unicorn/tests/unit/test_x86.c

#include "unicorn_test.h"

const uint64_t code_start = 0x1000;
const uint64_t code_len = 0x4000;

static void uc_common_setup(uc_engine **uc, uc_arch arch, uc_mode mode,
                            const char *code, uint64_t size)
{
    OK(uc_open(arch, mode, uc));
    OK(uc_mem_map(*uc, code_start, code_len, UC_PROT_ALL));
    OK(uc_mem_write(*uc, code_start, code, size));
}

typedef struct _INSN_IN_RESULT {
    uint32_t port;
    int size;
} INSN_IN_RESULT;

static void test_x86_in_callback(uc_engine *uc, uint32_t port, int size,
                                 void *user_data)
{
    INSN_IN_RESULT *result = (INSN_IN_RESULT *)user_data;

    result->port = port;
    result->size = size;
}

static void test_x86_in()
{
    uc_engine *uc;
    uc_hook hook;
    char code[] = "\xe5\x10"; // IN eax, 0x10
    INSN_IN_RESULT result;

    uc_common_setup(&uc, UC_ARCH_X86, UC_MODE_32, code, sizeof(code) - 1);
    OK(uc_hook_add(uc, &hook, UC_HOOK_INSN, test_x86_in_callback, &result, 1, 0,
                   UC_X86_INS_IN));

    OK(uc_emu_start(uc, code_start, code_start + sizeof(code) - 1, 0, 0));
    TEST_CHECK(result.port == 0x10);
    TEST_CHECK(result.size == 4);

    OK(uc_hook_del(uc, hook));
    OK(uc_close(uc));
}

typedef struct _INSN_OUT_RESULT {
    uint32_t port;
    int size;
    uint32_t value;
} INSN_OUT_RESULT;

static void test_x86_out_callback(uc_engine *uc, uint32_t port, int size,
                                  uint32_t value, void *user_data)
{
    INSN_OUT_RESULT *result = (INSN_OUT_RESULT *)user_data;

    result->port = port;
    result->size = size;
    result->value = value;
}

static void test_x86_out()
{
    uc_engine *uc;
    uc_hook hook;
    char code[] = "\xb0\x32\xe6\x46"; // MOV al, 0x32; OUT  0x46, al;
    INSN_OUT_RESULT result;

    uc_common_setup(&uc, UC_ARCH_X86, UC_MODE_32, code, sizeof(code) - 1);
    OK(uc_hook_add(uc, &hook, UC_HOOK_INSN, test_x86_out_callback, &result, 1,
                   0, UC_X86_INS_OUT));

    OK(uc_emu_start(uc, code_start, code_start + sizeof(code) - 1, 0, 0));
    TEST_CHECK(result.port == 0x46);
    TEST_CHECK(result.size == 1);
    TEST_CHECK(result.value == 0x32);

    OK(uc_hook_del(uc, hook));
    OK(uc_close(uc));
}

typedef struct _MEM_HOOK_RESULT {
    uc_mem_type type;
    uint64_t address;
    int size;
    uint64_t value;
} MEM_HOOK_RESULT;

typedef struct _MEM_HOOK_RESULTS {
    uint64_t count;
    MEM_HOOK_RESULT results[16];
} MEM_HOOK_RESULTS;

static bool test_x86_mem_hook_all_callback(uc_engine *uc, uc_mem_type type,
                                           uint64_t address, int size,
                                           uint64_t value, void *user_data)
{
    MEM_HOOK_RESULTS *r = (MEM_HOOK_RESULTS *)user_data;
    uint64_t count = r->count;

    if (count >= 16) {
        TEST_ASSERT(false);
    }

    r->results[count].type = type;
    r->results[count].address = address;
    r->results[count].size = size;
    r->results[count].value = value;
    r->count++;

    if (type == UC_MEM_READ_UNMAPPED) {
        uc_mem_map(uc, address, 0x1000, UC_PROT_ALL);
    }

    return true;
}

static void test_x86_mem_hook_all()
{
    uc_engine *uc;
    uc_hook hook;
    // mov eax, 0xdeadbeef;
    // mov [0x8000], eax;
    // mov eax, [0x10000];
    char code[] =
        "\xb8\xef\xbe\xad\xde\xa3\x00\x80\x00\x00\xa1\x00\x00\x01\x00";
    MEM_HOOK_RESULTS r = {0};
    MEM_HOOK_RESULT expects[3] = {{UC_MEM_WRITE, 0x8000, 4, 0xdeadbeef},
                                  {UC_MEM_READ_UNMAPPED, 0x10000, 4, 0},
                                  {UC_MEM_READ, 0x10000, 4, 0}};

    uc_common_setup(&uc, UC_ARCH_X86, UC_MODE_32, code, sizeof(code) - 1);
    OK(uc_mem_map(uc, 0x8000, 0x1000, UC_PROT_ALL));
    OK(uc_hook_add(uc, &hook, UC_HOOK_MEM_VALID | UC_HOOK_MEM_INVALID,
                   test_x86_mem_hook_all_callback, &r, 1, 0));

    OK(uc_emu_start(uc, code_start, code_start + sizeof(code) - 1, 0, 0));
    TEST_CHECK(r.count == 3);
    for (int i = 0; i < r.count; i++) {
        TEST_CHECK(expects[i].type == r.results[i].type);
        TEST_CHECK(expects[i].address == r.results[i].address);
        TEST_CHECK(expects[i].size == r.results[i].size);
        TEST_CHECK(expects[i].value == r.results[i].value);
    }

    OK(uc_hook_del(uc, hook));
    OK(uc_close(uc));
}

static void test_x86_inc_dec_pxor()
{
    uc_engine *uc;
    char code[] =
        "\x41\x4a\x66\x0f\xef\xc1"; // INC ecx; DEC edx; PXOR xmm0, xmm1
    int r_ecx = 0x1234;
    int r_edx = 0x7890;
    uint64_t r_xmm0[2] = {0x08090a0b0c0d0e0f, 0x0001020304050607};
    uint64_t r_xmm1[2] = {0x8090a0b0c0d0e0f0, 0x0010203040506070};

    uc_common_setup(&uc, UC_ARCH_X86, UC_MODE_32, code, sizeof(code) - 1);
    OK(uc_reg_write(uc, UC_X86_REG_ECX, &r_ecx));
    OK(uc_reg_write(uc, UC_X86_REG_EDX, &r_edx));
    OK(uc_reg_write(uc, UC_X86_REG_XMM0, &r_xmm0));
    OK(uc_reg_write(uc, UC_X86_REG_XMM1, &r_xmm1));

    OK(uc_emu_start(uc, code_start, code_start + sizeof(code) - 1, 0, 0));

    OK(uc_reg_read(uc, UC_X86_REG_ECX, &r_ecx));
    OK(uc_reg_read(uc, UC_X86_REG_EDX, &r_edx));
    OK(uc_reg_read(uc, UC_X86_REG_XMM0, &r_xmm0));

    TEST_CHECK(r_ecx == 0x1235);
    TEST_CHECK(r_edx == 0x788f);
    TEST_CHECK(r_xmm0[0] == 0x8899aabbccddeeff);
    TEST_CHECK(r_xmm0[1] == 0x0011223344556677);

    OK(uc_close(uc));
}

static void test_x86_relative_jump()
{
    uc_engine *uc;
    char code[] = "\xeb\x02\x90\x90\x90\x90\x90\x90"; // jmp 4; nop; nop; nop;
                                                      // nop; nop; nop
    int r_eip;

    uc_common_setup(&uc, UC_ARCH_X86, UC_MODE_32, code, sizeof(code) - 1);

    OK(uc_emu_start(uc, code_start, code_start + 4, 0, 0));

    OK(uc_reg_read(uc, UC_X86_REG_EIP, &r_eip));

    TEST_CHECK(r_eip == code_start + 4);

    OK(uc_close(uc));
}

static void test_x86_loop()
{
    uc_engine *uc;
    char code[] = "\x41\x4a\xeb\xfe"; // inc ecx; dec edx; jmp $;
    int r_ecx = 0x1234;
    int r_edx = 0x7890;

    uc_common_setup(&uc, UC_ARCH_X86, UC_MODE_32, code, sizeof(code) - 1);
    OK(uc_reg_write(uc, UC_X86_REG_ECX, &r_ecx));
    OK(uc_reg_write(uc, UC_X86_REG_EDX, &r_edx));

    OK(uc_emu_start(uc, code_start, code_start + sizeof(code) - 1, 1 * 1000000,
                    0));

    OK(uc_reg_read(uc, UC_X86_REG_ECX, &r_ecx));
    OK(uc_reg_read(uc, UC_X86_REG_EDX, &r_edx));

    TEST_CHECK(r_ecx == 0x1235);
    TEST_CHECK(r_edx == 0x788f);

    OK(uc_close(uc));
}

static void test_x86_invalid_mem_read()
{
    uc_engine *uc;
    char code[] = "\x8b\x0d\xaa\xaa\xaa\xaa"; // mov  ecx, [0xAAAAAAAA]

    uc_common_setup(&uc, UC_ARCH_X86, UC_MODE_32, code, sizeof(code) - 1);

    uc_assert_err(
        UC_ERR_READ_UNMAPPED,
        uc_emu_start(uc, code_start, code_start + sizeof(code) - 1, 0, 0));

    OK(uc_close(uc));
}

static void test_x86_invalid_mem_write()
{
    uc_engine *uc;
    char code[] = "\x89\x0d\xaa\xaa\xaa\xaa"; // mov  ecx, [0xAAAAAAAA]

    uc_common_setup(&uc, UC_ARCH_X86, UC_MODE_32, code, sizeof(code) - 1);

    uc_assert_err(
        UC_ERR_WRITE_UNMAPPED,
        uc_emu_start(uc, code_start, code_start + sizeof(code) - 1, 0, 0));

    OK(uc_close(uc));
}

static void test_x86_invalid_jump()
{
    uc_engine *uc;
    char code[] = "\xe9\xe9\xee\xee\xee"; // jmp 0xEEEEEEEE

    uc_common_setup(&uc, UC_ARCH_X86, UC_MODE_32, code, sizeof(code) - 1);

    uc_assert_err(
        UC_ERR_FETCH_UNMAPPED,
        uc_emu_start(uc, code_start, code_start + sizeof(code) - 1, 0, 0));

    OK(uc_close(uc));
}

static void test_x86_64_syscall_callback(uc_engine *uc, void *user_data)
{
    uint64_t rax;

    OK(uc_reg_read(uc, UC_X86_REG_RAX, &rax));

    TEST_CHECK(rax == 0x100);
}

static void test_x86_64_syscall()
{
    uc_engine *uc;
    uc_hook hook;
    char code[] = "\x0f\x05"; // syscall
    uint64_t r_rax = 0x100;

    uc_common_setup(&uc, UC_ARCH_X86, UC_MODE_64, code, sizeof(code) - 1);
    OK(uc_reg_write(uc, UC_X86_REG_RAX, &r_rax));
    OK(uc_hook_add(uc, &hook, UC_HOOK_INSN, test_x86_64_syscall_callback, NULL,
                   1, 0, UC_X86_INS_SYSCALL));

    OK(uc_emu_start(uc, code_start, code_start + sizeof(code) - 1, 0, 0));

    OK(uc_hook_del(uc, hook));
    OK(uc_close(uc));
}

static void test_x86_16_add()
{
    uc_engine *uc;
    char code[] = "\x00\x00"; // add   byte ptr [bx + si], al
    uint16_t r_ax = 7;
    uint16_t r_bx = 5;
    uint16_t r_si = 6;
    uint8_t result;

    uc_common_setup(&uc, UC_ARCH_X86, UC_MODE_16, code, sizeof(code) - 1);
    OK(uc_mem_map(uc, 0, 0x1000, UC_PROT_ALL));
    OK(uc_reg_write(uc, UC_X86_REG_AX, &r_ax));
    OK(uc_reg_write(uc, UC_X86_REG_BX, &r_bx));
    OK(uc_reg_write(uc, UC_X86_REG_SI, &r_si));

    OK(uc_emu_start(uc, code_start, code_start + sizeof(code) - 1, 0, 0));

    OK(uc_mem_read(uc, r_bx + r_si, &result, 1));
    TEST_CHECK(result == 7);
    OK(uc_close(uc));
}

static void test_x86_reg_save()
{
    uc_engine *uc;
    uc_context *ctx;
    char code[] = "\x40"; // inc eax
    int r_eax = 1;

    uc_common_setup(&uc, UC_ARCH_X86, UC_MODE_32, code, sizeof(code) - 1);
    OK(uc_reg_write(uc, UC_X86_REG_EAX, &r_eax));

    OK(uc_context_alloc(uc, &ctx));
    OK(uc_context_save(uc, ctx));
    OK(uc_emu_start(uc, code_start, code_start + sizeof(code) - 1, 0, 0));

    OK(uc_reg_read(uc, UC_X86_REG_EAX, &r_eax));
    TEST_CHECK(r_eax == 2);

    OK(uc_context_restore(uc, ctx));

    OK(uc_reg_read(uc, UC_X86_REG_EAX, &r_eax));
    TEST_CHECK(r_eax == 1);

    OK(uc_context_free(ctx));
    OK(uc_close(uc));
}

static bool
test_x86_invalid_mem_read_stop_in_cb_callback(uc_engine *uc, uc_mem_type type,
                                              uint64_t address, int size,
                                              uint64_t value, void *user_data)
{
    // False indicates that we fail to handle this ERROR and let the emulation
    // stop.
    //
    // Note that the memory must be mapped properly if we return true! Check
    // test_x86_mem_hook_all for example.
    return false;
}

static void test_x86_invalid_mem_read_stop_in_cb()
{
    uc_engine *uc;
    uc_hook hook;
    char code[] = "\x40\x8b\x1d\x00\x00\x10\x00\x42"; // inc eax; mov ebx,
                                                      // [0x100000]; inc edx
    int r_eax = 0x1234;
    int r_edx = 0x5678;
    int r_eip = 0;

    uc_common_setup(&uc, UC_ARCH_X86, UC_MODE_32, code, sizeof(code) - 1);
    OK(uc_hook_add(uc, &hook, UC_HOOK_MEM_READ,
                   test_x86_invalid_mem_read_stop_in_cb_callback, NULL, 1, 0));
    OK(uc_reg_write(uc, UC_X86_REG_EAX, &r_eax));
    OK(uc_reg_write(uc, UC_X86_REG_EDX, &r_edx));

    uc_assert_err(
        UC_ERR_READ_UNMAPPED,
        uc_emu_start(uc, code_start, code_start + sizeof(code) - 1, 0, 0));

    // The state of Unicorn should be correct at this time.
    OK(uc_reg_read(uc, UC_X86_REG_EIP, &r_eip));
    OK(uc_reg_read(uc, UC_X86_REG_EAX, &r_eax));
    OK(uc_reg_read(uc, UC_X86_REG_EDX, &r_edx));

    TEST_CHECK(r_eip == code_start + 1);
    TEST_CHECK(r_eax == 0x1235);
    TEST_CHECK(r_edx == 0x5678);

    OK(uc_close(uc));
}

static void test_x86_x87_fnstenv_callback(uc_engine *uc, uint64_t address,
                                          uint32_t size, void *user_data)
{
    uint32_t r_eip;
    uint32_t r_eax;
    uint32_t fnstenv[7];

    if (address == code_start + 4) { // The first fnstenv executed
        // Save the address of the fld.
        OK(uc_reg_read(uc, UC_X86_REG_EIP, &r_eip));
        *((uint32_t *)user_data) = r_eip;

        OK(uc_reg_read(uc, UC_X86_REG_EAX, &r_eax));
        OK(uc_mem_read(uc, r_eax, fnstenv, sizeof(fnstenv)));
        // Don't update FCS:FIP for fnop.
        TEST_CHECK(fnstenv[3] == 0);
    }
}

static void test_x86_x87_fnstenv()
{
    uc_engine *uc;
    uc_hook hook;
    char code[] =
        "\xd9\xd0\xd9\x30\xd9\x00\xd9\x30"; // fnop;fnstenv [eax];fld dword ptr
                                            // [eax];fnstenv [eax]
    uint32_t base = code_start + 3 * code_len;
    uint32_t last_eip;
    uint32_t fnstenv[7];

    uc_common_setup(&uc, UC_ARCH_X86, UC_MODE_32, code, sizeof(code) - 1);
    OK(uc_mem_map(uc, base, code_len, UC_PROT_ALL));
    OK(uc_reg_write(uc, UC_X86_REG_EAX, &base));

    OK(uc_hook_add(uc, &hook, UC_HOOK_CODE, test_x86_x87_fnstenv_callback,
                   &last_eip, 1, 0));

    OK(uc_emu_start(uc, code_start, code_start + sizeof(code) - 1, 0, 0));

    OK(uc_mem_read(uc, base, fnstenv, sizeof(fnstenv)));
    // But update FCS:FIP for fld.
    TEST_CHECK(fnstenv[3] == last_eip);

    OK(uc_close(uc));
}

static uint64_t test_x86_mmio_read_callback(uc_engine *uc, uint64_t offset,
                                            unsigned size, void *user_data)
{
    TEST_CHECK(offset == 4);
    TEST_CHECK(size == 4);

    return 0x19260817;
}

static void test_x86_mmio_write_callback(uc_engine *uc, uint64_t offset,
                                         unsigned size, uint64_t value,
                                         void *user_data)
{
    TEST_CHECK(offset == 4);
    TEST_CHECK(size == 4);
    TEST_CHECK(value == 0xdeadbeef);

    return;
}

static void test_x86_mmio()
{
    uc_engine *uc;
    int r_ecx = 0xdeadbeef;
    char code[] =
        "\x89\x0d\x04\x00\x02\x00\x8b\x0d\x04\x00\x02\x00"; // mov [0x20004],
                                                            // ecx; mov ecx,
                                                            // [0x20004]

    uc_common_setup(&uc, UC_ARCH_X86, UC_MODE_32, code, sizeof(code) - 1);
    OK(uc_reg_write(uc, UC_X86_REG_ECX, &r_ecx));
    OK(uc_mmio_map(uc, 0x20000, 0x1000, test_x86_mmio_read_callback, NULL,
                   test_x86_mmio_write_callback, NULL));

    OK(uc_emu_start(uc, code_start, code_start + sizeof(code) - 1, 0, 0));

    OK(uc_reg_read(uc, UC_X86_REG_ECX, &r_ecx));

    TEST_CHECK(r_ecx == 0x19260817);

    OK(uc_close(uc));
}

static bool test_x86_missing_code_callback(uc_engine *uc, uc_mem_type type,
                                           uint64_t address, int size,
                                           uint64_t value, void *user_data)
{
    char code[] = "\x41\x4a"; // inc ecx; dec edx;
    uint64_t algined_address = address & 0xFFFFFFFFFFFFF000ULL;
    int aligned_size = ((int)(size / 0x1000) + 1) * 0x1000;

    OK(uc_mem_map(uc, algined_address, aligned_size, UC_PROT_ALL));

    OK(uc_mem_write(uc, algined_address, code, sizeof(code) - 1));

    return true;
}

static void test_x86_missing_code()
{
    uc_engine *uc;
    uc_hook hook;
    int r_ecx = 0x1234;
    int r_edx = 0x7890;

    // Don't write any code by design.
    OK(uc_open(UC_ARCH_X86, UC_MODE_32, &uc));
    OK(uc_reg_write(uc, UC_X86_REG_ECX, &r_ecx));
    OK(uc_reg_write(uc, UC_X86_REG_EDX, &r_edx));
    OK(uc_hook_add(uc, &hook, UC_HOOK_MEM_UNMAPPED,
                   test_x86_missing_code_callback, NULL, 1, 0));

    OK(uc_emu_start(uc, code_start, code_start + 2, 0, 0));

    OK(uc_reg_read(uc, UC_X86_REG_ECX, &r_ecx));
    OK(uc_reg_read(uc, UC_X86_REG_EDX, &r_edx));

    TEST_CHECK(r_ecx == 0x1235);
    TEST_CHECK(r_edx == 0x788f);

    OK(uc_close(uc));
}

static void test_x86_smc_xor()
{
    uc_engine *uc;
    /*
     * 0x1000 xor dword ptr [edi+0x3], eax ; edi=0x1000, eax=0xbc4177e6
     * 0x1003 dw 0x3ea98b13
     */
    char code[] = "\x31\x47\x03\x13\x8b\xa9\x3e";
    int r_edi = code_start;
    int r_eax = 0xbc4177e6;
    uint32_t result;

    uc_common_setup(&uc, UC_ARCH_X86, UC_MODE_32, code, sizeof(code) - 1);
    uc_reg_write(uc, UC_X86_REG_EDI, &r_edi);
    uc_reg_write(uc, UC_X86_REG_EAX, &r_eax);

    OK(uc_emu_start(uc, code_start, code_start + 3, 0, 0));

    OK(uc_mem_read(uc, code_start + 3, (void *)&result, 4));

    TEST_CHECK(result == (0x3ea98b13 ^ 0xbc4177e6));

    OK(uc_close(uc));
}

static uint64_t test_x86_mmio_uc_mem_rw_read_callback(uc_engine *uc,
                                                      uint64_t offset,
                                                      unsigned size,
                                                      void *user_data)
{
    TEST_CHECK(offset == 8);
    TEST_CHECK(size == 4);

    return 0x19260817;
}

static void test_x86_mmio_uc_mem_rw_write_callback(uc_engine *uc,
                                                   uint64_t offset,
                                                   unsigned size,
                                                   uint64_t value,
                                                   void *user_data)
{
    TEST_CHECK(offset == 4);
    TEST_CHECK(size == 4);
    TEST_CHECK(value == 0xdeadbeef);

    return;
}

static void test_x86_mmio_uc_mem_rw()
{
    uc_engine *uc;
    int data = 0xdeadbeef;

    OK(uc_open(UC_ARCH_X86, UC_MODE_32, &uc));

    OK(uc_mmio_map(uc, 0x20000, 0x1000, test_x86_mmio_uc_mem_rw_read_callback,
                   NULL, test_x86_mmio_uc_mem_rw_write_callback, NULL));

    OK(uc_mem_write(uc, 0x20004, (void *)&data, 4));
    OK(uc_mem_read(uc, 0x20008, (void *)&data, 4));

    TEST_CHECK(data == 0x19260817);

    OK(uc_close(uc));
}

static void test_x86_sysenter_hook(uc_engine *uc, void *user)
{
    *(int *)user = 1;
}

static void test_x86_sysenter()
{
    uc_engine *uc;
    char code[] = "\x0F\x34"; // sysenter
    uc_hook h;
    int called = 0;

    uc_common_setup(&uc, UC_ARCH_X86, UC_MODE_32, code, sizeof(code) - 1);

    OK(uc_hook_add(uc, &h, UC_HOOK_INSN, test_x86_sysenter_hook, &called, 1, 0,
                   UC_X86_INS_SYSENTER));

    OK(uc_emu_start(uc, code_start, code_start + sizeof(code) - 1, 0, 0));

    TEST_CHECK(called == 1);

    OK(uc_close(uc));
}

static void test_x86_hook_cpuid_callback(uc_engine *uc, void *data)
{
    int reg = 7;

    OK(uc_reg_write(uc, UC_X86_REG_EAX, &reg));
}

static void test_x86_hook_cpuid()
{
    uc_engine *uc;
    char code[] = "\x40\x0F\xA2"; // INC EAX; CPUID
    uc_hook h;
    int reg;

    uc_common_setup(&uc, UC_ARCH_X86, UC_MODE_32, code, sizeof(code) - 1);

    OK(uc_hook_add(uc, &h, UC_HOOK_INSN, test_x86_hook_cpuid_callback, NULL, 1,
                   0, UC_X86_INS_CPUID));

    OK(uc_emu_start(uc, code_start, code_start + sizeof(code) - 1, 0, 0));

    OK(uc_reg_read(uc, UC_X86_REG_EAX, &reg));

    TEST_CHECK(reg == 7);

    OK(uc_close(uc));
}

// This is a regression bug.
static void test_x86_clear_tb_cache()
{
    uc_engine *uc;
    char code[] = "\x83\xc1\x01\x4a"; // ADD ecx, 1; DEC edx;
    int r_ecx = 0x1234;
    int r_edx = 0x7890;
    uint64_t code_start = 0x1240; // Choose this address by design
    uint64_t code_len = 0x1000;

    OK(uc_open(UC_ARCH_X86, UC_MODE_32, &uc));
    OK(uc_mem_map(uc, code_start & (1 << 12), code_len, UC_PROT_ALL));
    OK(uc_mem_write(uc, code_start, code, sizeof(code)));
    OK(uc_reg_write(uc, UC_X86_REG_ECX, &r_ecx));
    OK(uc_reg_write(uc, UC_X86_REG_EDX, &r_edx));

    // This emulation should take no effect at all.
    OK(uc_emu_start(uc, code_start, code_start, 0, 0));

    // Emulate ADD ecx, 1.
    OK(uc_emu_start(uc, code_start, code_start + 3, 0, 0));

    // If tb cache is not cleared, edx would be still 0x7890
    OK(uc_emu_start(uc, code_start, code_start + sizeof(code) - 1, 0, 0));

    OK(uc_reg_read(uc, UC_X86_REG_ECX, &r_ecx));
    OK(uc_reg_read(uc, UC_X86_REG_EDX, &r_edx));

    TEST_CHECK(r_ecx == 0x1236);
    TEST_CHECK(r_edx == 0x788f);

    OK(uc_close(uc));
}

// This is a regression bug.
static void test_x86_clear_empty_tb()
{
    uc_engine *uc;
    // lb:
    //    add ecx, 1;
    //    cmp ecx, 0;
    //    jz lb;
    //    dec edx;
    char code[] = "\x83\xc1\x01\x83\xf9\x00\x74\xf8\x4a";
    int r_edx = 0x7890;
    uint64_t code_start = 0x1240; // Choose this address by design
    uint64_t code_len = 0x1000;

    OK(uc_open(UC_ARCH_X86, UC_MODE_32, &uc));
    OK(uc_mem_map(uc, code_start & (1 << 12), code_len, UC_PROT_ALL));
    OK(uc_mem_write(uc, code_start, code, sizeof(code)));
    OK(uc_reg_write(uc, UC_X86_REG_EDX, &r_edx));

    // Make sure we generate an empty tb at the exit address by stopping at dec
    // edx.
    OK(uc_emu_start(uc, code_start, code_start + 8, 0, 0));

    // If tb cache is not cleared, edx would be still 0x7890
    OK(uc_emu_start(uc, code_start, code_start + sizeof(code) - 1, 0, 0));

    OK(uc_reg_read(uc, UC_X86_REG_EDX, &r_edx));

    TEST_CHECK(r_edx == 0x788f);

    OK(uc_close(uc));
}

TEST_LIST = {{"test_x86_in", test_x86_in},
             {"test_x86_out", test_x86_out},
             {"test_x86_mem_hook_all", test_x86_mem_hook_all},
             {"test_x86_inc_dec_pxor", test_x86_inc_dec_pxor},
             {"test_x86_relative_jump", test_x86_relative_jump},
             {"test_x86_loop", test_x86_loop},
             {"test_x86_invalid_mem_read", test_x86_invalid_mem_read},
             {"test_x86_invalid_mem_write", test_x86_invalid_mem_write},
             {"test_x86_invalid_jump", test_x86_invalid_jump},
             {"test_x86_64_syscall", test_x86_64_syscall},
             {"test_x86_16_add", test_x86_16_add},
             {"test_x86_reg_save", test_x86_reg_save},
             {"test_x86_invalid_mem_read_stop_in_cb",
              test_x86_invalid_mem_read_stop_in_cb},
             {"test_x86_x87_fnstenv", test_x86_x87_fnstenv},
             {"test_x86_mmio", test_x86_mmio},
             {"test_x86_missing_code", test_x86_missing_code},
             {"test_x86_smc_xor", test_x86_smc_xor},
             {"test_x86_mmio_uc_mem_rw", test_x86_mmio_uc_mem_rw},
             {"test_x86_sysenter", test_x86_sysenter},
             {"test_x86_hook_cpuid", test_x86_hook_cpuid},
             {"test_x86_clear_tb_cache", test_x86_clear_tb_cache},
             {"test_x86_clear_empty_tb", test_x86_clear_empty_tb},
             {NULL, NULL}};