add old detection using lrmi

4 files changed, 1086 insertions, 0 deletions

diff --git a/Makefile b/Makefile
index 64da639..0dfad06 100644
--- a/Makefile
+++ b/Makefile
@@ -27,6 +27,9 @@ TARGETS	= monitor-get-edid cvt
 CFLAGS = -O -Wall -g
 OBJS = monitor-get-edid.c
 
+ifeq (i386,$(ARCH))
+OBJS += lrmi.o
+endif
 ifeq (y,$(HAS_VBE))
 OBJS += vbe.o libint10.a libx86emu.a
 else
diff --git a/lrmi.c b/lrmi.c
new file mode 100644
index 0000000..2f896df
--- /dev/null
+++ b/lrmi.c
@@ -0,0 +1,871 @@
+/*
+Linux Real Mode Interface - A library of DPMI-like functions for Linux.
+
+Copyright (C) 1998 by Josh Vanderhoof
+
+You are free to distribute and modify this file, as long as you
+do not remove this copyright notice and clearly label modified
+versions as being modified.
+
+This software has NO WARRANTY.  Use it at your own risk.
+*/
+
+#include <stdio.h>
+#include <string.h>
+#include <sys/io.h>
+#include <asm/vm86.h>
+
+#ifdef USE_LIBC_VM86
+#include <sys/vm86.h>
+#endif
+
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <sys/mman.h>
+#include <unistd.h>
+#include <fcntl.h>
+
+#include "lrmi.h"
+
+#define REAL_MEM_BASE 	((void *)0x10000)
+#define REAL_MEM_SIZE 	0x10000
+#define REAL_MEM_BLOCKS 	0x100
+
+struct mem_block
+	{
+	unsigned int size : 20;
+	unsigned int free : 1;
+	};
+
+static struct
+	{
+	int ready;
+	int count;
+	struct mem_block blocks[REAL_MEM_BLOCKS];
+	} mem_info = { 0 };
+
+static int
+real_mem_init(void)
+	{
+	void *m;
+	int fd_zero;
+
+	if (mem_info.ready)
+		return 1;
+
+	fd_zero = open("/dev/zero", O_RDONLY);
+	if (fd_zero == -1)
+		{
+		perror("open /dev/zero");
+		return 0;
+		}
+
+	m = mmap((void *)REAL_MEM_BASE, REAL_MEM_SIZE,
+	 PROT_READ | PROT_WRITE | PROT_EXEC,
+	 MAP_FIXED | MAP_PRIVATE, fd_zero, 0);
+
+	if (m == (void *)-1)
+		{
+		perror("mmap /dev/zero");
+		close(fd_zero);
+		return 0;
+		}
+
+	mem_info.ready = 1;
+	mem_info.count = 1;
+	mem_info.blocks[0].size = REAL_MEM_SIZE;
+	mem_info.blocks[0].free = 1;
+
+	return 1;
+	}
+
+
+static void
+insert_block(int i)
+	{
+	memmove(
+	 mem_info.blocks + i + 1,
+	 mem_info.blocks + i,
+	 (mem_info.count - i) * sizeof(struct mem_block));
+
+	mem_info.count++;
+	}
+
+static void
+delete_block(int i)
+	{
+	mem_info.count--;
+
+	memmove(
+	 mem_info.blocks + i,
+	 mem_info.blocks + i + 1,
+	 (mem_info.count - i) * sizeof(struct mem_block));
+	}
+
+void *
+LRMI_alloc_real(int size)
+	{
+	int i;
+	char *r = (char *)REAL_MEM_BASE;
+
+	if (!mem_info.ready)
+		return NULL;
+
+	if (mem_info.count == REAL_MEM_BLOCKS)
+		return NULL;
+
+	size = (size + 15) & ~15;
+
+	for (i = 0; i < mem_info.count; i++)
+		{
+		if (mem_info.blocks[i].free && size < mem_info.blocks[i].size)
+			{
+			insert_block(i);
+
+			mem_info.blocks[i].size = size;
+			mem_info.blocks[i].free = 0;
+			mem_info.blocks[i + 1].size -= size;
+
+			return (void *)r;
+			}
+
+		r += mem_info.blocks[i].size;
+		}
+
+	return NULL;
+	}
+
+
+void
+LRMI_free_real(void *m)
+	{
+	int i;
+	char *r = (char *)REAL_MEM_BASE;
+
+	if (!mem_info.ready)
+		return;
+
+	i = 0;
+	while (m != (void *)r)
+		{
+		r += mem_info.blocks[i].size;
+		i++;
+		if (i == mem_info.count)
+			return;
+		}
+
+	mem_info.blocks[i].free = 1;
+
+	if (i + 1 < mem_info.count && mem_info.blocks[i + 1].free)
+		{
+		mem_info.blocks[i].size += mem_info.blocks[i + 1].size;
+		delete_block(i + 1);
+		}
+
+	if (i - 1 >= 0 && mem_info.blocks[i - 1].free)
+		{
+		mem_info.blocks[i - 1].size += mem_info.blocks[i].size;
+		delete_block(i);
+		}
+	}
+
+
+#define DEFAULT_VM86_FLAGS 	(IF_MASK | IOPL_MASK)
+#define DEFAULT_STACK_SIZE 	0x1000
+#define RETURN_TO_32_INT 	255
+
+static struct
+	{
+	int ready;
+	unsigned short ret_seg, ret_off;
+	unsigned short stack_seg, stack_off;
+	struct vm86_struct vm;
+	} context = { 0 };
+
+
+static inline void
+set_bit(unsigned int bit, void *array)
+	{
+	unsigned char *a = array;
+
+	a[bit / 8] |= (1 << (bit % 8));
+	}
+
+
+static inline unsigned int
+get_int_seg(int i)
+	{
+	return *(unsigned short *)(i * 4 + 2);
+	}
+
+
+static inline unsigned int
+get_int_off(int i)
+	{
+	return *(unsigned short *)(i * 4);
+	}
+
+
+static inline void
+pushw(unsigned short i)
+	{
+	struct vm86_regs *r = &context.vm.regs;
+	r->esp -= 2;
+	*(unsigned short *)(((unsigned int)r->ss << 4) + r->esp) = i;
+	}
+
+
+int
+LRMI_init(void)
+	{
+	void *m;
+	int fd_mem;
+
+	if (context.ready)
+		return 1;
+
+	if (!real_mem_init())
+		return 0;
+
+	/*
+	 Map the Interrupt Vectors (0x0 - 0x400) + BIOS data (0x400 - 0x502)
+	 and the ROM (0xa0000 - 0x100000)
+	*/
+	fd_mem = open("/dev/mem", O_RDWR);
+
+	if (fd_mem == -1)
+		{
+		perror("open /dev/mem");
+		return 0;
+		}
+
+	m = mmap((void *)0, 0x502,
+	 PROT_READ | PROT_WRITE | PROT_EXEC,
+	 MAP_FIXED | MAP_PRIVATE, fd_mem, 0);
+
+	if (m == (void *)-1)
+		{
+		perror("mmap /dev/mem");
+		return 0;
+		}
+
+	m = mmap((void *)0xa0000, 0x100000 - 0xa0000,
+	 PROT_READ | PROT_WRITE,
+	 MAP_FIXED | MAP_SHARED, fd_mem, 0xa0000);
+
+	if (m == (void *)-1)
+		{
+		perror("mmap /dev/mem");
+		return 0;
+		}
+
+
+	/*
+	 Allocate a stack
+	*/
+	m = LRMI_alloc_real(DEFAULT_STACK_SIZE);
+
+	context.stack_seg = (unsigned int)m >> 4;
+	context.stack_off = DEFAULT_STACK_SIZE;
+
+	/*
+	 Allocate the return to 32 bit routine
+	*/
+	m = LRMI_alloc_real(2);
+
+	context.ret_seg = (unsigned int)m >> 4;
+	context.ret_off = (unsigned int)m & 0xf;
+
+	((unsigned char *)m)[0] = 0xcd; 	/* int opcode */
+	((unsigned char *)m)[1] = RETURN_TO_32_INT;
+
+	memset(&context.vm, 0, sizeof(context.vm));
+
+	/*
+	 Enable kernel emulation of all ints except RETURN_TO_32_INT
+	*/
+	memset(&context.vm.int_revectored, 0, sizeof(context.vm.int_revectored));
+	set_bit(RETURN_TO_32_INT, &context.vm.int_revectored);
+
+	context.ready = 1;
+
+	return 1;
+	}
+
+
+static void
+set_regs(struct LRMI_regs *r)
+	{
+	context.vm.regs.edi = r->edi;
+	context.vm.regs.esi = r->esi;
+	context.vm.regs.ebp = r->ebp;
+	context.vm.regs.ebx = r->ebx;
+	context.vm.regs.edx = r->edx;
+	context.vm.regs.ecx = r->ecx;
+	context.vm.regs.eax = r->eax;
+	context.vm.regs.eflags = DEFAULT_VM86_FLAGS;
+	context.vm.regs.es = r->es;
+	context.vm.regs.ds = r->ds;
+	context.vm.regs.fs = r->fs;
+	context.vm.regs.gs = r->gs;
+	}
+
+
+static void
+get_regs(struct LRMI_regs *r)
+	{
+	r->edi = context.vm.regs.edi;
+	r->esi = context.vm.regs.esi;
+	r->ebp = context.vm.regs.ebp;
+	r->ebx = context.vm.regs.ebx;
+	r->edx = context.vm.regs.edx;
+	r->ecx = context.vm.regs.ecx;
+	r->eax = context.vm.regs.eax;
+	r->flags = context.vm.regs.eflags;
+	r->es = context.vm.regs.es;
+	r->ds = context.vm.regs.ds;
+	r->fs = context.vm.regs.fs;
+	r->gs = context.vm.regs.gs;
+	}
+
+#define DIRECTION_FLAG 	(1 << 10)
+
+static void
+em_ins(int size)
+	{
+	unsigned int edx, edi;
+
+	edx = context.vm.regs.edx & 0xffff;
+	edi = context.vm.regs.edi & 0xffff;
+	edi += (unsigned int)context.vm.regs.ds << 4;
+
+	if (context.vm.regs.eflags & DIRECTION_FLAG)
+		{
+		if (size == 4)
+			asm volatile ("std; insl; cld"
+			 : "=D" (edi) : "d" (edx), "0" (edi));
+		else if (size == 2)
+			asm volatile ("std; insw; cld"
+			 : "=D" (edi) : "d" (edx), "0" (edi));
+		else
+			asm volatile ("std; insb; cld"
+			 : "=D" (edi) : "d" (edx), "0" (edi));
+		}
+	else
+		{
+		if (size == 4)
+			asm volatile ("cld; insl"
+			 : "=D" (edi) : "d" (edx), "0" (edi));
+		else if (size == 2)
+			asm volatile ("cld; insw"
+			 : "=D" (edi) : "d" (edx), "0" (edi));
+		else
+			asm volatile ("cld; insb"
+			 : "=D" (edi) : "d" (edx), "0" (edi));
+		}
+
+	edi -= (unsigned int)context.vm.regs.ds << 4;
+
+	context.vm.regs.edi &= 0xffff0000;
+	context.vm.regs.edi |= edi & 0xffff;
+	}
+
+static void
+em_rep_ins(int size)
+	{
+	unsigned int ecx, edx, edi;
+
+	ecx = context.vm.regs.ecx & 0xffff;
+	edx = context.vm.regs.edx & 0xffff;
+	edi = context.vm.regs.edi & 0xffff;
+	edi += (unsigned int)context.vm.regs.ds << 4;
+
+	if (context.vm.regs.eflags & DIRECTION_FLAG)
+		{
+		if (size == 4)
+			asm volatile ("std; rep; insl; cld"
+			 : "=D" (edi), "=c" (ecx)
+			 : "d" (edx), "0" (edi), "1" (ecx));
+		else if (size == 2)
+			asm volatile ("std; rep; insw; cld"
+			 : "=D" (edi), "=c" (ecx)
+			 : "d" (edx), "0" (edi), "1" (ecx));
+		else
+			asm volatile ("std; rep; insb; cld"
+			 : "=D" (edi), "=c" (ecx)
+			 : "d" (edx), "0" (edi), "1" (ecx));
+		}
+	else
+		{
+		if (size == 4)
+			asm volatile ("cld; rep; insl"
+			 : "=D" (edi), "=c" (ecx)
+			 : "d" (edx), "0" (edi), "1" (ecx));
+		else if (size == 2)
+			asm volatile ("cld; rep; insw"
+			 : "=D" (edi), "=c" (ecx)
+			 : "d" (edx), "0" (edi), "1" (ecx));
+		else
+			asm volatile ("cld; rep; insb"
+			 : "=D" (edi), "=c" (ecx)
+			 : "d" (edx), "0" (edi), "1" (ecx));
+		}
+
+	edi -= (unsigned int)context.vm.regs.ds << 4;
+
+	context.vm.regs.edi &= 0xffff0000;
+	context.vm.regs.edi |= edi & 0xffff;
+
+	context.vm.regs.ecx &= 0xffff0000;
+	context.vm.regs.ecx |= ecx & 0xffff;
+	}
+
+static void
+em_outs(int size)
+	{
+	unsigned int edx, esi;
+
+	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; outsl; cld"
+			 : "=S" (esi) : "d" (edx), "0" (esi));
+		else if (size == 2)
+			asm volatile ("std; outsw; cld"
+			 : "=S" (esi) : "d" (edx), "0" (esi));
+		else
+			asm volatile ("std; outsb; cld"
+			 : "=S" (esi) : "d" (edx), "0" (esi));
+		}
+	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_inbl(unsigned char literal)
+	{
+	context.vm.regs.eax = inb(literal) & 0xff;
+	}
+
+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_outbl(unsigned char literal)
+	{
+	outb(context.vm.regs.eax & 0xff, literal);
+	}
+
+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] == 0xe4)
+			{
+			em_inbl(insn[i + 1]);
+			i += 2;
+			break;
+			}
+		else if (insn[i] == 0xe6)
+			{
+			em_outbl(insn[i + 1]);
+			i += 2;
+			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;
+#if 1
+	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 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;
+		}
+
+	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)
+		{
+#ifdef ORIGINAL_LRMI_CODE_THAT_GOT_IFDEFED_OUT
+		fprintf(stderr, "Int 0x%x is not in rom (%04x:%04x)\n", i, seg, off);
+#endif
+		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;
+	}
+
diff --git a/lrmi.h b/lrmi.h
new file mode 100644
index 0000000..c9c1863
--- /dev/null
+++ b/lrmi.h
@@ -0,0 +1,85 @@
+/*
+Linux Real Mode Interface - A library of DPMI-like functions for Linux.
+
+Copyright (C) 1998 by Josh Vanderhoof
+
+You are free to distribute and modify this file, as long as you
+do not remove this copyright notice and clearly label modified
+versions as being modified.
+
+This software has NO WARRANTY.  Use it at your own risk.
+*/
+
+#ifndef LRMI_H
+#define LRMI_H
+
+struct LRMI_regs
+	{
+	unsigned int edi;
+	unsigned int esi;
+	unsigned int ebp;
+	unsigned int reserved;
+	unsigned int ebx;
+	unsigned int edx;
+	unsigned int ecx;
+	unsigned int eax;
+	unsigned short int flags;
+	unsigned short int es;
+	unsigned short int ds;
+	unsigned short int fs;
+	unsigned short int gs;
+	unsigned short int ip;
+	unsigned short int cs;
+	unsigned short int sp;
+	unsigned short int ss;
+	};
+
+
+#ifndef LRMI_PREFIX
+#define LRMI_PREFIX LRMI_
+#endif
+
+#define LRMI_CONCAT2(a, b) 	a ## b
+#define LRMI_CONCAT(a, b) 	LRMI_CONCAT2(a, b)
+#define LRMI_MAKENAME(a) 	LRMI_CONCAT(LRMI_PREFIX, a)
+
+/*
+ Initialize
+ returns 1 if sucessful, 0 for failure
+*/
+#define LRMI_init LRMI_MAKENAME(init)
+int
+LRMI_init(void);
+
+/*
+ Simulate a 16 bit far call
+ returns 1 if sucessful, 0 for failure
+*/
+#define LRMI_call LRMI_MAKENAME(call)
+int
+LRMI_call(struct LRMI_regs *r);
+
+/*
+ Simulate a 16 bit interrupt
+ returns 1 if sucessful, 0 for failure
+*/
+#define LRMI_int LRMI_MAKENAME(int)
+int
+LRMI_int(int interrupt, struct LRMI_regs *r);
+
+/*
+ Allocate real mode memory
+ The returned block is paragraph (16 byte) aligned
+*/
+#define LRMI_alloc_real LRMI_MAKENAME(alloc_real)
+void *
+LRMI_alloc_real(int size);
+
+/*
+ Free real mode memory
+*/
+#define LRMI_free_real LRMI_MAKENAME(free_real)
+void
+LRMI_free_real(void *m);
+
+#endif
diff --git a/vbe.c b/vbe.c
index 8f12a3c..c228f24 100644
--- a/vbe.c
+++ b/vbe.c
@@ -15,6 +15,12 @@
 #include "get-edid.h"
 #include "int10/vbios.h"
 
+#ifdef __i386__
+/* some regressions can occur. e.g. Shuttle S754 with built-in VIA VGA,
+   in that case default to previous lrmi code */
+#define LRMI
+#endif
+
 /* This specifies whether CPU emulation is used or real mode execution */
 #ifdef __i386__
 #define cpuemu 0
@@ -157,6 +163,124 @@ int vbe_get_edid_info(char *edid)
   return 1;
 }
 
+#ifdef LRMI
+#include "lrmi.h"
+
+static int vbe_check_vbe_info__old(void)
+{
+  int i;
+  unsigned char *mem;
+  unsigned char v[0x200];
+  struct LRMI_regs regs;
+
+  /* initialize LRMI */
+  if (LRMI_init() == 0) {
+    log_err("VBE: could not initialize LRMI\n");
+    return 0;
+  }
+
+  /* allocate a chunk of memory */
+  mem = LRMI_alloc_real(sizeof(v));
+  if (mem == NULL) {
+    log_err("VBE: could allocate real memory\n");
+    return 0;
+  }
+  memset(mem, 0, sizeof(v));
+
+  /* set up registers for the interrupt call. */
+  memset(&regs, 0, sizeof(regs));
+  regs.eax = 0x4f00;
+  regs.es = ((u_int32_t)mem) >> 4;
+  regs.edi = ((u_int32_t)mem) & 0x0f;
+  memcpy(mem, "VBE2", 4);
+
+  /* do it. */
+  iopl(3);
+  ioperm(0, 0x400, 1);
+  if (LRMI_int(0x10, &regs) == 0) {
+    LRMI_free_real(mem);
+    return 0;
+  }
+
+  /* check for successful return code */
+  i = regs.eax & 0xffff;
+  if (i != 0x4f) {
+    LRMI_free_real(mem);
+    log_err("VBE: Error (0x4f00): 0x%04x\n", i);
+    return 0;
+  }
+
+  /* get memory to return the information */
+  memcpy(v, mem, sizeof(v));
+  LRMI_free_real(mem);
+
+  parse_vbe_info(v);
+  return 1;
+}
+
+static int vbe_get_edid_info__old(char *edid)
+{
+  int i;
+  unsigned char *mem;
+  const int EDID_BLOCK_SIZE = 256;
+  struct LRMI_regs regs;
+
+  /* initialize LRMI */
+  if (LRMI_init() == 0) {
+    log_err("EDID: could not initialize LRMI\n");
+    return 0;
+  }
+
+  /* allocate a chunk of memory */
+  mem = LRMI_alloc_real(EDID_BLOCK_SIZE);
+  if (mem == NULL) {
+    log_err("EDID: could allocate real memory\n");
+    return 0;
+  }
+  memset(mem, 0, EDID_BLOCK_SIZE);
+
+  /* set up registers for the interrupt call. */
+  memset(&regs, 0, sizeof(regs));
+  regs.eax = 0x4f15;
+  regs.ebx = 0x0001;
+  regs.es = ((u_int32_t)mem) >> 4;
+  regs.edi = ((u_int32_t)mem) & 0x0f;
+
+  /* do it. */
+  iopl(3);
+  ioperm(0, 0x400, 1);
+  if (LRMI_int(0x10, &regs) == 0) {
+    LRMI_free_real(mem);
+    return 0;
+  }
+
+  /* check for successful return code */
+  i = regs.eax & 0xffff;
+  if (i != 0x4f) {
+    LRMI_free_real(mem);
+    log_err("EDID: Error (0x4f15): 0x%04x\n", i);
+    return 0;
+  }
+
+  /* get memory to return the information */
+  memcpy(edid, mem, EDID_BLOCK_SIZE);
+  LRMI_free_real(mem);
+  return 1;
+}
+
+int get_edid__old(char *edid)
+{
+  int ok;
+  /* try with older lrmi interface, we can assume a failure for
+     one is also bogus for the other */
+  log_err("Retrying with old LRMI interface\n");
+  ok = 
+    (box_is_xbox() || vbe_check_vbe_info__old()) &&
+    vbe_get_edid_info__old(edid);
+  return ok;
+}
+#endif
+
 int get_edid(char *edid)
 {
   int pci_config_type = 1; /* Determine PCI configuration type */
@@ -171,6 +295,9 @@ int get_edid(char *edid)
       vbe_get_edid_info(edid);
 
     FreeInt10();
+#ifdef LRMI
+    if (!ok) ok = get_edid__old(edid);
+#endif
   } else if (getuid() != 0)
     fprintf(stderr, "you must be root to run this program\n");