[RFC 2/6] Replace all checks to USER_CODE_SEG by IFRAME_IS_USER macro.

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.
---
 headers/private/kernel/arch/x86/arch_cpu.h        |    4 ++++
 src/system/kernel/arch/x86/arch_int.c             |    2 +-
 src/system/kernel/arch/x86/arch_interrupts.S      |    2 ++
 src/system/kernel/arch/x86/arch_thread.cpp        |    2 +-
 src/system/kernel/arch/x86/arch_user_debugger.cpp |    4 ++--
 5 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/headers/private/kernel/arch/x86/arch_cpu.h b/headers/private/kernel/arch/x86/arch_cpu.h
index 803edc6..11e412f 100644
--- a/headers/private/kernel/arch/x86/arch_cpu.h
+++ b/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
diff --git a/src/system/kernel/arch/x86/arch_int.c b/src/system/kernel/arch/x86/arch_int.c
index c612ec6..4d2b472 100644
--- a/src/system/kernel/arch/x86/arch_int.c
+++ b/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))
diff --git a/src/system/kernel/arch/x86/arch_interrupts.S b/src/system/kernel/arch/x86/arch_interrupts.S
index ace4dd5..1f00a63 100644
--- a/src/system/kernel/arch/x86/arch_interrupts.S
+++ b/src/system/kernel/arch/x86/arch_interrupts.S
@@ -248,6 +248,8 @@ int_bottom:
 
 	cmp		$USER_CODE_SEG, IFRAME_cs(%ebp)
 	je		int_bottom_user
+	testl	$0x20000, IFRAME_flags(%ebp)	// VM86 mode
+	jnz		int_bottom_user
 
 	// disable interrupts -- the handler will enable them, if necessary
 	cli
diff --git a/src/system/kernel/arch/x86/arch_thread.cpp b/src/system/kernel/arch/x86/arch_thread.cpp
index 3b4f5c0..d9ad8ff 100644
--- a/src/system/kernel/arch/x86/arch_thread.cpp
+++ b/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);
 	}
diff --git a/src/system/kernel/arch/x86/arch_user_debugger.cpp b/src/system/kernel/arch/x86/arch_user_debugger.cpp
index 66ec93a..7d9b70f 100644
--- a/src/system/kernel/arch/x86/arch_user_debugger.cpp
+++ b/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;
 	}
-- 
1.5.4.2


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