From 14fc96febf3658d3e00ac3ebe50f45a76930c8cf Mon Sep 17 00:00:00 2001
From: sBubshait <s.bobshit@gmail.com>
Date: Thu, 28 Nov 2024 17:54:15 +0000
Subject: [PATCH] Implement Supplemental Page Table (SPT) per thread along with
 structure for its entries, w/ G

---
 src/threads/thread.c |  4 +++-
 src/threads/thread.h |  2 ++
 src/vm/page.c        | 23 +++++++++++++++++++++--
 src/vm/page.h        | 23 +++++++++++++++++++++++
 4 files changed, 49 insertions(+), 3 deletions(-)

diff --git a/src/threads/thread.c b/src/threads/thread.c
index 91a12b5..c2944cc 100644
--- a/src/threads/thread.c
+++ b/src/threads/thread.c
@@ -15,6 +15,7 @@
 #include "threads/switch.h"
 #include "threads/synch.h"
 #include "threads/vaddr.h"
+#include "vm/page.h"
 #ifdef USERPROG
 #include "userprog/process.h"
 #include "userprog/syscall.h"
@@ -264,7 +265,8 @@ thread_create (const char *name, int priority,
 
   if (!hash_init (&t->open_files, fd_hash, fd_less, NULL)
       || !hash_init (&t->child_results, process_result_hash,
-                     process_result_less, t))
+                     process_result_less, t)
+      || !hash_init (&t->pages, page_hash, page_less, NULL))
     {
       palloc_free_page (t);
       free (t->result);
diff --git a/src/threads/thread.h b/src/threads/thread.h
index 4a88577..bdfad35 100644
--- a/src/threads/thread.h
+++ b/src/threads/thread.h
@@ -135,6 +135,8 @@ struct thread
     /* Shared between thread.c and synch.c. */
     struct list_elem elem;              /* List element. */
 
+    struct hash pages;                  /* Table of open user pages. */
+
 #ifdef USERPROG
     /* Owned by userprog/process.c. */
     uint32_t *pagedir;                  /* Page directory. */
diff --git a/src/vm/page.c b/src/vm/page.c
index 8ebc71c..9ed026f 100644
--- a/src/vm/page.c
+++ b/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)
 {
 
-}
-
+}
\ No newline at end of file
diff --git a/src/vm/page.h b/src/vm/page.h
index 7259ca9..81a80ba 100644
--- a/src/vm/page.h
+++ b/src/vm/page.h
@@ -2,6 +2,29 @@
 #define VM_PAGE_H
 
 #include "threads/thread.h"
+#include "filesys/off_t.h"
+
+enum page_type {
+  PAGE_EXECUTABLE,
+  PAGE_EMPTY
+};
+
+struct page_entry {
+  enum page_type type; /* Type of Data that should go into the page */
+  void *upage;         /* Start Address of the User Page (Key of hash table). */
+
+  /* File Data */
+  struct file *file;   /* Pointer to the file for executables. */
+  off_t offset;        /* Offset of the page content within the file. */
+  uint32_t read_bytes; /* Number of bytes to read within the page. */
+  uint32_t zero_bytes; /* Number of bytes to zero within the page. */
+  bool writable;       /* Flag for whether this page is writable or not. */
+
+  struct hash_elem elem; /* An elem for the hash table. */
+};
+
+unsigned page_hash (const struct hash_elem *e, void *aux);
+bool page_less (const struct hash_elem *a_, const struct hash_elem *b_, void *aux);
 
 void page_set_swap (struct thread *, void *, size_t);
 size_t page_get_swap (struct thread *, void *);