xref: /qemu/accel/tcg/translate-all.c (revision 92eecfff)

/*
 *  Host code generation
 *
 *  Copyright (c) 2003 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 2.1 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 "qemu/osdep.h"
#include "qemu/units.h"
#include "qemu-common.h"

#define NO_CPU_IO_DEFS
#include "cpu.h"
#include "trace.h"
#include "disas/disas.h"
#include "exec/exec-all.h"
#include "tcg/tcg.h"
#if defined(CONFIG_USER_ONLY)
#include "qemu.h"
#if defined(__FreeBSD__) || defined(__FreeBSD_kernel__)
#include <sys/param.h>
#if __FreeBSD_version >= 700104
#define HAVE_KINFO_GETVMMAP
#define sigqueue sigqueue_freebsd  /* avoid redefinition */
#include <sys/proc.h>
#include <machine/profile.h>
#define _KERNEL
#include <sys/user.h>
#undef _KERNEL
#undef sigqueue
#include <libutil.h>
#endif
#endif
#else
#include "exec/ram_addr.h"
#endif

#include "exec/cputlb.h"
#include "exec/tb-hash.h"
#include "translate-all.h"
#include "qemu/bitmap.h"
#include "qemu/error-report.h"
#include "qemu/qemu-print.h"
#include "qemu/timer.h"
#include "qemu/main-loop.h"
#include "exec/log.h"
#include "sysemu/cpus.h"
#include "sysemu/cpu-timers.h"
#include "sysemu/tcg.h"

/* #define DEBUG_TB_INVALIDATE */
/* #define DEBUG_TB_FLUSH */
/* make various TB consistency checks */
/* #define DEBUG_TB_CHECK */

#ifdef DEBUG_TB_INVALIDATE
#define DEBUG_TB_INVALIDATE_GATE 1
#else
#define DEBUG_TB_INVALIDATE_GATE 0
#endif

#ifdef DEBUG_TB_FLUSH
#define DEBUG_TB_FLUSH_GATE 1
#else
#define DEBUG_TB_FLUSH_GATE 0
#endif

#if !defined(CONFIG_USER_ONLY)
/* TB consistency checks only implemented for usermode emulation.  */
#undef DEBUG_TB_CHECK
#endif

#ifdef DEBUG_TB_CHECK
#define DEBUG_TB_CHECK_GATE 1
#else
#define DEBUG_TB_CHECK_GATE 0
#endif

/* Access to the various translations structures need to be serialised via locks
 * for consistency.
 * In user-mode emulation access to the memory related structures are protected
 * with mmap_lock.
 * In !user-mode we use per-page locks.
 */
#ifdef CONFIG_SOFTMMU
#define assert_memory_lock()
#else
#define assert_memory_lock() tcg_debug_assert(have_mmap_lock())
#endif

#define SMC_BITMAP_USE_THRESHOLD 10

typedef struct PageDesc {
    /* list of TBs intersecting this ram page */
    uintptr_t first_tb;
#ifdef CONFIG_SOFTMMU
    /* in order to optimize self modifying code, we count the number
       of lookups we do to a given page to use a bitmap */
    unsigned long *code_bitmap;
    unsigned int code_write_count;
#else
    unsigned long flags;
#endif
#ifndef CONFIG_USER_ONLY
    QemuSpin lock;
#endif
} PageDesc;

/**
 * struct page_entry - page descriptor entry
 * @pd:     pointer to the &struct PageDesc of the page this entry represents
 * @index:  page index of the page
 * @locked: whether the page is locked
 *
 * This struct helps us keep track of the locked state of a page, without
 * bloating &struct PageDesc.
 *
 * A page lock protects accesses to all fields of &struct PageDesc.
 *
 * See also: &struct page_collection.
 */
struct page_entry {
    PageDesc *pd;
    tb_page_addr_t index;
    bool locked;
};

/**
 * struct page_collection - tracks a set of pages (i.e. &struct page_entry's)
 * @tree:   Binary search tree (BST) of the pages, with key == page index
 * @max:    Pointer to the page in @tree with the highest page index
 *
 * To avoid deadlock we lock pages in ascending order of page index.
 * When operating on a set of pages, we need to keep track of them so that
 * we can lock them in order and also unlock them later. For this we collect
 * pages (i.e. &struct page_entry's) in a binary search @tree. Given that the
 * @tree implementation we use does not provide an O(1) operation to obtain the
 * highest-ranked element, we use @max to keep track of the inserted page
 * with the highest index. This is valuable because if a page is not in
 * the tree and its index is higher than @max's, then we can lock it
 * without breaking the locking order rule.
 *
 * Note on naming: 'struct page_set' would be shorter, but we already have a few
 * page_set_*() helpers, so page_collection is used instead to avoid confusion.
 *
 * See also: page_collection_lock().
 */
struct page_collection {
    GTree *tree;
    struct page_entry *max;
};

/* list iterators for lists of tagged pointers in TranslationBlock */
#define TB_FOR_EACH_TAGGED(head, tb, n, field)                          \
    for (n = (head) & 1, tb = (TranslationBlock *)((head) & ~1);        \
         tb; tb = (TranslationBlock *)tb->field[n], n = (uintptr_t)tb & 1, \
             tb = (TranslationBlock *)((uintptr_t)tb & ~1))

#define PAGE_FOR_EACH_TB(pagedesc, tb, n)                       \
    TB_FOR_EACH_TAGGED((pagedesc)->first_tb, tb, n, page_next)

#define TB_FOR_EACH_JMP(head_tb, tb, n)                                 \
    TB_FOR_EACH_TAGGED((head_tb)->jmp_list_head, tb, n, jmp_list_next)

/*
 * In system mode we want L1_MAP to be based on ram offsets,
 * while in user mode we want it to be based on virtual addresses.
 *
 * TODO: For user mode, see the caveat re host vs guest virtual
 * address spaces near GUEST_ADDR_MAX.
 */
#if !defined(CONFIG_USER_ONLY)
#if HOST_LONG_BITS < TARGET_PHYS_ADDR_SPACE_BITS
# define L1_MAP_ADDR_SPACE_BITS  HOST_LONG_BITS
#else
# define L1_MAP_ADDR_SPACE_BITS  TARGET_PHYS_ADDR_SPACE_BITS
#endif
#else
# define L1_MAP_ADDR_SPACE_BITS  MIN(HOST_LONG_BITS, TARGET_ABI_BITS)
#endif

/* Size of the L2 (and L3, etc) page tables.  */
#define V_L2_BITS 10
#define V_L2_SIZE (1 << V_L2_BITS)

/* Make sure all possible CPU event bits fit in tb->trace_vcpu_dstate */
QEMU_BUILD_BUG_ON(CPU_TRACE_DSTATE_MAX_EVENTS >
                  sizeof_field(TranslationBlock, trace_vcpu_dstate)
                  * BITS_PER_BYTE);

/*
 * L1 Mapping properties
 */
static int v_l1_size;
static int v_l1_shift;
static int v_l2_levels;

/* The bottom level has pointers to PageDesc, and is indexed by
 * anything from 4 to (V_L2_BITS + 3) bits, depending on target page size.
 */
#define V_L1_MIN_BITS 4
#define V_L1_MAX_BITS (V_L2_BITS + 3)
#define V_L1_MAX_SIZE (1 << V_L1_MAX_BITS)

static void *l1_map[V_L1_MAX_SIZE];

/* code generation context */
TCGContext tcg_init_ctx;
__thread TCGContext *tcg_ctx;
TBContext tb_ctx;
bool parallel_cpus;

static void page_table_config_init(void)
{
    uint32_t v_l1_bits;

    assert(TARGET_PAGE_BITS);
    /* The bits remaining after N lower levels of page tables.  */
    v_l1_bits = (L1_MAP_ADDR_SPACE_BITS - TARGET_PAGE_BITS) % V_L2_BITS;
    if (v_l1_bits < V_L1_MIN_BITS) {
        v_l1_bits += V_L2_BITS;
    }

    v_l1_size = 1 << v_l1_bits;
    v_l1_shift = L1_MAP_ADDR_SPACE_BITS - TARGET_PAGE_BITS - v_l1_bits;
    v_l2_levels = v_l1_shift / V_L2_BITS - 1;

    assert(v_l1_bits <= V_L1_MAX_BITS);
    assert(v_l1_shift % V_L2_BITS == 0);
    assert(v_l2_levels >= 0);
}

void cpu_gen_init(void)
{
    tcg_context_init(&tcg_init_ctx);
}

/* Encode VAL as a signed leb128 sequence at P.
   Return P incremented past the encoded value.  */
static uint8_t *encode_sleb128(uint8_t *p, target_long val)
{
    int more, byte;

    do {
        byte = val & 0x7f;
        val >>= 7;
        more = !((val == 0 && (byte & 0x40) == 0)
                 || (val == -1 && (byte & 0x40) != 0));
        if (more) {
            byte |= 0x80;
        }
        *p++ = byte;
    } while (more);

    return p;
}

/* Decode a signed leb128 sequence at *PP; increment *PP past the
   decoded value.  Return the decoded value.  */
static target_long decode_sleb128(uint8_t **pp)
{
    uint8_t *p = *pp;
    target_long val = 0;
    int byte, shift = 0;

    do {
        byte = *p++;
        val |= (target_ulong)(byte & 0x7f) << shift;
        shift += 7;
    } while (byte & 0x80);
    if (shift < TARGET_LONG_BITS && (byte & 0x40)) {
        val |= -(target_ulong)1 << shift;
    }

    *pp = p;
    return val;
}

/* Encode the data collected about the instructions while compiling TB.
   Place the data at BLOCK, and return the number of bytes consumed.

   The logical table consists of TARGET_INSN_START_WORDS target_ulong's,
   which come from the target's insn_start data, followed by a uintptr_t
   which comes from the host pc of the end of the code implementing the insn.

   Each line of the table is encoded as sleb128 deltas from the previous
   line.  The seed for the first line is { tb->pc, 0..., tb->tc.ptr }.
   That is, the first column is seeded with the guest pc, the last column
   with the host pc, and the middle columns with zeros.  */

static int encode_search(TranslationBlock *tb, uint8_t *block)
{
    uint8_t *highwater = tcg_ctx->code_gen_highwater;
    uint8_t *p = block;
    int i, j, n;

    for (i = 0, n = tb->icount; i < n; ++i) {
        target_ulong prev;

        for (j = 0; j < TARGET_INSN_START_WORDS; ++j) {
            if (i == 0) {
                prev = (j == 0 ? tb->pc : 0);
            } else {
                prev = tcg_ctx->gen_insn_data[i - 1][j];
            }
            p = encode_sleb128(p, tcg_ctx->gen_insn_data[i][j] - prev);
        }
        prev = (i == 0 ? 0 : tcg_ctx->gen_insn_end_off[i - 1]);
        p = encode_sleb128(p, tcg_ctx->gen_insn_end_off[i] - prev);

        /* Test for (pending) buffer overflow.  The assumption is that any
           one row beginning below the high water mark cannot overrun
           the buffer completely.  Thus we can test for overflow after
           encoding a row without having to check during encoding.  */
        if (unlikely(p > highwater)) {
            return -1;
        }
    }

    return p - block;
}

/* The cpu state corresponding to 'searched_pc' is restored.
 * When reset_icount is true, current TB will be interrupted and
 * icount should be recalculated.
 */
static int cpu_restore_state_from_tb(CPUState *cpu, TranslationBlock *tb,
                                     uintptr_t searched_pc, bool reset_icount)
{
    target_ulong data[TARGET_INSN_START_WORDS] = { tb->pc };
    uintptr_t host_pc = (uintptr_t)tb->tc.ptr;
    CPUArchState *env = cpu->env_ptr;
    uint8_t *p = tb->tc.ptr + tb->tc.size;
    int i, j, num_insns = tb->icount;
#ifdef CONFIG_PROFILER
    TCGProfile *prof = &tcg_ctx->prof;
    int64_t ti = profile_getclock();
#endif

    searched_pc -= GETPC_ADJ;

    if (searched_pc < host_pc) {
        return -1;
    }

    /* Reconstruct the stored insn data while looking for the point at
       which the end of the insn exceeds the searched_pc.  */
    for (i = 0; i < num_insns; ++i) {
        for (j = 0; j < TARGET_INSN_START_WORDS; ++j) {
            data[j] += decode_sleb128(&p);
        }
        host_pc += decode_sleb128(&p);
        if (host_pc > searched_pc) {
            goto found;
        }
    }
    return -1;

 found:
    if (reset_icount && (tb_cflags(tb) & CF_USE_ICOUNT)) {
        assert(icount_enabled());
        /* Reset the cycle counter to the start of the block
           and shift if to the number of actually executed instructions */
        cpu_neg(cpu)->icount_decr.u16.low += num_insns - i;
    }
    restore_state_to_opc(env, tb, data);

#ifdef CONFIG_PROFILER
    qatomic_set(&prof->restore_time,
                prof->restore_time + profile_getclock() - ti);
    qatomic_set(&prof->restore_count, prof->restore_count + 1);
#endif
    return 0;
}

void tb_destroy(TranslationBlock *tb)
{
    qemu_spin_destroy(&tb->jmp_lock);
}

bool cpu_restore_state(CPUState *cpu, uintptr_t host_pc, bool will_exit)
{
    TranslationBlock *tb;
    bool r = false;
    uintptr_t check_offset;

    /* The host_pc has to be in the region of current code buffer. If
     * it is not we will not be able to resolve it here. The two cases
     * where host_pc will not be correct are:
     *
     *  - fault during translation (instruction fetch)
     *  - fault from helper (not using GETPC() macro)
     *
     * Either way we need return early as we can't resolve it here.
     *
     * We are using unsigned arithmetic so if host_pc <
     * tcg_init_ctx.code_gen_buffer check_offset will wrap to way
     * above the code_gen_buffer_size
     */
    check_offset = host_pc - (uintptr_t) tcg_init_ctx.code_gen_buffer;

    if (check_offset < tcg_init_ctx.code_gen_buffer_size) {
        tb = tcg_tb_lookup(host_pc);
        if (tb) {
            cpu_restore_state_from_tb(cpu, tb, host_pc, will_exit);
            if (tb_cflags(tb) & CF_NOCACHE) {
                /* one-shot translation, invalidate it immediately */
                tb_phys_invalidate(tb, -1);
                tcg_tb_remove(tb);
                tb_destroy(tb);
            }
            r = true;
        }
    }

    return r;
}

static void page_init(void)
{
    page_size_init();
    page_table_config_init();

#if defined(CONFIG_BSD) && defined(CONFIG_USER_ONLY)
    {
#ifdef HAVE_KINFO_GETVMMAP
        struct kinfo_vmentry *freep;
        int i, cnt;

        freep = kinfo_getvmmap(getpid(), &cnt);
        if (freep) {
            mmap_lock();
            for (i = 0; i < cnt; i++) {
                unsigned long startaddr, endaddr;

                startaddr = freep[i].kve_start;
                endaddr = freep[i].kve_end;
                if (h2g_valid(startaddr)) {
                    startaddr = h2g(startaddr) & TARGET_PAGE_MASK;

                    if (h2g_valid(endaddr)) {
                        endaddr = h2g(endaddr);
                        page_set_flags(startaddr, endaddr, PAGE_RESERVED);
                    } else {
#if TARGET_ABI_BITS <= L1_MAP_ADDR_SPACE_BITS
                        endaddr = ~0ul;
                        page_set_flags(startaddr, endaddr, PAGE_RESERVED);
#endif
                    }
                }
            }
            free(freep);
            mmap_unlock();
        }
#else
        FILE *f;

        last_brk = (unsigned long)sbrk(0);

        f = fopen("/compat/linux/proc/self/maps", "r");
        if (f) {
            mmap_lock();

            do {
                unsigned long startaddr, endaddr;
                int n;

                n = fscanf(f, "%lx-%lx %*[^\n]\n", &startaddr, &endaddr);

                if (n == 2 && h2g_valid(startaddr)) {
                    startaddr = h2g(startaddr) & TARGET_PAGE_MASK;

                    if (h2g_valid(endaddr)) {
                        endaddr = h2g(endaddr);
                    } else {
                        endaddr = ~0ul;
                    }
                    page_set_flags(startaddr, endaddr, PAGE_RESERVED);
                }
            } while (!feof(f));

            fclose(f);
            mmap_unlock();
        }
#endif
    }
#endif
}

static PageDesc *page_find_alloc(tb_page_addr_t index, int alloc)
{
    PageDesc *pd;
    void **lp;
    int i;

    /* Level 1.  Always allocated.  */
    lp = l1_map + ((index >> v_l1_shift) & (v_l1_size - 1));

    /* Level 2..N-1.  */
    for (i = v_l2_levels; i > 0; i--) {
        void **p = qatomic_rcu_read(lp);

        if (p == NULL) {
            void *existing;

            if (!alloc) {
                return NULL;
            }
            p = g_new0(void *, V_L2_SIZE);
            existing = qatomic_cmpxchg(lp, NULL, p);
            if (unlikely(existing)) {
                g_free(p);
                p = existing;
            }
        }

        lp = p + ((index >> (i * V_L2_BITS)) & (V_L2_SIZE - 1));
    }

    pd = qatomic_rcu_read(lp);
    if (pd == NULL) {
        void *existing;

        if (!alloc) {
            return NULL;
        }
        pd = g_new0(PageDesc, V_L2_SIZE);
#ifndef CONFIG_USER_ONLY
        {
            int i;

            for (i = 0; i < V_L2_SIZE; i++) {
                qemu_spin_init(&pd[i].lock);
            }
        }
#endif
        existing = qatomic_cmpxchg(lp, NULL, pd);
        if (unlikely(existing)) {
#ifndef CONFIG_USER_ONLY
            {
                int i;

                for (i = 0; i < V_L2_SIZE; i++) {
                    qemu_spin_destroy(&pd[i].lock);
                }
            }
#endif
            g_free(pd);
            pd = existing;
        }
    }

    return pd + (index & (V_L2_SIZE - 1));
}

static inline PageDesc *page_find(tb_page_addr_t index)
{
    return page_find_alloc(index, 0);
}

static void page_lock_pair(PageDesc **ret_p1, tb_page_addr_t phys1,
                           PageDesc **ret_p2, tb_page_addr_t phys2, int alloc);

/* In user-mode page locks aren't used; mmap_lock is enough */
#ifdef CONFIG_USER_ONLY

#define assert_page_locked(pd) tcg_debug_assert(have_mmap_lock())

static inline void page_lock(PageDesc *pd)
{ }

static inline void page_unlock(PageDesc *pd)
{ }

static inline void page_lock_tb(const TranslationBlock *tb)
{ }

static inline void page_unlock_tb(const TranslationBlock *tb)
{ }

struct page_collection *
page_collection_lock(tb_page_addr_t start, tb_page_addr_t end)
{
    return NULL;
}

void page_collection_unlock(struct page_collection *set)
{ }
#else /* !CONFIG_USER_ONLY */

#ifdef CONFIG_DEBUG_TCG

static __thread GHashTable *ht_pages_locked_debug;

static void ht_pages_locked_debug_init(void)
{
    if (ht_pages_locked_debug) {
        return;
    }
    ht_pages_locked_debug = g_hash_table_new(NULL, NULL);
}

static bool page_is_locked(const PageDesc *pd)
{
    PageDesc *found;

    ht_pages_locked_debug_init();
    found = g_hash_table_lookup(ht_pages_locked_debug, pd);
    return !!found;
}

static void page_lock__debug(PageDesc *pd)
{
    ht_pages_locked_debug_init();
    g_assert(!page_is_locked(pd));
    g_hash_table_insert(ht_pages_locked_debug, pd, pd);
}

static void page_unlock__debug(const PageDesc *pd)
{
    bool removed;

    ht_pages_locked_debug_init();
    g_assert(page_is_locked(pd));
    removed = g_hash_table_remove(ht_pages_locked_debug, pd);
    g_assert(removed);
}

static void
do_assert_page_locked(const PageDesc *pd, const char *file, int line)
{
    if (unlikely(!page_is_locked(pd))) {
        error_report("assert_page_lock: PageDesc %p not locked @ %s:%d",
                     pd, file, line);
        abort();
    }
}

#define assert_page_locked(pd) do_assert_page_locked(pd, __FILE__, __LINE__)

void assert_no_pages_locked(void)
{
    ht_pages_locked_debug_init();
    g_assert(g_hash_table_size(ht_pages_locked_debug) == 0);
}

#else /* !CONFIG_DEBUG_TCG */

#define assert_page_locked(pd)

static inline void page_lock__debug(const PageDesc *pd)
{
}

static inline void page_unlock__debug(const PageDesc *pd)
{
}

#endif /* CONFIG_DEBUG_TCG */

static inline void page_lock(PageDesc *pd)
{
    page_lock__debug(pd);
    qemu_spin_lock(&pd->lock);
}

static inline void page_unlock(PageDesc *pd)
{
    qemu_spin_unlock(&pd->lock);
    page_unlock__debug(pd);
}

/* lock the page(s) of a TB in the correct acquisition order */
static inline void page_lock_tb(const TranslationBlock *tb)
{
    page_lock_pair(NULL, tb->page_addr[0], NULL, tb->page_addr[1], 0);
}

static inline void page_unlock_tb(const TranslationBlock *tb)
{
    PageDesc *p1 = page_find(tb->page_addr[0] >> TARGET_PAGE_BITS);

    page_unlock(p1);
    if (unlikely(tb->page_addr[1] != -1)) {
        PageDesc *p2 = page_find(tb->page_addr[1] >> TARGET_PAGE_BITS);

        if (p2 != p1) {
            page_unlock(p2);
        }
    }
}

static inline struct page_entry *
page_entry_new(PageDesc *pd, tb_page_addr_t index)
{
    struct page_entry *pe = g_malloc(sizeof(*pe));

    pe->index = index;
    pe->pd = pd;
    pe->locked = false;
    return pe;
}

static void page_entry_destroy(gpointer p)
{
    struct page_entry *pe = p;

    g_assert(pe->locked);
    page_unlock(pe->pd);
    g_free(pe);
}

/* returns false on success */
static bool page_entry_trylock(struct page_entry *pe)
{
    bool busy;

    busy = qemu_spin_trylock(&pe->pd->lock);
    if (!busy) {
        g_assert(!pe->locked);
        pe->locked = true;
        page_lock__debug(pe->pd);
    }
    return busy;
}

static void do_page_entry_lock(struct page_entry *pe)
{
    page_lock(pe->pd);
    g_assert(!pe->locked);
    pe->locked = true;
}

static gboolean page_entry_lock(gpointer key, gpointer value, gpointer data)
{
    struct page_entry *pe = value;

    do_page_entry_lock(pe);
    return FALSE;
}

static gboolean page_entry_unlock(gpointer key, gpointer value, gpointer data)
{
    struct page_entry *pe = value;

    if (pe->locked) {
        pe->locked = false;
        page_unlock(pe->pd);
    }
    return FALSE;
}

/*
 * Trylock a page, and if successful, add the page to a collection.
 * Returns true ("busy") if the page could not be locked; false otherwise.
 */
static bool page_trylock_add(struct page_collection *set, tb_page_addr_t addr)
{
    tb_page_addr_t index = addr >> TARGET_PAGE_BITS;
    struct page_entry *pe;
    PageDesc *pd;

    pe = g_tree_lookup(set->tree, &index);
    if (pe) {
        return false;
    }

    pd = page_find(index);
    if (pd == NULL) {
        return false;
    }

    pe = page_entry_new(pd, index);
    g_tree_insert(set->tree, &pe->index, pe);

    /*
     * If this is either (1) the first insertion or (2) a page whose index
     * is higher than any other so far, just lock the page and move on.
     */
    if (set->max == NULL || pe->index > set->max->index) {
        set->max = pe;
        do_page_entry_lock(pe);
        return false;
    }
    /*
     * Try to acquire out-of-order lock; if busy, return busy so that we acquire
     * locks in order.
     */
    return page_entry_trylock(pe);
}

static gint tb_page_addr_cmp(gconstpointer ap, gconstpointer bp, gpointer udata)
{
    tb_page_addr_t a = *(const tb_page_addr_t *)ap;
    tb_page_addr_t b = *(const tb_page_addr_t *)bp;

    if (a == b) {
        return 0;
    } else if (a < b) {
        return -1;
    }
    return 1;
}

/*
 * Lock a range of pages ([@start,@end[) as well as the pages of all
 * intersecting TBs.
 * Locking order: acquire locks in ascending order of page index.
 */
struct page_collection *
page_collection_lock(tb_page_addr_t start, tb_page_addr_t end)
{
    struct page_collection *set = g_malloc(sizeof(*set));
    tb_page_addr_t index;
    PageDesc *pd;

    start >>= TARGET_PAGE_BITS;
    end   >>= TARGET_PAGE_BITS;
    g_assert(start <= end);

    set->tree = g_tree_new_full(tb_page_addr_cmp, NULL, NULL,
                                page_entry_destroy);
    set->max = NULL;
    assert_no_pages_locked();

 retry:
    g_tree_foreach(set->tree, page_entry_lock, NULL);

    for (index = start; index <= end; index++) {
        TranslationBlock *tb;
        int n;

        pd = page_find(index);
        if (pd == NULL) {
            continue;
        }
        if (page_trylock_add(set, index << TARGET_PAGE_BITS)) {
            g_tree_foreach(set->tree, page_entry_unlock, NULL);
            goto retry;
        }
        assert_page_locked(pd);
        PAGE_FOR_EACH_TB(pd, tb, n) {
            if (page_trylock_add(set, tb->page_addr[0]) ||
                (tb->page_addr[1] != -1 &&
                 page_trylock_add(set, tb->page_addr[1]))) {
                /* drop all locks, and reacquire in order */
                g_tree_foreach(set->tree, page_entry_unlock, NULL);
                goto retry;
            }
        }
    }
    return set;
}

void page_collection_unlock(struct page_collection *set)
{
    /* entries are unlocked and freed via page_entry_destroy */
    g_tree_destroy(set->tree);
    g_free(set);
}

#endif /* !CONFIG_USER_ONLY */

static void page_lock_pair(PageDesc **ret_p1, tb_page_addr_t phys1,
                           PageDesc **ret_p2, tb_page_addr_t phys2, int alloc)
{
    PageDesc *p1, *p2;
    tb_page_addr_t page1;
    tb_page_addr_t page2;

    assert_memory_lock();
    g_assert(phys1 != -1);

    page1 = phys1 >> TARGET_PAGE_BITS;
    page2 = phys2 >> TARGET_PAGE_BITS;

    p1 = page_find_alloc(page1, alloc);
    if (ret_p1) {
        *ret_p1 = p1;
    }
    if (likely(phys2 == -1)) {
        page_lock(p1);
        return;
    } else if (page1 == page2) {
        page_lock(p1);
        if (ret_p2) {
            *ret_p2 = p1;
        }
        return;
    }
    p2 = page_find_alloc(page2, alloc);
    if (ret_p2) {
        *ret_p2 = p2;
    }
    if (page1 < page2) {
        page_lock(p1);
        page_lock(p2);
    } else {
        page_lock(p2);
        page_lock(p1);
    }
}

/* Minimum size of the code gen buffer.  This number is randomly chosen,
   but not so small that we can't have a fair number of TB's live.  */
#define MIN_CODE_GEN_BUFFER_SIZE     (1 * MiB)

/* Maximum size of the code gen buffer we'd like to use.  Unless otherwise
   indicated, this is constrained by the range of direct branches on the
   host cpu, as used by the TCG implementation of goto_tb.  */
#if defined(__x86_64__)
# define MAX_CODE_GEN_BUFFER_SIZE  (2 * GiB)
#elif defined(__sparc__)
# define MAX_CODE_GEN_BUFFER_SIZE  (2 * GiB)
#elif defined(__powerpc64__)
# define MAX_CODE_GEN_BUFFER_SIZE  (2 * GiB)
#elif defined(__powerpc__)
# define MAX_CODE_GEN_BUFFER_SIZE  (32 * MiB)
#elif defined(__aarch64__)
# define MAX_CODE_GEN_BUFFER_SIZE  (2 * GiB)
#elif defined(__s390x__)
  /* We have a +- 4GB range on the branches; leave some slop.  */
# define MAX_CODE_GEN_BUFFER_SIZE  (3 * GiB)
#elif defined(__mips__)
  /* We have a 256MB branch region, but leave room to make sure the
     main executable is also within that region.  */
# define MAX_CODE_GEN_BUFFER_SIZE  (128 * MiB)
#else
# define MAX_CODE_GEN_BUFFER_SIZE  ((size_t)-1)
#endif

#if TCG_TARGET_REG_BITS == 32
#define DEFAULT_CODE_GEN_BUFFER_SIZE_1 (32 * MiB)
#ifdef CONFIG_USER_ONLY
/*
 * For user mode on smaller 32 bit systems we may run into trouble
 * allocating big chunks of data in the right place. On these systems
 * we utilise a static code generation buffer directly in the binary.
 */
#define USE_STATIC_CODE_GEN_BUFFER
#endif
#else /* TCG_TARGET_REG_BITS == 64 */
#ifdef CONFIG_USER_ONLY
/*
 * As user-mode emulation typically means running multiple instances
 * of the translator don't go too nuts with our default code gen
 * buffer lest we make things too hard for the OS.
 */
#define DEFAULT_CODE_GEN_BUFFER_SIZE_1 (128 * MiB)
#else
/*
 * We expect most system emulation to run one or two guests per host.
 * Users running large scale system emulation may want to tweak their
 * runtime setup via the tb-size control on the command line.
 */
#define DEFAULT_CODE_GEN_BUFFER_SIZE_1 (1 * GiB)
#endif
#endif

#define DEFAULT_CODE_GEN_BUFFER_SIZE \
  (DEFAULT_CODE_GEN_BUFFER_SIZE_1 < MAX_CODE_GEN_BUFFER_SIZE \
   ? DEFAULT_CODE_GEN_BUFFER_SIZE_1 : MAX_CODE_GEN_BUFFER_SIZE)

static inline size_t size_code_gen_buffer(size_t tb_size)
{
    /* Size the buffer.  */
    if (tb_size == 0) {
        size_t phys_mem = qemu_get_host_physmem();
        if (phys_mem == 0) {
            tb_size = DEFAULT_CODE_GEN_BUFFER_SIZE;
        } else {
            tb_size = MIN(DEFAULT_CODE_GEN_BUFFER_SIZE, phys_mem / 8);
        }
    }
    if (tb_size < MIN_CODE_GEN_BUFFER_SIZE) {
        tb_size = MIN_CODE_GEN_BUFFER_SIZE;
    }
    if (tb_size > MAX_CODE_GEN_BUFFER_SIZE) {
        tb_size = MAX_CODE_GEN_BUFFER_SIZE;
    }
    return tb_size;
}

#ifdef __mips__
/* In order to use J and JAL within the code_gen_buffer, we require
   that the buffer not cross a 256MB boundary.  */
static inline bool cross_256mb(void *addr, size_t size)
{
    return ((uintptr_t)addr ^ ((uintptr_t)addr + size)) & ~0x0ffffffful;
}

/* We weren't able to allocate a buffer without crossing that boundary,
   so make do with the larger portion of the buffer that doesn't cross.
   Returns the new base of the buffer, and adjusts code_gen_buffer_size.  */
static inline void *split_cross_256mb(void *buf1, size_t size1)
{
    void *buf2 = (void *)(((uintptr_t)buf1 + size1) & ~0x0ffffffful);
    size_t size2 = buf1 + size1 - buf2;

    size1 = buf2 - buf1;
    if (size1 < size2) {
        size1 = size2;
        buf1 = buf2;
    }

    tcg_ctx->code_gen_buffer_size = size1;
    return buf1;
}
#endif

#ifdef USE_STATIC_CODE_GEN_BUFFER
static uint8_t static_code_gen_buffer[DEFAULT_CODE_GEN_BUFFER_SIZE]
    __attribute__((aligned(CODE_GEN_ALIGN)));

static inline void *alloc_code_gen_buffer(void)
{
    void *buf = static_code_gen_buffer;
    void *end = static_code_gen_buffer + sizeof(static_code_gen_buffer);
    size_t size;

    /* page-align the beginning and end of the buffer */
    buf = QEMU_ALIGN_PTR_UP(buf, qemu_real_host_page_size);
    end = QEMU_ALIGN_PTR_DOWN(end, qemu_real_host_page_size);

    size = end - buf;

    /* Honor a command-line option limiting the size of the buffer.  */
    if (size > tcg_ctx->code_gen_buffer_size) {
        size = QEMU_ALIGN_DOWN(tcg_ctx->code_gen_buffer_size,
                               qemu_real_host_page_size);
    }
    tcg_ctx->code_gen_buffer_size = size;

#ifdef __mips__
    if (cross_256mb(buf, size)) {
        buf = split_cross_256mb(buf, size);
        size = tcg_ctx->code_gen_buffer_size;
    }
#endif

    if (qemu_mprotect_rwx(buf, size)) {
        abort();
    }
    qemu_madvise(buf, size, QEMU_MADV_HUGEPAGE);

    return buf;
}
#elif defined(_WIN32)
static inline void *alloc_code_gen_buffer(void)
{
    size_t size = tcg_ctx->code_gen_buffer_size;
    return VirtualAlloc(NULL, size, MEM_RESERVE | MEM_COMMIT,
                        PAGE_EXECUTE_READWRITE);
}
#else
static inline void *alloc_code_gen_buffer(void)
{
    int prot = PROT_WRITE | PROT_READ | PROT_EXEC;
    int flags = MAP_PRIVATE | MAP_ANONYMOUS;
    size_t size = tcg_ctx->code_gen_buffer_size;
    void *buf;

    buf = mmap(NULL, size, prot, flags, -1, 0);
    if (buf == MAP_FAILED) {
        return NULL;
    }

#ifdef __mips__
    if (cross_256mb(buf, size)) {
        /*
         * Try again, with the original still mapped, to avoid re-acquiring
         * the same 256mb crossing.
         */
        size_t size2;
        void *buf2 = mmap(NULL, size, prot, flags, -1, 0);
        switch ((int)(buf2 != MAP_FAILED)) {
        case 1:
            if (!cross_256mb(buf2, size)) {
                /* Success!  Use the new buffer.  */
                munmap(buf, size);
                break;
            }
            /* Failure.  Work with what we had.  */
            munmap(buf2, size);
            /* fallthru */
        default:
            /* Split the original buffer.  Free the smaller half.  */
            buf2 = split_cross_256mb(buf, size);
            size2 = tcg_ctx->code_gen_buffer_size;
            if (buf == buf2) {
                munmap(buf + size2, size - size2);
            } else {
                munmap(buf, size - size2);
            }
            size = size2;
            break;
        }
        buf = buf2;
    }
#endif

    /* Request large pages for the buffer.  */
    qemu_madvise(buf, size, QEMU_MADV_HUGEPAGE);

    return buf;
}
#endif /* USE_STATIC_CODE_GEN_BUFFER, WIN32, POSIX */

static inline void code_gen_alloc(size_t tb_size)
{
    tcg_ctx->code_gen_buffer_size = size_code_gen_buffer(tb_size);
    tcg_ctx->code_gen_buffer = alloc_code_gen_buffer();
    if (tcg_ctx->code_gen_buffer == NULL) {
        fprintf(stderr, "Could not allocate dynamic translator buffer\n");
        exit(1);
    }
}

static bool tb_cmp(const void *ap, const void *bp)
{
    const TranslationBlock *a = ap;
    const TranslationBlock *b = bp;

    return a->pc == b->pc &&
        a->cs_base == b->cs_base &&
        a->flags == b->flags &&
        (tb_cflags(a) & CF_HASH_MASK) == (tb_cflags(b) & CF_HASH_MASK) &&
        a->trace_vcpu_dstate == b->trace_vcpu_dstate &&
        a->page_addr[0] == b->page_addr[0] &&
        a->page_addr[1] == b->page_addr[1];
}

static void tb_htable_init(void)
{
    unsigned int mode = QHT_MODE_AUTO_RESIZE;

    qht_init(&tb_ctx.htable, tb_cmp, CODE_GEN_HTABLE_SIZE, mode);
}

/* Must be called before using the QEMU cpus. 'tb_size' is the size
   (in bytes) allocated to the translation buffer. Zero means default
   size. */
void tcg_exec_init(unsigned long tb_size)
{
    tcg_allowed = true;
    cpu_gen_init();
    page_init();
    tb_htable_init();
    code_gen_alloc(tb_size);
#if defined(CONFIG_SOFTMMU)
    /* There's no guest base to take into account, so go ahead and
       initialize the prologue now.  */
    tcg_prologue_init(tcg_ctx);
#endif
}

/* call with @p->lock held */
static inline void invalidate_page_bitmap(PageDesc *p)
{
    assert_page_locked(p);
#ifdef CONFIG_SOFTMMU
    g_free(p->code_bitmap);
    p->code_bitmap = NULL;
    p->code_write_count = 0;
#endif
}

/* Set to NULL all the 'first_tb' fields in all PageDescs. */
static void page_flush_tb_1(int level, void **lp)
{
    int i;

    if (*lp == NULL) {
        return;
    }
    if (level == 0) {
        PageDesc *pd = *lp;

        for (i = 0; i < V_L2_SIZE; ++i) {
            page_lock(&pd[i]);
            pd[i].first_tb = (uintptr_t)NULL;
            invalidate_page_bitmap(pd + i);
            page_unlock(&pd[i]);
        }
    } else {
        void **pp = *lp;

        for (i = 0; i < V_L2_SIZE; ++i) {
            page_flush_tb_1(level - 1, pp + i);
        }
    }
}

static void page_flush_tb(void)
{
    int i, l1_sz = v_l1_size;

    for (i = 0; i < l1_sz; i++) {
        page_flush_tb_1(v_l2_levels, l1_map + i);
    }
}

static gboolean tb_host_size_iter(gpointer key, gpointer value, gpointer data)
{
    const TranslationBlock *tb = value;
    size_t *size = data;

    *size += tb->tc.size;
    return false;
}

/* flush all the translation blocks */
static void do_tb_flush(CPUState *cpu, run_on_cpu_data tb_flush_count)
{
    bool did_flush = false;

    mmap_lock();
    /* If it is already been done on request of another CPU,
     * just retry.
     */
    if (tb_ctx.tb_flush_count != tb_flush_count.host_int) {
        goto done;
    }
    did_flush = true;

    if (DEBUG_TB_FLUSH_GATE) {
        size_t nb_tbs = tcg_nb_tbs();
        size_t host_size = 0;

        tcg_tb_foreach(tb_host_size_iter, &host_size);
        printf("qemu: flush code_size=%zu nb_tbs=%zu avg_tb_size=%zu\n",
               tcg_code_size(), nb_tbs, nb_tbs > 0 ? host_size / nb_tbs : 0);
    }

    CPU_FOREACH(cpu) {
        cpu_tb_jmp_cache_clear(cpu);
    }

    qht_reset_size(&tb_ctx.htable, CODE_GEN_HTABLE_SIZE);
    page_flush_tb();

    tcg_region_reset_all();
    /* XXX: flush processor icache at this point if cache flush is
       expensive */
    qatomic_mb_set(&tb_ctx.tb_flush_count, tb_ctx.tb_flush_count + 1);

done:
    mmap_unlock();
    if (did_flush) {
        qemu_plugin_flush_cb();
    }
}

void tb_flush(CPUState *cpu)
{
    if (tcg_enabled()) {
        unsigned tb_flush_count = qatomic_mb_read(&tb_ctx.tb_flush_count);

        if (cpu_in_exclusive_context(cpu)) {
            do_tb_flush(cpu, RUN_ON_CPU_HOST_INT(tb_flush_count));
        } else {
            async_safe_run_on_cpu(cpu, do_tb_flush,
                                  RUN_ON_CPU_HOST_INT(tb_flush_count));
        }
    }
}

/*
 * Formerly ifdef DEBUG_TB_CHECK. These debug functions are user-mode-only,
 * so in order to prevent bit rot we compile them unconditionally in user-mode,
 * and let the optimizer get rid of them by wrapping their user-only callers
 * with if (DEBUG_TB_CHECK_GATE).
 */
#ifdef CONFIG_USER_ONLY

static void do_tb_invalidate_check(void *p, uint32_t hash, void *userp)
{
    TranslationBlock *tb = p;
    target_ulong addr = *(target_ulong *)userp;

    if (!(addr + TARGET_PAGE_SIZE <= tb->pc || addr >= tb->pc + tb->size)) {
        printf("ERROR invalidate: address=" TARGET_FMT_lx
               " PC=%08lx size=%04x\n", addr, (long)tb->pc, tb->size);
    }
}

/* verify that all the pages have correct rights for code
 *
 * Called with mmap_lock held.
 */
static void tb_invalidate_check(target_ulong address)
{
    address &= TARGET_PAGE_MASK;
    qht_iter(&tb_ctx.htable, do_tb_invalidate_check, &address);
}

static void do_tb_page_check(void *p, uint32_t hash, void *userp)
{
    TranslationBlock *tb = p;
    int flags1, flags2;

    flags1 = page_get_flags(tb->pc);
    flags2 = page_get_flags(tb->pc + tb->size - 1);
    if ((flags1 & PAGE_WRITE) || (flags2 & PAGE_WRITE)) {
        printf("ERROR page flags: PC=%08lx size=%04x f1=%x f2=%x\n",
               (long)tb->pc, tb->size, flags1, flags2);
    }
}

/* verify that all the pages have correct rights for code */
static void tb_page_check(void)
{
    qht_iter(&tb_ctx.htable, do_tb_page_check, NULL);
}

#endif /* CONFIG_USER_ONLY */

/*
 * user-mode: call with mmap_lock held
 * !user-mode: call with @pd->lock held
 */
static inline void tb_page_remove(PageDesc *pd, TranslationBlock *tb)
{
    TranslationBlock *tb1;
    uintptr_t *pprev;
    unsigned int n1;

    assert_page_locked(pd);
    pprev = &pd->first_tb;
    PAGE_FOR_EACH_TB(pd, tb1, n1) {
        if (tb1 == tb) {
            *pprev = tb1->page_next[n1];
            return;
        }
        pprev = &tb1->page_next[n1];
    }
    g_assert_not_reached();
}

/* remove @orig from its @n_orig-th jump list */
static inline void tb_remove_from_jmp_list(TranslationBlock *orig, int n_orig)
{
    uintptr_t ptr, ptr_locked;
    TranslationBlock *dest;
    TranslationBlock *tb;
    uintptr_t *pprev;
    int n;

    /* mark the LSB of jmp_dest[] so that no further jumps can be inserted */
    ptr = qatomic_or_fetch(&orig->jmp_dest[n_orig], 1);
    dest = (TranslationBlock *)(ptr & ~1);
    if (dest == NULL) {
        return;
    }

    qemu_spin_lock(&dest->jmp_lock);
    /*
     * While acquiring the lock, the jump might have been removed if the
     * destination TB was invalidated; check again.
     */
    ptr_locked = qatomic_read(&orig->jmp_dest[n_orig]);
    if (ptr_locked != ptr) {
        qemu_spin_unlock(&dest->jmp_lock);
        /*
         * The only possibility is that the jump was unlinked via
         * tb_jump_unlink(dest). Seeing here another destination would be a bug,
         * because we set the LSB above.
         */
        g_assert(ptr_locked == 1 && dest->cflags & CF_INVALID);
        return;
    }
    /*
     * We first acquired the lock, and since the destination pointer matches,
     * we know for sure that @orig is in the jmp list.
     */
    pprev = &dest->jmp_list_head;
    TB_FOR_EACH_JMP(dest, tb, n) {
        if (tb == orig && n == n_orig) {
            *pprev = tb->jmp_list_next[n];
            /* no need to set orig->jmp_dest[n]; setting the LSB was enough */
            qemu_spin_unlock(&dest->jmp_lock);
            return;
        }
        pprev = &tb->jmp_list_next[n];
    }
    g_assert_not_reached();
}

/* reset the jump entry 'n' of a TB so that it is not chained to
   another TB */
static inline void tb_reset_jump(TranslationBlock *tb, int n)
{
    uintptr_t addr = (uintptr_t)(tb->tc.ptr + tb->jmp_reset_offset[n]);
    tb_set_jmp_target(tb, n, addr);
}

/* remove any jumps to the TB */
static inline void tb_jmp_unlink(TranslationBlock *dest)
{
    TranslationBlock *tb;
    int n;

    qemu_spin_lock(&dest->jmp_lock);

    TB_FOR_EACH_JMP(dest, tb, n) {
        tb_reset_jump(tb, n);
        qatomic_and(&tb->jmp_dest[n], (uintptr_t)NULL | 1);
        /* No need to clear the list entry; setting the dest ptr is enough */
    }
    dest->jmp_list_head = (uintptr_t)NULL;

    qemu_spin_unlock(&dest->jmp_lock);
}

/*
 * In user-mode, call with mmap_lock held.
 * In !user-mode, if @rm_from_page_list is set, call with the TB's pages'
 * locks held.
 */
static void do_tb_phys_invalidate(TranslationBlock *tb, bool rm_from_page_list)
{
    CPUState *cpu;
    PageDesc *p;
    uint32_t h;
    tb_page_addr_t phys_pc;

    assert_memory_lock();

    /* make sure no further incoming jumps will be chained to this TB */
    qemu_spin_lock(&tb->jmp_lock);
    qatomic_set(&tb->cflags, tb->cflags | CF_INVALID);
    qemu_spin_unlock(&tb->jmp_lock);

    /* remove the TB from the hash list */
    phys_pc = tb->page_addr[0] + (tb->pc & ~TARGET_PAGE_MASK);
    h = tb_hash_func(phys_pc, tb->pc, tb->flags, tb_cflags(tb) & CF_HASH_MASK,
                     tb->trace_vcpu_dstate);
    if (!(tb->cflags & CF_NOCACHE) &&
        !qht_remove(&tb_ctx.htable, tb, h)) {
        return;
    }

    /* remove the TB from the page list */
    if (rm_from_page_list) {
        p = page_find(tb->page_addr[0] >> TARGET_PAGE_BITS);
        tb_page_remove(p, tb);
        invalidate_page_bitmap(p);
        if (tb->page_addr[1] != -1) {
            p = page_find(tb->page_addr[1] >> TARGET_PAGE_BITS);
            tb_page_remove(p, tb);
            invalidate_page_bitmap(p);
        }
    }

    /* remove the TB from the hash list */
    h = tb_jmp_cache_hash_func(tb->pc);
    CPU_FOREACH(cpu) {
        if (qatomic_read(&cpu->tb_jmp_cache[h]) == tb) {
            qatomic_set(&cpu->tb_jmp_cache[h], NULL);
        }
    }

    /* suppress this TB from the two jump lists */
    tb_remove_from_jmp_list(tb, 0);
    tb_remove_from_jmp_list(tb, 1);

    /* suppress any remaining jumps to this TB */
    tb_jmp_unlink(tb);

    qatomic_set(&tcg_ctx->tb_phys_invalidate_count,
               tcg_ctx->tb_phys_invalidate_count + 1);
}

static void tb_phys_invalidate__locked(TranslationBlock *tb)
{
    do_tb_phys_invalidate(tb, true);
}

/* invalidate one TB
 *
 * Called with mmap_lock held in user-mode.
 */
void tb_phys_invalidate(TranslationBlock *tb, tb_page_addr_t page_addr)
{
    if (page_addr == -1 && tb->page_addr[0] != -1) {
        page_lock_tb(tb);
        do_tb_phys_invalidate(tb, true);
        page_unlock_tb(tb);
    } else {
        do_tb_phys_invalidate(tb, false);
    }
}

#ifdef CONFIG_SOFTMMU
/* call with @p->lock held */
static void build_page_bitmap(PageDesc *p)
{
    int n, tb_start, tb_end;
    TranslationBlock *tb;

    assert_page_locked(p);
    p->code_bitmap = bitmap_new(TARGET_PAGE_SIZE);

    PAGE_FOR_EACH_TB(p, tb, n) {
        /* NOTE: this is subtle as a TB may span two physical pages */
        if (n == 0) {
            /* NOTE: tb_end may be after the end of the page, but
               it is not a problem */
            tb_start = tb->pc & ~TARGET_PAGE_MASK;
            tb_end = tb_start + tb->size;
            if (tb_end > TARGET_PAGE_SIZE) {
                tb_end = TARGET_PAGE_SIZE;
             }
        } else {
            tb_start = 0;
            tb_end = ((tb->pc + tb->size) & ~TARGET_PAGE_MASK);
        }
        bitmap_set(p->code_bitmap, tb_start, tb_end - tb_start);
    }
}
#endif

/* add the tb in the target page and protect it if necessary
 *
 * Called with mmap_lock held for user-mode emulation.
 * Called with @p->lock held in !user-mode.
 */
static inline void tb_page_add(PageDesc *p, TranslationBlock *tb,
                               unsigned int n, tb_page_addr_t page_addr)
{
#ifndef CONFIG_USER_ONLY
    bool page_already_protected;
#endif

    assert_page_locked(p);

    tb->page_addr[n] = page_addr;
    tb->page_next[n] = p->first_tb;
#ifndef CONFIG_USER_ONLY
    page_already_protected = p->first_tb != (uintptr_t)NULL;
#endif
    p->first_tb = (uintptr_t)tb | n;
    invalidate_page_bitmap(p);

#if defined(CONFIG_USER_ONLY)
    if (p->flags & PAGE_WRITE) {
        target_ulong addr;
        PageDesc *p2;
        int prot;

        /* force the host page as non writable (writes will have a
           page fault + mprotect overhead) */
        page_addr &= qemu_host_page_mask;
        prot = 0;
        for (addr = page_addr; addr < page_addr + qemu_host_page_size;
            addr += TARGET_PAGE_SIZE) {

            p2 = page_find(addr >> TARGET_PAGE_BITS);
            if (!p2) {
                continue;
            }
            prot |= p2->flags;
            p2->flags &= ~PAGE_WRITE;
          }
        mprotect(g2h(page_addr), qemu_host_page_size,
                 (prot & PAGE_BITS) & ~PAGE_WRITE);
        if (DEBUG_TB_INVALIDATE_GATE) {
            printf("protecting code page: 0x" TB_PAGE_ADDR_FMT "\n", page_addr);
        }
    }
#else
    /* if some code is already present, then the pages are already
       protected. So we handle the case where only the first TB is
       allocated in a physical page */
    if (!page_already_protected) {
        tlb_protect_code(page_addr);
    }
#endif
}

/* add a new TB and link it to the physical page tables. phys_page2 is
 * (-1) to indicate that only one page contains the TB.
 *
 * Called with mmap_lock held for user-mode emulation.
 *
 * Returns a pointer @tb, or a pointer to an existing TB that matches @tb.
 * Note that in !user-mode, another thread might have already added a TB
 * for the same block of guest code that @tb corresponds to. In that case,
 * the caller should discard the original @tb, and use instead the returned TB.
 */
static TranslationBlock *
tb_link_page(TranslationBlock *tb, tb_page_addr_t phys_pc,
             tb_page_addr_t phys_page2)
{
    PageDesc *p;
    PageDesc *p2 = NULL;

    assert_memory_lock();

    if (phys_pc == -1) {
        /*
         * If the TB is not associated with a physical RAM page then
         * it must be a temporary one-insn TB, and we have nothing to do
         * except fill in the page_addr[] fields.
         */
        assert(tb->cflags & CF_NOCACHE);
        tb->page_addr[0] = tb->page_addr[1] = -1;
        return tb;
    }

    /*
     * Add the TB to the page list, acquiring first the pages's locks.
     * We keep the locks held until after inserting the TB in the hash table,
     * so that if the insertion fails we know for sure that the TBs are still
     * in the page descriptors.
     * Note that inserting into the hash table first isn't an option, since
     * we can only insert TBs that are fully initialized.
     */
    page_lock_pair(&p, phys_pc, &p2, phys_page2, 1);
    tb_page_add(p, tb, 0, phys_pc & TARGET_PAGE_MASK);
    if (p2) {
        tb_page_add(p2, tb, 1, phys_page2);
    } else {
        tb->page_addr[1] = -1;
    }

    if (!(tb->cflags & CF_NOCACHE)) {
        void *existing_tb = NULL;
        uint32_t h;

        /* add in the hash table */
        h = tb_hash_func(phys_pc, tb->pc, tb->flags, tb->cflags & CF_HASH_MASK,
                         tb->trace_vcpu_dstate);
        qht_insert(&tb_ctx.htable, tb, h, &existing_tb);

        /* remove TB from the page(s) if we couldn't insert it */
        if (unlikely(existing_tb)) {
            tb_page_remove(p, tb);
            invalidate_page_bitmap(p);
            if (p2) {
                tb_page_remove(p2, tb);
                invalidate_page_bitmap(p2);
            }
            tb = existing_tb;
        }
    }

    if (p2 && p2 != p) {
        page_unlock(p2);
    }
    page_unlock(p);

#ifdef CONFIG_USER_ONLY
    if (DEBUG_TB_CHECK_GATE) {
        tb_page_check();
    }
#endif
    return tb;
}

/* Called with mmap_lock held for user mode emulation.  */
TranslationBlock *tb_gen_code(CPUState *cpu,
                              target_ulong pc, target_ulong cs_base,
                              uint32_t flags, int cflags)
{
    CPUArchState *env = cpu->env_ptr;
    TranslationBlock *tb, *existing_tb;
    tb_page_addr_t phys_pc, phys_page2;
    target_ulong virt_page2;
    tcg_insn_unit *gen_code_buf;
    int gen_code_size, search_size, max_insns;
#ifdef CONFIG_PROFILER
    TCGProfile *prof = &tcg_ctx->prof;
    int64_t ti;
#endif

    assert_memory_lock();

    phys_pc = get_page_addr_code(env, pc);

    if (phys_pc == -1) {
        /* Generate a temporary TB with 1 insn in it */
        cflags &= ~CF_COUNT_MASK;
        cflags |= CF_NOCACHE | 1;
    }

    cflags &= ~CF_CLUSTER_MASK;
    cflags |= cpu->cluster_index << CF_CLUSTER_SHIFT;

    max_insns = cflags & CF_COUNT_MASK;
    if (max_insns == 0) {
        max_insns = CF_COUNT_MASK;
    }
    if (max_insns > TCG_MAX_INSNS) {
        max_insns = TCG_MAX_INSNS;
    }
    if (cpu->singlestep_enabled || singlestep) {
        max_insns = 1;
    }

 buffer_overflow:
    tb = tcg_tb_alloc(tcg_ctx);
    if (unlikely(!tb)) {
        /* flush must be done */
        tb_flush(cpu);
        mmap_unlock();
        /* Make the execution loop process the flush as soon as possible.  */
        cpu->exception_index = EXCP_INTERRUPT;
        cpu_loop_exit(cpu);
    }

    gen_code_buf = tcg_ctx->code_gen_ptr;
    tb->tc.ptr = gen_code_buf;
    tb->pc = pc;
    tb->cs_base = cs_base;
    tb->flags = flags;
    tb->cflags = cflags;
    tb->orig_tb = NULL;
    tb->trace_vcpu_dstate = *cpu->trace_dstate;
    tcg_ctx->tb_cflags = cflags;
 tb_overflow:

#ifdef CONFIG_PROFILER
    /* includes aborted translations because of exceptions */
    qatomic_set(&prof->tb_count1, prof->tb_count1 + 1);
    ti = profile_getclock();
#endif

    tcg_func_start(tcg_ctx);

    tcg_ctx->cpu = env_cpu(env);
    gen_intermediate_code(cpu, tb, max_insns);
    tcg_ctx->cpu = NULL;

    trace_translate_block(tb, tb->pc, tb->tc.ptr);

    /* generate machine code */
    tb->jmp_reset_offset[0] = TB_JMP_RESET_OFFSET_INVALID;
    tb->jmp_reset_offset[1] = TB_JMP_RESET_OFFSET_INVALID;
    tcg_ctx->tb_jmp_reset_offset = tb->jmp_reset_offset;
    if (TCG_TARGET_HAS_direct_jump) {
        tcg_ctx->tb_jmp_insn_offset = tb->jmp_target_arg;
        tcg_ctx->tb_jmp_target_addr = NULL;
    } else {
        tcg_ctx->tb_jmp_insn_offset = NULL;
        tcg_ctx->tb_jmp_target_addr = tb->jmp_target_arg;
    }

#ifdef CONFIG_PROFILER
    qatomic_set(&prof->tb_count, prof->tb_count + 1);
    qatomic_set(&prof->interm_time,
                prof->interm_time + profile_getclock() - ti);
    ti = profile_getclock();
#endif

    gen_code_size = tcg_gen_code(tcg_ctx, tb);
    if (unlikely(gen_code_size < 0)) {
        switch (gen_code_size) {
        case -1:
            /*
             * Overflow of code_gen_buffer, or the current slice of it.
             *
             * TODO: We don't need to re-do gen_intermediate_code, nor
             * should we re-do the tcg optimization currently hidden
             * inside tcg_gen_code.  All that should be required is to
             * flush the TBs, allocate a new TB, re-initialize it per
             * above, and re-do the actual code generation.
             */
            goto buffer_overflow;

        case -2:
            /*
             * The code generated for the TranslationBlock is too large.
             * The maximum size allowed by the unwind info is 64k.
             * There may be stricter constraints from relocations
             * in the tcg backend.
             *
             * Try again with half as many insns as we attempted this time.
             * If a single insn overflows, there's a bug somewhere...
             */
            max_insns = tb->icount;
            assert(max_insns > 1);
            max_insns /= 2;
            goto tb_overflow;

        default:
            g_assert_not_reached();
        }
    }
    search_size = encode_search(tb, (void *)gen_code_buf + gen_code_size);
    if (unlikely(search_size < 0)) {
        goto buffer_overflow;
    }
    tb->tc.size = gen_code_size;

#ifdef CONFIG_PROFILER
    qatomic_set(&prof->code_time, prof->code_time + profile_getclock() - ti);
    qatomic_set(&prof->code_in_len, prof->code_in_len + tb->size);
    qatomic_set(&prof->code_out_len, prof->code_out_len + gen_code_size);
    qatomic_set(&prof->search_out_len, prof->search_out_len + search_size);
#endif

#ifdef DEBUG_DISAS
    if (qemu_loglevel_mask(CPU_LOG_TB_OUT_ASM) &&
        qemu_log_in_addr_range(tb->pc)) {
        FILE *logfile = qemu_log_lock();
        int code_size, data_size = 0;
        size_t chunk_start;
        int insn = 0;

        if (tcg_ctx->data_gen_ptr) {
            code_size = tcg_ctx->data_gen_ptr - tb->tc.ptr;
            data_size = gen_code_size - code_size;
        } else {
            code_size = gen_code_size;
        }

        /* Dump header and the first instruction */
        qemu_log("OUT: [size=%d]\n", gen_code_size);
        qemu_log("  -- guest addr 0x" TARGET_FMT_lx " + tb prologue\n",
                 tcg_ctx->gen_insn_data[insn][0]);
        chunk_start = tcg_ctx->gen_insn_end_off[insn];
        log_disas(tb->tc.ptr, chunk_start);

        /*
         * Dump each instruction chunk, wrapping up empty chunks into
         * the next instruction. The whole array is offset so the
         * first entry is the beginning of the 2nd instruction.
         */
        while (insn < tb->icount) {
            size_t chunk_end = tcg_ctx->gen_insn_end_off[insn];
            if (chunk_end > chunk_start) {
                qemu_log("  -- guest addr 0x" TARGET_FMT_lx "\n",
                         tcg_ctx->gen_insn_data[insn][0]);
                log_disas(tb->tc.ptr + chunk_start, chunk_end - chunk_start);
                chunk_start = chunk_end;
            }
            insn++;
        }

        if (chunk_start < code_size) {
            qemu_log("  -- tb slow paths + alignment\n");
            log_disas(tb->tc.ptr + chunk_start, code_size - chunk_start);
        }

        /* Finally dump any data we may have after the block */
        if (data_size) {
            int i;
            qemu_log("  data: [size=%d]\n", data_size);
            for (i = 0; i < data_size; i += sizeof(tcg_target_ulong)) {
                if (sizeof(tcg_target_ulong) == 8) {
                    qemu_log("0x%08" PRIxPTR ":  .quad  0x%016" PRIx64 "\n",
                             (uintptr_t)tcg_ctx->data_gen_ptr + i,
                             *(uint64_t *)(tcg_ctx->data_gen_ptr + i));
                } else {
                    qemu_log("0x%08" PRIxPTR ":  .long  0x%08x\n",
                             (uintptr_t)tcg_ctx->data_gen_ptr + i,
                             *(uint32_t *)(tcg_ctx->data_gen_ptr + i));
                }
            }
        }
        qemu_log("\n");
        qemu_log_flush();
        qemu_log_unlock(logfile);
    }
#endif

    qatomic_set(&tcg_ctx->code_gen_ptr, (void *)
        ROUND_UP((uintptr_t)gen_code_buf + gen_code_size + search_size,
                 CODE_GEN_ALIGN));

    /* init jump list */
    qemu_spin_init(&tb->jmp_lock);
    tb->jmp_list_head = (uintptr_t)NULL;
    tb->jmp_list_next[0] = (uintptr_t)NULL;
    tb->jmp_list_next[1] = (uintptr_t)NULL;
    tb->jmp_dest[0] = (uintptr_t)NULL;
    tb->jmp_dest[1] = (uintptr_t)NULL;

    /* init original jump addresses which have been set during tcg_gen_code() */
    if (tb->jmp_reset_offset[0] != TB_JMP_RESET_OFFSET_INVALID) {
        tb_reset_jump(tb, 0);
    }
    if (tb->jmp_reset_offset[1] != TB_JMP_RESET_OFFSET_INVALID) {
        tb_reset_jump(tb, 1);
    }

    /* check next page if needed */
    virt_page2 = (pc + tb->size - 1) & TARGET_PAGE_MASK;
    phys_page2 = -1;
    if ((pc & TARGET_PAGE_MASK) != virt_page2) {
        phys_page2 = get_page_addr_code(env, virt_page2);
    }
    /*
     * No explicit memory barrier is required -- tb_link_page() makes the
     * TB visible in a consistent state.
     */
    existing_tb = tb_link_page(tb, phys_pc, phys_page2);
    /* if the TB already exists, discard what we just translated */
    if (unlikely(existing_tb != tb)) {
        uintptr_t orig_aligned = (uintptr_t)gen_code_buf;

        orig_aligned -= ROUND_UP(sizeof(*tb), qemu_icache_linesize);
        qatomic_set(&tcg_ctx->code_gen_ptr, (void *)orig_aligned);
        tb_destroy(tb);
        return existing_tb;
    }
    tcg_tb_insert(tb);
    return tb;
}

/*
 * @p must be non-NULL.
 * user-mode: call with mmap_lock held.
 * !user-mode: call with all @pages locked.
 */
static void
tb_invalidate_phys_page_range__locked(struct page_collection *pages,
                                      PageDesc *p, tb_page_addr_t start,
                                      tb_page_addr_t end,
                                      uintptr_t retaddr)
{
    TranslationBlock *tb;
    tb_page_addr_t tb_start, tb_end;
    int n;
#ifdef TARGET_HAS_PRECISE_SMC
    CPUState *cpu = current_cpu;
    CPUArchState *env = NULL;
    bool current_tb_not_found = retaddr != 0;
    bool current_tb_modified = false;
    TranslationBlock *current_tb = NULL;
    target_ulong current_pc = 0;
    target_ulong current_cs_base = 0;
    uint32_t current_flags = 0;
#endif /* TARGET_HAS_PRECISE_SMC */

    assert_page_locked(p);

#if defined(TARGET_HAS_PRECISE_SMC)
    if (cpu != NULL) {
        env = cpu->env_ptr;
    }
#endif

    /* we remove all the TBs in the range [start, end[ */
    /* XXX: see if in some cases it could be faster to invalidate all
       the code */
    PAGE_FOR_EACH_TB(p, tb, n) {
        assert_page_locked(p);
        /* NOTE: this is subtle as a TB may span two physical pages */
        if (n == 0) {
            /* NOTE: tb_end may be after the end of the page, but
               it is not a problem */
            tb_start = tb->page_addr[0] + (tb->pc & ~TARGET_PAGE_MASK);
            tb_end = tb_start + tb->size;
        } else {
            tb_start = tb->page_addr[1];
            tb_end = tb_start + ((tb->pc + tb->size) & ~TARGET_PAGE_MASK);
        }
        if (!(tb_end <= start || tb_start >= end)) {
#ifdef TARGET_HAS_PRECISE_SMC
            if (current_tb_not_found) {
                current_tb_not_found = false;
                /* now we have a real cpu fault */
                current_tb = tcg_tb_lookup(retaddr);
            }
            if (current_tb == tb &&
                (tb_cflags(current_tb) & CF_COUNT_MASK) != 1) {
                /*
                 * If we are modifying the current TB, we must stop
                 * its execution. We could be more precise by checking
                 * that the modification is after the current PC, but it
                 * would require a specialized function to partially
                 * restore the CPU state.
                 */
                current_tb_modified = true;
                cpu_restore_state_from_tb(cpu, current_tb, retaddr, true);
                cpu_get_tb_cpu_state(env, &current_pc, &current_cs_base,
                                     &current_flags);
            }
#endif /* TARGET_HAS_PRECISE_SMC */
            tb_phys_invalidate__locked(tb);
        }
    }
#if !defined(CONFIG_USER_ONLY)
    /* if no code remaining, no need to continue to use slow writes */
    if (!p->first_tb) {
        invalidate_page_bitmap(p);
        tlb_unprotect_code(start);
    }
#endif
#ifdef TARGET_HAS_PRECISE_SMC
    if (current_tb_modified) {
        page_collection_unlock(pages);
        /* Force execution of one insn next time.  */
        cpu->cflags_next_tb = 1 | curr_cflags();
        mmap_unlock();
        cpu_loop_exit_noexc(cpu);
    }
#endif
}

/*
 * Invalidate all TBs which intersect with the target physical address range
 * [start;end[. NOTE: start and end must refer to the *same* physical page.
 * 'is_cpu_write_access' should be true if called from a real cpu write
 * access: the virtual CPU will exit the current TB if code is modified inside
 * this TB.
 *
 * Called with mmap_lock held for user-mode emulation
 */
void tb_invalidate_phys_page_range(tb_page_addr_t start, tb_page_addr_t end)
{
    struct page_collection *pages;
    PageDesc *p;

    assert_memory_lock();

    p = page_find(start >> TARGET_PAGE_BITS);
    if (p == NULL) {
        return;
    }
    pages = page_collection_lock(start, end);
    tb_invalidate_phys_page_range__locked(pages, p, start, end, 0);
    page_collection_unlock(pages);
}

/*
 * Invalidate all TBs which intersect with the target physical address range
 * [start;end[. NOTE: start and end may refer to *different* physical pages.
 * 'is_cpu_write_access' should be true if called from a real cpu write
 * access: the virtual CPU will exit the current TB if code is modified inside
 * this TB.
 *
 * Called with mmap_lock held for user-mode emulation.
 */
#ifdef CONFIG_SOFTMMU
void tb_invalidate_phys_range(ram_addr_t start, ram_addr_t end)
#else
void tb_invalidate_phys_range(target_ulong start, target_ulong end)
#endif
{
    struct page_collection *pages;
    tb_page_addr_t next;

    assert_memory_lock();

    pages = page_collection_lock(start, end);
    for (next = (start & TARGET_PAGE_MASK) + TARGET_PAGE_SIZE;
         start < end;
         start = next, next += TARGET_PAGE_SIZE) {
        PageDesc *pd = page_find(start >> TARGET_PAGE_BITS);
        tb_page_addr_t bound = MIN(next, end);

        if (pd == NULL) {
            continue;
        }
        tb_invalidate_phys_page_range__locked(pages, pd, start, bound, 0);
    }
    page_collection_unlock(pages);
}

#ifdef CONFIG_SOFTMMU
/* len must be <= 8 and start must be a multiple of len.
 * Called via softmmu_template.h when code areas are written to with
 * iothread mutex not held.
 *
 * Call with all @pages in the range [@start, @start + len[ locked.
 */
void tb_invalidate_phys_page_fast(struct page_collection *pages,
                                  tb_page_addr_t start, int len,
                                  uintptr_t retaddr)
{
    PageDesc *p;

    assert_memory_lock();

    p = page_find(start >> TARGET_PAGE_BITS);
    if (!p) {
        return;
    }

    assert_page_locked(p);
    if (!p->code_bitmap &&
        ++p->code_write_count >= SMC_BITMAP_USE_THRESHOLD) {
        build_page_bitmap(p);
    }
    if (p->code_bitmap) {
        unsigned int nr;
        unsigned long b;

        nr = start & ~TARGET_PAGE_MASK;
        b = p->code_bitmap[BIT_WORD(nr)] >> (nr & (BITS_PER_LONG - 1));
        if (b & ((1 << len) - 1)) {
            goto do_invalidate;
        }
    } else {
    do_invalidate:
        tb_invalidate_phys_page_range__locked(pages, p, start, start + len,
                                              retaddr);
    }
}
#else
/* Called with mmap_lock held. If pc is not 0 then it indicates the
 * host PC of the faulting store instruction that caused this invalidate.
 * Returns true if the caller needs to abort execution of the current
 * TB (because it was modified by this store and the guest CPU has
 * precise-SMC semantics).
 */
static bool tb_invalidate_phys_page(tb_page_addr_t addr, uintptr_t pc)
{
    TranslationBlock *tb;
    PageDesc *p;
    int n;
#ifdef TARGET_HAS_PRECISE_SMC
    TranslationBlock *current_tb = NULL;
    CPUState *cpu = current_cpu;
    CPUArchState *env = NULL;
    int current_tb_modified = 0;
    target_ulong current_pc = 0;
    target_ulong current_cs_base = 0;
    uint32_t current_flags = 0;
#endif

    assert_memory_lock();

    addr &= TARGET_PAGE_MASK;
    p = page_find(addr >> TARGET_PAGE_BITS);
    if (!p) {
        return false;
    }

#ifdef TARGET_HAS_PRECISE_SMC
    if (p->first_tb && pc != 0) {
        current_tb = tcg_tb_lookup(pc);
    }
    if (cpu != NULL) {
        env = cpu->env_ptr;
    }
#endif
    assert_page_locked(p);
    PAGE_FOR_EACH_TB(p, tb, n) {
#ifdef TARGET_HAS_PRECISE_SMC
        if (current_tb == tb &&
            (tb_cflags(current_tb) & CF_COUNT_MASK) != 1) {
                /* If we are modifying the current TB, we must stop
                   its execution. We could be more precise by checking
                   that the modification is after the current PC, but it
                   would require a specialized function to partially
                   restore the CPU state */

            current_tb_modified = 1;
            cpu_restore_state_from_tb(cpu, current_tb, pc, true);
            cpu_get_tb_cpu_state(env, &current_pc, &current_cs_base,
                                 &current_flags);
        }
#endif /* TARGET_HAS_PRECISE_SMC */
        tb_phys_invalidate(tb, addr);
    }
    p->first_tb = (uintptr_t)NULL;
#ifdef TARGET_HAS_PRECISE_SMC
    if (current_tb_modified) {
        /* Force execution of one insn next time.  */
        cpu->cflags_next_tb = 1 | curr_cflags();
        return true;
    }
#endif

    return false;
}
#endif

/* user-mode: call with mmap_lock held */
void tb_check_watchpoint(CPUState *cpu, uintptr_t retaddr)
{
    TranslationBlock *tb;

    assert_memory_lock();

    tb = tcg_tb_lookup(retaddr);
    if (tb) {
        /* We can use retranslation to find the PC.  */
        cpu_restore_state_from_tb(cpu, tb, retaddr, true);
        tb_phys_invalidate(tb, -1);
    } else {
        /* The exception probably happened in a helper.  The CPU state should
           have been saved before calling it. Fetch the PC from there.  */
        CPUArchState *env = cpu->env_ptr;
        target_ulong pc, cs_base;
        tb_page_addr_t addr;
        uint32_t flags;

        cpu_get_tb_cpu_state(env, &pc, &cs_base, &flags);
        addr = get_page_addr_code(env, pc);
        if (addr != -1) {
            tb_invalidate_phys_range(addr, addr + 1);
        }
    }
}

#ifndef CONFIG_USER_ONLY
/* in deterministic execution mode, instructions doing device I/Os
 * must be at the end of the TB.
 *
 * Called by softmmu_template.h, with iothread mutex not held.
 */
void cpu_io_recompile(CPUState *cpu, uintptr_t retaddr)
{
#if defined(TARGET_MIPS) || defined(TARGET_SH4)
    CPUArchState *env = cpu->env_ptr;
#endif
    TranslationBlock *tb;
    uint32_t n;

    tb = tcg_tb_lookup(retaddr);
    if (!tb) {
        cpu_abort(cpu, "cpu_io_recompile: could not find TB for pc=%p",
                  (void *)retaddr);
    }
    cpu_restore_state_from_tb(cpu, tb, retaddr, true);

    /* On MIPS and SH, delay slot instructions can only be restarted if
       they were already the first instruction in the TB.  If this is not
       the first instruction in a TB then re-execute the preceding
       branch.  */
    n = 1;
#if defined(TARGET_MIPS)
    if ((env->hflags & MIPS_HFLAG_BMASK) != 0
        && env->active_tc.PC != tb->pc) {
        env->active_tc.PC -= (env->hflags & MIPS_HFLAG_B16 ? 2 : 4);
        cpu_neg(cpu)->icount_decr.u16.low++;
        env->hflags &= ~MIPS_HFLAG_BMASK;
        n = 2;
    }
#elif defined(TARGET_SH4)
    if ((env->flags & ((DELAY_SLOT | DELAY_SLOT_CONDITIONAL))) != 0
        && env->pc != tb->pc) {
        env->pc -= 2;
        cpu_neg(cpu)->icount_decr.u16.low++;
        env->flags &= ~(DELAY_SLOT | DELAY_SLOT_CONDITIONAL);
        n = 2;
    }
#endif

    /* Generate a new TB executing the I/O insn.  */
    cpu->cflags_next_tb = curr_cflags() | CF_LAST_IO | n;

    if (tb_cflags(tb) & CF_NOCACHE) {
        if (tb->orig_tb) {
            /* Invalidate original TB if this TB was generated in
             * cpu_exec_nocache() */
            tb_phys_invalidate(tb->orig_tb, -1);
        }
        tcg_tb_remove(tb);
        tb_destroy(tb);
    }

    qemu_log_mask_and_addr(CPU_LOG_EXEC, tb->pc,
                           "cpu_io_recompile: rewound execution of TB to "
                           TARGET_FMT_lx "\n", tb->pc);

    /* TODO: If env->pc != tb->pc (i.e. the faulting instruction was not
     * the first in the TB) then we end up generating a whole new TB and
     *  repeating the fault, which is horribly inefficient.
     *  Better would be to execute just this insn uncached, or generate a
     *  second new TB.
     */
    cpu_loop_exit_noexc(cpu);
}

static void tb_jmp_cache_clear_page(CPUState *cpu, target_ulong page_addr)
{
    unsigned int i, i0 = tb_jmp_cache_hash_page(page_addr);

    for (i = 0; i < TB_JMP_PAGE_SIZE; i++) {
        qatomic_set(&cpu->tb_jmp_cache[i0 + i], NULL);
    }
}

void tb_flush_jmp_cache(CPUState *cpu, target_ulong addr)
{
    /* Discard jump cache entries for any tb which might potentially
       overlap the flushed page.  */
    tb_jmp_cache_clear_page(cpu, addr - TARGET_PAGE_SIZE);
    tb_jmp_cache_clear_page(cpu, addr);
}

static void print_qht_statistics(struct qht_stats hst)
{
    uint32_t hgram_opts;
    size_t hgram_bins;
    char *hgram;

    if (!hst.head_buckets) {
        return;
    }
    qemu_printf("TB hash buckets     %zu/%zu (%0.2f%% head buckets used)\n",
                hst.used_head_buckets, hst.head_buckets,
                (double)hst.used_head_buckets / hst.head_buckets * 100);

    hgram_opts =  QDIST_PR_BORDER | QDIST_PR_LABELS;
    hgram_opts |= QDIST_PR_100X   | QDIST_PR_PERCENT;
    if (qdist_xmax(&hst.occupancy) - qdist_xmin(&hst.occupancy) == 1) {
        hgram_opts |= QDIST_PR_NODECIMAL;
    }
    hgram = qdist_pr(&hst.occupancy, 10, hgram_opts);
    qemu_printf("TB hash occupancy   %0.2f%% avg chain occ. Histogram: %s\n",
                qdist_avg(&hst.occupancy) * 100, hgram);
    g_free(hgram);

    hgram_opts = QDIST_PR_BORDER | QDIST_PR_LABELS;
    hgram_bins = qdist_xmax(&hst.chain) - qdist_xmin(&hst.chain);
    if (hgram_bins > 10) {
        hgram_bins = 10;
    } else {
        hgram_bins = 0;
        hgram_opts |= QDIST_PR_NODECIMAL | QDIST_PR_NOBINRANGE;
    }
    hgram = qdist_pr(&hst.chain, hgram_bins, hgram_opts);
    qemu_printf("TB hash avg chain   %0.3f buckets. Histogram: %s\n",
                qdist_avg(&hst.chain), hgram);
    g_free(hgram);
}

struct tb_tree_stats {
    size_t nb_tbs;
    size_t host_size;
    size_t target_size;
    size_t max_target_size;
    size_t direct_jmp_count;
    size_t direct_jmp2_count;
    size_t cross_page;
};

static gboolean tb_tree_stats_iter(gpointer key, gpointer value, gpointer data)
{
    const TranslationBlock *tb = value;
    struct tb_tree_stats *tst = data;

    tst->nb_tbs++;
    tst->host_size += tb->tc.size;
    tst->target_size += tb->size;
    if (tb->size > tst->max_target_size) {
        tst->max_target_size = tb->size;
    }
    if (tb->page_addr[1] != -1) {
        tst->cross_page++;
    }
    if (tb->jmp_reset_offset[0] != TB_JMP_RESET_OFFSET_INVALID) {
        tst->direct_jmp_count++;
        if (tb->jmp_reset_offset[1] != TB_JMP_RESET_OFFSET_INVALID) {
            tst->direct_jmp2_count++;
        }
    }
    return false;
}

void dump_exec_info(void)
{
    struct tb_tree_stats tst = {};
    struct qht_stats hst;
    size_t nb_tbs, flush_full, flush_part, flush_elide;

    tcg_tb_foreach(tb_tree_stats_iter, &tst);
    nb_tbs = tst.nb_tbs;
    /* XXX: avoid using doubles ? */
    qemu_printf("Translation buffer state:\n");
    /*
     * Report total code size including the padding and TB structs;
     * otherwise users might think "-tb-size" is not honoured.
     * For avg host size we use the precise numbers from tb_tree_stats though.
     */
    qemu_printf("gen code size       %zu/%zu\n",
                tcg_code_size(), tcg_code_capacity());
    qemu_printf("TB count            %zu\n", nb_tbs);
    qemu_printf("TB avg target size  %zu max=%zu bytes\n",
                nb_tbs ? tst.target_size / nb_tbs : 0,
                tst.max_target_size);
    qemu_printf("TB avg host size    %zu bytes (expansion ratio: %0.1f)\n",
                nb_tbs ? tst.host_size / nb_tbs : 0,
                tst.target_size ? (double)tst.host_size / tst.target_size : 0);
    qemu_printf("cross page TB count %zu (%zu%%)\n", tst.cross_page,
                nb_tbs ? (tst.cross_page * 100) / nb_tbs : 0);
    qemu_printf("direct jump count   %zu (%zu%%) (2 jumps=%zu %zu%%)\n",
                tst.direct_jmp_count,
                nb_tbs ? (tst.direct_jmp_count * 100) / nb_tbs : 0,
                tst.direct_jmp2_count,
                nb_tbs ? (tst.direct_jmp2_count * 100) / nb_tbs : 0);

    qht_statistics_init(&tb_ctx.htable, &hst);
    print_qht_statistics(hst);
    qht_statistics_destroy(&hst);

    qemu_printf("\nStatistics:\n");
    qemu_printf("TB flush count      %u\n",
                qatomic_read(&tb_ctx.tb_flush_count));
    qemu_printf("TB invalidate count %zu\n",
                tcg_tb_phys_invalidate_count());

    tlb_flush_counts(&flush_full, &flush_part, &flush_elide);
    qemu_printf("TLB full flushes    %zu\n", flush_full);
    qemu_printf("TLB partial flushes %zu\n", flush_part);
    qemu_printf("TLB elided flushes  %zu\n", flush_elide);
    tcg_dump_info();
}

void dump_opcount_info(void)
{
    tcg_dump_op_count();
}

#else /* CONFIG_USER_ONLY */

void cpu_interrupt(CPUState *cpu, int mask)
{
    g_assert(qemu_mutex_iothread_locked());
    cpu->interrupt_request |= mask;
    qatomic_set(&cpu_neg(cpu)->icount_decr.u16.high, -1);
}

/*
 * Walks guest process memory "regions" one by one
 * and calls callback function 'fn' for each region.
 */
struct walk_memory_regions_data {
    walk_memory_regions_fn fn;
    void *priv;
    target_ulong start;
    int prot;
};

static int walk_memory_regions_end(struct walk_memory_regions_data *data,
                                   target_ulong end, int new_prot)
{
    if (data->start != -1u) {
        int rc = data->fn(data->priv, data->start, end, data->prot);
        if (rc != 0) {
            return rc;
        }
    }

    data->start = (new_prot ? end : -1u);
    data->prot = new_prot;

    return 0;
}

static int walk_memory_regions_1(struct walk_memory_regions_data *data,
                                 target_ulong base, int level, void **lp)
{
    target_ulong pa;
    int i, rc;

    if (*lp == NULL) {
        return walk_memory_regions_end(data, base, 0);
    }

    if (level == 0) {
        PageDesc *pd = *lp;

        for (i = 0; i < V_L2_SIZE; ++i) {
            int prot = pd[i].flags;

            pa = base | (i << TARGET_PAGE_BITS);
            if (prot != data->prot) {
                rc = walk_memory_regions_end(data, pa, prot);
                if (rc != 0) {
                    return rc;
                }
            }
        }
    } else {
        void **pp = *lp;

        for (i = 0; i < V_L2_SIZE; ++i) {
            pa = base | ((target_ulong)i <<
                (TARGET_PAGE_BITS + V_L2_BITS * level));
            rc = walk_memory_regions_1(data, pa, level - 1, pp + i);
            if (rc != 0) {
                return rc;
            }
        }
    }

    return 0;
}

int walk_memory_regions(void *priv, walk_memory_regions_fn fn)
{
    struct walk_memory_regions_data data;
    uintptr_t i, l1_sz = v_l1_size;

    data.fn = fn;
    data.priv = priv;
    data.start = -1u;
    data.prot = 0;

    for (i = 0; i < l1_sz; i++) {
        target_ulong base = i << (v_l1_shift + TARGET_PAGE_BITS);
        int rc = walk_memory_regions_1(&data, base, v_l2_levels, l1_map + i);
        if (rc != 0) {
            return rc;
        }
    }

    return walk_memory_regions_end(&data, 0, 0);
}

static int dump_region(void *priv, target_ulong start,
    target_ulong end, unsigned long prot)
{
    FILE *f = (FILE *)priv;

    (void) fprintf(f, TARGET_FMT_lx"-"TARGET_FMT_lx
        " "TARGET_FMT_lx" %c%c%c\n",
        start, end, end - start,
        ((prot & PAGE_READ) ? 'r' : '-'),
        ((prot & PAGE_WRITE) ? 'w' : '-'),
        ((prot & PAGE_EXEC) ? 'x' : '-'));

    return 0;
}

/* dump memory mappings */
void page_dump(FILE *f)
{
    const int length = sizeof(target_ulong) * 2;
    (void) fprintf(f, "%-*s %-*s %-*s %s\n",
            length, "start", length, "end", length, "size", "prot");
    walk_memory_regions(f, dump_region);
}

int page_get_flags(target_ulong address)
{
    PageDesc *p;

    p = page_find(address >> TARGET_PAGE_BITS);
    if (!p) {
        return 0;
    }
    return p->flags;
}

/* Modify the flags of a page and invalidate the code if necessary.
   The flag PAGE_WRITE_ORG is positioned automatically depending
   on PAGE_WRITE.  The mmap_lock should already be held.  */
void page_set_flags(target_ulong start, target_ulong end, int flags)
{
    target_ulong addr, len;

    /* This function should never be called with addresses outside the
       guest address space.  If this assert fires, it probably indicates
       a missing call to h2g_valid.  */
    assert(end - 1 <= GUEST_ADDR_MAX);
    assert(start < end);
    assert_memory_lock();

    start = start & TARGET_PAGE_MASK;
    end = TARGET_PAGE_ALIGN(end);

    if (flags & PAGE_WRITE) {
        flags |= PAGE_WRITE_ORG;
    }

    for (addr = start, len = end - start;
         len != 0;
         len -= TARGET_PAGE_SIZE, addr += TARGET_PAGE_SIZE) {
        PageDesc *p = page_find_alloc(addr >> TARGET_PAGE_BITS, 1);

        /* If the write protection bit is set, then we invalidate
           the code inside.  */
        if (!(p->flags & PAGE_WRITE) &&
            (flags & PAGE_WRITE) &&
            p->first_tb) {
            tb_invalidate_phys_page(addr, 0);
        }
        p->flags = flags;
    }
}

int page_check_range(target_ulong start, target_ulong len, int flags)
{
    PageDesc *p;
    target_ulong end;
    target_ulong addr;

    /* This function should never be called with addresses outside the
       guest address space.  If this assert fires, it probably indicates
       a missing call to h2g_valid.  */
    if (TARGET_ABI_BITS > L1_MAP_ADDR_SPACE_BITS) {
        assert(start < ((target_ulong)1 << L1_MAP_ADDR_SPACE_BITS));
    }

    if (len == 0) {
        return 0;
    }
    if (start + len - 1 < start) {
        /* We've wrapped around.  */
        return -1;
    }

    /* must do before we loose bits in the next step */
    end = TARGET_PAGE_ALIGN(start + len);
    start = start & TARGET_PAGE_MASK;

    for (addr = start, len = end - start;
         len != 0;
         len -= TARGET_PAGE_SIZE, addr += TARGET_PAGE_SIZE) {
        p = page_find(addr >> TARGET_PAGE_BITS);
        if (!p) {
            return -1;
        }
        if (!(p->flags & PAGE_VALID)) {
            return -1;
        }

        if ((flags & PAGE_READ) && !(p->flags & PAGE_READ)) {
            return -1;
        }
        if (flags & PAGE_WRITE) {
            if (!(p->flags & PAGE_WRITE_ORG)) {
                return -1;
            }
            /* unprotect the page if it was put read-only because it
               contains translated code */
            if (!(p->flags & PAGE_WRITE)) {
                if (!page_unprotect(addr, 0)) {
                    return -1;
                }
            }
        }
    }
    return 0;
}

/* called from signal handler: invalidate the code and unprotect the
 * page. Return 0 if the fault was not handled, 1 if it was handled,
 * and 2 if it was handled but the caller must cause the TB to be
 * immediately exited. (We can only return 2 if the 'pc' argument is
 * non-zero.)
 */
int page_unprotect(target_ulong address, uintptr_t pc)
{
    unsigned int prot;
    bool current_tb_invalidated;
    PageDesc *p;
    target_ulong host_start, host_end, addr;

    /* Technically this isn't safe inside a signal handler.  However we
       know this only ever happens in a synchronous SEGV handler, so in
       practice it seems to be ok.  */
    mmap_lock();

    p = page_find(address >> TARGET_PAGE_BITS);
    if (!p) {
        mmap_unlock();
        return 0;
    }

    /* if the page was really writable, then we change its
       protection back to writable */
    if (p->flags & PAGE_WRITE_ORG) {
        current_tb_invalidated = false;
        if (p->flags & PAGE_WRITE) {
            /* If the page is actually marked WRITE then assume this is because
             * this thread raced with another one which got here first and
             * set the page to PAGE_WRITE and did the TB invalidate for us.
             */
#ifdef TARGET_HAS_PRECISE_SMC
            TranslationBlock *current_tb = tcg_tb_lookup(pc);
            if (current_tb) {
                current_tb_invalidated = tb_cflags(current_tb) & CF_INVALID;
            }
#endif
        } else {
            host_start = address & qemu_host_page_mask;
            host_end = host_start + qemu_host_page_size;

            prot = 0;
            for (addr = host_start; addr < host_end; addr += TARGET_PAGE_SIZE) {
                p = page_find(addr >> TARGET_PAGE_BITS);
                p->flags |= PAGE_WRITE;
                prot |= p->flags;

                /* and since the content will be modified, we must invalidate
                   the corresponding translated code. */
                current_tb_invalidated |= tb_invalidate_phys_page(addr, pc);
#ifdef CONFIG_USER_ONLY
                if (DEBUG_TB_CHECK_GATE) {
                    tb_invalidate_check(addr);
                }
#endif
            }
            mprotect((void *)g2h(host_start), qemu_host_page_size,
                     prot & PAGE_BITS);
        }
        mmap_unlock();
        /* If current TB was invalidated return to main loop */
        return current_tb_invalidated ? 2 : 1;
    }
    mmap_unlock();
    return 0;
}
#endif /* CONFIG_USER_ONLY */

/* This is a wrapper for common code that can not use CONFIG_SOFTMMU */
void tcg_flush_softmmu_tlb(CPUState *cs)
{
#ifdef CONFIG_SOFTMMU
    tlb_flush(cs);
#endif
}