Patch by Jan Klötzke:

* In vm86 mode CS will have arbitrary values so we check for both USER_CODE_SEG
  and the VM flag in EFLAGS. This is also done when entering interrupt gates.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@25607 a95241bf-73f2-0310-859d-f6bbb57e9c96

headers/private/kernel/arch/x86/arch_cpu.h

@@ -157,6 +157,10 @@ struct iframe {
 	uint32 user_ss;
 };
 
+#define IFRAME_IS_USER(f) ( ((f)->cs == USER_CODE_SEG) \
+                            || (((f)->flags & 0x20000) != 0 ))
+#define IFRAME_IS_VM86(f) ( ((f)->flags & 0x20000) != 0 )
+
 // features
 enum x86_feature_type {
 	FEATURE_COMMON = 0,     // cpuid eax=1, ecx register

src/system/kernel/arch/x86/arch_int.c

@@ -401,7 +401,7 @@ unexpected_exception(struct iframe* frame)
 			return;
 	}
 
-	if (frame->cs == USER_CODE_SEG) {
+	if (IFRAME_IS_USER(frame)) {
 		enable_interrupts();
 
 		if (user_debug_exception_occurred(type, signal))

src/system/kernel/arch/x86/arch_thread.cpp

@@ -143,7 +143,7 @@ i386_get_user_iframe(void)
 	struct iframe* frame = get_current_iframe();
 
 	while (frame != NULL) {
-		if (frame->cs == USER_CODE_SEG)
+		if (IFRAME_IS_USER(frame))
 			return frame;
 		frame = get_previous_iframe(frame);
 	}

src/system/kernel/arch/x86/arch_user_debugger.cpp

@@ -778,7 +778,7 @@ x86_handle_debug_exception(struct iframe *frame)
 
 	TRACE(("i386_handle_debug_exception(): DR6: %lx, DR7: %lx\n", dr6, dr7));
 
-	if (frame->cs != USER_CODE_SEG) {
+	if (!IFRAME_IS_USER(frame)) {
 		panic("debug exception in kernel mode: dr6: 0x%lx, dr7: 0x%lx", dr6,
 			dr7);
 		return;
@@ -850,7 +850,7 @@ x86_handle_breakpoint_exception(struct iframe *frame)
 {
 	TRACE(("i386_handle_breakpoint_exception()\n"));
 
-	if (frame->cs != USER_CODE_SEG) {
+	if (!IFRAME_IS_USER(frame)) {
 		panic("breakpoint exception in kernel mode");
 		return;
 	}