From 814b2d0009da73b56c6def5d70a9dd97c7b17e2e Mon Sep 17 00:00:00 2001
From: John Hodge <tpg@prelude.mutabah.net>
Date: Fri, 23 Apr 2010 19:53:02 +0800
Subject: [PATCH] Fixes to VM8086 handler to remove operand size errors.

---
 Kernel/Makefile.BuildNum                    |  2 +-
 Kernel/arch/x86/Makefile                    |  2 +-
 Kernel/arch/x86/desctab.asm                 | 38 +----------
 Kernel/arch/x86/kpanic.c                    |  4 +-
 Kernel/arch/x86/mm_virt.c                   |  2 +-
 Kernel/arch/x86/proc.c                      | 14 ++++
 Kernel/arch/x86/start.asm                   | 25 -------
 Kernel/arch/x86/vm8086.c                    | 57 ++++++++++++----
 Kernel/include/syscalls.h                   |  4 +-
 Kernel/include/syscalls.inc.asm             |  2 +-
 Kernel/include/threads.h                    | 11 ++-
 Kernel/syscalls.c                           |  6 ++
 Kernel/syscalls.lst                         |  2 +-
 Kernel/threads.c                            | 74 +++++++++------------
 Modules/Display/VESA/main.c                 | 18 +++--
 Usermode/Libraries/libacess.so_src/core.asm |  2 +-
 Usermode/Libraries/libc.so_src/stub.c       |  9 +++
 Usermode/include/sys/sys.h                  |  2 +
 18 files changed, 141 insertions(+), 133 deletions(-)

diff --git a/Kernel/Makefile.BuildNum b/Kernel/Makefile.BuildNum
index 620c1bbd..ce0a54c7 100644
--- a/Kernel/Makefile.BuildNum
+++ b/Kernel/Makefile.BuildNum
@@ -1 +1 @@
-BUILD_NUM = 1982
+BUILD_NUM = 2027
diff --git a/Kernel/arch/x86/Makefile b/Kernel/arch/x86/Makefile
index c52e369b..0c442882 100644
--- a/Kernel/arch/x86/Makefile
+++ b/Kernel/arch/x86/Makefile
@@ -31,5 +31,5 @@ endif
 
 A_OBJ  = start.ao main.o lib.o desctab.ao errors.o irq.o
 A_OBJ += mm_phys.o mm_virt.o
-A_OBJ += proc.o time.o vm8086.o
+A_OBJ += proc.o proc.ao time.o vm8086.o
 A_OBJ += kpanic.o
diff --git a/Kernel/arch/x86/desctab.asm b/Kernel/arch/x86/desctab.asm
index 43bd8e4c..27b7bb1a 100644
--- a/Kernel/arch/x86/desctab.asm
+++ b/Kernel/arch/x86/desctab.asm
@@ -190,6 +190,7 @@ DEF_SYSCALL	0xAC	; Acess System Call
 ; IRQs
 ; - Timer
 [global Isr240]
+[extern SchedulerBase]
 Isr240:
 	push 0
 	jmp SchedulerBase
@@ -281,40 +282,3 @@ IRQCommon:
 	popa
 	add esp, 8	; Error Code and ID
 	iret
-
-; --------------
-; Task Scheduler
-; --------------
-[extern Proc_Scheduler]
-SchedulerBase:
-	pusha
-	push ds
-	push es
-	push fs
-	push gs
-	
-	mov ax, 0x10
-	mov ds, ax
-	mov es, ax
-	mov fs, ax
-	mov gs, ax
-	
-	mov eax, [esp+12*4]	; CPU Number
-	push eax	; Pus as argument
-	
-	call Proc_Scheduler
-	
-	add esp, 4	; Remove Argument
-	
-	pop gs
-	pop fs
-	pop es
-	pop ds
-
-	mov dx, 0x20
-	mov al, 0x20
-	out dx, al		; ACK IRQ
-	popa
-	add esp, 4	; CPU ID
-	; No Error code / int num
-	iret
diff --git a/Kernel/arch/x86/kpanic.c b/Kernel/arch/x86/kpanic.c
index 1972fd3b..798c5139 100644
--- a/Kernel/arch/x86/kpanic.c
+++ b/Kernel/arch/x86/kpanic.c
@@ -59,7 +59,9 @@ void KernelPanic_SetMode()
 {
 	 int	i;
 	
-	// Some routines call this function twice, let's avoid that, shall we?
+	// This function is called by Panic(), but MM_PageFault and the
+	// CPU exception handers also call it, so let's not clear the screen
+	// twice
 	if( giKP_Pos )	return ;
 	
 	// Restore VGA 0xB8000 text mode
diff --git a/Kernel/arch/x86/mm_virt.c b/Kernel/arch/x86/mm_virt.c
index db89cc14..f2be750f 100644
--- a/Kernel/arch/x86/mm_virt.c
+++ b/Kernel/arch/x86/mm_virt.c
@@ -1013,7 +1013,7 @@ void MM_UnmapHWPages(tVAddr VAddr, Uint Number)
 	
 	for( j = 0; j < Number; j++ )
 	{
-		MM_DerefPhys( gaPageTable[ (HW_MAP_ADDR >> 12) + i + j ] );
+		MM_DerefPhys( gaPageTable[ (HW_MAP_ADDR >> 12) + i + j ] & ~0xFFF );
 		gaPageTable[ (HW_MAP_ADDR >> 12) + i + j ] = 0;
 	}
 	
diff --git a/Kernel/arch/x86/proc.c b/Kernel/arch/x86/proc.c
index 62980674..e9884161 100644
--- a/Kernel/arch/x86/proc.c
+++ b/Kernel/arch/x86/proc.c
@@ -39,6 +39,7 @@ extern tThread	*Threads_GetNextToRun(int CPU);
 extern void	Threads_Dump();
 extern tThread	*Threads_CloneTCB(Uint *Err, Uint Flags);
 extern void	Isr8();	// Double Fault
+extern void	Proc_AlterUserReturnAddr();
 
 // === PROTOTYPES ===
 void	ArchThreads_Init();
@@ -51,6 +52,7 @@ tThread	*Proc_GetCurThread();
 void	Proc_ChangeStack();
  int	Proc_Clone(Uint *Err, Uint Flags);
 void	Proc_StartProcess(Uint16 SS, Uint Stack, Uint Flags, Uint16 CS, Uint IP);
+void	Proc_CallFaultHandler(tThread *Thread);
 void	Proc_Scheduler();
 
 // === GLOBALS ===
@@ -693,6 +695,18 @@ int Proc_Demote(Uint *Err, int Dest, tRegs *Regs)
 	return 0;
 }
 
+/**
+ * \brief Calls a signal handler in user mode
+ * \note Used for signals
+ */
+void Proc_CallFaultHandler(tThread *Thread)
+{
+	// Rewinds the stack and calls the user function
+	// Never returns
+	__asm__ __volatile__ ("mov %0, %%ebp;\n\tcall Proc_AlterUserReturnAddr" :: "r"(Thread->FaultHandler));
+	for(;;);
+}
+
 /**
  * \fn void Proc_Scheduler(int CPU)
  * \brief Swap current thread and clears dead threads
diff --git a/Kernel/arch/x86/start.asm b/Kernel/arch/x86/start.asm
index d9a1e500..b98a0165 100644
--- a/Kernel/arch/x86/start.asm
+++ b/Kernel/arch/x86/start.asm
@@ -168,31 +168,6 @@ CallWithArgArray:
 	pop ebp
 	ret
 
-[extern Proc_Clone]
-[extern Threads_Exit]
-[global SpawnTask]
-SpawnTask:
-	; Call Proc_Clone with Flags=0
-	xor eax, eax
-	push eax
-	push eax
-	call Proc_Clone
-	add esp, 8	; Remove arguments from stack
-	
-	test eax, eax
-	jnz .parent
-	
-	; In child, so now set up stack frame
-	mov ebx, [esp+4]	; Child Function
-	mov edx, [esp+8]	; Argument
-	; Child
-	push edx	; Argument
-	call ebx	; Function
-	call Threads_Exit	; Kill Thread
-	
-.parent:
-	ret
-
 [section .initpd]
 [global gaInitPageDir]
 [global gaInitPageTable]
diff --git a/Kernel/arch/x86/vm8086.c b/Kernel/arch/x86/vm8086.c
index 8ef7453e..1816eacf 100644
--- a/Kernel/arch/x86/vm8086.c
+++ b/Kernel/arch/x86/vm8086.c
@@ -13,12 +13,14 @@
 #define VM8086_STACK_OFS	0x0AFE
 enum eVM8086_Opcodes
 {
-	VM8086_OP_PUSHF	= 0x9C,
-	VM8086_OP_POPF	= 0x9D,
-	VM8086_OP_INT_I	= 0xCD,
-	VM8086_OP_IRET	= 0xCF,
-	VM8086_OP_IN_AD	= 0xEC,
-	VM8086_OP_IN_ADX= 0xED
+	VM8086_OP_PUSHF   = 0x9C,
+	VM8086_OP_POPF    = 0x9D,
+	VM8086_OP_INT_I   = 0xCD,
+	VM8086_OP_IRET    = 0xCF,
+	VM8086_OP_IN_AD   = 0xEC,
+	VM8086_OP_IN_ADX  = 0xED,
+	VM8086_OP_OUT_AD  = 0xEE,
+	VM8086_OP_OUT_ADX = 0xEF
 };
 #define VM8086_PAGES_PER_INST	4
 
@@ -45,13 +47,16 @@ MODULE_DEFINE(0, 0x100, VM8086, VM8086_Install, NULL, NULL);
 tSpinlock	glVM8086_Process;
 tPID	gVM8086_WorkerPID;
 tTID	gVM8086_CallingThread;
-tVM8086	* volatile gpVM8086_State;
+tVM8086	* volatile gpVM8086_State = (void*)-1;	// Set to -1 to avoid race conditions
 
 // === FUNCTIONS ===
 int VM8086_Install(char **Arguments)
 {
 	tPID	pid;	
 	
+	// Lock to avoid race conditions
+	LOCK( &glVM8086_Process );
+	
 	// Create BIOS Call process
 	pid = Proc_Clone(NULL, CLONE_VM);
 	if(pid == -1)
@@ -139,6 +144,11 @@ void VM8086_GPF(tRegs *Regs)
 	if(Regs->eip == VM8086_MAGIC_IP && Regs->cs == VM8086_MAGIC_CS
 	&& Threads_GetPID() == gVM8086_WorkerPID)
 	{
+		if( gpVM8086_State == (void*)-1 ) {
+			Log_Log("VM8086", "Worker thread ready and waiting");
+			RELEASE( &glVM8086_Process );	// Release lock obtained in VM8086_Install
+			gpVM8086_State = NULL;
+		}
 		if( gpVM8086_State ) {
 			gpVM8086_State->AX = Regs->eax;	gpVM8086_State->CX = Regs->ecx;
 			gpVM8086_State->DX = Regs->edx;	gpVM8086_State->BX = Regs->ebx;
@@ -176,7 +186,7 @@ void VM8086_GPF(tRegs *Regs)
 		return ;
 	}
 	
-	opcode = *(Uint8*)( KERNEL_BASE + (Regs->cs*16) + (Regs->eip) );
+	opcode = *(Uint8*)( (Regs->cs*16) + (Regs->eip) );
 	Regs->eip ++;
 	switch(opcode)
 	{
@@ -237,13 +247,13 @@ void VM8086_GPF(tRegs *Regs)
 		#endif
 		break;
 		
-	case 0xEE:	//OUT DX, AL
+	case VM8086_OP_OUT_AD:	//OUT DX, AL
 		outb(Regs->edx&0xFFFF, Regs->eax&0xFF);
 		#if TRACE_EMU
 		Log_Debug("VM8086", "Emulated OUT DX, AL (*0x%04x = 0x%02x)\n", Regs->edx&0xFFFF, Regs->eax&0xFF);
 		#endif
 		break;
-	case 0xEF:	//OUT DX, AX
+	case VM8086_OP_OUT_ADX:	//OUT DX, AX
 		outw(Regs->edx&0xFFFF, Regs->eax&0xFFFF);
 		#if TRACE_EMU
 		Log_Debug("VM8086", "Emulated OUT DX, AX (*0x%04x = 0x%04x)\n", Regs->edx&0xFFFF, Regs->eax&0xFFFF);
@@ -257,8 +267,31 @@ void VM8086_GPF(tRegs *Regs)
 		break;
 	
 	case 0x66:
-		Log_Warning("VM8086", "Code at %04x:%04x attempted to use an operand override, ignored",
-			Regs->cs, Regs->eip);
+		opcode = *(Uint8*)( (Regs->cs*16) + (Regs->eip&0xFFFF));
+		switch( opcode )
+		{
+		case VM8086_OP_IN_ADX:	//IN AX, DX
+			Regs->eax = ind(Regs->edx&0xFFFF);
+			#if TRACE_EMU
+			Log_Debug("VM8086", "Emulated IN EAX, DX (Port 0x%x)\n", Regs->edx&0xFFFF);
+			#endif
+			break;
+		case VM8086_OP_OUT_ADX:	//OUT DX, AX
+			outd(Regs->edx&0xFFFF, Regs->eax);
+			#if TRACE_EMU
+			Log_Debug("VM8086", "Emulated OUT DX, EAX (*0x%04x = 0x%08x)\n", Regs->edx&0xFFFF, Regs->eax);
+			#endif
+			break;
+		default:
+			Log_Error("VM8086", "Error - Unknown opcode 66 %02x caused a GPF at %04x:%04x",
+				Regs->cs, Regs->eip,
+				opcode
+				);
+			// Force an end to the call
+			Regs->cs = VM8086_MAGIC_CS;
+			Regs->eip = VM8086_MAGIC_IP;
+			break;
+		}
 		break;
 	
 	default:
diff --git a/Kernel/include/syscalls.h b/Kernel/include/syscalls.h
index fb9a2ff6..0007dc1c 100644
--- a/Kernel/include/syscalls.h
+++ b/Kernel/include/syscalls.h
@@ -9,7 +9,7 @@ enum eSyscalls {
 	SYS_EXIT,	// 0 - Kill this thread
 	SYS_CLONE,	// 1 - Create a new thread
 	SYS_KILL,	// 2 - Send a signal
-	SYS_SIGNAL,	// 3 - Set signal Handler
+	SYS_SETFAULTHANDLER,	// 3 - Set signal Handler
 	SYS_YIELD,	// 4 - Yield remainder of timestamp
 	SYS_SLEEP,	// 5 - Sleep until messaged or signaled
 	SYS_WAIT,	// 6 - Wait for a time or a message
@@ -63,7 +63,7 @@ enum eSyscalls {
 };
 
 static const char *cSYSCALL_NAMES[] = {
-	"SYS_EXIT","SYS_CLONE","SYS_KILL","SYS_SIGNAL","SYS_YIELD","SYS_SLEEP",
+	"SYS_EXIT","SYS_CLONE","SYS_KILL","SYS_SETFAULTHANDLER","SYS_YIELD","SYS_SLEEP",
 	"SYS_WAIT","SYS_WAITTID","SYS_SETNAME","SYS_GETNAME","SYS_GETTID","SYS_GETPID",
 	"SYS_SETPRI","SYS_SENDMSG","SYS_GETMSG","SYS_GETTIME","SYS_SPAWN","SYS_EXECVE",
 	"SYS_LOADBIN","SYS_UNLOADBIN","SYS_LOADMOD","","","",
diff --git a/Kernel/include/syscalls.inc.asm b/Kernel/include/syscalls.inc.asm
index a379deb1..bd59af83 100644
--- a/Kernel/include/syscalls.inc.asm
+++ b/Kernel/include/syscalls.inc.asm
@@ -5,7 +5,7 @@
 %define SYS_EXIT	0	; Kill this thread
 %define SYS_CLONE	1	; Create a new thread
 %define SYS_KILL	2	; Send a signal
-%define SYS_SIGNAL	3	; Set signal Handler
+%define SYS_SETFAULTHANDLER	3	; Set signal Handler
 %define SYS_YIELD	4	; Yield remainder of timestamp
 %define SYS_SLEEP	5	; Sleep until messaged or signaled
 %define SYS_WAIT	6	; Wait for a time or a message
diff --git a/Kernel/include/threads.h b/Kernel/include/threads.h
index b55fe0e0..28d669d2 100644
--- a/Kernel/include/threads.h
+++ b/Kernel/include/threads.h
@@ -17,11 +17,13 @@ typedef struct sMessage
 typedef struct sThread
 {
 	// --- threads.c's
+	//  0
 	struct sThread	*Next;	//!< Next thread in list
 	tSpinlock	IsLocked;	//!< Thread's spinlock
 	volatile int	Status;		//!< Thread Status
 	 int	RetStatus;	//!< Return Status
 	
+	// 16
 	Uint	TID;	//!< Thread ID
 	Uint	TGID;	//!< Thread Group (Process)
 	Uint	PTID;	//!< Parent Thread ID
@@ -29,19 +31,22 @@ typedef struct sThread
 	char	*ThreadName;	//!< Name of thread
 	
 	// --- arch/proc.c's responsibility
+	// 40
 	//! Kernel Stack Base
 	tVAddr	KernelStack;
 	
+	// 44 (x86)
 	//! Memory Manager State
 	tMemoryState	MemState;
 	
+	// 48 (x86)
 	//! State on task switch
 	tTaskState	SavedState;
 	
 	// --- threads.c's
-	 int	CurSignal;	//!< Signal currently being handled (0 for none)
-	tVAddr	SignalHandlers[NSIG];	//!< Signal Handler List
-	tTaskState	SignalState;	//!< Saved state for signal handler
+	// 60
+	 int	CurFaultNum;	//!< Current fault number, 0: none
+	tVAddr	FaultHandler;	//!< Fault Handler
 	
 	tMsg * volatile	Messages;	//!< Message Queue
 	tMsg	*LastMessage;	//!< Last Message (speeds up insertion)
diff --git a/Kernel/syscalls.c b/Kernel/syscalls.c
index 34567976..b49b4d6c 100644
--- a/Kernel/syscalls.c
+++ b/Kernel/syscalls.c
@@ -32,6 +32,7 @@ extern tUID	Threads_GetUID();
 extern int	Threads_SetUID(Uint *errno, tUID ID);
 extern tGID	Threads_GetGID();
 extern int	Threads_SetGID(Uint *errno, tGID ID);
+extern int	Threads_SetFaultHandler(Uint Handler);
 
 // === PROTOTYPES ===
  int	Syscall_ValidString(Uint Addr);
@@ -60,6 +61,11 @@ void SyscallHandler(tSyscallRegs *Regs)
 	// -- Yield current timeslice
 	case SYS_YIELD:	Threads_Yield();	break;
 	
+	// -- Set Error Handler
+	case SYS_SETFAULTHANDLER:
+		Threads_SetFaultHandler(Regs->Arg1);
+		break;
+	
 	// -- Clone the current thread
 	case SYS_CLONE:
 		// Call clone system call
diff --git a/Kernel/syscalls.lst b/Kernel/syscalls.lst
index c5978bea..dde278cd 100644
--- a/Kernel/syscalls.lst
+++ b/Kernel/syscalls.lst
@@ -3,7 +3,7 @@
 SYS_EXIT	Kill this thread
 SYS_CLONE	Create a new thread
 SYS_KILL	Send a signal
-SYS_SIGNAL	Set signal Handler
+SYS_SETFAULTHANDLER	Set signal Handler
 SYS_YIELD	Yield remainder of timestamp
 SYS_SLEEP	Sleep until messaged or signaled
 SYS_WAIT	Wait for a time or a message
diff --git a/Kernel/threads.c b/Kernel/threads.c
index 96a38dac..f726f275 100644
--- a/Kernel/threads.c
+++ b/Kernel/threads.c
@@ -22,6 +22,7 @@ extern void	ArchThreads_Init();
 extern void	Proc_Start();
 extern tThread	*Proc_GetCurThread();
 extern int	Proc_Clone(Uint *Err, Uint Flags);
+extern void	Proc_CallFaultHandler(tThread *Thread);
 
 // === PROTOTYPES ===
 void	Threads_Init();
@@ -62,7 +63,7 @@ tThread	gThreadZero = {
 	{0},	// Saved State
 	{0},	// VM State
 	
-	0, {0}, {0},	// Signal State
+	0, 0,	// Current Fault, Fault Handler
 	
 	NULL, NULL,	// Messages, Last Message
 	DEFAULT_QUANTUM, DEFAULT_QUANTUM,	// Quantum, Remaining
@@ -201,12 +202,8 @@ tThread *Threads_CloneTCB(Uint *Err, Uint Flags)
 	new->NumTickets = cur->NumTickets;
 	
 	// Set Signal Handlers
-	new->CurSignal = 0;
-	if(Flags & CLONE_VM)
-		memset(new->SignalHandlers, 0, sizeof(new->SignalHandlers));
-	else
-		memcpy(new->SignalHandlers, cur->SignalHandlers, sizeof(new->SignalHandlers));
-	memset(&new->SignalState, 0, sizeof(tTaskState));
+	new->CurFaultNum = 0;
+	new->FaultHandler = cur->FaultHandler;
 	
 	for( i = 0; i < NUM_CFG_ENTRIES; i ++ )
 	{
@@ -566,57 +563,50 @@ void Threads_AddActive(tThread *Thread)
 	RELEASE( &giThreadListLock );
 }
 
-#if 0
 /**
- * \fn void Threads_SetSignalHandler(int Num, void *Handler)
+ * \fn void Threads_SetSignalHandler(Uint Handler)
  * \brief Sets the signal handler for a signal
  */
-void Threads_SetSignalHandler(int Num, void *Handler)
-{
-	if(Num < 0 || Num >= NSIG)	return;
-	
-	gCurrentThread->SignalHandlers[Num] = Handler;
+void Threads_SetFaultHandler(Uint Handler)
+{	
+	Log_Log("Threads", "Threads_SetFaultHandler: Handler = %p", Handler);
+	Proc_GetCurThread()->FaultHandler = Handler;
 }
 
 /**
- * \fn void Threads_SendSignal(int TID, int Num)
- * \brief Send a signal to a thread
+ * \fn void Threads_Fault(int Num)
+ * \brief Calls a fault handler
  */
-void Threads_SendSignal(int TID, int Num)
+void Threads_Fault(int Num)
 {
-	tThread	*thread = Proc_GetThread(TID);
-	void	*handler;
+	tThread	*thread = Proc_GetCurThread();
+	
+	Log_Log("Threads", "Threads_Fault: thread = %p", thread);
 	
 	if(!thread)	return ;
 	
-	handler = thread->SignalHandlers[Num];
+	Log_Log("Threads", "Threads_Fault: thread->FaultHandler = %p", thread->FaultHandler);
 	
-	// Panic?
-	if(handler == SIG_ERR) {
-		Proc_Kill(TID);
+	switch(thread->FaultHandler)
+	{
+	case 0:	// Panic?
+		Threads_Kill(thread, -1);
+		HALT();
 		return ;
-	}
-	// Dump Core?
-	if(handler == -2) {
-		Proc_Kill(TID);
+	case 1:	// Dump Core?
+		Threads_Kill(thread, -1);
+		HALT();
 		return ;
 	}
-	// Ignore?
-	if(handler == -2)	return;
-	
-	// Check the type and handle if the thread is already in a signal
-	if(thread->CurSignal != 0) {
-		if(Num < _SIGTYPE_FATAL)
-			Proc_Kill(TID);
-		} else {
-			while(thread->CurSignal != 0)
-				Proc_Yield();
-		}
+	
+	// Double Fault? Oh, F**k
+	if(thread->CurFaultNum != 0) {
+		Threads_Kill(thread, -1);	// For now, just kill
+		HALT();
 	}
 	
-	//TODO: 
+	Proc_CallFaultHandler(thread);
 }
-#endif
 
 // --- Process Structure Access Functions ---
 tPID Threads_GetPID()
@@ -747,9 +737,9 @@ tThread *Threads_GetNextToRun(int CPU)
  */
 void Threads_SegFault(tVAddr Addr)
 {
-	//Threads_SendSignal( Proc_GetCurThread()->TID, SIGSEGV );
 	Warning("Thread #%i committed a segfault at address %p", Proc_GetCurThread()->TID, Addr);
-	Threads_Exit( 0, -1 );
+	Threads_Fault( 1 );
+	//Threads_Exit( 0, -1 );
 }
 
 // === EXPORTS ===
diff --git a/Modules/Display/VESA/main.c b/Modules/Display/VESA/main.c
index e625c577..c2217e4c 100644
--- a/Modules/Display/VESA/main.c
+++ b/Modules/Display/VESA/main.c
@@ -68,7 +68,7 @@ int Vesa_Install(char **Arguments)
 	// Call Interrupt
 	VM8086_Int(gpVesa_BiosState, 0x10);
 	if(gpVesa_BiosState->AX != 0x004F) {
-		Log_Warning("VESA", "Vesa_Install - VESA/VBE Unsupported (AX = 0x%x)\n", gpVesa_BiosState->AX);
+		Log_Warning("VESA", "Vesa_Install - VESA/VBE Unsupported (AX = 0x%x)", gpVesa_BiosState->AX);
 		return MODULE_ERR_NOTNEEDED;
 	}
 	
@@ -211,7 +211,8 @@ Uint64 Vesa_Write(tVFS_Node *Node, Uint64 Offset, Uint64 Length, void *Buffer)
 		{
 		tVT_Char	*chars = Buffer;
 		 int	pitch = gVesa_Modes[giVesaCurrentMode].width;
-		 int	widthInChars;
+		 int	widthInChars = gVesa_Modes[giVesaCurrentMode].width/giVT_CharWidth;
+		 int	heightInChars = gVesa_Modes[giVesaCurrentMode].height/giVT_CharHeight;
 		 int	x, y;
 		Uint32	*dest = (void*)gpVesa_Framebuffer;
 		 int	i;
@@ -220,7 +221,6 @@ Uint64 Vesa_Write(tVFS_Node *Node, Uint64 Offset, Uint64 Length, void *Buffer)
 		Offset /= sizeof(tVT_Char);
 		
 		LOG("gVesa_Modes[%i].width = %i", giVesaCurrentMode, gVesa_Modes[giVesaCurrentMode].width);
-		widthInChars = gVesa_Modes[giVesaCurrentMode].width/giVT_CharWidth;
 		x = Offset % widthInChars;
 		y = Offset / widthInChars;
 		LOG("(x,y) = (%i,%i) = [%i,%i]", x, y, x * giVT_CharWidth, y * giVT_CharHeight * pitch);
@@ -232,11 +232,16 @@ Uint64 Vesa_Write(tVFS_Node *Node, Uint64 Offset, Uint64 Length, void *Buffer)
 			);
 		
 		// Sanity Check
-		if(y > gVesa_Modes[giVesaCurrentMode].height/giVT_CharHeight) {
+		if(y > heightInChars) {
 			LEAVE('i', 0);
 			return 0;
 		}
 		
+		if( Offset + Length > heightInChars*widthInChars ) {
+			Length = heightInChars*widthInChars - Offset;
+			Log_Notice("VESA", "Clipping write size to %i characters", (int)Length);
+		}
+		
 		dest += y * giVT_CharHeight * pitch;
 		dest += x * giVT_CharWidth;
 		
@@ -251,7 +256,6 @@ Uint64 Vesa_Write(tVFS_Node *Node, Uint64 Offset, Uint64 Length, void *Buffer)
 				VT_Colour12to24(chars->FGCol)
 				);
 			
-			
 			chars ++;
 			x ++;
 			if( x >= widthInChars ) {
@@ -301,6 +305,7 @@ Uint64 Vesa_Write(tVFS_Node *Node, Uint64 Offset, Uint64 Length, void *Buffer)
 int Vesa_Ioctl(tVFS_Node *Node, int ID, void *Data)
 {
 	 int	ret;
+	//Log_Debug("VESA", "Vesa_Ioctl: (Node=%p, ID=%i, Data=%p)", Node, ID, Data);
 	switch(ID)
 	{
 	case DRV_IOCTL_TYPE:	return DRV_TYPE_VIDEO;
@@ -324,6 +329,9 @@ int Vesa_Ioctl(tVFS_Node *Node, int ID, void *Data)
 		}
 		return ret;
 	
+	case VIDEO_IOCTL_SETCURSOR:	// Set cursor position
+		return 0;
+	
 	case VIDEO_IOCTL_REQLFB:	// Request Linear Framebuffer
 		return 0;
 	}
diff --git a/Usermode/Libraries/libacess.so_src/core.asm b/Usermode/Libraries/libacess.so_src/core.asm
index ef5b1233..e097d8c5 100644
--- a/Usermode/Libraries/libacess.so_src/core.asm
+++ b/Usermode/Libraries/libacess.so_src/core.asm
@@ -18,7 +18,6 @@ SoMain:
 SYSCALL1	_exit, SYS_EXIT
 SYSCALL2	clone, SYS_CLONE
 SYSCALL2	kill, SYS_KILL
-SYSCALL2	signal, SYS_SIGNAL
 SYSCALL0	yield, SYS_YIELD
 SYSCALL0	sleep, SYS_SLEEP
 SYSCALL1	wait, SYS_WAIT
@@ -44,5 +43,6 @@ SYSCALL3	SysSpawn, SYS_SPAWN
 SYSCALL3	execve, SYS_EXECVE
 SYSCALL2	SysLoadBin, SYS_LOADBIN
 
+SYSCALL1	_SysSetFaultHandler, SYS_SETFAULTHANDLER
 
 SYSCALL6	_SysDebug, 0x100
diff --git a/Usermode/Libraries/libc.so_src/stub.c b/Usermode/Libraries/libc.so_src/stub.c
index 9f629ba4..55f4ca66 100644
--- a/Usermode/Libraries/libc.so_src/stub.c
+++ b/Usermode/Libraries/libc.so_src/stub.c
@@ -3,6 +3,8 @@
  */
 #include "stdio_int.h"
 #include "lib.h"
+#include <stdio.h>
+#include <sys/sys.h>
 
 #define USE_CPUID	0
 
@@ -10,6 +12,7 @@
 #if USE_CPUID
 static void	cpuid(uint32_t Num, uint32_t *EAX, uint32_t *EBX, uint32_t *EDX, uint32_t *ECX);
 #endif
+void	ErrorHandler(int Fault);
 
 // === GLOBALS ===
 extern char **_envp;
@@ -53,9 +56,15 @@ int SoMain(unsigned int BaseAddress, int argc, char **argv, char **envp)
 	}
 	#endif
 	
+	_SysSetFaultHandler(ErrorHandler);
+	
 	return 1;
 }
 
+void ErrorHandler(int Fault)
+{
+	fprintf(stderr, "Fault = %i\n", Fault);
+}
 
 #if USE_CPUID
 /**
diff --git a/Usermode/include/sys/sys.h b/Usermode/include/sys/sys.h
index 7ddf5832..105d5737 100644
--- a/Usermode/include/sys/sys.h
+++ b/Usermode/include/sys/sys.h
@@ -36,3 +36,5 @@ extern int	getpid();	// Get Process ID
 extern int	sendmsg(int dest, unsigned int *Data);
 extern int	pollmsg(int *src, unsigned int *Data);
 extern int	getmsg(int *src, unsigned int *Data);
+
+extern int	_SysSetFaultHandler(void (*Handler)(int));
-- 
2.20.1