--- np2/i386c/ia32/segments.c	2003/12/22 18:00:31	1.3
+++ np2/i386c/ia32/segments.c	2012/02/05 06:16:08	1.26
@@ -1,5 +1,3 @@
-/*	$Id: segments.c,v 1.3 2003/12/22 18:00:31 monaka Exp $	*/
-
 /*
  * Copyright (c) 2003 NONAKA Kimihiro
  * All rights reserved.
@@ -12,8 +10,6 @@
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
  *    documentation and/or other materials provided with the distribution.
- * 3. The name of the author may not be used to endorse or promote products
- *    derived from this software without specific prior written permission.
  *
  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
@@ -31,34 +27,34 @@
 #include "cpu.h"
 #include "ia32.mcr"
 
+static void CPUCALL segdesc_set_default(int, UINT16, descriptor_t *);
 
-void
-load_segreg(int idx, WORD selector, int exc)
+void CPUCALL
+load_segreg(int idx, UINT16 selector, UINT16 *sregp, descriptor_t *sdp, int exc)
 {
 	selector_t sel;
 	int rv;
 
 	__ASSERT((unsigned int)idx < CPU_SEGREG_NUM);
+	__ASSERT((sregp != NULL));
+	__ASSERT((sdp != NULL));
 
 	if (!CPU_STAT_PM || CPU_STAT_VM86) {
-		descriptor_t sd;
-
 		/* real-mode or vm86 mode */
-		CPU_REGS_SREG(idx) = selector;
-
-		sd.u.seg.limit = CPU_STAT_SREGLIMIT(idx);
-		CPU_SET_SEGDESC_DEFAULT(&sd, idx, selector);
-		CPU_STAT_SREG(idx) = sd;
+		*sregp = selector;
+		segdesc_clear(&sel.desc);
+		segdesc_set_default(idx, selector, &sel.desc);
+		*sdp = sel.desc;
 		return;
 	}
 
+	VERBOSE(("load_segreg: EIP = %04x:%08x, idx = %d, selector = %04x, sregp = %p, dp = %p, exc = %d", CPU_CS, CPU_PREV_EIP, idx, selector, sregp, sdp, exc));
+
 	/*
 	 * protected mode
 	 */
-	VERBOSE(("load_segreg: idx = %d, selector = %04x, exc = %d", idx, selector, exc));
-
 	if (idx == CPU_CS_INDEX) {
-		ia32_panic("load_segreg: sreg(%d)", idx);
+		ia32_panic("load_segreg: CS");
 	}
 
 	rv = parse_selector(&sel, selector);
@@ -66,16 +62,18 @@ load_segreg(int idx, WORD selector, int 
 		if ((rv != -2) || (idx == CPU_SS_INDEX)) {
 			EXCEPTION(exc, sel.idx);
 		}
-		CPU_REGS_SREG(idx) = sel.selector;
-		CPU_STAT_SREG_CLEAR(idx);
+		*sregp = sel.selector;
+		segdesc_clear(sdp);
 		return;
 	}
 
 	switch (idx) {
 	case CPU_SS_INDEX:
-		if ((CPU_STAT_CPL != sel.rpl) ||
-		    !sel.desc.s || sel.desc.u.seg.c || !sel.desc.u.seg.wr ||
-		    (CPU_STAT_CPL != sel.desc.dpl)) {
+		if ((CPU_STAT_CPL != sel.rpl)
+		 || (CPU_STAT_CPL != sel.desc.dpl)
+		 || SEG_IS_SYSTEM(&sel.desc)
+		 || SEG_IS_CODE(&sel.desc)
+		 || !SEG_IS_WRITABLE_DATA(&sel.desc)) {
 			EXCEPTION(exc, sel.idx);
 		}
 
@@ -85,24 +83,22 @@ load_segreg(int idx, WORD selector, int 
 			EXCEPTION(SS_EXCEPTION, sel.idx);
 		}
 
-		CPU_STAT_SS32 = sel.desc.d;
-		CPU_REGS_SREG(idx) = sel.selector;
-		CPU_STAT_SREG(idx) = sel.desc;
+		load_ss(sel.selector, &sel.desc, CPU_STAT_CPL);
 		break;
 
 	case CPU_ES_INDEX:
 	case CPU_DS_INDEX:
 	case CPU_FS_INDEX:
 	case CPU_GS_INDEX:
-		/* !(system segment || non-readble code segment */
-		if (!sel.desc.s
-		 || (sel.desc.u.seg.c && !sel.desc.u.seg.wr)) {
+		if (SEG_IS_SYSTEM(&sel.desc)
+		 || (SEG_IS_CODE(&sel.desc) && !SEG_IS_READABLE_CODE(&sel.desc))) {
 			EXCEPTION(exc, sel.idx);
 		}
-		/* data segment || non-conforming code segment */
-		if (!sel.desc.u.seg.c || !sel.desc.u.seg.ec) {
+		if (SEG_IS_DATA(&sel.desc)
+		 || !SEG_IS_CONFORMING_CODE(&sel.desc)) {
 			/* check privilege level */
-			if ((sel.rpl > sel.desc.dpl) || (CPU_STAT_CPL > sel.desc.dpl)) {
+			if ((sel.rpl > sel.desc.dpl)
+			 || (CPU_STAT_CPL > sel.desc.dpl)) {
 				EXCEPTION(exc, sel.idx);
 			}
 		}
@@ -113,8 +109,8 @@ load_segreg(int idx, WORD selector, int 
 			EXCEPTION(NP_EXCEPTION, sel.idx);
 		}
 
-		CPU_REGS_SREG(idx) = sel.selector;
-		CPU_STAT_SREG(idx) = sel.desc;
+		*sregp = sel.selector;
+		*sdp = sel.desc;
 		break;
 	
 	default:
@@ -126,42 +122,47 @@ load_segreg(int idx, WORD selector, int 
 /*
  * load SS register
  */
-void
-load_ss(WORD selector, descriptor_t* sdp, BYTE cpl)
+void CPUCALL
+load_ss(UINT16 selector, const descriptor_t *sdp, int cpl)
 {
 
 	CPU_STAT_SS32 = sdp->d;
-	CPU_REGS_SREG(CPU_SS_INDEX) = (selector & ~3) | (cpl & 3);
-	CPU_STAT_SREG(CPU_SS_INDEX) = *sdp;
+	CPU_SS = (UINT16)((selector & ~3) | (cpl & 3));
+	CPU_SS_DESC = *sdp;
 }
 
 /*
  * load CS register
  */
-void
-load_cs(WORD selector, descriptor_t* sdp, BYTE cpl)
+void CPUCALL
+load_cs(UINT16 selector, const descriptor_t *sdp, int new_cpl)
 {
+	int cpl = new_cpl & 3;
 
-	CPU_STATSAVE.cpu_inst_default.op_32
-	    = CPU_STATSAVE.cpu_inst_default.as_32 = sdp->d;
-	CPU_REGS_SREG(CPU_CS_INDEX) = (selector & ~3) | (cpl & 3);
-	CPU_STAT_SREG(CPU_CS_INDEX) = *sdp;
-	CPU_STAT_CPL = cpl & 3;
+	CPU_INST_OP32 = CPU_INST_AS32 =
+	    CPU_STATSAVE.cpu_inst_default.op_32 =
+	    CPU_STATSAVE.cpu_inst_default.as_32 = sdp->d;
+	CPU_CS = (UINT16)((selector & ~3) | cpl);
+	CPU_CS_DESC = *sdp;
+	set_cpl(cpl);
 }
 
 /*
  * load LDT register
  */
-void
-load_ldtr(WORD selector, int exc)
+void CPUCALL
+load_ldtr(UINT16 selector, int exc)
 {
 	selector_t sel;
 	int rv;
 
+	memset(&sel, 0, sizeof(sel));
+
 	rv = parse_selector(&sel, selector);
 	if (rv < 0 || sel.ldt) {
 		if (rv == -2) {
 			/* null segment */
+			VERBOSE(("load_ldtr: null segment"));
 			CPU_LDTR = 0;
 			memset(&CPU_LDTR_DESC, 0, sizeof(CPU_LDTR_DESC));
 			return;
@@ -170,163 +171,158 @@ load_ldtr(WORD selector, int exc)
 	}
 
 	/* check descriptor type */
-	if (sel.desc.s || (sel.desc.type != CPU_SYSDESC_TYPE_LDT)) {
+	if (!SEG_IS_SYSTEM(&sel.desc)
+	 || (sel.desc.type != CPU_SYSDESC_TYPE_LDT)) {
 		EXCEPTION(exc, sel.selector);
 	}
 
-	/* check limit */
-	if (sel.desc.u.seg.limit < 7) {
-		ia32_panic("load_ldtr: LDTR descriptor limit < 7");
-	}
-
 	/* not present */
 	rv = selector_is_not_present(&sel);
 	if (rv < 0) {
 		EXCEPTION((exc == TS_EXCEPTION) ? TS_EXCEPTION : NP_EXCEPTION, sel.selector);
 	}
 
+#if defined(MORE_DEBUG)
+	ldtr_dump(sel.desc.u.seg.segbase, sel.desc.u.seg.limit);
+#endif
+
 	CPU_LDTR = sel.selector;
 	CPU_LDTR_DESC = sel.desc;
 }
 
-void
-load_descriptor(descriptor_t *descp, DWORD addr)
+void CPUCALL
+load_descriptor(descriptor_t *sdp, UINT32 addr)
 {
+	UINT32 l, h;
 
-	descp->addr = addr;
-	descp->l = cpu_lmemoryread_d(descp->addr);
-	descp->h = cpu_lmemoryread_d(descp->addr + 4);
-
-	descp->flag = 0;
-
-	descp->p = (descp->h & CPU_DESC_H_P) == CPU_DESC_H_P;
-	descp->type = (descp->h & CPU_DESC_H_TYPE) >> 8;
-	descp->dpl = (descp->h & CPU_DESC_H_DPL) >> 13;
-	descp->s = (descp->h & CPU_DESC_H_S) == CPU_DESC_H_S;
+	__ASSERT(sdp != NULL);
 
-	if (descp->s) {
-		/* code/data */
-		descp->valid = 1;
+	VERBOSE(("load_descriptor: address = 0x%08x", addr));
 
-		descp->d = (descp->h & CPU_SEGDESC_H_D) ? 1 : 0;
-		descp->u.seg.c = (descp->h & CPU_SEGDESC_H_D_C) ? 1 : 0;
-		descp->u.seg.g = (descp->h & CPU_SEGDESC_H_G) ? 1 : 0;
-		descp->u.seg.wr = (descp->type & CPU_SEGDESC_TYPE_WR) ? 1 : 0;
-		descp->u.seg.ec = (descp->type & CPU_SEGDESC_TYPE_EC) ? 1 : 0;
+	l = cpu_kmemoryread_d(addr);
+	h = cpu_kmemoryread_d(addr + 4);
+	VERBOSE(("descriptor value = 0x%08x%08x", h, l));
 
-		descp->u.seg.segbase  = (descp->l >> 16) & 0xffff;
-		descp->u.seg.segbase |= (descp->h & 0xff) << 16;
-		descp->u.seg.segbase |= descp->h & 0xff000000;
+	segdesc_clear(sdp);
+	sdp->flag = 0;
 
-		descp->u.seg.limit = (descp->h & 0xf0000) | (descp->l & 0xffff);
-		if (descp->u.seg.g) {
-			descp->u.seg.limit <<= 12;
-			descp->u.seg.limit |= 0xfff;
-		}
+	sdp->p = (h & CPU_DESC_H_P) ? 1 : 0;
+	sdp->type = (UINT8)((h & CPU_DESC_H_TYPE) >> CPU_DESC_H_TYPE_SHIFT);
+	sdp->dpl = (UINT8)((h & CPU_DESC_H_DPL) >> CPU_DESC_H_DPL_SHIFT);
+	sdp->s = (h & CPU_DESC_H_S) ? 1 : 0;
 
-		descp->u.seg.segend = descp->u.seg.segbase + descp->u.seg.limit;
+	if (!SEG_IS_SYSTEM(sdp)) {
+		/* code/data */
+		sdp->valid = 1;
+		sdp->d = (h & CPU_SEGDESC_H_D) ? 1 : 0;
 
-		VERBOSE(("load_descriptor: %s segment descriptor: addr = 0x%08x, h = 0x%04x, l = %04x, type = %d, DPL = %d, base = 0x%08x, limit = 0x%08x, d = %s, g = %s, %s, %s", descp->u.seg.c ? "code" : "data", descp->addr, descp->h, descp->l, descp->type, descp->dpl, descp->u.seg.segbase, descp->u.seg.limit, descp->d ? "on" : "off",  descp->u.seg.g ? "on" : "off", descp->u.seg.c ? (descp->u.seg.wr ? "executable/readable" : "execute-only") : (descp->u.seg.wr ? "writable" : "read-only"), (descp->u.seg.c ? (descp->u.seg.ec ? "conforming" : "non-conforming") : (descp->u.seg.ec ? "expand-down" : "expand-up"))));
+		sdp->u.seg.c = (h & CPU_SEGDESC_H_D_C) ? 1 : 0;
+		sdp->u.seg.g = (h & CPU_SEGDESC_H_G) ? 1 : 0;
+		sdp->u.seg.wr = (sdp->type & CPU_SEGDESC_TYPE_WR) ? 1 : 0;
+		sdp->u.seg.ec = (sdp->type & CPU_SEGDESC_TYPE_EC) ? 1 : 0;
+
+		sdp->u.seg.segbase  = (l >> 16) & 0xffff;
+		sdp->u.seg.segbase |= (h & 0xff) << 16;
+		sdp->u.seg.segbase |= h & 0xff000000;
+		sdp->u.seg.limit = (h & 0xf0000) | (l & 0xffff);
+		if (sdp->u.seg.g) {
+			sdp->u.seg.limit <<= 12;
+			if (SEG_IS_CODE(sdp) || !SEG_IS_EXPANDDOWN_DATA(sdp)) {
+				/* expand-up segment */
+				sdp->u.seg.limit |= 0xfff;
+			}
+		}
 	} else {
 		/* system */
-		switch (descp->type) {
+		switch (sdp->type) {
 		case CPU_SYSDESC_TYPE_LDT:		/* LDT */
-			descp->valid = 1;
-			VERBOSE(("load_descriptor: LDT descriptor"));
+			sdp->valid = 1;
+			sdp->u.seg.g = (h & CPU_SEGDESC_H_G) ? 1 : 0;
+
+			sdp->u.seg.segbase  = h & 0xff000000;
+			sdp->u.seg.segbase |= (h & 0xff) << 16;
+			sdp->u.seg.segbase |= l >> 16;
+			sdp->u.seg.limit  = h & 0xf0000;
+			sdp->u.seg.limit |= l & 0xffff;
+			if (sdp->u.seg.g) {
+				sdp->u.seg.limit <<= 12;
+				sdp->u.seg.limit |= 0xfff;
+			}
 			break;
 
-		case CPU_SYSDESC_TYPE_TASK:
-			descp->valid = 1;
-			descp->u.gate.selector = descp->l >> 16;
-			VERBOSE(("load_descriptor: task descriptor: selector = 0x%04x", descp->u.gate.selector));
+		case CPU_SYSDESC_TYPE_TASK:		/* task gate */
+			sdp->valid = 1;
+			sdp->u.gate.selector = (UINT16)(l >> 16);
 			break;
 
 		case CPU_SYSDESC_TYPE_TSS_16:		/* 286 TSS */
 		case CPU_SYSDESC_TYPE_TSS_BUSY_16:	/* 286 TSS Busy */
-			descp->valid = 1;
-			descp->u.seg.segbase |= (descp->h & 0xff) << 16;
-			descp->u.seg.segbase |= descp->l >> 16;
-			descp->u.seg.limit  = descp->h & 0xf0000;
-			descp->u.seg.limit |= descp->l & 0xffff;
-			descp->u.seg.segend = descp->u.seg.segbase + descp->u.seg.limit;
-			VERBOSE(("load_descriptor: 16bit %sTSS descriptor: base = 0x%08x, limit = 0x%08x", (descp->type & CPU_SYSDESC_TYPE_TSS_BUSY) ? "busy " : "", descp->u.seg.segbase, descp->u.seg.limit));
-			break;
-
-		case CPU_SYSDESC_TYPE_CALL_16:		/* 286 call gate */
-		case CPU_SYSDESC_TYPE_INTR_16:		/* 286 interrupt gate */
-		case CPU_SYSDESC_TYPE_TRAP_16:		/* 286 trap gate */
-			if ((descp->h & 0x0000000e0) == 0) {
-				descp->valid = 1;
-				descp->u.gate.selector = descp->l >> 16;
-				descp->u.gate.offset = descp->l & 0xffff;
-				descp->u.gate.count = descp->h & 0x1f;
-				VERBOSE(("load_descriptor: 16bit %s gate descriptor: selector = 0x%04x, offset = 0x%08x, count = %d", (descp->type == CPU_SYSDESC_TYPE_CALL_16) ? "call" : ((descp->type == CPU_SYSDESC_TYPE_INTR_16) ? "interrupt" : "trap"), descp->u.gate.selector, descp->u.gate.offset, descp->u.gate.count));
-			} else {
-				ia32_panic("load_descriptor: 286 gate is invalid");
-			}
-			break;
-
 		case CPU_SYSDESC_TYPE_TSS_32:		/* 386 TSS */
 		case CPU_SYSDESC_TYPE_TSS_BUSY_32:	/* 386 TSS Busy */
-			descp->valid = 1;
-			descp->d = (descp->h & CPU_SEGDESC_H_D) ? 1 : 0;
-			descp->u.seg.g = (descp->h & CPU_SEGDESC_H_G) ? 1 : 0;
-			descp->u.seg.segbase  = descp->h & 0xff000000;
-			descp->u.seg.segbase |= (descp->h & 0xff) << 16;
-			descp->u.seg.segbase |= descp->l >> 16;
-			descp->u.seg.limit  = descp->h & 0xf0000;
-			descp->u.seg.limit |= descp->l & 0xffff;
-			if (descp->u.seg.g) {
-				descp->u.seg.limit <<= 12;
-				descp->u.seg.limit |= 0xfff;
+			sdp->valid = 1;
+			sdp->d = (h & CPU_GATEDESC_H_D) ? 1 : 0;
+			sdp->u.seg.g = (h & CPU_SEGDESC_H_G) ? 1 : 0;
+
+			sdp->u.seg.segbase  = h & 0xff000000;
+			sdp->u.seg.segbase |= (h & 0xff) << 16;
+			sdp->u.seg.segbase |= l >> 16;
+			sdp->u.seg.limit  = h & 0xf0000;
+			sdp->u.seg.limit |= l & 0xffff;
+			if (sdp->u.seg.g) {
+				sdp->u.seg.limit <<= 12;
+				sdp->u.seg.limit |= 0xfff;
 			}
-			VERBOSE(("load_descriptor: 32bit %sTSS descriptor: base = 0x%08x, limit = 0x%08x, d = %s, g = %s", (descp->type & CPU_SYSDESC_TYPE_TSS_BUSY) ? "busy " : "", descp->u.seg.segbase, descp->u.seg.limit, descp->d ? "on" : "off", descp->u.seg.g ? "on" : "off"));
 			break;
 
+		case CPU_SYSDESC_TYPE_CALL_16:		/* 286 call gate */
+		case CPU_SYSDESC_TYPE_INTR_16:		/* 286 interrupt gate */
+		case CPU_SYSDESC_TYPE_TRAP_16:		/* 286 trap gate */
 		case CPU_SYSDESC_TYPE_CALL_32:		/* 386 call gate */
 		case CPU_SYSDESC_TYPE_INTR_32:		/* 386 interrupt gate */
 		case CPU_SYSDESC_TYPE_TRAP_32:		/* 386 trap gate */
-			if ((descp->h & 0x0000000e0) == 0) {
-				descp->valid = 1;
-				descp->d = (descp->h & CPU_GATEDESC_H_D) ? 1:0;
-				descp->u.gate.selector = descp->l >> 16;
-				descp->u.gate.offset  = descp->h & 0xffff0000;
-				descp->u.gate.offset |= descp->l & 0xffff;
-				descp->u.gate.count = descp->h & 0x1f;
-				VERBOSE(("load_descriptor: 32bit %s gate descriptor: selector = 0x%04x, offset = 0x%08x, count = %d, d = %s", (descp->type == CPU_SYSDESC_TYPE_CALL_16) ? "call" : ((descp->type == CPU_SYSDESC_TYPE_INTR_16) ? "interrupt" : "trap"), descp->u.gate.selector, descp->u.gate.offset, descp->u.gate.count, descp->d ? "on" : "off"));
+			if ((h & 0x0000000e0) == 0) {
+				sdp->valid = 1;
+				sdp->d = (h & CPU_GATEDESC_H_D) ? 1 : 0;
+				sdp->u.gate.selector = (UINT16)(l >> 16);
+				sdp->u.gate.offset  = h & 0xffff0000;
+				sdp->u.gate.offset |= l & 0xffff;
+				sdp->u.gate.count = (UINT8)(h & 0x1f);
 			} else {
-				ia32_panic("load_descriptor: 286 gate is invalid");
+				sdp->valid = 0;
+				VERBOSE(("load_descriptor: gate is invalid"));
 			}
 			break;
 
 		case 0: case 8: case 10: case 13: /* reserved */
 		default:
-			descp->valid = 0;
-			ia32_panic("bad segment descriptor (%d)", descp->type);
+			sdp->valid = 0;
 			break;
 		}
 	}
+#if defined(DEBUG)
+	segdesc_dump(sdp);
+#endif
 }
 
-int
-parse_selector(selector_t* ssp, WORD selector)
+int CPUCALL
+parse_selector(selector_t *ssp, UINT16 selector)
 {
-	DWORD base;
-	WORD limit;
-	WORD idx;
+	UINT32 base;
+	UINT limit;
+	UINT idx;
 
 	ssp->selector = selector;
 	ssp->idx = selector & ~3;
 	ssp->rpl = selector & 3;
-	ssp->ldt = selector & CPU_SEGMENT_TABLE_IND;
+	ssp->ldt = (UINT8)(selector & CPU_SEGMENT_TABLE_IND);
 
 	VERBOSE(("parse_selector: selector = %04x, index = %d, RPL = %d, %cDT", ssp->selector, ssp->idx >> 3, ssp->rpl, ssp->ldt ? 'L' : 'G'));
 
 	/* descriptor table */
-	idx = selector & ~7;
+	idx = selector & CPU_SEGMENT_SELECTOR_INDEX_MASK;
 	if (ssp->ldt) {
 		/* LDT */
-		if (!CPU_LDTR_DESC.valid) {
+		if (!SEG_IS_VALID(&CPU_LDTR_DESC)) {
 			VERBOSE(("parse_selector: LDT is invalid"));
 			return -1;
 		}
@@ -342,26 +338,77 @@ parse_selector(selector_t* ssp, WORD sel
 		limit = CPU_GDTR_LIMIT;
 	}
 	if (idx + 7 > limit) {
-		VERBOSE(("parse_selector: segment limit check failed"));
+		VERBOSE(("parse_selector: segment limit check failed: 0x%08x > 0x%08x", idx + 7, limit));
 		return -3;
 	}
+
 	/* load descriptor */
-	CPU_SET_SEGDESC(&ssp->desc, base + idx);
-	if (!ssp->desc.valid) {
+	ssp->addr = base + idx;
+	load_descriptor(&ssp->desc, ssp->addr);
+	if (!SEG_IS_VALID(&ssp->desc)) {
 		VERBOSE(("parse_selector: segment descriptor is invalid"));
 		return -4;
 	}
+
 	return 0;
 }
 
-int
-selector_is_not_present(selector_t* ssp)
+int CPUCALL
+selector_is_not_present(const selector_t *ssp)
 {
+	UINT32 h;
+
 	/* not present */
-	if (!ssp->desc.p) {
+	if (!SEG_IS_PRESENT(&ssp->desc)) {
 		VERBOSE(("selector_is_not_present: not present"));
 		return -1;
 	}
-	CPU_SET_SEGDESC_POSTPART(&ssp->desc);
+
+	/* set access bit if code/data segment descriptor */
+	if (!SEG_IS_SYSTEM(&ssp->desc)) {
+		h = cpu_kmemoryread_d(ssp->addr + 4);
+		if (!(h & CPU_SEGDESC_H_A)) {
+			h |= CPU_SEGDESC_H_A;
+			cpu_kmemorywrite_d(ssp->addr + 4, h);
+		}
+	}
+
 	return 0;
 }
+
+void CPUCALL
+segdesc_init(int idx, UINT16 sreg, descriptor_t *sdp)
+{
+
+	__ASSERT(((unsigned int)idx < CPU_SEGREG_NUM));
+	__ASSERT((sdp != NULL));
+
+	CPU_REGS_SREG(idx) = sreg;
+	segdesc_clear(sdp);
+	segdesc_set_default(idx, sreg, sdp);
+}
+
+static void CPUCALL
+segdesc_set_default(int idx, UINT16 selector, descriptor_t *sdp)
+{
+
+	__ASSERT(((unsigned int)idx < CPU_SEGREG_NUM));
+	__ASSERT((sdp != NULL));
+
+	sdp->u.seg.segbase = (UINT32)selector << 4;
+	sdp->u.seg.limit = 0xffff;
+	sdp->u.seg.c = (idx == CPU_CS_INDEX) ? 1 : 0;	/* code or data */
+	sdp->u.seg.g = 0;	/* non 4k factor scale */
+	sdp->u.seg.wr = 1;	/* execute/read(CS) or read/write(others) */
+	sdp->u.seg.ec = 0;	/* nonconforming(CS) or expand-up(others) */
+	sdp->valid = 1;		/* valid */
+	sdp->p = 1;		/* present */
+	sdp->type = (CPU_SEGDESC_TYPE_WR << CPU_DESC_H_TYPE_SHIFT)
+	            | ((idx == CPU_CS_INDEX) ? CPU_SEGDESC_H_D_C : 0);
+				/* readable code/writable data segment */
+	sdp->dpl = CPU_STAT_VM86 ? 3 : 0; /* descriptor privilege level */
+	sdp->rpl = CPU_STAT_VM86 ? 3 : 0; /* request privilege level */
+	sdp->s = 1;		/* code/data */
+	sdp->d = 0;		/* 16bit */
+	sdp->flag = CPU_DESC_FLAG_READABLE|CPU_DESC_FLAG_WRITABLE;
+}