--- np2/i386c/ia32/cpu_mem.c	2004/01/13 16:32:16	1.5
+++ np2/i386c/ia32/cpu_mem.c	2004/01/23 14:33:26	1.6
@@ -1,4 +1,4 @@
-/*	$Id: cpu_mem.c,v 1.5 2004/01/13 16:32:16 monaka Exp $	*/
+/*	$Id: cpu_mem.c,v 1.6 2004/01/23 14:33:26 monaka Exp $	*/
 
 /*
  * Copyright (c) 2002-2003 NONAKA Kimihiro
@@ -76,17 +76,20 @@ init_cpumem(BYTE usemem)
  * memory access check
  */
 void
-cpu_memoryread_check(descriptor_t* sd, DWORD madr, DWORD length, int e)
+cpu_memoryread_check(descriptor_t* sd, DWORD offset, DWORD length, int e)
 {
+	DWORD uplimit;
 
 	if (CPU_STAT_PM) {
 		/* invalid */
 		if (!sd->valid) {
+			VERBOSE(("cpu_memoryread_check: invalid"));
 			EXCEPTION(GP_EXCEPTION, 0);
 		}
 
 		/* not present */
 		if (!sd->p) {
+			VERBOSE(("cpu_memoryread_check: not present"));
 			EXCEPTION(e, 0);
 		}
 
@@ -95,95 +98,126 @@ cpu_memoryread_check(descriptor_t* sd, D
 		case 2:  case 3:	/* rw */
 		case 10: case 11:	/* rx */
 		case 14: case 15:	/* rxc */
-			if ((madr > sd->u.seg.segend - length + 1)
-			    || (length - 1 > sd->u.seg.limit)) {
+			if (offset > sd->u.seg.limit - length + 1) {
+				VERBOSE(("cpu_memoryread_check: offset(%08x) > sd->u.seg.limit(%08x) - length(%08x) + 1", offset, sd->u.seg.limit, length));
+				EXCEPTION(e, 0);
+			}
+			if (length - 1 > sd->u.seg.limit) {
+				VERBOSE(("cpu_memoryread_check: length(%08x) - 1 > sd->u.seg.limit(%08x)", length, sd->u.seg.limit));
 				EXCEPTION(e, 0);
 			}
 			break;
 
 		case 4:  case 5:	/* ro (expand down) */
 		case 6:  case 7:	/* rw (expand down) */
-		{
-			DWORD uplimit = sd->d ? 0xffffffff : 0x0000ffff;
-			if ((madr <= sd->u.seg.segend)
-			    || (madr > uplimit)
-			    || (uplimit - madr < length - 1)) {
+			uplimit = sd->d ? 0xffffffff : 0x0000ffff;
+			if (offset <= sd->u.seg.limit) {
+				VERBOSE(("cpu_memoryread_check: offset(%08x) <= sd->u.seg.limit(%08x)", offset, sd->u.seg.limit));
+				EXCEPTION(e, 0);
+			}
+			if (offset > uplimit) {
+				VERBOSE(("cpu_memoryread_check: offset(%08x) > uplimit(%08x)", offset, uplimit));
+				EXCEPTION(e, 0);
+			}
+			if (uplimit - offset < length - 1) {
+				VERBOSE(("cpu_memoryread_check: uplimit(%08x) - offset(%08x) < length(%08x) - 1", uplimit, offset, length));
 				EXCEPTION(e, 0);
 			}
-		}
 			break;
 
 		default:
+			VERBOSE(("cpu_memoryread_check: invalid type (type = %d)", sd->type));
 			EXCEPTION(e, 0);
 			break;
 		}
 	}
-	sd->flag |= CPU_DESC_READABLE;
+	sd->flag |= CPU_DESC_FLAG_READABLE;
 }
 
 void
-cpu_memorywrite_check(descriptor_t* sd, DWORD madr, DWORD length, int e)
+cpu_memorywrite_check(descriptor_t* sd, DWORD offset, DWORD length, int e)
 {
+	DWORD uplimit;
 
 	if (CPU_STAT_PM) {
 		/* invalid */
 		if (!sd->valid) {
+			VERBOSE(("cpu_memorywrite_check: invalid"));
 			EXCEPTION(GP_EXCEPTION, 0);
 		}
 
 		/* not present */
 		if (!sd->p) {
+			VERBOSE(("cpu_memorywrite_check: not present"));
+			EXCEPTION(e, 0);
+		}
+
+		if (!sd->s) {
+			VERBOSE(("cpu_memorywrite_check: system segment"));
 			EXCEPTION(e, 0);
 		}
 
 		switch (sd->type) {
 		case 2: case 3:	/* rw */
-			if ((madr > sd->u.seg.segend - length + 1)
-			    || (length - 1 > sd->u.seg.limit)) {
+			if (offset > sd->u.seg.limit - length + 1) {
+				VERBOSE(("cpu_memorywrite_check: offset(%08x) > sd->u.seg.limit(%08x) - length(%08x) + 1", offset, sd->u.seg.limit, length));
+				EXCEPTION(e, 0);
+			}
+			if (length - 1 > sd->u.seg.limit) {
+				VERBOSE(("cpu_memorywrite_check: length(%08x) - 1 > sd->u.seg.limit(%08x)", length, sd->u.seg.limit));
 				EXCEPTION(e, 0);
 			}
 			break;
 
 		case 6: case 7:	/* rw (expand down) */
-		{
-			DWORD uplimit = sd->d ? 0xffffffff : 0x0000ffff;
-			if ((madr <= sd->u.seg.segend)
-			    || (madr > uplimit)
-			    || (uplimit - madr < length - 1)) {
+			uplimit = sd->d ? 0xffffffff : 0x0000ffff;
+			if (offset <= sd->u.seg.limit) {
+				VERBOSE(("cpu_memorywrite_check: offset(%08x) <= sd->u.seg.limit(%08x)", offset, sd->u.seg.limit));
+				EXCEPTION(e, 0);
+			}
+			if (offset > uplimit) {
+				VERBOSE(("cpu_memorywrite_check: offset(%08x) > uplimit(%08x)", offset, uplimit));
+				EXCEPTION(e, 0);
+			}
+			if (uplimit - offset < length - 1) {
+				VERBOSE(("cpu_memorywrite_check: uplimit(%08x) - offset(%08x) < length(%08x) - 1", uplimit, offset, length));
 				EXCEPTION(e, 0);
 			}
-		}
 			break;
 
 		default:
+			VERBOSE(("cpu_memorywrite_check: invalid type (type = %d)", sd->type));
 			EXCEPTION(e, 0);
 			break;
 		}
 	}
-	sd->flag |= CPU_DESC_WRITABLE;
+	sd->flag |= CPU_DESC_FLAG_WRITABLE;
 }
 
 BOOL
 cpu_stack_push_check(descriptor_t* sdp, DWORD esp, DWORD length)
 {
+	DWORD limit;
 
 	if (!CPU_STAT_PM)
 		return TRUE;
 
 	if (!sdp->valid || !sdp->p)
 		return FALSE;
-#ifdef _DEBUG
 	if (!sdp->s || sdp->u.seg.c || !sdp->u.seg.wr)
 		return FALSE;
-#endif
 
-	if (!sdp->d)
+	if (!sdp->d) {
 		esp &= 0xffff;
+		limit = 0xffff;
+	} else {
+		limit = 0xffffffff;
+	}
 	if (sdp->u.seg.ec) {
-		DWORD limit = (sdp->d) ? 0xffffffff : 0xffff;
+		/* expand-down stack */
 		if ((esp == 0)
 		 || (esp < length)
-		 || (esp - length <= sdp->u.seg.segend)
+		 || (esp - length <= sdp->u.seg.limit)
 		 || (esp > limit))
 			return FALSE;
 	} else {
@@ -194,7 +228,7 @@ cpu_stack_push_check(descriptor_t* sdp, 
 				return FALSE;
 		} else {
 			if ((esp < length)
-			 || (esp - 1 > sdp->u.seg.segend))
+			 || (esp - 1 > sdp->u.seg.limit))
 				return FALSE;
 		}
 	}
@@ -211,10 +245,8 @@ cpu_stack_pop_check(descriptor_t* sdp, D
 
 	if (!sdp->valid || !sdp->p)
 		return FALSE;
-#ifdef _DEBUG
 	if (!sdp->s || sdp->u.seg.c || !sdp->u.seg.wr)
 		return FALSE;
-#endif
 
 	if (!sdp->d) {
 		esp &= 0xffff;
@@ -223,35 +255,47 @@ cpu_stack_pop_check(descriptor_t* sdp, D
 		limit = 0xffffffff;
 	}
 	if (sdp->u.seg.ec) {
+		/* expand-down stack */
 		if ((esp == limit)
-		 || ((limit  - esp) + 1 < length))
+		 || ((limit - esp) + 1 < length))
 			return FALSE;
 	} else {
 		/* expand-up stack */
 		if ((esp == limit)
 		 || (sdp->u.seg.segend == 0)
-		 || (esp > sdp->u.seg.segend)
-		 || ((sdp->u.seg.segend - esp) + 1 < length))
+		 || (esp > sdp->u.seg.limit)
+		 || ((sdp->u.seg.limit - esp) + 1 < length))
 			return FALSE;
 	}
 	return TRUE;
 }
 
 
+#define	AS32_NOCHECK
+#undef	OVERRUN_CHECK
+
+#if defined(OVERRUN_CHECK)
+#define	OVERRUN_EXCEPTION()	EXCEPTION(GP_EXCEPTION, 0)
+#else
+#define	OVERRUN_EXCEPTION()
+#endif
+
 /*
  * code fetch
  */
 BYTE MEMCALL
-cpu_codefetch(DWORD madr)
+cpu_codefetch(DWORD offset)
 {
 	descriptor_t *sd;
 	DWORD addr;
 
 	sd = &CPU_STAT_SREG(CPU_CS_INDEX);
+#ifndef	AS32_NOCHECK
 	if (!CPU_INST_AS32)
-		madr &= 0xffff;
-	if (madr <= sd->u.seg.segend) {
-		addr = CPU_STAT_SREGBASE(CPU_CS_INDEX) + madr;
+		offset &= 0xffff;
+#endif
+	if (offset <= sd->u.seg.limit) {
+		addr = CPU_STAT_SREGBASE(CPU_CS_INDEX) + offset;
 		if (!CPU_STAT_PM)
 			return cpu_memoryread(addr);
 		return cpu_lcmemoryread(addr);
@@ -261,16 +305,18 @@ cpu_codefetch(DWORD madr)
 }
 
 WORD MEMCALL
-cpu_codefetch_w(DWORD madr)
+cpu_codefetch_w(DWORD offset)
 {
 	descriptor_t *sd;
 	DWORD addr;
 
 	sd = &CPU_STAT_SREG(CPU_CS_INDEX);
+#ifndef	AS32_NOCHECK
 	if (!CPU_INST_AS32)
-		madr &= 0xffff;
-	if (madr <= sd->u.seg.segend - 1) {
-		addr = CPU_STAT_SREGBASE(CPU_CS_INDEX) + madr;
+		offset &= 0xffff;
+#endif
+	if (offset <= sd->u.seg.limit - 1) {
+		addr = CPU_STAT_SREGBASE(CPU_CS_INDEX) + offset;
 		if (!CPU_STAT_PM)
 			return cpu_memoryread_w(addr);
 		return cpu_lcmemoryread_w(addr);
@@ -280,16 +326,18 @@ cpu_codefetch_w(DWORD madr)
 }
 
 DWORD MEMCALL
-cpu_codefetch_d(DWORD madr)
+cpu_codefetch_d(DWORD offset)
 {
 	descriptor_t *sd;
 	DWORD addr;
 
 	sd = &CPU_STAT_SREG(CPU_CS_INDEX);
+#ifndef	AS32_NOCHECK
 	if (!CPU_INST_AS32)
-		madr &= 0xffff;
-	if (madr <= sd->u.seg.segend - 3) {
-		addr = CPU_STAT_SREGBASE(CPU_CS_INDEX) + madr;
+		offset &= 0xffff;
+#endif
+	if (offset <= sd->u.seg.limit - 3) {
+		addr = CPU_STAT_SREGBASE(CPU_CS_INDEX) + offset;
 		if (!CPU_STAT_PM)
 			return cpu_memoryread_d(addr);
 		return cpu_lcmemoryread_d(addr);
@@ -303,193 +351,346 @@ cpu_codefetch_d(DWORD madr)
  * virtual address -> linear address
  */
 BYTE MEMCALL
-cpu_vmemoryread(int idx, DWORD madr)
+cpu_vmemoryread(int idx, DWORD offset)
 {
 	descriptor_t *sd;
 	DWORD addr;
+	int exc;
 
 	__ASSERT((unsigned int)idx < CPU_SEGREG_NUM);
 
 	sd = &CPU_STAT_SREG(idx);
 	if (!sd->valid) {
-		EXCEPTION(GP_EXCEPTION, 0);
+		exc = GP_EXCEPTION;
+		goto err;
 	}
 
+#ifndef	AS32_NOCHECK
 	if (!CPU_INST_AS32)
-		madr &= 0xffff;
-	for (;;) {
-		if ((sd->flag & CPU_DESC_READABLE)
-		    || (madr <= sd->u.seg.segend)) {
-			addr = CPU_STAT_SREGBASE(idx) + madr;
-			if (!CPU_STAT_PM)
-				return cpu_memoryread(addr);
-			return cpu_lmemoryread(addr);
-		}
-		cpu_memoryread_check(sd, madr, 1,
+		offset &= 0xffff;
+#endif
+	if (!(sd->flag & CPU_DESC_FLAG_READABLE)) {
+		cpu_memoryread_check(sd, offset, 1,
 		    (idx == CPU_SS_INDEX) ? SS_EXCEPTION : GP_EXCEPTION);
+	} else {
+		switch (sd->type) {
+		case 4: case 5: case 6: case 7:
+			if (offset <= sd->u.seg.limit) {
+				if (idx == CPU_SS_INDEX)
+					exc = SS_EXCEPTION;
+				else
+					exc = GP_EXCEPTION;
+				goto err;
+			}
+			break;
+
+		default:
+			if (offset > sd->u.seg.limit) {
+				if (idx == CPU_SS_INDEX)
+					exc = SS_EXCEPTION;
+				else
+					exc = GP_EXCEPTION;
+				goto err;
+			}
+			break;
+		}
 	}
-	/*NOTREACHED*/
+	addr = CPU_STAT_SREGBASE(idx) + offset;
+	if (!CPU_STAT_PM)
+		return cpu_memoryread(addr);
+	return cpu_lmemoryread(addr);
+
+err:
+	EXCEPTION(exc, 0);
+	return 0;	/* compiler happy */
 }
 
 WORD MEMCALL
-cpu_vmemoryread_w(int idx, DWORD madr)
+cpu_vmemoryread_w(int idx, DWORD offset)
 {
 	descriptor_t *sd;
 	DWORD addr;
+	int exc;
 
 	__ASSERT((unsigned int)idx < CPU_SEGREG_NUM);
 
 	sd = &CPU_STAT_SREG(idx);
 	if (!sd->valid) {
-		EXCEPTION(GP_EXCEPTION, 0);
+		exc = GP_EXCEPTION;
+		goto err;
 	}
 
+#ifndef	AS32_NOCHECK
 	if (!CPU_INST_AS32)
-		madr &= 0xffff;
-	for (;;) {
-		if ((sd->flag & CPU_DESC_READABLE)
-		    || (madr <= sd->u.seg.segend - 1)) {
-			addr = CPU_STAT_SREGBASE(idx) + madr;
-			if (!CPU_STAT_PM)
-				return cpu_memoryread_w(addr);
-			return cpu_lmemoryread_w(addr);
-		}
-		cpu_memoryread_check(sd, madr, 2,
+		offset &= 0xffff;
+#endif
+	if (!(sd->flag & CPU_DESC_FLAG_READABLE)) {
+		cpu_memoryread_check(sd, offset, 2,
 		    (idx == CPU_SS_INDEX) ? SS_EXCEPTION : GP_EXCEPTION);
-	}
-	/*NOTREACHED*/
+	} else {
+		switch (sd->type) {
+		case 4: case 5: case 6: case 7:
+			if (offset - 1 <= sd->u.seg.limit) {
+				if (idx == CPU_SS_INDEX)
+					exc = SS_EXCEPTION;
+				else
+					exc = GP_EXCEPTION;
+				goto err;
+			}
+			break;
+
+		default:
+			if (offset > sd->u.seg.limit - 1) {
+				if (idx == CPU_SS_INDEX)
+					exc = SS_EXCEPTION;
+				else
+					exc = GP_EXCEPTION;
+				goto err;
+			}
+			break;
+		}
+	} 
+	addr = CPU_STAT_SREGBASE(idx) + offset;
+	if (!CPU_STAT_PM)
+		return cpu_memoryread_w(addr);
+	return cpu_lmemoryread_w(addr);
+
+err:
+	EXCEPTION(exc, 0);
+	return 0;	/* compiler happy */
 }
 
 DWORD MEMCALL
-cpu_vmemoryread_d(int idx, DWORD madr)
+cpu_vmemoryread_d(int idx, DWORD offset)
 {
 	descriptor_t *sd;
 	DWORD addr;
+	int exc;
 
 	__ASSERT((unsigned int)idx < CPU_SEGREG_NUM);
 
 	sd = &CPU_STAT_SREG(idx);
 	if (!sd->valid) {
-		EXCEPTION(GP_EXCEPTION, 0);
+		exc = GP_EXCEPTION;
+		goto err;
 	}
 
+#ifndef	AS32_NOCHECK
 	if (!CPU_INST_AS32)
-		madr &= 0xffff;
-	for (;;) {
-		if ((sd->flag & CPU_DESC_READABLE)
-		    || (madr <= sd->u.seg.segend - 3)) {
-			addr = CPU_STAT_SREGBASE(idx) + madr;
-			if (!CPU_STAT_PM)
-				return cpu_memoryread_d(addr);
-			return cpu_lmemoryread_d(addr);
-		}
-		cpu_memoryread_check(sd, madr, 4,
+		offset &= 0xffff;
+#endif
+	if (!(sd->flag & CPU_DESC_FLAG_READABLE)) {
+		cpu_memoryread_check(sd, offset, 4,
 		    (idx == CPU_SS_INDEX) ? SS_EXCEPTION : GP_EXCEPTION);
+	} else {
+		switch (sd->type) {
+		case 4: case 5: case 6: case 7:
+			if (offset - 3 <= sd->u.seg.limit) {
+				if (idx == CPU_SS_INDEX)
+					exc = SS_EXCEPTION;
+				else
+					exc = GP_EXCEPTION;
+				goto err;
+			}
+			break;
+
+		default:
+			if (offset > sd->u.seg.limit - 3) {
+				if (idx == CPU_SS_INDEX)
+					exc = SS_EXCEPTION;
+				else
+					exc = GP_EXCEPTION;
+				goto err;
+			}
+			break;
+		}
 	}
-	/*NOTREACHED*/
+	addr = CPU_STAT_SREGBASE(idx) + offset;
+	if (!CPU_STAT_PM)
+		return cpu_memoryread_d(addr);
+	return cpu_lmemoryread_d(addr);
+
+err:
+	EXCEPTION(exc, 0);
+	return 0;	/* compiler happy */
 }
 
 /* vaddr memory write */
 void MEMCALL
-cpu_vmemorywrite(int idx, DWORD madr, BYTE val)
+cpu_vmemorywrite(int idx, DWORD offset, BYTE val)
 {
 	descriptor_t *sd;
 	DWORD addr;
+	int exc;
 
 	__ASSERT((unsigned int)idx < CPU_SEGREG_NUM);
 
 	sd = &CPU_STAT_SREG(idx);
 	if (!sd->valid) {
-		EXCEPTION(GP_EXCEPTION, 0);
+		exc = GP_EXCEPTION;
+		goto err;
 	}
 
+#ifndef	AS32_NOCHECK
 	if (!CPU_INST_AS32)
-		madr &= 0xffff;
-	for (;;) {
-		if ((sd->flag & CPU_DESC_WRITABLE)
-		    || (madr <= sd->u.seg.segend)) {
-			addr = CPU_STAT_SREGBASE(idx) + madr;
-			if (!CPU_STAT_PM) {
-				/* real mode */
-				cpu_memorywrite(addr, val);
-			} else {
-				/* protected mode */
-				cpu_lmemorywrite(addr, val);
+		offset &= 0xffff;
+#endif
+	if (!(sd->flag & CPU_DESC_FLAG_WRITABLE)) {
+		cpu_memorywrite_check(sd, offset, 1,
+		    (idx == CPU_SS_INDEX) ? SS_EXCEPTION : GP_EXCEPTION);
+	} else {
+		switch (sd->type) {
+		case 6: case 7:
+			if (offset <= sd->u.seg.limit) {
+				if (idx == CPU_SS_INDEX)
+					exc = SS_EXCEPTION;
+				else
+					exc = GP_EXCEPTION;
+				goto err;
 			}
-			return;
+			break;
+
+		default:
+			if (offset > sd->u.seg.limit) {
+				if (idx == CPU_SS_INDEX)
+					exc = SS_EXCEPTION;
+				else
+					exc = GP_EXCEPTION;
+				goto err;
+			}
+			break;
 		}
-		cpu_memorywrite_check(sd, madr, 1,
-		    (idx == CPU_SS_INDEX) ? SS_EXCEPTION : GP_EXCEPTION);
 	}
-	/*NOTREACHED*/
+	addr = CPU_STAT_SREGBASE(idx) + offset;
+	if (!CPU_STAT_PM) {
+		/* real mode */
+		cpu_memorywrite(addr, val);
+	} else {
+		/* protected mode */
+		cpu_lmemorywrite(addr, val);
+	}
+	return;
+
+err:
+	EXCEPTION(exc, 0);
 }
 
 void MEMCALL
-cpu_vmemorywrite_w(int idx, DWORD madr, WORD val)
+cpu_vmemorywrite_w(int idx, DWORD offset, WORD val)
 {
 	descriptor_t *sd;
 	DWORD addr;
+	int exc;
 
 	__ASSERT((unsigned int)idx < CPU_SEGREG_NUM);
 
 	sd = &CPU_STAT_SREG(idx);
 	if (!sd->valid) {
-		EXCEPTION(GP_EXCEPTION, 0);
+		exc = GP_EXCEPTION;
+		goto err;
 	}
 
+#ifndef	AS32_NOCHECK
 	if (!CPU_INST_AS32)
-		madr &= 0xffff;
-	for (;;) {
-		if ((sd->flag & CPU_DESC_WRITABLE)
-		    || (madr <= sd->u.seg.segend - 1)) {
-			addr = CPU_STAT_SREGBASE(idx) + madr;
-			if (!CPU_STAT_PM) {
-				/* real mode */
-				cpu_memorywrite_w(addr, val);
-			} else {
-				/* protected mode */
-				cpu_lmemorywrite_w(addr, val);
+		offset &= 0xffff;
+#endif
+	if (!(sd->flag & CPU_DESC_FLAG_WRITABLE)) {
+		cpu_memorywrite_check(sd, offset, 2,
+		    (idx == CPU_SS_INDEX) ? SS_EXCEPTION : GP_EXCEPTION);
+	} else {
+		switch (sd->type) {
+		case 6: case 7:
+			if (offset - 1 <= sd->u.seg.limit) {
+				if (idx == CPU_SS_INDEX)
+					exc = SS_EXCEPTION;
+				else
+					exc = GP_EXCEPTION;
+				goto err;
 			}
-			return;
+			break;
+
+		default:
+			if (offset > sd->u.seg.limit - 1) {
+				if (idx == CPU_SS_INDEX)
+					exc = SS_EXCEPTION;
+				else
+					exc = GP_EXCEPTION;
+				goto err;
+			}
+			break;
 		}
-		cpu_memorywrite_check(sd, madr, 2,
-		    (idx == CPU_SS_INDEX) ? SS_EXCEPTION : GP_EXCEPTION);
 	}
-	/*NOTREACHED*/
+	addr = CPU_STAT_SREGBASE(idx) + offset;
+	if (!CPU_STAT_PM) {
+		/* real mode */
+		cpu_memorywrite_w(addr, val);
+	} else {
+		/* protected mode */
+		cpu_lmemorywrite_w(addr, val);
+	}
+	return;
+
+err:
+	EXCEPTION(exc, 0);
 }
 
 void MEMCALL
-cpu_vmemorywrite_d(int idx, DWORD madr, DWORD val)
+cpu_vmemorywrite_d(int idx, DWORD offset, DWORD val)
 {
 	descriptor_t *sd;
 	DWORD addr;
+	int exc;
 
 	__ASSERT((unsigned int)idx < CPU_SEGREG_NUM);
 
 	sd = &CPU_STAT_SREG(idx);
 	if (!sd->valid) {
-		EXCEPTION(GP_EXCEPTION, 0);
+		exc = GP_EXCEPTION;
+		goto err;
 	}
 
+#ifndef	AS32_NOCHECK
 	if (!CPU_INST_AS32)
-		madr &= 0xffff;
-	for (;;) {
-		if ((sd->flag & CPU_DESC_WRITABLE)
-		    || (madr <= sd->u.seg.segend - 3)) {
-			addr = CPU_STAT_SREGBASE(idx) + madr;
-			if (!CPU_STAT_PM) {
-				/* real mode */
-				cpu_memorywrite_d(addr, val);
-			} else {
-				/* protected mode */
-				cpu_lmemorywrite_d(addr, val);
+		offset &= 0xffff;
+#endif
+	if (!(sd->flag & CPU_DESC_FLAG_WRITABLE)) {
+		cpu_memorywrite_check(sd, offset, 4,
+		    (idx == CPU_SS_INDEX) ? SS_EXCEPTION : GP_EXCEPTION);
+	} else {
+		switch (sd->type) {
+		case 6: case 7:
+			if (offset - 3 <= sd->u.seg.limit) {
+				if (idx == CPU_SS_INDEX)
+					exc = SS_EXCEPTION;
+				else
+					exc = GP_EXCEPTION;
+				goto err;
+			}
+			break;
+
+		default:
+			if (offset > sd->u.seg.limit - 3) {
+				if (idx == CPU_SS_INDEX)
+					exc = SS_EXCEPTION;
+				else
+					exc = GP_EXCEPTION;
+				goto err;
 			}
-			return;
+			break;
 		}
-		cpu_memorywrite_check(sd, madr, 4,
-		    (idx == CPU_SS_INDEX) ? SS_EXCEPTION : GP_EXCEPTION);
 	}
-	/*NOTREACHED*/
+	addr = CPU_STAT_SREGBASE(idx) + offset;
+	if (!CPU_STAT_PM) {
+		/* real mode */
+		cpu_memorywrite_d(addr, val);
+	} else {
+		/* protected mode */
+		cpu_lmemorywrite_d(addr, val);
+	}
+	return;
+
+err:
+	EXCEPTION(exc, 0);
 }
 
 /*
@@ -499,20 +700,95 @@ void MEMCALL
 cpu_memorywrite_d(DWORD address, DWORD value)
 {
 	DWORD adr = address & CPU_STAT_ADRSMASK;
+	DWORD diff;
+	DWORD off;
 
 	if (adr < LOWMEM - 3) {
 		__i286_memorywrite_d(adr, value);
 	} else if (adr < LOWMEM) {
-		cpu_memorywrite_w(adr, value & 0xffff);
-		cpu_memorywrite_w(adr + 2, (value >> 16) & 0xffff);
-	} else {
+		diff = LOWMEM - adr;
+
+		switch (diff) {
+		default:
+			ia32_panic("cpu_memorywrite_d: diff(%d)", diff);
+			break;
+
+		case 3:
+			__i286_memorywrite_w(adr, value & 0xffff);
+			value >>= 16;
+			__i286_memorywrite(adr + 2, value & 0xff);
+			value >>= 8;
+			break;
+
+		case 2:
+			__i286_memorywrite_w(adr, value & 0xffff);
+			value >>= 16;
+			break;
+
+		case 1:
+			__i286_memorywrite(adr, value & 0xff);
+			value >>= 8;
+			break;
+		}
+
+		if (extmem_size > 0) {
+			off = 0;
+
+			switch (4 - diff) {
+			case 3:
+				cpumem[off++] = value & 0xff;
+				value >>= 8;
+				if (off >= extmem_size) {
+					OVERRUN_EXCEPTION();
+					break;
+				}
+				/*FALLTHROUGH*/
+			case 2:
+				cpumem[off++] = value & 0xff;
+				if (off >= extmem_size) {
+					OVERRUN_EXCEPTION();
+					break;
+				}
+				value >>= 8;
+				/*FALLTHROUGH*/
+			case 1:
+				cpumem[off] = value & 0xff;
+				break;
+			}
+		} else {
+			OVERRUN_EXCEPTION();
+		}
+	} else if (extmem_size > 0) {
 		adr -= LOWMEM;
 		if (adr < extmem_size - 3) {
 			STOREINTELDWORD(cpumem + adr, value);
 		} else if (adr < extmem_size) {
-			cpu_memorywrite_w(adr, value & 0xffff);
-			cpu_memorywrite_w(adr + 2, (value >> 16) & 0xffff);
+			diff = extmem_size - adr;
+			value >>= (8 * (4 - diff));
+
+			switch (diff) {
+			default:
+				ia32_panic("cpu_memorywrite_d: diff(%d)", diff);
+				break;
+
+			case 3:
+				cpumem[extmem_size - 3] = value & 0xff;
+				value >>= 8;
+				/*FALLTHROUGH*/
+			case 2:
+				cpumem[extmem_size - 2] = value & 0xff;
+				value >>= 8;
+				/*FALLTHROUGH*/
+			case 1:
+				cpumem[extmem_size - 1] = value & 0xff;
+				break;
+			}
+			OVERRUN_EXCEPTION();
+		} else {
+			OVERRUN_EXCEPTION();
 		}
+	} else {
+		OVERRUN_EXCEPTION();
 	}
 }
 
@@ -526,13 +802,18 @@ cpu_memorywrite_w(DWORD address, WORD va
 	} else if (adr < LOWMEM) {
 		__i286_memorywrite(adr, value & 0xff);
 		cpumem[adr - (LOWMEM - 1)] = (value >> 8) & 0xff;
-	} else {
+	} else if (extmem_size > 0) {
 		adr -= LOWMEM;
 		if (adr < extmem_size - 1) {
 			STOREINTELWORD(cpumem + adr, value);
 		} else if (adr == extmem_size - 1) {
 			cpumem[adr] = value & 0xff;
+			OVERRUN_EXCEPTION();
+		} else {
+			OVERRUN_EXCEPTION();
 		}
+	} else {
+		OVERRUN_EXCEPTION();
 	}
 }
 
@@ -543,11 +824,15 @@ cpu_memorywrite(DWORD address, BYTE valu
 
 	if (adr < LOWMEM) {
 		__i286_memorywrite(adr, value);
-	} else {
+	} else if (extmem_size > 0) {
 		adr -= LOWMEM;
 		if (adr < extmem_size) {
 			cpumem[adr] = value;
+		} else {
+			OVERRUN_EXCEPTION();
 		}
+	} else {
+		OVERRUN_EXCEPTION();
 	}
 }
 
@@ -556,20 +841,83 @@ cpu_memoryread_d(DWORD address)
 {
 	DWORD adr = address & CPU_STAT_ADRSMASK;
 	DWORD val;
+	DWORD diff;
 
 	if (adr < LOWMEM - 3) {
 		val = __i286_memoryread_d(adr);
 	} else if (adr < LOWMEM) {
-		val = cpu_memoryread_w(adr);
-		val |= (DWORD)cpu_memoryread_w(adr + 2) << 16;
-	} else {
+		diff = LOWMEM - adr;
+
+		switch (diff) {
+		default:
+			ia32_panic("cpu_memoryread_d: diff(%d)", diff);
+			val = 0;	/* compiler happy */
+			break;
+
+		case 3:
+			val = __i286_memoryread_w(adr);
+			val |= __i286_memoryread(adr + 2);
+			if (extmem_size > 0) {
+				val |= cpumem[0] << 24;
+			} else {
+				val |= 0xff000000;
+				OVERRUN_EXCEPTION();
+			}
+			break;
+
+		case 2:
+			val = __i286_memoryread_w(adr);
+			if (extmem_size > 1) {
+				val |= (DWORD)LOADINTELWORD(cpumem) << 16;
+			} else {
+				val |= 0xffff0000;
+				OVERRUN_EXCEPTION();
+			}
+			break;
+
+		case 1:
+			val = __i286_memoryread(adr);
+			if (extmem_size > 2) {
+				val |= (DWORD)LOADINTELWORD(cpumem) << 8;
+				val |= (DWORD)cpumem[2] << 24;
+			} else {
+				val |= 0xffffff00;
+				OVERRUN_EXCEPTION();
+			}
+			break;
+		}
+	} else if (extmem_size > 0) {
 		adr -= LOWMEM;
 		if (adr < extmem_size - 3) {
 			val = LOADINTELDWORD(cpumem + adr);
+		} else if (adr < extmem_size) {
+			diff = extmem_size - adr;
+			val = 0;
+
+			switch (diff) {
+			default:
+				ia32_panic("cpu_memoryread_d: diff(%d)", diff);
+				break;
+
+			case 3:
+				val |= cpumem[extmem_size - 3];
+				/*FALLTHROUGH*/
+			case 2:
+				val |= (cpumem[extmem_size - 2] << (8 * (diff - 2)));
+				/*FALLTHROUGH*/
+			case 1:
+				val |= (cpumem[extmem_size - 1] << (8 * (diff - 1)));
+				break;
+			}
+			val |= ((DWORD)-1) << (8 * diff);
+			OVERRUN_EXCEPTION();
 		} else {
-			val = cpu_memoryread_w(adr);
-			val |= (DWORD)cpu_memoryread_w(adr + 2) << 16;
+			val = (DWORD)-1;
+			OVERRUN_EXCEPTION();
 		}
+	} else {
+		val = (DWORD)-1;
+		OVERRUN_EXCEPTION();
 	}
 	return val;
 }
@@ -583,17 +931,22 @@ cpu_memoryread_w(DWORD address)
 	if (adr < LOWMEM - 1) {
 		val = __i286_memoryread_w(adr);
 	} else if (adr < LOWMEM) {
-		val = cpu_memoryread(adr);
-		val |= (WORD)cpumem[adr - (LOWMEM - 1)] << 8;
-	} else {
+		val = __i286_memoryread(adr);
+		val |= (WORD)cpumem[0] << 8;
+	} else if (extmem_size > 0) {
 		adr -= LOWMEM;
 		if (adr < extmem_size - 1) {
 			val = LOADINTELWORD(cpumem + adr);
 		} else if (adr == extmem_size - 1) {
 			val = 0xff00 | cpumem[adr];
+			OVERRUN_EXCEPTION();
 		} else {
 			val = (WORD)-1;
+			OVERRUN_EXCEPTION();
 		}
+	} else {
+		val = (WORD)-1;
+		OVERRUN_EXCEPTION();
 	}
 	return val;
 }
@@ -606,13 +959,17 @@ cpu_memoryread(DWORD address)
 
 	if (adr < LOWMEM) {
 		val = __i286_memoryread(adr);
-	} else {
+	} else if (extmem_size > 0) {
 		adr -= LOWMEM;
 		if (adr < extmem_size) {
 			val = cpumem[adr];
 		} else {
 			val = (BYTE)-1;
+			OVERRUN_EXCEPTION();
 		}
+	} else {
+		val = (BYTE)-1;
+		OVERRUN_EXCEPTION();
 	}
 	return val;
 }