xref: /kvm-unit-tests/x86/realmode.c (revision c60618175f490cabc61e4bc0759ca806df432d80)

asm(".code16gcc");

typedef unsigned char u8;
typedef unsigned short u16;
typedef unsigned u32;
typedef unsigned long long u64;

void test_function(void);

asm(
	"test_function: \n\t"
	"mov $0x1234, %eax \n\t"
	"ret"
   );

static int strlen(const char *str)
{
	int n;

	for (n = 0; *str; ++str)
		++n;
	return n;
}

static void print_serial(const char *buf)
{
	unsigned long len = strlen(buf);

	asm volatile ("cld; addr32/rep/outsb" : "+S"(buf), "+c"(len) : "d"(0xf1));
}

static void exit(int code)
{
        asm volatile("out %0, %1" : : "a"(code), "d"((short)0xf4));
}

struct regs {
	u32 eax, ebx, ecx, edx;
	u32 esi, edi, esp, ebp;
	u32 eip, eflags;
};

static u64 gdt[] = {
	0,
	0x00cf9b000000ffffull, // flat 32-bit code segment
	0x00cf93000000ffffull, // flat 32-bit data segment
};

static struct {
	u16 limit;
	void *base;
} __attribute__((packed)) gdt_descr = {
	sizeof(gdt) - 1,
	gdt,
};

static void exec_in_big_real_mode(const struct regs *inregs,
				  struct regs *outregs,
				  const u8 *insn, int insn_len)
{
	unsigned long tmp;
	static struct regs save;
	int i;
	extern u8 test_insn[], test_insn_end[];

	for (i = 0; i < insn_len; ++i)
		test_insn[i] = insn[i];
	for (; i < test_insn_end - test_insn; ++i)
		test_insn[i] = 0x90; // nop

	save = *inregs;
	asm volatile(
		"lgdtl %[gdt_descr] \n\t"
		"mov %%cr0, %[tmp] \n\t"
		"or $1, %[tmp] \n\t"
		"mov %[tmp], %%cr0 \n\t"
		"mov %[bigseg], %%gs \n\t"
		"and $-2, %[tmp] \n\t"
		"mov %[tmp], %%cr0 \n\t"

                "pushw %[save]+36; popfw \n\t"
		"xchg %%eax, %[save]+0 \n\t"
		"xchg %%ebx, %[save]+4 \n\t"
		"xchg %%ecx, %[save]+8 \n\t"
		"xchg %%edx, %[save]+12 \n\t"
		"xchg %%esi, %[save]+16 \n\t"
		"xchg %%edi, %[save]+20 \n\t"
		"xchg %%esp, %[save]+24 \n\t"
		"xchg %%ebp, %[save]+28 \n\t"

		"test_insn: . = . + 32\n\t"
		"test_insn_end: \n\t"

		"xchg %%eax, %[save]+0 \n\t"
		"xchg %%ebx, %[save]+4 \n\t"
		"xchg %%ecx, %[save]+8 \n\t"
		"xchg %%edx, %[save]+12 \n\t"
		"xchg %%esi, %[save]+16 \n\t"
		"xchg %%edi, %[save]+20 \n\t"
		"xchg %%esp, %[save]+24 \n\t"
		"xchg %%ebp, %[save]+28 \n\t"

		/* Save EFLAGS in outregs*/
		"pushfl \n\t"
		"popl %[save]+36 \n\t"

		"xor %[tmp], %[tmp] \n\t"
		"mov %[tmp], %%gs \n\t"
		: [tmp]"=&r"(tmp), [save]"+m"(save)
		: [gdt_descr]"m"(gdt_descr), [bigseg]"r"((short)16)
		: "cc", "memory"
		);
	*outregs = save;
}

#define R_AX 1
#define R_BX 2
#define R_CX 4
#define R_DX 8
#define R_SI 16
#define R_DI 32
#define R_SP 64
#define R_BP 128

int regs_equal(const struct regs *r1, const struct regs *r2, int ignore)
{
	const u32 *p1 = &r1->eax, *p2 = &r2->eax;  // yuck
	int i;

	for (i = 0; i < 8; ++i)
		if (!(ignore & (1 << i)) && p1[i] != p2[i])
			return 0;
	return 1;
}

#define MK_INSN(name, str)                         \
	asm (				           \
		".text 1\n\t"                      \
		"insn_" #name ": " str " \n\t"	   \
		"insn_" #name "_end: \n\t"	   \
		".text\n\t"                        \
		);				   \
	extern u8 insn_##name[], insn_##name##_end[]

void test_xchg(void)
{
	struct regs inregs = { .eax = 0, .ebx = 1, .ecx = 2, .edx = 3, .esi = 4, .edi = 5, .ebp = 6, .esp = 7}, outregs;

	MK_INSN(xchg_test1, "xchg %eax,%eax\n\t");
	MK_INSN(xchg_test2, "xchg %eax,%ebx\n\t");
	MK_INSN(xchg_test3, "xchg %eax,%ecx\n\t");
	MK_INSN(xchg_test4, "xchg %eax,%edx\n\t");
	MK_INSN(xchg_test5, "xchg %eax,%esi\n\t");
	MK_INSN(xchg_test6, "xchg %eax,%edi\n\t");
	MK_INSN(xchg_test7, "xchg %eax,%ebp\n\t");
	MK_INSN(xchg_test8, "xchg %eax,%esp\n\t");

	exec_in_big_real_mode(&inregs, &outregs,
			      insn_xchg_test1,
                              insn_xchg_test1_end - insn_xchg_test1);

	if (!regs_equal(&inregs, &outregs, 0))
		print_serial("xchg test 1: FAIL\n");
	else
		print_serial("xchg test 1: PASS\n");

	exec_in_big_real_mode(&inregs, &outregs,
			      insn_xchg_test2,
                              insn_xchg_test2_end - insn_xchg_test2);

	if (!regs_equal(&inregs, &outregs, R_AX | R_BX) ||
            outregs.eax != inregs.ebx ||
            outregs.ebx != inregs.eax)
		print_serial("xchg test 2: FAIL\n");
	else
		print_serial("xchg test 2: PASS\n");

	exec_in_big_real_mode(&inregs, &outregs,
			      insn_xchg_test3,
                              insn_xchg_test3_end - insn_xchg_test3);

	if (!regs_equal(&inregs, &outregs, R_AX | R_CX) ||
            outregs.eax != inregs.ecx ||
            outregs.ecx != inregs.eax)
		print_serial("xchg test 3: FAIL\n");
	else
		print_serial("xchg test 3: PASS\n");

	exec_in_big_real_mode(&inregs, &outregs,
			      insn_xchg_test4,
                              insn_xchg_test4_end - insn_xchg_test4);

	if (!regs_equal(&inregs, &outregs, R_AX | R_DX) ||
            outregs.eax != inregs.edx ||
            outregs.edx != inregs.eax)
		print_serial("xchg test 4: FAIL\n");
	else
		print_serial("xchg test 4: PASS\n");

	exec_in_big_real_mode(&inregs, &outregs,
			      insn_xchg_test5,
                              insn_xchg_test5_end - insn_xchg_test5);

	if (!regs_equal(&inregs, &outregs, R_AX | R_SI) ||
            outregs.eax != inregs.esi ||
            outregs.esi != inregs.eax)
		print_serial("xchg test 5: FAIL\n");
	else
		print_serial("xchg test 5: PASS\n");

	exec_in_big_real_mode(&inregs, &outregs,
			      insn_xchg_test6,
                              insn_xchg_test6_end - insn_xchg_test6);

	if (!regs_equal(&inregs, &outregs, R_AX | R_DI) ||
            outregs.eax != inregs.edi ||
            outregs.edi != inregs.eax)
		print_serial("xchg test 6: FAIL\n");
	else
		print_serial("xchg test 6: PASS\n");

	exec_in_big_real_mode(&inregs, &outregs,
			      insn_xchg_test7,
                              insn_xchg_test7_end - insn_xchg_test7);

	if (!regs_equal(&inregs, &outregs, R_AX | R_BP) ||
            outregs.eax != inregs.ebp ||
            outregs.ebp != inregs.eax)
		print_serial("xchg test 7: FAIL\n");
	else
		print_serial("xchg test 7: PASS\n");

	exec_in_big_real_mode(&inregs, &outregs,
			      insn_xchg_test8,
                              insn_xchg_test8_end - insn_xchg_test8);

	if (!regs_equal(&inregs, &outregs, R_AX | R_SP) ||
            outregs.eax != inregs.esp ||
            outregs.esp != inregs.eax)
		print_serial("xchg test 8: FAIL\n");
	else
		print_serial("xchg test 8: PASS\n");
}

void test_shld(void)
{
	struct regs inregs = { .eax = 0xbe, .edx = 0xef000000 }, outregs;
	MK_INSN(shld_test, "shld $8,%edx,%eax\n\t");

	exec_in_big_real_mode(&inregs, &outregs,
			      insn_shld_test,
			      insn_shld_test_end - insn_shld_test);
	if (outregs.eax != 0xbeef)
		print_serial("shld: FAIL\n");
	else
		print_serial("shld: PASS\n");
}

void test_mov_imm(void)
{
	struct regs inregs = { 0 }, outregs;
	MK_INSN(mov_r32_imm_1, "mov $1234567890, %eax");
	MK_INSN(mov_r16_imm_1, "mov $1234, %ax");
	MK_INSN(mov_r8_imm_1, "mov $0x12, %ah");
	MK_INSN(mov_r8_imm_2, "mov $0x34, %al");
	MK_INSN(mov_r8_imm_3, "mov $0x12, %ah\n\t" "mov $0x34, %al\n\t");

	exec_in_big_real_mode(&inregs, &outregs,
			      insn_mov_r16_imm_1,
			      insn_mov_r16_imm_1_end - insn_mov_r16_imm_1);
	if (!regs_equal(&inregs, &outregs, R_AX) || outregs.eax != 1234)
		print_serial("mov test 1: FAIL\n");
	else
		print_serial("mov test 1: PASS\n");

	/* test mov $imm, %eax */
	exec_in_big_real_mode(&inregs, &outregs,
			      insn_mov_r32_imm_1,
			      insn_mov_r32_imm_1_end - insn_mov_r32_imm_1);
	if (!regs_equal(&inregs, &outregs, R_AX) || outregs.eax != 1234567890)
		print_serial("mov test 2: FAIL\n");
	else
		print_serial("mov test 2: PASS\n");

	/* test mov $imm, %al/%ah */
	exec_in_big_real_mode(&inregs, &outregs,
			      insn_mov_r8_imm_1,
			      insn_mov_r8_imm_1_end - insn_mov_r8_imm_1);
	if (!regs_equal(&inregs, &outregs, R_AX) || outregs.eax != 0x1200)
		print_serial("mov test 3: FAIL\n");
	else
		print_serial("mov test 3: PASS\n");

	exec_in_big_real_mode(&inregs, &outregs,
			      insn_mov_r8_imm_2,
			      insn_mov_r8_imm_2_end - insn_mov_r8_imm_2);
	if (!regs_equal(&inregs, &outregs, R_AX) || outregs.eax != 0x34)
		print_serial("mov test 4: FAIL\n");
	else
		print_serial("mov test 4: PASS\n");

	exec_in_big_real_mode(&inregs, &outregs,
			      insn_mov_r8_imm_3,
			      insn_mov_r8_imm_3_end - insn_mov_r8_imm_3);
	if (!regs_equal(&inregs, &outregs, R_AX) || outregs.eax != 0x1234)
		print_serial("mov test 5: FAIL\n");
	else
		print_serial("mov test 5: PASS\n");
}

void test_sub_imm(void)
{
	struct regs inregs = { 0 }, outregs;
	MK_INSN(sub_r32_imm_1, "mov $1234567890, %eax\n\t" "sub $10, %eax\n\t");
	MK_INSN(sub_r16_imm_1, "mov $1234, %ax\n\t" "sub $10, %ax\n\t");
	MK_INSN(sub_r8_imm_1, "mov $0x12, %ah\n\t" "sub $0x10, %ah\n\t");
	MK_INSN(sub_r8_imm_2, "mov $0x34, %al\n\t" "sub $0x10, %al\n\t");

	exec_in_big_real_mode(&inregs, &outregs,
			      insn_sub_r16_imm_1,
			      insn_sub_r16_imm_1_end - insn_sub_r16_imm_1);
	if (!regs_equal(&inregs, &outregs, R_AX) || outregs.eax != 1224)
		print_serial("sub test 1: FAIL\n");
	else
		print_serial("sub test 1: PASS\n");

	/* test mov $imm, %eax */
	exec_in_big_real_mode(&inregs, &outregs,
			      insn_sub_r32_imm_1,
			      insn_sub_r32_imm_1_end - insn_sub_r32_imm_1);
	if (!regs_equal(&inregs, &outregs, R_AX) || outregs.eax != 1234567880)
		print_serial("sub test 2: FAIL\n");
	else
		print_serial("sub test 2: PASS\n");

	/* test mov $imm, %al/%ah */
	exec_in_big_real_mode(&inregs, &outregs,
			      insn_sub_r8_imm_1,
			      insn_sub_r8_imm_1_end - insn_sub_r8_imm_1);
	if (!regs_equal(&inregs, &outregs, R_AX) || outregs.eax != 0x0200)
		print_serial("sub test 3: FAIL\n");
	else
		print_serial("sub test 3: PASS\n");

	exec_in_big_real_mode(&inregs, &outregs,
			      insn_sub_r8_imm_2,
			      insn_sub_r8_imm_2_end - insn_sub_r8_imm_2);
	if (!regs_equal(&inregs, &outregs, R_AX) || outregs.eax != 0x24)
		print_serial("sub test 4: FAIL\n");
	else
		print_serial("sub test 4: PASS\n");
}


void test_xor_imm(void)
{
	struct regs inregs = { 0 }, outregs;
	MK_INSN(xor_r32_imm_1, "mov $1234567890, %eax\n\t" "xor $1234567890, %eax\n\t");
	MK_INSN(xor_r16_imm_1, "mov $1234, %ax\n\t" "xor $1234, %ax\n\t");
	MK_INSN(xor_r8_imm_1, "mov $0x12, %ah\n\t" "xor $0x12, %ah\n\t");
	MK_INSN(xor_r8_imm_2, "mov $0x34, %al\n\t" "xor $0x34, %al\n\t");

	exec_in_big_real_mode(&inregs, &outregs,
			      insn_xor_r16_imm_1,
			      insn_xor_r16_imm_1_end - insn_xor_r16_imm_1);
	if (!regs_equal(&inregs, &outregs, R_AX) || outregs.eax != 0)
		print_serial("xor test 1: FAIL\n");
	else
		print_serial("xor test 1: PASS\n");

	/* test mov $imm, %eax */
	exec_in_big_real_mode(&inregs, &outregs,
			      insn_xor_r32_imm_1,
			      insn_xor_r32_imm_1_end - insn_xor_r32_imm_1);
	if (!regs_equal(&inregs, &outregs, R_AX) || outregs.eax != 0)
		print_serial("xor test 2: FAIL\n");
	else
		print_serial("xor test 2: PASS\n");

	/* test mov $imm, %al/%ah */
	exec_in_big_real_mode(&inregs, &outregs,
			      insn_xor_r8_imm_1,
			      insn_xor_r8_imm_1_end - insn_xor_r8_imm_1);
	if (!regs_equal(&inregs, &outregs, R_AX) || outregs.eax != 0)
		print_serial("xor test 3: FAIL\n");
	else
		print_serial("xor test 3: PASS\n");

	exec_in_big_real_mode(&inregs, &outregs,
			      insn_xor_r8_imm_2,
			      insn_xor_r8_imm_2_end - insn_xor_r8_imm_2);
	if (!regs_equal(&inregs, &outregs, R_AX) || outregs.eax != 0)
		print_serial("xor test 4: FAIL\n");
	else
		print_serial("xor test 4: PASS\n");
}

void test_cmp_imm(void)
{
	struct regs inregs = { 0 }, outregs;
	MK_INSN(cmp_test1, "mov $0x34, %al\n\t"
			   "cmp $0x34, %al\n\t");
	MK_INSN(cmp_test2, "mov $0x34, %al\n\t"
			   "cmp $0x39, %al\n\t");
	MK_INSN(cmp_test3, "mov $0x34, %al\n\t"
			   "cmp $0x24, %al\n\t");

	/* test cmp imm8 with AL */
	/* ZF: (bit 6) Zero Flag becomes 1 if an operation results
	 * in a 0 writeback, or 0 register
	 */
	exec_in_big_real_mode(&inregs, &outregs,
			      insn_cmp_test1,
			      insn_cmp_test1_end - insn_cmp_test1);
	if ((outregs.eflags & (1<<6)) != (1<<6))
		print_serial("cmp test 1: FAIL\n");
	else
		print_serial("cmp test 1: PASS\n");

	exec_in_big_real_mode(&inregs, &outregs,
			      insn_cmp_test2,
			      insn_cmp_test2_end - insn_cmp_test2);
	if ((outregs.eflags & (1<<6)) != 0)
		print_serial("cmp test 2: FAIL\n");
	else
		print_serial("cmp test 2: PASS\n");

	exec_in_big_real_mode(&inregs, &outregs,
			      insn_cmp_test3,
			      insn_cmp_test3_end - insn_cmp_test3);
	if ((outregs.eflags & (1<<6)) != 0)
		print_serial("cmp test 3: FAIL\n");
	else
		print_serial("cmp test 3: PASS\n");
}

void test_add_imm(void)
{
	struct regs inregs = { 0 }, outregs;
	MK_INSN(add_test1, "mov $0x43211234, %eax \n\t"
			   "add $0x12344321, %eax \n\t");
	MK_INSN(add_test2, "mov $0x12, %eax \n\t"
			   "add $0x21, %al\n\t");

	exec_in_big_real_mode(&inregs, &outregs,
			      insn_add_test1,
			      insn_add_test1_end - insn_add_test1);
	if (outregs.eax != 0x55555555)
		print_serial("add test 1: FAIL\n");
	else
		print_serial("add test 1: PASS\n");

	exec_in_big_real_mode(&inregs, &outregs,
			      insn_add_test2,
			      insn_add_test2_end - insn_add_test2);
	if (outregs.eax != 0x33)
		print_serial("add test 2: FAIL\n");
	else
		print_serial("add test 2: PASS\n");
}

void test_eflags_insn(void)
{
	struct regs inregs = { 0 }, outregs;
	MK_INSN(clc, "clc");
	MK_INSN(stc, "stc");
	MK_INSN(cli, "cli");
	MK_INSN(sti, "sti");
	MK_INSN(cld, "cld");
	MK_INSN(std, "std");

	exec_in_big_real_mode(&inregs, &outregs,
			      insn_clc,
			      insn_clc_end - insn_clc);
	if (outregs.eflags & 1)
		print_serial("clc test: FAIL\n");
	else
		print_serial("clc test: PASS\n");

	exec_in_big_real_mode(&inregs, &outregs,
			      insn_stc,
			      insn_stc_end - insn_stc);
	if (!(outregs.eflags & 1))
		print_serial("stc test: FAIL\n");
	else
		print_serial("stc test: PASS\n");

	exec_in_big_real_mode(&inregs, &outregs,
			      insn_cli,
			      insn_cli_end - insn_cli);
	if (outregs.eflags & (1 << 9))
		print_serial("cli test: FAIL\n");
	else
		print_serial("cli test: PASS\n");

	exec_in_big_real_mode(&inregs, &outregs,
			      insn_sti,
			      insn_sti_end - insn_sti);
	if (!(outregs.eflags & (1 << 9)))
		print_serial("sti test: FAIL\n");
	else
		print_serial("sti test: PASS\n");

	exec_in_big_real_mode(&inregs, &outregs,
			      insn_cld,
			      insn_cld_end - insn_cld);
	if (outregs.eflags & (1 << 10))
		print_serial("cld test: FAIL\n");
	else
		print_serial("cld test: PASS\n");

	exec_in_big_real_mode(&inregs, &outregs,
			      insn_std,
			      insn_std_end - insn_std);
	if (!(outregs.eflags & (1 << 10)))
		print_serial("std test: FAIL\n");
	else
		print_serial("std test: PASS\n");
}

void test_io(void)
{
	struct regs inregs = { 0 }, outregs;
	MK_INSN(io_test1, "mov $0xff, %al \n\t"
		          "out %al, $0xe0 \n\t"
		          "mov $0x00, %al \n\t"
			  "in $0xe0, %al \n\t");
	MK_INSN(io_test2, "mov $0xffff, %ax \n\t"
			  "out %ax, $0xe0 \n\t"
			  "mov $0x0000, %ax \n\t"
			  "in $0xe0, %ax \n\t");
	MK_INSN(io_test3, "mov $0xffffffff, %eax \n\t"
			  "out %eax, $0xe0 \n\t"
			  "mov $0x000000, %eax \n\t"
			  "in $0xe0, %eax \n\t");
	MK_INSN(io_test4, "mov $0xe0, %dx \n\t"
			  "mov $0xff, %al \n\t"
			  "out %al, %dx \n\t"
			  "mov $0x00, %al \n\t"
			  "in %dx, %al \n\t");
	MK_INSN(io_test5, "mov $0xe0, %dx \n\t"
			  "mov $0xffff, %ax \n\t"
			  "out %ax, %dx \n\t"
			  "mov $0x0000, %ax \n\t"
			  "in %dx, %ax \n\t");
	MK_INSN(io_test6, "mov $0xe0, %dx \n\t"
			  "mov $0xffffffff, %eax \n\t"
			  "out %eax, %dx \n\t"
			  "mov $0x00000000, %eax \n\t"
			  "in %dx, %eax \n\t");

	exec_in_big_real_mode(&inregs, &outregs,
			      insn_io_test1,
			      insn_io_test1_end - insn_io_test1);

	if (!regs_equal(&inregs, &outregs, R_AX) || outregs.eax != 0xff)
		print_serial("I/O test 1: FAIL\n");
	else
		print_serial("I/O test 1: PASS\n");

	exec_in_big_real_mode(&inregs, &outregs,
			      insn_io_test2,
			      insn_io_test2_end - insn_io_test2);

	if (!regs_equal(&inregs, &outregs, R_AX) || outregs.eax != 0xffff)
		print_serial("I/O test 2: FAIL\n");
	else
		print_serial("I/O test 2: PASS\n");

	exec_in_big_real_mode(&inregs, &outregs,
			      insn_io_test3,
			      insn_io_test3_end - insn_io_test3);

	if (!regs_equal(&inregs, &outregs, R_AX) || outregs.eax != 0xffffffff)
		print_serial("I/O test 3: FAIL\n");
	else
		print_serial("I/O test 3: PASS\n");

	exec_in_big_real_mode(&inregs, &outregs,
			      insn_io_test4,
			      insn_io_test4_end - insn_io_test4);

	if (!regs_equal(&inregs, &outregs, R_AX|R_DX) || outregs.eax != 0xff)
		print_serial("I/O test 4: FAIL\n");
	else
		print_serial("I/O test 4: PASS\n");

	exec_in_big_real_mode(&inregs, &outregs,
			      insn_io_test5,
			      insn_io_test5_end - insn_io_test5);

	if (!regs_equal(&inregs, &outregs, R_AX|R_DX) || outregs.eax != 0xffff)
		print_serial("I/O test 5: FAIL\n");
	else
		print_serial("I/O test 5: PASS\n");

	exec_in_big_real_mode(&inregs, &outregs,
			      insn_io_test6,
			      insn_io_test6_end - insn_io_test6);

	if (!regs_equal(&inregs, &outregs, R_AX|R_DX) || outregs.eax != 0xffffffff)
		print_serial("I/O test 6: FAIL\n");
	else
		print_serial("I/O test 6: PASS\n");
}

asm ("retf: lretw");
extern void retf();

void test_call(void)
{
	struct regs inregs = { 0 }, outregs;
	u32 esp[16];
	u32 addr;

	inregs.esp = (u32)esp;

	MK_INSN(call1, "mov $test_function, %eax \n\t"
		       "call *%eax\n\t");
	MK_INSN(call_near1, "jmp 2f\n\t"
			    "1: mov $0x1234, %eax\n\t"
			    "ret\n\t"
			    "2: call 1b\t");
	MK_INSN(call_near2, "call 1f\n\t"
			    "jmp 2f\n\t"
			    "1: mov $0x1234, %eax\n\t"
			    "ret\n\t"
			    "2:\t");
	MK_INSN(call_far1,  "lcallw *(%ebx)\n\t");
	MK_INSN(ret_imm,    "sub $10, %sp; jmp 2f; 1: retw $10; 2: callw 1b");

	exec_in_big_real_mode(&inregs, &outregs,
			      insn_call1,
			      insn_call1_end - insn_call1);
	if(!regs_equal(&inregs, &outregs, R_AX) || outregs.eax != 0x1234)
		print_serial("Call Test 1: FAIL\n");
	else
		print_serial("Call Test 1: PASS\n");

	exec_in_big_real_mode(&inregs, &outregs,
			insn_call_near1, insn_call_near1_end - insn_call_near1);
	if(!regs_equal(&inregs, &outregs, R_AX) || outregs.eax != 0x1234)
		print_serial("Call near Test 1: FAIL\n");
	else
		print_serial("Call near Test 1: PASS\n");

	exec_in_big_real_mode(&inregs, &outregs,
			insn_call_near2, insn_call_near2_end - insn_call_near2);
	if(!regs_equal(&inregs, &outregs, R_AX) || outregs.eax != 0x1234)
		print_serial("Call near Test 2: FAIL\n");
	else
		print_serial("Call near Test 2: PASS\n");

	addr = (((unsigned)retf >> 4) << 16) | ((unsigned)retf & 0x0f);
	inregs.ebx = (unsigned)&addr;
	exec_in_big_real_mode(&inregs, &outregs, insn_call_far1,
			      insn_call_far1_end - insn_call_far1);
	if (!regs_equal(&inregs, &outregs, 0))
		print_serial("Call far Test 1: FAIL\n");
	else
		print_serial("Call far Test 1: PASS\n");

	exec_in_big_real_mode(&inregs, &outregs, insn_ret_imm,
			      insn_ret_imm_end - insn_ret_imm);
	if (!regs_equal(&inregs, &outregs, 0))
		print_serial("ret imm Test 1: FAIL\n");
	else
		print_serial("ret imm Test 1: PASS\n");
}

void test_jcc_short(void)
{
	struct regs inregs = { 0 }, outregs;
	MK_INSN(jnz_short1, "jnz 1f\n\t"
			    "mov $0x1234, %eax\n\t"
		            "1:\n\t");
	MK_INSN(jnz_short2, "1:\n\t"
			    "cmp $0x1234, %eax\n\t"
			    "mov $0x1234, %eax\n\t"
		            "jnz 1b\n\t");
	MK_INSN(jmp_short1, "jmp 1f\n\t"
		      "mov $0x1234, %eax\n\t"
		      "1:\n\t");

	exec_in_big_real_mode(&inregs, &outregs,
			insn_jnz_short1, insn_jnz_short1_end - insn_jnz_short1);
	if(!regs_equal(&inregs, &outregs, 0))
		print_serial("JNZ short Test 1: FAIL\n");
	else
		print_serial("JNZ short Test 1: PASS\n");

	exec_in_big_real_mode(&inregs, &outregs,
			insn_jnz_short2, insn_jnz_short2_end - insn_jnz_short2);
	if(!regs_equal(&inregs, &outregs, R_AX) || !(outregs.eflags & (1 << 6)))
		print_serial("JNZ short Test 2: FAIL\n");
	else
		print_serial("JNZ short Test 2: PASS\n");

	exec_in_big_real_mode(&inregs, &outregs,
			insn_jmp_short1, insn_jmp_short1_end - insn_jmp_short1);
	if(!regs_equal(&inregs, &outregs, 0))
		print_serial("JMP short Test 1: FAIL\n");
	else
		print_serial("JMP short Test 1: PASS\n");
}

void test_jcc_near(void)
{
	struct regs inregs = { 0 }, outregs;
	/* encode near jmp manually. gas will not do it if offsets < 127 byte */
	MK_INSN(jnz_near1, ".byte 0x0f, 0x85, 0x06, 0x00\n\t"
		           "mov $0x1234, %eax\n\t");
	MK_INSN(jnz_near2, "cmp $0x1234, %eax\n\t"
			   "mov $0x1234, %eax\n\t"
		           ".byte 0x0f, 0x85, 0xf0, 0xff\n\t");
	MK_INSN(jmp_near1, ".byte 0xE9, 0x06, 0x00\n\t"
		           "mov $0x1234, %eax\n\t");

	exec_in_big_real_mode(&inregs, &outregs,
			insn_jnz_near1, insn_jnz_near1_end - insn_jnz_near1);
	if(!regs_equal(&inregs, &outregs, 0))
		print_serial("JNZ near Test 1: FAIL\n");
	else
		print_serial("JNZ near Test 1: PASS\n");

	exec_in_big_real_mode(&inregs, &outregs,
			insn_jnz_near2, insn_jnz_near2_end - insn_jnz_near2);
	if(!regs_equal(&inregs, &outregs, R_AX) || !(outregs.eflags & (1 << 6)))
		print_serial("JNZ near Test 2: FAIL\n");
	else
		print_serial("JNZ near Test 2: PASS\n");

	exec_in_big_real_mode(&inregs, &outregs,
			insn_jmp_near1, insn_jmp_near1_end - insn_jmp_near1);
	if(!regs_equal(&inregs, &outregs, 0))
		print_serial("JMP near Test 1: FAIL\n");
	else
		print_serial("JMP near Test 1: PASS\n");
}

void test_long_jmp()
{
	struct regs inregs = { 0 }, outregs;
	u32 esp[16];

	inregs.esp = (u32)esp;
	MK_INSN(long_jmp, "call 1f\n\t"
			  "jmp 2f\n\t"
			  "1: jmp $0, $test_function\n\t"
		          "2:\n\t");
	exec_in_big_real_mode(&inregs, &outregs,
			      insn_long_jmp,
			      insn_long_jmp_end - insn_long_jmp);
	if(!regs_equal(&inregs, &outregs, R_AX) || outregs.eax != 0x1234)
		print_serial("Long JMP Test: FAIL\n");
	else
		print_serial("Long JMP Test: PASS\n");
}

void test_push_pop()
{
	struct regs inregs = { 0 }, outregs;
	MK_INSN(push32, "mov $0x12345678, %eax\n\t"
			"push %eax\n\t"
			"pop %ebx\n\t");
	MK_INSN(push16, "mov $0x1234, %ax\n\t"
			"push %ax\n\t"
			"pop %bx\n\t");

	MK_INSN(push_es, "mov $0x231, %bx\n\t" //Just write a dummy value to see if it gets overwritten
			 "mov $0x123, %ax\n\t"
			 "mov %ax, %es\n\t"
			 "push %es\n\t"
			 "pop %bx \n\t"
			 );
	MK_INSN(pop_es, "push %ax\n\t"
			"pop %es\n\t"
			"mov %es, %bx\n\t"
			);
	MK_INSN(push_pop_ss, "push %ss\n\t"
			     "pushw %ax\n\t"
			     "popw %ss\n\t"
			     "mov %ss, %bx\n\t"
			     "pop %ss\n\t"
			);
	MK_INSN(push_pop_fs, "push %fs\n\t"
			     "pushl %eax\n\t"
			     "popl %fs\n\t"
			     "mov %fs, %ebx\n\t"
			     "pop %fs\n\t"
			);

	exec_in_big_real_mode(&inregs, &outregs,
			      insn_push32,
			      insn_push32_end - insn_push32);
	if (!regs_equal(&inregs, &outregs, R_AX|R_BX) || outregs.eax != outregs.ebx || outregs.eax != 0x12345678)
		print_serial("Push/Pop Test 1: FAIL\n");
	else
		print_serial("Push/Pop Test 1: PASS\n");

	exec_in_big_real_mode(&inregs, &outregs,
			      insn_push16,
			      insn_push16_end - insn_push16);

	if (!regs_equal(&inregs, &outregs, R_AX|R_BX) || outregs.eax != outregs.ebx || outregs.eax != 0x1234)
		print_serial("Push/Pop Test 2: FAIL\n");
	else
		print_serial("Push/Pop Test 2: PASS\n");

	exec_in_big_real_mode(&inregs, &outregs,
			      insn_push_es,
			      insn_push_es_end - insn_push_es);
	if (!regs_equal(&inregs, &outregs, R_AX|R_BX) ||  outregs.ebx != outregs.eax || outregs.eax != 0x123)
		print_serial("Push/Pop Test 3: FAIL\n");
	else
		print_serial("Push/Pop Test 3: PASS\n");

	exec_in_big_real_mode(&inregs, &outregs,
			      insn_pop_es,
			      insn_pop_es_end - insn_pop_es);

	if (!regs_equal(&inregs, &outregs, R_AX|R_BX) || outregs.ebx != outregs.eax)
		print_serial("Push/Pop Test 4: FAIL\n");
	else
		print_serial("Push/Pop Test 4: PASS\n");

	exec_in_big_real_mode(&inregs, &outregs,
			      insn_push_pop_ss,
			      insn_push_pop_ss_end - insn_push_pop_ss);

	if (!regs_equal(&inregs, &outregs, R_AX|R_BX) || outregs.ebx != outregs.eax)
		print_serial("Push/Pop Test 5: FAIL\n");
	else
		print_serial("Push/Pop Test 5: PASS\n");

	exec_in_big_real_mode(&inregs, &outregs,
			      insn_push_pop_fs,
			      insn_push_pop_fs_end - insn_push_pop_fs);

	if (!regs_equal(&inregs, &outregs, R_AX|R_BX) || outregs.ebx != outregs.eax)
		print_serial("Push/Pop Test 6: FAIL\n");
	else
		print_serial("Push/Pop Test 6: PASS\n");
}

void test_null(void)
{
	struct regs inregs = { 0 }, outregs;
	exec_in_big_real_mode(&inregs, &outregs, 0, 0);
	if (!regs_equal(&inregs, &outregs, 0))
		print_serial("null test: FAIL\n");
	else
		print_serial("null test: PASS\n");
}

struct {
    char stack[500];
    char top[];
} tmp_stack;

void test_pusha_popa()
{
	struct regs inregs = { .eax = 0, .ebx = 1, .ecx = 2, .edx = 3, .esi = 4, .edi = 5, .ebp = 6, .esp = (unsigned long)&tmp_stack.top }, outregs;

	MK_INSN(pusha, "pusha\n\t"
		       "pop %edi\n\t"
		       "pop %esi\n\t"
		       "pop %ebp\n\t"
		       "add $4, %esp\n\t"
		       "pop %ebx\n\t"
		       "pop %edx\n\t"
		       "pop %ecx\n\t"
		       "pop %eax\n\t"
		       );

	MK_INSN(popa, "push %eax\n\t"
		      "push %ecx\n\t"
		      "push %edx\n\t"
		      "push %ebx\n\t"
		      "push %esp\n\t"
		      "push %ebp\n\t"
		      "push %esi\n\t"
		      "push %edi\n\t"
		      "popa\n\t"
		      );

	exec_in_big_real_mode(&inregs, &outregs,
			      insn_pusha,
			      insn_pusha_end - insn_pusha);

	if (!regs_equal(&inregs, &outregs, 0))
		print_serial("Pusha/Popa Test1: FAIL\n");
	else
		print_serial("Pusha/Popa Test1: PASS\n");

	exec_in_big_real_mode(&inregs, &outregs,
			      insn_popa,
			      insn_popa_end - insn_popa);
	if (!regs_equal(&inregs, &outregs, 0))
		print_serial("Pusha/Popa Test2: FAIL\n");
	else
		print_serial("Pusha/Popa Test2: PASS\n");
}

void test_iret()
{
	struct regs inregs = { 0 }, outregs;

	MK_INSN(iret32, "pushf\n\t"
			"pushl %cs\n\t"
			"call 1f\n\t" /* a near call will push eip onto the stack */
			"jmp 2f\n\t"
			"1: iret\n\t"
			"2:\n\t"
		     );

	MK_INSN(iret16, "pushfw\n\t"
			"pushw %cs\n\t"
			"callw 1f\n\t"
			"jmp 2f\n\t"
			"1: iretw\n\t"
			"2:\n\t");

	MK_INSN(iret_flags32, "pushfl\n\t"
			      "popl %eax\n\t"
			      "andl $~0x2, %eax\n\t"
			      "orl $0xffc08028, %eax\n\t"
			      "pushl %eax\n\t"
			      "pushl %cs\n\t"
			      "call 1f\n\t"
			      "jmp 2f\n\t"
			      "1: iret\n\t"
			      "2:\n\t");

	MK_INSN(iret_flags16, "pushfw\n\t"
			      "popw %ax\n\t"
			      "and $~0x2, %ax\n\t"
			      "or $0x8028, %ax\n\t"
			      "pushw %ax\n\t"
			      "pushw %cs\n\t"
			      "callw 1f\n\t"
			      "jmp 2f\n\t"
			      "1: iretw\n\t"
			      "2:\n\t");

	exec_in_big_real_mode(&inregs, &outregs,
			      insn_iret32,
			      insn_iret32_end - insn_iret32);

	if (!regs_equal(&inregs, &outregs, 0))
		print_serial("iret Test 1: FAIL\n");
	else
		print_serial("iret Test 1: PASS\n");

	exec_in_big_real_mode(&inregs, &outregs,
			      insn_iret16,
			      insn_iret16_end - insn_iret16);

	if (!regs_equal(&inregs, &outregs, 0))
		print_serial("iret Test 2: FAIL\n");
	else
		print_serial("iret Test 2: PASS\n");

	exec_in_big_real_mode(&inregs, &outregs,
			      insn_iret_flags32,
			      insn_iret_flags32_end - insn_iret_flags32);

	if (!regs_equal(&inregs, &outregs, R_AX))
		print_serial("iret Test 3: FAIL\n");
	else
		print_serial("iret Test 3: PASS\n");

	exec_in_big_real_mode(&inregs, &outregs,
			      insn_iret_flags16,
			      insn_iret_flags16_end - insn_iret_flags16);

	if (!regs_equal(&inregs, &outregs, R_AX))
		print_serial("iret Test 4: FAIL\n");
	else
		print_serial("iret Test 4: PASS\n");
}

void test_int()
{
	struct regs inregs = { 0 }, outregs;

	*(u32 *)(0x11 * 4) = 0x1000; /* Store a pointer to address 0x1000 in IDT entry 0x11 */
	*(u8 *)(0x1000) = 0xcf; /* 0x1000 contains an IRET instruction */

	MK_INSN(int11, "int $0x11\n\t");

	exec_in_big_real_mode(&inregs, &outregs,
			      insn_int11,
			      insn_int11_end - insn_int11);

	if (!regs_equal(&inregs, &outregs, 0))
		print_serial("int Test 1: FAIL\n");
	else
		print_serial("int Test 1: PASS\n");
}

void test_imul()
{
	struct regs inregs = { 0 }, outregs;

	MK_INSN(imul8_1, "mov $2, %al\n\t"
			"mov $-4, %cx\n\t"
			"imul %cl\n\t");

	MK_INSN(imul16_1, "mov $2, %ax\n\t"
		      "mov $-4, %cx\n\t"
		      "imul %cx\n\t");

	MK_INSN(imul32_1, "mov $2, %eax\n\t"
		       "mov $-4, %ecx\n\t"
		       "imul %ecx\n\t");

	MK_INSN(imul8_2, "mov $0x12340002, %eax\n\t"
			"mov $4, %cx\n\t"
			"imul %cl\n\t");

	MK_INSN(imul16_2, "mov $2, %ax\n\t"
			"mov $4, %cx\n\t"
			"imul %cx\n\t");

	MK_INSN(imul32_2, "mov $2, %eax\n\t"
			"mov $4, %ecx\n\t"
			"imul %ecx\n\t");

	exec_in_big_real_mode(&inregs, &outregs,
			      insn_imul8_1,
			      insn_imul8_1_end - insn_imul8_1);

	if (!regs_equal(&inregs, &outregs, R_AX | R_CX | R_DX) || (outregs.eax & 0xff) != (u8)-8)
		print_serial("imul Test 1: FAIL\n");
	else
		print_serial("imul Test 1: PASS\n");

	exec_in_big_real_mode(&inregs, &outregs,
			      insn_imul16_1,
			      insn_imul16_1_end - insn_imul16_1);

	if (!regs_equal(&inregs, &outregs, R_AX | R_CX | R_DX) || outregs.eax != (u16)-8)
		print_serial("imul Test 2: FAIL\n");
	else
		print_serial("imul Test 2: PASS\n");

	exec_in_big_real_mode(&inregs, &outregs,
			      insn_imul32_1,
			      insn_imul32_1_end - insn_imul32_1);

	if (!regs_equal(&inregs, &outregs, R_AX | R_CX | R_DX) || outregs.eax != (u32)-8)
		print_serial("imul Test 3: FAIL\n");
	else
		print_serial("imul Test 3: PASS\n");

	exec_in_big_real_mode(&inregs, &outregs,
			      insn_imul8_2,
			      insn_imul8_2_end - insn_imul8_2);

	if (!regs_equal(&inregs, &outregs, R_AX | R_CX | R_DX) || (outregs.eax & 0xffff) != 8 ||
	     (outregs.eax & 0xffff0000) != 0x12340000)
		print_serial("imul Test 4: FAIL\n");
	else
		print_serial("imul Test 4: PASS\n");

	exec_in_big_real_mode(&inregs, &outregs,
			      insn_imul16_2,
			      insn_imul16_2_end - insn_imul16_2);

	if (!regs_equal(&inregs, &outregs, R_AX | R_CX | R_DX) || outregs.eax != 8)
		print_serial("imul Test 5: FAIL\n");
	else
		print_serial("imul Test 5: PASS\n");

	exec_in_big_real_mode(&inregs, &outregs,
			      insn_imul32_2,
			      insn_imul32_2_end - insn_imul32_2);

	if (!regs_equal(&inregs, &outregs, R_AX | R_CX | R_DX) || outregs.eax != 8)
		print_serial("imul Test 6: FAIL\n");
	else
		print_serial("imul Test 6: PASS\n");
}

void test_mul()
{
	struct regs inregs = { 0 }, outregs;

	MK_INSN(mul8, "mov $2, %al\n\t"
			"mov $4, %cx\n\t"
			"imul %cl\n\t");

	MK_INSN(mul16, "mov $2, %ax\n\t"
			"mov $4, %cx\n\t"
			"imul %cx\n\t");

	MK_INSN(mul32, "mov $2, %eax\n\t"
			"mov $4, %ecx\n\t"
			"imul %ecx\n\t");

	exec_in_big_real_mode(&inregs, &outregs,
			      insn_mul8,
			      insn_mul8_end - insn_mul8);

	if (!regs_equal(&inregs, &outregs, R_AX | R_CX | R_DX) || (outregs.eax & 0xff) != 8)
		print_serial("mul Test 1: FAIL\n");
	else
		print_serial("mul Test 1: PASS\n");

	exec_in_big_real_mode(&inregs, &outregs,
			      insn_mul16,
			      insn_mul16_end - insn_mul16);

	if (!regs_equal(&inregs, &outregs, R_AX | R_CX | R_DX) || outregs.eax != 8)
		print_serial("mul Test 2: FAIL\n");
	else
		print_serial("mul Test 2: PASS\n");

	exec_in_big_real_mode(&inregs, &outregs,
			      insn_mul32,
			      insn_mul32_end - insn_mul32);

	if (!regs_equal(&inregs, &outregs, R_AX | R_CX | R_DX) || outregs.eax != 8)
		print_serial("mul Test 3: FAIL\n");
	else
		print_serial("mul Test 3: PASS\n");
}

void test_div()
{
	struct regs inregs = { 0 }, outregs;

	MK_INSN(div8, "mov $257, %ax\n\t"
			"mov $2, %cl\n\t"
			"div %cl\n\t");

	MK_INSN(div16, "mov $512, %ax\n\t"
			"mov $5, %cx\n\t"
			"div %cx\n\t");

	MK_INSN(div32, "mov $512, %eax\n\t"
			"mov $5, %ecx\n\t"
			"div %ecx\n\t");

	exec_in_big_real_mode(&inregs, &outregs,
			     insn_div8,
			     insn_div8_end - insn_div8);

	if (!regs_equal(&inregs, &outregs, R_AX | R_CX | R_DX) || outregs.eax != 384)
		print_serial("div Test 1: FAIL\n");
	else
		print_serial("div Test 1: PASS\n");

	exec_in_big_real_mode(&inregs, &outregs,
			      insn_div16,
			      insn_div16_end - insn_div16);

	if (!regs_equal(&inregs, &outregs, R_AX | R_CX | R_DX) || outregs.eax != 102 ||
	    outregs.edx != 2)
		print_serial("div Test 2: FAIL\n");
	else
		print_serial("div Test 2: PASS\n");

	exec_in_big_real_mode(&inregs, &outregs,
			      insn_div32,
			      insn_div32_end - insn_div32);

	if (!regs_equal(&inregs, &outregs, R_AX | R_CX | R_DX) || outregs.eax != 102 ||
	    outregs.edx != 2)
		print_serial("div Test 3: FAIL\n");
	else
		print_serial("div Test 3: PASS\n");
}

void test_idiv()
{
	struct regs inregs = { 0 }, outregs;

	MK_INSN(idiv8, "mov $256, %ax\n\t"
			"mov $-2, %cl\n\t"
			"idiv %cl\n\t");

	MK_INSN(idiv16, "mov $512, %ax\n\t"
			"mov $-2, %cx\n\t"
			"idiv %cx\n\t");

	MK_INSN(idiv32, "mov $512, %eax\n\t"
			"mov $-2, %ecx\n\t"
			"idiv %ecx\n\t");

	exec_in_big_real_mode(&inregs, &outregs,
			     insn_idiv8,
			     insn_idiv8_end - insn_idiv8);

	if (!regs_equal(&inregs, &outregs, R_AX | R_CX | R_DX) || outregs.eax != (u8)-128)
		print_serial("idiv Test 1: FAIL\n");
	else
		print_serial("idiv Test 1: PASS\n");

	exec_in_big_real_mode(&inregs, &outregs,
			      insn_idiv16,
			      insn_idiv16_end - insn_idiv16);

	if (!regs_equal(&inregs, &outregs, R_AX | R_CX | R_DX) || outregs.eax != (u16)-256)
		print_serial("idiv Test 2: FAIL\n");
	else
		print_serial("idiv Test 2: PASS\n");

	exec_in_big_real_mode(&inregs, &outregs,
			      insn_idiv32,
			      insn_idiv32_end - insn_idiv32);

	if (!regs_equal(&inregs, &outregs, R_AX | R_CX | R_DX) || outregs.eax != (u32)-256)
		print_serial("idiv Test 3: FAIL\n");
	else
		print_serial("idiv Test 3: PASS\n");
}

void test_cbw(void)
{
	struct regs inregs = { 0 }, outregs;

	MK_INSN(cbw, "mov $0xFE, %eax \n\t"
		     "cbw\n\t");
	MK_INSN(cwde, "mov $0xFFFE, %eax \n\t"
		      "cwde\n\t");

	exec_in_big_real_mode(&inregs, &outregs,
			      insn_cbw,
			      insn_cbw_end - insn_cbw);
	if (outregs.eax != 0xFFFE)
		print_serial("cbw test1: FAIL\n");
	else
		print_serial("cbw test 1: PASS\n");

	exec_in_big_real_mode(&inregs, &outregs,
			      insn_cwde,
			      insn_cwde_end - insn_cwde);
	if (outregs.eax != 0xFFFFFFFE)
		print_serial("cwde test1: FAIL\n");
	else
		print_serial("cwde test 1: PASS\n");
}

void test_loopcc(void)
{
	struct regs inregs = { 0 }, outregs;

	MK_INSN(loop, "mov $10, %ecx\n\t"
		      "1: inc %eax\n\t"
		      "loop 1b\n\t");

	MK_INSN(loope, "mov $10, %ecx\n\t"
		       "mov $1, %eax\n\t"
		       "1: dec %eax\n\t"
		       "loope 1b\n\t");

	MK_INSN(loopne, "mov $10, %ecx\n\t"
		        "mov $5, %eax\n\t"
		        "1: dec %eax\n\t"
			"loopne 1b\n\t");

	exec_in_big_real_mode(&inregs, &outregs,
			insn_loop, insn_loop_end - insn_loop);
	if(!regs_equal(&inregs, &outregs, R_AX) || outregs.eax != 10)
		print_serial("LOOPcc short Test 1: FAIL\n");
	else
		print_serial("LOOPcc short Test 1: PASS\n");

	exec_in_big_real_mode(&inregs, &outregs,
			insn_loope, insn_loope_end - insn_loope);
	if(!regs_equal(&inregs, &outregs, R_AX | R_CX) ||
	   outregs.eax != -1 || outregs.ecx != 8)
		print_serial("LOOPcc short Test 2: FAIL\n");
	else
		print_serial("LOOPcc short Test 2: PASS\n");

	exec_in_big_real_mode(&inregs, &outregs,
			insn_loopne, insn_loopne_end - insn_loopne);
	if(!regs_equal(&inregs, &outregs, R_AX | R_CX) ||
	   outregs.eax != 0 || outregs.ecx != 5)
		print_serial("LOOPcc short Test 3: FAIL\n");
	else
		print_serial("LOOPcc short Test 3: PASS\n");
}

static void test_das(void)
{
    struct regs inregs = { 0 }, outregs = { 0 };
    short i;
    static unsigned test_cases[1024] = {
        0x46000000, 0x8701a000, 0x9710fa00, 0x97119a00,
        0x02000101, 0x8301a101, 0x9310fb01, 0x93119b01,
        0x02000202, 0x8301a202, 0x9710fc02, 0x97119c02,
        0x06000303, 0x8701a303, 0x9310fd03, 0x93119d03,
        0x02000404, 0x8301a404, 0x9310fe04, 0x93119e04,
        0x06000505, 0x8701a505, 0x9710ff05, 0x97119f05,
        0x06000606, 0x8701a606, 0x56100006, 0x9711a006,
        0x02000707, 0x8301a707, 0x12100107, 0x9311a107,
        0x02000808, 0x8301a808, 0x12100208, 0x9311a208,
        0x06000909, 0x8701a909, 0x16100309, 0x9711a309,
        0x1200040a, 0x9301a40a, 0x1210040a, 0x9311a40a,
        0x1600050b, 0x9701a50b, 0x1610050b, 0x9711a50b,
        0x1600060c, 0x9701a60c, 0x1610060c, 0x9711a60c,
        0x1200070d, 0x9301a70d, 0x1210070d, 0x9311a70d,
        0x1200080e, 0x9301a80e, 0x1210080e, 0x9311a80e,
        0x1600090f, 0x9701a90f, 0x1610090f, 0x9711a90f,
        0x02001010, 0x8301b010, 0x16100a10, 0x9711aa10,
        0x06001111, 0x8701b111, 0x12100b11, 0x9311ab11,
        0x06001212, 0x8701b212, 0x16100c12, 0x9711ac12,
        0x02001313, 0x8301b313, 0x12100d13, 0x9311ad13,
        0x06001414, 0x8701b414, 0x12100e14, 0x9311ae14,
        0x02001515, 0x8301b515, 0x16100f15, 0x9711af15,
        0x02001616, 0x8301b616, 0x12101016, 0x9311b016,
        0x06001717, 0x8701b717, 0x16101117, 0x9711b117,
        0x06001818, 0x8701b818, 0x16101218, 0x9711b218,
        0x02001919, 0x8301b919, 0x12101319, 0x9311b319,
        0x1600141a, 0x9701b41a, 0x1610141a, 0x9711b41a,
        0x1200151b, 0x9301b51b, 0x1210151b, 0x9311b51b,
        0x1200161c, 0x9301b61c, 0x1210161c, 0x9311b61c,
        0x1600171d, 0x9701b71d, 0x1610171d, 0x9711b71d,
        0x1600181e, 0x9701b81e, 0x1610181e, 0x9711b81e,
        0x1200191f, 0x9301b91f, 0x1210191f, 0x9311b91f,
        0x02002020, 0x8701c020, 0x12101a20, 0x9311ba20,
        0x06002121, 0x8301c121, 0x16101b21, 0x9711bb21,
        0x06002222, 0x8301c222, 0x12101c22, 0x9311bc22,
        0x02002323, 0x8701c323, 0x16101d23, 0x9711bd23,
        0x06002424, 0x8301c424, 0x16101e24, 0x9711be24,
        0x02002525, 0x8701c525, 0x12101f25, 0x9311bf25,
        0x02002626, 0x8701c626, 0x12102026, 0x9711c026,
        0x06002727, 0x8301c727, 0x16102127, 0x9311c127,
        0x06002828, 0x8301c828, 0x16102228, 0x9311c228,
        0x02002929, 0x8701c929, 0x12102329, 0x9711c329,
        0x1600242a, 0x9301c42a, 0x1610242a, 0x9311c42a,
        0x1200252b, 0x9701c52b, 0x1210252b, 0x9711c52b,
        0x1200262c, 0x9701c62c, 0x1210262c, 0x9711c62c,
        0x1600272d, 0x9301c72d, 0x1610272d, 0x9311c72d,
        0x1600282e, 0x9301c82e, 0x1610282e, 0x9311c82e,
        0x1200292f, 0x9701c92f, 0x1210292f, 0x9711c92f,
        0x06003030, 0x8301d030, 0x12102a30, 0x9711ca30,
        0x02003131, 0x8701d131, 0x16102b31, 0x9311cb31,
        0x02003232, 0x8701d232, 0x12102c32, 0x9711cc32,
        0x06003333, 0x8301d333, 0x16102d33, 0x9311cd33,
        0x02003434, 0x8701d434, 0x16102e34, 0x9311ce34,
        0x06003535, 0x8301d535, 0x12102f35, 0x9711cf35,
        0x06003636, 0x8301d636, 0x16103036, 0x9311d036,
        0x02003737, 0x8701d737, 0x12103137, 0x9711d137,
        0x02003838, 0x8701d838, 0x12103238, 0x9711d238,
        0x06003939, 0x8301d939, 0x16103339, 0x9311d339,
        0x1200343a, 0x9701d43a, 0x1210343a, 0x9711d43a,
        0x1600353b, 0x9301d53b, 0x1610353b, 0x9311d53b,
        0x1600363c, 0x9301d63c, 0x1610363c, 0x9311d63c,
        0x1200373d, 0x9701d73d, 0x1210373d, 0x9711d73d,
        0x1200383e, 0x9701d83e, 0x1210383e, 0x9711d83e,
        0x1600393f, 0x9301d93f, 0x1610393f, 0x9311d93f,
        0x02004040, 0x8301e040, 0x16103a40, 0x9311da40,
        0x06004141, 0x8701e141, 0x12103b41, 0x9711db41,
        0x06004242, 0x8701e242, 0x16103c42, 0x9311dc42,
        0x02004343, 0x8301e343, 0x12103d43, 0x9711dd43,
        0x06004444, 0x8701e444, 0x12103e44, 0x9711de44,
        0x02004545, 0x8301e545, 0x16103f45, 0x9311df45,
        0x02004646, 0x8301e646, 0x12104046, 0x9311e046,
        0x06004747, 0x8701e747, 0x16104147, 0x9711e147,
        0x06004848, 0x8701e848, 0x16104248, 0x9711e248,
        0x02004949, 0x8301e949, 0x12104349, 0x9311e349,
        0x1600444a, 0x9701e44a, 0x1610444a, 0x9711e44a,
        0x1200454b, 0x9301e54b, 0x1210454b, 0x9311e54b,
        0x1200464c, 0x9301e64c, 0x1210464c, 0x9311e64c,
        0x1600474d, 0x9701e74d, 0x1610474d, 0x9711e74d,
        0x1600484e, 0x9701e84e, 0x1610484e, 0x9711e84e,
        0x1200494f, 0x9301e94f, 0x1210494f, 0x9311e94f,
        0x06005050, 0x8701f050, 0x12104a50, 0x9311ea50,
        0x02005151, 0x8301f151, 0x16104b51, 0x9711eb51,
        0x02005252, 0x8301f252, 0x12104c52, 0x9311ec52,
        0x06005353, 0x8701f353, 0x16104d53, 0x9711ed53,
        0x02005454, 0x8301f454, 0x16104e54, 0x9711ee54,
        0x06005555, 0x8701f555, 0x12104f55, 0x9311ef55,
        0x06005656, 0x8701f656, 0x16105056, 0x9711f056,
        0x02005757, 0x8301f757, 0x12105157, 0x9311f157,
        0x02005858, 0x8301f858, 0x12105258, 0x9311f258,
        0x06005959, 0x8701f959, 0x16105359, 0x9711f359,
        0x1200545a, 0x9301f45a, 0x1210545a, 0x9311f45a,
        0x1600555b, 0x9701f55b, 0x1610555b, 0x9711f55b,
        0x1600565c, 0x9701f65c, 0x1610565c, 0x9711f65c,
        0x1200575d, 0x9301f75d, 0x1210575d, 0x9311f75d,
        0x1200585e, 0x9301f85e, 0x1210585e, 0x9311f85e,
        0x1600595f, 0x9701f95f, 0x1610595f, 0x9711f95f,
        0x06006060, 0x47010060, 0x16105a60, 0x9711fa60,
        0x02006161, 0x03010161, 0x12105b61, 0x9311fb61,
        0x02006262, 0x03010262, 0x16105c62, 0x9711fc62,
        0x06006363, 0x07010363, 0x12105d63, 0x9311fd63,
        0x02006464, 0x03010464, 0x12105e64, 0x9311fe64,
        0x06006565, 0x07010565, 0x16105f65, 0x9711ff65,
        0x06006666, 0x07010666, 0x16106066, 0x57110066,
        0x02006767, 0x03010767, 0x12106167, 0x13110167,
        0x02006868, 0x03010868, 0x12106268, 0x13110268,
        0x06006969, 0x07010969, 0x16106369, 0x17110369,
        0x1200646a, 0x1301046a, 0x1210646a, 0x1311046a,
        0x1600656b, 0x1701056b, 0x1610656b, 0x1711056b,
        0x1600666c, 0x1701066c, 0x1610666c, 0x1711066c,
        0x1200676d, 0x1301076d, 0x1210676d, 0x1311076d,
        0x1200686e, 0x1301086e, 0x1210686e, 0x1311086e,
        0x1600696f, 0x1701096f, 0x1610696f, 0x1711096f,
        0x02007070, 0x03011070, 0x16106a70, 0x17110a70,
        0x06007171, 0x07011171, 0x12106b71, 0x13110b71,
        0x06007272, 0x07011272, 0x16106c72, 0x17110c72,
        0x02007373, 0x03011373, 0x12106d73, 0x13110d73,
        0x06007474, 0x07011474, 0x12106e74, 0x13110e74,
        0x02007575, 0x03011575, 0x16106f75, 0x17110f75,
        0x02007676, 0x03011676, 0x12107076, 0x13111076,
        0x06007777, 0x07011777, 0x16107177, 0x17111177,
        0x06007878, 0x07011878, 0x16107278, 0x17111278,
        0x02007979, 0x03011979, 0x12107379, 0x13111379,
        0x1600747a, 0x1701147a, 0x1610747a, 0x1711147a,
        0x1200757b, 0x1301157b, 0x1210757b, 0x1311157b,
        0x1200767c, 0x1301167c, 0x1210767c, 0x1311167c,
        0x1600777d, 0x1701177d, 0x1610777d, 0x1711177d,
        0x1600787e, 0x1701187e, 0x1610787e, 0x1711187e,
        0x1200797f, 0x1301197f, 0x1210797f, 0x1311197f,
        0x82008080, 0x03012080, 0x12107a80, 0x13111a80,
        0x86008181, 0x07012181, 0x16107b81, 0x17111b81,
        0x86008282, 0x07012282, 0x12107c82, 0x13111c82,
        0x82008383, 0x03012383, 0x16107d83, 0x17111d83,
        0x86008484, 0x07012484, 0x16107e84, 0x17111e84,
        0x82008585, 0x03012585, 0x12107f85, 0x13111f85,
        0x82008686, 0x03012686, 0x92108086, 0x13112086,
        0x86008787, 0x07012787, 0x96108187, 0x17112187,
        0x86008888, 0x07012888, 0x96108288, 0x17112288,
        0x82008989, 0x03012989, 0x92108389, 0x13112389,
        0x9600848a, 0x1701248a, 0x9610848a, 0x1711248a,
        0x9200858b, 0x1301258b, 0x9210858b, 0x1311258b,
        0x9200868c, 0x1301268c, 0x9210868c, 0x1311268c,
        0x9600878d, 0x1701278d, 0x9610878d, 0x1711278d,
        0x9600888e, 0x1701288e, 0x9610888e, 0x1711288e,
        0x9200898f, 0x1301298f, 0x9210898f, 0x1311298f,
        0x86009090, 0x07013090, 0x92108a90, 0x13112a90,
        0x82009191, 0x03013191, 0x96108b91, 0x17112b91,
        0x82009292, 0x03013292, 0x92108c92, 0x13112c92,
        0x86009393, 0x07013393, 0x96108d93, 0x17112d93,
        0x82009494, 0x03013494, 0x96108e94, 0x17112e94,
        0x86009595, 0x07013595, 0x92108f95, 0x13112f95,
        0x86009696, 0x07013696, 0x96109096, 0x17113096,
        0x82009797, 0x03013797, 0x92109197, 0x13113197,
        0x82009898, 0x03013898, 0x92109298, 0x13113298,
        0x86009999, 0x07013999, 0x96109399, 0x17113399,
        0x1300349a, 0x1301349a, 0x1310349a, 0x1311349a,
        0x1700359b, 0x1701359b, 0x1710359b, 0x1711359b,
        0x1700369c, 0x1701369c, 0x1710369c, 0x1711369c,
        0x1300379d, 0x1301379d, 0x1310379d, 0x1311379d,
        0x1300389e, 0x1301389e, 0x1310389e, 0x1311389e,
        0x1700399f, 0x1701399f, 0x1710399f, 0x1711399f,
        0x030040a0, 0x030140a0, 0x17103aa0, 0x17113aa0,
        0x070041a1, 0x070141a1, 0x13103ba1, 0x13113ba1,
        0x070042a2, 0x070142a2, 0x17103ca2, 0x17113ca2,
        0x030043a3, 0x030143a3, 0x13103da3, 0x13113da3,
        0x070044a4, 0x070144a4, 0x13103ea4, 0x13113ea4,
        0x030045a5, 0x030145a5, 0x17103fa5, 0x17113fa5,
        0x030046a6, 0x030146a6, 0x131040a6, 0x131140a6,
        0x070047a7, 0x070147a7, 0x171041a7, 0x171141a7,
        0x070048a8, 0x070148a8, 0x171042a8, 0x171142a8,
        0x030049a9, 0x030149a9, 0x131043a9, 0x131143a9,
        0x170044aa, 0x170144aa, 0x171044aa, 0x171144aa,
        0x130045ab, 0x130145ab, 0x131045ab, 0x131145ab,
        0x130046ac, 0x130146ac, 0x131046ac, 0x131146ac,
        0x170047ad, 0x170147ad, 0x171047ad, 0x171147ad,
        0x170048ae, 0x170148ae, 0x171048ae, 0x171148ae,
        0x130049af, 0x130149af, 0x131049af, 0x131149af,
        0x070050b0, 0x070150b0, 0x13104ab0, 0x13114ab0,
        0x030051b1, 0x030151b1, 0x17104bb1, 0x17114bb1,
        0x030052b2, 0x030152b2, 0x13104cb2, 0x13114cb2,
        0x070053b3, 0x070153b3, 0x17104db3, 0x17114db3,
        0x030054b4, 0x030154b4, 0x17104eb4, 0x17114eb4,
        0x070055b5, 0x070155b5, 0x13104fb5, 0x13114fb5,
        0x070056b6, 0x070156b6, 0x171050b6, 0x171150b6,
        0x030057b7, 0x030157b7, 0x131051b7, 0x131151b7,
        0x030058b8, 0x030158b8, 0x131052b8, 0x131152b8,
        0x070059b9, 0x070159b9, 0x171053b9, 0x171153b9,
        0x130054ba, 0x130154ba, 0x131054ba, 0x131154ba,
        0x170055bb, 0x170155bb, 0x171055bb, 0x171155bb,
        0x170056bc, 0x170156bc, 0x171056bc, 0x171156bc,
        0x130057bd, 0x130157bd, 0x131057bd, 0x131157bd,
        0x130058be, 0x130158be, 0x131058be, 0x131158be,
        0x170059bf, 0x170159bf, 0x171059bf, 0x171159bf,
        0x070060c0, 0x070160c0, 0x17105ac0, 0x17115ac0,
        0x030061c1, 0x030161c1, 0x13105bc1, 0x13115bc1,
        0x030062c2, 0x030162c2, 0x17105cc2, 0x17115cc2,
        0x070063c3, 0x070163c3, 0x13105dc3, 0x13115dc3,
        0x030064c4, 0x030164c4, 0x13105ec4, 0x13115ec4,
        0x070065c5, 0x070165c5, 0x17105fc5, 0x17115fc5,
        0x070066c6, 0x070166c6, 0x171060c6, 0x171160c6,
        0x030067c7, 0x030167c7, 0x131061c7, 0x131161c7,
        0x030068c8, 0x030168c8, 0x131062c8, 0x131162c8,
        0x070069c9, 0x070169c9, 0x171063c9, 0x171163c9,
        0x130064ca, 0x130164ca, 0x131064ca, 0x131164ca,
        0x170065cb, 0x170165cb, 0x171065cb, 0x171165cb,
        0x170066cc, 0x170166cc, 0x171066cc, 0x171166cc,
        0x130067cd, 0x130167cd, 0x131067cd, 0x131167cd,
        0x130068ce, 0x130168ce, 0x131068ce, 0x131168ce,
        0x170069cf, 0x170169cf, 0x171069cf, 0x171169cf,
        0x030070d0, 0x030170d0, 0x17106ad0, 0x17116ad0,
        0x070071d1, 0x070171d1, 0x13106bd1, 0x13116bd1,
        0x070072d2, 0x070172d2, 0x17106cd2, 0x17116cd2,
        0x030073d3, 0x030173d3, 0x13106dd3, 0x13116dd3,
        0x070074d4, 0x070174d4, 0x13106ed4, 0x13116ed4,
        0x030075d5, 0x030175d5, 0x17106fd5, 0x17116fd5,
        0x030076d6, 0x030176d6, 0x131070d6, 0x131170d6,
        0x070077d7, 0x070177d7, 0x171071d7, 0x171171d7,
        0x070078d8, 0x070178d8, 0x171072d8, 0x171172d8,
        0x030079d9, 0x030179d9, 0x131073d9, 0x131173d9,
        0x170074da, 0x170174da, 0x171074da, 0x171174da,
        0x130075db, 0x130175db, 0x131075db, 0x131175db,
        0x130076dc, 0x130176dc, 0x131076dc, 0x131176dc,
        0x170077dd, 0x170177dd, 0x171077dd, 0x171177dd,
        0x170078de, 0x170178de, 0x171078de, 0x171178de,
        0x130079df, 0x130179df, 0x131079df, 0x131179df,
        0x830080e0, 0x830180e0, 0x13107ae0, 0x13117ae0,
        0x870081e1, 0x870181e1, 0x17107be1, 0x17117be1,
        0x870082e2, 0x870182e2, 0x13107ce2, 0x13117ce2,
        0x830083e3, 0x830183e3, 0x17107de3, 0x17117de3,
        0x870084e4, 0x870184e4, 0x17107ee4, 0x17117ee4,
        0x830085e5, 0x830185e5, 0x13107fe5, 0x13117fe5,
        0x830086e6, 0x830186e6, 0x931080e6, 0x931180e6,
        0x870087e7, 0x870187e7, 0x971081e7, 0x971181e7,
        0x870088e8, 0x870188e8, 0x971082e8, 0x971182e8,
        0x830089e9, 0x830189e9, 0x931083e9, 0x931183e9,
        0x970084ea, 0x970184ea, 0x971084ea, 0x971184ea,
        0x930085eb, 0x930185eb, 0x931085eb, 0x931185eb,
        0x930086ec, 0x930186ec, 0x931086ec, 0x931186ec,
        0x970087ed, 0x970187ed, 0x971087ed, 0x971187ed,
        0x970088ee, 0x970188ee, 0x971088ee, 0x971188ee,
        0x930089ef, 0x930189ef, 0x931089ef, 0x931189ef,
        0x870090f0, 0x870190f0, 0x93108af0, 0x93118af0,
        0x830091f1, 0x830191f1, 0x97108bf1, 0x97118bf1,
        0x830092f2, 0x830192f2, 0x93108cf2, 0x93118cf2,
        0x870093f3, 0x870193f3, 0x97108df3, 0x97118df3,
        0x830094f4, 0x830194f4, 0x97108ef4, 0x97118ef4,
        0x870095f5, 0x870195f5, 0x93108ff5, 0x93118ff5,
        0x870096f6, 0x870196f6, 0x971090f6, 0x971190f6,
        0x830097f7, 0x830197f7, 0x931091f7, 0x931191f7,
        0x830098f8, 0x830198f8, 0x931092f8, 0x931192f8,
        0x870099f9, 0x870199f9, 0x971093f9, 0x971193f9,
        0x930094fa, 0x930194fa, 0x931094fa, 0x931194fa,
        0x970095fb, 0x970195fb, 0x971095fb, 0x971195fb,
        0x970096fc, 0x970196fc, 0x971096fc, 0x971196fc,
        0x930097fd, 0x930197fd, 0x931097fd, 0x931197fd,
        0x930098fe, 0x930198fe, 0x931098fe, 0x931198fe,
        0x970099ff, 0x970199ff, 0x971099ff, 0x971199ff,
    };

    MK_INSN(das, "das");

    for (i = 0; i < 1024; ++i) {
        unsigned tmp = test_cases[i];
        inregs.eax = tmp & 0xff;
        inregs.eflags = (tmp >> 16) & 0xff;
	exec_in_big_real_mode(&inregs, &outregs,
			      insn_das,
			      insn_das_end - insn_das);

	if (!regs_equal(&inregs, &outregs, R_AX)
            || outregs.eax != ((tmp >> 8) & 0xff)
            || (outregs.eflags & 0xff) != (tmp >> 24)) {
		print_serial("DAS Test: FAIL\n");
                return;
        }
    }
    print_serial("DAS Test: PASS\n");
}

void test_cwd_cdq()
{
	struct regs inregs = { 0 }, outregs;

	/* Sign-bit set */
	MK_INSN(cwd_1, "mov $0x8000, %ax\n\t"
		       "cwd\n\t");

	/* Sign-bit not set */
	MK_INSN(cwd_2, "mov $0x1000, %ax\n\t"
		       "cwd\n\t");

	/* Sign-bit set */
	MK_INSN(cdq_1, "mov $0x80000000, %eax\n\t"
		       "cdq\n\t");

	/* Sign-bit not set */
	MK_INSN(cdq_2, "mov $0x10000000, %eax\n\t"
		       "cdq\n\t");

	exec_in_big_real_mode(&inregs, &outregs,
			      insn_cwd_1,
			      insn_cwd_1_end - insn_cwd_1);

	if (!regs_equal(&inregs, &outregs, R_AX | R_DX) || outregs.eax != 0x8000 || outregs.edx != 0xffff)
		print_serial("cwd Test 1: FAIL\n");
	else
		print_serial("cwd Test 1: PASS\n");

	exec_in_big_real_mode(&inregs, &outregs,
			      insn_cwd_2,
			      insn_cwd_2_end - insn_cwd_2);

	if (!regs_equal(&inregs, &outregs, R_AX | R_DX) || outregs.eax != 0x1000 || outregs.edx != 0)
		print_serial("cwd Test 2: FAIL\n");
	else
		print_serial("cwd Test 2: PASS\n");

	exec_in_big_real_mode(&inregs, &outregs,
			      insn_cdq_1,
			      insn_cdq_1_end - insn_cdq_1);

	if (!regs_equal(&inregs, &outregs, R_AX | R_DX) || outregs.eax != 0x80000000 || outregs.edx != 0xffffffff)
		print_serial("cdq Test 1: FAIL\n");
	else
		print_serial("cdq Test 1: PASS\n");

	exec_in_big_real_mode(&inregs, &outregs,
			      insn_cdq_2,
			      insn_cdq_2_end - insn_cdq_2);

	if (!regs_equal(&inregs, &outregs, R_AX | R_DX) || outregs.eax != 0x10000000 || outregs.edx != 0)
		print_serial("cdq Test 2: FAIL\n");
	else
		print_serial("cdq Test 2: PASS\n");
}

void realmode_start(void)
{
	test_null();

	test_shld();
	test_push_pop();
	test_pusha_popa();
	test_mov_imm();
	test_cmp_imm();
	test_add_imm();
	test_sub_imm();
	test_xor_imm();
	test_io();
	test_eflags_insn();
	test_jcc_short();
	test_jcc_near();
	/* test_call() uses short jump so call it after testing jcc */
	test_call();
	/* long jmp test uses call near so test it after testing call */
	test_long_jmp();
	test_xchg();
	test_iret();
	test_int();
	test_imul();
	test_mul();
	test_div();
	test_idiv();
	test_loopcc();
	test_cbw();
	test_cwd_cdq();
	test_das();

	exit(0);
}

unsigned long long r_gdt[] = { 0, 0x9b000000ffff, 0x93000000ffff };

struct __attribute__((packed)) {
	unsigned short limit;
	void *base;
} r_gdt_descr = { sizeof(r_gdt) - 1, &r_gdt };

asm(
	".section .init \n\t"

	".code32 \n\t"

	"mb_magic = 0x1BADB002 \n\t"
	"mb_flags = 0x0 \n\t"

	"# multiboot header \n\t"
	".long mb_magic, mb_flags, 0 - (mb_magic + mb_flags) \n\t"

	".globl start \n\t"
	".data \n\t"
	". = . + 4096 \n\t"
	"stacktop: \n\t"

	".text \n\t"
	"start: \n\t"
	"lgdt r_gdt_descr \n\t"
	"ljmp $8, $1f; 1: \n\t"
	".code16gcc \n\t"
	"mov $16, %eax \n\t"
	"mov %ax, %ds \n\t"
	"mov %ax, %es \n\t"
	"mov %ax, %fs \n\t"
	"mov %ax, %gs \n\t"
	"mov %ax, %ss \n\t"
	"mov %cr0, %eax \n\t"
	"btc $0, %eax \n\t"
	"mov %eax, %cr0 \n\t"
	"ljmp $0, $realmode_entry \n\t"

	"realmode_entry: \n\t"

	"xor %ax, %ax \n\t"
	"mov %ax, %ds \n\t"
	"mov %ax, %es \n\t"
	"mov %ax, %ss \n\t"
	"mov %ax, %fs \n\t"
	"mov %ax, %gs \n\t"
	"mov $stacktop, %esp\n\t"
	"ljmp $0, $realmode_start \n\t"

	".code16gcc \n\t"
	);