LAB 4 IS DONE.

lab/lib/pgfault.c

@@ -0,0 +1,40 @@
+// User-level page fault handler support.
+// Rather than register the C page fault handler directly with the
+// kernel as the page fault handler, we register the assembly language
+// wrapper in pfentry.S, which in turns calls the registered C
+// function.
+
+#include <inc/lib.h>
+
+
+// Assembly language pgfault entrypoint defined in lib/pfentry.S.
+extern void _pgfault_upcall(void);
+
+// Pointer to currently installed C-language pgfault handler.
+void (*_pgfault_handler)(struct UTrapframe *utf);
+
+//
+// Set the page fault handler function.
+// If there isn't one yet, _pgfault_handler will be 0.
+// The first time we register a handler, we need to
+// allocate an exception stack (one page of memory with its top
+// at UXSTACKTOP), and tell the kernel to call the assembly-language
+// _pgfault_upcall routine when a page fault occurs.
+//
+void
+set_pgfault_handler(void (*handler)(struct UTrapframe *utf))
+{
+	int r;
+
+	if (_pgfault_handler == 0) {
+		// First time through!
+		// LAB 4: Your code here.
+
+		sys_page_alloc(sys_getenvid(), (void *) (UXSTACKTOP - PGSIZE), PTE_SYSCALL);
+		sys_env_set_pgfault_upcall(sys_getenvid(), _pgfault_upcall);
+		// panic("set_pgfault_handler not implemented");
+	}
+	
+	// Save handler pointer for assembly to call.
+	_pgfault_handler = handler;
+}