1 files changed, 53 insertions, 0 deletions
diff --git a/kernel/vm/pagefault.c b/kernel/vm/pagefault.c
new file mode 100644
index 0000000..11868e5
--- /dev/null
+++ b/kernel/vm/pagefault.c
@@ -0,0 +1,53 @@
+#include "vm/pagefault.h"
+#include "errno.h"
+#include "globals.h"
+#include "mm/mm.h"
+#include "mm/mman.h"
+#include "mm/mobj.h"
+#include "mm/pframe.h"
+#include "mm/tlb.h"
+#include "types.h"
+#include "util/debug.h"
+
+/*
+ * Respond to a user mode pagefault by setting up the desired page.
+ *
+ *  vaddr - The virtual address that the user pagefaulted on
+ *  cause - A combination of FAULT_ flags indicating the type of operation that
+ *  caused the fault (see pagefault.h)
+ *
+ * Implementation details:
+ *  1) Find the vmarea that contains vaddr, if it exists.
+ *  2) Check the vmarea's protections (see the vmarea_t struct) against the 'cause' of
+ *     the pagefault. For example, error out if the fault has cause write and we don't
+ *     have write permission in the area. Keep in mind:
+ *     a) You can assume that FAULT_USER is always specified.
+ *     b) If neither FAULT_WRITE nor FAULT_EXEC is specified, you may assume the
+ *     fault was due to an attempted read.
+ *  3) Obtain the corresponding pframe from the vmarea's mobj. Be careful about
+ *     locking and error checking!
+ *  4) Finally, set up a call to pt_map to insert a new mapping into the
+ *     appropriate pagetable:
+ *     a) Use pt_virt_to_phys() to obtain the physical address of the actual
+ *        data.
+ *     b) You should not assume that vaddr is page-aligned, but you should
+ *        provide a page-aligned address to the mapping.
+ *     c) For pdflags, use PT_PRESENT | PT_WRITE | PT_USER.
+ *     d) For ptflags, start with PT_PRESENT | PT_USER. Also supply PT_WRITE if
+ *        the user can and wants to write to the page.
+ *  5) Flush the TLB.
+ *
+ * Tips:
+ * 1) This gets called by _pt_fault_handler() in mm/pagetable.c, which
+ *    importantly checks that the fault did not occur in kernel mode. Think
+ *    about why a kernel mode page fault would be bad in Weenix. Explore
+ *    _pt_fault_handler() to get a sense of what's going on.
+ * 2) If you run into any errors, you should segfault by calling
+ *    do_exit(EFAULT).
+ */
+void handle_pagefault(uintptr_t vaddr, uintptr_t cause)
+{
+    dbg(DBG_VM, "vaddr = 0x%p (0x%p), cause = %lu\n", (void *)vaddr,
+        PAGE_ALIGN_DOWN(vaddr), cause);
+    NOT_YET_IMPLEMENTED("VM: ***none***");
+}