lrmi.c

linux 下svgalib编的一个界面程序示例

		}
	else
		{
		if (size == 4)
			asm volatile ("cld; outsl"
			 : "=S" (esi) : "d" (edx), "0" (esi));
		else if (size == 2)
			asm volatile ("cld; outsw"
			 : "=S" (esi) : "d" (edx), "0" (esi));
		else
			asm volatile ("cld; outsb"
			 : "=S" (esi) : "d" (edx), "0" (esi));
		}

	esi -= (unsigned int)context.vm.regs.ds << 4;

	context.vm.regs.esi &= 0xffff0000;
	context.vm.regs.esi |= esi & 0xffff;
	}

static void
em_rep_outs(int size)
	{
	unsigned int ecx, edx, esi;

	ecx = context.vm.regs.ecx & 0xffff;
	edx = context.vm.regs.edx & 0xffff;
	esi = context.vm.regs.esi & 0xffff;
	esi += (unsigned int)context.vm.regs.ds << 4;

	if (context.vm.regs.eflags & DIRECTION_FLAG)
		{
		if (size == 4)
			asm volatile ("std; rep; outsl; cld"
			 : "=S" (esi), "=c" (ecx)
			 : "d" (edx), "0" (esi), "1" (ecx));
		else if (size == 2)
			asm volatile ("std; rep; outsw; cld"
			 : "=S" (esi), "=c" (ecx)
			 : "d" (edx), "0" (esi), "1" (ecx));
		else
			asm volatile ("std; rep; outsb; cld"
			 : "=S" (esi), "=c" (ecx)
			 : "d" (edx), "0" (esi), "1" (ecx));
		}
	else
		{
		if (size == 4)
			asm volatile ("cld; rep; outsl"
			 : "=S" (esi), "=c" (ecx)
			 : "d" (edx), "0" (esi), "1" (ecx));
		else if (size == 2)
			asm volatile ("cld; rep; outsw"
			 : "=S" (esi), "=c" (ecx)
			 : "d" (edx), "0" (esi), "1" (ecx));
		else
			asm volatile ("cld; rep; outsb"
			 : "=S" (esi), "=c" (ecx)
			 : "d" (edx), "0" (esi), "1" (ecx));
		}

	esi -= (unsigned int)context.vm.regs.ds << 4;

	context.vm.regs.esi &= 0xffff0000;
	context.vm.regs.esi |= esi & 0xffff;

	context.vm.regs.ecx &= 0xffff0000;
	context.vm.regs.ecx |= ecx & 0xffff;
	}

static void
em_inb(void)
	{
	asm volatile ("inb (%w1), %b0"
	 : "=a" (context.vm.regs.eax)
	 : "d" (context.vm.regs.edx), "0" (context.vm.regs.eax));
	}

static void
em_inw(void)
	{
	asm volatile ("inw (%w1), %w0"
	 : "=a" (context.vm.regs.eax)
	 : "d" (context.vm.regs.edx), "0" (context.vm.regs.eax));
	}

static void
em_inl(void)
	{
	asm volatile ("inl (%w1), %0"
	 : "=a" (context.vm.regs.eax)
	 : "d" (context.vm.regs.edx));
	}

static void
em_outb(void)
	{
	asm volatile ("outb %b0, (%w1)"
	 : : "a" (context.vm.regs.eax),
	 "d" (context.vm.regs.edx));
	}

static void
em_outw(void)
	{
	asm volatile ("outw %w0, (%w1)"
	 : : "a" (context.vm.regs.eax),
	 "d" (context.vm.regs.edx));
	}

static void
em_outl(void)
	{
	asm volatile ("outl %0, (%w1)"
	 : : "a" (context.vm.regs.eax),
	 "d" (context.vm.regs.edx));
	}

static int
emulate(void)
	{
	unsigned char *insn;
	struct
		{
		unsigned int size : 1;
		unsigned int rep : 1;
		} prefix = { 0, 0 };
	int i = 0;

	insn = (unsigned char *)((unsigned int)context.vm.regs.cs << 4);
	insn += context.vm.regs.eip;

	while (1)
		{
		if (insn[i] == 0x66)
			{
			prefix.size = 1 - prefix.size;
			i++;
			}
		else if (insn[i] == 0xf3)
			{
			prefix.rep = 1;
			i++;
			}
		else if (insn[i] == 0xf0 || insn[i] == 0xf2
		 || insn[i] == 0x26 || insn[i] == 0x2e
		 || insn[i] == 0x36 || insn[i] == 0x3e
		 || insn[i] == 0x64 || insn[i] == 0x65
		 || insn[i] == 0x67)
			{
			/* these prefixes are just ignored */
			i++;
			}
		else if (insn[i] == 0x6c)
			{
			if (prefix.rep)
				em_rep_ins(1);
			else
				em_ins(1);
			i++;
			break;
			}
		else if (insn[i] == 0x6d)
			{
			if (prefix.rep)
				{
				if (prefix.size)
					em_rep_ins(4);
				else
					em_rep_ins(2);
				}
			else
				{
				if (prefix.size)
					em_ins(4);
				else
					em_ins(2);
				}
			i++;
			break;
			}
		else if (insn[i] == 0x6e)
			{
			if (prefix.rep)
				em_rep_outs(1);
			else
				em_outs(1);
			i++;
			break;
			}
		else if (insn[i] == 0x6f)
			{
			if (prefix.rep)
				{
				if (prefix.size)
					em_rep_outs(4);
				else
					em_rep_outs(2);
				}
			else
				{
				if (prefix.size)
					em_outs(4);
				else
					em_outs(2);
				}
			i++;
			break;
			}
		else if (insn[i] == 0xec)
			{
			em_inb();
			i++;
			break;
			}
		else if (insn[i] == 0xed)
			{
			if (prefix.size)
				em_inl();
			else
				em_inw();
			i++;
			break;
			}
		else if (insn[i] == 0xee)
			{
			em_outb();
			i++;
			break;
			}
		else if (insn[i] == 0xef)
			{
			if (prefix.size)
				em_outl();
			else
				em_outw();

			i++;
			break;
			}
		else
			return 0;
		}

	context.vm.regs.eip += i;
	return 1;
	}


/*
 I don't know how to make sure I get the right vm86() from libc.
 The one I want is syscall # 113 (vm86old() in libc 5, vm86() in glibc)
 which should be declared as "int vm86(struct vm86_struct *);" in
 <sys/vm86.h>.

 This just does syscall 113 with inline asm, which should work
 for both libc's (I hope).
*/
#if !defined(USE_LIBC_VM86)
static int
lrmi_vm86(struct vm86_struct *vm)
	{
	int r;
#ifdef __PIC__
	asm volatile (
	 "pushl %%ebx\n\t"
	 "movl %2, %%ebx\n\t"
	 "int $0x80\n\t"
	 "popl %%ebx"
	 : "=a" (r)
	 : "0" (113), "r" (vm));
#else
	asm volatile (
	 "int $0x80"
	 : "=a" (r)
	 : "0" (113), "b" (vm));
#endif
	return r;
	}
#else
#define lrmi_vm86 vm86
#endif


static void
debug_info(int vret)
	{
	int i;
	unsigned char *p;

	fputs("vm86() failed\n", stderr);
	fprintf(stderr, "return = 0x%x\n", vret);
	fprintf(stderr, "eax = 0x%08lx\n", context.vm.regs.eax);
	fprintf(stderr, "ebx = 0x%08lx\n", context.vm.regs.ebx);
	fprintf(stderr, "ecx = 0x%08lx\n", context.vm.regs.ecx);
	fprintf(stderr, "edx = 0x%08lx\n", context.vm.regs.edx);
	fprintf(stderr, "esi = 0x%08lx\n", context.vm.regs.esi);
	fprintf(stderr, "edi = 0x%08lx\n", context.vm.regs.edi);
	fprintf(stderr, "ebp = 0x%08lx\n", context.vm.regs.ebp);
	fprintf(stderr, "eip = 0x%08lx\n", context.vm.regs.eip);
	fprintf(stderr, "cs  = 0x%04x\n", context.vm.regs.cs);
	fprintf(stderr, "esp = 0x%08lx\n", context.vm.regs.esp);
	fprintf(stderr, "ss  = 0x%04x\n", context.vm.regs.ss);
	fprintf(stderr, "ds  = 0x%04x\n", context.vm.regs.ds);
	fprintf(stderr, "es  = 0x%04x\n", context.vm.regs.es);
	fprintf(stderr, "fs  = 0x%04x\n", context.vm.regs.fs);
	fprintf(stderr, "gs  = 0x%04x\n", context.vm.regs.gs);
	fprintf(stderr, "eflags  = 0x%08lx\n", context.vm.regs.eflags);

	fputs("cs:ip = [ ", stderr);

	p = (unsigned char *)((context.vm.regs.cs << 4) + (context.vm.regs.eip & 0xffff));

	for (i = 0; i < 16; ++i)
		fprintf(stderr, "%02x ", (unsigned int)p[i]);

	fputs("]\n", stderr);
	}


static int
run_vm86(void)
	{
	unsigned int vret;

	while (1)
		{
		vret = lrmi_vm86(&context.vm);

		if (VM86_TYPE(vret) == VM86_INTx)
			{
			unsigned int v = VM86_ARG(vret);

			if (v == RETURN_TO_32_INT)
				return 1;

			pushw(context.vm.regs.eflags);
			pushw(context.vm.regs.cs);
			pushw(context.vm.regs.eip);

			context.vm.regs.cs = get_int_seg(v);
			context.vm.regs.eip = get_int_off(v);
			context.vm.regs.eflags &= ~(VIF_MASK | TF_MASK);

			continue;
			}

		if (VM86_TYPE(vret) != VM86_UNKNOWN)
			break;

		if (!emulate())
			break;
		}

	debug_info(vret);

	return 0;
	}


int
LRMI_call(struct LRMI_regs *r)
	{
	unsigned int vret;

	memset(&context.vm.regs, 0, sizeof(context.vm.regs));

	set_regs(r);

	context.vm.regs.cs = r->cs;
	context.vm.regs.eip = r->ip;

	if (r->ss == 0 && r->sp == 0)
		{
		context.vm.regs.ss = context.stack_seg;
		context.vm.regs.esp = context.stack_off;
		}
	else
		{
		context.vm.regs.ss = r->ss;
		context.vm.regs.esp = r->sp;
		}

	pushw(context.ret_seg);
	pushw(context.ret_off);

	vret = run_vm86();

	get_regs(r);

	return vret;
	}


int
LRMI_int(int i, struct LRMI_regs *r)
	{
	unsigned int vret;
	unsigned int seg, off;

	seg = get_int_seg(i);
	off = get_int_off(i);

	/*
	 If the interrupt is in regular memory, it's probably
	 still pointing at a dos TSR (which is now gone).
	*/
	if (seg < 0xa000 || (seg << 4) + off >= 0x100000)
		{
		fprintf(stderr, "Int 0x%x is not in rom (%04x:%04x)\n", i, seg, off);
		return 0;
		}

	memset(&context.vm.regs, 0, sizeof(context.vm.regs));

	set_regs(r);

	context.vm.regs.cs = seg;
	context.vm.regs.eip = off;

	if (r->ss == 0 && r->sp == 0)
		{
		context.vm.regs.ss = context.stack_seg;
		context.vm.regs.esp = context.stack_off;
		}
	else
		{
		context.vm.regs.ss = r->ss;
		context.vm.regs.esp = r->sp;
		}

	pushw(DEFAULT_VM86_FLAGS);
	pushw(context.ret_seg);
	pushw(context.ret_off);

	vret = run_vm86();

	get_regs(r);

	return vret;
	}