--- np2/i386c/ia32/task.c	2003/12/08 00:55:31	1.1
+++ np2/i386c/ia32/task.c	2004/03/24 14:34:23	1.19
@@ -1,4 +1,4 @@
-/*	$Id: task.c,v 1.1 2003/12/08 00:55:31 yui Exp $	*/
+/*	$Id: task.c,v 1.19 2004/03/24 14:34:23 monaka Exp $	*/
 
 /*
  * Copyright (c) 2003 NONAKA Kimihiro
@@ -33,10 +33,14 @@
 
 
 void
-load_tr(WORD selector)
+load_tr(UINT16 selector)
 {
 	selector_t task_sel;
 	int rv;
+#if defined(IA32_SUPPORT_DEBUG_REGISTER)
+	int i;
+#endif
+	UINT16 iobase;
 
 	rv = parse_selector(&task_sel, selector);
 	if (rv < 0 || task_sel.ldt || task_sel.desc.s) {
@@ -49,17 +53,19 @@ load_tr(WORD selector)
 		if (task_sel.desc.u.seg.limit < 0x2b) {
 			EXCEPTION(TS_EXCEPTION, task_sel.idx);
 		}
+		iobase = 0;
 		break;
 
 	case CPU_SYSDESC_TYPE_TSS_32:
 		if (task_sel.desc.u.seg.limit < 0x67) {
 			EXCEPTION(TS_EXCEPTION, task_sel.idx);
 		}
+		iobase = cpu_kmemoryread_w(task_sel.desc.u.seg.segbase + 102);
 		break;
 
 	default:
 		EXCEPTION(GP_EXCEPTION, task_sel.idx);
-		break;
+		return;
 	}
 
 	/* not present */
@@ -68,47 +74,72 @@ load_tr(WORD selector)
 		EXCEPTION(NP_EXCEPTION, task_sel.idx);
 	}
 
-	CPU_SET_TASK_BUSY(&task_sel.desc);
+#if defined(MORE_DEBUG)
+	tr_dump(task_sel.selector, task_sel.desc.u.seg.segbase, task_sel.desc.u.seg.limit);
+#endif
+
+	CPU_SET_TASK_BUSY(task_sel.selector, &task_sel.desc);
 	CPU_TR = task_sel.selector;
 	CPU_TR_DESC = task_sel.desc;
+
+	/* I/O deny bitmap */
+	if (task_sel.desc.type == CPU_SYSDESC_TYPE_TSS_BUSY_32) {
+		if (iobase != 0 && iobase < task_sel.desc.u.seg.limit) {
+			CPU_STAT_IOLIMIT = (UINT16)(task_sel.desc.u.seg.limit - iobase);
+			CPU_STAT_IOADDR = task_sel.desc.u.seg.segbase + iobase;
+		} else {
+			CPU_STAT_IOLIMIT = 0;
+		}
+	} else {
+		CPU_STAT_IOLIMIT = 0;
+	}
+
+#if defined(IA32_SUPPORT_DEBUG_REGISTER)
+	/* clear local break point flags */
+	CPU_DR7 &= ~(CPU_DR7_L(0)|CPU_DR7_L(1)|CPU_DR7_L(2)|CPU_DR7_L(3)|CPU_DR7_LE);
+	CPU_STAT_BP = 0;
+	for (i = 0; i < CPU_DEBUG_REG_INDEX_NUM; i++) {
+		if (CPU_DR7 & CPU_DR7_G(i)) {
+			CPU_STAT_BP |= (1 << i);
+		}
+	}
+#endif
 }
 
 void
-get_stack_from_tss(BYTE pl, WORD* new_ss, DWORD* new_esp)
+get_stack_pointer_from_tss(UINT pl, UINT16 *new_ss, UINT32 *new_esp)
 {
-	DWORD tss_stack_addr;
+	UINT32 tss_stack_addr;
 
-	switch (CPU_TR_DESC.type) {
-	case CPU_SYSDESC_TYPE_TSS_BUSY_32:
+	__ASSERT(pl < 3);
+
+	if (CPU_TR_DESC.type == CPU_SYSDESC_TYPE_TSS_BUSY_32) {
 		tss_stack_addr = pl * 8 + 4;
 		if (tss_stack_addr + 7 > CPU_TR_DESC.u.seg.limit) {
 			EXCEPTION(TS_EXCEPTION, CPU_TR & ~3);
 		}
 		tss_stack_addr += CPU_TR_DESC.u.seg.segbase;
-		*new_esp = cpu_lmemoryread_d(tss_stack_addr);
-		*new_ss = cpu_lmemoryread_w(tss_stack_addr + 4);
-		break;
-
-	case CPU_SYSDESC_TYPE_TSS_BUSY_16:
+		*new_esp = cpu_kmemoryread_d(tss_stack_addr);
+		*new_ss = cpu_kmemoryread_w(tss_stack_addr + 4);
+	} else if (CPU_TR_DESC.type == CPU_SYSDESC_TYPE_TSS_BUSY_16) {
 		tss_stack_addr = pl * 4 + 2;
-		if (tss_stack_addr + 4 > CPU_TR_DESC.u.seg.limit) {
+		if (tss_stack_addr + 3 > CPU_TR_DESC.u.seg.limit) {
 			EXCEPTION(TS_EXCEPTION, CPU_TR & ~3);
 		}
 		tss_stack_addr += CPU_TR_DESC.u.seg.segbase;
-		*new_esp = cpu_lmemoryread_w(tss_stack_addr);
-		*new_ss = cpu_lmemoryread_w(tss_stack_addr + 2);
-		break;
-
-	default:
-		ia32_panic("get_stack_from_tss: TR is invalid (%d)\n",
-		    CPU_TR_DESC.type);
-		break;
+		*new_esp = cpu_kmemoryread_w(tss_stack_addr);
+		*new_ss = cpu_kmemoryread_w(tss_stack_addr + 2);
+	} else {
+		ia32_panic("get_stack_pointer_from_tss: task register is invalid (%d)\n", CPU_TR_DESC.type);
 	}
+
+	VERBOSE(("get_stack_pointer_from_tss: pl = %d, new_esp = 0x%08x, new_ss = 0x%04x", pl, *new_esp, *new_ss));
 }
 
-WORD
-get_link_selector_from_tss()
+UINT16
+get_backlink_selector_from_tss(void)
 {
+	UINT16 backlink;
 
 	if (CPU_TR_DESC.type == CPU_SYSDESC_TYPE_TSS_BUSY_32) {
 		if (4 > CPU_TR_DESC.u.seg.limit) {
@@ -119,100 +150,152 @@ get_link_selector_from_tss()
 			EXCEPTION(TS_EXCEPTION, CPU_TR & ~3);
 		}
 	} else {
-		ia32_panic("get_link_selector_from_tss: TR is invalid (%d)\n",
-		    CPU_TR_DESC.type);
-		return 0;	/* compiler happy */
+		ia32_panic("get_backlink_selector_from_tss: task register is invalid (%d)\n", CPU_TR_DESC.type);
 	}
 
-	return cpu_lmemoryread_w(CPU_TR_DESC.u.seg.segbase);
+	backlink = cpu_kmemoryread_w(CPU_TR_DESC.u.seg.segbase);
+	VERBOSE(("get_backlink_selector_from_tss: backlink selector = 0x%04x", backlink));
+	return backlink;
 }
 
 void
-task_switch(selector_t* task_sel, int type)
+task_switch(selector_t *task_sel, task_switch_type_t type)
 {
-	DWORD regs[CPU_REG_NUM];
-	DWORD eip;
-	DWORD new_flags;
-	DWORD cr3 = 0;
-	WORD sreg[CPU_SEGREG_NUM];
-	WORD ldtr;
-	WORD t, iobase;
+	UINT32 regs[CPU_REG_NUM];
+	UINT32 eip;
+	UINT32 new_flags;
+	UINT32 cr3 = 0;
+	UINT16 sreg[CPU_SEGREG_NUM];
+	UINT16 ldtr;
+	UINT16 iobase;
+	UINT16 t;
 
 	selector_t cs_sel;
 	int rv;
 
-	DWORD cur_base;		/* current task state */
-	DWORD task_base;	/* new task state */
-	DWORD old_flags = REAL_EFLAGREG;
+	UINT32 cur_base;	/* current task state */
+	UINT32 task_base;	/* new task state */
+	UINT32 old_flags = REAL_EFLAGREG;
 	BOOL task16;
-	int nsreg;
-	int i;
+	UINT i;
 
-	cur_base = CPU_TR_DESC.u.seg.segbase;
-	task_base = task_sel->desc.u.seg.segbase;
+	VERBOSE(("task_switch: start"));
 
 	/* limit check */
 	switch (task_sel->desc.type) {
 	case CPU_SYSDESC_TYPE_TSS_32:
 	case CPU_SYSDESC_TYPE_TSS_BUSY_32:
-		if (task_sel->desc.u.seg.limit < 103) {
+		if (task_sel->desc.u.seg.limit < 0x67) {
 			EXCEPTION(TS_EXCEPTION, task_sel->idx);
 		}
 		task16 = FALSE;
-		nsreg = CPU_SEGREG_NUM;
 		break;
 
 	case CPU_SYSDESC_TYPE_TSS_16:
 	case CPU_SYSDESC_TYPE_TSS_BUSY_16:
-		if (task_sel->desc.u.seg.limit < 43) {
+		if (task_sel->desc.u.seg.limit < 0x2b) {
 			EXCEPTION(TS_EXCEPTION, task_sel->idx);
 		}
 		task16 = TRUE;
-		nsreg = CPU_SEGREG286_NUM;
 		break;
 
 	default:
 		ia32_panic("task_switch: descriptor type is invalid.");
 		task16 = FALSE;		/* compiler happy */
-		nsreg = CPU_SEGREG_NUM;	/* compiler happy */
 		break;
 	}
 
+	cur_base = CPU_TR_DESC.u.seg.segbase;
+	task_base = task_sel->desc.u.seg.segbase;
+	VERBOSE(("task_switch: cur task (%04x) = 0x%08x:%08x", CPU_TR, cur_base, CPU_TR_DESC.u.seg.limit));
+	VERBOSE(("task_switch: new task (%04x) = 0x%08x:%08x", task_sel->selector, task_base, task_sel->desc.u.seg.limit));
+	VERBOSE(("task_switch: %dbit task switch", task16 ? 16 : 32));
+
+#if defined(MORE_DEBUG)
+	{
+		UINT32 v;
+
+		VERBOSE(("task_switch: new task"));
+		for (i = 0; i < task_sel->desc.u.seg.limit; i += 4) {
+			v = cpu_kmemoryread_d(task_base + i);
+			VERBOSE(("task_switch: 0x%08x: %08x", task_base + i,v));
+		}
+	}
+#endif
+
 	if (CPU_STAT_PAGING) {
 		/* task state paging check */
-		paging_check(cur_base, CPU_TR_DESC.u.seg.limit, CPU_PAGING_PAGE_WRITE);
-		paging_check(task_base, task_sel->desc.u.seg.limit, CPU_PAGING_PAGE_WRITE);
+		paging_check(cur_base, CPU_TR_DESC.u.seg.limit, CPU_PAGE_WRITE_DATA|CPU_MODE_SUPERVISER);
+		paging_check(task_base, task_sel->desc.u.seg.limit, CPU_PAGE_WRITE_DATA|CPU_MODE_SUPERVISER);
 	}
 
 	/* load task state */
 	memset(sreg, 0, sizeof(sreg));
 	if (!task16) {
 		if (CPU_STAT_PAGING) {
-			cr3 = cpu_lmemoryread_d(task_base + 28);
+			cr3 = cpu_kmemoryread_d(task_base + 28);
 		}
-		eip = cpu_lmemoryread_d(task_base + 32);
-		new_flags = cpu_lmemoryread_d(task_base + 36);
+		eip = cpu_kmemoryread_d(task_base + 32);
+		new_flags = cpu_kmemoryread_d(task_base + 36);
 		for (i = 0; i < CPU_REG_NUM; i++) {
-			regs[i] = cpu_lmemoryread_d(task_base + 40 + i * 4);
+			regs[i] = cpu_kmemoryread_d(task_base + 40 + i * 4);
+		}
+		for (i = 0; i < CPU_SEGREG_NUM; i++) {
+			sreg[i] = cpu_kmemoryread_w(task_base + 72 + i * 4);
 		}
-		for (i = 0; i < nsreg; i++) {
-			sreg[i] = (WORD)cpu_lmemoryread_d(task_base + 72 + i * 4);
+		ldtr = cpu_kmemoryread_w(task_base + 96);
+		t = cpu_kmemoryread_w(task_base + 100);
+		if (t & 1) {
+			CPU_STAT_BP_EVENT |= CPU_STAT_BP_EVENT_TASK;
 		}
-		ldtr = (WORD)cpu_lmemoryread_d(task_base + 96);
-		t = cpu_lmemoryread_w(task_base + 100);
-		iobase = cpu_lmemoryread_w(task_base + 102);
+		iobase = cpu_kmemoryread_w(task_base + 102);
 	} else {
-		eip = cpu_lmemoryread_w(task_base + 14);
-		new_flags = cpu_lmemoryread_w(task_base + 16);
+		eip = cpu_kmemoryread_w(task_base + 14);
+		new_flags = cpu_kmemoryread_w(task_base + 16);
 		for (i = 0; i < CPU_REG_NUM; i++) {
-			regs[i] = cpu_lmemoryread_w(task_base + 18 + i * 2);
+			regs[i] = cpu_kmemoryread_w(task_base + 18 + i * 2);
 		}
-		for (i = 0; i < nsreg; i++) {
-			sreg[i] = cpu_lmemoryread_w(task_base + 34 + i * 2);
+		for (i = 0; i < CPU_SEGREG286_NUM; i++) {
+			sreg[i] = cpu_kmemoryread_w(task_base + 34 + i * 2);
 		}
-		ldtr = cpu_lmemoryread_w(task_base + 42);
+		ldtr = cpu_kmemoryread_w(task_base + 42);
 		iobase = 0;
+		t = 0;
+	}
+
+#if defined(DEBUG)
+	VERBOSE(("task_switch: current task"));
+	if (!task16) {
+		VERBOSE(("task_switch: CR3     = 0x%08x", CPU_CR3));
+	}
+	VERBOSE(("task_switch: eip     = 0x%08x", CPU_EIP));
+	VERBOSE(("task_switch: eflags  = 0x%08x", old_flags));
+	for (i = 0; i < CPU_REG_NUM; i++) {
+		VERBOSE(("task_switch: regs[%d] = 0x%08x", i, CPU_REGS_DWORD(i)));
+	}
+	for (i = 0; i < CPU_SEGREG_NUM; i++) {
+		VERBOSE(("task_switch: sreg[%d] = 0x%04x", i, CPU_REGS_SREG(i)));
+	}
+	VERBOSE(("task_switch: ldtr    = 0x%04x", CPU_LDTR));
+
+	VERBOSE(("task_switch: new task"));
+	if (!task16) {
+		VERBOSE(("task_switch: CR3     = 0x%08x", cr3));
+	}
+	VERBOSE(("task_switch: eip     = 0x%08x", eip));
+	VERBOSE(("task_switch: eflags  = 0x%08x", new_flags));
+	for (i = 0; i < CPU_REG_NUM; i++) {
+		VERBOSE(("task_switch: regs[%d] = 0x%08x", i, regs[i]));
 	}
+	for (i = 0; i < CPU_SEGREG_NUM; i++) {
+		VERBOSE(("task_switch: sreg[%d] = 0x%04x", i, sreg[i]));
+	}
+	VERBOSE(("task_switch: ldtr    = 0x%04x", ldtr));
+	if (!task16) {
+		VERBOSE(("task_switch: t       = 0x%04x", t));
+		VERBOSE(("task_switch: iobase  = 0x%04x", iobase));
+	}
+#endif
 
 	/* if IRET or JMP, clear busy flag in this task: need */
 	/* if IRET, clear NT_FLAG in current EFLAG: need */
@@ -223,7 +306,7 @@ task_switch(selector_t* task_sel, int ty
 		/*FALLTHROUGH*/
 	case TASK_SWITCH_JMP:
 		/* clear busy flags in current task */
-		CPU_SET_TASK_FREE(&CPU_TR_DESC);
+		CPU_SET_TASK_FREE(CPU_TR, &CPU_TR_DESC);
 		break;
 
 	case TASK_SWITCH_CALL:
@@ -236,36 +319,45 @@ task_switch(selector_t* task_sel, int ty
 		break;
 	}
 
-	/* save this task state in this task state segment ind */
+	/* save this task state in this task state segment */
 	if (!task16) {
-		cpu_lmemorywrite_d(cur_base + 28, CPU_CR3);
-		cpu_lmemorywrite_d(cur_base + 32, CPU_EIP);
-		cpu_lmemorywrite_d(cur_base + 36, old_flags);
+		cpu_kmemorywrite_d(cur_base + 32, CPU_EIP);
+		cpu_kmemorywrite_d(cur_base + 36, old_flags);
 		for (i = 0; i < CPU_REG_NUM; i++) {
-			cpu_lmemorywrite_d(cur_base + 40 + i * 4, CPU_REGS_DWORD(i));
+			cpu_kmemorywrite_d(cur_base + 40 + i * 4, CPU_REGS_DWORD(i));
 		}
-		for (i = 0; i < nsreg; i++) {
-			cpu_lmemorywrite_d(cur_base + 72 + i * 4, CPU_REGS_SREG(i));
+		for (i = 0; i < CPU_SEGREG_NUM; i++) {
+			cpu_kmemorywrite_w(cur_base + 72 + i * 4, CPU_REGS_SREG(i));
 		}
-		cpu_lmemorywrite_d(cur_base + 96, CPU_LDTR);
 	} else {
-		cpu_lmemorywrite_w(cur_base + 14, CPU_IP);
-		cpu_lmemorywrite_w(cur_base + 16, (WORD)old_flags);
+		cpu_kmemorywrite_w(cur_base + 14, CPU_IP);
+		cpu_kmemorywrite_w(cur_base + 16, (UINT16)old_flags);
 		for (i = 0; i < CPU_REG_NUM; i++) {
-			cpu_lmemorywrite_w(cur_base + 18 + i * 2, CPU_REGS_WORD(i));
+			cpu_kmemorywrite_w(cur_base + 18 + i * 2, CPU_REGS_WORD(i));
 		}
-		for (i = 0; i < nsreg; i++) {
-			cpu_lmemorywrite_w(cur_base + 34 + i * 2, CPU_REGS_SREG(i));
+		for (i = 0; i < CPU_SEGREG286_NUM; i++) {
+			cpu_kmemorywrite_w(cur_base + 34 + i * 2, CPU_REGS_SREG(i));
 		}
-		cpu_lmemorywrite_w(cur_base + 42, CPU_LDTR);
 	}
 
+#if defined(MORE_DEBUG)
+	{
+		UINT32 v;
+
+		VERBOSE(("task_switch: current task"));
+		for (i = 0; i < CPU_TR_DESC.u.seg.limit; i += 4) {
+			v = cpu_kmemoryread_d(cur_base + i);
+			VERBOSE(("task_switch: 0x%08x: %08x", cur_base + i, v));
+		}
+	}
+#endif
+
 	/* set back link selector */
 	switch (type) {
 	case TASK_SWITCH_CALL:
 	case TASK_SWITCH_INTR:
 		/* set back link selector */
-		cpu_lmemorywrite_d(task_base, CPU_TR);
+		cpu_kmemorywrite_w(task_base, CPU_TR);
 		break;
 	
 	case TASK_SWITCH_IRET:
@@ -280,7 +372,7 @@ task_switch(selector_t* task_sel, int ty
 
 	/* Now task switching! */
 
-	/* if CALL, INTR, set EFLAG image NT_FLAG */
+	/* if CALL, INTR, set EFLAGS image NT_FLAG */
 	/* if CALL, INTR, JMP set busy flag */
 	switch (type) {
 	case TASK_SWITCH_CALL:
@@ -289,12 +381,18 @@ task_switch(selector_t* task_sel, int ty
 		new_flags |= NT_FLAG;
 		/*FALLTHROUGH*/
 	case TASK_SWITCH_JMP:
-		CPU_SET_TASK_BUSY(&task_sel->desc);
+		CPU_SET_TASK_BUSY(task_sel->selector, &task_sel->desc);
 		break;
 	
 	case TASK_SWITCH_IRET:
-		/* Nothing to do */
-		/* XXX: if IRET, check busy flag is active? */
+		/* check busy flag is active */
+		if (task_sel->desc.valid) {
+			UINT32 h;
+			h = cpu_kmemoryread_d(task_sel->addr + 4);
+			if ((h & CPU_TSS_H_BUSY) == 0) {
+				ia32_panic("task_switch: new task is not busy");
+			}
+		}
 		break;
 
 	default:
@@ -310,81 +408,125 @@ task_switch(selector_t* task_sel, int ty
 	CPU_TR_DESC = task_sel->desc;
 
 	/* load task state (CR3, EFLAG, EIP, GPR, segreg, LDTR) */
-	if (CPU_STAT_PAGING) {
-		/* XXX setCR3()? */
-		CPU_CR3 = cr3 & 0xfffff018;
-		tlb_flush(FALSE);
+
+	/* set new CR3 */
+	if (!task16 && CPU_STAT_PAGING) {
+		set_CR3(cr3);
 	}
 
-	/* set new EFLAGS, EIP, GPR, segment register, LDTR */
-	set_eflags(new_flags, I_FLAG|IOPL_FLAG|RF_FLAG|VM_FLAG|VIF_FLAG|VIP_FLAG);
+	/* set new EIP, GPR */
 	CPU_PREV_EIP = CPU_EIP = eip;
+	CPU_PREFETCH_CLEAR();
 	for (i = 0; i < CPU_REG_NUM; i++) {
 		CPU_REGS_DWORD(i) = regs[i];
 	}
 	for (i = 0; i < CPU_SEGREG_NUM; i++) {
 		CPU_REGS_SREG(i) = sreg[i];
-		CPU_STAT_SREG_CLEAR(i);
+		CPU_STAT_SREG_INIT(i);
 	}
-	CPU_LDTR = ldtr;
-	CPU_LDTR_DESC.valid = 0;
 
-	/* load LDTR */
-	load_ldtr(ldtr, TS_EXCEPTION);
+	/* set new EFLAGS */
+#if defined(IA32_DONT_USE_SET_EFLAGS_FUNCTION)
+	CPU_EFLAG = new_flags;
+	CPU_OV = CPU_FLAG & O_FLAG;
+	CPU_TRAP = (CPU_FLAG & (I_FLAG|T_FLAG)) == (I_FLAG|T_FLAG);
+	if ((old_flags ^ CPU_EFLAG) & VM_FLAG) {
+		if (CPU_EFLAG & VM_FLAG) {
+			change_vm(1);
+		} else {
+			change_vm(0);
+		}
+	}
+#else
+	set_eflags(new_flags, I_FLAG|IOPL_FLAG|RF_FLAG|VM_FLAG|VIF_FLAG|VIP_FLAG);
+#endif
 
-	/* load CS */
-	rv = parse_selector(&cs_sel, sreg[CPU_CS_INDEX]);
-	if (rv < 0) {
-		EXCEPTION(TS_EXCEPTION, cs_sel.idx);
+	/* I/O deny bitmap */
+	if (!task16) {
+		if (iobase != 0 && iobase < task_sel->desc.u.seg.limit) {
+			CPU_STAT_IOLIMIT = (UINT16)(task_sel->desc.u.seg.limit - iobase);
+			CPU_STAT_IOADDR = task_sel->desc.u.seg.segbase + iobase;
+		} else {
+			CPU_STAT_IOLIMIT = 0;
+		}
+	} else {
+		CPU_STAT_IOLIMIT = 0;
+	}
+	VERBOSE(("task_switch: ioaddr = %08x, limit = %08x", CPU_STAT_IOADDR, CPU_STAT_IOLIMIT));
+
+#if defined(IA32_SUPPORT_DEBUG_REGISTER)
+	/* check resume flag */
+	if (CPU_EFLAG & RF_FLAG) {
+		CPU_STAT_BP_EVENT |= CPU_STAT_BP_EVENT_RF;
 	}
 
-	/* CS register must be code segment */
-	if (!cs_sel.desc.s || !cs_sel.desc.u.seg.c) {
-		EXCEPTION(TS_EXCEPTION, cs_sel.idx);
+	/* clear local break point flags */
+	CPU_DR7 &= ~(CPU_DR7_L(0)|CPU_DR7_L(1)|CPU_DR7_L(2)|CPU_DR7_L(3)|CPU_DR7_LE);
+	CPU_STAT_BP = 0;
+	for (i = 0; i < CPU_DEBUG_REG_INDEX_NUM; i++) {
+		if (CPU_DR7 & CPU_DR7_G(i)) {
+			CPU_STAT_BP |= (1 << i);
+		}
 	}
+#endif
 
-	/* check privilege level */
-	if (!cs_sel.desc.u.seg.ec) {
-		/* non-confirming code segment */
-		if (cs_sel.desc.dpl != cs_sel.rpl) {
+	/* load new LDTR */
+	load_ldtr(ldtr, TS_EXCEPTION);
+
+	/* set new segment register */
+	if (!CPU_STAT_VM86) {
+		/* clear segment descriptor cache */
+		for (i = 0; i < CPU_SEGREG_NUM; i++) {
+			CPU_STAT_SREG_CLEAR(i);
+		}
+
+		/* load CS */
+		rv = parse_selector(&cs_sel, sreg[CPU_CS_INDEX]);
+		if (rv < 0) {
+			VERBOSE(("task_switch: load CS failure (sel = 0x%04x, rv = %d)", sreg[CPU_CS_INDEX], rv));
 			EXCEPTION(TS_EXCEPTION, cs_sel.idx);
 		}
-	} else {
-		/* confirming code segment */
-		if (cs_sel.desc.dpl < cs_sel.rpl) {
+
+		/* CS register must be code segment */
+		if (!cs_sel.desc.s || !cs_sel.desc.u.seg.c) {
 			EXCEPTION(TS_EXCEPTION, cs_sel.idx);
 		}
-	}
 
-	/* CS segment is not present */
-	rv = selector_is_not_present(&cs_sel);
-	if (rv < 0) {
-		EXCEPTION(NP_EXCEPTION, cs_sel.idx);
-	}
+		/* check privilege level */
+		if (!cs_sel.desc.u.seg.ec) {
+			/* non-confirming code segment */
+			if (cs_sel.desc.dpl != cs_sel.rpl) {
+				EXCEPTION(TS_EXCEPTION, cs_sel.idx);
+			}
+		} else {
+			/* confirming code segment */
+			if (cs_sel.desc.dpl < cs_sel.rpl) {
+				EXCEPTION(TS_EXCEPTION, cs_sel.idx);
+			}
+		}
+
+		/* code segment is not present */
+		rv = selector_is_not_present(&cs_sel);
+		if (rv < 0) {
+			EXCEPTION(NP_EXCEPTION, cs_sel.idx);
+		}
 
-	/* Now loading CS register */
-	load_cs(cs_sel.selector, &cs_sel.desc, cs_sel.desc.dpl);
+		/* Now loading CS register */
+		load_cs(cs_sel.selector, &cs_sel.desc, cs_sel.desc.dpl);
 
-	/* load ES, SS, DS, FS, GS segment register */
-	for (i = 0; i < nsreg; i++) {
-		if (i != CPU_CS_INDEX) {
-			load_segreg(i, sreg[i], TS_EXCEPTION);
+		/* load ES, SS, DS, FS, GS segment register */
+		for (i = 0; i < CPU_SEGREG_NUM; i++) {
+			if (i != CPU_CS_INDEX) {
+				load_segreg(i, sreg[i], TS_EXCEPTION);
+			}
 		}
 	}
 
-	/* I/O deny bitmap */
-	if (!task16) {
-		if (task_sel->desc.u.seg.limit > iobase) {
-			CPU_STAT_IOLIMIT = task_sel->desc.u.seg.limit - iobase;
-			CPU_STAT_IOLIMIT *= 8;	/* ビット単位で保持しておく */
-			CPU_STAT_IOADDR = task_sel->desc.u.seg.segbase + iobase;
-		} else {
-			CPU_STAT_IOLIMIT = 0;
-		}
-	} else {
-		CPU_STAT_IOLIMIT = 0;
+	/* out of range */
+	if (CPU_EIP > CPU_STAT_CS_LIMIT) {
+		VERBOSE(("task_switch: new_ip is out of range. new_ip = %08x, limit = %08x", CPU_EIP, CPU_STAT_CS_LIMIT));
+		EXCEPTION(GP_EXCEPTION, 0);
 	}
 
-	/* running new task */
-	SET_EIP(eip);
+	VERBOSE(("task_switch: done."));
 }