Add Pentium II SYSENTER/SYSEXIT stub, add to debugger decompiler, add option to enable the instruction

src/cpu/core_normal.cpp

@@ -26,6 +26,8 @@
 
 bool CPU_RDMSR();
 bool CPU_WRMSR();
+bool CPU_SYSENTER();
+bool CPU_SYSEXIT();
 
 #define PRE_EXCEPTION { }
 

src/cpu/core_normal/prefix_0f.h

@@ -257,6 +257,18 @@
 			reg_eax=(uint32_t)(tsc&0xffffffff);
 		}
 		break;
+	CASE_0F_B(0x34)												/* SYSENTER */
+		{
+			if (CPU_ArchitectureType<CPU_ARCHTYPE_PENTIUMII) goto illegal_opcode;
+			if (!CPU_SYSENTER()) goto illegal_opcode;
+		}
+		break;
+	CASE_0F_B(0x35)												/* SYSEXIT */
+		{
+			if (CPU_ArchitectureType<CPU_ARCHTYPE_PENTIUMII) goto illegal_opcode;
+			if (!CPU_SYSEXIT()) goto illegal_opcode;
+		}
+		break;
 
 	// Pentium Pro Conditional Moves
 	CASE_0F_W(0x40)												/* CMOVO */

src/cpu/core_normal_286.cpp

@@ -26,6 +26,8 @@
 
 bool CPU_RDMSR();
 bool CPU_WRMSR();
+bool CPU_SYSENTER();
+bool CPU_SYSEXIT();
 
 #define PRE_EXCEPTION { }
 

src/cpu/core_prefetch.cpp

@@ -161,6 +161,8 @@ static uint32_t Fetchd() {
 
 bool CPU_RDMSR();
 bool CPU_WRMSR();
+bool CPU_SYSENTER();
+bool CPU_SYSEXIT();
 
 #define Push_16 CPU_Push16
 #define Push_32 CPU_Push32

src/cpu/core_prefetch_286.cpp

@@ -31,6 +31,8 @@ using namespace std;
 
 bool CPU_RDMSR();
 bool CPU_WRMSR();
+bool CPU_SYSENTER();
+bool CPU_SYSEXIT();
 
 #define PRE_EXCEPTION { }
 

src/cpu/core_simple.cpp

@@ -144,6 +144,8 @@ static INLINE uint32_t Fetchd() {
 
 bool CPU_RDMSR();
 bool CPU_WRMSR();
+bool CPU_SYSENTER();
+bool CPU_SYSEXIT();
 
 #include "instructions.h"
 #include "core_normal/support.h"

src/cpu/cpu.cpp

@@ -69,6 +69,7 @@ bool do_seg_limits = false;
 
 bool enable_fpu = true;
 bool enable_msr = true;
+bool enable_syscall = true;
 bool enable_cmpxchg8b = true;
 bool ignore_undefined_msr = true;
 bool report_fdiv_bug = false;
@@ -2956,6 +2957,7 @@ bool CPU_CPUID(void) {
 			reg_edx=0x00008011;	/* FPU+TimeStamp/RDTSC */
 			if (enable_msr) reg_edx |= 0x20; /* ModelSpecific/MSR */
 			if (enable_cmpxchg8b) reg_edx |= 0x100; /* CMPXCHG8B */
+			if (enable_syscall) reg_edx |= 0x800; /* SEP Fast System Call aka SYSENTER/SYSEXIT */
 		} else {
 			return false;
 		}
@@ -3516,7 +3518,8 @@ public:
 		cpu_rep_max=section->Get_int("interruptible rep string op");
 		ignore_undefined_msr=section->Get_bool("ignore undefined msr");
 		enable_msr=section->Get_bool("enable msr");
-        enable_cmpxchg8b=section->Get_bool("enable cmpxchg8b");
+		enable_syscall=section->Get_bool("enable syscall");
+		enable_cmpxchg8b=section->Get_bool("enable cmpxchg8b");
 		CPU_CycleUp=section->Get_int("cycleup");
 		CPU_CycleDown=section->Get_int("cycledown");
 		std::string core(section->Get_string("core"));
@@ -4096,6 +4099,19 @@ void CPU_ForceV86FakeIO_Out(Bitu port,Bitu val,Bitu len) {
 	reg_edx = old_edx;
 }
 
+/* pentium II fast system call */
+bool CPU_SYSENTER() {
+	if (!enable_syscall) return false;
+	LOG(LOG_CPU,LOG_NORMAL)("SYSENTER: UNIMPLEMENTED");
+	return false; /* TODO */
+}
+
+bool CPU_SYSEXIT() {
+	if (!enable_syscall) return false;
+	LOG(LOG_CPU,LOG_NORMAL)("SYSEXIT: UNIMPLEMENTED");
+	return false; /* TODO */
+}
+
 /* pentium machine-specific registers */
 bool CPU_RDMSR() {
 	if (!enable_msr) return false;

src/debug/debug_disasm.cpp

@@ -284,7 +284,7 @@ static char const *second[] = {
   0,                  0,                 0,                0,
 /* 3 */
   0,                  "rdtsc",           0,                0,
-  0,                  0,                 0,                0,
+  "sysenter",         "sysexit",         0,                0,
   0,                  0,                 0,                0,
   0,                  0,                 0,                0,
 /* 4 */

src/dosbox.cpp

@@ -2531,6 +2531,9 @@ void DOSBOX_SetupConfigSections(void) {
     Pbool->Set_help("Enable Pentium CMPXCHG8B instruction. Enable this explicitly if using software that uses this instruction.\n"
             "You must enable this option to run Windows ME because portions of the kernel rely on this instruction.");
 
+    Pbool = secprop->Add_bool("enable syscall",Property::Changeable::Always,true);
+    Pbool->Set_help("Allow SYSENTER/SYSEXIT instructions. This option is only meaningful when cputype=pentium_ii.\n");
+
     Pbool = secprop->Add_bool("ignore undefined msr",Property::Changeable::Always,false);
     Pbool->Set_help("Ignore RDMSR/WRMSR on undefined registers. Normally the CPU will fire an Invalid Opcode exception in that case.\n"
             "This option is off by default, enable if using software or drivers that assumes the presence of\n"