From 0e0f29420279642b21b4f848ba214ef5feeee4d1 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Sebastian=20Strohh=C3=A4cker?=
 <c2woody@users.sourceforge.net>
Date: Mon, 4 Jul 2005 20:20:19 +0000
Subject: [PATCH] better compatibility while in v86-mode (Strike Commander
 etc.)

Imported-from: https://svn.code.sf.net/p/dosbox/code-0/dosbox/trunk@2228
---
 include/cpu.h                   |  4 ++-
 src/cpu/core_normal/prefix_0f.h |  6 ++--
 src/cpu/cpu.cpp                 | 56 +++++++++++++++++++++++++--------
 src/dos/dos_execute.cpp         | 11 ++++---
 4 files changed, 57 insertions(+), 20 deletions(-)

diff --git a/include/cpu.h b/include/cpu.h
index ac6b6489..01783145 100644
--- a/include/cpu.h
+++ b/include/cpu.h
@@ -63,8 +63,10 @@ void CPU_ARPL(Bitu & dest_sel,Bitu src_sel);
 void CPU_LAR(Bitu selector,Bitu & ar);
 void CPU_LSL(Bitu selector,Bitu & limit);
 
-bool CPU_SET_CRX(Bitu cr,Bitu value);
+void CPU_SET_CRX(Bitu cr,Bitu value);
+bool CPU_WRITE_CRX(Bitu cr,Bitu value);
 Bitu CPU_GET_CRX(Bitu cr);
+bool CPU_READ_CRX(Bitu cr,Bit32u & retvalue);
 
 void CPU_SMSW(Bitu & word);
 Bitu CPU_LMSW(Bitu word);
diff --git a/src/cpu/core_normal/prefix_0f.h b/src/cpu/core_normal/prefix_0f.h
index ca5c7d58..4b5103cf 100644
--- a/src/cpu/core_normal/prefix_0f.h
+++ b/src/cpu/core_normal/prefix_0f.h
@@ -128,7 +128,9 @@
 			Bitu which=(rm >> 3) & 7;
 			if (rm >= 0xc0 ) {
 				GetEArd;
-				*eard=CPU_GET_CRX(which);
+				Bit32u crx_value;
+				if (CPU_READ_CRX(which,crx_value)) RUNEXCEPTION();
+				*eard=crx_value;
 			} else {
 				GetEAa;
 				LOG(LOG_CPU,LOG_ERROR)("MOV XXX,CR%d with non-register",which);
@@ -153,7 +155,7 @@
 			Bitu which=(rm >> 3) & 7;
 			if (rm >= 0xc0 ) {
 				GetEArd;
-				if (CPU_SET_CRX(which,*eard)) RUNEXCEPTION();
+				if (CPU_WRITE_CRX(which,*eard)) RUNEXCEPTION();
 			} else 	goto illegal_opcode;
 		}
 		break;
diff --git a/src/cpu/cpu.cpp b/src/cpu/cpu.cpp
index 61e53db5..ea886505 100644
--- a/src/cpu/cpu.cpp
+++ b/src/cpu/cpu.cpp
@@ -16,7 +16,7 @@
  *  Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  */
 
-/* $Id: cpu.cpp,v 1.70 2005-04-25 19:01:11 qbix79 Exp $ */
+/* $Id: cpu.cpp,v 1.71 2005-07-04 20:20:18 c2woody Exp $ */
 
 #include <assert.h>
 #include "dosbox.h"
@@ -82,7 +82,7 @@ void CPU_Core_Dyn_X86_Init(void);
 }
 #elif defined(CPU_CHECK_EXCEPT)
 #define CPU_CHECK_COND(cond,msg,exc,sel) {	\
-	if (cond) {
+	if (cond) {					\
 		CPU_Exception(exc,sel);		\
 		return;				\
 	}					\
@@ -158,10 +158,14 @@ bool CPU_STI(void) {
 }
 
 bool CPU_POPF(Bitu use32) {
-	if ((reg_flags & FLAG_VM) && (GETFLAG(IOPL)!=FLAG_IOPL))
+	if (cpu.pmode && GETFLAG(VM) && (GETFLAG(IOPL)!=FLAG_IOPL)) {
+		/* Not enough privileges to execute POPF */
 		return CPU_PrepareException(EXCEPTION_GP,0);
-	Bitu mask=cpu.cpl ? FMASK_NORMAL : FMASK_ALL;
-	if ((GETFLAG_IOPL<cpu.cpl) && !(reg_flags & FLAG_VM)) mask &= (~FLAG_IF);
+	}
+	Bitu mask=FMASK_ALL;
+	/* IOPL field can only be modified when CPL=0 or in real mode: */
+	if (cpu.pmode && (cpu.cpl>0)) mask &= (~FLAG_IOPL);
+	if (cpu.pmode && !GETFLAG(VM) && (GETFLAG_IOPL<cpu.cpl)) mask &= (~FLAG_IF);
 	if (use32)
 		CPU_SetFlags(CPU_Pop32(),mask);
 	else CPU_SetFlags(CPU_Pop16(),mask & 0xffff);
@@ -169,10 +173,12 @@ bool CPU_POPF(Bitu use32) {
 }
 
 bool CPU_PUSHF(Bitu use32) {
-	if ((reg_flags & FLAG_VM) && (GETFLAG(IOPL)!=FLAG_IOPL))
+	if (cpu.pmode && GETFLAG(VM) && (GETFLAG(IOPL)!=FLAG_IOPL)) {
+		/* Not enough privileges to execute PUSHF */
 		return CPU_PrepareException(EXCEPTION_GP,0);
+	}
 	if (use32) 
-		CPU_Push32(reg_flags & 0x00fcffff);
+		CPU_Push32(reg_flags & 0xfcffff);
 	else CPU_Push16(reg_flags);
 	return false;
 }
@@ -631,15 +637,14 @@ do_interrupt:
 
 void CPU_IRET(bool use32,Bitu oldeip) {
 	if (!cpu.pmode) {					/* RealMode IRET */
-realmode_iret:
 		if (use32) {
 			reg_eip=CPU_Pop32();
 			SegSet16(cs,CPU_Pop32());
-			CPU_SetFlagsd(CPU_Pop32());
+			CPU_SetFlags(CPU_Pop32(),FMASK_ALL);
 		} else {
 			reg_eip=CPU_Pop16();
 			SegSet16(cs,CPU_Pop16());
-			CPU_SetFlagsw(CPU_Pop16());
+			CPU_SetFlags(CPU_Pop16(),FMASK_ALL & 0xffff);
 		}
 		cpu.code.big=false;
 		return;
@@ -649,7 +654,21 @@ realmode_iret:
 				// win3.x e
 				CPU_Exception(EXCEPTION_GP,0);
 				return;
-			} else goto realmode_iret;
+			} else {
+				if (use32) {
+					reg_eip=CPU_Pop32();
+					SegSet16(cs,CPU_Pop32());
+					/* IOPL can not be modified in v86 mode by IRET */
+					CPU_SetFlags(CPU_Pop32(),FMASK_NORMAL|FLAG_NT);
+				} else {
+					reg_eip=CPU_Pop16();
+					SegSet16(cs,CPU_Pop16());
+					/* IOPL can not be modified in v86 mode by IRET */
+					CPU_SetFlags(CPU_Pop16(),FMASK_NORMAL|FLAG_NT);
+				}
+				cpu.code.big=false;
+				return;
+			}
 		}
 		/* Check if this is task IRET */	
 		if (GETFLAG(NT)) {
@@ -1380,12 +1399,12 @@ void CPU_SIDT(Bitu & limit,Bitu & base) {
 }
 
 
-bool CPU_SET_CRX(Bitu cr,Bitu value) {
+void CPU_SET_CRX(Bitu cr,Bitu value) {
 	switch (cr) {
 	case 0:
 		{
 			Bitu changed=cpu.cr0 ^ value;		
-			if (!changed) return false;
+			if (!changed) return;
 			cpu.cr0=value;
 			if (value & CR0_PROTECTION) {
 				cpu.pmode=true;
@@ -1408,6 +1427,11 @@ bool CPU_SET_CRX(Bitu cr,Bitu value) {
 		LOG(LOG_CPU,LOG_ERROR)("Unhandled MOV CR%d,%X",cr,value);
 		break;
 	}
+}
+
+bool CPU_WRITE_CRX(Bitu cr,Bitu value) {
+	if (cpu.pmode && GETFLAG(VM)) return CPU_PrepareException(EXCEPTION_GP,0);
+	else CPU_SET_CRX(cr,value);
 	return false;
 }
 
@@ -1426,6 +1450,12 @@ Bitu CPU_GET_CRX(Bitu cr) {
 	return 0;
 }
 
+bool CPU_READ_CRX(Bitu cr,Bit32u & retvalue) {
+	if (cpu.pmode && GETFLAG(VM)) return CPU_PrepareException(EXCEPTION_GP,0);
+	retvalue=CPU_GET_CRX(cr);
+	return false;
+}
+
 
 void CPU_SMSW(Bitu & word) {
 	word=cpu.cr0;
diff --git a/src/dos/dos_execute.cpp b/src/dos/dos_execute.cpp
index 26c2d407..ba686254 100644
--- a/src/dos/dos_execute.cpp
+++ b/src/dos/dos_execute.cpp
@@ -16,7 +16,7 @@
  *  Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  */
 
-/* $Id: dos_execute.cpp,v 1.45 2005-02-10 10:20:51 qbix79 Exp $ */
+/* $Id: dos_execute.cpp,v 1.46 2005-07-04 20:20:19 c2woody Exp $ */
 
 #include <string.h>
 #include <ctype.h>
@@ -131,7 +131,7 @@ bool DOS_Terminate(bool tsr) {
 	/* Set the CS:IP stored in int 0x22 back on the stack */
 	mem_writew(SegPhys(ss)+reg_sp+0,RealOff(old22));
 	mem_writew(SegPhys(ss)+reg_sp+2,RealSeg(old22));
-	mem_writew(SegPhys(ss)+reg_sp+4,0x200); //stack isn't preserved
+	mem_writew(SegPhys(ss)+reg_sp+4,reg_flags&(~FLAG_CF));
 	// Free memory owned by process
 	if (!tsr) DOS_FreeProcessMemory(mempsp);
 	DOS_UpdatePSPName();
@@ -376,10 +376,13 @@ bool DOS_Execute(char * name,PhysPt block_pt,Bit8u flags) {
 		reg_sp-=6;
 		mem_writew(SegPhys(ss)+reg_sp+0,RealOff(csip));
 		mem_writew(SegPhys(ss)+reg_sp+2,RealSeg(csip));
-		mem_writew(SegPhys(ss)+reg_sp+4,0x200);
+		/* DOS starts programs with a RETF, so our IRET
+		   should not modify the flags (e.g. IOPL in v86 mode) */
+		mem_writew(SegPhys(ss)+reg_sp+4,reg_flags&(~FLAG_CF));
 		/* Setup the rest of the registers */
 		reg_ax=0;reg_si=0x100;
-		reg_cx=reg_dx=reg_bx=reg_di=reg_bp=0;
+		reg_cx=reg_dx=reg_bx=reg_di=0;
+		reg_bp=0x91c;	/* DOS internal stack begin relict */
 		SegSet16(ds,pspseg);SegSet16(es,pspseg);
 #if C_DEBUG		
 		/* Started from debug.com, then set breakpoint at start */