned long pc;
    int trapno;

#ifndef REG_EIP
/* for glibc 2.1 */
#define REG_EIP    EIP
#define REG_ERR    ERR
#define REG_TRAPNO TRAPNO
#endif
    pc = EIP_sig(uc);
    trapno = TRAP_sig(uc);
    return handle_cpu_signal(pc, (unsigned long)info->si_addr,
                             trapno == 0xe ?
                             (ERROR_sig(uc) >> 1) & 1 : 0,
                             &MASK_sig(uc), puc);
}

#elif defined(__x86_64__)

#ifdef __NetBSD__
#define PC_sig(context)       _UC_MACHINE_PC(context)
#define TRAP_sig(context)     ((context)->uc_mcontext.__gregs[_REG_TRAPNO])
#define ERROR_sig(context)    ((context)->uc_mcontext.__gregs[_REG_ERR])
#define MASK_sig(context)     ((context)->uc_sigmask)
#elif defined(__OpenBSD__)
#define PC_sig(context)       ((context)->sc_rip)
#define TRAP_sig(context)     ((context)->sc_trapno)
#define ERROR_sig(context)    ((context)->sc_err)
#define MASK_sig(context)     ((context)->sc_mask)
#elif defined (__FreeBSD__) || defined(__DragonFly__)
#include <ucontext.h>

#define PC_sig(context)  (*((unsigned long*)&(context)->uc_mcontext.mc_rip))
#define TRAP_sig(context)     ((context)->uc_mcontext.mc_trapno)
#define ERROR_sig(context)    ((context)->uc_mcontext.mc_err)
#define MASK_sig(context)     ((context)->uc_sigmask)
#else
#define PC_sig(context)       ((context)->uc_mcontext.gregs[REG_RIP])
#define TRAP_sig(context)     ((context)->uc_mcontext.gregs[REG_TRAPNO])
#define ERROR_sig(context)    ((context)->uc_mcontext.gregs[REG_ERR])
#define MASK_sig(context)     ((context)->uc_sigmask)
#endif

int cpu_signal_handler(int host_signum, void *pinfo,
                       void *puc)
{
    siginfo_t *info = pinfo;
    unsigned long pc;
#if defined(__NetBSD__) || defined (__FreeBSD__) || defined(__DragonFly__)
    ucontext_t *uc = puc;
#elif defined(__OpenBSD__)
    struct sigcontext *uc = puc;
#else
    struct ucontext *uc = puc;
#endif

    pc = PC_sig(uc);
    return handle_cpu_signal(pc, (unsigned long)info->si_addr,
                             TRAP_sig(uc) == 0xe ?
                             (ERROR_sig(uc) >> 1) & 1 : 0,
                             &MASK_sig(uc), puc);
}

#elif defined(_ARCH_PPC)

/***********************************************************************
 * signal context platform-specific definitions
 * From Wine
 */
#ifdef linux
/* All Registers access - only for local access */
# define REG_sig(reg_name, context)		((context)->uc_mcontext.regs->reg_name)
/* Gpr Registers access  */
# define GPR_sig(reg_num, context)		REG_sig(gpr[reg_num], context)
# define IAR_sig(context)			REG_sig(nip, context)	/* Program counter */
# define MSR_sig(context)			REG_sig(msr, context)   /* Machine State Register (Supervisor) */
# define CTR_sig(context)			REG_sig(ctr, context)   /* Count register */
# define XER_sig(context)			REG_sig(xer, context) /* User's integer exception register */
# define LR_sig(context)			REG_sig(link, context) /* Link register */
# define CR_sig(context)			REG_sig(ccr, context) /* Condition register */
/* Float Registers access  */
# define FLOAT_sig(reg_num, context)		(((double*)((char*)((context)->uc_mcontext.regs+48*4)))[reg_num])
# define FPSCR_sig(context)			(*(int*)((char*)((context)->uc_mcontext.regs+(48+32*2)*4)))
/* Exception Registers access */
# define DAR_sig(context)			REG_sig(dar, context)
# define DSISR_sig(context)			REG_sig(dsisr, context)
# define TRAP_sig(context)			REG_sig(trap, context)
#endif /* linux */

#if defined(__FreeBSD__) || defined(__FreeBSD_kernel__)
#include <ucontext.h>
# define IAR_sig(context)		((context)->uc_mcontext.mc_srr0)
# define MSR_sig(context)		((context)->uc_mcontext.mc_srr1)
# define CTR_sig(context)		((context)->uc_mcontext.mc_ctr)
# define XER_sig(context)		((context)->uc_mcontext.mc_xer)
# define LR_sig(context)		((context)->uc_mcontext.mc_lr)
# define CR_sig(context)		((context)->uc_mcontext.mc_cr)
/* Exception Registers access */
# define DAR_sig(context)		((context)->uc_mcontext.mc_dar)
# define DSISR_sig(context)		((context)->uc_mcontext.mc_dsisr)
# define TRAP_sig(context)		((context)->uc_mcontext.mc_exc)
#endif /* __FreeBSD__|| __FreeBSD_kernel__ */

#ifdef __APPLE__
# include <sys/ucontext.h>
typedef struct ucontext SIGCONTEXT;
/* All Registers access - only for local access */
# define REG_sig(reg_name, context)		((context)->uc_mcontext->ss.reg_name)
# define FLOATREG_sig(reg_name, context)	((context)->uc_mcontext->fs.reg_name)
# define EXCEPREG_sig(reg_name, context)	((context)->uc_mcontext->es.reg_name)
# define VECREG_sig(reg_name, context)		((context)->uc_mcontext->vs.reg_name)
/* Gpr Registers access */
# define GPR_sig(reg_num, context)		REG_sig(r##reg_num, context)
# define IAR_sig(context)			REG_sig(srr0, context)	/* Program counter */
# define MSR_sig(context)			REG_sig(srr1, context)  /* Machine State Register (Supervisor) */
# define CTR_sig(context)			REG_sig(ctr, context)
# define XER_sig(context)			REG_sig(xer, context) /* Link register */
# define LR_sig(context)			REG_sig(lr, context)  /* User's integer exception register */
# define CR_sig(context)			REG_sig(cr, context)  /* Condition register */
/* Float Registers access */
# define FLOAT_sig(reg_num, context)		FLOATREG_sig(fpregs[reg_num], context)
# define FPSCR_sig(context)			((double)FLOATREG_sig(fpscr, context))
/* Exception Registers access */
# define DAR_sig(context)			EXCEPREG_sig(dar, context)     /* Fault registers for coredump */
# define DSISR_sig(context)			EXCEPREG_sig(dsisr, context)
# define TRAP_sig(context)			EXCEPREG_sig(exception, context) /* number of powerpc exception taken */
#endif /* __APPLE__ */

int cpu_signal_handler(int host_signum, void *pinfo,
                       void *puc)
{
    siginfo_t *info = pinfo;
#if defined(__FreeBSD__) || defined(__FreeBSD_kernel__)
    ucontext_t *uc = puc;
#else
    struct ucontext *uc = puc;
#endif
    unsigned long pc;
    int is_write;

    pc = IAR_sig(uc);
    is_write = 0;
#if 0
    /* ppc 4xx case */
    if (DSISR_sig(uc) & 0x00800000)
        is_write = 1;
#else
    if (TRAP_sig(uc) != 0x400 && (DSISR_sig(uc) & 0x02000000))
        is_write = 1;
#endif
    return handle_cpu_signal(pc, (unsigned long)info->si_addr,
                             is_write, &uc->uc_sigmask, puc);
}

#elif defined(__alpha__)

int cpu_signal_handler(int host_signum, void *pinfo,
                           void *puc)
{
    siginfo_t *info = pinfo;
    struct ucontext *uc = puc;
    uint32_t *pc = uc->uc_mcontext.sc_pc;
    uint32_t insn = *pc;
    int is_write = 0;

    /* XXX: need kernel patch to get write flag faster */
    switch (insn >> 26) {
    case 0x0d: // stw
    case 0x0e: // stb
    case 0x0f: // stq_u
    case 0x24: // stf
    case 0x25: // stg
    case 0x26: // sts
    case 0x27: // stt
    case 0x2c: // stl
    case 0x2d: // stq
    case 0x2e: // stl_c
    case 0x2f: // stq_c
	is_write = 1;
    }

    return handle_cpu_signal(pc, (unsigned long)info->si_addr,
                             is_write, &uc->uc_sigmask, puc);
}
#elif defined(__sparc__)

int cpu_signal_handler(int host_signum, void *pinfo,
                       void *puc)
{
    siginfo_t *info = pinfo;
    int is_write;
    uint32_t insn;
#if !defined(__arch64__) || defined(CONFIG_SOLARIS)
    uint32_t *regs = (uint32_t *)(info + 1);
    void *sigmask = (regs + 20);
    /* XXX: is there a standard glibc define ? */
    unsigned long pc = regs[1];
#else
#ifdef __linux__
    struct sigcontext *sc = puc;
    unsigned long pc = sc->sigc_regs.tpc;
    void *sigmask = (void *)sc->sigc_mask;
#elif defined(__OpenBSD__)
    struct sigcontext *uc = puc;
    unsigned long pc = uc->sc_pc;
    void *sigmask = (void *)(long)uc->sc_mask;
#endif
#endif

    /* XXX: need kernel patch to get write flag faster */
    is_write = 0;
    insn = *(uint32_t *)pc;
    if ((insn >> 30) == 3) {
      switch((insn >> 19) & 0x3f) {
      case 0x05: // stb
      case 0x15: // stba
      case 0x06: // sth
      case 0x16: // stha
      case 0x04: // st
      case 0x14: // sta
      case 0x07: // std
      case 0x17: // stda
      case 0x0e: // stx
      case 0x1e: // stxa
      case 0x24: // stf
      case 0x34: // stfa
      case 0x27: // stdf
      case 0x37: // stdfa
      case 0x26: // stqf
      case 0x36: // stqfa
      case 0x25: // stfsr
      case 0x3c: // casa
      case 0x3e: // casxa
	is_write = 1;
	break;
      }
    }
    return handle_cpu_signal(pc, (unsigned long)info->si_addr,
                             is_write, sigmask, NULL);
}

#elif defined(__arm__)

int cpu_signal_handler(int host_signum, void *pinfo,
                       void *puc)
{
    siginfo_t *info = pinfo;
    struct ucontext *uc = puc;
    unsigned long pc;
    int is_write;

#if (__GLIBC__ < 2 || (__GLIBC__ == 2 && __GLIBC_MINOR__ <= 3))
    pc = uc->uc_mcontext.gregs[R15];
#else
    pc = uc->uc_mcontext.arm_pc;
#endif
    /* XXX: compute is_write */
    is_write = 0;
    return handle_cpu_signal(pc, (unsigned long)info->si_addr,
                             is_write,
                             &uc->uc_sigmask, puc);
}

#elif defined(__mc68000)

int cpu_signal_handler(int host_signum, void *pinfo,
                       void *puc)
{
    siginfo_t *info = pinfo;
    struct ucontext *uc = puc;
    unsigned long pc;
    int is_write;

    pc = uc->uc_mcontext.gregs[16];
    /* XXX: compute is_write */
    is_write = 0;
    return handle_cpu_signal(pc, (unsigned long)info->si_addr,
                             is_write,
                             &uc->uc_sigmask, puc);
}

#elif defined(__ia64)

#ifndef __ISR_VALID
  /* This ought to be in <bits/siginfo.h>... */
# define __ISR_VALID	1
#endif

int cpu_signal_handler(int host_signum, void *pinfo, void *puc)
{
    siginfo_t *info = pinfo;
    struct ucontext *uc = puc;
    unsigned long ip;
    int is_write = 0;

    ip = uc->uc_mcontext.sc_ip;
    switch (host_signum) {
      case SIGILL:
      case SIGFPE:
      case SIGSEGV:
      case SIGBUS:
      case SIGTRAP:
	  if (info->si_code && (info->si_segvflags & __ISR_VALID))
	      /* ISR.W (write-access) is bit 33:  */
	      is_write = (info->si_isr >> 33) & 1;
	  break;

      default:
	  break;
    }
    return handle_cpu_signal(ip, (unsigned long)info->si_addr,
                             is_write,
                             (sigset_t *)&uc->uc_sigmask, puc);
}

#elif defined(__s390__)

int cpu_signal_handler(int host_signum, void *pinfo,
                       void *puc)
{
    siginfo_t *info = pinfo;
    struct ucontext *uc = puc;
    unsigned long pc;
    uint16_t *pinsn;
    int is_write = 0;

    pc = uc->uc_mcontext.psw.addr;

    /* ??? On linux, the non-rt signal handler has 4 (!) arguments instead
       of the normal 2 arguments.  The 3rd argument contains the "int_code"
       from the hardware which does in fact contain the is_write value.
       The rt signal handler, as far as I can tell, does not give this value
       at all.  Not that we could get to it from here even if it were.  */
    /* ??? This is not even close to complete, since it ignores all
       of the read-modify-write instructions.  */
    pinsn = (uint16_t *)pc;
    switch (pinsn[0] >> 8) {
    case 0x50: /* ST */
    case 0x42: /* STC */
    case 0x40: /* STH */
        is_write = 1;
        break;
    case 0xc4: /* RIL format insns */
        switch (pinsn[0] & 0xf) {
        case 0xf: /* STRL */
        case 0xb: /* STGRL */
        case 0x7: /* STHRL */
            is_write = 1;
        }
        break;
    case 0xe3: /* RXY format insns */
        switch (pinsn[2] & 0xff) {
        case 0x50: /* STY */
        case 0x24: /* STG */
        case 0x72: /* STCY */
        case 0x70: /* STHY */
        case 0x8e: /* STPQ */
        case 0x3f: /* STRVH */
        case 0x3e: /* STRV */
        case 0x2f: /* STRVG */
            is_write = 1;
        }
        break;
    }
    return handle_cpu_signal(pc, (unsigned long)info->si_addr,
                             is_write, &uc->uc_sigmask, puc);
}

#elif defined(__mips__)

int cpu_signal_handler(int host_signum, void *pinfo,
                       void *puc)
{
    siginfo_t *info = pinfo;
    struct ucontext *uc = puc;
    greg_t pc = uc->uc_mcontext.pc;
    int is_write;

    /* XXX: compute is_write */
    is_write = 0;
    return handle_cpu_signal(pc, (unsigned long)info->si_addr,
                             is_write, &uc->uc_sigmask, puc);
}

#elif defined(__hppa__)

int cpu_signal_handler(int host_signum, void *pinfo,
                       void *puc)
{
    struct siginfo *info = pinfo;
    struct ucontext *uc = puc;
    unsigned long pc = uc->uc_mcontext.sc_iaoq[0];
    uint32_t insn = *(uint32_t *)pc;
    int is_write = 0;

    /* XXX: need kernel patch to get write flag faster.  */
    switch (insn >> 26) {
    case 0x1a: /* STW */
    case 0x19: /* STH */
    case 0x18: /* STB */
    case 0x1b: /* STWM */
        is_write = 1;
        break;

    case 0x09: /* CSTWX, FSTWX, FSTWS */
    case 0x0b: /* CSTDX, FSTDX, FSTDS */
        /* Distinguish from coprocessor load ... */
        is_write = (insn >> 9) & 1;
        break;

    case 0x03:
        switch ((insn >> 6) & 15) {
        case 0xa: /* STWS */
        case 0x9: /* STHS */
        case 0x8: /* STBS */
        case 0xe: /* STWAS */
        case 0xc: /* STBYS */
            is_write = 1;
        }
        break;
    }

    return handle_cpu_signal(pc, (unsigned long)info->si_addr,
                             is_write, &uc->uc_sigmask, puc);
}

#else

#error host CPU specific signal handler needed

#endif

#endif /* !defined(CONFIG_SOFTMMU) */