x86-64: handle stack fault for non-canonical address access

* With the amd64 architecture, the stack fault exception got a new
  meaning: it is raised when an instruction tries to access a
  non-canonical address, and the stack is referenced in the
  instruction (e.g. by its addressing mode).
  So unlike on x86, this is not a fatal exception and shouldn't
  trigger a KDL -- instead, it is to be treated like a general
  protection fault, terminating the team which caused it.

* Fixes #13744

src/system/kernel/arch/x86/64/descriptors.cpp

@@ -329,6 +329,15 @@ x86_64_general_protection_fault(iframe* frame)
 }
 
 
+static void
+x86_64_stack_fault_exception(iframe* frame)
+{
+	// Non-canonical address accesses which reference the stack cause a stack
+	// fault exception instead of GPF. However, we can treat it like a GPF.
+	x86_64_general_protection_fault(frame);
+}
+
+
 // #pragma mark -
 
 
@@ -381,7 +390,7 @@ x86_descriptors_init(kernel_args* args)
 	table[9]  = x86_fatal_exception;		// Coprocessor Segment Overrun
 	table[10] = x86_fatal_exception;		// Invalid TSS Exception (#TS)
 	table[11] = x86_fatal_exception;		// Segment Not Present (#NP)
-	table[12] = x86_fatal_exception;		// Stack Fault Exception (#SS)
+	table[12] = x86_64_stack_fault_exception;    // Stack Fault Exception (#SS)
 	table[13] = x86_64_general_protection_fault; // General Protection Exception (#GP)
 	table[14] = x86_page_fault_exception;	// Page-Fault Exception (#PF)
 	table[16] = x86_unexpected_exception;	// x87 FPU Floating-Point Error (#MF)

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

@@ -139,6 +139,13 @@ x86_unexpected_exception(iframe* frame)
 			signalAddress = frame->ip;
 			break;
 
+		case 12: 	// Stack Fault (#SS)
+			type = B_STACK_FAULT;
+			signalNumber = SIGBUS;
+			signalCode = BUS_ADRERR;
+			signalAddress = frame->ip;
+			break;
+
 		case 13: 	// General Protection Exception (#GP)
 			type = B_GENERAL_PROTECTION_FAULT;
 			signalNumber = SIGILL;