Implement Supplemental Page Table (SPT) per thread along with structure for its entries, w/ G

src/vm/page.c

@@ -1,5 +1,25 @@
 #include "page.h"
 
+/* Hashing function needed for the SPT table. Returns a hash for an entry,
+   based on its upage. */
+unsigned
+page_hash (const struct hash_elem *e, UNUSED void *aux)
+{
+  struct page_entry *page = hash_entry (e, struct page_entry, elem);
+  return hash_ptr(page->upage);
+}
+
+/* Comparator function for the SPT table. Compares two entries based on their
+   upages. */
+bool
+page_less (const struct hash_elem *a_, const struct hash_elem *b_, UNUSED void *aux)
+{
+  const struct page_entry *a = hash_entry (a_, struct page_entry, elem);
+  const struct page_entry *b = hash_entry (b_, struct page_entry, elem);
+  return a->upage < b->upage;
+}
+
+
 /* Updates the 'owner' thread's page table entry for virtual address 'upage'
    to have a present bit of 0 and stores the specified swap slot value in the
    entry for later retrieval from disk. */
@@ -16,5 +36,4 @@ size_t
 page_get_swap (struct thread *owner, void *upage)
 {
 
-}
-
+}