implement page table and use it for lazy loading of segments

1 files changed, 12 insertions, 23 deletions

diff --git a/userprog/process.c b/userprog/process.c
index c13c051..15883d9 100644
--- a/userprog/process.c
+++ b/userprog/process.c
@@ -18,6 +18,7 @@
 #include "threads/synch.h"
 #include "threads/thread.h"
 #include "threads/vaddr.h"
+#include "vm/page.h"
 
 /* data structure to communicate with the thread initializing a new process */
 struct start_aux_data {
@@ -128,6 +129,8 @@ start_process (void *aux)
   process->parent_tid = aux_data->parent_thread->tid;
   thread->process = process;
 
+  page_table_init (&thread->page_table);
+
   /* Initialize interrupt frame and load executable. */
   memset (&if_, 0, sizeof if_);
   if_.gs = if_.fs = if_.es = if_.ds = if_.ss = SEL_UDSEG;
@@ -251,6 +254,8 @@ process_exit (void)
     pagedir_destroy (pd);
   }
 
+  page_table_free (&thread->page_table);
+
   /* Destroy the process structure if the parent is not alive
    * any more. Atomic test and set would be sufficient here.
    */
@@ -478,8 +483,6 @@ load (const char *args, void (**eip) (void), void **esp)
 
 /* load() helpers. */
 
-static bool install_page (void *upage, void *kpage, bool writable);
-
 /* Checks whether PHDR describes a valid, loadable segment in
    FILE and returns true if so, false otherwise. */
 static bool
@@ -556,29 +559,15 @@ load_segment (struct file *file, off_t ofs, uint8_t *upage,
     size_t page_read_bytes = read_bytes < PGSIZE ? read_bytes : PGSIZE;
     size_t page_zero_bytes = PGSIZE - page_read_bytes;
 
-    /* Get a page of memory. */
-    uint8_t *kpage = palloc_get_page (PAL_USER);
-    if (kpage == NULL)
-      return false;
-
-    /* Load this page. */
-    if (file_read (file, kpage, page_read_bytes) != (int) page_read_bytes)
-    {
-      palloc_free_page (kpage);
+    /* add segment to page table for on demand loading */
+    if (!page_table_insert_segment (file, ofs, upage, page_read_bytes,
+          page_zero_bytes, writable))
       return false;
-    }
-    memset (kpage + page_read_bytes, 0, page_zero_bytes);
-
-    /* Add the page to the process's address space. */
-    if (!install_page (upage, kpage, writable))
-    {
-      palloc_free_page (kpage);
-      return false;
-    }
 
     /* Advance. */
     read_bytes -= page_read_bytes;
     zero_bytes -= page_zero_bytes;
+    ofs += page_read_bytes;
     upage += PGSIZE;
   }
   return true;
@@ -602,7 +591,7 @@ setup_stack (uint32_t **esp, const char *args)
   if (kpage == NULL)
       return false;
 
-  if (! install_page (((uint8_t *) PHYS_BASE) - PGSIZE, kpage, true)) {
+  if (! process_install_page (((uint8_t *) PHYS_BASE) - PGSIZE, kpage, true)) {
       palloc_free_page (kpage);
       return false;
   }
@@ -706,8 +695,8 @@ setup_stack (uint32_t **esp, const char *args)
    with palloc_get_page().
    Returns true on success, false if UPAGE is already mapped or
    if memory allocation fails. */
-static bool
-install_page (void *upage, void *kpage, bool writable)
+bool
+process_install_page (void *upage, void *kpage, bool writable)
 {
   struct thread *t = thread_current ();